Anesthetic Management of Intracranial Aneurysms

Speakers: Riwa El Masri, PGY III

Vana Mouawad, PGY I

Moderator: C. Zeeni, MD

Objectives

• Understand the basic characteristics of intracranial aneurysms

• Recognize the different treatment modalities of intracranial aneurysms

• Understand the basic anesthetic management of intracranial aneurysm clipping.

What is an aneurysm?

• A localized dilation or ballooning of blood vessels

• Cerebral vasculature is a common site for aneurysm formation

Epidemiology

• Incidence : 1 to 6%

• Incidence of ruptured aneurysm: 12/100,000

• Age: any age, peaks 40 - 60.

• Sex: M/F 2:3

• Genetic loci on chr 1, 2, 7, 11 and 19

• Rupture : 90% < 12mm, 5% 12-15mm, 5% > 15mm.

Risk factors for intracranial aneurysm

Inherited RF Others

Polycystic kidney disease Over 50 years of age

Type IV Ehler Danlos syndrome Female gender

Pseudoxanthoma elasticum Smoking

Hereditary hemorrhagic telangectasia Cocaine use

Neurofibromatosis type 1 Infection of vessel wall

Alpha 1 antitrypsin deficiency Head trauma

Coarctation of the aorta Septic emboli

Fibromuscular dysplasia Hypertension

Pheochromocytoma Alcohol abuse

Klinfelter’s syndrome Oral contraceptive pills

Tuberous sclerosis hypercholesterolemia

Noonan’s syndrome

Alpha glucosidase deficiency

Locations

• 85% anterior circle of Willis

• Most commonly:

– ACA + AComm (30-35%)

– Internal carotid (ICA) + PComm (25%)

– MCA (20%)

– Basilar artery + remaining posterior circulation artery (5-10%)

Classification

• Congenital or acquired

• True or false

• By size:

»Small: ≤ 10mm

»Large: 11 to 25mm

»Giant: > 25mm

• By shape:

– Saccular: aka berry aneurysm, has a neck/stem

– Fusiform: without stem

– Dissecting: blood flows from a false lumen

Intracranial Aneurysm

• 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

Clinical Presentation

• Incidental finding if unruptured

• Ruptured: sudden severe headache “worse headache of my life”, nausea, vision impairment, vomiting, & LOC

Ruptured Aneurysm

• Increased ICP + stroke

• Risk of rupture rises with the size of the aneurysm

• Ruptured aneurysm = real emergency.

Mortality after SAH

• Of the cases that reach the hospital 50% die

within 4 weeks • 70% from the initial bleed 30% from re-bleeding

and vasospasm. • Re-bleeds do very badly: Mortality after first re-

bleed 64%, second 96% and usually within 24 hours

• 50% of the survivors will have neurological deficits.

Classification of Ruptured Aneurysms HUNT and HESS scale

FISHER GRADE: based on CT scan

Vasospasm

• Most feared complication of SAH

• Occurs 1 to 2 weeks following initial hemorrhage

• Pathophysiology not well understood yet

• Blood in SAS inflammation entrapped macrophages and neutrophils endothelins & free radicals vasospasm stoke

Vasospasm Diagnosis

• Magnetic resonance angiography (MRA)

• Ct angiography

• Transcranial doppler ultrasonography (TCDs)

• Intra-arterial digital subtraction angiography GOLD STANDARD but invasive

– 1% risk of transient neurologic complications

– 0.5% risk of permanent neurologic complications

Cerebral Angiography

Intracranial Aneurysm Treatment Modalities

• Surgical: Clipping – Direct

– Temporary clipping

– Balloon suction decompression

– Trapping with clip reconstruction +/- EC IC bypass

– Adenosine cardiac standstill

– Deep hypothermic circulatory arrest

• Non surgical: coiling – Coiling

– Stent assisted coiling

Surgical Treatment- Clipping

• Aim: isolate the weakened vessel area from the blood supply

• Strategic placement of one or more small surgical clips to neck

• Isolates from normal circulation w/o damaging or impinging on adjacent vessels or branches

Determination of the Technique

• Depends on

– Size

– Location

– Characteristics of the neck and neck pressure

What is a clip?

Direct Clipping

• When the surgeon can visualize the surrounding structures, parent vessel and perforators and when the neck is soft.

