S

Abbreviation: GCS, Glasgow Coma Scale.

Timing of surgery is essential in achieving optimal outcome, and the time course of vasospasm is the major consideration. "Early surgery" has been advocated for several obvious practical reasons. Prompt clipping of an aneurysm eliminates the risk of rebleeding, which is theoretically associated with increased morbidity and mortality. Also, once an aneurysm is secured, treatment of vasospasm is facilitated with the use of triple-H therapy (hypertension, hypervolemia, and hemodilution), an option that is dangerous in an unsecured aneurysm. Vasospasm and edema may complicate surgery that is delayed from 7 to 10 days after aSAH, when vasospasm is at its peak. Another surgical option is that of "late surgery," in which clipping is accomplished after 12 to 14 days, when vasospasm has resolved and edema has subsided. The Cooperative Study on the Timing of Aneurysm Surgery showed that the results of early surgery were equivalent to those of late surgery (26,27). This was a prospective observational study involving 3521 patients from 60 centers collected over a period of 2.5 years. Comparably good outcomes were reported for surgery that was performed on days 0 to 3 (63%) and days 4 to 6 (60%) post-aSAH. Delayed surgery on days 11 to 14 post-aSAH also yielded similar results (62%), as did late surgery on days 15 to 32 (63%). Surgery during days 7 to 10 after aSAH had the worst outcome, and this period coincides with the peak of vasospasm.

The intraoperative dissection technique is crucial for aneurysm clipping. Using an operating microscope, dissection should focus on sharply separating arachnoid tissues to facilitate separation of vascular structures from the parenchyma. The first goal of the dissection is to gain proximal control. Prior to attempting dissection near the aneurysm, the surgeon must be able to emergently occlude the vessel that supplies the aneurysm in the case of an intraoperative rupture. In cases in which intracranial proximal control is not an option (e.g., ophthalmic artery aneurysms), an extracranial neck dissection for proximal control is required prior to the craniotomy. Blunt dissection should be avoided, especially near the aneurysm due to the high risk of tearing the frail dome. Also, a blunt tear is much more difficult to repair than a punctate tear made using sharp dissection techniques. Once the aneurysm is reached, meticulous dissection of the aneurysm neck is required, to ensure optimal clip placement and to reduce iatrogenic rupture of the aneurysm.

Temporary arterial occlusion is a useful option to aid in the surgical dissection and, ultimately, in the clipping of aneurysms. This technique, when used properly, can reduce the risk of intraoperative rupture when dissecting near the aneurysm, can facilitate optimal placement of the permanent clip, and is indicated in cases where more involved neck dissection is required and those in which extensive adhesions are located near the aneurysm. Prior to applying temporary clips, hemodynamic status must be stable and the patient's intravascular volume and systemic blood pressure should be normalized (higher blood pressure should be maintained for hypertensive patients). The patient should be anesthetized to electroencephalographic burst suppression. The temporary arterial occlusion should be applied with a "temporary clip" that has a closing pressure approximately half that of a permanent clip. This will decrease the risk of intimal damage to the vessel. Although the exact placement of the temporary clip is case specific, the general guideline is that it should allow maximal aneurysm exposure while minimizing the risk of infarction.

The technique used in treating the aneurysm is as important as the dissection and application of the clip. Clip selection is crucial in excluding the aneurysm from the systemic circulation. Careful measurement of the aneurysm on the angiogram should be correlated with the intraoperative findings. The clip size should be at least 1.53 x the diameter of the aneurysm, as application of the clip will lead to collapse and elongation of the neck of the aneurysm. In certain circumstances, application of a clip is not possible due to the anatomy or shape of the aneurysm. An alternative maneuver is wrapping the aneurysm, although the outcome of this technique is debatable. In another technique, called "trapping," clips are placed proximal and distal to the aneurysm to interrupt flow. Depending upon the anatomic location, this procedure can be associated with ischemic sequelae.

Post-clipping protocol is as important as pre-clipping protocol. Once the clip is in place, careful visual inspection must be made to ensure that optimal placement has occurred and no other vessels are compromised, especially in cases where the clip is placed too close to the parent vessel, decreasing its diameter. Papaverine is applied to all exposed and manipulated arteries to facilitate redilatation to premanipulation diameters. Then, intraoperative angiography is performed to ensure proper clip placement. Improper clip placement that requires reexploration and clip adjustment was seen on intraoperative angiography in 11% of the cases in one study (28).

Endovascular intervention for aneurysms is a more recent technique and is a promising minimally invasive option for the treatment of aneurysms. Endovascular interventional neuroradiology began in the 1970s, when Fedor Serbinenko used detachable latex balloons to occlude the supplying artery of the aneurysm or to occlude the aneurysm sac itself (29). Modern endovascular treatment of aneurysms started in 1991, when Guido Guglielmi introduced an electrolytic detachable platinum coil (Guglielmi detachable coils) (30,31). These coils are inserted through a femoral artery cannula via a microcatheter that can be threaded to the location of the aneurysm. The coils are then packed into the saccular portion and separated from the microcatheter by electrolysis, thus excluding the aneurysmal sac from cerebral circulation.

The use of endovascular coiling for the treatment of aneurysms is rapidly increasing worldwide, which is a reflection of improved coil design and refinements of techniques, as more centers subspecialize in this area. A few centers are reserving surgery as a back-up option when coiling is deemed unsuitable. It is estimated that approximately 1500 patients worldwide per month are being treated by endovascular coiling, and more than 100,000 patients with aneurysms have been treated with endovascular coiling (32 ).

The level of expertise at the neurosurgical center is a crucial determinant of outcome in patients who undergo surgical treatment of aneurysms, especially clipping. Microsurgical techniques of aneurysmal clipping are technically demanding and usually are not employed for most neurosurgical cases. The neurosurgical centers that treat the average patient population without a referral bias would typically not encounter a high volume of aneurysm patients, thus limiting the experience of the surgeons. A study on the effects of patient volume on the outcome of craniotomy and aneurysmal clipping showed that institutions that performed more than 30 craniotomies per year had a 43% reduction in mortality rates. Also, centers that performed more than 30 aneurysm clippings per year had a 43% reduction in mortality rates (33). Similar results have been noted in other studies, suggesting that patients with aSAH will have improved outcome if their surgery is performed at a high-volume institution.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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