Anesthetic Anesthetic management of management of

Cerebral AneurysmCerebral Aneurysm

By Dr. Veena BoswalBy Dr. Veena BoswalUnder the guidance ofUnder the guidance of

Dr. Poonam Kalra Dr. Poonam Kalra

DefinitionsDefinitions

A A cerebralcerebral aneurysmaneurysm is a is a cerebrovascular disorder in which cerebrovascular disorder in which weakness in the wall of a cerebral artery weakness in the wall of a cerebral artery or vein causes a localized dilatation or or vein causes a localized dilatation or ballooning of the blood vesselballooning of the blood vessel

A common location of cerebral A common location of cerebral aneurysms is on the arteries at the base aneurysms is on the arteries at the base of the brain, known as the of the brain, known as the Circle of Circle of WillisWillis

AnatomyAnatomy The The Circle of WillisCircle of Willis is a circle of arteries is a circle of arteries

that supply blood to the brain that supply blood to the brain ComponentsComponents1.1. Anterior cerebral artery (left and right) Anterior cerebral artery (left and right) 2.2. Anterior communicating artery Anterior communicating artery 3.3. Internal carotid artery (left and right) Internal carotid artery (left and right) 4.4. Posterior cerebral artery (left and right) Posterior cerebral artery (left and right) 5.5. Posterior communicating artery (left and Posterior communicating artery (left and

right) right) The basilar artery and middle cerebral The basilar artery and middle cerebral

arteries, though they supply the brain, are arteries, though they supply the brain, are not considered part of the circlenot considered part of the circle

EpidemiologyEpidemiology Exact incidence is unclear but probably Exact incidence is unclear but probably

about 4%. about 4%. An annual incidence of rupture is about 15-An annual incidence of rupture is about 15-

20 per 100,000 population20 per 100,000 population AgeAge : At any age but peaks at 40-60 years : At any age but peaks at 40-60 years Sex Sex : Male to Female 2 : 3 but more males : Male to Female 2 : 3 but more males

below 40 and more females after 40years below 40 and more females after 40years SitesSites : 30% ICA : 30% ICA 40% ACA( Anterior Communicating)40% ACA( Anterior Communicating) 20% MCA20% MCA 10% Vertebro-basilar systems10% Vertebro-basilar systems Rupture Rupture : 90% <12mm, 5% in 12-15mm, : 90% <12mm, 5% in 12-15mm,

5% >15mm5% >15mm

AetiologyAetiology It had been thought to be a congenital disease but is It had been thought to be a congenital disease but is

now thought to be now thought to be primarily acquiredprimarily acquired (although (although there is a congenital component in some cases) there is a congenital component in some cases)

Most are of the Most are of the saccular or berry aneurysmssaccular or berry aneurysms and this type of aneurysm is unique to the cerebral and this type of aneurysm is unique to the cerebral circulationcirculation

Rupture is thought to relate to the size of the lesion. Rupture is thought to relate to the size of the lesion. This clearly is due to This clearly is due to Laplace's Law T = 2PRLaplace's Law T = 2PR and and the fact that the wall also becomes thinner as the the fact that the wall also becomes thinner as the aneurysm enlargesaneurysm enlarges

The lesions almost always occur at the The lesions almost always occur at the bifurcation bifurcation of vesselsof vessels. It is thought that the process starts with . It is thought that the process starts with degeneration of the internal elastic membrane at degeneration of the internal elastic membrane at the apex of a bifurcation. This is the the apex of a bifurcation. This is the site of site of the maximum hemodynamic stressthe maximum hemodynamic stress

The pressure within the aneurysm is at systemic The pressure within the aneurysm is at systemic levels and thus rupture is most likely to occur at levels and thus rupture is most likely to occur at moments of raised BP. The larger the moments of raised BP. The larger the aneurysm the greater the likelihood of rupture, aneurysm the greater the likelihood of rupture, however most rupture when they are however most rupture when they are <12mm<12mm

PresentationPresentation The vast majority present with The vast majority present with Sub Arachnoid Sub Arachnoid

HaemorrhageHaemorrhage Occasionally with Occasionally with pressure symptomspressure symptoms related related

to direct pressure on nerves, eg. 3, 4, or 6 nerve to direct pressure on nerves, eg. 3, 4, or 6 nerve palsiespalsies

Many are now presenting with Many are now presenting with incidental incidental findingsfindings on MRI or CT scans on MRI or CT scans

Those patients who present with a SAH will in fact Those patients who present with a SAH will in fact have had some type of symptoms in the few days have had some type of symptoms in the few days prior to the major bleedprior to the major bleed

Minor bleeds precede the major haemorrhage in Minor bleeds precede the major haemorrhage in 50% of patients. The patients may have 50% of patients. The patients may have Hypertension either as the cause or the result Hypertension either as the cause or the result of the bleed. Brainstem ischaemia is thought of the bleed. Brainstem ischaemia is thought to be the cause of the secondary form to be the cause of the secondary form

Signs and SymptomsSigns and Symptoms

The Signs and Symptoms of SAH The Signs and Symptoms of SAH are are due todue to

1.1. Raised ICPRaised ICP2.2. Damage due to intra-cerebral bleedsDamage due to intra-cerebral bleeds3.3. Regional vasospasmRegional vasospasm4.4. Generalised vasospasmGeneralised vasospasm

Continued..Continued..

