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UROLOGY BOARD REVIEW MANUAL

Urology Volume 10, Part 2 1

PUBLISHING STAFFPRESIDENT, GROUP PUBLISHER

Bruce M. White

EDITORIAL DIRECTORDebra Dreger

SENIOR EDITORBecky Krumm, ELS

ASSISTANT EDITORJennifer M. Vander Bush

EDITORIAL ASSISTANT Nora H. Landon

EXECUTIVE VICE PRESIDENTBarbara T. White, MBA

EXECUTIVE DIRECTOR OF OPERATIONS

Jean M. Gaul

PRODUCTION DIRECTORSuzanne S. Banish

PRODUCTION ASSOCIATESTish Berchtold KlusMary Beth Cunney

PRODUCTION ASSISTANT Stacey Caiazzo

ADVERTISING/PROJECT MANAGERPatricia Payne Castle

MARKETING MANAGERDeborah D. Chavis

Copyright 2002, Turner White Communications, Inc., 125 Strafford Avenue, Suite 220, Wayne, PA 19087-3391, www.turner-white.com. Allrights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means,mechanical, electronic, photocopying, recording, or otherwise, without the prior written permission of Turner White Communications, Inc.The editors are solely responsible for selecting content. Although the editors take great care to ensure accuracy, Turner WhiteCommunications, Inc., will not be liable for any errors of omission or inaccuracies in this publication. Opinions expressed are those of theauthors and do not necessarily reflect those of Turner White Communications, Inc.

NOTE FROM THE PUBLISHER:This publication has been developed withoutinvolvement of or review by the AmericanBoard of Urology.

Laparoscopy in Urology: Physiologic ConsiderationsSeries Editor: Bernard Fallon, MDProfessor, Department of Urology, University of Iowa, Iowa City, IA

Contributors: Vincent G. Bird, MDFellow, Endourology and Laparoscopic Surgery, Department ofUrology, University of Iowa, Iowa City, IA

Howard N. Winfield, MDProfessor, Director of Endourology and Minimally Invasive Surgery,Department of Urology, University of Iowa, Iowa City, IA

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Equipment Used for Insufflation . . . . . . . . . . . . . . . 3

Physiologic Changes During Laparoscopy. . . . . . . . . 5

Anesthetic Considerations. . . . . . . . . . . . . . . . . . . . 10

Intraoperative Complications of Laparoscopy. . . . . 13

Postoperative Considerations . . . . . . . . . . . . . . . . . 16

Case Discussions. . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Table of Contents

Cover Illustration by Paul Schiffmacher

2 Hospital Physician Board Review Manual

INTRODUCTION

The application of modern laparoscopic principlesto urologic surgery has resulted in significant patientbenefits, including decreased postoperative pain,reduced length of hospitalization, and shortened recov-ery times. The evolving technologies that accompanylaparoscopy and its application have also afforded thelaparoscopic surgeon excellent visualization, magnifica-tion, and surgical instrumentation that allow the per-formance of increasingly complex surgical procedureswith a degree of safety and efficacy equal to that of sim-ilar open surgical interventions.

Laparoscopic surgery is performed in a differentenvironment from that of open surgery. This uniqueenvironment results in differences in which the anes-thetized patient responds to the physiologic stress ofsurgery. Urologists performing transurethral surgeryare already familiar with the concept of performingprocedures in a surgical environment different fromthat of open surgery. As is the case with transurethralsurgery, both the laparoscopic surgeon and anesthesi-ologist must have a complete understanding of the dif-ferences between open and laparoscopic surgery inorder to ensure that all patients undergoing laparo-scopic interventions will be able to tolerate the proce-dure, and that patients are not being exposed to unduerisk that may result from factors specifically related tothe nature of laparoscopic surgery.

The laparoscopic technique is predicated on themechanical creation of pneumoperitoneum, which hasimportant physiologic implications. A proper and thor-ough understanding of the physiology of laparoscopicanesthesia and surgery is becoming even more relevantin that laparoscopic procedures are now not only offeredto young, healthy adult patients. Many pediatric andelderly patients with a variety of medical conditions maynow also benefit from laparoscopic procedures. Thisreview focuses on the physiologic sequelae of the pneu-moperitoneum induced in laparoscopy. Studies relatingto laparoscopy alluded to in this article were performed

with CO2 insufflation of the peritoneal cavity unless it isspecifically stated that the conditions are otherwise.

HISTORY OF LAPAROSCOPY

The use of minimally invasive techniques for the diag-nosis and treatment of a variety of medical conditionsextends back to ancient times. Archaeological evidencereveals that the Greeks and Romans inserted instrumentsinto the human body in a variety of manners in attemptsto visualize internal anatomy and pathology.1 The Arabianphysician Albukasim (936–1013) was the first known tohave used illumination (light from a candle reflectedfrom a mirror) to view the interior of the vagina.1 How-ever, the evolution of modern endoscopy/laparoscopytruly began approximately 200 years ago when Bozziniconstructed his “Lichtleiter,” which was the first crude cys-toscope.2 The quality of endoscopy slowly progressed asimproved light sources became available. Bladder endos-copy was readily embraced because the bladder could eas-ily be filled with fluid that also acted as a coolant for thedistally located light source. Soon after its invention, theprinciples of the electric light bulb were quickly adaptedto endoscopy by Maximilian Nitze, thus further improv-ing the quality of endoscopy.1

Peritoneal endoscopy would prove more formidablethan cystoscopy. In 1902, Ott performed “ventroscopy”by passing a speculum through a small colpotomy, illu-minating the abdominal cavity with incandescent lightreflected from a head mirror.3 However this viewing wasquite limited as the abdomen was not expanded. A fewyears later, both Kelling4 in Germany and Jacobaeus5 inSweden described endoscopic abdominal inspectionwith the use of pneumoperitoneum. The use of insuffla-tion greatly enhanced endoscopic surveillance of theabdominal cavity. The safety of these procedures wasthen improved by the use of proximal light sources,which prevented the dangers of burns and other elec-trical faults associated with intraabdominal light sources.

During most of the twentieth century, mainly inEurope, laparoscopy was widely used as a diagnostic tool.Many European endoscopists continued to make im-provements upon the procedure. Notably, in Germany,

UROLOGY BOARD REVIEW MANUAL

Laparoscopy in Urology: Physiologic Considerations

Vincent G. Bird, MD, and Howard N. Winfield, MD

Frangenheim6 published numerous articles describingvarious technical points of laparoscopy. Moreover, he wasalso among the first individuals to describe in detail poten-tial complications of laparoscopy, including emphysema,air embolism, and cardiopulmonary problems. He alsoemphasized the need for performance of laparoscopyunder general anesthesia and the importance of insuf-flating the abdomen slowly. Frangenheim’s contributionshelped emphasize that attention and proper manage-ment of the physiologic effects of laparoscopy performedunder pneumoperitoneum were as important as employ-ing proper technical skills with the proper equipment.The combination of advanced equipment and an under-standing of the physiology of laparoscopy has allowedlaparoscopic surgical technique to ultimately be em-ployed for a multitude of complex therapeutic surgicalprocedures that are performed today in a variety of surgi-cal specialties.

VARIANTS OF LAPAROSCOPY

Urologic laparoscopic procedures are performed ina variety of fashions. The term laparoscopy is of Greekderivation (lapara, flank). Endoscopy of the insufflatedperitoneal cavity is more correctly termed peritoneoscopy.This procedure became generally termed laparoscopyeven though this designation is not entirely accurate.Many urologic laparoscopic procedures are performedin this transperitoneal fashion. However, nephrectomycan be accomplished through creation of a retroperi-toneal working space, a technique properly termedretroperitoneoscopy. For the sake of clarity, in this reviewretroperitoneoscopy refers to endoscopy of the retroperi-toneum cephalad to the pelvic brim.7 Pelvic lymphad-enectomy and various procedures that involve the blad-der can also be performed in an extraperitoneal(referring to the extraperitoneal space below the pelvicbrim) fashion. In this manual, the term laparoscopy isused in a general sense to include all laparoscopic pro-cedures, including those noted above. Occasional spe-cific mention will be made when the unique nature ofone of these approaches has the potential to create dif-ferent physiologic manifestations.

