Posterior Fossa Posterior Fossa ProceduresProcedures

(Infratentorial (Infratentorial Craniotomy)Craniotomy)

and Neuroanesthesia and Neuroanesthesia EmergenciesEmergenciesMani K.C Vindhya M.DMani K.C Vindhya M.D

Asst Prof of AnesthesiologyAsst Prof of Anesthesiology

Nova Southeastern UniversityNova Southeastern University

Anesthesia forAnesthesia for Posterior Fossa Posterior Fossa ProceduresProcedures

(Infratentorial Craniotomy)(Infratentorial Craniotomy)and Neuroanesthesia Emergenciesand Neuroanesthesia Emergencies

I. Format = approach to posterior fossa caseI. Format = approach to posterior fossa case Preoperative concerns – Preoperative concerns –

Problem list? Problem list? Further labs and studies? Further labs and studies? Optimization? (Is the patient optimal for surgery?) Optimization? (Is the patient optimal for surgery?)

Consults? Consults? Further medical treatment? Further medical treatment?

Intraoperative concerns Intraoperative concerns Premedication Premedication Monitoring Monitoring Induction Induction Maintenance Maintenance Intra-op complications (2 main complications?) Intra-op complications (2 main complications?) Emergence Emergence

Postoperative concerns – only on the long stem Postoperative concerns – only on the long stem 2 main complications? 2 main complications? Post-op pain relief Post-op pain relief

Posterior fossa considerations Posterior fossa considerations Case Presentation. Case Presentation.

An 18 year-old male for posterior fossa exploration and excision of cerebellar mass An 18 year-old male for posterior fossa exploration and excision of cerebellar mass lesion.lesion.

History History headache headache nausea and vomiting nausea and vomiting impaired hearing impaired hearing occasional diplopia occasional diplopia

Physical exam Physical exam ataxia ataxia severe bilateral papilledema (3/4) severe bilateral papilledema (3/4) BP = 120/70 to 140/80 BP = 120/70 to 140/80 weight = 65 kg weight = 65 kg

CT scan CT scan cerebellar mass lesion cerebellar mass lesion hydrocephalus hydrocephalus

The neurosurgeon desires intraoperative monitoring of: The neurosurgeon desires intraoperative monitoring of: brain stem auditory evoked potentials (BAEP's) brain stem auditory evoked potentials (BAEP's) facial nerve (cranial nerve VII) function facial nerve (cranial nerve VII) function

Problem List: Problem List: Cerebellar mass lesion with Cerebellar mass lesion with

hydrocephalus hydrocephalus Increased ICP Increased ICP Positioning -- sitting, prone, lateral, or Positioning -- sitting, prone, lateral, or

supine (semi-lateral) supine (semi-lateral) "Full stomach" -- nausea and vomiting, "Full stomach" -- nausea and vomiting,

increased ICP increased ICP Intraoperative monitoring Intraoperative monitoring

Brainstem auditory evoked potentials Brainstem auditory evoked potentials Facial nerve function (motor testing)Facial nerve function (motor testing)

Posterior FossaPosterior Fossa Is a "closed-in" space Is a "closed-in" space

Bone - on sides, back, and bottom Bone - on sides, back, and bottom Tentorium - on top (Posterior fossa is "infratentorial.") Tentorium - on top (Posterior fossa is "infratentorial.") Brain stem - in front Brain stem - in front

Contains about 1/4 of intracranial contents Contains about 1/4 of intracranial contents Tumors in the posterior fossa Tumors in the posterior fossa

ChildrenChildren Intracranial neoplasms = the most common solid tumors in Intracranial neoplasms = the most common solid tumors in

childhood (about 25% of all admissions for neoplastic disease).childhood (about 25% of all admissions for neoplastic disease). Posterior fossa = the site of origin of 50 to 60% of brain tumors in children. Posterior fossa = the site of origin of 50 to 60% of brain tumors in children.