The Signs and SymptomsThe Signs and Symptoms are : are :

1)1) Result of Initial RuptureResult of Initial Rupture: There is an initial abrupt rise in ICP that : There is an initial abrupt rise in ICP that produces a severe headache ± loss of consciousness. Blood in the produces a severe headache ± loss of consciousness. Blood in the CSF produces meningism (photophobia, neck stiffness, and headache)CSF produces meningism (photophobia, neck stiffness, and headache)

2)2) Focal signsFocal signs: The most commonly occurs 7 days later from : The most commonly occurs 7 days later from vasospasm, but if occurring initially may be due to the direct effects vasospasm, but if occurring initially may be due to the direct effects of the jet of blood, intracerebral bleeding, or from herniationof the jet of blood, intracerebral bleeding, or from herniation

3)3) HydrocephalusHydrocephalus: Common, usually due to impaired CSF passage : Common, usually due to impaired CSF passage through the basal cisterns. Occasionally large basilar aneurysms through the basal cisterns. Occasionally large basilar aneurysms may produce IV ventricular obstruction and hydrocephalus may produce IV ventricular obstruction and hydrocephalus

Classification SystemsClassification Systems Botterell’s Clinical GradingBotterell’s Clinical Grading

GradeGrade

1)1)

2)2)

3)3)

4)4)

5)5)

CriteriaCriteria

Conscious with or without Meningeal Conscious with or without Meningeal SignsSigns

Drowsy without significant Neurological Drowsy without significant Neurological DeficitDeficit

Drowsy with Neurological Deficit and Drowsy with Neurological Deficit and probable cerebral clotprobable cerebral clot

Major Neurological Deficit present.Major Neurological Deficit present.

Moribund with Failing Vital Centers and Moribund with Failing Vital Centers and Extensor Rigidity.Extensor Rigidity.

Modified Hunt and Hess’s Clinical GradesModified Hunt and Hess’s Clinical Grades

Grade Grade

0)0)

1)1)

2)2)

3)3)

4)4)

5)5)

CriteriaCriteria

Unruptured AneurysmUnruptured Aneurysm

Asymptomatic or have mild headache or Asymptomatic or have mild headache or neck stiffnessneck stiffness

Headache and neck stiffness but no Headache and neck stiffness but no neurological abnormalities other than neurological abnormalities other than cranial nerve palsiescranial nerve palsies

Drowsy, confused or have mild focal Drowsy, confused or have mild focal deficitsdeficits

Stuporosed and have moderate or severe Stuporosed and have moderate or severe hemiparesishemiparesis

Comatosed, non-responsive, and Comatosed, non-responsive, and moribund with decerebrate rigiditymoribund with decerebrate rigidity

World Federation of Neurological World Federation of Neurological

Surgeons GradingSurgeons Grading

WNFS GradeWNFS Grade

1)1)

2)2)

3)3)

4)4)

5)5)

GCS ScoreGCS Score

1515

14 – 1314 – 13

14 – 1314 – 13

12 – 712 – 7

6 - 36 - 3

Motor DeficitMotor Deficit

AbsentAbsent

AbsentAbsent

PresentPresent

Present or Present or AbsentAbsent

Present or Present or AbsentAbsent

Diagnosis of SAHDiagnosis of SAH

This is usually on This is usually on CT scanCT scan (SAH or (SAH or haematoma mainly but you may be haematoma mainly but you may be able to see the aneurysm on a plain able to see the aneurysm on a plain CTCT

MRI or CT angiographyMRI or CT angiography will have a will have a much better detection rate much better detection rate

Ultimately Ultimately Cerebral AngiographyCerebral Angiography will be done to determine whether will be done to determine whether there is an aneurysm and how it there is an aneurysm and how it should best be treatedshould best be treated

ManagementManagement An angiogram is done as soon as possible to allow rational An angiogram is done as soon as possible to allow rational

management decisions to be made (aneurysms are not management decisions to be made (aneurysms are not always demonstrated in presumed subarachnoid bleeds always demonstrated in presumed subarachnoid bleeds and the absence of an aneurysm obviously has a major and the absence of an aneurysm obviously has a major impact on the patient’s management)impact on the patient’s management)

As the As the patients who have survived the initial bleedpatients who have survived the initial bleed are at risk of re-bleeding it would seem sensible to repair are at risk of re-bleeding it would seem sensible to repair the aneurysm as soon as possible. Almost all the aneurysm as soon as possible. Almost all neurosurgeons will now operate neurosurgeons will now operate as soon as is practicalas soon as is practical except in Grade IV and V patientsexcept in Grade IV and V patients