• Direct application with clip appliers

Temporary Clipping

1. A temporary clip is placed on the parent vessel

2. A permanent clip is placed on the aneurysm neck

3. The temporary clip is removed from the parent vessel

Difference between Temporary & Permanent clips

Retrograde Suction Decompression

Distal

Blood flow

direction

proximal

Trapping and clip reconstruction

EC-IC bypass

• Branch of the EC artery (STA) to a branch of the IC artery (MCA), either directly or via a vein graft.

• The anastomosis is made distal to the aneurysm to maintain perfusion while working on the reconstruction of the aneurysm.

• Concept similar to cardiac bypass surgery

I-Preoperative Assessment

• The approach to a ruptured aneurysm is different than an elective clipping

• Focus on:

– Baseline blood pressure

– Baseline neurologic exam

– Possible cardiopulmonary repercussions if the aneurysm is ruptured

– Fluid status

Fluid status & Cerebral Aneurysm Management:

Fluid overload, hyponatremia,

CHF

Cerebral edema

Too dry,

Vasospasm,

Compromised cerebral

circulation

Preoperative tests

i) Electrolytes, kidney function and glucose level.

ii) Hg/Hct /Plts

iii) Coags: INR/APTT, PT and fibrinogen, type and cross match for PRBC

iv) ECG: done on the day prior to surgery 50-80% pts have changes

v) CXR: assessment of RESP and CVS pathology

vi) Echo: looking for neurogenic cardiac failure if high suspicion

ECG changes

ST abnormalities T wave abnormalities

QT prolongation ventricular tachycardia

Myocardial lesions

Diastolic dysfunction Ventricular hypokinesis and reduced EF

Premedication

• Ruptured aneurysms: usually decreased mental status and elevated ICP: No premedication

• Elective clipping: good premedication necessary to decrease anxiety and reduce risk of BP elevation

Intraoperative management

• Avoid aneurysm rupture/rebleeding • Minimize potential secondary neurologic injury • Provide good conditions for intracranial surgery a) "slack" brain b) reduce neck pressure during clipping

• Management of temporary ischemia • Smooth emergence and rapid neurologic

evaluation

Monitoring

• CV: ECG, Arterial line, CVP?

• Resp: SpO2, ETCO2

• Neuromuscular: Train of 4 • CNS: EEG and/or EPs • Renal: Foley U/O .

II-Keys to Induction

• Aim= avoid increases in BP at all costs

• Any combination of anesthetic medications can be used (avoiding ketamine), ensure the patient is adequately deep before attempting intubation.

• Adjunct short acting blood pressure controlling medications can be used such as esmolol, hydralazine, nicardipine…sodium nitroprusside drip to supplement just before intubation

II-Keys to Induction

- Do not intubate until full relaxation achieved to avoid bucking.

- Be generous with opioids before attempting intubation

- Intubation should be smooth and quick, by an experienced anesthesiologist.

- If the BP rises during intubation give further doses of opioids or adjuncts until controlled.

- Pay close attention to eyes (betadine)

III- Maintenance

• Opioid infusions are preferable

• NMB infusions to maintain immobility

• Low dose volatile agents due to the uncoupling effect and increases in ICP (< 1 MAC)

• Nitrous oxide can be used, but should be avoided if the brain is tight.

III- Maintenance

• Consider TIVA for maximum brain relaxation

• Use osmotic diuretics if necessary

• Hyperventilate to target CO2 of 30

• Aim for a BP 20% lower than baseline (i.e. BP at home)

Avoidance of inhaled

anesthetics

The use of intravenous agents that

cause cerebral vasoconstriction

Optimize cerebral

conditions

Mannitol 0.25-1g/kg

3% (hypertonic)

saline

Shrink the brain and intracranial pressure :better

working conditions

Pinning

• Mayfield pin insertion is as irritating as laryngoscopy

• At pin insertion deepen the anesthetic:

Add Propofol bolus

Add/increase opioids

Add Local Anesthetic at the site

Use short acting adjuncts to supplement

Induced hypotension

Some surgeons ask for induced hypotension during dissection & clipping to reduce neck tension

This ↓ transmural wall tension more soft/malleable for clip placement

For direct clipping consider reducing the MAP to about 60mmHg when dissecting and ready to clip

Induced hypotension

Vasospasm +cerebral ischemia

Coronary ischemia

Inhibition of hypoxic

pulmonary vasoconstriction

Reduced hepatic and renal BF

hyperglycemia

Temporary Clipping

• Just before temporary clipping, consider putting the patient in burst suppression by bolusing propofol/thiopental

• As soon as the temporary clip is on: – Start the timer

– Increase the blood pressure by 20% in order to increase collateral flow from the circle of Willis

– As soon as the temporary clip is off, stop the timer, return the BP to pre temporary levels.