EQUIPMENT USED FOR INSUFFLATION

When laparoscopy was first performed for simplediagnostic purposes, relatively simple instrumentationsufficed. However, with the advent of using laparoscopyto perform full-scale therapeutic procedures that re-quire considerable operative time, a wide array of ad-vanced multipurpose equipment and instrumentation

has been developed. For the performance of successfullaparoscopy, equipment and instrumentation satisfyingthe following categories is required:

• Insufflation system • Camera/video system • Proper instrumentation (eg, trocar/sheaths, as-

piration irrigation system, laparoscopic shears,graspers)

It is essential that the laparoscopic surgeon hasfamiliarity with all needed equipment and ensures itsavailability and proper functioning. The insufflator is afundamental and vital component for the routine per-formance of laparoscopic surgery. A thorough under-standing of this device is imperative for recognition ofthe physiologic sequela and potential complications ofinsufflation. Three components are necessary for insuf-flation8: A device through which to insufflate (either aneedle or Hasson-type cannula), an insufflator, and aninsufflating gas medium.

DEVICES THROUGH WHICH TO INSUFFLATE

Most commonly, initial peritoneal insufflation is car-ried out through use of a Veress needle, a spring-loadeddevice specifically designed for laparoscopy that allows forrelatively atraumatic passage into the peritoneal cavity.However, if there is a history of prior intra-abdominalsurgery with the likelihood of intra-abdominal adhesions,it is safest to perform a “mini-laparotomy” with place-ment, under direct vision, of a blunt-tipped Hasson-typecannula through which insufflation can be carried out.

In addition to transperitoneal laparoscopic proce-dures, retroperitoneal procedures are also common.Extraperitoneal procedures have also been described.These types of procedures usually require first a smallincision with creation of a “working space” by means ofa balloon dilating device. After expansion, a Hasson-type trocar may be placed, through which insufflation iscarried out.

THE INSUFFLATOR

The insufflator is a complex electronic machine thatoperates by a valve mechanism that controls the flow ofgas from a tank or other gas source into the peritoneal orother body cavity in which surgery is being performed.Regardless of manufacturer, all of these devices operate ina similar fashion and have standard functions that can beadjusted and monitored. Most machines display 3 essen-tial items: (1) gas flow rate, (2) intraperitoneal pressure,and (3) volume of gas utilized during the procedure.

Early devices operated only at a “low flow” of gas, butas laparoscopy has progressed from simple diagnostic


L a p a r o s c o p y i n U r o l o g y : P h y s i o l o g i c C o n s i d e r a t i o n s



procedures to procedures that require multiple ex-changes of instrumentation and specimen retrieval (caus-ing partial or full release of pneumoperitoneum), “high-flow” devices now available allow these procedures to becompleted expeditiously. Low flow commonly refers to gasflow of 1 to 2 L/min, whereas high flow refers to flow of 8 to10 L/min (or higher). Most modern machines can pro-vide flow of up to 15 L/min of gas flow. Upon initiation ofinsufflation, it is judicious to begin filling the workingspace at a low flow rate until one is sure that the properspace is being insufflated and that the patient is tolerat-ing insufflation without complication. Once these issueshave been clarified, insufflation may then be continuedon high flow.

The second important component of the insufflator isthe analog or digital display of the patient’s intraperi-toneal pressure. This component usually includes a fea-ture that allows one to preset a maximal allowable intra-cavitary pressure. Prior to insufflation, the surgeon shouldtest the proper function of the pressure gauge by occlud-ing the gas line (which should cause a high pressure read-ing) and then unoccluding it (which should cause thepressure reading to appropriately drop). The pressuregauge has the very important function of ensuring thatinitial filling takes place at low pressure, that continuedfilling follows a smooth progression up to the preset max-imal pressure, and that unduly high pressures are avoidedduring the performance of surgery. Most modern insuf-flators contain an alarm that will go off when the presetmaximal pressure is exceeded.

The insufflator also records the amount of gas uti-lized. Upon initial insufflation, the average adult in-traperitoneal cavity will require 4 to 6 L of gas to obtaina pressure of 15 mm Hg. Any significant deviation fromthese expected parameters should be appropriatelyaddressed. The total volume of gas utilized during aprocedure is related to procedure duration and theexchange or removal of instruments and specimens.

THE INSUFFLANT

In the pioneering era of laparoscopy, room air wasused for insufflation. However, room air may be conta-minated, may result in prolonged postoperative disten-tion, and is relatively insoluble in blood, thus increasingthe risk of gas embolus. For these reasons the use of airfell out of favor.

CO2 is the most commonly used insufflant for laparo-scopic procedures, for several reasons. The anesthesiol-ogist can readily monitor elimination of this gas. Relativeto other (inert) gases that may be used as an insufflant,CO2 has a high diffusion coefficient.9 The diffusion coef-ficient defines the rate of diffusion for a specific gas at agiven partial pressure and diffusion distance. As such,this coefficient also accounts for the solubility and mole-cular weight of the gas. The diffusion coefficients ofselected gases are shown in Table 1. The degree of solu-bility of CO2 in blood significantly diminishes the risk ofgas embolus. It is believed that rapid absorption of atleast 500 cc of CO2 is required prior to development ofgas embolus.8 Note, however, that the ready absorptionof this gas results in increased arterial CO2 pressure.Thus, it is important that the anesthesiologist adjustsventilation to ensure removal of excess CO2. Anotheradvantage of CO2 is that it does not support combustion,allowing for the safe use of electrocautery and lasers.

Nitrous oxide has been used as an insufflant in shortdiagnostic procedures under local anesthesia. UnlikeCO2, nitrous oxide does not irritate the diaphragm orthe peritoneal membrane. However, nitrous oxide sup-ports combustion, and as such cannot be safely used ifelectrocautery or lasers are required.8,10 (One shouldalso consider that if the bowel is opened during a lap-aroscopic procedure, combustible gases such as meth-ane may be released).

Inert gases such as helium, argon, xenon, and kryptonmay be suitable for laparoscopy. However, besides beingvery expensive, these gases are not readily absorbed andthus may be more likely to result in embolus.10 There isalso a paucity of data relating to the full extent of possiblephysiologic effects of these gases. For safety purposes, dif-ferent gases often are stored in specifically different typesof tanks with different yokes and attachment devices inorder to prevent unintentional use of the wrong gas.These differences in storage require adaptation of opera-tive equipment that may be cumbersome and impractical.As such, cost (in some instances), routine unavailability,practicality, and lack of large amounts of data as to the fullextent of the effects of these gases contribute to the pro-hibition of their regular use.8,10

Given the selection of gases available, and their rela-tive practicality, risks and benefits, the advantages of CO2

Table 1. Diffusion Coefficients of Select Gases

Gas Diffusion Coefficient*

Carbon dioxide 20.3

Oxygen 1.0

Helium 0.95

Carbon monoxide 0.81

Nitrogen 0.53

*The diffusion coefficient is a relative number based on the diffusioncoefficient of oxygen.

Data from Pearle.9

most clearly outweigh its risks, making it the insufflant ofchoice for the majority of laparoscopic procedures.

GASLESS LAPAROSCOPY

Insufflation with any type of gas under any significantpressure will have some effect upon the patient, more soin those with significant cardiopulmonary disease.Completely gasless laparoscopy eliminates the concernof insufflation and its attendant effects. Banting et al9,11

describe the use of an abdominal lifting device made ofa polyethylene tube—supported extracorporeally by ahook and chain contraption—that suspends the ab-dominal wall. The use of this device allowed a reductionin the amount of intra-abdominal pressure needed foran adequate working space. The device was insertedunder endoscopic vision after having initially created apneumoperitoneum with a pressure of 10 to 12 mm Hg.With this setup, the authors were able to perform laparo-scopic cholecystectomy in 8 patients who had significantcardiopulmonary disease using intra-abdominal pres-sures of only 6 to 8 mm Hg. The authors reported nocomplications specifically related to the use of the ab-dominal lifting device.

Araki et al12 reported use of a similar mechanism com-posed of wire externally attached to a suspensory mech-anism. This setup was used with initial low pressure pneu-moperitoneum until the gall bladder was identified, andwas especially helpful in obese patients. There were nocomplications specifically related to the use of this wire-type device. The authors documented decreased endtidal CO2 pressure (compared to end tidal CO2 pressuresmeasured in laparoscopic procedures performed withCO2 pneumoperitoneum at 15 to 20 mm Hg.) through-out various parts of the procedure.