Those with severe vasospasmThose with severe vasospasm unresponsive to unresponsive to pharmacologic treatment may also be clipped to allow pharmacologic treatment may also be clipped to allow the use of more marked induced hypertensionthe use of more marked induced hypertension

Obviously the patient who has a Obviously the patient who has a major intracranial bleed major intracranial bleed with mass effects or obstructive hydrocephaluswith mass effects or obstructive hydrocephalus (blockage of the arachnoid villi or the basal cisterns) will (blockage of the arachnoid villi or the basal cisterns) will require urgent surgery. In these cases the surgery may require urgent surgery. In these cases the surgery may be restricted to relieving these problems rather than the be restricted to relieving these problems rather than the definitive repairdefinitive repair

In case Angiography (and thus definitive In case Angiography (and thus definitive diagnosis of Aneurysm) is delayed due to diagnosis of Aneurysm) is delayed due to any reasons, theany reasons, the intervening period is a intervening period is a dangerous one with 20% suffering a re-dangerous one with 20% suffering a re-bleed, with a >60% mortalitybleed, with a >60% mortality

The goals of this periodThe goals of this period1.1. Prevent re-bleedsPrevent re-bleeds2.2. Prevent or treat vasospasmPrevent or treat vasospasm3.3. Detect hydrocephalusDetect hydrocephalus4.4. Avoid respiratory problemsAvoid respiratory problems5.5. Optimise the general medical state of Optimise the general medical state of

the patient the patient

The patient is confined to bed and they are to The patient is confined to bed and they are to avoid things that may increase their BP eg avoid things that may increase their BP eg straining at stool (given laxatives) straining at stool (given laxatives)

Their BP control is difficult and depends on Their BP control is difficult and depends on their clinical status. As a rule their clinical status. As a rule hypertension hypertension should be controlledshould be controlled however however if they have if they have vasospasm a common treatment is to raise vasospasm a common treatment is to raise their BPtheir BP

If there is no obvious vasospasm then the BP is If there is no obvious vasospasm then the BP is controlled on empirical grounds to about 160 controlled on empirical grounds to about 160 systolic and 100 diastolicsystolic and 100 diastolic

Epsilon aminocaproic acid may be used to Epsilon aminocaproic acid may be used to prevent the clot around the aneurysm from prevent the clot around the aneurysm from being dissolved. In general it has not proved being dissolved. In general it has not proved usefuluseful

Generally the patient’s fluid status needs to be Generally the patient’s fluid status needs to be very carefully assessed and it may be necessary very carefully assessed and it may be necessary to measure the CVP, of course the U/O and to measure the CVP, of course the U/O and fluid balance should be carefully measuredfluid balance should be carefully measured

The prolonged bed rest predisposes to The prolonged bed rest predisposes to respiratory problems and these should be respiratory problems and these should be aggressively treatedaggressively treated

Vasospasm Vasospasm

ItIt is one of the worst problems in this condition is one of the worst problems in this condition causing ischaemia and subsequent cerebral causing ischaemia and subsequent cerebral oedema that further compromises the cerebral oedema that further compromises the cerebral circulationcirculation

Radiological evidence of large vessel Radiological evidence of large vessel vasoconstriction is present in about 60-80% of vasoconstriction is present in about 60-80% of patientspatients

But is Clinically and hemodynamically significant But is Clinically and hemodynamically significant in 33% of patientsin 33% of patients

The peak incidence is around 7The peak incidence is around 7thth day from initial day from initial event.event.

The exact mechanism for it is unclear but appears The exact mechanism for it is unclear but appears to be due to the presence of to be due to the presence of blood breakdown blood breakdown productsproducts. FFA derivatives such as the . FFA derivatives such as the prostaglandins and leukotrienes, prostaglandins and leukotrienes, oxyhaemoglobinoxyhaemoglobin and the and the oxygen radicals.oxygen radicals.

Clinical ManifestationsClinical Manifestations – Are due to – Are due to Cerebral Ischemia:Cerebral Ischemia:

1.1. Decrease in Level of ConsciousnessDecrease in Level of Consciousness2.2. New Onset of Focal SignsNew Onset of Focal Signs3.3. MutismMutism

Diagnosis Diagnosis : :

1.1. Confirmed by AngiographyConfirmed by Angiography2.2. Non Invasive TCD USG may be used to Non Invasive TCD USG may be used to

demonstrate increased cerebral artery demonstrate increased cerebral artery Flow VelocitiesFlow Velocities

Treatment :Treatment :

1.1. Pharmacological :Pharmacological : Calcium Channel Blockers Calcium Channel Blockers – Nimodipine is used. Beneficial effects occur – Nimodipine is used. Beneficial effects occur either at Distal Vessel Site or at a Cellular leveleither at Distal Vessel Site or at a Cellular level

2.2. Surgical :Surgical : Early Surgery (within 48 hrs of SAH) Early Surgery (within 48 hrs of SAH) with extensive irrigation of cisterns, removes with extensive irrigation of cisterns, removes the causative agent (blood byproducts) of the causative agent (blood byproducts) of vasospasm. vasospasm.

