Thiopental loading during controlled hypotension for intracranial aneurysm surgery

Perioperative Management of Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage is an acute neurologic emergency. Prompt definitive treatment of the aneurysm by craniotomy and clipping or endovascular intervention with coils and/or stents is needed to prevent rebleeding. Extracranial manifestations of aneurysmal subarachnoid hemorrhage include cardiac dysfunction, neurogenic pulmonary edema, fluid and electrolyte imbalances, and hyperglycemia. Data on the impact of anesthesia on long-term neurologic outcomes of aneurysmal subarachnoid hemorrhage do not exist. Perioperative management should therefore focus on optimizing systemic physiology, facilitating timely definitive treatment, and selecting an anesthetic technique based on patient characteristics, severity of aneurysmal subarachnoid hemorrhage, and the planned intervention and monitoring. Anesthesiologists should be familiar with evoked potential monitoring, electroencephalographic burst suppression, temporary clipping, management of external ventricular drains, adenosine-induced cardiac standstill, and rapid ventricular pacing to effectively care for these patients.

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.

Risks and benefits of deliberate hypotension in anaesthesia: a systematic review

This systematic review was performed to investigate and review the evidence on the risks and benefits of hypotensive anaesthesia in order to answer the following question: 'Should deliberate hypotension be used routinely during orthognathic surgery?' An electronic search on MEDLINE and the Cochrane Library database was carried out for all relevant articles using specific search keywords. All articles were classified by their levels of evidence. Studies with highest level of evidence and rated to have the lowest risk of bias were reviewed. Regarding the benefits of hypotensive anaesthesia, three studies reported significant decrease of blood loss in patients receiving hypotensive anaesthesia. Two studies reported a significant decrease in transfusion rate. Two studies demonstrated improved surgical field and significant reduction in operation time. In terms of risk, no significant changes in cerebral, cardiovascular, renal and hepatic functions in patients receiving hypotensive anaesthesia compared to control were reported. In conclusion, hypotensive anaesthesia appears to be effective in reducing blood loss. Serious consequences due to organ hypoperfusion are uncommon. Hypotensive anaesthesia can be justified as a routine procedure for orthognathic surgery especially bimaxillary osteotomy. Patient selection and appropriate monitoring are mandatory for this technique to be carried out safely.

Effects of intraoperative hypothermia on neuropsychological outcomes after intracranial aneurysm surgery

OBJECTIVE

Subarachnoid hemorrhage and surgical obliteration of ruptured intracranial aneurysms are frequently associated with neurological and neuropsychological abnormalities. We reported that intraoperative cooling did not improve neurological outcome in good-grade surgical subarachnoid hemorrhage patients, as assessed by the Glasgow Outcome Scale score or other neurological and functional measures (National Institutes of Health Stroke Scale, Rankin Disability Scale, Barthel Activities of Daily Living). We now report the results of neuropsychological testing in these patients.

METHODS

A total of 1,001 patients who bled < or = 14 days before surgery were randomly assigned to intraoperative hypothermia (t = 33 degrees C) or normothermia (37 degrees C). Outcome was assessed approximately 3 months after surgery. Patients underwent the Benton Visual Retention, Controlled Oral Word Association, Rey-Osterrieth Complex Figure, Grooved Pegboard, and the Trail Making tests. T-scores for each test were calculated from normative data. T-scores were averaged to calculate a Composite Score. A test result (or the Composite Score) was considered "impaired" if the T-score was two or more standard deviations below the norm. A Mini-Mental State Examination was also performed.

RESULTS

Neurological outcome data were available in 1,000 patients. Sixty-one patients died. Of the 939 survivors, 873 completed 3 or more tests (exclusive of the Mini-Mental State Examination). Patients with poor neurological outcomes were less likely to complete testing; only 3.9% of Good Outcome (Glasgow Outcome Scale score = 1) patients were untested, compared with 38.6% of patients with Glasgow Outcome Scale scores of 3 and 4. There were no prerandomization demographic differences between the two treatment groups. For hypothermic patients, 16.8% were impaired from their Composite Score versus 20.0% of patients in the normothermic group (p = 0.317). For patients in the hypothermic group, 54.5% were impaired on at least one test, compared with 55.5% of patients in the normothermic group (p = 0.865). Similar results were seen in patients with baseline WFNS scores = I. Mini-Mental State Examination scores in the hypothermic and normothermic groups were 27.4 +/- 3.8 and 26.8 +/- 4.5, respectively.

