Temporary vascular occlusion during aneurysm surgery

Role of temporary arterial occlusion in subarachnoid hemorrhage outcomes: a prospective cohort study

PURPOSE

Temporary arterial occlusion (TAO) is a widespread practice in the surgical treatment of intracranial aneurysms. This study aimed to investigate TAO's role during ruptured aneurysm clipping as an independent prognostic factor on short- and long-term outcomes.

METHODS

This prospective cohort included 180 patients with ruptured intracranial aneurysms and an indication of microsurgical treatment. Patients who died in the first 12 hours after admission were excluded.

RESULTS

TAO was associated with intraoperative rupture (IOR) (odds ratio - OR = 10.54; 95% confidence interval - 95%CI 4.72-23.55; p < 0.001) and surgical complications (OR = 2.14; 95%CI 1.11-4.07; p = 0.01). The group with TAO and IOR had no significant difference in clinical (p = 0.06) and surgical (p = 0.94) complications compared to the group that had TAO, but no IOR. Among the 111 patients followed six months after treatment, IOR, number of occlusions, and total time of occlusion were not associated with Glasgow Outcome Scale (GOS) in the follow-up (respectively, p = 0.18, p = 0.30, and p = 0.73). Among patients who underwent TAO, IOR was also not associated with GOS in the follow-up (p = 0.29).

CONCLUSIONS

TAO was associated with IOR and surgical complications, being the latter independent of IOR occurrence. In long-term analysis, neither TAO nor IOR were associated with poor clinical outcomes.

Intra-operative cerebral blood flow assessment by indocyanine green video-angiography after temporary arterial occlusion in aneurysm surgery and its clinical implications: a prospective study

Objective

Indocyanine green video angiography (ICG-VA) is a routine while performing vascular surgery to assess patency of perforators, completeness of clipping and/or to assess patency of anastomosis. Its usefulness in assessing cerebral blood flow and perfusion is not well studied. This study is aimed to assess the cerebral blood flow and perfusion after temporary clipping and to correlate with the risk of ischemia.

Methods

Prospective analysis of intra-operative ICG-VA performed during temporary arterial occlusion in 38 patients from January 2014 to December 2018 was conducted. Co-relation with post-operative MR diffusion weighted imaging (MR DWI) in terms of vascular territory of interest within 48 hours of surgery was performed. Clinical outcome was assessed using modified Rankin Scale (mRS) score 1-month post-surgery.

Results

43 aneurysms in 38 patients clipped using ICG-VA were included in this study. No side effect of ICG dye was seen in any patients. The number of times temporary clips applied had a direct relationship to the delay in appearance of ICG in the surgical field which became statistically significant after application of 3rd temporary clip. Nine (23.7%) patients developed ischemia following the procedure confirmed by post-operative MR DWI and all the ischemic cases had visible decrease in ICG fluorescence post-temporary clipping.

Conclusions

No previous study had tried to assess the intraoperative cerebral blood flow and perfusion during temporary clipping of parent vessels during aneurysm surgery. The use of ICG-VA can be extended to assess perfusion in desired territory by merely assessing the degree of opacification.

Effects of Temporary Clipping as an Expression of Circulatory Individuality: Online Measurement of Temporal Lobe Oxygen Levels During Surgery for Middle Cerebral Artery Aneurysms

OBJECTIVE

Despite its widespread use, much is left to understand about the repercussions of parent artery temporary clipping in neurosurgery. This study seeks a better comprehension of the subject by aiming at the online measurement of brain tissue oxygen pressure (P_btO₂) during such events.

METHODS

This was a prospective observational study. Patients submitted to surgery for middle cerebral artery aneurysms (both ruptured and unruptured) were continuously monitored under Intensive Care Monitoring+ software, in order to obtain temporal (downstream) P_btO₂ levels while temporary clips were applied. Separate P_btO₂ curve events were identified, extracted, and processed. These were studied for assessing intraindividual and interindividual variability and the potential impact of repeated clipping and previous aneurysmal rupture.

RESULTS

Eighty-six temporary clippings (from 20 patients) were recorded with a mean duration of 140.8 (41 - 238) seconds. Temporary arterial occlusion at the M1 segment of the middle cerebral artery produced specifically shaped trajectories, characterized by a preclipping P_btO₂ level, rapid downward sigmoid-shaped curve, succession of progressively angled slopes, and lower plateau. The steepest slope of the curve correlated strongly with P_btO₂ range (P < 0.001, r = 0.944). These features were highly reproducible only intraindividually and did not vary significantly with repeated clippings.

CONCLUSIONS

The effects of temporary arterial occlusion on temporal lobe oxygenation demonstrate a high degree of singularity, highlighting the potential benefits of assessing individual available collateral circulation intraoperatively. The "P_btO₂ steepest slope" predicted the severity of P_btO₂ decrease and was available within the first minute.

Intracranial Vascular Procedures

Anesthesia for intracranial vascular procedures is complex because it requires a balance of several competing interests and potentially can result in significant morbidity and mortality. Frequently, periods of ischemia, where perfusion must be maintained, are combined with situations that are high risk for hemorrhage. This review discusses the basic surgical approach to several common pathologies (intracranial aneurysms, arteriovenous malformations, and moyamoya disease) along with the goals for anesthetic management and specific high-yield recommendations.

A prediction of postoperative neurological deficits following intracranial aneurysm surgery using somatosensory evoked potential deterioration duration

Although the application of somatosensory evoked potential (SSEP) in intracranial aneurysm surgery has been well demonstrated, the relationship between the duration of SSEP deterioration and postoperative neurological deficits (PNDs) is still not clear. The objectives of this study were (1) to detect the relationship between the SSEP deterioration duration and PND; and (2) detect the relationship between SSEP deterioration duration and postoperative computed tomography (CT) findings. Data from 587 patients were reviewed and 40 patients with SSEP deterioration were enrolled. Four patients presented irreversible disappearance and 36 patients presented reversible deterioration (including 9 [25%] patients with reversible reduction and 27 [75%] patients with reversible disappearance). In the patients with reversible SSEP deterioration, 17 patients had PNDs, and the SSEP deterioration duration was 42 ± 46 min, ranging from 5 to 180 min. Nineteen patients did not have PNDs, and their duration of SSEP deterioration was 11 ± 9 min (range 2-40 min). The SSEP deterioration duration significantly differed between patients with or without PND (P < 0.01). Eleven minutes is the optimal cut-off value of motor evoked potential change duration avoiding PND (area under the curve = 0.84). Patients with a SSEP deteriorating duration > 11 min had a significant higher incidence rate of abnormal CT finding postoperatively (p < 0.05). According to these results, we conclude that the duration of SSEP deterioration is extremely important to postoperative neurological function, and in order to avoid PND, the SSEP deterioration duration must not exceed 10 min. The SSEP deterioration duration is also associated with postoperative CT findings.

Adenosine-induced cardiac arrest as an alternative to temporary clipping during intracranial aneurysm surgery

OBJECTIVE

The purpose of this study was to analyze the impact of adenosine-induced cardiac arrest (AiCA) on temporary clipping (TC) and the postoperative cerebral infarction rate among patients undergoing intracranial aneurysm surgery.