Adults -- uncommon site for brain tumors Adults -- uncommon site for brain tumors Tumors in the posterior fossa are often:Tumors in the posterior fossa are often:

"Benign by histology" "Benign by histology" "Malignant by location" "Malignant by location"

Posterior fossa tumors can compress the brain stem (pons and medulla).Posterior fossa tumors can compress the brain stem (pons and medulla). CSF outflow tracts CSF outflow tracts Cardiovascular centers Cardiovascular centers Respiratory centers -- pneumotaxic center, apneustic center Respiratory centers -- pneumotaxic center, apneustic center

dorsal respiratory group, ventral respiratory group3 d. Lower cranial nerves (and functions):

V Trigeminal Facial sensation VI Abducens Eye abduction VII Facial Facial muscles (motor) VIII Acoustic Hearing IX Glossopharyngeal Gag reflex X Vagus Cough reflex, laryngeal muscles XI Spinal accessory Shoulder movement XII Hypoglossal Tongue movement

Posterior Fossa Posterior Fossa

Explanation of symptoms in Explanation of symptoms in case presentationcase presentation

1. Elevated intracranial pressure (ICP) triad secondary to hydrocephalus - headache, nausea (and vomiting), papilledema

2. Cerebellar involvement -- ataxia 3. Brain stem involvment

a. Hearing loss (involvement of C.N. VIII) b. Diplopia (probably involvement of C.N. VI)

Sitting PositionSitting Position

Situations Situations in which sitting position might be used are mainly:in which sitting position might be used are mainly: Posterior fossa procedures Posterior fossa procedures Cervical laminectomy Cervical laminectomy

Establish which position the surgeon desires Establish which position the surgeon desires for posterior for posterior fossa surgery:fossa surgery:

Sitting Sitting Prone Prone Lateral decubitus Lateral decubitus Supine (semi-lateral) Supine (semi-lateral)

Proper positioning Proper positioning for a seated posterior fossa operationfor a seated posterior fossa operation Knees at heart level Knees at heart level

Neck not hyperflexed Neck not hyperflexed

Sitting PositionSitting Position

Advantages of the sitting position includeAdvantages of the sitting position include: :

Excellent surgical access Excellent surgical access Comfort for the surgeon Comfort for the surgeon Facilitates hemostasis (decreased Facilitates hemostasis (decreased

blood loss) blood loss) Improved venous and CSF drainage Improved venous and CSF drainage Exposes face for monitoring response Exposes face for monitoring response

to cranial nerve stimulation (though to cranial nerve stimulation (though this can also be done electronically)this can also be done electronically)

Possible sitting position complications include:Possible sitting position complications include: Air embolism (venous and arterial) Air embolism (venous and arterial) Cardiovascular instability Cardiovascular instability

Hypotension Hypotension Venous pooling Venous pooling Cardiac arrhythmias Cardiac arrhythmias

Neurologic complications Neurologic complications Quadriplegia Quadriplegia Nerve injuries (e.g. ulnar, sciatic, lateral peroneal) Nerve injuries (e.g. ulnar, sciatic, lateral peroneal)

Pneumocephalus Pneumocephalus Airway obstruction Airway obstruction Airway swelling (head and tongue) Airway swelling (head and tongue) Malpractice risk. The use of the sitting position for posterior fossa neurosurgery is Malpractice risk. The use of the sitting position for posterior fossa neurosurgery is

somewhat controversial.somewhat controversial. Current practice is away from operating in sitting position6 Current practice is away from operating in sitting position6 No evidence that position affects outcome.No evidence that position affects outcome. Venous air emboli can occur in any position -- Venous air emboli can occur in any position -- sitting, lateral, prone, or supinesitting, lateral, prone, or supine

Relative Contraindications to Sitting PositionRelative Contraindications to Sitting Position

Known cardiac septal defect = a "red Known cardiac septal defect = a "red flag" flag"

