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

Effects of propofol on the activity of rat glutamate transporter type 3 expressed in Xenopus oocytes: the role of protein kinase C

We investigated the effects of propofol on one type of glutamate transporter, excitatory amino acid transporter 3 (EAAT3) and the role of protein kinase C (PKC) in mediating these effects. Rat EAAT3 was expressed in Xenopus oocytes. L-glutamate (30 microM)-induced membrane currents were measured. Propofol increased glutamate-induced inward currents significantly at two tested concentrations (30 and 100 microM) but not at other concentrations. Propofol (30 microM) significantly increased V(max), but not K(m) of EAAT3 for glutamate. The combination of phorbol-12-myrisate-13-acetate (PMA, a PKC activator) and propofol did not increase the responses further compared with PMA or propofol alone. Three PKC inhibitors (staurosporine, calphostin C, and chelerythrine) did not affect basal EAAT3 activity but significantly inhibited the propofol-enhanced EAAT3 activity. Our results suggest that propofol enhances EAAT3 activity at clinically relevant concentrations and PKC may mediate these effects.

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.

[Evaluation of microsurgical treatment in a series of 121 intracranial aneurysms]

OBJECTIVE

The results obtained with therapy of intracranial aneurysms, in terms of morbidity and mortality, are very important when the patient has to choose between microsurgical techniques or endovascular management. The aim of this paper is to review the information regarding current microsurgical treatment of intracranial aneurysms, and presenting our experience over the last five years.

MATERIAL AND METHODS

We studied 101 consecutive patients with 121 intracranial aneurysms admitted between 1996 and 2000 with the initial diagnosis of subarachnoid hemorrhage. We paid special attention to the day of admission from the onset of the symptomatic hemorrhage to the grade of Hunt&Hess scale and the possibility of early or delayed microsurgical treatment. The diagnosis was based on four vessels cerebral angiography and in a few cases with CT-angiography. All patients were treated by microsurgical technique and such treatment was completed by nimodipine, intensive care unit management and in some cases of postoperative suspected vasospasm, induced arterial hypertension was applied. Post surgical angiography was carried out in all patients to confirm the clipping of the cerebral aneurysm. The 12 months assessment was based on the Glasgow Outcome Scale (GOS).

RESULTS

The 92.1% of the patients were admitted with a grade equal or below III in the Hunt&Hess scale. A 80% were operated within the 72 hours of admission and in the remaining cases, the surgical treatment was delayed due to a grade IV or V or to a medical contraindication. Four patients died (3.9%). At 12 months follow up, 88.9% presented a score I or II in the GOS.

CONCLUSION

According to our results, there are a substantial improvements in the microsurgical treatment of cerebral aneurysms, specially in patients admitted early after the onset of the symptoms of their hemorrhage, who have a grade I to III in the Hunt&Hess scale and showed a good level of consciousness. We think that the improvement of our results are due to: l. the high percentage of patients admitted with grades I to III. 2. the high percentage of patients operated within the first 72 hours from the onset of their symptomatic hemorrhage. 3. surgery was always carried out by the same two experienced vascular neurosurgeons. 4. intraoperative measures taken to prevent the rupture of the aneurysm. 5. early administration of nimodipine, ICU management, doppler studies and in seldom cases, induced hypertension therapy to treat the vasospasm and postoperative hypotension.

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.

Ruptura aneurismática intraoperatória junto ao colo: sugestão de manuseio cirúrgico

A ruptura aneurismática intraoperatória de um aneurisma intracraniano pode comprometer dramaticamente um procedimento neurocirúrgico delicado, diminuindo as chances de uma evolução favorável do paciente. A ruptura ordinariamente se dá junto ao domus do aneurisma, causando icto.Com menor frequência, a ruptura pode se processar junto ao colo, em um ponto entre o vaso principal e o saco aneurismático. Isso causa um grande problema ao neurocirurgião; a colocação de um clipe de aneurisma neste local só irá aumentar a hemorragia. Nossa sugestão técnica resume-se à clipagem do aneurisma sobre um pequeno fragmento de músculo temporal colocado no local da ruptura. É bastante simples mas bastante útil, devendo ser lembrada no momento da ruptura. Não encontramos descrição semelhante nos principais livros e artigos que se referem à ruptura aneurismática durante a cirurgia.

