Anaesthesia for intracranial vascular surgery

Dr. S. Parthasarathy MD., DA., DNB, MD (Acu),

Dip. Diab.DCA, Dip. Software statistics,Phd (physio)

Mahatma Gandhi Medical college and research institute , puducherry , India

What is it ??

A localized dilation or ballooning of blood vessels

Dr SPS

Incidence and sites

Incidence : 1 to 6% • •Incidence of ruptured aneurysm: 12/100,000 • •Age: any age, peaks 40 - 60. • •Sex: M/F 2:3 • Sites : 30% ICA 40% ACA( Anterior Communicating) 20% MCA 10% Vertebro-basilar systems

Anterior – 85 %

85 %

Types

• Berry (pedunculated)• Fusiform • Dissecting

Mostly asymptomatic

• •Subarachnoid hemorrhage (SAH) due to aneurysmal rupture

• –Lethal event: 25% don’t even get to the hospital • –In hospital mortality rate up to 50% • –Most survivors have permanent disability • Size – < 12 mm , 12 to 24 mm, > 24 mm • Neuronal injury due to bleed • Vasospasm • Rebleeds

• The three main predictors of mortality and dependence

• impaired level of consciousness on admission,

• advanced age, • and large volume of blood on initial cranial

computed tomography

Clinical features • Incidental finding if un ruptured • Hematoma and edema • Ruptured: sudden severe headache “worse

headache of my life”, nausea, vision impairment, vomiting, & LOC

• Hydrocephalus- blood clots on Subarachnoid granulations & ventricles ↓ CSF absorption & obstruct CSF drainage

• Increased ICP , stroke • Lethal event: 25% don’t even get to the hospital

Hunt and hess scale

2

Mortality

35 %

Fischer - CT scan based features

World federation of neuro surgeons

Vasospasm- 13.5% cause of mortality & morbidity.

• Most feared complication of SAH • •Occurs 1 to 2 weeks following initial

hemorrhage • Patho physiology not well understood• Blood in SAS→ inflammation → entrapped

macrophages and neutrophils → endothelins & free radicals → vasospasm → stroke

New onset neuro signs

Vasospasm

• Magnetic resonance angiography (MRA) • Ct angiography • Transcranial doppler ultrasonography (TCDs) • Intra-arterial digital subtraction angiography

GOLD STANDARD but invasive

Nimodipine• Improve outcome in vasospasm • Oral 60mg 4Hly, max dose 360mg for 21 days• IV 1mg/hr during the first 6 hrs,• increase gradually to max 2mg/hr• Maintain SBP 130-150mmhg• risk of hypotension• central line to avoid thrombophlebitis.

Hypertension, hypervolumia ,hemodilution ( 3 H )

• SBP 120-150 mmhg in unclipped

• 160-200 mmHg in clipped aneurysm.

• CVP 8-12mmHg

• HCT 30-35%

• Intraarterial papaverine

Rebleeds

• The overall incidence of re bleeding is 11%.• 1 – 12 days • Deterioration

• 70 % mortality

• Prevention • BP maintain , seizure control ,ICP maintenance

What should we do ??

From outside

Or from inside

Thrombogenic – new intima will

grow inside

When to touch

• 0- 3 days

• 4 – 10 days

• Controversial

Preoperative evaluation

• Careful medical history • Physical examination • Baseline BP , fluid status • Hyponatremia (brain natriuretic peptide) • Prolonged bed rest runs the risk of atelectasis

and pneumonia .• CNS examination

Pre op work up

• Investigations --- for the diagnosis • Routine + ECG, ECHO, CxR , coagulation

profile • T wave inversion & ST depression (most

common), Prolong QT (atrial & ventricular dysrhythmias) -- catecholamine surge

• Pregnancy test ( pregnant ruptures the aneurysm)

• Talk to the surgeon also

Neuro radiology

• Cerebral Angiogram Site of the aneurysm Prepare for intraop positioning, surgical exposure & monitoring• CT scan Amount of subarachnoid blood in the basal cisterns is good predictor of delayed vasospasm Increase ICP from IC haemorrhage, hydrocephalus or cerebral oedema• TCD facilitate vasospasm management.