METHODS

In this retrospective matched-cohort study, 65 patients who received adenosine for decompression of aneurysms during microsurgical clipping were identified (Group A) and randomly matched with 65 selected patients who underwent clipping but did not receive adenosine during surgery (Group B). The matching criteria included age, Fisher grade, aneurysm size, rupture status, and location of aneurysms. The primary outcomes were TC time and the postoperative infarction rate. The secondary outcome was the incidence of intraoperative aneurysm rupture (IAR).

RESULTS

In Group A, 40 patients underwent clipping with AiCA alone and 25 patients (38%) received AiCA combined with TC, and in Group B, 60 patients (92%) underwent aneurysm clipping under the protection of TC (OR 0.052; 95% CI 0.018–0.147; p < 0.001). Group A required less TC time (2.04 minutes vs 4.46 minutes; p < 0.001). The incidence of postoperative lacunar infarction was equal in both groups (6.2%). There was an insignificant between-group difference in the incidence of IAR (1.5% in Group A vs 6.1% in Group B; OR 0.238; 95% CI 0.026–2.192; p = 0.171).

CONCLUSIONS

AiCA is a useful technique for microneurosurgical treatment of cerebral aneurysms. AiCA can minimize the use of TC and does not increase the risk of IAR and postoperative infarction.

"Clip first" policy in management of intracranial MCA aneurysms: Single-centre experience with a systematic review of literature

BACKGROUND

The results of microsurgical treatment for middle cerebral artery (MCA) aneurysms (ANs) have been highly satisfying for decades, notoriously posing a challenge for interventional neuroradiologists. Following the International Subarachnoid Aneurysm Trial (ISAT) study results, most centres across Europe and the USA switched to a "coil first" policy. The purpose of this study is to evaluate and critically review the substantiation of this change.

METHODS

The authors conducted a single-institution retrospective study of MCA AN treatment between January 2000 and December 2013 maintaining a "clip first" policy. The results are supplied with a literature review.

RESULTS

A total of 315 MCA ANs were treated in 288 consecutive patients (209 females, 79 males). Microsurgical treatment was performed for 238 AN patients (116 ruptured, 122 unruptured) and 77 AN patients (46 ruptured, 31 unruptured) who underwent a coiling procedure. Treatment-related morbidity and mortality (MM) for unruptured ANs was 2.8 % in the microsurgical group and 10.3 % in the endovascular group. The percentage of patients with no/minor permanent neurological deficits after SAH in a good initial clinical state (HH 1-2) was 93 % in the microsurgical and 76 % in the endovascular group. A literature review identified 21 studies concerning MCA AN treatment with a specified decision-making algorithm. Microsurgery seemed superior to endovascular management regarding both clinical and radiological outcomes, although several aspects of the analysed reports might appear questionable.

CONCLUSION

Although this study has its inherent limitations, the effect brought about by microsurgical clipping of MCA ANs remains superior to that of endovascular embolisation and it should be sustained as the first treatment choice. The decision about the treatment strategy should be made by a multi-disciplinary team consisting of specialists from both teams, bearing in mind the higher occlusion rate and longevity of the surgical treatment.

Concerns and challenges during anesthetic management of aneurysmal subarachnoid hemorrhage

Anesthetic management of patients with aneurysmal subarachnoid hemorrhage is challenging because of the emergency nature of the presentation, complex pathology, varied intracranial and systemic manifestations and need for special requirements during the course of management. Successful perioperative outcome depends on overcoming these challenges by thorough understanding of pathophysiology of Subarachnoid hemorrhage, knowledge about associated complications, preoperative optimization, choice of definitive therapy, a good anesthetic and surgical technique, vigilant monitoring and optimal postoperative care. Guidelines based on randomized studies and provided by various societies are helpful in the routine management of these patients and wherever there is a lack of high quality evidence, the available data is provided for practical management.

Controversies in the anesthetic management of intraoperative rupture of intracranial aneurysm

Despite great advancements in the management of aneurysmal subarachnoid hemorrhage (SAH), outcomes following SAH rupture have remained relatively unchanged. In addition, little data exists to guide the anesthetic management of intraoperative aneurysm rupture (IAR), though intraoperative management may have a significant effect on overall neurological outcomes. This review highlights the various controversies related to different anesthetic management related to aneurysm rupture. The first controversy relates to management of preexisting factors that affect risk of IAR. The second controversy relates to diagnostic techniques, particularly neurophysiological monitoring. The third controversy pertains to hemodynamic goals. The neuroprotective effects of various factors, including hypothermia, various anesthetic/pharmacologic agents, and burst suppression, remain poorly understood and have yet to be further elucidated. Different management strategies for IAR during aneurysmal clipping versus coiling also need further attention.

Genealogy of Training in Vascular Neurosurgery

Remarkable advances and changes in the landscape of neurovascular disease have occurred recently. Concurrently, a paradigm shift in training and resident education is underway. This crossroad of unique opportunities and pressures necessitates creative change in the training of future vascular neurosurgeons to allow incorporation of surgical advances, new technology, and supplementary treatment modalities in a setting of reduced work hours and increased public scrutiny. This article discusses the changing landscape in neurovascular disease treatment, followed by the recent changes in resident training, and concludes with our view of the future of training in vascular neurosurgery.

Fusiform aneurysms of the lenticulostriate artery

Lenticulostriate artery aneurysms are rare, can be difficult to diagnoze, and when they rupture they are often associated with deep intraparenchymal hemorrhages. In particular, fusiform, dissecting aneurysms of a distal lenticulostriate artery are extremely rare. Typically, they are usually associated with underlying systemic conditions such as systemic lupus erythematosus, moyamoya disease, and substance abuse. Given their usual small size and location, these aneurysms may be difficult to detect with angiography and can be challenging to treat with either endovascular or microsurgical techniques. We provide background information, review the existing treatment experiences reported in the literature, and present a discussion regarding the optimal management using an illustrative clinical vignette. Parent artery obliteration can be a safe and effective treatment in these rare aneurysms.

The impact of temporary artery occlusion during intracranial aneurysm surgery on long-term clinical outcome: Part II. The patient who undergoes elective clipping

BACKGROUND

Temporary artery occlusion (TAO) during intracranial aneurysm surgery is a key element in facilitating aneurysm dissection and clipping. Despite its significance, knowledge of its effects on long-term clinical outcome in patients undergoing elective clipping for unruptured aneurysms is limited. This study evaluated the safety of this technique in this patient population by 1 surgeon.

METHODS

Patients managed for an intracranial aneurysm were followed from 2000-2009. This study included a cohort of patients found to have unruptured intracranial aneurysms who underwent TAO during their elective clipping procedure. Potential risk factors to affect outcome were considered. Effects of TAO on long-term clinical outcome were evaluated using the Glasgow Outcome Scale (GOS) obtained retrospectively by analyzing medical records at the last follow-up visit or discharge. Analyses included descriptive statistics, binary logistic regression, and ordinal logistic regression.