INTERPRETATION

This is the largest prospective evaluation of neuropsychological function after subarachnoid hemorrhage to date. Testing was completed in a high fraction of patients, demonstrating the feasibility of such testing in a large trial. However, the frequent inability to complete testing in poor-outcome patients suggests that testing may be best used to refine outcome assessments in good-grade patients. Many patients showed impairment on at least one test, with global impairment present in 17 to 20% of patients (18-21% of survivors). This was true even among the patients with the best preoperative condition (WFNS = 1). There was no difference in the incidence of impairment between hypothermic and normothermic groups.

Mild intraoperative hypothermia during surgery for intracranial aneurysm

BACKGROUND

Surgery for intracranial aneurysm often results in postoperative neurologic deficits. We conducted a randomized trial at 30 centers to determine whether intraoperative cooling during open craniotomy would improve the outcome among patients with acute aneurysmal subarachnoid hemorrhage.

METHODS

A total of 1001 patients with a preoperative World Federation of Neurological Surgeons score of I, II, or III ("good-grade patients"), who had had a subarachnoid hemorrhage no more than 14 days before planned surgical aneurysm clipping, were randomly assigned to intraoperative hypothermia (target temperature, 33 degrees C, with the use of surface cooling techniques) or normothermia (target temperature, 36.5 degrees C). Patients were followed closely postoperatively and examined approximately 90 days after surgery, at which time a Glasgow Outcome Score was assigned.

RESULTS

There were no significant differences between the group assigned to intraoperative hypothermia and the group assigned to normothermia in the duration of stay in the intensive care unit, the total length of hospitalization, the rates of death at follow-up (6 percent in both groups), or the destination at discharge (home or another hospital, among surviving patients). At the final follow-up, 329 of 499 patients in the hypothermia group had a Glasgow Outcome Score of 1 (good outcome), as compared with 314 of 501 patients in the normothermia group (66 percent vs. 63 percent; odds ratio, 1.14; 95 percent confidence interval, 0.88 to 1.48; P=0.32). Postoperative bacteremia was more common in the hypothermia group than in the normothermia group (5 percent vs. 3 percent, P=0.05).

CONCLUSIONS

Intraoperative hypothermia did not improve the neurologic outcome after craniotomy among good-grade patients with aneurysmal subarachnoid hemorrhage.

[Peroperative risks in cerebral aneurysm surgery]

The perioperative complications associated with cerebral aneurysm surgery require a specific anaesthetic management. Four major perioperative accidents are discussed in this review. The anaesthetic and surgical management in case of rebleeding subsequent to the re-rupture of the aneurysm is mainly prophylactic. It includes haemodynamic stability assurance, maintenance of mean arterial pressure (MAP) between 80-90 mmHg during stimulation of the patient such as endotracheal intubation, application of the skull-pin head-holder, incision, and craniotomy. The aneurysmal transmural pressure should be adequately maintained by avoiding an aggressive decrease of intracranial pressure. Once the skull is open, the brain must be kept slack in order to decrease pressure under the retractors and avoid the risks of stretching and tearing of the adjacent vessels. If, despite these precautions, the aneurysm ruptures again. MAP should be decreased to 60 mmHg and the brain rendered more slack, in order to allow direct clipping of the aneurysm, or temporary clipping of the adjacent vessels. The optimal agents in this situation are isoflurane (which decreases CMRO2), intravenous anaesthetic agents (inspite their negative inotropic effect, they may potentially protect the brain) and sodium nitroprusside. Vasospasm occurs usually between the 3rd and the 7th day after subarachnoid haemorrhage. It may be seen peroperatively. The optimal treatment, as well as prophylaxis, is moderate controlled hypertension (MAP > 100 mmHg), associated with hypervolaemia and haemodilution, the so-called triple H therapy, with strict control of the filling pressures. Other beneficial therapies are calcium antagonists (nimodipine and nicardipine), the removal of the blood accumulated around the brain and in the cisternae, and possibly local administration of papaverine. Abrupt MAP increases are controlled in order to maintain adequate aneurysmal transmural pressure. Beta-blockers, local anaesthetics administered locally or intravenously, a carefully titrated level of anaesthesia, a maintained volaemia play a protective role. Cerebral oedema is sometimes already present at the opening of the skull or may arise later, due to a high pressure under the retractors, to the surgical manipulations of the brain or to brain ischaemia subsequent to temporary clipping. Its treatment is aggressive, with intravenous agents, mannitol, deep hypocapnia and/or lumbar drainage. Prophylaxis, according to the "brain homeostasis concept", is the preferred method to avoid these four peroperative accidents. It includes normal blood volume, normoglycaemia, moderate hypocapnia, normotension, soft manipulation of the brain and optimal brain relaxation.