Isoflurane induced prolonged protection against cerebral ischemia in mice: a redox sensitive mechanism?

We here demonstrate that general anesthesia with isoflurane can have profound effects on the brain of mice long after the anesthetic has been discontinued. Three hours of exposure to 1% isoflurane induced rapid and longlasting protection against 60 min transient focal cerebral ischemia induced by filament occlusion of the middle cerebral artery (MCAO). Mean infarct volumes were significantly smaller in animals pretreated with isoflurane 0, 12, and 24 h before MCAO (-38%, -31%, -24%, respectively). Mild hypoxia (17% O(2)) during or 5 mg/kg desferrioxiamine administered at the onset of isoflurane pretreatment completely abrogated the development of delayed tolerance (12 h) against focal cerebral ischemia, suggesting that the signaling of delayed protection induced by isoflurane is sensitive to the intracellular oxygenation state.

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.

Carotid endarterectomy in patients with contralateral internal carotid artery occlusion without intraoperative shunting

BACKGROUND

Controversy about the optimal method of performing a carotid endarterectomy (CEA) exists despite its widespread application and support from various randomized clinical trials. Many surgeons selectively or routinely use electroencephalography (EEG) monitoring as well as shunting when performing this operation.

METHODS

We conducted this retrospective study to assess the maximum carotid clamp time without shunting or EEG monitoring during a CEA without the development of neurological deficits in an already compromised cerebral circulation.

RESULTS

Fifteen consecutive patients who underwent CEAs between 1988 and 1999 met our criteria of angiographically documented ipsilateral internal carotid artery (ICA) stenosis with contralateral ICA occlusion. The patient presentations included asymptomatic (14%), transient ischemic attack (TIA) (50%), and stroke (36%). All patients were operated under general anesthesia without shunting and only 4 patients underwent EEG monitoring. On angiography, all 15 patients had ipsilateral ICA stenosis (70-99%) and contralateral occlusion. In 54% of patients, the vertebral arteries (VAs) were both patent, while in 46% of patients only 1 VA was patent. Eighty-five percent of patients had at least 1 patent anterior communicating (Pcomm) artery, while 15% had nonvisualized Pcomm arteries bilaterally. Of the 15 patients, 14 had a patent anterior communicating artery. The mean clamp time of the CCA was 18.5 minutes (range 14-30 minutes). None of the 15 patients had new neurological changes immediately postoperatively or during the 6 weeks of follow-up.

CONCLUSION

We propose that shunting may not be necessary during CEA for high-grade stenosis with contralateral ICA occlusion, presumably because of adequate distal small vessel collaterals.

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.

The influence of surgical experience on the rate of intraoperative aneurysm rupture and its impact on aneurysm treatment outcome

BACKGROUND

The influence of surgical experience on the result of aneurysm surgery remains unclear. To determine the impact of surgical experience we considered the occurrence of intraoperative aneurysm rupture (IAR) during microneurosurgery for intracranial aneurysms as an objective factor that could be evaluated.

METHODS

A retrospective study was performed on 379 consecutive patients with 490 cerebral aneurysms operated upon from 1989 to 1995.

RESULTS

IAR occurred in 6.7% of aneurysms and 8.7% of patients. There was a direct inverse relationship between the annual caseload of the surgeon and the risk of IAR. New neurological deficits (NND) occurred in 21% of patients with IAR, which accounts for 1.8% of NND in all patients with aneurysms.

CONCLUSION

Although there seems to be a direct relationship between surgical experience and the risk of IAR, the impact on the overall treatment outcome of cerebral aneurysms is rather limited.