Intraoperative cisternal injection of Papaverine Intraoperative cisternal injection of Papaverine may be done to reduce vasospasmmay be done to reduce vasospasm

3.3. Reduction of ICP : Reduction of ICP : To improve Cerebral To improve Cerebral Perfusion and alleviate the ischemic state, Perfusion and alleviate the ischemic state, reduction of ICP may be tried in patients with reduction of ICP may be tried in patients with elevated ICPelevated ICP

4.4. Triple H TherapyTriple H Therapy : : Hypervolaemia, Haemodilution, and Hypervolaemia, Haemodilution, and HypertensionHypertension

HypervolaemiaHypervolaemia – Increase CVP to 10 mm Hg or PAWP – Increase CVP to 10 mm Hg or PAWP to 12 to 20 mm Hg. Colloids or Crystalloids may be used. to 12 to 20 mm Hg. Colloids or Crystalloids may be used. Hetastarch and Dextrans should be used sparingly due Hetastarch and Dextrans should be used sparingly due to potential of coagulopathyto potential of coagulopathy

HypertensionHypertension – To increase CPP, Vasopressors – To increase CPP, Vasopressors (dopamine, dobutamine or phenylephrine) may be used (dopamine, dobutamine or phenylephrine) may be used to titrate the blood pressure level till reversal of to titrate the blood pressure level till reversal of symptoms or to a maximum of SBP of 160 -200 mm Hg symptoms or to a maximum of SBP of 160 -200 mm Hg in aneurysm clipped patients and upto 120 – 150 mm Hg in aneurysm clipped patients and upto 120 – 150 mm Hg in patients with non clipped aneurysms. The BP is in patients with non clipped aneurysms. The BP is maintained until vasospasm resolves (usually in 3 to 7 maintained until vasospasm resolves (usually in 3 to 7 days)days)

HemodilutionHemodilution – Based on correlation of hematocrit and – Based on correlation of hematocrit and blood viscosity. The cerebral blood flow improves with blood viscosity. The cerebral blood flow improves with reduction of blood viscosity. Hematocrit of 33% provides reduction of blood viscosity. Hematocrit of 33% provides optimal balance between viscosity and oxygen carrying optimal balance between viscosity and oxygen carrying capacity of bloodcapacity of blood

Intracranial PressureIntracranial Pressure1.1. ICP rises rapidly after SAH. May also increase from ICP rises rapidly after SAH. May also increase from

mass effect of clot, cerebral edema or mass effect of clot, cerebral edema or hydrocephalus due to blocked aqueduct or hydrocephalus due to blocked aqueduct or communicating hydrocephalus due to arachnoidal communicating hydrocephalus due to arachnoidal adhesions from extravasated blood that interferes adhesions from extravasated blood that interferes with reabsorption of CSFwith reabsorption of CSF

2.2. Vasospasm can also exacerbate ICP increase Vasospasm can also exacerbate ICP increase because the reduction in CBF is accompanied by because the reduction in CBF is accompanied by vasodilatation of distal vesselsvasodilatation of distal vessels

3.3. ICP correlates well with clinical grade. Normal in ICP correlates well with clinical grade. Normal in Grade 1 or 2 and raised in grade 4 or 5 (Botterell’s Grade 1 or 2 and raised in grade 4 or 5 (Botterell’s grades)grades)

4.4. Never normalize ICP too rapidly because it leads to a Never normalize ICP too rapidly because it leads to a rapid increase in Transmural Pressure across the rapid increase in Transmural Pressure across the aneurysm wall, thus further increasing chances of aneurysm wall, thus further increasing chances of bleedingbleeding

Impairment of AutoregulationImpairment of Autoregulation: These : These patients may have an impaired ability to patients may have an impaired ability to autoregulate CBF and the Degree of impairment autoregulate CBF and the Degree of impairment correlates directly to Clinical Grade. Thus it is correlates directly to Clinical Grade. Thus it is advisable not to allow the Perfusion pressure to advisable not to allow the Perfusion pressure to decrease below the lower limit of autoregulation decrease below the lower limit of autoregulation perioperatively specially in Gradewise poor perioperatively specially in Gradewise poor patients. Thus it presents a relative patients. Thus it presents a relative contraindication to Induced Hypotension in these contraindication to Induced Hypotension in these patientspatients

Reactivity to COReactivity to CO22: Cerebrovascular response : Cerebrovascular response to Hyperventilation is generally preserved after to Hyperventilation is generally preserved after SAH . Thus hyperventilation remains effective in SAH . Thus hyperventilation remains effective in reducing CBF during perioperative management reducing CBF during perioperative management in these patientsin these patients

