• Cerebral embolization is performed in the neuroradiology suite for the treatment of cerebral aneurysms, arteriovenous malformations (AVM), and in preparation for intracranial tumor resections.
• Patients presenting for embolization range from being very healthy with unruptured aneurysms (Hunt and Hess classification grade 1, survival >70%) to comatose and moribund (Hunt and Hess grade 5, survival <10%).
• These procedures can be lengthy and uncomfortable for patients and hence will either require monitored anesthesia care or general anesthesia.
• Vascular sheaths are introduced into the femoral arteries, through which catheters are passed. Fluoroscopy is used to advance and position the catheters near the level of the aneurysm. Microcatheters with detachable coils are then threaded through the catheter and deployed at the site of the aneurysm. Coils are typically made of soft platinum wires with a diameter smaller than a strand of hair; they come in varying diameters and lengths. They are flexible and can conform to the aneurysm shape.
• The body eventually forms blood clots around the coils and blocks blood flow into the bulge or passageway to keep the vessel from rupturing or leaking; this decreases transluminal pressure against the aneurysmal wall.
• Coils are not the only choice for embolization. Cyanoacrylates, onyx embolic material, gelfoam, polyvinyl alcohol, and others are also used.

• Supine
• Bilateral groins are prepped and draped for vascular access.
• Limited access to the patient due to fluoroscopy equipment (particularly if 3D images are obtained).

Bilateral percutaneous punctures are made in the groin to access femoral vessels.

Simple cases will be accomplished in 1–2 hours, while complex cases can take many hours.

• Usually minimal, on the order of 50–100 cc.
• In the event of aneurysm or AVM rupture during the procedure, there may be some blood loss, which has little hemodynamic consequences, but dire effects on the CNS. This may require emergent ventricular drain placement or even craniotomy for evacuation of hematoma and clipping of the aneurysm or AVM.
• There is a small risk of hidden retroperitoneal hematomas, which can become hemodynamically significant.

Patients are typically discharged home on postoperative day one after coiling for unruptured lesions. Others may require multiple-day hospitalizations as dictated by the patient's condition.

• Comprehensive fluoroscopy equipment with 3D capabilities and computer processing
• IV contrast dye
• Detachable coils or other embolization material

Incidence

• Incidence of subarachnoid hemorrhage (SAH) is 9 per 100,000 people annually.
• Up to 85% of cases of spontaneous SAH are due to ruptured aneurysms.
• Other causes of SAH are AVMs (~10%), cerebral hemorrhage (~10%), and others (e.g., tumors).
• Risk increases with age, family history, hypertension, heavy alcohol consumption, and smoking
• Most hemorrhages are from small aneurysms, although risk of rupture increases with increasing size.

Prevalence

About 1–2% of the population has at least one cerebral aneurysm.

• If the early course after aneurysm rupture is survived, 25% of patients will have significant restrictions in their lifestyle, and only 20% will have no residual symptoms.
• Other problems include long-term cognitive impairment, depression, fatigue, headache, PTSD, and hypopituitarism.

• Following a SAH, mortality can approach 50%.
• Unruptured aneurysms or AVMs who undergo uncomplicated procedures, generally do very well.

History

• Healthy patients for elective coiling need no special workup.
• A detailed history as to the presence of hypertension is sought.
• Contrast or shellfish allergy is elicited given the large amounts of contrast used.
• Heparin and protamine allergies should be noted.

Signs/Physical Exam

A thorough neurologic exam needs to be performed to assess the baseline status of the patient so it can be compared to the postprocedure exam. In this fashion, subtle changes can be picked up; allowing for further diagnostics and therapeutics to be pursued in a timely fashion.

Labs/Studies

• Hg/Hct to assess hemodilution during triple H therapy (hypertension, hemodilution, hypervolemia).
• Chemistry panel to assess for cerebral salt-wasting (hyponatremia and hypokalemia) due to the release of brain and atrial natriuretic hormone and SIADH.
• SAH can produce EKG changes including QT prolongation, Q waves, cardiac dysrhythmias, and signs consistent with acute ischemia.

• Healthy patients may be given premedication in usual fashion, with the caveat that heavy premedication and short cases may lead to delayed emergence and neurological assessment.
• Patients with altered sensorium or with increased ICP should be premedicated very carefully, if at all, as small changes in CO₂ tension can lead to large changes in ICP and obtundation.

Patients need to understand that there may be a need for prolonged intubation and the possibility for emergent craniotomy.

Usually no antibiotics are given.

• Local only, monitored anesthesia care, or general anesthesia may be appropriate.
• Local cases may be appropriate for otherwise healthy and very motivated patients with minimal risk for cerebral ischemia requiring emergent intubation.
• Monitored anesthesia care, again, should be reserved for healthy motivated patients. Sedation should be kept very light as to allow for patient communication and cooperation.
• General anesthesia (with endotracheal intubation) is chosen in most cases. Benefits include a motionless field, full airway control, control of hemodynamics and ICP, and control during complications (acute rupture, induction of barbiturate coma, treatment of seizures, and emergent craniotomy).

• Standard ASA monitors
• Foley catheter
• There should be a low threshold for placing an arterial line in patients with SAH from a ruptured aneurysm or AVM; if difficult to access, the operating physician can often provide access via the groin line.
• EEG monitoring and evoked potentials are not the standard of care, but should be considered in cases of giant and wide neck aneurysms, aneurysm in close proximity to other vessels, high ICP, large SAH, or who are otherwise at risk for cerebral ischemia.

• Management of ICP, BP, cerebral perfusion pressure (CPP), and the airway are the main concerns during induction.
• Patients with unruptured aneurysms and AVMs rarely have high ICP. Maintaining a stable BP with minimal variation is more important than an absolute number. Patients with recently ruptured aneurysms or AVMs should have their BP controlled at, or slightly below, normal levels to avoid rebleeding. If the ICP is increased, a drop in BP can cause CPP to become marginal. Intracranial hypertension may be controlled with mannitol, hyperventilation, furosemide, and decreasing or discontinuing volatile anesthetics (convert to a propofol, dexmedetomidine, and/or opioid technique).
• Patients at risk for vasospasm on "triple H (hypertension, hemodilution, hypervolemia)" therapy need to have their BP maintained in the high normal range to avoid cerebral ischemia. This is accomplished with a combination of pressors and volume.

• Unless ICP cannot be controlled with the methods described, a balanced anesthetic with low levels of volatile anesthetics can be employed.
• There is no evidence that any particular anesthetic is superior to another for uncomplicated cases.
• Movement must be avoided utilizing either deep anesthesia or paralysis, especially during critical coil positioning and deployment. Coil positioning and deployment is usually not painful, but when work is performed close to the dura, thalamus, or certain parts of the brainstem (e.g., during AVM embolization), the patient may move.
• Coagulation management with heparin and other agents may be required to prevent intraoperative thromboembolic events; this may need to be reversed at the conclusion of the case. Protamine reversal is often done with a small "test dose" to assess for allergic or anaphylactic reactions followed by slow titration to avoid hypotension.

• Naturally, emergence should be smooth.
• Endotracheal lidocaine may be administered at the beginning of the case during laryngoscopy. Alternatively, IV lidocaine may be given at the end to reduce tracheal reflexes.
• Aggressive multimodal emesis prophylaxis.