Patent foramen ovale (PFO) Patent foramen ovale (PFO) Atrial septal defect Atrial septal defect Ventricular septal defect Ventricular septal defect

Right atrial pressure > left atrial pressure Right atrial pressure > left atrial pressure Functioning ventriculo-atrial shunt Functioning ventriculo-atrial shunt ?? cardiac instability ?? cardiac instability ?? extremes of age?? extremes of age

Air Emboli (Venous and Arterial)Air Emboli (Venous and Arterial)

Incidence of venous air emboli Incidence of venous air emboli (VAE) (VAE) can be as high as 50% in neurosurgery.can be as high as 50% in neurosurgery.

Incidence of VAE depends on both Incidence of VAE depends on both monitoring and position.10 monitoring and position.10

"Bottom line" on VAE: "Bottom line" on VAE: More frequent in the sitting position. More frequent in the sitting position. BUT -- VAE can occur in BUT -- VAE can occur in anyany position. position. Early detection and prevention with the Early detection and prevention with the

Doppler and other more sensitive Doppler and other more sensitive VAE monitoring methods have:VAE monitoring methods have: Decreased the occurrence of clinically Decreased the occurrence of clinically

significant VAE significant VAE Increased the reported incidence of VAE Increased the reported incidence of VAE

Relative sensitivity of techniques to monitor for VAERelative sensitivity of techniques to monitor for VAE

Comments on VAE monitors Comments on VAE monitors Bubble Doppler -- still a very sensitive and practical way to detect Bubble Doppler -- still a very sensitive and practical way to detect

VAE VAE Transesophageal ECHO (TEE) Transesophageal ECHO (TEE)

The most sensitive way to detect VAE. The most sensitive way to detect VAE. The only way to document intraoperative "paradoxical air The only way to document intraoperative "paradoxical air

emboli" which have crossed to the arterial circulation, unless the emboli" which have crossed to the arterial circulation, unless the surgeon sees air bubbles in arteries! surgeon sees air bubbles in arteries!

ECHO could be used to detect a patent foramen ovale preop.ECHO could be used to detect a patent foramen ovale preop. Incidence of patent foramen ovale = about 1 in 4. Incidence of patent foramen ovale = about 1 in 4. A paradoxical air embolus can occur even if a person does not have a A paradoxical air embolus can occur even if a person does not have a

patent foramen ovale. Air can traverse the pulmonary circulation.patent foramen ovale. Air can traverse the pulmonary circulation. Why don't we get pre-op ECHO's for all sitting position cases? Why don't we get pre-op ECHO's for all sitting position cases?

Expensive Expensive The number of complications as a result of paradoxical air emboli is The number of complications as a result of paradoxical air emboli is

actually small actually small

Pulmonary artery pressures (PAP) Pulmonary artery pressures (PAP)

CVP catheters: CVP catheters: Have two uses regarding VAE: Have two uses regarding VAE:

VAE detection (much less sensitive than Doppler or TEE) VAE detection (much less sensitive than Doppler or TEE) VAE aspiration (potentially life-saving in some situations) VAE aspiration (potentially life-saving in some situations)

How do you confirm CVP catheter placement in the right atrium How do you confirm CVP catheter placement in the right atrium (to aspirate air lock if VAE occurs)?(to aspirate air lock if VAE occurs)? Length of catheter (but could be in jugular vein) Length of catheter (but could be in jugular vein) Rapid saline bolus through CVP (listen to Doppler) Rapid saline bolus through CVP (listen to Doppler) PAC's (imply atrial stimulation) PAC's (imply atrial stimulation) PVC's (imply ventricular stimulation) PVC's (imply ventricular stimulation) Right ventricular pressure wave on CVP (Pull catheter back into right Right ventricular pressure wave on CVP (Pull catheter back into right

atrium.) atrium.) Chest X-ray Chest X-ray Biphasic P-wave on intracardiac electrocardiogram Biphasic P-wave on intracardiac electrocardiogram

Biphasic P-wave on intracardiac electrocardiogramBiphasic P-wave on intracardiac electrocardiogram

Intraoperative Concerns Intraoperative Concerns Premedication? Premedication?

