Anaesthesia for Interventional

Neuroradiology

Presentor : Dr.Kumar

Moderator : Dr.chaitanya

Intro

A trend towards minimally invasive neurosurgery, an important

development in which has been the introduction of the Guglielmi

detachable coil (GDC) for endovascular aneurysm coiling.

Anaesthesia is required for neuroradiological diagnostic procedures such

as angiograms,computerized tomography (CT), and magnetic resonance

imaging (MRI) or for therapeutic intervention

Indications

Anaesthetic concerns INR procedures, including

1. maintaining immobility during procedures to facilitate imaging

2. rapid recovery from anesthesia at the end of procedures to

facilitate neurologic examination and monitoring or to provide for

intermittent evaluation of neurologic function during procedures

3. managing anticoagulation

4. treating and managing sudden, unexpected procedure-specific

complications during procedures (eg, hemorrhage or vascular

occlusion) which may involve manipulating systemic or regional

blood Pressures

5. guiding the medical management of critical care patients

Pre operative assessment

Patients who have had an SAH can have

marked derangement of various organ

systems

Pulmonary complications are the most

common non-neurological cause of death

Neurology

A brief history and short neurological examination

should be carried

1. Glasgow Coma Scale,

2. Grade of SAH

3. Any cranial nerve, visual field, and

4. Motor and sensory deficits

The nature, location, and size of the lesion and

previous treatment must also be ascertained.

Cardiovascular system Massive catecholamine release is the most likely cause of cardiac

dysfunction seen after SAH.

This may include dysrhythmias, abnormal ECG morphology (T

inversion, ST depression, Q waves, U waves, and prolonged QT),

elevated cardiac enzymes, and frequent left ventricular dysfunction

and pulmonary oedema.

Therapy with oral anticoagulants should be stopped and, if

necessary, converted to heparin, which can be stopped or reversed,

if required.

Respiratory system

In addition to the strong causal relationship

between SAH

cigarette smoking

reduced levels of consciousness

prolonged bed rest

predispose to atelectasis and pneumonia

Metabolic considerations Tight control of blood glucose is essential since hyper- and

hypoglycemia are associated with poor outcomes,particularly in the

presence of cerebral ischaemia.

Patients are often dehydrated with electrolyte disturbances such as

1. hypomagnesaemia,

2. hypernatraemia,

3. hyponatraemia associated with the syndrome of inappropriate

ADH secretion,

4. hypokalaemia, and

5. hypocalcaemia

Conduct of anaesthesia

Premedication Premedication should be individualized. A titrated dose of a

benzodiazepine (e.g. midazolam) provides anxiolysis, sedation of short

duration, and amnesia, although it can impair assessment of

neurological status and worsen confusion

Narcotics are best avoided because of potential respiratory depression

and hypercarbia.

H2 -receptor antagonists, alone or with metoclopramide, may be used

to reduce the risks of gastric aspiration.

Nimodipine is frequently used to reduce cerebral ischaemia

consequent to cerebral vasospasm.

Induction

The overriding priority is to maintain cardiovascular

stability, avoiding surges in arterial pressure that might

cause aneurysm rupture while maintaining adequate

perfusion of a possibly ischaemic cerebral circulation.

To this end, propofol is usually used to induce

anaesthesia combined with remifentanil, alfentanil, or

fentanyl; thiopentone and etomidate are alternatives.

Pressor responses can also be obtunded with i.v.

lidocaine or rapid, short-acting b-blockers (e.g. esmolol).

Before tracheal intubation, it is important to ensure that

neuromuscular block is profound; before administration of

neuromuscular blocking agent, the correct placement of

electrodes for peripheral nerve stimulation should be verified.

Rocuronium, atracurium, or vecuronium are suitable for

neuromuscular block. It is useful to use a cut endotracheal tube

so that the image intensifier does not push in or kink the tube

The laryngeal mask airway has also been used in this setting;

there is insufficient evidence to recommend its routine use

Maintainence

Sevoflurane is the volatile anaesthetic agent of choice

because of its low potential for increasing CBF – ICP and

its rapid offset.

Up to 1 MAC, there is preservation of the reactivity of

cerebral blood vessels to carbon dioxide and coupling of

CBF and CMRO2

Sevoflurane also provides faster recovery and

postoperative neurological assessment than isoflurane.

Nitrous oxide (N2O) elevates CBF and ICP and increases

the consequences of air embolism; it should not be used

The use of a TIVA technique incorporating propofol and a short-

acting opioid reduces CBF, ICP, and CMRO2.

Of the short-acting opioids, remifentanil is frequently used; it

provides stable haemodynamics and allows more rapid recovery

from anaesthesia than alfentanil or fentanyl

Rebound hypertension may develop on sudden discontinuation of

the infusion, necessitating a slow decrease in rate before

emergence.

Propofol and remifentanil, sevoflurane and remifentanil, and a

combination of propofol and remifentanil supplemented with

sevoflurane.