Pre-operative Pre-operative AssessmentAssessment These patients need very careful pre-op assessment These patients need very careful pre-op assessment

1.1. CVSCVS : Baseline BP (to give some idea of the safe level of : Baseline BP (to give some idea of the safe level of hypotension)hypotension)

Fluid Status (the fluid balance of these patients is very Fluid Status (the fluid balance of these patients is very important, they should not be overloaded otherwise they important, they should not be overloaded otherwise they may develop CCF but if they are dry, cerebral circulation may develop CCF but if they are dry, cerebral circulation maybe compromised and vasospasm, if present, may be maybe compromised and vasospasm, if present, may be rendered haemodynamically significant. rendered haemodynamically significant.

If hyponatremia is allowed to develop cerebral oedema may If hyponatremia is allowed to develop cerebral oedema may resultresult

2.2. RESPRESP: Prolonged bed rest runs the risk of atelectasis and : Prolonged bed rest runs the risk of atelectasis and pneumonia if this is present, it should be cleared to the pneumonia if this is present, it should be cleared to the patient prior to surgery. Patients with COPD may also need a patient prior to surgery. Patients with COPD may also need a higher FiOhigher FiO22 intra-op intra-op

3.3. CNSCNS: A simple pre-op assessment will help in the rapid post-: A simple pre-op assessment will help in the rapid post-op assessment of the patient. Pupil size, gross motor op assessment of the patient. Pupil size, gross motor weakness, presence of aphasia and any specific cranial nerve weakness, presence of aphasia and any specific cranial nerve signs are sufficientsigns are sufficient

4.4. GENGEN: As for any pre-op examination: As for any pre-op examination

Pre-op TestsPre-op Tests1.1. Blood BiochemistryBlood Biochemistry: : Electrolyte abnormalitiesElectrolyte abnormalities are are

common and should be corrected pre-op. common and should be corrected pre-op. Renal Renal functionsfunctions should be assessed as this be a consideration in should be assessed as this be a consideration in reducing the BP if induced hypotension is used. reducing the BP if induced hypotension is used. Blood SugarBlood Sugar should be normalised as hyperglycaemia has been shown should be normalised as hyperglycaemia has been shown to worsen neurological deficits in the presence of cerebral to worsen neurological deficits in the presence of cerebral ischaemiaischaemia

2.2. CBCCBC: Anaemia should be corrected pre-op: Anaemia should be corrected pre-op3.3. CoagsCoags: INR/APTT: INR/APTT

4.4. ECG:ECG: This should be done on the day prior to surgery as these This should be done on the day prior to surgery as these patients have a high incidence of ECG abnormalities and these patients have a high incidence of ECG abnormalities and these are changeable over the time that surgery is delayedare changeable over the time that surgery is delayed

5.5. CXRCXR: As a general assessment of RESP and CVS pathology: As a general assessment of RESP and CVS pathology

6.6. EchoEcho: Patients with questionable cardiac function should have : Patients with questionable cardiac function should have a pre-operative echocardiography a pre-operative echocardiography

7.7. Other tests may be indicated in specific situationsOther tests may be indicated in specific situations

Pre-MedicationPre-Medication Adequate Explanation is the Best Premedication.Adequate Explanation is the Best Premedication. Aim of pre-med is to alleviate anxiety to prevent Aim of pre-med is to alleviate anxiety to prevent

shooting of blood pressureshooting of blood pressure In general, pre-med is best omitted to allow In general, pre-med is best omitted to allow

accurate assessment of patient’s pre-op accurate assessment of patient’s pre-op neurologic statusneurologic status

In patients with Elevated ICP pre-medication In patients with Elevated ICP pre-medication with barbiturates or narcotic should be used with barbiturates or narcotic should be used judiciously to prevent respiratory depression judiciously to prevent respiratory depression and hence hypercapnia induced increases in and hence hypercapnia induced increases in CBFCBF

In very anxious, grade 1 SAH patients, titrated In very anxious, grade 1 SAH patients, titrated doses of sedatives might be used till anxiety is doses of sedatives might be used till anxiety is relievedrelieved

Adequate amount of blood should be available Adequate amount of blood should be available

Radiological Management Radiological Management of Aneurysmsof Aneurysms

Angiographic Coiling of an AneurysmAngiographic Coiling of an Aneurysm Usually done under GAUsually done under GA Coiling works by placing extremely coiled material Coiling works by placing extremely coiled material

inside the Aneurysm. The material coating the coils is inside the Aneurysm. The material coating the coils is extremely thrombogenic and the aim is for the extremely thrombogenic and the aim is for the aneurysm to thrombose and a new intima to grow aneurysm to thrombose and a new intima to grow over the inlet of the aneurysm. A variable number of over the inlet of the aneurysm. A variable number of the coils are placed until the aneurysm is full of themthe coils are placed until the aneurysm is full of them

