Aneurysm Clip Ligation Research Articles

A Step-by-Step Dissection of Cerebral Pathologies for Neurosurgical Trainees: The Middle Cerebral Artery Bifurcation Aneurysm.

Aneurysmal subarachnoid hemorrhage remains one of the most prevalent causes of strokes in the young causing a high socioeconomic damage. Both emergent and elective treatments of intracranial aneurysms remain essential challenges for neurovascular centers. We aim to present conceptual education on clip ligation of middle cerebral artery bifurcation aneurysms in an accessible and structured way to maximize the educational takeaway of residents from aneurysm cases. After 30 years of experience of the senior author in cerebrovascular surgery in three centers, we closely reviewed an exemplary case of elective right middle cerebral artery bifurcation aneurysm clipping and contrasted it to an alternative microneurosurgical approach to illustrate key principles of microneurosurgical clip ligation for neurosurgical trainees. Dissection of the sylvian fissure, subfrontal approach to the optic-carotid complex, proximal control, aneurysm dissection, dissection of kissing branches, dissection of aneurysm fundus, temporary and permanent clipping, as well as aneurysm inspection and resection are highlighted as key steps of clip ligation. This proximal-to-distal approach is contrasted to the distal-to-proximal approach. Additionally, general principles of intracranial surgery such as use of retraction, arachnoid dissection, and draining of cerebrospinal fluid are addressed. Due to a constantly decreasing case load in the era of neurointerventionalism, the paradox of facing increased complexity with decreased experience must be met with a sophisticated practical and theoretical education of neurosurgical trainees early on and with a low threshold.

Identification and surgical ligation of spinal CSF-venous fistula.

Background: CSF-venous fistulas (CVF) may cause incapacitating positional headaches resulting from spontaneous intracranial hypotension/hypovolemia (SIH). Their etiology remains unknown, although unrecognized local trauma may precipitate SIH. In addition, they are diagnostically challenging despite various imaging tools available. Here, we present CVF identification using magnetic resonance myelography (MRM) and elaborate on their surgical management techniques.Methods: Retrospective charts of confirmed and treated CVF patients with attention to their diagnostic imaging modalities and management techniques were further reviewed.Results: Six cases were identified of which three are presented here. There were two females and one male patient. All had fistulas on the left side. Two were at T7-T8 while the third was at T9-T10 level. Two underwent hemilaminotomies at the T7-T8 while the third underwent a foraminotomy at T9 level to access the fistula site. All CVF were closed with a combination of an aneurysm clip and a silk tie. On follow-up, all had complete resolution of symptoms with no evidence of recurrence.Conclusion: Of the various imaging modalities available, MRM is particularly sensitive in localizing CVF spinal nerve level and their laterality. In addition, the technique of aneurysm clip ligation and placement of a silk tie is curative for these lesions.

Initial Experience with Transradial Intraoperative Angiography in Aneurysm Clipping: Technique, Feasibility, and Case Series

The transradial approach has slowly been gaining momentum in neuroendovascular procedures. We sought to assess its feasibility and safety and present a case series of transradial intraoperative angiography (IOA) during microsurgical clip ligation of intracranial aneurysms. The setup and technique for transradial intraoperative angiography are described. Data on 10 consecutive patients undergoing IOA through the radial artery are presented. All target vessels were successfully catheterized transradially, and conversion to the transfemoral access was not required in any of the cases. There was no access-site complication, such as hand ischemia, hematoma, or radial artery spasm. There were also no thromboembolic events causing a stroke. The average time for the IOA was 9.3 minutes. Our initial experience shows the transradial approach for IOA in clip ligation of aneurysms to be feasible and safe, with potential advantages over transfemoral IOA.

Adenosine-induced Flow Arrest to Facilitate Intracranial Complex Aneurysm Clip Ligation: Review of the Literature.

Complex intracranial aneurysms (CIAs) rank high among the most technically demanding neurosurgical pathologies. Microsurgery and clip ligation can be challenging in CIAs as circumferential visualization of the aneurysm, parent vessels, branches, perforators, and other neurovascular structures is important to prevent residual aneurysms or strokes from vessel or perforator occlusion. Decompression of the aneurysm sac is often required for CIAs. We reviewed the literature and PubMed advanced search showed 13 results of adenosine-induced flow arrest to facilitate intracranial complex aneurysm clip ligation which included three independent case reports and ten cases in a case series from 1999 to May 2016. Few case series have described the use of adenosine in intracranial aneurysm surgery. Satisfactory aneurysm decompression was achieved in all cases, and all aneurysms were clipped successfully. We recommend that adenosine cardiac arrest is a relatively novel method for decompression of intracranial aneurysms to facilitate clip application. With appropriate safety precautions, it is a reasonable alternative method when temporary clipping of proximal vessels is not desirable or not possible.