RESULTS

Inclusion criteria were met by 246 patients (75.2% female, age 54 years±10.9) with electively clipped, unruptured aneurysms. Mean follow-up was 53 months±67.5. Mean temporary artery clipping time was 16.1 minutes±14.7. Of patients, 86% had a good outcome and made a complete recovery at last follow-up (GOS 5); 9% of patients were moderately disabled (GOS 4); 5% of patients were severely disabled (GOS 3), were in a vegetative state (GOS 2), or had died (GOS 1). TAO time had no effects on overall long-term clinical outcomes (P=0.59). Although patients with posterior circulation aneurysms had a worse outcome compared with patients with anterior circulation aneurysms (P=0.008), age (P=0.176) and aneurysm size (P=0.497) were not significantly associated with clinical outcome.

CONCLUSIONS

This study did not demonstrate any relationship between limited duration of TAO and clinical outcome. Posterior circulation aneurysms are associated with worse long-term clinical outcomes in patients with electively clipped, unruptured aneurysms.

The impact of temporary artery occlusion during intracranial aneurysm surgery on long-term clinical outcome: part I. Patients with subarachnoid hemorrhage

BACKGROUND

Temporary artery occlusion (TAO) during intracranial aneurysm surgery is an integral element in facilitating aneurysm dissection and clipping. Despite its significance, knowledge of effects of TAO on long-term clinical outcome is limited. The purpose of this study was to evaluate the impact of TAO in patients with subarachnoid hemorrhage (SAH) at one institution.

METHODS

Patients managed for an intracranial aneurysm were followed from January 2000 to July 2009. This study included a cohort of patients with a diagnosis of SAH who underwent TAO during aneurysm surgery. Risk factors known to affect outcome were considered. Effects of TAO time on long-term clinical outcome were evaluated using the Glasgow Outcome Scale (GOS) at last follow-up visit or hospital discharge. Analyses included descriptive statistics and binary logistic and ordinal logistic regression.

RESULTS

Inclusion criteria were met by 382 patients (74.3% female, age 52 years ± 13.5) with aneurysmal SAH. Mean follow-up was 39 months ± 57.3. Mean TAO time was 19.4 minutes ± 15.7. Of patients, 66% had a good outcome and made a complete recovery at last follow-up (GOS 5); 13% of patients were moderately disabled (GOS 4); and 27% of patients were severely disabled (GOS 3), were in a vegetative state (GOS 2), or had died (GOS 1). Overall, TAO time had no effect on overall long-term clinical outcome (P = 0.76). Higher Hunt and Hess grades (P < 0.001), Fisher computed tomography grades (P < 0.001), age (P < 0.001), larger size of aneurysm (P < 0.008), aneurysms of the posterior circulation (P = 0.044), and presence of clinical vasospasm (P < 0.001) were significantly associated with worse outcomes. On logistic regression analysis, the association between location of aneurysm (anterior vs. posterior circulation) and outcome disappeared.

CONCLUSIONS

Limited duration of TAO during aneurysm surgery did not affect long-term clinical outcome and appears to be safe in patients with aneurysmal SAH. Established SAH risk factors including Hunt and Hess grades, Fisher computed tomography grades, and presence of clinical vasospasm clearly correlated with long-term clinical outcomes.

Guidelines for the management of aneurysmal subarachnoid hemorrhage: a guideline for healthcare professionals from the American Heart Association/american Stroke Association

PURPOSE

The aim of this guideline is to present current and comprehensive recommendations for the diagnosis and treatment of aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

A formal literature search of MEDLINE (November 1, 2006, through May 1, 2010) was performed. Data were synthesized with the use of evidence tables. Writing group members met by teleconference to discuss data-derived recommendations. The American Heart Association Stroke Council's Levels of Evidence grading algorithm was used to grade each recommendation. The guideline draft was reviewed by 7 expert peer reviewers and by the members of the Stroke Council Leadership and Manuscript Oversight Committees. It is intended that this guideline be fully updated every 3 years.

RESULTS

Evidence-based guidelines are presented for the care of patients presenting with aSAH. The focus of the guideline was subdivided into incidence, risk factors, prevention, natural history and outcome, diagnosis, prevention of rebleeding, surgical and endovascular repair of ruptured aneurysms, systems of care, anesthetic management during repair, management of vasospasm and delayed cerebral ischemia, management of hydrocephalus, management of seizures, and management of medical complications.

CONCLUSIONS

aSAH is a serious medical condition in which outcome can be dramatically impacted by early, aggressive, expert care. The guidelines offer a framework for goal-directed treatment of the patient with aSAH.

Circulatory arrest and deep hypothermia for the treatment of complex intracranial aneurysms--results from a single European center

BACKGROUND

Vascular neurosurgery faces the controversial discussion about the need for deep hypothermia and circulatory arrest (dh/ca) for the treatment of complex cerebral aneurysms. In this retrospective analysis, we present our experience in the treatment of 26 giant and large cerebral aneurysms under profound hypothermia and circulatory arrest.

METHODS

All patients were treated surgically under dh/ca. Seventeen patients had aneurysms of the anterior circulation, and nine patients had aneurysms of the posterior circulation. Thrombosis or calcification was found in ten patients. Eleven patients presented with subarachnoid hemorrhage. The seven patients with the longest circulation arrest time were analyzed in detail.

RESULTS

Subarachnoid hemorrhage led to hospital admission in 42% (n = 11) of cases. The overall mortality was 11.5%, and the overall morbidity was 15%. Ten patients deteriorated transiently but fully recovered. The mean age, Glasgow Coma Score, Fisher, and Hunt and Hess Score correlated significantly with the long-term outcome. Circulation arrest time correlated significantly to the neurological outcome on discharge. All patients with prolonged circulation arrest times had wide aneurysmal necks, and four had adjacent vessels to the dome or the parent vessel included in the neck. We observed a significant increase of neurological deficits immediately postoperatively, but this neurological deterioration resolved over time.

CONCLUSIONS

We observed neurological deterioration immediately postoperatively in 13 patients, but all patients fully recovered within 6 months except for four patients. A long cardiac arrest time reflected complex pathoanatomical conditions. We conclude that the clipping procedure under deep hypothermia and circulatory arrest remains a pivotal armament in complex vascular neurosurgery.

Risk of stroke with temporary arterial occlusion in patients undergoing craniotomy for cerebral aneurysm

OBJECTIVE

This study was performed to elucidate the technical and patient-specific risk factors for postoperative ischemia in patients undergoing temporary arterial occlusion (TAO) during the surgical repair of their aneurysms.

METHODS

Eighty-nine consecutive patients in whom TAO was performed during surgical repair of an aneurysm were retrospectively analyzed. The demographics of the patients were analyzed with respect to age, Hunt and Hess grade on admission, Fisher grade of hemorrhage, aneurysm characteristics, timing of surgery, duration of temporary occlusion, and number of temporary occlusive episodes. Outcome was analyzed at the 3-month follow-up, along with the occurrence of symptomatic and radiological stroke.

RESULTS

In overall, twenty-seven patients (29.3%) had radiologic ischemia attributable to TAO and fifteen patients (16.3%) had symptomatic ischemia attributable to TAO. Older age and poor clinical grade were associated with poor clinical outcome. There was a significantly higher rate of symptomatic ischemia in patients who underwent early surgery (p = 0.007). The incidence of ischemia was significantly higher in patients with TAO longer than 10 minutes (p = 0.01). In addition, patients who underwent repeated TAO, which allowed reperfusion, had a lower incidence of ischemia than those who underwent single TAO lasting for more than 10 minutes (p = 0.011).

