Diana Diana ScolaroScolaro-Cook RN,BSN,CCRN-Cook RN,BSN,CCRNPediatric Intensive Care Nurse, Pediatric Intensive Care Nurse, OHSU,OHSU, Doernbecher Doernbecher Children’s Hospital Children’s Hospital

Pediatric Anesthesia Issues

Children are not small adults Differ physiologically and psychologically

Drug dosage different than adults Size difference Sometimes unpredictable response Constant vigilance needed Rapid deterioration of cardiorespiratory mechanism

Pediatric Anesthesia Issues

Goals of Presentation:

Basic understanding of pediatric cardiac and respiratory physiology

Management of pediatric emergency situations

Pediatric Cardiovascular Physiology

Function of Heart: Deliver a sufficient cardiac output to meet body’s metabolic needs

Cardiac output (CO) = Heart Rate(HR) x Stroke Volume (SV) SV = Preload, Afterload, Contractility Children usually heart rate dependent Bradycardia in children should be presumed to be due to hypoxia until proven otherwise

Stroke Volume Preload:

Too high: diuretics, arrhythmias, poor cardiac function

Too low: volume load Afterload:

Too high: vasodilators Too low: vasoconstrictors

Contractility: Hyperdynamic: B Blockers Depressed: Digoxin, Inotropes

Physical ExaminationImpaired cardiac function often recognized first by physical examination techniquesHeart rateQuality of pulsesCapillary refillSkin temperature/color

Physical Examination

Reduced cardiac outputDifficulty in palpating distal pulses

Tachycardic/BradycardicProlonged capillary refill (>3 sec)

Cool skin, mottled appearance

Physical ExaminationBlood pressure

Remains within normal parameters until decompensation

Physical ExaminationBlood pressure

Physiological changes to maintain blood pressureSecretion of antidiuretic hormoneHeart rate increasesSecretion of aldosterone/renin

Cardiac DysrhythmiasNot common in pediatricsMay be associated with congenital heart disease

Usually classified as rapid/slow, hemodynamically stable/unstable

Significant when associated with a fall in cardiac output

Cardiac DysrhythmiasMay be associated with sedation/anesthesiaSinus bradycardiaVentricular tachycardiaSupraventricular tachycardia

Pediatric Respiratory Physiology

Anatomy of Pediatric AirwayNarrowest portion at cricoidLarynx at C3-4 (Adult C4-5)Cuffed endotracheal tube > 8 years of age

Lymphatic tissue present and may lead to airway obstruction

Pediatric Respiratory Physiology

Resistance ImportantChild’s airway smallerResistance to airflow inversely proportional the 4th power of the radius of the lumen

R=8nl/πr4

Causes of Increased Airway Resistance

AsthmaUpper respiratory tract infections

AllergiesObstructionSecretions in airway

Airway ObstructionMay occur with oral soft tissues

TonguePharyngeal structuresSecretionsAirway swellingViral infectionsAsthma

May present with stridor/wheezing

Respiratory Mechanics Minute Ventilation (VE)

Tidal Volume (TV) X Respiratory Rate (RR)

Alveolar Ventilation (VA) (Tidal Volume – Dead Space) X RR Dead space – nose, pharynx, large airways: No interchange of CO2/O2

Alveolar Oxygenation (PaO2)

FiO2 (Barometric Pressure – Water Pressure) – PaCO2/RQ

RQ = Respiratory QuotientImportant Concept

As PaCO2 increases, PAO2 decreases

SaO2 decreases

Decreased Oxygen Saturation (SaO2)

Atelectasis – V/Q mismatching shunts

Dead space ventilation Pneumothorax Tamponade Pulmonary embolus Loss of respiratory drive Pleural effusions

Functional Residual Capacity (FRC)

FRC is source of oxygen during expiration until lungs reinflate with next breath When FRC decreased, then lung segments are closed leading to atelectasis and hypoxia

Segments are closed leading to atelectasis and hypoxia FRC reduced when closing capacity exceeds FRC

N Engl J Med 287:690-698, 1972.N Engl J Med 287:690-698, 1972.

Functional Residual Capacity (FRC)

Children < 6 years of age and adults >40 years of age have a closing capacity > FRC in the supine position

Pediatric Emergency Issues

Loss of AirwayMaintain with BVM using head tilt/chin lift or jaw thrust

Intubate if unable to manage airway or if unable to oxygenate/ventilate

Proper Endotracheal Tube Placement

Fog in tube: not necessarily in tracheal Chest rise: not necessarily in trachea Bilateral breath sounds: gastric air can mimic breath sounds

Detection of CO2 – extremely useful but Can be in esophagus with yellow (CO2) color if patient has taken NaHCO3 for any reason

Can be in trachea with lavender color (No CO2) Cardiac arrest Pulmonary hypertension Complete airway obstruction

Best Way to Assess Proper Placement

See tube pass between cords Chest rise Presence of CO2 Breath sounds present bilaterally/none over epigastrum

If bradycardic – an increase in heart rate

O2 saturations may be low or unobtainable with vasoconstriction

StridorEpinephrine 1:1000 solution: 0.01 mg/kg up to 0.5 mg sub q

Decadron: 0.25-0.5 mg/kg IV every 8 hours for 5 doses

Epinephrine nebs:0.05 cc/kg

Wheezing:BronchospasmAlbuterol nebs:0.01-0.03 cc/kg (2.5 mg)

Solumedrol: 1 mg/kg q 6 hours IV.Atrovent nebs:2-4 puffs q 4 hoursMgSO4: 40 mg/kg IV (Bronchodilation)

Epinephrine: 0.01 mg/kg sub q as for stridor

Hypotension

Airway

Heart Rate-Avoid bradycardia: Atropine 20 mcg/kg IV for vagally induced bradycardia not to be < 0.1 mg OR epinephrine 0.01 mg/Kg 1:10000 IV

Vasodilation: warm extremities, increased capillary refill

Fluid boluses with 20 cc/kg LR/NS

Ephedrine:0.2 mg/kg IV (releases endogenous catecholamines)

Phenylephrine:0.1-0.5mg/kg IV

Vasoconstriction: Cold extremities, delayed capillary refill

Fluid bolus as previously described

Epinephrine: 0.01 mg/kg 1:10000 IV

Cardiac DysrhythmiasSupraventricular Tachycardia:

Hemodynamically stable: Vagal maneuvers successful 25%

Adenosine:100-250 mcg/kg rapid IV push

Hemodynamically unstable: hypotension, neurologically compromised, mottled, etc

Cardioversion: 0.5-1.0 J/Kg synchronized mode

Hemodynamically unstable without pulse: CPR, defibrillation 2 J/kg-4 J/kg.

Hemodynamically unstable with pulse: Synchronized cardioversion:0.5-1.0 J/Kg

Sinus BradycardiaEliminate hypoxia as causeAtropine: 20 mcg/kg IVEpinephrine: 0.01 mg/kg IVIsoproterenol:0.1-0.2 cc/kg of 1:50,000 solution

SeizuresCorrect hypoxemia/airway

Ativan:0.05-0.1 mg/kg IV

Midazoloam:0.1 mg/kg IV

Phenobarbitol: 20 mg/kg IV

Fosphenytoin:15 mg/kg IV

Glucose:0.5 mg/kg D25 or 1 mg glucagon IV/IM.

Summary

Children are not small adultsDiffer physiologically, psychologically and developmentally from adults

Medication dosages are different

Rapid cardio-respiratory decompensation is a possibility at all times