Other abdominal lift devices have also been de-scribed, including the Laprolift (Origin Medsystems,Menlo Park, CA), which has been used in the perfor-mance of a wide variety of laparoscopic procedures. Intheir use of this device in 58 patients undergoing bothelective and trauma-related procedures, Smith et al13

reported that exposure was equal to that achieved bypneumoperitoneum in 97% of cases. The majority ofthese procedures were completed with the gasless tech-nique. Complications in this group included 2 superfi-cial wound infections and 1 enterotomy. Additionally,several patients experienced abdominal wall discom-fort in the postoperative period.

Fortunately, the majority of patients undergoinglaparoscopy with CO2 at standard insufflation pressures(15 mm Hg) do not experience significant sequelae,and therefore the use of low pressure and gasless lapar-

oscopy is limited. Surgeons who have used a gaslesstechnique have also made it clear that its use is some-what cumbersome, and at times it may not offer suffi-cient exposure of the operative field.10 However, gaslesslaparotomy may be quite beneficial to those patientswith significant medical comorbidity who are not likelyto tolerate typical insufflation pressures.

PHYSIOLOGIC CHANGES DURING LAPAROSCOPY

Laparoscopic surgery shares certain features withopen surgery in terms of how the patient’s body isstressed during the procedure. However, a significantfeature that distinguishes it from open surgery is thelaparoscopic environment—a confined space that isgenerally insufflated with CO2 gas under pressure. Theeffects of this condition are transmitted to the patients’body in a variety of ways.

Study of the physiologic effects of abdominal insuf-flation to date has been limited. However, the physio-logic state created by pneumoperitoneum sharesmany features with what trauma surgeons have termedthe abdominal compartment syndrome,14 and thus acomparison to this condition may be worthwhile. Ab-dominal compartment syndrome is commonly causedby entities such as intra-abdominal hemorrhage, mas-sive abdominal distention, bowel edema, ascites, andthe use of military antishock trousers. This potentiallyfatal syndrome is commonly associated with intra-abdominal pressures greater than 20 mm Hg, peak air-way pressures greater than 40 mm Hg, decreasedurine output (< 0.5 mL/kg body weight per hour),and significant cardiopulmonary deterioration.15 It ischaracterized by notable cardiovascular, pulmonary,and renal effects that result from increased intra-abdominal pressure. The increased intra-abdominalpressure results in a decrease in microcirculation,which in turn causes impairment of organ func-tion.16,17 although this syndrome is related to otherpathologic conditions, an understanding of this entityand of CO2 homeostasis has led to a better under-standing of the significant pulmonary, cardiovascular,and renal effects of pneumoperitoneum.

CARBON DIOXIDE HOMEOSTASIS

CO2 is one of the major end products of cellularmetabolism; as such, efficient mechanisms exist for itsremoval from human body tissue prior to its removal as agas from the lungs. The primary mechanism of removalinvolves the carbonic acid–bicarbonate buffer system,



which also assists in the prevention of significant changesin arterial pH.9 The two major components of this systemare CO2 and bicarbonate (HCO3

–). CO2 concentration isregulated by the lungs, and bicarbonate is regulated bythe kidneys. After its production by body metabolism,CO2 is transported from body tissues in two ways. A smallamount of CO2 dissolves in the blood and is carried to thelungs as a gas. The remainder enters erythrocytes, wherea small amount complexes with hemoglobin and a muchlarger amount combines with water to form carbonic acid(H2CO3) in a reaction catalyzed by carbonic anhydrase.Upon formation, carbonic acid then rapidly dissociatesinto hydrogen ions and bicarbonate. These reactions,which are in dynamic equilibrium, are shown here:

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3–

This reaction can be driven in either direction by theremoval or introduction of CO2 or bicarbonate. Forexample, as CO2 is removed by the lungs, the reactionis driven to the left, resulting in a decrease in hydrogenions and an increase in pH.

Owing to its relatively high diffusion coefficient,CO2—whether as a end product of metabolism or as aninsufflant introduced during a laparoscopic procedure—partially dissolves into the peritoneal fluid (in the case oftransperitoneal laparoscopy) and reaches equilibriumwith the body tissues and blood. However, the degree ofabsorption may vary depending on the nature of the pro-cedure being performed. There is evidence that retro-peritoneal and extraperitoneal procedures may be as-sociated with more CO2 absorption as compared withtransperitoneal procedures.18,19 The reasons for this arenot entirely clear, but may be related to the creation ofthe potential space needed to perform retroperitoneo-scopic and extraperitoneoscopic procedures. Creation ofthe working space with manual and balloon dissectionmay result in a cavity surface that is more permeable toCO2 due to disruption of these body tissue surfaces.However, these noted differences in absorption are ofuncertain clinical significance and have not precludedthe use of any of these approaches.

In summary, the well-controlled metabolic integra-tion of CO2 into the metabolism makes this gas quitesuitable as an insufflant for laparoscopy under normalconditions. Upon introduction, the formation of gasembolus is unlikely, and its elimination can readily bemonitored by measurement of end-tidal CO2 pressures.

INTRAOPERATIVE RESPIRATORY CHANGES

The filling of the peritoneal, retroperitoneal, andextraperitoneal spaces with CO2 results in both a dis-turbance in the mechanics of breathing (perhaps less so

in lower abdominal extraperitoneal procedures) andexcessive absorption of CO2.

Insufflation pressures used during laparoscopy canresult in decreased lung compliance. Trendelenburgpositioning also transfers the weight of the viscera to thediaphragm, which is already elevated by increased intra-abdominal pressure (Figure 1).20 These effects result ina loss of functional residual capacity and an increase inventilation-perfusion mismatching, which in turn mayresult in hypoxia. These factors may also significantlycontribute to postoperative atelectasis.

The absorption of CO2 during laparoscopic proce-dures results in increased arterial and alveolar CO2 andacidosis. These increases in CO2 can be easily measuredby blood gas analysis and determination of end tidalCO2 pressure. Studies have shown that hypercarbia dur-ing laparoscopy is related to both the laparoscopicapproach and the length of the procedure, and is alsoassociated with the development of significant subcuta-neous emphysema.18

When CO2 is absorbed, its partial pressure in theblood increases. Laparoscopy performed under gener-al anesthesia results in increased CO2 pressure in theblood of approximately 9 to 10 mm Hg, although in anygiven case it may be higher.21 This excess CO2 must beeliminated. This is commonly done by increasing thepatient’s respiratory minute volume. In certain patientswith restrictive or obstructive pulmonary disease, theamount of increase of respiratory minute volume re-quired for elimination of excess CO2 may not be achiev-able and thus these individuals should not undergo alaparoscopic procedure that specifically involves insuf-flation with CO2.22

Notable differences in lung mechanics between chil-dren and adults exist.23 Owing to differences in the configuration of the thoracic rib cage and a relativelyhigher dependence on the diaphragm for adequateventilation in children, the specific nature of mechani-cal ventilation required for children is determined byusing tidal volume–compliance curves specific to chil-dren along with age- and weight-appropriate ventila-tion parameters. Young children also have smaller lungcapacities and thus require increased minute ventilationfor the elimination of excess CO2. The operative posi-tion of the pediatric patient may also greatly influencelung and chest compliance and the parameters requiredfor adequate ventilation.

INTRAOPERATIVE HEMODYNAMIC EFFECTS

The establishment of pneumoperitoneum results in adirect increase in intra-abdominal pressure. This pres-sure increase causes a reduction in cardiac preload and



an increase in cardiac afterload (Figure 2).20,24 Thedecrease in preload is generally the result of compressionof the inferior vena cava. However, the effect of pneu-moperitoneum on venous return is also largely depen-dent on the patient’s volume status prior to insufflation.25

Thus, preoperative volume loading may minimize theincidence of abrupt cardiovascular changes.

The increase in cardiac afterload is caused by com-pression of the abdominal aorta, an increase in sympa-thetic activity with contraction of the arterioles, andincreased venous resistance.22 CO2 itself enhances sym-pathetic activity and causes peripheral vasoconstriction.In addition, increased intra-abdominal pressure andhypercarbia also result in further myocardial suppres-sion. although a number of investigations have beenperformed regarding the cardiovascular effects of CO2

pneumoperitoneum, it remains difficult to distinguishwhich effects are caused specifically by hypercarbia andwhich are the result of increased abdominal pressure.