The usual anaesthesia is similar that for operative The usual anaesthesia is similar that for operative neurosurgery with relaxation, intubation and neurosurgery with relaxation, intubation and ventilationventilation

The patients will develop a diuresis from all the The patients will develop a diuresis from all the contrast material and should be catheterised after contrast material and should be catheterised after inductioninduction

RisksRisks of Angiographic Coiling: of Angiographic Coiling:1.1. The aneurysm may rupture with the The aneurysm may rupture with the

angiographic manipulation angiographic manipulation 2.2. Secondly part of the coil could embolise out of Secondly part of the coil could embolise out of

the aneurysm into a more distal arterythe aneurysm into a more distal artery3.3. The thrombus formation may extend out of The thrombus formation may extend out of

the aneurysm and cause thrombus formation the aneurysm and cause thrombus formation in the feeding vessels in the feeding vessels

Aneurysm rupture is uncommon and can vary from Aneurysm rupture is uncommon and can vary from

a small leak to a full-blown rupture. Rupture can a small leak to a full-blown rupture. Rupture can usually be controlled angiographically but if usually be controlled angiographically but if this fails the patient may need to go to theatre.this fails the patient may need to go to theatre.

It is imperative however not to let the BP become It is imperative however not to let the BP become elevated and BP should be controlled with elevated and BP should be controlled with Propofol in the first instance. DO NOT used Propofol in the first instance. DO NOT used vasodilators to control the BP.vasodilators to control the BP.

Intra-operative Anaesthesia Intra-operative Anaesthesia PrinciplesPrinciples

The principles are : The principles are :

1.1. Avoid increases in transmural aneurysm pressureAvoid increases in transmural aneurysm pressure

2.2. Provide good conditions for the aneurysm Provide good conditions for the aneurysm surgerysurgery

a)a) "slack" brain"slack" brain

b)b) Reduce aneurysmal pressure during clipping byReduce aneurysmal pressure during clipping byi)i) Induced hypotensionInduced hypotensionii)ii) Surgically by Temporary clips Surgically by Temporary clips

3.3. Avoid damage to the brain Avoid damage to the brain

MonitoringMonitoring1.1. CVS : ECG, Arterial line (IBP), CVP (cubital fossa)CVS : ECG, Arterial line (IBP), CVP (cubital fossa)2.2. RESP : SpORESP : SpO22, End tidal CO, End tidal CO22, oesophageal , oesophageal

stethoscopestethoscope3.3. NEUROMUSCULAR : Train of 4 (by PNS) (it is NEUROMUSCULAR : Train of 4 (by PNS) (it is

essential that these patients do not move)essential that these patients do not move)4.4. CNS : Either BIS/EEG or EPs CNS : Either BIS/EEG or EPs 5.5. RENAL : U/O, all these patients are RENAL : U/O, all these patients are

catheterised the U/O provides an indication catheterised the U/O provides an indication that the diuretics are workingthat the diuretics are working

InductionInduction Principle of Induction is thatPrinciple of Induction is that rises in BP and rises in BP and

falls in ICP should be avoidedfalls in ICP should be avoided at this at this stage as that increases the transmural stage as that increases the transmural aneurysm pressure (the pressure in the aneurysm aneurysm pressure (the pressure in the aneurysm is at arterial levels) and makes rupture more is at arterial levels) and makes rupture more likely; this is a disaster if it occurslikely; this is a disaster if it occurs

Thiopentone (5-6 mg/kg) or carefully titrated Thiopentone (5-6 mg/kg) or carefully titrated Propofol (1.5 – 2.5 mg/kg) may be used. These Propofol (1.5 – 2.5 mg/kg) may be used. These tend to reduce CBF and hence ICPtend to reduce CBF and hence ICP

Narcotics ( sufentanyl, fentanyl, remifentanyl) Narcotics ( sufentanyl, fentanyl, remifentanyl) tend to increase ICP ( due to autoregulation tend to increase ICP ( due to autoregulation mediated compensatory cerebral vasodilation in mediated compensatory cerebral vasodilation in response to systemic hypotension)response to systemic hypotension)

Thus Normotension should be ensured before Thus Normotension should be ensured before their usage. Their Combination with Thiopentone their usage. Their Combination with Thiopentone is safe as the opposing effects on ICP usually is safe as the opposing effects on ICP usually cancel each other.cancel each other.

Mild Hyperventilation may be instituted in Mild Hyperventilation may be instituted in patients with elevated ICP.patients with elevated ICP.

Continued..Continued..