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.

Internal shunting in small vessel reconstruction: an experimental study

We describe the experimental use of an endoluminal shunt in different procedures for small vessel reconstruction. Since the arteries used in this work are similar in diameter to those of the brain, this method could be applied to human vascular surgery.

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.

Intraoperative variables and early outcome after aneurysm surgery

BACKGROUND

The purpose of this study was to investigate the effects of blood pressure, temperature, and anesthetic agents on outcome in patients undergoing craniotomy for cerebral aneurysms.

METHODS

All ruptured and unruptured intracranial aneurysms operated on from 1992 to 1998 were reviewed retrospectively. The data included 297 aneurysms (190 ruptured and 107 unruptured). Data were collected on variables known to influence outcome after aneurysmal subarachnoid hemorrhage as well as on intraoperative factors that might influence outcome (intraoperative blood pressure, temperature, temporary clipping, anesthetic agents). Outcome was assessed at discharge using the Glasgow Outcome Scale.

RESULTS

In univariate analysis of patients with ruptured aneurysms, younger age, better clinical grade, lower Fisher grade, lower intraoperative blood pressure (maximum systolic and mean blood pressure), smaller decrease in intraoperative compared to preoperative systolic blood pressure, shorter duration of surgery, and use of propofol, pancuronium, or N(2)O were associated with significantly better outcome. In patients with unruptured aneurysms, increased intraoperative minimum diastolic and mean blood pressure, a decrease in the difference between multiple measures of preoperative and intraoperative blood pressure, and a shorter duration of surgery were associated with significantly better outcome. Intraoperative temperature did not affect outcome in either group. In multivariate analysis of patients with ruptured aneurysms, younger age, better clinical grade, lower maximum systolic intraoperative blood pressure, shorter duration of surgery, and use of propofol were independently associated with better outcome.

CONCLUSIONS

Multivariate analysis of intraoperative factors affecting outcome in patients undergoing craniotomy for ruptured aneurysms shows that decreased intraoperative blood pressure and use of propofol are associated with improved outcome. Univariate analysis suggests that decreasing the magnitude of drop in blood pressure intraoperatively from preoperative values in patients with ruptured or unruptured aneurysms is associated with better outcome. Intraoperative hypothermia did not affect outcome.

Multifactorial analysis of surgical outcome in patients with unruptured middle cerebral artery aneurysms

OBJECTIVE

To build a predictive tool for assessing both favorable outcome and morbidity in a large series of unruptured aneurysms.

SUMMARY BACKGROUND DATA

Some well-known predictors of clinical outcome for patients with ruptured aneurysms are not useful in forecasting outcome for patients with unruptured aneurysms.

METHODS

The authors analyzed 93 patients with a total of 101 unruptured middle cerebral aneurysms who underwent surgical clipping. Intraoperative data was reviewed and seven factors that might influence outcome were identified: 1) aneurysm size > 10 mm, 2) presence of a broad neck, 3) presence of intraaneurysmal plaque, 4) clipping of more than one aneurysm during the same surgery, 5) temporary occlusion of the middle cerebral artery, 6) multiple clip applications and repositionings, and 7) use of multiple clips. The entire group of unruptured middle cerebral artery aneurysms was divided into two subgroups on the basis of outcome. Each patient was subsequently analyzed for the Factor Accumulation Index (FAI), the sum of different factors observed in a given patient.

RESULTS

The expected outcome subgroup was represented by 86 patients, with a total of 92 aneurysms, and demonstrated the following results: no factors were found in six patients; FAI of 1: 24 patients; FAI of 2: 23 patients; FAI of 3: 12 patients; FAI of 4: 11 patients; FAI of 5: 8 patients; FAI of 6: one patient; FAI of 7: one patient. Seven patients represented the subgroup of unexpected outcomes with total morbidity of 7.5%. There were no deaths. None of the patients in this subgroup accumulated FAI of 0, 1, 2, or 5; otherwise: FAI of 3: two patients; FAI of 4: two patients; FAI of 6: one patient; FAI of 7: two patients.