Ventilation Ventilation aims for mild hypocapnia to normocapnia (Paco2 4 – 4.5

kPa) to help control ICP

It is important to distinguish two general settings where

hyperventilation is used in anesthetic practice.

First, it is used to treat intracranial hypertension.

Hyperventilation is an important mainstay of the acute management of

an intracranial catastrophe to reduce cerebral blood volume acutely.

The second, far more common, application is to provide brain

relaxation after the skull is open with the intent of providing better

surgical access and, presumably, a lesser degree of brain retraction for

a given surgical approach

Delibrate hypertension

During acute arterial occlusion or vasospasm, the only practical

way to increase collateral blood flow may be an augmentation of

the collateral perfusion pressure by raising the systemic blood

pressure.

The extent to which the blood pressure has to be raised depends

on the condition of patients and the nature of the disease.

Typically, during deliberate hypertension, the systemic blood

pressure is raised by 30% to 40% above the baseline in the

absence of some direct outcome measure, such as resolution of

ischemic symptoms or imaging evidence of improved perfusion.

Phenylephrine usually is the first-line agent for deliberate

hypertension and is titrated to achieve the desired level of blood

pressure.

The EKG and ST segment monitor should be inspected carefully

for signs of myocardial ischemia.

The risk for causing hemorrhage into an ischemic area must be

weighed against the benefits of improving perfusion, but

augmentation of blood pressure in the face of acute cerebral

ischemia probably is protective in most settings.

There also is a risk for rupturing an aneurysm or arteriovenous

malformation (AVM) with induction of hypertension

Delibrate hypotension

The two primary indications for induced hypotension

are

1. to test cerebrovascular reserve in patients

undergoing carotid occlusion.

2. to slow flow in a feeding artery of brain AVMs before

glue injection (sometimes termed ‘‘flow arrest’’).

The most important factor in choosing a hypotensive

agent is the ability to achieve safely and expeditiously

the de-sired reduction in blood pressure while

maintaining patients physiologically stable

Anti coagulation Heparin is administered as an initial i.v. bolus

(5000 IU) or 70 units /kg followed by intermittent boluses or an infusion to keep ACT 2 – 3 times baseline; ACT is monitored hourly.

For reversal of heparin anticoagulation, protamine is used in a dose of 1 mg per 100 units of heparin or dosed according to the heparin dose – response curve.

Complications of protamine administration include I. hypotension, II. anaphylaxis,III. pulmonary hypertension

Direct thrombin inhibitors inhibit free and clot-bound

thrombin, and their effect can be monitored by

either activated partial thromboplastin time or ACT.

Lepirudin and bivalirudin, a synthetic derivative,

have half-lives of 40 to 120 minutes and

approximately 25 minutes, respectively.

Because these drugs undergo renal elimination,

dose adjustments may be needed in patients who

have renal dysfunction.

Temperature Control of body temperature is important; hyperthermia is associated with poor

outcome, and mild hypother-mia has not shown to improve

neurological outcome

Recovery A rapid and smooth recovery is desirable to

facilitate early neurological assessment and safe transfer to recovery areas.

Blood pressure is allowed to return to normal or up to a systolic pressure of 160 mm Hg.

An unsecured or incompletely secured aneurysm may call for induced hypotension.

Patients who have had neurological complications may need to be transferred to neurointensive care for continued sedation and ventilation

Complications Vascular complications are either

haemorrhagic or occlusive Vascular rupture or perforation may be: 1. spontaneous;2. due to hypertension during laryngoscopy,

emergence, inadequate depth of anaesthesia, or associated with the use of vasoactive drugs.

3. brought about by the microcatheter, guide wire, coil, or injection of contrast

Management of intracranial catastrophes

Specific procedures

Tumors & AV malformations

• Maintain lower blood pressure

a. Reduces flow through fistulous lesion

b. Greater precision for delivery of

cyanoacrylate glues

c. To prevent glue passage into the draining

veins or systemic venous system

Intracranial Aneurysms• 2 basic approaches 1. occlusion of proximal parent arteries 2. obliteration of the aneurysmal sac. (coil

embolization )

Risks – spontaneous rupture, leaky sac, vascular rupture secondary to manipulation

Alternate – stent assisted coiling methods • Risks - parent vessel occlusion,

thromboembolism, or vascular rupture.

AV malformations • Goal : To obliterate as many of the fistulae and

their respective feeding arteries as possible

• Method : embolization with cyanoacrylate glues

• Complications : 1. Acute hemorrhage2. Pulmonary embolism

Carotid Angioplasty & Stenting Anesthetist services are mostly

requested for compromised patients Relative contraindications to CAS

include –

• Antiplatelet agent intolerance, • Other pending surgery that precludes antiplatelet

agents, • Aortic arch disease (age)• Altered carotid morphology, including carotid

tortuosity, concentric calcification (which entails a risk of vessel rupture),

• Heavy thrombus burden, and unstable plaque

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