The combination of decreased preload and in-creased afterload results in a decreased cardiac out-put. Animal studies have shown that a reduction any-where from 20% to 70% occurs, in comparison topreoperative values. Although the data in humans isincomplete, it appears that in the standard pressurerange at which laparoscopy is generally performed(15–20 mm Hg), any reduced cardiac output is notclinically significant in healthy patients under normalcircumstances.21,22 Table 2 summarizes the cardio-vascular effects of laparoscopy that occur at standardpneumoperitoneal pressures.

Studies in young healthy women placed in theTrendelenburg position have demonstrated that car-diac indices are reduced even when intra-abdominalpressures are 14 mm Hg or less.9 The results of the car-diovascular effects of position are shown in Table 3.

Insufflation pressure, choice of insufflant, and patientposition all influence hemodynamic parameters duringlaparoscopy, although the exact contribution of each isoften difficult to discern. For this reason, it is not alwaysclear how patients with cardiac disease will respond toinsufflation. The reported incidence of cardiac arrhyth-mias during laparoscopy performed under general anes-thesia is in the range of 5% to 27%.26 The most commonarrhythmias are unifocal and multifocal ventricular ectopyand bigeminy.27 It is hypothesized that these arrhythmiasare caused by hypercarbia20 or by vagal activity induced byinsufflation (particularly if insufflation is rapid and resultsin high intra-abdominal pressure).22 Some also considerthe manipulation of pelvic organs to be a cause of vagalactivity.27 Hypercarbia results in depression of myocardialfunction, which can result in bradycardia and hypoten-sion. This may then lead to a sympathetic responsemarked by the release of catecholamines with resultantvasoconstriction, increased inotropic/chronotropic ef-fects, and possibly arrhythmias. Certain anesthetic agentsmay also sensitize the myocardium.20

INTRAOPERATIVE RENAL EFFECTS

The most common renal alteration associated withpneumoperitoneum is oliguria (urine output less than0.5 mL/kg per hour). Vukasin et al28 demonstrated in acontrolled study that these renal effects were not inducedby anesthesia alone, but that increasing pneumoperi-toneal pressures using either nitrogen or CO2 resulted ina further decrease of urine output, which was reversedupon desufflation. Studies involving gasless laparoscopydemonstrate that oliguria is not observed when onlyabdominal lift devices are used. Another study involvingthe use of CO2 versus argon gas demonstrated that thetype of insufflated gas made no difference in the renalsequelae typically seen with increased intra-abdominal



Figure 1. The diaphragm is ele-vated during pneumoperitoneum,restricting lung volume and de-creasing compliance. Reprintedwith permission from Wolf JS,Monk TG. Anesthetic considera-tions. In: Smith AD, Badlani GH,Bagley DH, et al, editors. Smith’stextbook of endourology. St.Louis (MO): Quality Medical Pub;1996:734.

pressure.9,29 In both animal and human studies, a largenumber of authors have noted that oliguria most com-monly occurs in cases of prolonged abdominal insuffla-tion. It has also been demonstrated that it occurs duringboth pneumoperitoneal and pneumoretroperitonealprocedures. Oliguria and anuria occur more often incases of prolonged insufflation in patients with cardiovas-cular and renal dysfunction. However, oliguria reliablyreverses following desufflation.

There are no known reports of pneumoperitoneum-induced renal failure, although transient increases inserum creatinine have been noted. Histologic studies ofkidney tissue after CO2 pneumoperitoneum have notrevealed any pathologic changes,30 but higher than nor-mal N-acetyl-β-D-glucosaminidase (NAG) levels, an indi-cator of proximal tubular cell death, have been noted.The significance of this latter finding is uncertain.

Mechanisms of Pneumoperitoneum-Induced Oliguria

A variety of mechanisms have been suggested as caus-es for pneumoperitoneum-induced oliguria. Seiba et al16

offer a thorough summary of the renal physiology oflaparoscopic surgery and the mechanisms that may beresponsible for oliguria. These mechanisms includerenal parenchymal and vascular compression, decreasedblood flow to the kidney due to decreased cardiac out-put, central venous congestion (increased central venouspressure), hormonal changes, and ureteral obstruction.16

Although it is not entirely clear to what degree these var-ious entities contribute to decreased urine output, itappears that pneumoperitoneum-induced oliguria ismultifactorial in nature.

Renal parenchymal compression. In early studies,Page16,31 noted that renal parenchymal compressionresulted in both renal hypertension and decreased urineoutput. Skinner16,32 later demonstrated this effect to berenin mediated. Others also have associated increasedplasma renin activity with increased intra-abdominal pres-sure. More recently, Razvi et al16,33 demonstrated that renalcompression at 15 mm Hg resulted in a 63% decrease inurine output, a 21% decrease in glomerular filtration rate,and a 26% decrease in effective renal blood flow.

Renal vascular compression. Renal arterial blood flowis stable at intra-abdominal pressures below 10 mm Hg.At intra-abdominal pressures of 20 mm Hg, however, a15% decrease in renal arterial blood flow, a 58% to 69%drop in cortical perfusion, a 64% reduction in glomeru-lar filtration rate, and a 50% decrease in urine outputhave been noted.16,34–36 At typical pneumoperitonealpressures, intra-abdominal pressure is twice that of venacaval pressure.16,35 It also known that changes in venouspressure parallel changes in intra-abdominal pressure.At intra-abdominal pressures greater than 15 mm Hg,changes in urine output parallel decreases in renal veinblood flow.16,29

Decreased cardiac output to the kidney. Decreasedcardiac output directly results in decreased renal perfu-sion and is a well known prerenal cause of oliguria.Decreased cardiac output upon an increase in intra-abdominal pressure has been documented. Hypovo-lemia may also lead to further cardiac compromise. Ina study of patients undergoing laparoscopic cholecys-tectomy, urine output was more severely decreased inthose patients with cardiac disease.37



Figure 2. Pneumoperitoneum increasessystemic vascular resistance and reducesvenous return. Dramatic decreases incardiac output can occur. Reprinted withpermission from Wolf JS, Monk TG.Anesthetic considerations. In: Smith AD,Badlani GH, Bagley DH, et al, editors.Smith’s textbook of endourology. St.Louis (MO): Quality Medical Pub; 1996:741.

Central venous compression. Kirsch et al38 demon-strated that at insufflation pressures of 10 mm Hg,inferior vena caval and aortic flow are both significant-ly decreased. This overall decreased arterial flow, com-bined with an increase in venous pressure, also con-tributes to reduced renal plasma flow, glomerularfiltration rate, and reduced urine output.

Hormonal changes. Numerous physiologic stud-ies demonstrate changes in the renin-angiotensin-aldosterone system and in levels of endothelin, antidi-uretic hormone (ADH), and atrial natriuretic factor.16

Animal studies clearly demonstrate an increase in plas-ma renin activity during intra-abdominal insufflation.This does not occur at low pressure, but insufflation at15 mm Hg has resulted in a 4-fold increase.39–42 Thisrenin increase is also associated with redistribution ofrenal blood flow from the outer renal cortex to thejuxtamedullary zone. As the majority of glomeruli re-side in the cortex, this redistribution results in de-creased filtration. Studies involving the administrationof angiotensin-converting enzyme inhibitors duringlaparoscopy do not demonstrate prevention of olig-uria with use of these agents.28

Changes in serum electrolyte levels during lapa-roscopy may result from increased serum aldosterone lev-els.16 The net result of increased serum aldosterone isdecreased serum potassium and increased serum sodi-um. Bloomfield et al42 demonstrated in animal studiesthat intravascular volume expansion could increase urineoutput and decrease plasma renin and aldosterone levels.

Animal studies have revealed a 55% increase in renalvein endothelin during pneumoperitoneum. This agent

is a potent vasoconstrictor and may contribute to olig-uria. Studies involving the use of endothelin receptorantagonists under pneumoperitoneum resulted in asmaller drop in glomerular filtration rate compared tocontrols.43

CO2 insufflation may increase plasma levels of ADH.This has been demonstrated in animal and human stud-ies.44,45 Studies showing no increase in plasma ADH at15 mm Hg insufflation pressures also exist, however.28

Decreased cardiac output, increased levels of catechol-amines, and increased renin production all may con-tribute to elevated levels of ADH during pneumoperi-toneum. It is hypothesized that the delay in diuresis afterdesufflation may be explained by the ADH release asso-ciated with increased intra-abdominal pressure16; howev-er, no specific data exists to support this theory.