Expression of c-kit and Cytokeratin 5 in the Submandibular Gland after Release of Long-Term Ligation of the Main Excretory Duct in Mice.

Long-term submandibular duct obstruction is thought to cause irreversible atrophy and dysfunction of the submandibular gland. As an atrophic gland may be induced clinically by chronic or recurrent infection, it is generally removed surgically. However, the regenerative capacity of atrophic submandibular glands after long-term obstruction is not completely understood. We studied the regenerative capacity of the mouse submandibular duct using an aneurysm clip ligation model. We documented changes in the size, histologic structure and gene expression of the submandibular gland after 2 months of ligation, and 1 week, 1 month and 2 months after clip removal. Two months of ligation caused atrophy, particularly in the acinar portion. In the 2 months after clip removal, we observed a steady and significant increase in the expression of the acinar cell precursor gene cytokeratin 5 (CK5), and a significant decrease in the expression of the stem cell marker c-kit. These findings suggest that the submandibular gland retains some capacity for regeneration even after long-term obstruction, and that CK5 could serve as a marker of this regenerative process.

Use of a surgical rehearsal platform and improvement in aneurysm clipping measures: results of a prospective, randomized trial.

OBJECTIVE The field of neurosurgery is constantly undergoing improvements and advances, both in technique and technology. Cerebrovascular neurosurgery is no exception, with endovascular treatments changing the treatment paradigm. Clipping of aneurysms is still necessary, however, and advances are still being made to improve patient outcomes within the microsurgical treatment of aneurysms. Surgical rehearsal platforms are surgical simulators that offer the opportunity to rehearse a procedure prior to entering the operative suite. This study is designed to determine whether use of a surgical rehearsal platform in aneurysm surgery is helpful in decreasing aneurysm dissection time and clip manipulation of the aneurysm. METHODS The authors conducted a blinded, prospective, randomized study comparing key effort and time variables in aneurysm clip ligation surgery with and without preoperative use of the SuRgical Planner (SRP) surgical rehearsal platform. Initially, 40 patients were randomly assigned to either of two groups: one in which surgery was performed after use of the SRP (SRP group) and one in which surgery was performed without use of the SRP (control group). All operations were videotaped. After exclusion of 6 patients from the SRP group and 9 from the control group, a total of 25 surgical cases were analyzed by a reviewer blinded to group assignment. The videos were analyzed for total microsurgical time, number of clips used, and number of clip placement attempts. Means and standard deviations (SDs) were calculated and compared between groups. RESULTS The mean (± SD) amount of operative time per clip used was 920 ± 770 seconds in the SRP group and 1294 ± 678 seconds in the control group (p = 0.05). In addition, the mean values for the number of clip attempts, total operative time, ratio of clip attempts to clips used, and time per clip attempt were all lower in the SRP group, although the between-group differences were not statistically significant. CONCLUSIONS Preoperative rehearsal with SRP increased efficiency and safety in aneurysm microsurgery as demonstrated by the statistically significant improvement in time per clip used. Although the rest of the outcomes did not demonstrate statistically significant between-group differences, the fact that the SRP group showed improvement in mean values for all measures studied suggests that preoperative rehearsal may increase the efficiency and safety of aneurysm microsurgery. Future studies aimed at improving patient outcome and safety during surgical clipping of aneurysms will be needed to keep pace with the quickly advancing endovascular field.

A long-term study of durability and risk factors for aneurysm recurrence after microsurgical clip ligation.