CONCLUSION

It is possible to predict outcome in patients with unruptured middle cerebral artery aneurysm by calculating FAI. The postoperative morbidity increases with an FAI within a range of 3 to 4.

Intraoperative Mild Hypothermia Ameliorates Postoperative Cerebral Blood Flow Impairment in Patients with Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

Intraoperative mild hypothermia has been used during cerebral aneurysm surgery to reduce ischemic injury induced by temporary vessel occlusion and brain retraction. However, the clinical effects on cerebral hemodynamics are unclear. This study investigated the effects of intraoperative mild hypothermia on cerebral blood flow (CBF) after surgery to treat aneurysmal subarachnoid hemorrhage.

METHODS

Twenty-four patients with ruptured internal carotid or middle cerebral artery aneurysms, of preoperative Hunt and Hess Grade II or III, underwent aneurysm clipping within 72 hours after the onset of subarachnoid hemorrhage. During surgery, patients were randomly assigned to either intraoperative mild hypothermia (33.5°C, n = 12) or normothermia (37°C, n = 12). Brain single photon emission computed tomography with 99m Tc-hexamethylpropylenamine oxime or 99m Tc-l,l-ethylcysteinate dimer was performed on Days 4, 7, and 14 after subarachnoid hemorrhage. Regional CBF was determined in the basal ganglia and cingulate, frontal, and frontoparietal cortices, using a semiquantitative method.

RESULTS

CBF in the frontal cortex ipsilateral to the aneurysm was significantly higher in the hypothermia group than in the normothermia group on Day 4 (P &lt; 0.01) but not Day 7 or 14. There was a similar trend in the ipsilateral frontoparietal cortex, but it was not significant. There were no differences in regional CBF in the ipsilateral cingulate cortex or basal ganglia or in any contralateral region during the study period.

CONCLUSION

Intraoperative mild hypothermia may reduce the severity of ischemia induced by intraoperative temporary vessel occlusion and brain retraction, thus ameliorating postoperative CBF impairment. (47;601;2000)

Prospective analysis of aneurysm treatment in a series of 103 consecutive patients when endovascular embolization is considered the first option

OBJECT

The aim of this study was to evaluate prospectively the results of treating cerebral aneurysms with coil embolization (CE) or with surgical clipping when CE was considered the first option.

METHODS

Whenever an aneurysm was to be treated, CE was first considered by our neurovascular team. Surgical clipping was reserved for cases excluded from CE or cases in which CE failed. The study consisted of 103 consecutive patients with 132 aneurysms, of which 127 were treated. Coil embolization was performed using Guglielmi detachable coils, and surgery was performed using Zeppelin clips. Three groups were defined: Group A consisted of 64 aneurysms that were treated by CE (neck/sac ratio < 1:3); Group B, 63 aneurysms that were surgically clipped; and Group C, 12 aneurysms that failed to be satisfactorily (> or = 95%) embolized and were subsequently clipped. The percentages of residual aneurysm were 31.2% in Group A, 1.6% in Group B, and 0% in Group C. The percentages of patients with poor Glasgow Outcome Scale (GOS) scores (GOS Scores 1-3) were 13.3% in Group A, 6.1% in Group B, and 8.3% in Group C. The percentages of poor outcome (GOS Scores 1-3) in patients with good clinical status before treatment were 10.7% in Group A, 0% in Group B, and 8.3% in Group C.

CONCLUSIONS

Even with preselection, CE remains associated with a significant number of treatment failures and poor outcomes, even in patients with good preoperative clinical status. Surgical clipping can offer better results than CE, even for more complex aneurysms of the anterior circulation, especially for those involving the middle cerebral artery cases. However, because CE can be effective and causes less stress and invasiveness for the patient, it should be considered first in aneurysms strictly selected by a neurovascular team.