CONCLUSION

Duration of occlusion is the only variable that needs to be considered when assessing the risk of postoperative ischemic complication in patients who undergo temporary vascular occlusion. Attention must be paid to the patient's age, grade of hemorrhage, and the timing of surgery. In addition, patients undergoing dissection when brief periods of temporary occlusion are performed may benefit more from intermittent reperfusion than continuous clip application. With careful planning, the use of TAO is a safe technique when used for periods of less than 10 minutes.

The effect of temporary aneurysm clip on the common carotid artery of atherosclerotic rabbits

BACKGROUND

We compared the effect of temporary aneurysm clips on atherosclerotic and nonatherosclerotic CCA of rabbits by morphometric and ultrastructural methods.

METHODS

The rabbits (N = 12) were divided into 2 groups: the first group was fed a 2% cholesterol diet, and the second group, a normal diet for 4 weeks. Atherosclerotic lesions developed after 4 weeks. Temporary aneurysm clips were placed on the left CCA of both groups; the right CCA of both groups served as control. Thus, a total of 4 groups were used: atherosclerotic (A), atherosclerotic/clip (AC), nonatherosclerotic (NA), and nonatherosclerotic/clip (NAC). Temporary aneurysm clips were applied for 1, 5, and 10 minutes in the AC and NAC groups. No temporary clip was placed on the right CCA (A and NA groups). The affected parts of the CCA via clips were examined under light microscope and SEM.

RESULTS

Comparison of atherosclerotic and nonatherosclerotic CCA of rabbits under light microscope indicated that the wall of atherosclerotic CCA was thicker than that of nonatherosclerotic CCA. The difference between the thickness of atherosclerotic and nonatherosclerotic CCAs was significant. SEM analyses showed that in nonatherosclerotic CCAs, the effect of temporary aneurysm clips was seen after 10 minutes, but in atherosclerotic CCAs, the effect was seen within the 1st minute of clipping and continued in the 5th and 10th minutes.

CONCLUSION

The duration of temporary clipping should be decreased for the neurovascular surgery of atherosclerotic patients.

Detection of cerebral ischemia in neurovascular surgery using quantitative frequency-domain near-infrared spectroscopy

OBJECT

There is great value in monitoring for signs of ischemia during neurovascular procedures. Current intraoperative monitoring techniques provide real-time feedback with limited accuracy. Quantitative frequency-domain near-infrared spectroscopy (Q-NIRS) allows measurement of tissue oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (tHb) concentrations and brain tissue oxygen saturation (SO2), which could be useful when monitoring for evidence of intraoperative ischemia.

METHODS

Using Q-NIRS, the authors monitored 25 neurovascular procedures including aneurysm clip placement, arteriovenous malformation resection, carotid endarterectomy, superficial temporal artery-middle cerebral artery (MCA) bypass surgery, external carotid artery-MCA bypass surgery, encephaloduromyosynangiosis, and balloon occlusion testing. The Q-NIRS technology provides measurable cerebral oxygenation values independent from those of the scalp tissue. Thus, alterations in the variables measured with Q-NIRS quantitatively reflect cerebral tissue perfusion. Bilateral monitoring was performed in all cases. Five of the patients exhibited evidence of clinical ischemic events during the procedures. One patient suffered blood loss with systemic hypotension and developed diffuse brain edema intraoperatively, one patient suffered an ischemic event intraoperatively and developed an occipital stroke postoperatively, and one patient showed slowing on electroencephalography intraoperatively during carotid clamping; in two patients balloon occlusion testing failed. In all cases of ischemic events occurring during the procedure, Q-NIRS monitoring showed a decrease in HbO2, tHb, and SO2, and an increase in HHb.

CONCLUSIONS

. Quantitative frequency-domain near-infrared spectroscopy provides quantifiable and continuous real-time information about brain oxygenation and hemodynamics in a noninvasive manner. This continuous intraoperative oxygenation monitoring is a promising method for detecting ischemic events during neurovascular procedures.

Experience from "double-insurance bypass." Surgical results and additional techniques to achieve complex aneurysm surgery in a safer manner

BACKGROUND

"Double-insurance bypass" was recently advocated to avoid the risk of cerebral ischemia during prolonged temporary occlusion of the carotid artery. For large aneurysms needing temporary but prolonged obliteration of the internal carotid artery (ICA). We have attempted the double-insurance bypass in 15 patients and, herein, report the efficacies and limitations of the procedure, and surgical techniques to make this procedure safer.

METHODS

We treated 15 patients with complex internal carotid aneurysms by clipping surgery with the aid of radial artery (RA) to proximal middle cerebral artery (MCA) bypass, so-called double-insurance bypass. We analyzed surgical results of the procedure.

RESULTS

In 11 patients, the duration of temporary occlusion of the ICA could be prolonged for as long as 110 minutes (mean, 45 minutes) without any ischemic complications. One patient in the earlier period of our experience suffered extended cerebral infarction due to possible restricted blood flow through the RA, because the brachial artery was compressed by the firm shoulder joint and neighboring structures. Thereafter, we routinely monitored the blood pressure of MCA (MCABP) and never experienced such cortical infarctions. Another 3 patients, however, experienced ischemia in the territory of perforating arteries that originated from a segment that could not be perfused by the RA-MCA bypass.

CONCLUSIONS

In combination with monitoring of MCABP, the double-insurance bypass can be a safer and more potent adjunctive procedure for the treatment of complex internal carotid aneurysms which require prolonged temporary occlusion of the ICA.

Clampage vasculaire temporaire

In many situations, temporary artery occlusion is an integral component of aneurysm surgery. The use of temporary clip may allow safer and easier aneurysmal dissection and clipping. Several points, concerning the duration and overall risks of temporary occlusion and the method of choice for cerebral function monitoring have to be discussed.

MATERIAL AND METHODS

Non exhaustive review of neurosurgical literature.

DISCUSSION

Temporary clip application decreases the risk of intraoperative aneurysmal rupture. The analysis of data published in the literature showed that several questions remain open concerning the optimal method of neuroprotection and cerebral function monitoring, as well as the limit of occlusion duration. Other clinical trials are needed to assess the efficacy and safety of this technique.

Extracellular amino acid changes in patients during reversible cerebral ischaemia

This study investigated the changes in extracellular chemistry during reversible human cerebral ischaemia. Delayed analysis was performed on samples taken from a subgroup of patients during aneurysm surgery previously reported. Frozen microdialysis samples from 14 patients who had all undergone temporary clipping of the ipsilateral internal carotid artery (ICA) were analysed for another 15 amino acids with HPLC and for glycerol with CMA-600. Changes were characterised according to whether cerebral tissue oxygen pressure (PBO2) decreases were brief or prolonged. Brief ICA clipping (maximum duration of 16 minutes) in 11 patients was not associated with changes in amino acids or glycerol. Cerebral ischaemia, defined by a PBO2 decrease below 1.1 kPa for at least 30 minutes during ICA occlusion, occurred in 3 patients. None of whom developed an infarct in the monitored region. This prolonged reversible ischaemia was associated with transient delayed increases in gamma-amino butyric acid (GABA) as well as glutamate and glycerol, each by two-to-three folds. This study demonstrates detectable transient increases in human extracellular glutamate, GABA and glycerol during identified periods of reversible cerebral ischaemia, maximal 30-60 minutes after onset of ischaemia, but not in other amino acids detected by HPLC.