Thorough pre-op interview to allay anxiety. Thorough pre-op interview to allay anxiety. None ("light" sedation with benzodiazepine if at all). None ("light" sedation with benzodiazepine if at all).

Avoid narcotics pre-op (respiratory depression, nausea and vomiting). Avoid narcotics pre-op (respiratory depression, nausea and vomiting). Monitoring Checklist Monitoring Checklist -- use "routine" monitors as reminders:-- use "routine" monitors as reminders:

Stethoscope -- esophageal Stethoscope -- esophageal Precordial Doppler -- to detect venous air emboli (VAE) Precordial Doppler -- to detect venous air emboli (VAE)

EKG -- ST segments EKG -- ST segments Non-invasive blood pressure Non-invasive blood pressure

Radial A-line -- BP, paO2, paCO2 (=25-30), H&H, K+ Radial A-line -- BP, paO2, paCO2 (=25-30), H&H, K+ CVP -- follow volume status, aspirate VAE CVP -- follow volume status, aspirate VAE

Temperature -- esophageal probe Temperature -- esophageal probe Blood warmer, Bird or Bear humidifer Blood warmer, Bird or Bear humidifer Warming/cooling blanket Warming/cooling blanket

Oxygen monitor (+ volume monitor and PIP) Oxygen monitor (+ volume monitor and PIP) Adjust ventilation according to paCO2 Adjust ventilation according to paCO2

Pulse oximeter Pulse oximeter End-tidal CO2 (and infrared gas analyzer) End-tidal CO2 (and infrared gas analyzer)

Useful to trend paCO2 (End-tidal CO2 < paCO2) Useful to trend paCO2 (End-tidal CO2 < paCO2) Detecting VAE (decreased end-tidal CO2, increased ET N2) Detecting VAE (decreased end-tidal CO2, increased ET N2)

RRestraints (+ twitch monitor -- muscle relaxants)estraints (+ twitch monitor -- muscle relaxants) IIntake and outputntake and output

Foley catheter (furosemide, mannitol) Foley catheter (furosemide, mannitol) Maintain even I&O (Don't "run em' dry.") Maintain even I&O (Don't "run em' dry.") Avoid dextrose-containing solutions in IV's Avoid dextrose-containing solutions in IV's

PPosition injuriesosition injuries Ulnar or sciatic nerves (in sitting position) Ulnar or sciatic nerves (in sitting position) Neck not hyper-flexed or -extended Neck not hyper-flexed or -extended

Special monitors Special monitors 1. Facial nerve (C.N. VII) function 1. Facial nerve (C.N. VII) function Neurosurgeon directly stimulates facial nerve in operative field. Neurosurgeon directly stimulates facial nerve in operative field. Facial muscle movement is observed: Facial muscle movement is observed:

Directly by the anesthesiologist (under drapes) Directly by the anesthesiologist (under drapes) Indirectly by electrode and monitor Indirectly by electrode and monitor

Anesthetic implication -- neuromuscular blockade must wear off or be Anesthetic implication -- neuromuscular blockade must wear off or be reversed at time of stimulation.reversed at time of stimulation.

2. Brainstem auditory evoked potentials or responses2. Brainstem auditory evoked potentials or responses (BAEP's or BAER’s)(BAEP's or BAER’s) Specialized form of EEG monitoring Specialized form of EEG monitoring

Background EEG activity is electronically subtracted out. Background EEG activity is electronically subtracted out. The EEG waveform evoked by auditory stimulus (clicking in ear) The EEG waveform evoked by auditory stimulus (clicking in ear)

remains. remains.