Variations in regional cerebral blood flow investigated by single photon emission computed tomography with technetium-99m-d, l-hexamethylpropyleneamineoxime = l-h during temporary clipping in intracranial aneurysm surgery: preliminary results

Single photon emission computed tomography with technetium-99m-d, l-hexamethylpropyleneamineoxime was used to assess variations in regional cerebral blood flow during temporary clipping in the course of intracranial aneurysm surgery and during the postoperative period in 20 patients, 14 of whom underwent temporary clipping. Of these 14 patients (Group A), 9 had aneurysms of the anterior communicating artery, 2 had aneurysms of the middle cerebral artery, and 3 had aneurysms of the carotid siphon. Temporary clips were applied, according to the site of the lesion, on A1, on the trunk of the middle cerebral artery, or on the trunk of the internal carotid artery. The occlusion time ranged from 2 to 31 minutes. The six patients who did not undergo temporary clipping served as controls (Group B), as follows: three had aneurysms of the posterior communicating artery, one of the anterior communicating artery, one of the middle cerebral artery, and one of the internal carotid artery. All patients were investigated with cerebral single photon emission computed tomography preoperatively, perioperatively, and postoperatively. In all the patients of Group A, the preliminary results of the study show a sharp fall in the perfusion of the territories of the temporarily clipped parent vessel and practically a complete recovery within 2 to 7 days of surgery, with no significant neurological symptoms. No similar disturbance of perfusion was found in the patients of Group B.

The risk of ischaemic brain damage during the use of self-retaining brain retractors

Self-retaining brain retractors (SRBR) are commonly used during intracranial surgery and they are indispensable during microneurosurgery. To evaluate limitations in the employment of SRBR, as well animal as human studies have been performed. In the animal studies, male Wistar rats were used for measurements of regional cerebral blood flow (rCBF) changes during brain retractor pressure (BRP) provided by lead weights. These weights, corresponding to different levels of mm Hg, were applicated for different periods of time on the parietal cortex after craniotomy. In one part of the animal studies different profiles of the application surface of the weights were evaluated. For measurement of the rCBF (n = 41) autoradiography with carbon-14(14C)iodoantipyrine was used as described by Gjedde et al (1980). A neuropathological method (n = 30) was used to reveal possible brain damage after graded BRP. In the rats the thresholds of rCBF, regional cerebral perfusion pressure (rCPP) and time were 20-25 ml/100 g/min, 20 mm Hg and 7-10 minutes respectively. In the human studies only alert patients without neurological deficits (except defects of the visual fields) and in whom preoperative CT-scans did not disclose any sign of infarction were included. BRP beneath as well the tip as the centre of the SRBR and the MABP were recorded continuously. Patients with peroperative complications were excluded. During the operations induced hypotension (n = 20) and mannitol (n = 6) were administrated. The patients (n = 23) had a 3-month follow-up examination. In man the thresholds of rCPP and time were found to be 10 mm Hg and 6-8 minutes, respectively. Other authors have found a rCBF threshold of 10-13 ml/100 g/min (Astrup 1982, Iannotti & Hoff 1983). It is concluded that the results obtained in the rat studies are comparable to the human situation if reservations are made concerning the differences in the thresholds of rCBF and rCPP. The time threshold of cerebral ischaemia seems to be rather equal in rat and in man. If these thresholds are reached, intermittent BRP is absolutely recommendable. It was also found that the most easily-handled retractors, those with a flat profile, did not decrease the rCBF further than other types of retractors.

Cerebral protection

Cerebral protection from an ischemic/hypoxic insult implies that tissue injury can be controlled or even prevented by certain therapeutic maneuvers. For example, physiological thresholds may be altered so that tissue vulnerability to the insult is reduced, or the intensity of an insult may be blunted by enhancing brain homeostasis. Such a therapeutic maneuver is carotid endarterectomy to improve blood flow in the disordered hemisphere. Alternatively, drugs with protective properties can be used before or even after the insult to "stabilize" injured tissue and prevent the harmful secondary effects that often follow. Various past and present approaches to cerebral protection employing physiological, pharmacological, and surgical intervention are reviewed. The mechanisms by which each allegedly protects the brain from ischemia and hypoxia are discussed briefly. Promising, but not always successful, approaches used in the past have pointed the way for new and more rational therapies. Truly effective protection of the brain from ischemia and hypoxia depends directly upon our capability to explore basic mechanisms of injury and our willingness to measure accurately and objectively the outcome of newly developed protective measures.