OBJECTIVE With the recent evolution of endovascular therapies, objective evaluation of the efficacy of clip ligation for cerebral aneurysms should be performed. This study was undertaken to evaluate the durability of microsurgical clip ligation, identify risk factors for recurrence, and assess the need for long-term follow-up imaging. METHODS A retrospective review of medical records identified 616 consecutive patients (156 male and 460 female patients; mean age 48.4 ± 12.4 years; range 6-90 years) who underwent microsurgical clip ligation and follow-up imaging at least 1 year after discharge between 1990 and 2010 at our institution. Of a total of 926 aneurysms in 616 patients, 758 aneurysms were microsurgically clip-ligated. At presentation, 431 of these aneurysms were ruptured and 327 aneurysms were unruptured. All patients underwent postoperative baseline imaging within the 1st month of their operation. A logistic regression analysis was performed to identify which variables are more likely to predict recurrence. RESULTS Late follow-up angiographic imaging was obtained at a mean of 7.2 ± 4.7 years postdischarge (median 5.7 years; range 1-23 years). Of the 699 clipped aneurysms without residua, late follow-up angiography revealed only 1 (0.14%) recurrent aneurysm. Of the 59 residual aneurysms that remained after initial clip ligation on early postoperative imaging, 8 (13.6%) demonstrated growth. All of these aneurysms required treatment. None of the recurrences were due to broken or delayed displacement of clips. A total of 111 patients presented with multiple aneurysms. De novo aneurysm formation occurred in 8 (0.97%) patients, all of whom initially presented with multiple aneurysms. CONCLUSIONS This study provides additional evidence to support the long-term efficacy of aneurysm clip ligation. The chance of aneurysm recurrence after complete clip ligation is very small. However, there is a regrowth risk of 1.83% per year for aneurysm remnants after incomplete clip ligation. These findings support the necessity for continued followup, late angiographic imaging, and the potential need for further intervention of incompletely ligated aneurysms. Furthermore, completely clip-ligated aneurysms may not require additional surveillance imaging unless multiple aneurysms were evident at presentation.

Minimally Invasive Thumb-sized Pterional Craniotomy for Surgical Clip Ligation of Unruptured Anterior Circulation Aneurysms.

Less invasive surgical approaches for intracranial aneurysm clipping may reduce length of hospital stay, surgical morbidity, treatment cost, and improve patient outcomes. We present our experience with a minimally invasive pterional approach for anterior circulation aneurysms performed in a major tertiary cerebrovascular center and compare the results with an aged matched dataset from the Nationwide Inpatient Sample (NIS). From August 2008 to December 2012, 22 elective aneurysm clippings on patients ≤55 years of age were performed by the same dual fellowship-trained cerebrovascular/endovascular neurosurgeon. One patient (4.5%) experienced transient post-operative complications. 18 of 22 patients returned for follow-up imaging and there were no recurrences through an average duration of 22 months. A search in the NIS database from 2008 to 2010, also for patients aged ≤55 years of age, yielded 1,341 hospitalizations for surgical clip ligation of unruptured cerebral aneurysms. Inpatient length of stay and hospital charges at our institution using the minimally invasive thumb-sized pterional technique were nearly half that of NIS (length of stay: 3.2 vs 5.7 days; hospital charges: $52,779 vs. $101,882). The minimally invasive thumb-sized pterional craniotomy allows good exposure of unruptured small and medium-sized supraclinoid anterior circulation aneurysms. Cerebrospinal fluid drainage from key subarachnoid cisterns and constant bimanual microsurgical techniques avoid the need for retractors which can cause contusions, localized venous infarctions, and post-operative cerebral edema at the retractor sites. Utilizing this set of techniques has afforded our patients with a shorter hospital stay at a lower cost compared to the national average.

Minimally Invasive Thumb-sized Pterional Craniotomy for Surgical Clip Ligation of Unruptured Anterior Circulation Aneurysms

Minimally Invasive Thumb-sized Pterional Craniotomy for Surgical Clip Ligation of Unruptured Anterior Circulation Aneurysms

Endoscopic endonasal clip ligation of cerebral aneurysms: an anatomical feasibility study and future directions.