Shape of a typical BAEP = seven peaks1

– Latency = time to first peak (usually 2 msec)

– Amplitude = height of the peaks

c. The seven peaks of the BAEP are believed to correspond to passage of a stimulus through "generators" in the auditory nerve, brainstem and cortex.

The seven peaks of the BAEP The seven peaks of the BAEP

WAVE PURPORTED GENERATOR

I Extracranial auditory nerve

II Intracranial auditory nerve and/or cochlear nucleus

III Superior olive

IV Lateral lemniscus

V Inferior colliculus

VI Thalamus

VII Thalamocortical radiation

BAEPBAEP

What do we look for during surgery? What do we look for during surgery? Mainly two things: Mainly two things:

Increase in latency (> 10%) Increase in latency (> 10%) Decrease in amplitude (<50%) Decrease in amplitude (<50%)

These two changes could be indicative of impending These two changes could be indicative of impending injury or ischemia in the BAEP pathway. injury or ischemia in the BAEP pathway.

BAER's are barely affected by anesthetics: BAER's are barely affected by anesthetics: No anesthetic drug produces a change in BAER’s that No anesthetic drug produces a change in BAER’s that

could be mistaken for a surgically induced change.could be mistaken for a surgically induced change. 2) Etomidate decreases amplitude and increases latency (but 2) Etomidate decreases amplitude and increases latency (but

this is not clinically significant). this is not clinically significant).

Induction Induction -- "typical" anesthetic regimen for intracranial procedures,-- "typical" anesthetic regimen for intracranial procedures, assuming airway assuming airway meets good criteria (i.e. Mallampati classification):meets good criteria (i.e. Mallampati classification):

1. Method: "Modified" rapid sequence induction and intubation1. Method: "Modified" rapid sequence induction and intubation (with cricoid pressure)(with cricoid pressure) Preoxygenate and denitrogenate (100% O2 by mask with head in good "sniffing" Preoxygenate and denitrogenate (100% O2 by mask with head in good "sniffing"

position) position) Cricoid pressure (N&V with increased ICP) Cricoid pressure (N&V with increased ICP) Hyperventilate to decrease paCO2 prior to intubation Hyperventilate to decrease paCO2 prior to intubation

Typical induction agents Typical induction agents Propofol, etomidate, or thiopental Propofol, etomidate, or thiopental

suitable I.V. induction agents suitable I.V. induction agents Fentanyl or sufentanil Fentanyl or sufentanil

– – as narcotic analgesics to supplement as narcotic analgesics to supplement Lidocaine IV – to blunt hypertensive and ICP response to intubation d. Lidocaine IV – to blunt hypertensive and ICP response to intubation d. Neuromuscular junction blockers –rocuronium, vecuronium, or succinylcholine (with Neuromuscular junction blockers –rocuronium, vecuronium, or succinylcholine (with

prior defasciculating dose of non-depolarizing NMJ blocker)prior defasciculating dose of non-depolarizing NMJ blocker)

MaintenanceMaintenance 1. Reasonable Maintenance Regimens for Intracranial Neuroanesthesia (going from 1. Reasonable Maintenance Regimens for Intracranial Neuroanesthesia (going from

routine to desperate).routine to desperate).a. N2O + isoflurane (½%) + fentanyla. N2O + isoflurane (½%) + fentanyl N2O = the first agent to go if there’s brain swelling or venous air emboli or ischemia N2O = the first agent to go if there’s brain swelling or venous air emboli or ischemia

danger (i.e. aneurysm or head trauma) danger (i.e. aneurysm or head trauma) MAC equivalents of sevoflurane or desflurane might also be substituted MAC equivalents of sevoflurane or desflurane might also be substituted

for isoflurane. for isoflurane. Sufentanil could be substituted for fentanyl. Sufentanil could be substituted for fentanyl.