Premedication

• Calcium channel-blocking drugs, anticonvulsants, and steroids are continued.

• No sedatives • No narcotics • Possible acid aspiration prophylaxis • preoperative administration of erythropoietin in

elective cases might reduce injury from reversible ischemia during temporary clipping

Cardiac evaluation

• Elevated Troponin 17-28%• Elevated CKMB 37%• Echo LV dysfunction Syndrome of neurogenic-stunned myocardium• Cardiogenic shock• pulmonary oedema• But OK – don’t postpone – no added

treatment

Monitoring

1. CVS : ECG, Arterial line (IBP), CVP (cubital fossa)

2. RESP : SpO2, End tidal CO2, oesophageal stethoscope

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

that these patients do not move)

4. CNS : Either BIS/EEG or EPs

5. RENAL : U/O, all these patients are catheterised the

U/O provides an indication that the diuretics are working

Monitoring

• brain temperature

Intermittent arterial blood gases, glucose, electrolytes,

osmolality, hematocrit, urine output

EEG evoked potentials – duration of occlusion? IV

anaesthetics better

Jugular bulb oxygen monitoring can also be helpful in

patients at risk for global cerebral ischemia.

Can we place the leads ??

• SSEP monitoring has mostly been used during

aneurysm surgery in the territory of both

anterior and posterior cerebral circulation,

• BAEP monitoring has been used during

operations in the territory of the vertebral-

basilar circulation.

Anesthetic Management

• Goals • Decrease transmural pressure gradient

• Don’t try to control ICP much !!

Goals

• maintaining adequate CPP and cerebral oxygenation;

• preventing the development of a “tight” brain from cerebral edema or vascular engorgement.

Induction !!!

Induction • Thio – 5- 6 mg/Kg • Smooth induction – narcotics • IV lignocaine or esmolol • Scoline – OK • Vecuronium – complete muscle relaxation • Local and fentanyl for pinning• Normotension

Maintenance

• Nitrous ?? , fentanyl, propofol - infusion

• BP should be kept within previously defined limits

according to the patient’s baseline BP. Target is usually

20 mm Hg below baseline

• Prior Beta blockade may help

• Mannitol (1.5 gm/kg) combined with Frusemide

(0.3mg/kg) is given to shrink the brain

Crucial times

• Securing of head with Mayfield pins

• Skin Incision

• Periosteal Flap elevation and Bone cutting.

• Narcotic, propofol , Local

The basics of brain slackness

• crucial for safe surgical dissection to proceed. • implement moderate hypocapnia (PaCO2 25–

30 mmHg); • elevate the head position; • Add diuretics and mannitol; • Drain spinal fluid; • Avoid cerebral vasodilators

BP ?? !!

• Before clipping – get down the BP

• After clipping - increase to just above baseline is acceptable – 10 minutes

• Hypothermia – not acceptable – vasospasm is more common

Intra op problems

Coiling problems 1. The aneurysm may rupture with the angiographic

manipulation 2. Secondly part of the coil could embolise out of the

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

aneurysm and cause thrombus formation in the feeding vessels

4. Propofol or Thio 5. No vasodilators 6. Control angiographically 7. Rarely done with IV sedation

Aneurysmal rupture

• 11% of patients with previously ruptured aneurysm

(compared with an incidence of 1.2% in previously

un ruptured aneurysms).

• Maintain fluid and BP ?? • Clamp before and after the aneurysm

Reversal

• The patient is not extubated until they are awake and

breathing well

• BP should be controlled with Propofol or Narcotics

infusion

• Further agents to control BP (Beta blockers) during

extubation might be used if infusions are found

unsatisfactory

Post op problems • Neuro deficits – new

• Then do

• CT scan

• If normal

• Do angio for vasospasm

Vasospasm Rebleeds Infarction Fluid status Urine output Hyponatremia

Summary

• Worst headache ( neuro, vasospasm, rebleeds) • Incidence ( impending doom!!) • Hunt, Fischer WFNS • Ecto and endo • Pre op – CNS, general, investigations• Induction – maintenance - recovery • Post op monitoring

Thank you all