Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 58, Num. 4, 2010, pp. 571-575

Neurology India, Vol. 58, No. 4, July-August, 2010, pp. 571-575

Original Article

Intraoperative angiography in aneurysm surgery: An initial experience

Pai BalajiS, Muralimohan S

Department of Neurosurgery, Columbia Asia Referral Hospital, Yeshwanthpur, Bangalore - 560 055
Correspondence Address:747, 14th Cross, Girinagar II Phase, Bangalore - 560 085, balajipai65@yahoo.co.in

Date of Acceptance: 01-Feb-2010

Code Number: ni10150

PMID: 20739794

DOI: 10.4103/0028-3886.68681

Abstract

Keywords: Aneurysm surgery, aneurysmal neck remnant, cerebral angiography, intraoperative angiography

Introduction

The surgical clipping of a cerebral aneurysm may be complicated by aneurysmal neck remnant or compromise of adjacent cerebral vasculature. Intraoperative impression of the surgeon regarding the efficacy of clipping is subjective and requires extensive experience. ^[1] Postoperative cerebral angiography is useful in detecting such complications, but reparative action if possible would require another intervention. In the case of vascular compromise, permanent ischemic neuronal damage would result, making any intervention irrelevant. Hence intraoperative angiography (IOA) assumes an important role in the prevention of these unwanted complications. IOA has been available since the 1960s, though its advantages and efficacy have been debated. ^[2],[3] The postoperative rupture and subsequent mortality of a patient with undetected incompletely obliterated anterior communicating artery aneurysm [Figure - 1] prompted the senior author to introduce IOA routinely in all cases of aneurysm surgery. We report our initial experience with 20 consecutive patients who had aneurysmal clipping followed by IOA.

Materials and Methods

IOA was performed in 20 consecutive patients with cerebral aneurysm who underwent surgical clipping. All these patients had undergone preoperative digital subtraction angiography (DSA), which apart from giving necessary details of aneurysmal morphology and its relationship to vasculature, also revealed information about the anatomy of the aortic arch and its branches and their tortuosity. A note was made of the catheters used to enter the concerned artery and the view in which the aneurysm neck and its surrounding vasculature were best appreciated. This was duplicated during the IOA.

IOA requirements included: radiolucent operating table, C-arm with DSA mode, puncture needle (18/16G), 5F femoral sheath, H1 guiding catheter, guide wire, non-ionic contrast medium and pressure infusion bag.

Procedure

After surgical clipping of the aneurysm and before closure, IOA was performed in all the 20 patients. We used the image intensifier with DSA compatibility and radiolucent operating table. Using the Seldinger technique the right femoral artery was cannulated and a 5F sheath inserted. A pressure infusion of saline was connected to the sheath to prevent blockage; 2500-3000 units of heparin was administered intravenously at this stage. The femoral artery was cannulated just prior to the introperative angiogram. In ten patients a pre-clipping IOA was done. However, the authors later have given up this practice. In such patients the femoral artery was cannulated just after the aneurysm was clipped. Heparin was administered intravenously at this stage. and the anticoagulation effect of the same might be lost if the femoral artery was cannulated too early necessitating repeating the dose of heparin. The guiding catheter was then navigated to the concerned artery using fluoroscopic guidance. Care had been taken to remove all metal objects from the area of exposure. Once the appropriate artery was catheterized, the C-arm was moved into a position corresponding to the best view noted in the preoperative angiogram. Using the DSA mode, various runs were taken and compared with preoperative images. Obliteration of the aneurysm and the patency of all the adjacent vessels were confirmed. Any clip adjustment if required was done and then angiogram repeated. The catheter was removed and the craniotomy wound closed after securing perfect hemostasis. The sheath was removed after the surgery, once the patient was shifted to the intensive care unit (ICU). Cerebral protection in the form of propofol infusion was administered during the entire intradural dissection and clipping of the aneurysm. This was discontinued once the IOA had yielded satisfactory results. Additional cerebral protection in the form of mannitol, steroids and hypertension was instituted if temporary clipping was carried out.

Results

In all the 20 patients, obliteration of the aneurysm was confirmed by IOA [Figure - 2]. In two patients, compramization of the adjacent vessels was noted necessitating clip repositioning. The first patient was with an anterior communicating artery (AComA) aneurysm, where the distal end of the clip was seen to obstruct the contralateral frontopolar artery [Figure - 3]. In the second patient, the superior trunk of the middle cerebral artery was seen to be sub-totally blocked by a clip applied to obliterate a wide-necked middle cerebral artery bifurcation aneurysm. A repeat angiogram done after clip repositioning confirmed aneurysm obliteration with no adjacent vessel compromise. In both instances reflow was established within 15-20 min. No postoperative strokes were noted in the postoperative scans. Both the patients did not reveal any neurological deficit attributable to the transient ischemia. There were no changes in the routine intraoperative monitoring parameters in the two patients with temporary vessel occlusion.

Some degree of vasospasm was generally noted due to vessel handling during surgery. Administration of intra-arterial nimodipine to alleviate severe radiological vasospasm was performed in four patients and significant improvement was noted in two patients. The time taken for an IOA varied from 30 min to 45 min. Catheterization of the left internal carotid artery (ICA) was sometimes difficult, but with patience this could be achieved in all the patients. No complications (embolic, dissection or hemorrhagic) attributable to IOA were encountered. Perfect hemostasis at the operative site could be easily achieved in spite of intravenous heparin during IOA. [Table - 1] summarizes the results.