Adverse effects of limited hypotensive anesthesia on the outcome of patients with subarachnoid hemorrhage

OBJECT

This study was aimed at clarifying the effect of intraoperative hypotensive anesthesia on the outcome of early surgery in patients with subarachnoid hemorrhage (SAH) caused by saccular cerebral aneurysms. Other factors were also screened for possible effects on the outcome.

METHODS

Hospital charts in 84 consecutive patients with SAH who underwent aneurysm clipping by Day 4 were examined. Possible factors affecting the outcome were analyzed using multiple logistic regression with the dichotomous Glasgow Outcome Scale score as the outcome variable. The relationship between the intraoperative hypotension and the occurrence and severity of vasospasm was studied using both single- and multivariate analyses.

CONCLUSIONS

Intraoperative hypotension had a significantly adverse effect on the outcome of SAH. Hypotension was also related to more frequent and severe manifestations of vasospasm. A long-lasting effect of brain retraction is possibly the cause of this phenomenon. The data contained in this study preclude the use of intraoperative hypotension even in a limited form.

Neuronal damage in gerbils caused by intermittent forebrain ischemia

OBJECT

The purpose of this study was to investigate the possibility of preventing cumulative neuronal damage after repetitive severe ischemia.

METHODS

The authors monitored ischemic depolarization in the gerbil hippocampus, which has recently been shown to be a good experimental model of the effects of brief ischemia on the brain, and evaluated neuronal damage in the CA1 subregion 7 days after the ischemic insult. In a single-ischemia paradigm, the results indicate that induction of ischemia-induced neuronal damage depended on the duration of ischemic depolarization. Neuronal damage can be detected in the CA1 subregion after a period of depolarization lasting 210 seconds. Using a double-ischemia paradigm in which the animals were subjected to two periods of ischemia, there was apparently no accumulation of neuronal damage from the first ischemic episode to the second, provided the duration of the first period of ischemic depolarization did not exceed 90 seconds. Neuronal damage accumulated when the duration of the first ischemia episode exceeded 90 seconds, regardless of the duration of the reperfusion interval between the two ischemic insults. Finally, when the ischemic insult was spread over four separate episodes, each lasting 90 seconds (with a reperfusion interval of 5 minutes), neuronal damage was not found when the total depolarization period was less than 420 seconds.

CONCLUSIONS

The authors conclude that cumulative neuronal damage may be avoided by adopting an intermittent ischemia approach. The implications of these results for human surgery requiring temporary occlusion of the cerebral arteries are discussed.

Surgical treatment of anterior circulation aneurysms

The purpose of this paper is to present the results, assessed by an independent observer, of surgical treatment of 428 consecutive patients harbouring aneurysms of the anterior circulation, together with a review of relevant anatomy and operative strategy. At follow-up (mean 5.6 years) 89.3% lived at home and were independent, 5.1% lived at home but needed some kind of assistance, 2.0% lived in institution, whereas information was unavailable in 3.6% of living patients. Two hundred and fifty-three patients (64.5%) had unchanged employment status, 0.3% worked in sheltered environment, whereas 30.9% went out of work due to their subarachnoid hemorrhage (SAH). Information about employment status was unavailable in 4.3%. For aneurysms of the internal carotid, anterior communicating and middle cerebral artery, respectively, mortality was 3.2, 3.9 and 5.6%, whereas 92.0, 88.1 and 89.0% of surviving patients lived at home and were independent and 67.0, 63.6 and 63.0% had unchanged employment status. Three-months mortality of all causes was 4.2%. In the postoperative period 53 (12.4%) patients developed clinical signs of vasospasms, 6 (1.4%) had cardiac infarction, 4 (0.9%) lung oedema, 4 (0.9%) deep vein thrombosis, and 7 patients (1.6%) infection. During the follow-up period shunt-dependent hydrocephalus developed in 4.2% and 0.2% had a subsequent SAH from the same aneurysm. Forty-three patients were on anticonvulsive therapy.