Extracorporeal femoral to carotid artery perfusion in selective brain cooling for a giant aneurysm

Giant partially thrombosed intracranial aneurysms are a challenge to treat surgically, and they are also unsuitable for coil embolization. The current options for treatment include extracranial-intracranial bypass followed by parent artery occlusion or direct surgical occlusion in which deep hypothermic circulatory arrest is used. The authors report the use of another approach in the treatment of a giant anterior circulation aneurysm: selective brain cooling accomplished by extracorporeal perfusion. This facilitated direct surgery on a 4.2-cm, partially thrombosed aneurysm of the middle cerebral artery (MCA). A brain temperature of 22 degrees C was achieved after 20 minutes of perfusion with blood cooled using an extracorporeal technique of femoral-common carotid artery perfusion. This was followed by a 20-minute period of surgical trapping of the MCA, then evacuation and clip occlusion of the aneurysm. During the period of selective brain cooling the patient's core body temperature was maintained above 35 degrees C. This technique of selective brain cooling may be a useful alternative to currently available surgical and endovascular methods of treatment for giant aneurysms.

Monitoring of brain tissue oxygenation during aneurysm surgery: prediction of procedure-related ischemic events

OBJECT

The aim of this study was to evaluate the feasibility of monitoring brain tissue oxygenation (PO2) during aneurysm surgery for the detection of procedure-related ischemia.

METHODS

Between 1997 and 1998, PO2 was monitored prospectively in a cohort of 40 patients (42 recordings) during aneurysm surgery in the anterior circulation within the vascular territory of the aneurysm-bearing artery. The position of the probe used to measure oxygenation levels was verified on computerized tomography (CT) scanning on the 1st postoperative day. Because of the mislocation of one probe and the malfunction of another, data from only 38 patients (40 recordings) were suitable for analysis. Relative changes from baseline to absolute nadir values of intraoperative PO2 were correlated with simultaneously recorded somatosensory evoked potentials (SSEPs), and cardiovascular and ventilatory parameters. The frequency of ischemic events was evaluated with the aid of CT on the 1st postoperative day as a substitute parameter for intraoperative ischemia. Clinical outcome was evaluated 30 days postoperatively based on the Glasgow Outcome Scale. Except for three, all patients underwent surgery for treatment of a symptomatic aneurysm. Mean baseline PO2 was 23.9 mm Hg (range 2-67.2 mm Hg) before clip application. A relative decrease in PO2 (20% decrease in value compared with baseline) occurred in 12 patients and was a sensitive indicator for the risk of ischemia during temporary arterial occlusion, but was less predictive of nonocclusive ischemia (sensitivity 0.5; positive predictive value [PPV] 0.42; p > 0.05). Results of receiver operating characteristic analysis demonstrated a postclipping PO2 nadir of 15 mm Hg as a dichotomizing threshold for the prediction of ischemia. This threshold rendered an improved sensitivity (0.9) and PPV (0.56) for procedure-related ischemia (p = 0.0003). The results of utility analysis revealed this monitoring parameter to be clinically diagnostic. Only PO2 monitoring, and not SSEP at the tibial nerve, was predictive of ischemia within the anterior cerebral artery territory.

CONCLUSIONS

Using 15 mm Hg as a dichotomizing threshold, intraoperative PO2 monitoring enables one to identify patients at risk for procedure-related ischemia during aneurysm surgery and surpasses SSEP monitoring. This newly defined threshold based on intraoperative PO2 monitoring provides a basis for studies on treatments for procedure-related ischemia during aneurysm surgery.

Effects of variation in cerebral haemodynamics during aneurysm surgery on brain tissue oxygen and metabolism

OBJECTIVES

This study explores the sensitivities of multiparameter tissue gas sensors and microdialysis to variations in blood pressure, CSF drainage and to well-defined periods of ischaemia accompanying aneurysm surgery, and their predictive value for infarction.

METHODS

A Neurotrend sensor [brain tissue partial pressure of oxygen (PBO2), carbon dioxide (PBCO2), brain pH (pHB) and temperature] and microdialysis catheter were inserted into the appropriate vascular territory prior to craniotomy.

RESULTS

Baseline data showed a clear correlation between PBO2 and mean arterial pressure (MAP) below a threshold of 80 mmHg. PBO2 improved with CSF drainage in 20 out of 28 (Wilcoxon: P < 0.05) cases where data was available. In 26 patients the effects of temporary vascular clipping (TC) (mean duration 16 minutes) were assessed. 2 patients subsequently declared infarction in the region of the probes. PBO2 fell from a mean 3.2 (95% CI 2.4-4.1) kPa to a minimum of 1.5 (95% CI 1.0-2.0) kPa in the non-infarct group. There was a lower baseline PBO2 (mean 0.8 kPa) in the patients who infarcted. PBCO2 mirrored PBO2 changes, whereas pHB did not change significantly in either group. Microdialysis changes associated with decreased PBO2 included a delayed increase in lactate, a raised lactate/pyruvate ratio and more rarely an increased glutamate. These changes were seen in 11 patients but were not predictive of infarction.

CONCLUSION

Hypotension during aneurysm surgery is associated with a low PBO2. Multiparameter sensors can be sensitive to acute ischaemia. Microdialysis shows potential in the detection of metabolic changes during tissue hypoxia.

Extracellular lactate/pyruvate and glutamate changes in patients during per-operative episodes of cerebral ischaemia

OBJECTIVE

Temporary Internal Carotid Artery (ICA) clipping necessary during aneurysm surgery was used as a model to investigate metabolic changes in the human brain during defined episodes of ischaemia.

DESIGN

An observational study using intracerebral monitors: PBO2 (Neurotrend) and microdialysis (CMA, Sweden).

SUBJECTS

16 patients monitored during complex aneurysm surgery.

OUTCOME MEASURES

Changes in extracellular concentrations of glucose, lactate, and glutamate and lactate/pyruvate ratio (L/P).

RESULTS

Mean age was 55. 10 patients presented with subarachnoid haemorrhage and 6 with mass effect (4 giant). Temporary ICA occlusion was required for dissection (n = 9), intraoperative rupture (n = 5) or aneurysmal thrombectomy (n = 2). The mean total duration was 15 minutes (range 4-52 minutes). No infarcts developed in the monitored regions. Microdialysis was unsuccessful in 3 patients and Neurotrend in 1. Patients were grouped according to the degree and duration of fall in PBO2: minimal brief falls were not associated with microdialysis changes (n = 5). More pronounced falls were associated with increases in L/P (n = 4). Only prolonged occlusions averaging 42 minutes (n = 3) with PBO2 sustained below 1 kPa were associated with rises in glutamate.

CONCLUSIONS

Brief temporary ICA occlusion caused an initial increased L/P. Glutamate increases were only seen after occlusion that was prolonged with PBO2 below 1.0 kPa.

Temporary arterial occlusion in the repair of ruptured intracranial aneurysms: an analysis of risk factors for stroke

OBJECT

This study was performed to further elucidate technical and patient-specific risk factors for perioperative stroke in patients undergoing temporary arterial occlusion during the surgical repair of their aneurysms.