Succinylcholine is often used for muscle Succinylcholine is often used for muscle relaxation for intubation (found to be clinically relaxation for intubation (found to be clinically safe although theoretically it increases ICP)safe although theoretically it increases ICP)

Atracurium (hypotension) and Pancuronium Atracurium (hypotension) and Pancuronium (tachycardia and hypertension) are associated (tachycardia and hypertension) are associated with Hemodynamic disturbances and hence with Hemodynamic disturbances and hence avoidedavoided

Vecuronium might be used but long latency Vecuronium might be used but long latency obviates its useobviates its use

Rocuronium, due to short latency may be the Rocuronium, due to short latency may be the NDMR of choice in Neurosurgical AnaesthesiaNDMR of choice in Neurosurgical Anaesthesia

Complete muscle relaxation should be ensured Complete muscle relaxation should be ensured using PNS before attempting laryngoscopyusing PNS before attempting laryngoscopy

Laryngoscopy and Laryngoscopy and IntubationIntubation

Prophylaxis against BP rise during laryngoscopy Prophylaxis against BP rise during laryngoscopy may be given in form of High dose Narcotics, Beta may be given in form of High dose Narcotics, Beta adrenergic antagonists, IV or Topical Lignocaine, adrenergic antagonists, IV or Topical Lignocaine, Second dose of Thiopentone( 1-2 mg/kg), high MAC Second dose of Thiopentone( 1-2 mg/kg), high MAC IsofluraneIsoflurane

IV adjuncts best for poor SAH gradesIV adjuncts best for poor SAH grades Deep Inhalational anaesthetics may be used in good Deep Inhalational anaesthetics may be used in good

SAH grades but Avoided in those with increased ICPSAH grades but Avoided in those with increased ICP Laryngoscopy and Intubation should be smooth. If Laryngoscopy and Intubation should be smooth. If

unacceptable rises in BP are encountered, attempt unacceptable rises in BP are encountered, attempt is aborted and resorted back to mask ventilation is aborted and resorted back to mask ventilation along with deepening of anaesthesia until it is safe along with deepening of anaesthesia until it is safe to try againto try again

MaintainanceMaintainance Maintenance best with Nitrous, Remifentanil (due Maintenance best with Nitrous, Remifentanil (due

to short duration of action), and a Propofol infusion.to short duration of action), and a Propofol infusion. Avoidance of inhalational agents and the use of Avoidance of inhalational agents and the use of

an intravenous agent that causes cerebral an intravenous agent that causes cerebral vasoconstriction helps to optimise cerebral vasoconstriction helps to optimise cerebral conditions. conditions.

BP should be kept within previously defined limits BP should be kept within previously defined limits according to the patient’s baseline BP. Target is according to the patient’s baseline BP. Target is usually 20 mm Hg below baselineusually 20 mm Hg below baseline

Prior Beta blockade is preferable to reduce reflex Prior Beta blockade is preferable to reduce reflex tachycardia due to hypotensive agents, to reduce tachycardia due to hypotensive agents, to reduce the total requirement of hypotensive agents and to the total requirement of hypotensive agents and to reduce rebound hypertension once the reduce rebound hypertension once the hypotensive agent is discontinuedhypotensive agent is discontinued

Mannitol (1.5 gm/kg) combined with Frusemide Mannitol (1.5 gm/kg) combined with Frusemide (0.3mg/kg) is given to shrink the brain and provide (0.3mg/kg) is given to shrink the brain and provide good operating conditions. It takes about 1 hour for good operating conditions. It takes about 1 hour for the maximal effect so the mannitol should be the maximal effect so the mannitol should be started soon after the BP has settled down from started soon after the BP has settled down from intubationintubation

Critical Periods Critical Periods

Securing of head with Mayfield pinsSecuring of head with Mayfield pins Skin IncisionSkin Incision Periosteal Flap elevation and Bone Periosteal Flap elevation and Bone

cutting.cutting.

These stimuli might cause an These stimuli might cause an increase in BP and hence a increase in BP and hence a preemptive bolus of Narcotic or preemptive bolus of Narcotic or Propofol is advised before thesePropofol is advised before these

Induced HypotensionInduced Hypotension As the pressure inside the aneurysm is at arterial As the pressure inside the aneurysm is at arterial

levels it is usual to induce hypotension during the levels it is usual to induce hypotension during the time of dissection and clippingtime of dissection and clipping

It has been found that the aneurysm and it's It has been found that the aneurysm and it's vascular tree are more mobile at MAPs of vascular tree are more mobile at MAPs of around 50 mmHgaround 50 mmHg

In general cerebral autoregulation preserves flow at In general cerebral autoregulation preserves flow at MAPs of 50 mmHg (providing that there is not MAPs of 50 mmHg (providing that there is not raised ICP) but in patients with pre-existing raised ICP) but in patients with pre-existing uncontrolled hypertension this lower limit may be uncontrolled hypertension this lower limit may be considerable raisedconsiderable raised

It is important that the MAP is measured at the level It is important that the MAP is measured at the level of the brain and not some point below this (due to of the brain and not some point below this (due to very low margin for error)very low margin for error)

The usual thing to do is to reduce the MAP to about The usual thing to do is to reduce the MAP to about 60 mmHg as they are approaching the aneurysm 60 mmHg as they are approaching the aneurysm and only go to 50mmHg with clippingand only go to 50mmHg with clipping