Discussion

The reported frequency of remnant aneurysmal neck varied from 3.8% to 18% and risk of recurrent hemorrhage was 33% with small neck remnants and 54% with large neck remnants. ^{[4],[5],[6],[7],[8],[9]} Sindou et al., have classified the aneurysmal neck remnants into four grades and also described the treatment for the same. ^[9] The surgeon′s visual impression and aneurysmal dome puncture are two means to confirm complete aneurysmal occlusion. Neither of these two are optimal measures to confirm complete aneurysmal obliteration. The reported frequency of occlusion of the parent vessel varied between 3% and 9% and this may be associated with permanent neurological deficit or death. ^[4],[6] Only a small window of time exists before this complication can be recognized and restorative action is taken. Aneurysm size and location have been reported to influence substantially the adequacy of aneurysmal clipping and vascular compromise. Large and giant aneurysms have been associated with a higher incidence of these complications. ^[2],[8] Adequacy of clipping and vascular compromization may depend on the location of the aneurysm. The aneurysms that may be associated with suboptimal clipping include: superior hypophyseal (SHA), internal carotid artery (ICA) bifurcation, superior cerebellar arteries, and paraclinoidal. ^[8],[10] Alexander et al.,[11] have noted posterior communicating artery location, and Chiang et al.,[2] have found anterior communicating artery location as the site for unexpected IOA findings. We feel that the pterional approach to the AComA aneurysm may sometimes result in inadequate clipping or contralateral vascular compromise due to inadequate visualization of contralateral vasculature. This may be avoided with judicious usage of the neuroendoscope. Morphology of the aneurysm like multi-lobulated structure may also result in suboptimal clipping.

IOA has been considered since 1960s ^[3] and it can demonstrate both incomplete aneurysm occlusion and parent vessel compromise in a facile and timely manner. This may lead to early intraoperative corrective intervention, thus improve surgical outcome. ^[4] It is possible in the same sitting to administer intra-arterial medications to alleviate vasospasm, if seen during IOA. The authors have injected intra-arterial nimodipine in four patients with radiologically detected severe cerebral vasospasm during IOA.

Suzuki et al.[12], have described a noninvasive and effective technique of intraoperative aneurysmal obliteration and vascular patency using fluorescein angiography by injecting 5 ml of 10% fluorescein sodium intravenously. Raabe et al. ^[13] , and Wang et al.[14], have studied intraoperative blood flow using indocyanine green angiography (ICG). A microscope-integrated light source containing infrared excitation light illuminated the operating field. The dye ICG was injected intravenously, and the intravascular fluorescence was recorded by a video camera attached to the microscope with optical filtering to block ambient and laser light for collection of only ICG-induced fluorescence.

Analyses of postoperative angiography have shown that the overall need for clip re- adjustment ranges from 4-21%. ^{[2],[11],[15],[16]} There has been considerable debate regarding the routine use of IOA or on a selective basis. Recently, a number of studies have evaluated the routine use of IOA in cerebral aneurysm surgery. ^{[1],[2],[4],[8]} The most common strategy of selective use of IOA for aneurysm surgery is partially based on the belief that the operating surgeon can predict when it is required and is of use. ^[8] The opinion is more in favor of routine IOA as the surgeon′s opinion alone may be insufficient to predict adequacy of clip placement. ^[2] Origitano et al. ^[14] , have found the incidence ranging from 3% to 18%. Incidence of IOA leading to clip revision varied from 11% to 33% in various series. ^[8],[17] In a large series of IOA in 517 consecutive aneurysms, Tang et al.[8], have noted 12.4% incidence of clip revision following IOA.

The potential advantages must be weighed against the technical difficulties and complications. The reported complication rate varied between 0.4% to 3% ^[x] and the complications include: stroke, dissection, embolism and hemorrhage. Eventhough this complication rate is higher than the complication rate associated with conventional cerebral angiography, it still compares favorably with the intraoperative clip revision rates and the outcome. Technical challenges of IOA include need for skilled neuro-radiology staff in the operative room (OR), requirement of a DSA C-arm, radiolucent operating table and catheters. Increased traffic in the operating room during IOA may also be a deterrent. The extra time required for IOA can be reduced with routine use and training of the operating room (OR) and radiology staff. In our study the extra time for IOA was generally 30 min with an additional 15 min for intra-arterial nimodipine administeration. The extra time taken also assured perfect hemostasis in the surgical field. Mihara et al., have suggested a continuous infusion of heparin at 3 ml/h, of a solution of 1 liter of saline containing 8000 units of heparin in an attempt to reduce the total dose of heparin to the patient during IOA. The authors, however, use a bolus dose of 2500-3000 units after insertion of the femoral sheath. ^[18]

In this study some degress of vasospasm was seen in the post-clipping IOA in most of the patients. Such an observation has not been documented in the earlier studies. We are not in a position to offer a good explanation for this phenomenon. Timing of surgery is unlikely to be the cause as these findings were seen the post-clipping IOA and not in the pre-clipping IOA done 2-3 h before [Figure - 2]. The authors hypothesize that surgical dissection of the parent vessel could result in some kind of transient vasospasm. Other possible explanation would be that exposing the vessels to the atmospheric pressure during the operation could result in transient decrease in lumen reduction. Patients who recived intraarterial nimodipine were the patients with severe vasospasm obvious in the preoperative angiogram.

IOA is a safe and effective adjunctive tool for aneurysm clipping. The potential ability to detect aneurysmal remnant and vessel compromise outweighs the complications and technical difficulties of IOA. We recommend the routine use of IOA in all cases of aneurysm surgery. Optimal speed, reliability and efficacy of IOA can only be achieved within an institution when its use is routine.

References

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