Surgical considerations and complications

The goals of aneurysm surgery following SAH are: (1) aneurysm obliteration with preservation of normal vasculature; and (2) minimisation of brain tissue disruption (Figures 8.2, 8.3). Our patients undergoing uncomplicated aneurysm repair following SAH had morbidity and mortality rates of approximately 10%. When intraoperative rupture occurred, the morbidity and mortality rates increased to approximately 20%. Factors such as the phase of the dissection, the use of blunt versus sharp dissection techniques, and complete aneurysm neck dissection play key roles in minimising intraoperative rupture. Adequate depth of anaesthesia, strict blood pressure control, ventricular drainage at the time of surgery, aggressive sphenoid wing removal, and appropriately situated craniotomies which permit minimal brain retraction will aid in reducing the incidence of aneurysm rupture prior to subarachnoid dissection.

The most frequent time for intraoperative aneurysm rupture is during subarachnoid dissection prior to clip application.175-177 In our experience, ill advised blunt dissection techniques are the most frequent cause of intraoperative rupture. Aneurysm rupture produced by blunt

Figure 8.2 AP vertebral arteriogram demonstrating basilar apex aneurysm

dissection typically produces a large tear at the aneurysm sac-neck junction and the amount of bleeding is usually torrential. Bleeding from sharp dissection is usually from punctate holes and, therefore, more controllable. To reduce the risk of rupture, dense clot surrounding the vessels and the aneurysm should be sharply divided with microscissors or microarachnoid knives. Dissection should also hug the normal vasculature when working in the aneurysm's vicinity. Early proximal and distal vascular control prior to aneurysm dissection is mandatory in all cases. Definitive neck dissection prior to clip application will also reduce the likelihood of clip induced aneurysm rupture which is similar to aneurysm rupture from blunt dissection.

Intraoperative aneurysm rupture is an inevitable complication of aneurysm surgery. Close blood pressure control, basal craniotomy flaps, minimal brain retraction, strict use of sharp dissection techniques, dissection along normal vascular anatomy, temporary occlusion of parent

Figure 8.3 AP vertebral arteriogram of basilar apex aneurysm which has been successfully clipped with sparing of both posterior cerebral arteries

vessels, and appropriate use of available clips can minimise the incidence of intraoperative rupture and provide the optimal chance for a good surgical outcome.

In the event of intraoperative aneurysm rupture, temporary occlusion of afferent and efferent vessels is one of the most useful measures. We utilise pentothal induced electroencephalographic burst suppression during temporary occlusion to theoretically optimise cerebral protection.178 We do not use induced hypotension to control intraoperative aneurysm rupture because of the theoretically deleterious effects of hypotension on patients specifically susceptible to acute ischaemia. Giannotta found that induced hypotension negatively influenced outcomes when used to control intraoperative aneurysm rupture.177

During surgery, we attempt to remove as much subarachnoid clot as is deemed safe. The variable consistency of acute and subacute subarachnoid blood at various stages of fibrinolysis renders success of clot removal unpredictable. Previous reports have found some potential benefit in preventing vasospasm or lessening its severity by aggressive subarachnoid clot removal.172,173 Recent reports have focused on the use of topical thrombolytic agents such as tissue-type plasminogen activator (tPA) instilled into the subarachnoid space during surgery. Use of tPA has been reported to show some effect on chemical thrombolysis of subarachnoid clot in the postoperative period.166,169,179 184 In our limited experience, tPA does appear to aid in the clearance of subarachnoid blood seen on CT scan. Whether this chemically induced thrombolysis will be beneficial in decreasing the morbidity and mortality of vasospasm remains to be demonstrated. The addition of tPA at surgery carries some risk of increased bleeding in the operative site postoperatively.

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