Elevated adrenocorticotropic hormone and cortisollevels have been associated with laparoscopic proce-dures.46 Some studies suggest that levels of atrial natri-uretic factor levels may increase during CO2 pneu-moperitoneum.16 Because the information availableregarding the activity of these hormones during pneu-moperitoneum is limited, however, no further conclu-sions can be drawn as to the significance of these find-ings. A summary of some of the observed hormonalphysiologic changes occurring during pneumoperi-toneum is listed in Table 4.

Ureteral compression. Studies of cases involving in-creased intra-abdominal pressure due to intra-abdominalhemorrhage demonstrate that the placement of ureteralcatheters does not prevent oliguria.16,47,48 Intravenouspyelograms of individuals undergoing intra-abdominalinsufflation do not demonstrate ureteral obstruction.38



Table 2. Cardiovascular Effects of CO2

Pneumoperitoneum at 10 to 20 mm Hg of Pressure

Parameter Effect of Pneumoperitoneum

Heart rate ↑Mean arterial ↑

pressure

Systemic vascular ↑↑resistance

Venous return ↓↓Cardiac output no change or ↓

↑ = moderate increase, ↓ = moderate decrease, ↑↑ = large increase,↓↓ = large decrease.

Adapted with permission from Pearle MS. Physiologic effects of pneu-moperitoneum. In: Smith AD, Badlani GH, Bagley DH, et al, editors.Smith’s textbook of endourology. St. Louis (MO): Quality Medical Pub;1996:756.

Table 3. Direct Hemodynamic Effects of PatientPosition Compared with Baseline Supine Position

Patient Position

Hemodynamic Parameter Head Up Head Down

Heart rate ↑ ↓Mean arterial pressure ↓ ↑Systemic vascular resistance ↑ ↓Cardiac output ↓ ↑

↑ = increase, ↓ = decrease.

Adapted with permission from Pearle MS. Physiologic effects of pneu-moperitoneum. In: Smith AD, Badlani GH, Bagley DH, et al, editors.Smith’s textbook of endourology. St. Louis (MO): Quality Medical Pub;1996:763.

Thus, there is no clear evidence that insufflation-inducedoliguria is attributable to ureteral compression.16

Laparoscopic Living-Donor Nephrectomy

The nature of oliguria related to insufflation is par-ticularly pertinent to cases involving laparoscopic living-donor nephrectomy, in which adequate hydration andrenal perfusion is necessary for optimization of func-tion of the donor kidney prior to division of the renalvasculature. The concern is that the effects of pneu-moperitoneum may result in decreased perfusion,renal ischemia, acute tubular necrosis, delayed graftfunction, and increased allogenicity.49 Studies of laparo-scopic living-donor nephrectomy demonstrate that cre-atinine nadirs in recipients are slightly delayed immedi-ately after surgery as compared with open donornephrectomy. However, graft survival and long-termcreatinine levels in the two groups appear to be equal.50

Fortunately, most living donors are in good health andtolerate intravascular volume expansion well, whichmay alleviate these concerns. Mannitol has been usedfor its abilities to increase glomerular filtration rate andurine output. Endothelin receptor blockers have alsobeen used in an attempt to block the vasoconstrictiveeffects of endothelin.51

ANESTHETIC CONSIDERATIONS

PREOPERATIVE EVALUATION

Though laparoscopic surgery is minimally invasive,many procedures performed by laparoscopic means (eg,nephrectomy) are major procedures. All laparoscopicprocedures also carry the risk of conversion to an openprocedure. As such, all patients being evaluated for theseprocedures should be prepared with the assumption thatconversion to an open procedure may be necessary.

In addition to the laparoscopic surgeon’s criteria forpatient selection, there are anesthetic criteria that mustbe met. One third of deaths that occur during laparo-scopic procedures result from anesthetic complica-tions.52 A complete preoperative history and physicalexamination is required to identify any factors that maybecome significant issues for the patient undergoingnot only surgery, but specifically laparoscopic surgery.Significant cardiac and pulmonary disorders need to becarefully evaluated in all patients undergoing laparo-scopic surgery as increased intra-abdominal pressureand absorption of CO2 can have serious cardiopul-monary effects in those with preexisting disease. If thehistory or physical examination reveals any evidence ofpossible pulmonary compromise, a complete evalua-tion of pulmonary function should be performed. Ameasurement of forced expiratory volume is useful inthe assessment of pulmonary function.22 This will aidthe anesthesiologist in assessing both the pulmonarytolerance and anesthetic risk of the patient.

The existence of hernias extending from the intra-abdominal cavity must also be discerned. Diaphragmatichernias may allow the pneumoperitoneum to extend intothe thoracic cavity, causing pneumothorax. Herniation ofintra-abdominal contents into the thoracic cavity may alsocause significant mechanical impairment of cardiopul-monary function.53 In general, only those significanthiatal hernias requiring surgical repair are of concern inlaparoscopic surgery.54 Small abdominal wall hernias canusually be mechanically contained easily with bandagesand tapes, but larger hernias may result in ineffectivepneumoperitoneum and are at times a contraindicationto laparoscopic surgery.

Body habitus, notably obesity, may be a contrain-dication to laparoscopic surgery not only for mechani-cal and technical reasons (ie, impairment of inspectionof abdominal contents, inadequate length of instru-mentation, and obscurement of structures due to large



Table 4. Observed Hormonal Physiologic ChangesResulting from Pneumoperitoneum

Hormone* Effect of Pneumoperitoneum

Adrenocorticotropic ↑hormone

Aldosterone ↑Antidiuretic hormone ↑ or stable

Atrial natriuretic factor ↑ or stable

Cortisol ↑Endothelin ↑Renin ↑Urinary potassium ↑Urinary sodium ↓

↑ = increased level/activity of hormone, ↓ = decreased level/activity ofhormone.

*Serum levels unless otherwise noted.

Adapted with permission from Seiba M, Schulsinger D, Sosa RE. Therenal physiology of laparoscopic surgery. AUA update series 2000;XIX (23):182.

(continued on page 12)



amounts of peritoneal fat), but also because the insuf-flation pressure required to maintain pneumoperi-toneum may result in excessively high levels of absorbedCO2. These patients should be carefully evaluatedbecause they may have undiagnosed or subclinical car-diopulmonary disease that may manifest at the time ofCO2 pneumoperitoneum.

Anesthetic evaluation of children undergoing laparo-scopic procedures is best performed by specialists whounderstand the anesthetic needs of children, in particu-lar, those of children undergoing laparoscopic proce-dures. As this area is still evolving, clear communicationbetween the anesthesiologist and the surgeon is manda-tory. Positioning of the patient during the procedure,which has a relatively larger effect on pediatric pulmonaryfunction, is of special importance. The anesthesiologistmay also require increased access (eg, for evaluation ofthoracic expansion) to the pediatric patient during theprocedure to ensure adequate management.23

Although many problems can be adequately man-aged by current anesthetic technique, there are anes-thetic contraindications to laparoscopic surgery thatexist if the specific issues cannot be resolved preopera-tively. These issues include uncorrectable hypovolemia,profound pulmonary emphysema, decompensated car-diac insufficiency, and pulmonary embolism.22

OPERATIVE PREPARATION

In general, anesthetic preparation is the same forlaparoscopy as for the corresponding open surgical pro-cedure that would be performed. The route for intra-venous access is chosen based on the likelihood that thepatient will require large volumes of fluid or possiblyblood transfusion. The need for continuous arterialmonitoring is also determined by the patient’s degreeof cardiopulmonary risk.

In a study of non-obese patients, Ong et al55 notedthat patients had decreased stomach pH and often hadincomplete gastric emptying prior to the administra-tion of anesthesia on the day of surgery. These factorsmay contribute to the development of aspiration pneu-monia. The use of preoperative gastric motility agentsand H2 blockers may promote gastric emptying andincrease the stomach pH, respectively.56 This is an im-portant consideration in that anesthetic deaths relatedto laparoscopic procedures are commonly due to fail-ure of intubation with subsequent aspiration.

Local and regional anesthesia have been used onoccasion for laparoscopic diagnostic procedures, butonly in cases involving a highly cooperative patient andminimal intra-abdominal organ manipulation.57 Use of

the Trendelenburg position may also make respirationdifficult in nonintubated patients, more so in cases ofprolonged procedures. Inadequate respiratory exchangemay lead to significant hypercarbia.58

General anesthesia with intubation and controlledrespiration is considered the safest and most reliableform of anesthesia for patients undergoing laparoscop-ic surgery. Table 5 lists the advantages and disadvan-tages of general anesthesia. Today, a wide variety ofanesthetics allows for well-controlled anesthesia withminimal postoperative side effects.