The expansion of endovascular procedures for obliteration of cerebral aneurysms highlights one of the drawbacks of clip ligation through the transcranial route, namely brain retraction or brain transgression. Sporadic case reports have emerged over the past 10 years describing endonasal endoscopic clip ligation of cerebral aneurysms. The authors present a detailed anatomical study to evaluate the feasibility of an endoscopic endonasal approach for application of aneurysm clips. Nine human cadaveric head specimens were used to evaluate operative exposures for clip ligation of aneurysms in feasible anterior and posterior circulation locations. Measurements of trajectories were completed using a navigation system to calculate skull base craniectomy size, corridor space, and the surgeon's ability to gain proximal and distal control of parent vessels. In each of the 9 cadaveric heads, excellent exposure of the target vessels was achieved. The transplanum, transtuberculum, and transcavernous approaches were used to explore the feasibility of anterior circulation access. Application of aneurysm clips was readily possible to the ophthalmic artery, A1 and A2 segments of the anterior cerebral artery, anterior communicating artery complex, and the paraclinoid and paraclival internal carotid artery. The transclival approach was explored, and clips were successfully deployed along the proximal branches of the vertebrobasilar system and basilar trunk and bifurcation. The median sizes of skull base craniectomy necessary for exposure of the anterior communicating artery complex and basilar tip were 3.24 cm(2) and 4.62 cm(2), respectively. The mean angles of surgical corridors to the anterior communicating artery complex and basilar tip were 11.4° and 14°, respectively. Although clip placement was feasible on the basilar artery and its branches, the associated perforating arteries were difficult to visualize, posing unexpected difficulty for safe clip application, with the exception of ventrolateral-pointing aneurysms. The authors characterize the feasibility of endonasal endoscopic clip ligation of aneurysms involving the paraclinoid, anterior communicating, and basilar arteries and proximal control of the paraclival internal carotid artery. The endoscopic approach should be initially considered for nonruptured aneurysms involving the paraclinoid and anterior communicating arteries, as well as ventrolateral basilar trunk aneurysms. Clinical experience will be mandatory to determine the applicability of this approach in practice.

Adenosine-Induced Flow Arrest to Facilitate Intracranial Aneurysm Clip Ligation Does Not Worsen Neurologic Outcome

Bebawy, John F.; Zeeni, Carine; Sharma, Sonal; Kim, Edina S.; de Wood, Mark S.; Hemmer, Laura B.; Ramaiah, Vijay K.; Bendok, Bernard R.; Koht, Antoun; Gupta, Dhanesh K. Author Information

Adenosine-Induced Flow Arrest to Facilitate Intracranial Aneurysm Clip Ligation Does Not Worsen Neurologic Outcome

When temporary arterial occlusion of the parent artery is difficult for anatomical reasons, or when inadvertent aneurysmal rupture occurs during surgical dissection, adenosine administration can be used to produce flow arrest and brief, profound systemic hypotension that can facilitate intracranial aneurysm clip ligation. There is a concern, however, that the flow arrest and profound hypotension produced by adenosine, although brief, may cause cerebral ischemia and therefore worsen neurologic outcome compared with other techniques to facilitate aneurysm clip ligation. Therefore, we performed a retrospective, case-control study to determine whether adenosine-induced flow arrest had negative effects on the neurologic outcome of our patients. We reviewed the perioperative records of all patients in our intracranial aneurysm surgery outcomes database between August 1, 2006, and June 15, 2012. The primary outcome was the presence or absence of a poor neurologic outcome 48 hours after surgery, with a modified Rankin scale score >2 being defined as a poor neurologic outcome. The neurologic outcome at the time of hospital discharge was a secondary outcome. Secondary outcomes related to cardiac morbidity included atrial or ventricular arrhythmia requiring treatment and elevated cardiac biomarkers consistent with ischemia (i.e., Troponin-I). During the study period, adenosine-induced flow arrest was used in 72 of the 413 patients (17.4%) who underwent intracranial aneurysm clip ligation. The difference in the incidence of poor neurological outcome, with or without the use of adenosine, was no larger than 15.7% at 48 hours after surgery (P =0.524) or -12.7% at discharge (P = 0.741). In addition, the difference in the incidence of cardiac morbidity was no larger than -16.0% for persistent arrhythmia (P = 0.155) or -9.4% for biomarkers of myocardial ischemia (P = 0.898) in the initial 48 hours after surgery. When used to facilitate intracranial aneurysm clip ligation, adenosine-induced flow arrest was associated with no more than a 15.7% increase or a 12.7% decrease in the incidence of a poor neurologic outcome at either 48 hours or at the time of hospital discharge. In addition, adenosine use was not associated with cardiac morbidity in the perioperative period (i.e., persistent arrhythmia or biomarkers of cardiac ischemia).

The Use of Adenosine in Cerebral Aneurysm Clipping: A Review

Management of intracranial aneurysms continues to evolve, with coiling of aneurysms becoming an increasingly used modality. However, for aneurysms which are considered to be “complex” due to their size, position, or morphology, clipping continues to be the preferred treatment option. Several techniques can be utilized intraoperatively to facilitate aneurysm exposure and clip ligation. These include deep hypothermic circulatory arrest, endovascular balloon occlusion with suction, and, most commonly, temporary clip application to the proximal feeding vessel. The use of these techniques has been limited by the associated significant morbidity and mortality, and in the case of temporary clipping, anatomic limitations preventing clip application in certain cases. Recently, adenosine induced transient circulatory arrest has undergone a resurgence in neurosurgical practice to assist in complex aneurysm clip ligation. In this article we review this technique with special emphasis on appropriate patient selection and safety profile.