b. Isoflurane (1%) + fentanylb. Isoflurane (1%) + fentanylc. Isoflurane (½%) + propofol + fentanylc. Isoflurane (½%) + propofol + fentanyl ! Volatile agents are next to go if high ICP or brain swelling! Volatile agents are next to go if high ICP or brain swelling Total IV anesthetic: Propofol + fentanyl Total IV anesthetic: Propofol + fentanyl Barbiturate coma -- for intractible brain swelling or cerebral Barbiturate coma -- for intractible brain swelling or cerebral protection during aneurysm clipping (titrated to EEG burst suppression):protection during aneurysm clipping (titrated to EEG burst suppression):

Thiopental Thiopental Pentobarbital Pentobarbital

Non-depolarizing neuromuscular junction blocker Non-depolarizing neuromuscular junction blocker (must wear off or be reversible by time of CN VII (must wear off or be reversible by time of CN VII testing). testing).

Vecuronium Vecuronium Rocuronium Rocuronium Pancuronium – increases HR Pancuronium – increases HR Cis-atracurium Cis-atracurium

Additional maneuvers to decrease ICP Additional maneuvers to decrease ICP

Intraoperative Complications Intraoperative Complications -- "Emergencies in Neuroanesthesia"-- "Emergencies in Neuroanesthesia" Intraoperative Air Embolus Intraoperative Air Embolus

What should I do immediately?What should I do immediately? Tell the surgeon, who should flood the field. Tell the surgeon, who should flood the field. Discontinue N2O and give 100% O2 Discontinue N2O and give 100% O2 Aspirate air from the CVP line Aspirate air from the CVP line Light neck compression Light neck compression Call for help Call for help Supportive measures (i.e., treat hypotension, arrhythmias) Supportive measures (i.e., treat hypotension, arrhythmias) Try to position patient for CPR Try to position patient for CPR

What else can I do? Other considerations: What else can I do? Other considerations: Dopamine or dobutamine? (Suggested to increase right ventricular Dopamine or dobutamine? (Suggested to increase right ventricular

contractility) contractility) Raise CVP by fluid loading, not PEEP. PEEP would raise Raise CVP by fluid loading, not PEEP. PEEP would raise

CVP, but at the risk of sending a paradoxical (arterial) air embolus CVP, but at the risk of sending a paradoxical (arterial) air embolus through a probe-patent foramen ovale.through a probe-patent foramen ovale.

Avoid the Valsalva maneuver:This increases CVP, but: Avoid the Valsalva maneuver:This increases CVP, but: could cause paradoxical air emboluscould cause paradoxical air embolus causes severe hypotension causes severe hypotension

"Tight Brain" "Tight Brain" -- Think through things we can do to decrease-- Think through things we can do to decrease intracranial intracranial volume and ICP.volume and ICP.

Airway disaster? In any anesthetic emergency, the first things to think of are: Airway disaster? In any anesthetic emergency, the first things to think of are: HYPOXIA & HYPERCARBIA!HYPOXIA & HYPERCARBIA! (Is this a respiratory disaster?) (Is this a respiratory disaster?)

Furosemide and mannitol? Furosemide and mannitol? Dexamethasone? Dexamethasone? Open the spinal drain or insert a ventriculostomy? Open the spinal drain or insert a ventriculostomy? Can I hyperventilate more (to paCO2 of 25)? Can I hyperventilate more (to paCO2 of 25)? Anesthetic choice? Anesthetic choice?

Muscle relaxant? Muscle relaxant? DC N2O, switch to 100% O2? DC N2O, switch to 100% O2? TIVA (total IV anesthetic) technique? TIVA (total IV anesthetic) technique? Barbiturate coma – as a last resort Barbiturate coma – as a last resort

Improve venous return? Improve venous return? Reverse Trendelenberg position? Elevate head of bed? Reverse Trendelenberg position? Elevate head of bed? Reposition the head? Is there venous occlusion secondary to positioning? Reposition the head? Is there venous occlusion secondary to positioning?