INTRAOPERATIVE ANESTHETIC MANAGEMENT ANDMONITORING

Noninvasive capnometry (measurement of CO2

concentration during the expiratory phase) is now aroutine part of anesthetic monitoring and is impor-tant in laparoscopic procedures for ensuring thatexcess CO2 is removed from the patient. However, onemust keep in mind that when there is a rapid rise inarterial CO2, there is a lag in the excretion of CO2.Thus, arterial blood gas monitoring may be necessaryin selected patients. Serial measurements of arterialand venous blood gases and transcutaneous blood gasmonitoring may also be considered in elderly patientsand in those with significant pulmonary comorbidi-ties.22 The anesthesiologist should also be made awareof the specific nature of the laparoscopic procedurebeing performed, as evidence suggests that retro-peritoneal18 and extraperitoneal procedures19 may beassociated with increased absorption of CO2. Sub-cutaneous emphysema also is associated with in-creased absorption of CO2.

It is imperative that the anesthesiologist understandsthe effects of pneumoperitoneum on renal function,especially in high risk patients, because treatment ofpneumoperitoneum-induced oliguria by administeringadditional fluids can result in pulmonary edema and con-gestive heart failure. In cases of living donor nephrecto-my, in which the donor is usually in good health, the anes-thesiologist and the surgeon need to maintain an openline of communication to ensure that adequate volumeexpansion and administration of diuretics are carried outin a timely fashion so that renal function is optimized atthe time of division of the renal vasculature.

Most laparoscopic surgeons prefer that nitrous oxidenot be used as an anesthetic, as this agent tends to accu-mulate in air-filled hollow spaces, such as the stomachand intestines. The resulting distention of these struc-tures may restrict the laparoscopic view of the abdominalcavity and interfere with the performance of surgery.

(from page 10)



Nitrous oxide may also delay the dissolution of CO2 inblood, which may result in an air embolism in the heart.22

Non-heated CO2 gas can result in significanthypothermia, especially during prolonged procedures.Heating pads and blankets should be used to preventhypothermia. In addition, units that warm the insufflat-ed gas have recently been employed.

INTRAOPERATIVE COMPLICATIONS OFLAPAROSCOPY

Complications of laparoscopic surgery may be relat-ed to anesthesia or other technical aspects of the proce-dure. This discussion will focus on complications relatedto the establishment and maintenance of pneumoperi-toneum. Complications of laparoscopy that may or maynot be specific to laparoscopy are listed in Table 6.

CARDIOPULMONARY COMPLICATIONS

Decreased chest wall compliance and diaphragmaticexcursion caused by pneumoperitoneum may occasion-ally result in difficulty ventilating the patient. Such diffi-culty also may be caused by the escape of gas into othercompartments. When altered cardiopulmonary func-tion becomes significant and is without explanation, theprocedure should be halted and the pneumoperiton-eum should be released until the source of the difficultyis appropriately identified and addressed. Dependingon the nature of the problem, pneumoperitoneum maythen be re-established with caution.

Cardiovascular collapse is a rare and devastating com-plication of laparoscopic surgery. It may occur intraoper-atively or postoperatively. Its possible causes are listed inTable 7. When cardiovascular collapse occurs intraoper-atively, in addition to immediate specific actions to iden-tify the etiology, pneumoperitoneum is released, anes-thetic concentrations are decreased, intravenous fluid isgiven, and cardiovascular drugs are given as needed.59

Gas Embolism

This potentially fatal complication results from theintroduction of a gas into the intravascular system dur-ing laparoscopy. Although gas embolism is a rare occur-rence, it is critically important that it be recognizedimmediately. Symptoms of gas embolism are listed inTable 8. Possible mechanisms for delivering gas into theintravascular system include22,23,59:

• Attempted insufflation with the Veress needleplaced intravascularly

• Gas uptake through large bleeding venous sur-faces

• Inadvertent placement of CO2 cooled-tiplasers onto tissue surfaces

• High intra-abdominal pressures, allowing forexcessive absorption of CO2

Embolism may occur from a large gas bolus, orthrough the collection of many small gas bubbles.These gas bubbles migrate to the right heart outflowtract and the pulmonary vasculature, where the gascollection forms a gas lock, causing significant circula-tory restriction leading to cardiovascular collapse.60

Owing to the relatively high solubility of CO2, manysmall emboli may be readily dissolved and go unno-ticed. The frequency of small, subclinical gas emboli isnot known. One large study involving patients under-going gynecologic laparoscopy noted a probable inci-dence of 0.59% of subclinical gas emboli.61

Table 5. Advantages and Disadvantages of GeneralAnesthesia for Laparoscopic Procedures

Advantages

Excellent muscle relaxation, which allows control of voluntary and involuntary movement

Ventilation can be controlled, allowing the elimination of CO2

and the prevention of hypercarbia

The operative field is still, allowing for the safe use of electrocautery and other operating instrumentation

Complete analgesia

The risk of gastric aspiration is minimized by the use of cuffed endotracheal tubes and orogastric decompression

Amnesia is achieved and anxiety can be eliminated

The discomfort to the patient from prolonged Trendelenburgpositioning (eg, headache) is minimized

Disadvantages

Recovery from the anesthetic agents may be prolonged

Additional stress may be placed on patients with severe cardiac or pulmonary disease

Postoperative throat irritation and pulmonary complications may result from intubation

Inappropriate use of positive-pressure face mask ventilation or esophageal placement of endotracheal tube may lead to distention of the stomach

Overzealous assisted or controlled ventilation may produce pneumothorax, especially in patients with pulmonary blebs.

Data from Richter and Kloppik.22



Transesophageal echocardiography is considered thegold standard method for detecting gas emboli.62 Theuse of a precordial doppler stethoscope and end-tidalCO2 monitoring allow for the early detection of a gasembolus. A CO2 embolus may cause a sharp increase inend-tidal CO2 pressure. Capnography, which is used forthe assessment of arterial CO2 pressure, may also be use-ful in making the diagnosis. Aspiration of gas or foamingblood from a central venous line also confirms the diag-nosis of embolism. The classical “mill-wheel” murmur isusually a late finding.

When gas embolism is suspected or has been diag-nosed, the pneumoperitoneum should be released im-mediately and standard resuscitative measures initiated.The patient should be placed in steep Trendelenburgposition with the right side up, and attempts should bemade to aspirate the obstructing embolus via a centralvenous line. The patient should be given 100% oxygen,with hyperventilation to increase CO2 excretion (in mostcases, as CO2 is commonly the insufflant being used).Cardiopulmonary resuscitation may be necessary formaintenance of oxygenation.59

Proper technique when using the Veress needle is im-portant for preventing gas embolism. Clear and opencommunication with the anesthesiologist is important toensure that the patient is relaxed and is not abdominallystraining. Incomplete relaxation and abdominal strainingwill make it difficult for the surgeon to confirm the prop-er position of the Veress needle. This needle should neverbe inserted with the gas line attached. Upon insertion,one should first aspirate to rule out intravascular place-ment. Next, after a small volume of saline solution isinjected, one should not be able to withdraw the solution.The syringe is then removed, with the remaining salinesolution that is left in the hub of the Veress needle fallinginto the abdominal cavity under gravity, confirming prop-er placement of the needle. The gas line is then attachedand insufflation is initiated slowly at a low rate of flow.

Notable indicators of intravascular needle placementinclude pulsations of the insufflator flow meter matchingthe patient’s pulsations and the absence of signs of dis-tention of the abdomen despite the insufflation of ade-quate volumes of gas. Maintaining intra-abdominal pres-sures at or below 15 mm Hg, especially in the presence ofsignificant venous bleeding surfaces in the operativefield, may decrease the risk of emboli. Careful and prop-er use of a CO2 cooled-tip laser is also important.22,60

Arrhythmias

Arrhythmias have been noted to occur in up to 27% ofpatients undergoing laparoscopic surgery22 and are oftendue to hypercarbia. The use of the anesthetic halothaneshould be avoided during laparoscopic surgery, as thisagent may lead to ventricular arrhythmias in the presenceof high levels of CO2.63

Management of arrythmias includes reducing theintra-abdominal pressure, increasing ventilation with oxy-gen, and the use of anti-arrhythmic drugs as necessary.