Reduced Length of Stay and Hospital Cost for Unruptured Anterior Circulation Aneurysms Treated with Endovascular Coiling or a Minimally Invasive Thumb-Sized Pterional Craniotomy: Single Center Experience and Nationwide Inpatient Sample Data Analysis

Cost-benefit analysis of endovascular treatment compared to open-surgical treatment of cerebral aneurysms in the setting of global economic restrictions is of growing importance. We present our experience with coil embolization and a modified thumb-sized pterional craniotomy for clip ligation of unruptured anterior circulation cerebral aneurysms performed in a major tertiary cerebrovascular center; our experience is then compared to a matched dataset from the Nationwide Inpatient Sample (NIS). In our institutional analysis, all patients were aged ≤55 years and treated electively for unruptured anterior circulation aneurysms. A matched dataset from the NIS was constructed using patients ≤55 years with unruptured aneurysms. At our institution, length of stay was half that of NIS for both the surgical clipping group and the endovascular group. Additionally, hospital charges were reduced by one-third for surgical clipping and by approximately one-fourth for endovascular coiling. The cost of clipping vs coiling for unruptured cerebral aneurysms should not undermine the ethics of decision making, but rather should be used as a guide in allocation of hospital resources, manpower and funds. Thumb-sized craniotomies without use of cerebral retractors for clipping provide excellent recovery and show a significant decrease in the postoperative hospital stay as well as a lower cost of hospitalization compared to the national average. High volume centers for treatment of cerebral aneurysms, like ours which is managed by the same neurovascular staff for both treatment options, is an important factor in lowering the length of stay and hospitalization cost. Keywords: Craniotomy, cerebral aneurysm, clip ligation, endovascular coiling, health care costs, length of stay, minimally invasive, retractorless, surgery. Read more →

Reduced Length of Stay and Hospital Cost for Unruptured Anterior Circulation Aneurysms Treated with Endovascular Coiling or a Minimally Invasive Thumb-Sized Pterional Craniotomy: Single Center Experience and Nationwide Inpatient Sample Data Analysis

Cost-benefit analysis of endovascular treatment compared to open-surgical treatment of cerebral aneurysms in the setting of global economic restrictions is of growing importance. We present our experience with coil embolization and a modified thumb-sized pterional craniotomy for clip ligation of unruptured anterior circulation cerebral aneurysms performed in a major tertiary cerebrovascular center; our experience is then compared to a matched dataset from the Nationwide Inpatient Sample (NIS). In our institutional analysis, all patients were aged � 55 years and treated electively for unruptured anterior circulation aneurysms. A matched dataset from the NIS was constructed using patients � 55 years with unruptured aneurysms. At our institution, length of stay was half that of NIS for both the surgical clipping group and the endovascular group. Additionally, hospital charges were reduced by one-third for surgical clipping and by approximately one-fourth for endovascular coiling. The cost of clipping vs coiling for unruptured cerebral aneurysms should not undermine the ethics of decision making, but rather should be used as a guide in allocation of hospital resources, manpower and funds. Thumb-sized craniotomies without use of cerebral retractors for clipping provide excellent recovery and show a significant decrease in the postoperative hospital stay as well as a lower cost of hospitalization compared to the national average. High volume centers for treatment of cerebral aneurysms, like ours which is managed by the same neurovascular staff for both treatment options, is an important factor in lowering the length of stay and hospitalization cost.

Clip ligation of unruptured intracranial aneurysms: a prospective midterm outcome study

We conducted a prospective study to investigate the clinical and radiological outcome in a surgical case series of 176 patients with 203 unruptured intracranial aneurysms (UIA). The success of aneurysm obliteration was assessed within 2 weeks after surgery by digital subtraction angiography (DSA). Patients also underwent angiography 5 years after surgery. Clinical outcomes were assessed using the modified Rankin Scale (mRS). All predictors of poor surgical outcomes were assessed using an exact logistic regression. Overall, 83 % of the patients had a good outcome (mRS score 0 or 1); 10.8 % of the patients had a slight disability (mRS score 2), and 6.2 % of the patients had a moderate or moderate-severe disability (mRS score 3 or 4). The mortality rate was 0 % overall. The most important predictors of outcome were presence of history of ischemic cerebrovascular disease and postoperative stroke. Complete aneurysm occlusion was achieved in 93.5 % of all aneurysms. Sixty percent of treated aneurysms were checked with late follow-up DSA. No cases of hemorrhage from a surgically obliterated UIA were documented in this series during the 7.3 ± 1.4 (SD)-year follow-up period. If patients are carefully selected and individually assigned to their optimum treatment modality, IUAs can be obliterated by surgery with a low percentage of unfavorable outcomes.

