Anesthesia for interventional neuroradiology

Introduction


I could not find nothing more appropiate to start this topic  than this blessing (Asher Yatzar) that   jews say several times a day:

The Asher Yatzar blessing was initiated by the holy Amora (Talmudic sage) Abayei, (see tractate Brachot 60b). The Gemara says: "Abayei said, when one comes out of a privy one should say: 

"Blessed is He who has formed man in wisdom and created in him many orifices and many cavities. It is obvious and known before Your throne of glory that if one of them were to be ruptured or one of them obstructed, it would be impossible for a man to survive and stand before You. Blessed are You that heals all flesh and does wonders."

Indications for treatment 

 Most frequent procedures in our hospital are aneurysm coiling, AVM embolization , tumor embolization,carotid stenting, treatment of vasospasm or stenosis, stroke intervention.

 Most procedures are performed under general endotracheal anesthesia for airway control and  immobility.

General goals

Patient immobility

Avoidance of injuries

Physiological stability

Airway control

Hemodynamic manipulation

Management of anticoagulants/antiplatelets

Rapid recovery for neurological assessment

Avoidance of hyperthermia/hypothermia

Good communication with radiologists

Safe intrahospital  transport

Radiation safety

Preoperative assessment

Special emphasis in the following items:

Airway –Difficult airway in a remote location.

Cardiovascular function- Arterial hypertension, SAH related myocardial ischemia, previous function

Renal function.-contrast nephropathy

Respiratory- pulmonary edema (hydrostatic, neurogenic)
Neurologic- SAH, intracerebral hematoma.

Drugs- antiplatelets, anticoagulants,Ca channel blockers.

Accessory examinations: EKG, chest xray ,TCD,CT angio,MRI,MRA.

Laboratory- routine, baseline coagulation screen, platelet  function.

Room preparation

Similar to any  OR

Ideally get help of an anesthesia technician.

Check anesthetic chart, drugs, difficult intubation equipment.

Monitoring

Standard monitoring, urinary catheter.

Arterial line is placed before induction with local anesthesia. Transducer fixed to a pole in the x-ray table.

Intra-intervention laboratory- ABG, ACT.

 IV access-with extension tubes. In TIVA ,dedicated iv cannula.

Induction

Critical in aneurysm because risk of rupture.

Smooth induction with  attenuation of CV response to intubation and maintenance of CPP.

After a small dose of midazolam,  spray lidocaine 10% over tongue,oropharynx.

IV fentanyl 2 mcg/kg.

Hypnosis: Propofol 1-2 mg/kg,or thiopental 3-5 mg/kg or etomidate 0.2 mg/kg.

Muscle relaxant : rocuronium or vecuronium.

Ventilate with O₂ and isoflurane before laryngoscopy.

Available drugs: Nitropruside,labetalol,phenylephrine.

Let BP decrease 20% of baseline.

Trial laryngoscopy- minimal CV response, proceed with intubation. If BP rises, deepen anesthesia with fentanyl, ventilate with more  isoflurane and try again.

Maintenance

Balanced anesthesia with isoflurane at < 1 MAC.

Further doses of fentanyl are generally not needed.

Muscle relaxants: atracurium in continuous infusion or repetitive doses of vecuronium/rocuronium.

TIVA –is another option, propofol/remifentanyl.

Fluids

Patients are generally hypovolemic due to poor intake , contrast media.

Replace fluids with normal saline. Glucose is avoided.

Keep Ht 30-35%

Hetastarch is not recommended due to its interference with coagulation.

Anticoagulation

Routine in intracranial procedures

After measuring a baseline ACT( normal is  90-130 sec) give heparine  2500 to 5000 units to prolong ACT 2-2.5 times.

An adverse effect of heparine administration is induced thrombocytopenia, accompanied by platelets activation and thrombotic complications. In this event it is recommended to shift to a direct thrombin inhibitor like argatoban or lepirudin.
GPIIb/IIIa inhibitors can also produce severe thrombocytopenia. To rule out,check CBC 4 hours after administration.                                     

For acute platelet plugs ,systemic eptifibatide is administered (see table in the angio suite) and/ or intraarterial tissue plasminogen activator (tPA).

Reversal of heparine- protamine, its dose depending on the time elapsed since last dose of heparine.

Reversal of GPIIb/IIIa inhibitors –platelet transfusions

Reversal of Eptifibatide -FFP

Hemodynamic control

Labetalol,α and β blocker, reduces BP and HR.

Nitroprusside-direct vasodilator,  dilates cerebral vessels. May rise ICP in patients with  decreased  cranial elastance.

Phenylephrine- does not influence ICP, is a pure α agonist.

Specific procedures

Aneurysms

The procedure consists in the introduction of coils, or stent and coils which obliterate the aneurysm and promote intraaneurysm clotting.

Complications
-Embolism.

-Rupture of the aneurysm-  extravasation of contrast , Cushing triad.

Treatment- the radiologist  will try to introduce coils to stop bleeding.

-Heparine reversal with protamine

-Lower BP

-Mannitol to reduce ICP.

-Rarely emergency craniotomy for ventriculostomy ,clipping of aneurism.

Occlusion:

Increase BP

Trombolysis-systemic and  intrarterial , mechanical removal of thrombus

AVM  Embolization

AVM  generally requires multiple sessions to occlude AVM nidus or feeding arteries.In some cases, the occlusion of the AVM produce an increase of the CBF in the normal parenquima, which may exceed the autoregulation capacity and cause intraparenquimatous hemorrhages.

It is recommended  to reduce the BP 20% below the patient's  baseline BP.

The obstruction of the draining veins by glue can cause venous outflow obstruction and pulmonary embolism.
Another complication is perforation  with extravasation of contrast media.The treatment is similar to  the rupture of aneurysm.

Stenting for  carotid occlusive disease

Generally done  under monitored anesthesia care,under light sedation, to  assess neurologic function during the procedure.

Drugs :fentanyl, midazolam.

Bradycardia  and asystole from carotid body stimulation can occur. Have atropine ready.
If atropine does not work,chronotropic drugs are as good as external pacing.

Other complications- perforation of the artery ,dissection, spasm, TIA, stroke,

hyperperfusion syndrome

Emergence of general anesthesia

Avoid coughing and bucking.

Treat severe hypertension with labetalol starting at 0.25 mg/k  bolus.
Transfer the patient to neurosurgical intensive care.


I  wish to thank Dr.Yaaqov Amsalem,MD, Director of the Invasive Neuro-Radiology Service
for the revision of this guidelines and for the useful comments and suggestions.