Table 6. Potential Complications of Laparoscopy

Intraoperative complications

Bladder perforation

Bowel perforation

Cardiovascular collapse

Gas embolus

Hemorrhage

Injury to bowel mesentery

Neurologic injury

Orthopedic injury

Pneumomediastinum

Pneumopericardium

Pneumothorax

Subcutaneous emphysema

Vascular injury

Postoperative complications

Atelectasis/pneumonia

Bowel obstruction

Incisional hernia

Infection

Adapted with permission from See WA. Overview of Complicationsof Urologic Laparoscopy. In: Gomella LG, Kozminski M, Winfield HN.Laparoscopic urologic surgery. New York: Raven Press; 1994:250.

Table 7. Causes of Cardiovascular Collapse orHypotension During Laparoscopic Surgery

Diaphragmatic rupture

Gas embolus

Intra-abdominal hemorrhage

Myocardial infarction

Pneumomediastinum

Pneumothorax

Tension pneumoperitoneum

Vasovagal reflex

Data from Gomella et al.59

SUBCUTANEOUS EMPHYSEMA, PNEUMOMEDIASTINUM,PNEUMOPERICARDIUM, AND PNEUMOTHORAX

Common to the etiology of subcutaneous emphyse-ma, pneumomediastinum, pneumopericardium, andpneumothorax is the leakage of gas out of the intendedworking space and into one of these specific spaces(Figure 3). These complications may occur any timeduring the laparoscopic procedure, from the initiationof pneumoperitoneum until removal of the insufflatingcannula. Diagnosis may be made by physical examina-tion, radiography (Figure 4), or other abnormal find-ings noted by the anesthesiologist. These complicationscommonly result from improper positioning of theVeress needle, leakage of CO2 around working trocars,malfunction or improper use of the insufflator, or un-recognized previous injuries.

Improper Placement of the Veress Needle

Unrecognized subcutaneous emphysema resultingfrom preperitoneal placement of the Veress needle makesthe subsequent correct placement more difficult. This dif-ficulty arises because preperitoneal insufflation reducesthe relative volume of the peritoneal cavity and increasesthe distance that the needle must traverse to reach theperitoneal cavity. Improper needle placement can be rec-ognized early by monitoring the pressure of the peri-toneal cavity during insufflation. The large potential spaceof the peritoneal cavity should fill under low pressurewhen the Veress needle is placed unoccluded in the peri-toneal cavity. A high pressure level upon initiation of insuf-flation may indicate improper needle placement.

If not immediately noted, preperitoneal needle place-ment will likely be recognized at the time of primary tro-car insertion, at which time there will be minimal returnof CO2. Visualization of only fat at this point is also high-ly suggestive that the needle has been improperly placed.Improper needle placement may also be recognized byearly development of pneumoscrotum.

Upon recognition of subcutaneous emphysema, anddepending on the degree to which it has occurred, cours-es of action may include evacuation of the insufflatedspace and a repeated attempt at placement of the Veress

needle, minilaparotomy and use of the Hasson cannula,or abandonment of the laparoscopic approach. In mildcases and in those in which most of the insufflant can beevacuated, a repeated attempt at peritoneal access byeither reinsertion of the Veress needle or minilaparoto-my is usually successful.

Leakage of CO2 Around Working Ports

Leakage around the working ports causes subcuta-neous emphysema. In its mild to moderate form, thisoccurs quite commonly. In such cases no specific inter-vention is required because the condition will readily



Table 8. Symptoms of Gas Embolism

Rapid drop of end-tidal CO2 pressure

Sudden bradycardia

Distinct arterial hypotension

Precordial mill-wheel sound on cardiac auscultation

Data from Richter and Kloppik.22

Figure 3. Possible routes of gas into thoracic spaces. Persistentfetal connections include the pleuroperitoneal membrane (A1),pleuropericardial membrane (A2), and pericardial canal (A3). Gasmay pass around great vessels in an extrafascial plane such as atthe diaphragmatic hiatus (B1), pulmonary hilus (B2), or theentry/exit of the great vessels at the heart (B3). Extraperitonealor extrapleural gas can dissect in between fibers of thediaphragm (C1) and subcutaneous gas may extend directly fromthe anterior neck into the superior mediastinum (C2). Finally,barotrauma may allow ventilatory gas to enter the pleural cavi-ty or mediastinum (D). Reprinted with permission from Wolf JS,Monk TG. Anesthetic considerations. In: Smith AD, Badlani GH,Bagley DH, et al, editors. Smith’s textbook of endourology. St.Louis (MO): Quality Medical Pub; 1996:740.

C2

B3

B2

B1C1 A3

A1

D

A2



resolve soon after completion of the procedure. How-ever, extreme cases can have serious sequelae. Severesubcutaneous emphysema may compromise chest wallexcursion and may make it difficult for the anesthesiol-ogist to ventilate the patient. Severe subcutaneous em-physema may also result in significant hypercarbia; insuch cases, one should completely investigate the etiol-ogy of this serious complication, including the possibil-ity of insufflator malfunction.

In addition to subcutaneous emphysema, improp-er insertion of the insufflating cannula may result inpneumothorax, pneumomediastinum, and pneumo-pericardium, although it appears that these occurquite rarely. Since there are no specific diagnostic cri-teria for these entities, atypical intraoperative pul-monary and cardiac problems demand exclusion ofthese entities. Diagnosis of these entities may be facil-itated by obtaining plain film radiographs of thechest. As CO2 will gradually be absorbed, treatment ofthese entities is supportive.

Problems Related to the Insufflator

The insufflator is essential for successful performanceof laparoscopy. Both malfunction and misuse of thisdevice may result in increased intraperitoneal pressureswith introduction of CO2 into various compartments andstructures. A thorough knowledge of the working of thisdevice is essential. Many consider a preset upper limitpressure of 15 mm Hg to be safe for performance of rou-tine laparoscopy. As with all such operative equipment,

this device should be periodically inspected by qualifiedpersonnel to ensure its proper function.

Unrecognized Injuries

Laparoscopy is being frequently performed with in-creasing frequency in trauma patients, both for diagnos-tic and therapeutic purposes. Although laparoscopy isgenerally safe and effective, one must always keep inmind that a traumatic injury, such as a diaphragmatic lac-eration, can result in introduction of CO2 into the tho-racic cavity with resultant tension pneumothorax.Unnoticed diaphragmatic injuries during upper abdom-inal laparoscopic procedures may also lead to this com-plication. Traumatic vascular injuries may result in intra-vascular gas absorption and embolism. Peritoneal defectsmay result in significant amounts of subcutaneousemphysema.10 A proper assessment and suspicion forinjuries is essential in the preoperative assessment of thetrauma patient undergoing laparoscopy.

HYPOTHERMIA

Hypothermia may result in cases of prolongedlaparoscopic procedures. Large volumes of unheatedCO2 can cause cooling of the core body temperatureby approximately 0.3°C per 50 L of CO2 used.64 Specialconsideration should be given to children, who have ahigher ratio of surface area to body weight and do notsustain body temperatures as well as adults in coldenvironments.23 Prevention of hypothermia includeshaving a warm operating room, use of heating blan-kets, and limiting operating time. Devices that warmthe insufflant are also available and may be useful inthe prevention of hypothermia.

POSTOPERATIVE CONSIDERATIONS

PULMONARY CONSIDERATIONS

Studies reveal that approximately 50% of insufflatedgas is removed through the trocars upon termination ofpneumoperitoneum, 20% is absorbed by abdominalcompartments, and 30% remains in the abdominalspace.21 Thus, approximately 50% must be removed bythe lungs postoperatively. The typical physiologic re-sponse to hypercapnia is an increase in tidal volume.Tolksdorf65 observed that after a laparoscopic proce-dure, postoperative spontaneous hyperventilationresults in a return to normal levels of exhaled CO2 by3 hours postoperatively. Thus, the administration of suf-ficient postoperative analgesia should involve judicious

Figure 4. Chest radiograph demonstrating subcutaneous emphy-sema. Pneumomediastinum can also be seen.



use of agents that do not cause significant respiratorydepression during the first 3 hours of the postoperativeperiod.22

Laparoscopic interventions in the upper abdomenoften result in decreases in vital capacity, forced expiratoryvolume, and functional residual capacity.22 The decreasein functional residual capacity may result in some short-term postoperative hypoxia and postoperative atelectasis.Adequate postoperative respiratory support (usually ashort period of supplemental oxygenation in select pa-tients) and pulmonary toilet will alleviate these effects.