Adenosine-Induced Flow Arrest to Facilitate Intracranial Aneurysm Clip Ligation

Adenosine-Induced Flow Arrest to Facilitate Intracranial Aneurysm Clip Ligation

Adenosine-induced Transient Asystole for Intracranial Aneurysm Surgery

BRIEF SUMMARY: We describe the use of adenosine-induced cardiac arrest to facilitate intracranial aneurysm clip ligation. Cerebral aneurysms are highly variable which may result in difficult surgical exposure for clip ligation in select cases. Secure clip placement is often not feasible without temporarily decompressing the aneurysm. This can be accomplished with temporary clip ligation of proximal vessels, or with deep hypothermic circulatory arrest on cardiopulmonary bypass, although these methods have their own inherent risks. Here we describe an alternate method of decompressing the aneurysm via adenosine-induced transient asystole. We examined the records of 27 patients who underwent craniotomy for cerebral aneurysm clipping in which adenosine was used to induce transient asystole to facilitate clip ligation. Duration of adenosine-induced bradycardia (heart rate <40) and hypotension (SBP < 60) recorded on the electronic anesthesia record and outcome data including incidence of successful clipping, intraoperative and postoperative complications, and mortality were recorded. Satisfactory aneurysm decompression was achieved in all cases, and all aneurysms were clipped successfully. The median dose of intravenous adenosine resulting in bradycardia greater than 30 seconds was 30 mg. The median dose of adenosine resulting in hypotension greater than 30 seconds was 15 mg, and greater than 60 seconds was 30 mg. One case of prolonged hypotension after rapid redosing of adenosine required brief closed chest compressions before circulation was spontaneously restored. No other adverse events were observed. Adenosine cardiac arrest is a relatively novel method for decompression of intracranial aneurysms to facilitate clip application. With appropriate safety precautions, it is a reasonable alternative method when temporary clipping of proximal vessels is not desirable or not possible.

Adenosine-Induced Flow Arrest to Facilitate Intracranial Aneurysm Clip Ligation: Dose-Response Data and Safety Profile

Adenosine-Induced Flow Arrest to Facilitate Intracranial Aneurysm Clip Ligation: Dose-Response Data and Safety Profile

Adenosine-Induced Flow Arrest to Facilitate Intracranial Aneurysm Clip Ligation

Adenosine-induced transient flow arrest has been used to facilitate clip ligation of intracranial aneurysms. However, the starting dose that is most likely to produce an adequate duration of profound hypotension remains unclear. We reviewed our experience to determine the dose-response relationship and apparent perioperative safety profile of adenosine in intracranial aneurysm patients. This case series describes 24 aneurysm clip ligation procedures performed under an anesthetic consisting of remifentanil, low-dose volatile anesthetic, and propofol in which adenosine was used. The report focuses on the doses administered; duration of systolic blood pressure <60 mm Hg (SBP(<60 mm Hg)); and any cardiovascular, neurologic, or pulmonary complications observed in the perioperative period. A median dose of 0.34 mg/kg ideal body weight (range: 0.29-0.44 mg/kg) resulted in a SBP(<60 mm Hg) for a median of 57 seconds (range: 26-105 seconds). There was a linear relationship between the log-transformed dose of adenosine and the duration of a SBP(<60 mm Hg) (R(2) = 0.38). Two patients developed transient, hemodynamically stable atrial fibrillation, 2 had postoperative troponin levels >0.03 ng/mL without any evidence of cardiac dysfunction, and 3 had postoperative neurologic changes. For intracranial aneurysms in which temporary occlusion is impractical or difficult, adenosine is capable of providing brief periods of profound systemic hypotension with low perioperative morbidity. On the basis of these data, a dose of 0.3 to 0.4 mg/kg ideal body weight may be the recommended starting dose to achieve approximately 45 seconds of profound systemic hypotension during a remifentanil/low-dose volatile anesthetic with propofol induced burst suppression.