METHODS

One hundred twelve consecutive patients in whom temporary arterial occlusion was performed during surgical repair of an aneurysm were retrospectively analyzed. Confounding factors (inadvertent permanent vessel occlusion and retraction injury) were identified in six cases (5%) and these were excluded from further analysis. The demographics for the remaining 106 patients were analyzed with respect to age, neurological status, aneurysm characteristics, intraoperative rupture, duration of temporary occlusion, and number of occlusive episodes; end points considered were outcome at 3-month follow up and symptomatic and radiological stroke.

CONCLUSIONS

Overall 17% of patients experienced symptomatic stroke and 26% had radiological evidence of stroke attributable to temporary arterial occlusion. A longer duration of clip placement, older patient age, a poor clinical grade (Hunt and Hess Grades IV-V), early surgery, and the use of single prolonged clip placement rather than repeated shorter episodes were associated with a higher risk of stroke based on univariate analysis. Intraoperative aneurysm rupture did not affect stroke risk. On multivariate analysis, only poorer clinical grade (p = 0.001) and increasing age (p = 0.04) were significantly associated with symptomatic stroke risk.

Cerebral oxygen and microdialysis monitoring during aneurysm surgery: effects of blood pressure, cerebrospinal fluid drainage, and temporary clipping on infarction

OBJECT

The aim of this study was to investigate potential episodes of cerebral ischemia during surgery for large and complicated aneurysms, by examining the effects of arterial temporary clipping and the impact of confounding variables such as blood pressure and cerebrospinal fluid (CSF) drainage.

METHODS

Brain tissue PO2, PCO2, and pH, as well as temperature and extracellular glucose, lactate, pyruvate, and glutamate were monitored in 46 patients by using multiparameter sensors and microdialysis. Baseline data showed that brain tissue PO2 decreased significantly, below a mean arterial pressure (MAP) threshold of 70 mm Hg. Further evidence of its relationship with cerebral perfusion pressure was shown by an increase in mean brain tissue PO2 after drainage of CSF from the basal cisterns (Wilcoxon test, p < 0.01). Temporary clipping was required in 31 patients, with a mean total duration of 14 minutes (range 3-52 minutes), causing brain tissue PO2 to decrease and brain tissue PCO2 to increase (Wilcoxon test, p < 0.01). In patients in whom no subsequent infarction developed in the monitored region, brain tissue PO2 fell to 11 mm Hg (95% confidence interval 8-14 mm Hg). A brain tissue PO2 level below 8 mm Hg for 30 minutes was associated with infarction in any region (p < 0.05 according to the Fisher exact test); other parameters were not predictive of infarction. Intermittent occlusions of less than 30 minutes in total had little effect on extracellular chemistry. Large glutamate increases were only seen in two patients, in both of whom brain tissue PO2 during occlusion was continuously lower than 8 mm Hg for longer than 38 minutes.

CONCLUSIONS

The brain tissue PO2 decreases with hypotension, and, when it is below 8 mm Hg for longer than 30 minutes during temporary clipping, it is associated with increasing extracellular glutamate levels and cerebral infarction.

Intraoperative complications in aneurysm surgery: a prospective national study

OBJECT

With increasing use of endovascular procedures, the number of aneurysms treated surgically will decline. In this study the authors review complications related to the surgical treatment of aneurysms and address the issue of maintaining quality standards on a national level.

METHODS

A prospective, nonselected amalgamation of every aneurysm case treated in five of six neurosurgical centers in Sweden during 1 calendar year was undertaken (422 patients; 7.4 persons/100,000 population/year). The treatment protocols at these institutions were very similar. Outcome was assessed using clinical end points. In this series, 84.1% of the patients underwent surgery, and intraoperative complications occurred in 30% of these procedures. Poor outcome from technical complications was seen in 7.9% of the surgically treated patients. Intraoperative aneurysm rupture accounted for 60% and branch sacrifice for 12% of all technical difficulties. Although these complications were significantly related to aneurysm base geometry and the competence of the surgeon, problems still occurred apparently at random and also in the best of hands (17%). The temporary mean occlusion time in the patients who suffered intraoperative aneurysm rupture was twice as long as the temporary arrest of blood flow performed to aid dissection.

CONCLUSIONS

The results obtained in this series closely reflect the overall management results of this disease and support the conclusion that surgical complications causing a poor outcome can be estimated on a large population-based scale. Intraoperative aneurysm rupture was the most common and most devastating technical complication that occurred. Support was found for a more liberal use of temporary clips early during dissection, regardless of the experience of the surgeon. Temporary regional interruption of arterial blood flow should be a routine method for aneurysm surgery on an everyday basis. A random occurrence of difficult intraoperative problems was clearly shown, and this factor of unpredictability, which is present in any preoperative assessment of risk, strengthens the case for recommending neuroprotection as a routine adjunct to virtually every aneurysm operation, regardless of the surgeon's experience.

Continuous monitoring of regional cerebral blood flow during temporary arterial occlusion in aneurysm surgery

OBJECT

Temporary arterial occlusion (TAO) during aneurysm surgery carries the risk of ischemic sequelae. Because monitoring of regional cerebral blood flow (rCBF) may limit neurological damage, the authors evaluated a novel thermal diffusion (TD) microprobe for use in the continuous and quantitative assessment of rCBF during TAO.

METHODS

Following subcortical implantation of the device at a depth of 20 mm in the middle cerebral artery or anterior cerebral artery territory, rCBF was continuously monitored by TD microprobe (TD-rCBF) throughout surgery in 20 patients harboring anterior circulation aneurysms; 46 occlusive episodes were recorded. Postoperative radiographic evidence of new infarction was used as the threshold for failure of occlusion tolerance. The mean subcortical TD-rCBF decreased from 27.8+/-8.4 ml/100 g/min at baseline to 13.7+/-11.1 ml/100 g/min (p < 0.0001) during TAO. The TD microprobe showed an immediate exponential decline of TD-rCBF on clip placement. On average, 50% of the total decrease was reached after 12 seconds, thus rapidly indicating the severity of hypoperfusion. Following clip removal, TD-rCBF returned to baseline levels after an average interval of 32 seconds, and subsequently demonstrated a transient hyperperfusion to 41.4+/-18.3 ml/l 00 g/min (p < 0.001). The occurrence of postoperative infarction (15%) and the extent of postischemic hyperperfusion correlated with the depth of occlusion-induced ischemia.

CONCLUSIONS

The new TD microprobe provides a sensitive, continuous, and real-time assessment of intraoperative rCBF during TAO. Occlusion-induced ischemia is reliably detected within the 1st minute after clip application. In the future, this may enable the surgeon to alter the surgical strategy early after TAO to prevent ischemic brain injury.

Possible control of intermittent cerebral ischemia by monitoring of direct-current potentials

OBJECT

Neurosurgically induced temporary occlusion of intracranial arteries carries the risk of cerebral ischemic damage. Because negative shifts in the cortical direct-current (DC) potential indicate tissue depolarization and, thus, critical ischemic stress, the authors hypothesized that recordings of these potentials could help to determine the optimal duration and frequency of induced intermittent focal ischemia to prevent brain injury. The investigators related the results of DC recordings both to simultaneously recorded decreases in extracellular Ca++ concentration ([Ca++]o), which reflect Ca++ entry into cells, and to histological outcome.