Sudden Cardiovascular Changes Sudden Cardiovascular Changes a. With any sudden change in vital signs (hyper- or hypotension, a. With any sudden change in vital signs (hyper- or hypotension, tachy- or bradycardia, cardiac arrhythmias, etc.), the first three things to tachy- or bradycardia, cardiac arrhythmias, etc.), the first three things to

think of in this situation are:think of in this situation are: HYPOXIA & HYPERCARBIA! (Always first) HYPOXIA & HYPERCARBIA! (Always first) SEVERE AIR EMBOLUS (Close second) SEVERE AIR EMBOLUS (Close second) Artifact - has BP transducer or table moved up or down? Artifact - has BP transducer or table moved up or down? b. Bradycardia b. Bradycardia 1)With hypertension 1)With hypertension

a) Most likely cause = Cushing response 2ndary to: a) Most likely cause = Cushing response 2ndary to: ICP (closed skull) ICP (closed skull) surgical retraction (open skull) surgical retraction (open skull)

brain stem stimulation brain stem stimulation traction on trigeminal nerve (CN V) traction on trigeminal nerve (CN V)

Cushing Response Cushing Response

Potential treatments: Potential treatments: Tell surgeon. Tell surgeon. Propofol or pentothal bolus Propofol or pentothal bolus Deepen anesthesia Deepen anesthesia

Other possible causes: Other possible causes: Impending brain stem herniation Impending brain stem herniation

(turn off spinal drain?) (turn off spinal drain?) Inadvertent phenylephrine bolus Inadvertent phenylephrine bolus

Bradycardia With hypotension Bradycardia With hypotension Most likely cause = vagal stimulation Most likely cause = vagal stimulation Potential treatments: Potential treatments:

Tell surgeon. Tell surgeon. Ephedrine Ephedrine Atropine (or glycopyrrolate) Atropine (or glycopyrrolate)

Tachycardia Tachycardia With hypertension With hypertension

Most likely causes = light anesthesia or sympathetic Most likely causes = light anesthesia or sympathetic stimulation stimulation

Another cause = inadvertent Ephedrine bolus Another cause = inadvertent Ephedrine bolus Potential treatments = deepen anesthesia (1st), Potential treatments = deepen anesthesia (1st),

antihypertensives (2nd)antihypertensives (2nd) With hypotension With hypotension

Most likely cause = hypovolemia Most likely cause = hypovolemia Another cause = hemodynamic instability Another cause = hemodynamic instability due to sitting positiondue to sitting position Potential treatments: Potential treatments:

Replace I&O cc per cc Replace I&O cc per cc Phenylephrine Phenylephrine

Premature Ventricular Contractions (PVC's) Premature Ventricular Contractions (PVC's)

POTENTIAL CAUSES P O TE N TIA L TR E A TM E N TS ! Hypoxia Oxygen ! CVP catheter Pull back catheter

in right ventricle

! Brain stem stimulation Tell surgeon ! Hypokalemia Potassium

(due to diuresis)

! Hypomagnesemia Magnesium ! Intrinsic disease Lidocaine

Emergence. Emergence. Hypertension is frequently a problem. Hypertension is frequently a problem. Avoid "coughing and bucking" while head is Avoid "coughing and bucking" while head is

secured. Two agents to treat coughing and secured. Two agents to treat coughing and bucking are: bucking are:

Propofol Propofol Lidocaine Lidocaine

It's desirable for the patient to awaken quickly so It's desirable for the patient to awaken quickly so neurosurgeons can obtain a neurologic neurosurgeons can obtain a neurologic assessment. assessment.

Postoperative Concerns.

• Many potential postoperative problems are related to the location of the surgery on or near the brain stem.

• Cardiovascular centers - hypertension

• Respiratory centers - respiratory depression, apnea

• Lower cranial nerves:

VI Abducens Disconjugate gaze VII Facial Facial muscle paralysis VIII Acoustic Hearing loss IX Glosspharyngeal loss of gag reflex X Vagus V oca l cord para lysis