Usual choice of agents is between Nitroglycerine Usual choice of agents is between Nitroglycerine and Sodium Nitroprusside with a prior beta and Sodium Nitroprusside with a prior beta blockadeblockade

HypothermiaHypothermia As the survival of tissues has been shown As the survival of tissues has been shown

to be prolonged by profound hypothermia to be prolonged by profound hypothermia (20-25°C) it was felt that this might be (20-25°C) it was felt that this might be beneficial in this type of surgery beneficial in this type of surgery

Very rarely used these daysVery rarely used these days Reasons:Reasons:1.1. For the average case it did not seem to For the average case it did not seem to

cause a decrease in the mortality cause a decrease in the mortality ( because there usually is no problem with ( because there usually is no problem with adequate blood supply as the degree and adequate blood supply as the degree and period of hypotension is not usually great)period of hypotension is not usually great)

2.2. It increases the incidence of post-op It increases the incidence of post-op vasospasmvasospasm

Post ClippingPost Clipping Once the aneurysm is clipped the BP is Once the aneurysm is clipped the BP is

raised to the pre-op level. This should be raised to the pre-op level. This should be done slowly over about 10 minsdone slowly over about 10 mins

All the fluid loss including calculated All the fluid loss including calculated insensible losses should be replaced prior insensible losses should be replaced prior to the end of surgery unless there was to the end of surgery unless there was marked Cerebral Oedema pre-opmarked Cerebral Oedema pre-op

The maintenance of adequate filling The maintenance of adequate filling pressures and BP will help prevent pressures and BP will help prevent vasospasm becoming clinically significant vasospasm becoming clinically significant

ReversalReversal

The patient is not extubated until they are The patient is not extubated until they are awake and breathing wellawake and breathing well

BP should be controlled with Propofol or BP should be controlled with Propofol or Narcotics infusionNarcotics infusion

Further agents to control BP (B blockers, Further agents to control BP (B blockers, diazoxide) during extubation might be diazoxide) during extubation might be used if infusions are found unsatisfactoryused if infusions are found unsatisfactory

If Remifentanyl has been used then If Remifentanyl has been used then Fentanyl (50-100µg) should be given after Fentanyl (50-100µg) should be given after the patient is awake and appears the patient is awake and appears neurologically normal neurologically normal

Post Operative Post Operative ManagementManagement The patients should be assessed in the recovery The patients should be assessed in the recovery

ward prior to their return to ICU as there may ward prior to their return to ICU as there may be need to re-operate if major new neurological be need to re-operate if major new neurological signs have occured. signs have occured.

The worries post-op areThe worries post-op are1.1. VasospasmVasospasm2.2. Re-bleedsRe-bleeds3.3. InfarctionInfarction either due to the clip occluding a either due to the clip occluding a

vessel or to thrombosisvessel or to thrombosis4.4. In the higher risk groups there may be continual In the higher risk groups there may be continual

decreased level of consciousness and the usual decreased level of consciousness and the usual complications occur, eg pulmonary oedemacomplications occur, eg pulmonary oedema

Post op the Post op the Fluid statusFluid status needs to be very needs to be very carefully looked at with enough fluids given carefully looked at with enough fluids given to maintain an adequate U/O but not to to maintain an adequate U/O but not to much as to cause cerebral or pulmonary much as to cause cerebral or pulmonary oedema oedema

Close eye kept on their Close eye kept on their Electrolyte statusElectrolyte status as as hyponatraemia (causes cerebral oedema)hyponatraemia (causes cerebral oedema)

If new neurological deficits are If new neurological deficits are encountered some time after an encountered some time after an apparently successful surgery, CT apparently successful surgery, CT scan is done to rule out Hematomascan is done to rule out Hematoma

If normal, Angiography needs to be If normal, Angiography needs to be done to diagnose Vasospasm.Then done to diagnose Vasospasm.Then the BP is raised until the the BP is raised until the neurological deficit goes or an neurological deficit goes or an arbitrary limit is reachedarbitrary limit is reached

ConclusionConclusion Because of the systemic effects and surgical Because of the systemic effects and surgical

requirements, patient with cerebral aneurysms requirements, patient with cerebral aneurysms present a unique challenge to anaesthesiologist. present a unique challenge to anaesthesiologist. As an anaesthesiologist we should have a As an anaesthesiologist we should have a thorough understanding of pathophysiology of thorough understanding of pathophysiology of SAH, a communication with the neurosurgeon SAH, a communication with the neurosurgeon regarding approach, a formulation of an regarding approach, a formulation of an anaesthetic plan and its implementation. There anaesthetic plan and its implementation. There will always be patients who despite our best will always be patients who despite our best efforts, fail to benefit from the surgical procedure, efforts, fail to benefit from the surgical procedure, however with proper planning optimal results can however with proper planning optimal results can be hoped for.be hoped for.

Thank You.Thank You.