METHODS

In cats anesthetized with halothane the effects of intermittent brief (10 minutes long, six times [6 x 10-min group]) and prolonged (20 minutes long, three times [3 x 20-min group]) episodes of middle cerebral artery occlusions were compared with those of a single continuous episode (1 x 60-min group). Laser Doppler flow probes and ion-selective microelectrodes were used to measure cerebral blood flow, DC potentials, and [Ca++]o in cortical tissues of ectosylvian gyri. Negative shifts in DC potential were evaluated in the three groups during the entire 60-minute-long period of ischemia and were smallest in the 6 x 10-min group, larger in the 3 x 20-min group, and largest in the 1 x 60-min group. Accordingly, infarct volumes were smallest in the 6 x 10-min group, intermediate in the 3 x 20-min group, and largest in the 1 x 60-min group. Decreases in ischemic [Ca++]o were significantly greater in the 1 x 60-min group than in the two groups in which there were repetitive occlusions, and recovery of [Ca++]o after reperfusion normalized only in the 1 x 60-min group.

CONCLUSIONS

The DC potential may provide a reliable measure to optimize intermittent ischemia and to achieve minimal ischemic brain injury during temporary neurosurgical occlusion of cerebral arteries.

Health-related quality of life after aneurysmal subarachnoid hemorrhage: impacts of bleeding severity, computerized tomography findings, surgery, vasospasm, and neurological grade

OBJECT

Based on the results of earlier studies it is agreed that the significance of aneurysm location and surgery for neuropsychological impairments after subarachnoid hemorrhage (SAH) is secondary to the effects of the bleeding itself. Therefore, the present study was performed to evaluate whether bleeding, acute clinical course, and surgery have persistent effects on health-related quality of life (QOL) after SAH.

METHODS

A series of 116 patients was examined for 4 to 5 years (mean 52.2 months) after aneurysmal SAH by means of a QOL questionnaire. Eighty-six patients (74.1%) had undergone surgery early (< or = 72 hours post-SAH). There were 77 women (66.4%) and 39 men (33.6%) in the study group, and the mean age of the patients was 50.3+/-13.3 years (range 30-69 years). Patients who had undergone surgery for a left-sided middle cerebral artery (MCA) aneurysm complained of significantly more impairments in social contact, communication, and cognition than those treated for a right-sided MCA aneurysm. No other effects of aneurysm location (including the anterior communicating artery) emerged. Multiple aneurysms, intraoperative aneurysm rupture, and partial resection of the gyrus rectus had no adverse effects on later daily life. Only temporary clipping was associated with increased complaints in some QOL areas. Disturbances of the circulation of cerebrospinal fluid and the presence of intraventricular hemorrhage led to more impairments in daily life. Specific effects of the anatomical pattern of the bleeding could be identified, but no adverse effects of vasospasm were found. Multivariate analyses revealed, in particular, that patient age and admission neurological status (Hunt and Hess grade) are substantial predictors of the psychosocial sequelae of SAH.

CONCLUSIONS

In contrast to the mild effects of aneurysm surgery, patient's age, initial neurological state on admission, and the bleeding pattern substantially influence late QOL after SAH.

Nuances of middle cerebral artery aneurysm microsurgery

Middle cerebral artery aneurysms, a common source of subarachnoid hemorrhage, occur predominantly at the main bifurcation of the middle cerebral artery. Microsurgical clipping is the most effective treatment of these aneurysms because of their peripheral location, wide necks, and straightforward surgical anatomy. Despite the moderate technical requirements of this type of surgery, patients with ruptured aneurysms often have poor outcomes because of the high incidence of intracerebral hematomas. Although several different surgical approaches can be used, we favor a lateral-to-medial transsylvian approach for most aneurysms. This description of our surgical technique stresses minimizing retraction to avoid injury to the brain and preparing broad-based middle cerebral artery aneurysms for clipping. Management of outcomes when using these techniques also is presented.

Functional outcome after aneurysmal subarachnoid hemorrhage

The introduction of the operating microscope, the principle of early surgery, specialized intensive care units, the calcium antagonist nimodipine, the sophisticated pre- and postoperative management and an aggressive antiischemic pharmacological management have substantially reduced morbidity and mortality after aneurysmal subarachnoid hemorrhage (SAH). In spite of this progress, many patients after rupture and surgical repair of an intracranial aneurysm exhibit substantial cognitive deficits and emotional problems although their neurological outcome was rated as good according to the Glasgow Outcome Scale (GOS = I). Therefore, a comprehensive neuropsychological examination is called for in order to evaluate the factual functional outcome after SAH. Neither focal brain damage associated with aneurysm location nor surgery but the hemorrhage itself and related events can be regarded as the most important causal factors for the late result after SAH. In contrast to the mild permanent effects of aneurysm surgery, the initial bleeding itself seems to have substantial lasting adverse neurobehavioral effects after. In concordance with other authors our own data stress the strong predictive power of the bleeding pattern such as the presence of intraventricular and/or intracerebral blood on the functional outcome after aneurysmal SAH.

Ruptured giant intracranial aneurysms. Part II. A retrospective analysis of timing and outcome of surgical treatment

OBJECT

This retrospective study was made to determine the relationship between surgical timing and outcome in all patients with ruptured giant intracranial aneurysms undergoing surgical treatment at the Mayo Clinic between 1973 and 1996.

METHODS

The authors studied 109 patients, 102 of whom were referred from other medical centers. The ruptured giant aneurysms were 25 to 60 mm in diameter. One hundred five of the patients survived the rupturing of the aneurysm to undergo operation, with direct surgery possible in 84% of cases. Excluding delayed referrals, the average time to surgery after admission to the Mayo Clinic was approximately 4 to 5 days. Patients admitted earlier tended to be in poorer condition, often undergoing earlier operation. On average, surgical treatment was administered later for patients with ruptured aneurysms of the posterior circulation than for those with aneurysms in the anterior circulation. Temporary occlusion of the parent vessel was necessary in 67% of direct procedures, with an average occlusion time of 15.5 minutes. Among surgically treated patients, a favorable outcome was achieved in 72% harboring ruptured anterior circulation aneurysms and in 78% with ruptured posterior circulation lesions.

CONCLUSIONS

The overall management mortality rate was 21.1%, and the mortality rate for surgical management was 8.6%. The authors believe that because of the technical difficulties and risk of rebleeding associated with ruptured giant intracranial aneurysms, timely referral to and well-planned treatment at medical centers specializing in management of these lesions are essential to effect a more favorable outcome.