POSTOPERATIVE COMPLICATIONS

Most postoperative complications, including bleed-ing and infection, are related to technical aspects of theprocedure. Other technical complications are relatedto the specific nature of the procedure performed.However, complications related to physiologic aspectsof laparoscopy also exist, and at times may not be read-ily discernible from certain technical complications.Patients undergoing laparoscopic procedures mostoften report less postoperative pain than those under-going similar open procedures; in the immediate post-operative period, however, these patients may also haveabdominal pain related to stretching or pulling of theabdominal wall during the procedure.

Significant abdominal pain that does not resolveshould arouse suspicion of an underlying injury, suchas bowel perforation or intra-abdominal bleeding. Arecent review of the literature by Bishoff and col-leagues66 reveals that bowel perforation related tolaparoscopic surgery is a rare complication, occurringin only 1.3 cases per 1000. Patients with this complica-tion may present in unusual fashions. In Bishoff’sseries, patients whose abdominal injuries were not rec-ognized intraoperatively tended to have severe painassociated with a single trocar site, abdominal disten-tion, diarrhea, and leukopenia. These signs were fol-lowed within 96 hours of surgery by acute cardiopul-monary collapse related to sepsis.66 Accordingly, onemust maintain clinical suspicion of such atypical signsand symptoms. Bleeding may be evidenced by changesin vital signs and complaints of abdominal pain in asso-ciation with a falling hematocrit. Such patients shouldundergo prompt evaluation with radiologic imagingand re-exploration if necessary.

Shoulder pain caused by irritation of the diaphragmby CO2 commonly occurs after laparoscopic proce-dures. The pathophysiology of this irritation is mostlikely a combination of direct stretching of the dia-phragm caused by insufflation and the release of hydro-

gen ions as a consequence of the reaction between CO2

and water. This phenomenon occurs in up to one thirdof patients, but is severe in fewer than 5% of patients.Shoulder pain often responds well to oral analgesicsand anti-inflammatory agents and usually resolves with-in 24 to 48 hours.59 Complete evacuation of CO2 at theend of the procedure may help decrease the incidenceof this problem. Evacuation of CO2 with the patient inthe Trendelenburg position may prevent the entrap-ment of gas in the upper abdomen. Slow insufflation ofthe abdomen may also decrease the incidence of thisentity.

CASE DISCUSSIONS

CASE 1 PRESENTATION

Patient 1 is a 65-year-old man with a 6-cm left renalmass consistent with a neoplasm. He wishes to knowwhether he is a candidate for a laparoscopic radicalnephrectomy. His past medical history is significant forbowel obstruction, for which he had 2 open transab-dominal procedures many years ago. His bowel func-tion has now been regular for many years. He has coro-nary artery disease for which he had coronary arterybypass grafting 2 years ago. He has not had any cardiacsymptoms since this time. He has a smoking history of1 pack of cigarettes daily for 25 years, but he has notsmoked since the time of his bypass surgery.

• Does patient 1’s previous coronary artery diseasepreclude laparoscopic surgery?

This patient is evaluated by both the anesthesiologistand his internist, as well as the urologist. A thoroughhistory and physical examination are performed, as wellas a chest radiograph and electrocardiogram, whichreveal no evidence of cardiopulmonary insufficiency.Patient 1’s cardiac condition has been successfully treat-ed and there is no indication that he should not be ableto tolerate laparoscopy with CO2 insufflation with ap-propriate anesthetic monitoring.

• How does patient 1’s history of bowel obstructionaffect his surgical options?

Patient 1’s significant history of bowel obstructionmeans that he is likely to have intra-abdominal boweladhesions. However, this history does not necessarilyexclude him from consideration for a laparoscopicprocedure. Although blind entry with a Veress needleis not recommended, the surgeon could perform a



minilaparotomy and safely place a Hasson-type blunttipped cannula under direct vision and assess thedegree of adhesions and the feasibility of transperi-toneal laparoscopy after lysis of possible adhesions.Alternatively, if the surgeon has experience with retro-peritoneoscopy, a retroperitoneoscopic nephrectomywould be the preferred technique.

• How should patient 1 be monitored intraoperatively?

Patient 1 should receive general endotracheal anes-thesia. If possible, the use of nitrous oxide should beavoided because it may result in significant bowel dis-tention and possible compromise of the laparoscopicprocedure.

Patient 1 should be monitored with standard anes-thetic equipment currently in use during laparoscopyand many open procedures. This includes capnometryand continuous cardiac telemetry. Close monitoring ofcardiac telemetry is particularly important in this patientbecause cardiac arrhythmias, which occur often duringlaparoscopic procedures, may be even more prevalent inpatients with a history of open heart surgery.

Cardiovascular drugs necessary for treatment ofarrhythmias should be readily available. In addition,although this patient’s medical comorbidities are welltreated and controlled, placement of an arterial lineallows continuous blood pressure monitoring and maybe useful in the early detection of elevated blood levelsof CO2. Monitoring of blood CO2 levels may be espe-cially important in retroperitoneal procedures, as theseare associated with increased CO2 absorption.

• Patient 1 undergoes a retroperitoneoscopic radicalnephrectomy without incident. How should he bemanaged postoperatively?

This patient is likely to have an uneventful postop-erative course with early resumption of diet, minimalpostoperative pain, and discharge home within 2 to3 days. Because most excess CO2 in the body is re-moved by the lungs in the first 3 hours after thelaparoscopic procedure, it is important that appro-priate postoperative monitoring be conducted withsupplemental oxygenation as needed. In addition,analgesics that can cause significant respiratorydepression should be avoided. Inspiratory spirometryis useful in the prevention of postoperative atelectasis,which occurs following laparoscopic procedures aswell as open procedures.

CASE 2 PRESENTATION

Patient 2 is an otherwise completely healthy 32-year-

old woman with right ureteropelvic junction obstruc-tion who is under going a laparoscopic right pyeloplas-ty. After placement of the Veress needle, insufflation,and placement of the camera through the initial trocar,only preperitoneal fat is seen.

• What is the appropriate course of action at this point?

The Veress needle has been improperly placed intothe preperitoneal space. This problem is usually evi-denced by unusually high fluctuating pressures uponinitial insufflation; and it is rare for it to be recognizedat the time of camera insertion. Insufflation should bestopped as soon as the problem is identified. An at-tempt should be made to evacuate as much CO2 aspossible from the preperitoneal space. If most of thegas is removed and disruption of the anatomy of theanterior abdominal wall is minimal, another attemptat Veress needle placement could be undertaken withvigilant attention paid to technique and initial in-sufflation pressures. It may be more prudent, howev-er, to perform a minilaparotomy with placement of aHasson-type cannula to avoid any further exacerba-tion of this problem. Because the CO2 gas remainingin the preperitoneal space will be absorbed, it isimportant that the surgeon clearly communicate tothe anesthesiologist that preperitoneal needle place-ment occurred.

• A Hasson-type cannula is placed under direct vision,and a laparoscopic pyeloplasty is performed. Uponcompletion of the procedure, it is noted that thepatient has a high degree of subcutaneous crepitus.How should this be managed?

A significant degree of subcutaneous emphysema hasformed in this patient. This may have resulted from fur-ther leakage into the preperitoneal space or from leak-age around the trocars at the trocar sites. Discerning theetiology of this problem is important because any noteddifficulties with technique or equipment, including theinsufflator, should be remedied.

When subcutaneous emphysema is substantial, onemust first assess whether subcutaneous gas is presentup to the level of the neck and ensure that there is noairway compromise. The patient should be extubatedonly when there is clear evidence that the subcuta-neous emphysema is not significantly interfering withchest wall mechanics. In certain cases, depending onthe specific nature of the etiology, one should rule outsignificant pneumopericardium or pneumomedi-astinum with a chest radiograph. As the gas will allgradually be absorbed, supportive care, depending on



the degree of subcutaneous air, is the mainstay oftreatment.

CONCLUSION

Advances in technology and understanding of thephysiologic processes involved have allowed urologic sur-geons to successfully perform virtually every major uro-logic procedure in a laparoscopic fashion. However, thelaparoscopic urologic surgeon must always maintain acomplete knowledge of laparoscopic physiology in orderto ensure that an ever-increasing number of pediatric,elderly, medically ill, and otherwise healthy patients un-dergo laparoscopic surgery in a safe environment.

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