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