Intraoperative monitoring of substrate delivery during aneurysm and hematoma surgery: initial experience in 16 patients

The effects of proximal occlusion of the parent artery during aneurysm surgery in humans are not fully understood, although this method is widely used. The reduction in substrate that can be tolerated by normal and subarachnoid hemorrhage (SAH)-affected brain is unknown. Therefore, the authors measured brain oxygen tension (brain PO2), carbon dioxide tension (brain PCO2), pH, and hemoglobin oxygen (HbO2) saturation before and after temporary occlusion in 12 patients with aneurysms. The effect of removal of a traumatic intracranial hematoma on cerebral oxygenation was also studied in four severely head injured patients. A multiparameter sensor was placed in the cortex of interest and locked by means of a specially designed skull bolt. The mean arterial blood pressure, inspired O2 fraction, and end-tidal PCO2 were analyzed. Brain PO2 and HbO2 saturation data were collected every 10 seconds. Descriptive and nonparametric analyses were used to analyze the data. A wide range in baseline PO2 was seen, although a decrease from baseline in brain PO2 was found in all patients. During temporary occlusion, brain PO2 in patients with unruptured aneurysm (seven patients) dropped significantly, from 60 +/- 31 to 27 +/- 17 mm Hg (p < 0.05). In the SAH group (five patients), the brain PO2 dropped from 106 +/- 74 to 87 +/- 73 mm Hg (not significant). Removal of intracranial hematomas in four severely head injured patients resulted in a significant increase in brain PO2, from 13 +/- 9 to 34 +/- 13 mm Hg (p < 0.05). The duration of safe temporary occlusion could not be determined from this group of patients, because none developed postoperative deterioration in their neurological status. However, the data indicate that this technique is useful to detect changes in substrate delivery during intraoperative maneuvers. This study also reemphasizes the need for emergency removal of intracranial hematomas to improve substrate delivery in severely head injured patients.

Temporary occlusion of the middle cerebral artery in intracranial aneurysm surgery: time limitation and advantage of brain protection

The risk of focal infarction secondary to the induced reversible arrest of local arterial flow during microsurgical dissection of middle cerebral artery (MCA) aneurysms was evaluated further to define the optimal approach to temporary arterial occlusion. To compare the effectiveness of potential brain-protection anesthetics, a group of patients treated with the intravenous agents propofol, etomidate, and pentobarbital, administered individually or in combination, was compared to a group treated with the inhalational agent isoflurane. Forty-nine consecutive MCA aneurysm surgeries involving the temporary clipping of the parent vessel were retrospectively reviewed. Thirty-eight patients received intravenous brain-protection (IVBP) anesthesia. Groups of patients with and without infarctions, and receiving and not receiving IVBP anesthesia, were compared based on the duration and nature of temporary arterial occlusion. Postoperative radiographic evidence of new infarction was used as the threshold for failure of occlusion tolerance. The overall infarction rate was 22.4% (11 of 49 patients), including 15.8% (six of 38 patients) in the IVBP group versus 45.5% (five of 11 patients) in the group that did not receive brain protection (NBP). In the NBP group, the mean duration of temporary occlusion was 3.9 +/- 2.2 minutes for patients without infarction versus 12.2 +/- 4.3 minutes for patients with focal infarction (p < 0.01). In contrast, the mean duration was 13.6 +/- 10.6 minutes for patients without infarction and 18.5 +/- 9.9 minutes for patients with infarction in the IVBP group. All patients (four of four) in the NBP group who underwent occlusion lasting 10 minutes or longer suffered an infarction versus five of 23 patients in the IVBP group (p < 0.0001). Patients with multiple aneurysms were found to be at increased risk of developing focal infarction, whereas those treated with intermittent temporary clip application were at decreased risk. It is concluded that patients in whom focal iatrogenic ischemia is induced during MCA aneurysm clip ligation have a significant advantage compared with those receiving isoflurane when they are given pentobarbital as the primary neuroprotective agent or when they receive propofol or etomidate titrated to achieve electroencephalographic burst suppression, particularly if more than 10 minutes of occlusion time is required. It is also concluded that 10 minutes is a general guideline for safe, temporary occlusion of the MCA. The use of intermittent temporary arterial occlusion and its use in patients with multiple aneurysms need further evaluation before specific recommendations can be made.

Temporary occlusion of the middle cerebral artery in intracranial aneurysm surgery: time limitation and advantage of brain protection

The risk of focal infarction secondary to the induced reversible arrest of local arterial flow during microsurgical dissection of middle cerebral artery (MCA) aneurysms was evaluated further to define the optimal approach to temporary arterial occlusion. To compare the effectiveness of brain-protection anesthetics, a group of patients treated with the intravenous agents, propofol, etomidate, and pentobarbital, administered individually or in combination, was compared to a group treated with the inhalational agent isoflurane.

Forty-nine consecutive MCA aneurysm surgeries involving the temporary clipping of the parent vessel were retrospectively reviewed. Thirty-eight patients received intravenous brain-protection (IVBP) anesthesia. Groups of patients with and without infarctions, and receiving and not receiving IVBP, were compared based on the duration and nature of temporary arterial occlusion. Postoperative radiographic evidence of new infarction was used as the threshold for failure of occlusion tolerance. The overall infarction rate was 22.4% (11 of 49 patients), including 15.8% (six of 38 patients) in the IVBP group versus 45.5% (five of 11 patients) in the isoflurane (ISO) group. In the ISO group, the mean duration of temporary occlusion was 3.9 ± 2.2 minutes for patients without infarction versus 12.2 ± 4.3 minutes for patients with focal infarction (p < 0.01). In contrast, the mean duration was 13.6 ± 10.6 minutes for patients without infarction and 18.5 ± 9.9 minutes for patients with infarction in the IVBP group. All patients in the ISO group who underwent occlusion lasting 10 minutes or longer suffered an infarction versus five of 23 patients in the IVBP group. Patients with multiple aneurysms were found to be at increased risk of developing focal infarction, whereas those treated with intermittent temporary clip application were at a decreased risk.

It is concluded that patients in whom focal iatrogenic ischemia is induced during MCA aneurysm clip ligation have a significant advantage compared with those receiving ISO when they are given pentobarbital as the primary neuroprotective agent or when they receive propofol or etomidate titrated to achieve electroencephalographic burst suppression, particularly if more than 10 minutes of occlusion time is required. It is also concluded that 10 minutes is a general guideline for safe, temporary occlusion of the MCA. The use of intermittent temporary arterial occlusion and patients with multiple aneurysms need further evaluation before specific recommendations can be made.

Temporary vessel occlusion during intracranial aneurysm repair

Any method that decreases the risk of intraoperative rupture should improve outcome if complications associated with its use do not negate positive effect. If application time is limited and a form of cerebral protection and appropriate monitoring of cerebral function are used, temporary clip application may meet these requirements. The efficacy of temporary occlusion as an adjunct to aneurysm clipping may be limited by technical considerations with respect to regional anatomy, aneurysm size, and aneurysm consistency. In areas of limited access, positioning proximal clips may not be feasible. The use of endovascular techniques of balloon occlusion may provide proximal control in these situations (9, 106). The decision to use total circulatory arrest and profound hypothermia, as opposed to temporary clip application, remains largely a matter of the surgeon's judgment. The role of proximal parent vessel ligation must also be considered in the decision-making process regarding the treatment of giant or technically difficult aneurysms (114). Further refinements in cerebral monitoring that can accurately reflect intracellular processes in all territories affected by the application of temporary clips or balloon occlusion and development of more effective forms of cerebral protection may permit safer use of this technique. An adequately controlled clinical trial of temporary occlusion with or without putative "cerebral protection" is needed to confirm the efficacy of this technique.