– Document temporary clipping time

IV-Emergence and early post-op care

Aim: prompt emergence that allows immediate neurologic assessment + early intervention in case of:

Clip malposition

vasospasm hematoma

IV-Emergence & early post-op care

Emergence can be associated with intracranial & systemic hypertension

Main cause of intracranial hypertension

1- The use of a short acting opioid infusion such as remifentanil helps blunting the cough reflex during emergence

2- Other techniques: IV lidocaine, or in ET tube

3- PONV prophylaxis!

coughing

IV-Emergence & early post-op care

• Tendency to undertreat pain after craniotomies

• minimize noxious stimulation and treat pain adequately

• Fentanyl PCA>>> PRN for post op pain treatment*

*Morad AH, Winters BD, Yaster M, et al. Efficacy of intravenous patient-controlled analgesia after supratentorial intracranial surgery: a prospective randomized controlled trial. Clinical article. J Neurosurg 2009; 111:343-350 PubMed

Cerebral Protection

1- Glucose control

2- Corticosteroids

3- Barbiturates

4- Hypothermia

5- Monitoring for impending neurologic injury

6- Intraoperative anatomic monitoring

1-Glucose Control

• Hyperglycemia + ischemia = worse outcomes

• Hyperglycemia+ absence of O2 anaerobic glycolysis lactate intracellular acidosis more neuronal injury ↑cerebral infarct size

• If Glucose> 150mg/dl start insulin

2-Corticosteroids

• Used to decrease peritumoral vasogenic edema

• HOWEVER: no sufficient data for any beneficial effect on focal or global cerebral ischemia

• Animal studies: exacerbate ischemic injury by increasing plasma glucose level

No place during aneurysm clipping

3- Barbiturates

• They decrease ICP, CBF and Metabolic rate.

• Cause burst suppression at high doses

• ? Improvement in mortality/ morbidity

• The large doses needed can lead to cardiovascular depression

• Etomidate or propofol alternatives, more hemodynamic stability

4-Hypothermia

• Since 1950 mild hypothermia cerebral protection

HOW?

Decreasing CMRO2

hypothermia

Decrease CMR

Less energy requirement

Withstand ischemia for a longer time

More operative ischemia

time

HOWEVER!!

Mild Hypothermia

Inhibition of platelet and coagulation

factor activation

Increased susceptebility

to cardiac dysrhythmias

Post-op wound

infection and hyperglycemia

intra-op

So what is the consensus on hypothermia?

The answer with Dr Assadi on Wednesday…

5-Monitoring for Impending Neurologic Injury

- Extremely useful in detecting cerebral ischemia prior to irreversible neuronal damage

- Ideal monitor= react RAPIDLY and RELIABLY to even small changes in regional cerebral blood flow

Unfortunately direct cerebral blood flow monitors (xenon washout, transcranial

doppler)

indirect monitors (brain tissue oxygen

tension, cerebral oximetry)

inability to monitor multiple cerebral regions

simultaneosly

impracticality of continuous

use during craniotomy

imperfect surrogate

markers of cerebral blood

flow

are limited by

EEG monitoring : of limited use

- +

Evoked potential monitoring

Brainstem auditory evoked potentials (BAEPs) Somatosensory evoked potentials (SSEPs) Motor evoked potentials (MEPs) Assess the integrity of neural pathways and detect

impending neurologic injury when used in combination and are now routinely used in some centers

6-Intraoperative Anatomic Monitoring

Clip misplacement with impingement of parent or perforating arteries can result in potentially disastrous outcomes

Intraoperative vascular imaging as well as neuromonitoring can be valuable in reducing the morbidity of intracranial vascular surgery

Gold standard: Intraoperative Angiography

• Complex & carries risk for vessel injury & stroke

• Indocyanine green (ICG) angiography= simpler method of anatomic visualization with clinical value

• ICG dose: 0.2-0.5mg/kg bolus, max daily dose= 5mg/kg, hepatically eliminated, ½ life 3 min