A Technique of Anesthesia with Induced Hypotension for Surgical Correction of Intracranial Aneurysms

Aitken, R. R.; Drake, Charles G.

doi:10.1093/neurosurgery/21.cn_suppl_1.107

Cited by 29 publications

(3 citation statements)

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“…In these circumstances, drug-induced hypotension to levels of mean arterial pressure approximately 35-40 % of the patients' baseline values would not be expected to produce any significant effect on CBF. The successful use, in the clinical situation, of a technique of hypotensive anaesthesia similar to that used in this study (Aitken and Drake, 1974) would tend to support this contention. Although autoregulation of cerebral blood flow was impaired or lost at the levels of mean arterial pressure noted in this study, mean CBF was still within the accepted normal range.…”

Section: Clinical Significancementioning

confidence: 61%

Autoregulation of cerebral blood flow during controlled hypotension in baboons

Fitch

Ferguson

Sengupta

et al. 1976

Journal of Neurology, Neurosurgery & Psychiatry

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SYNOPSISThe effect of graded, progressive hypotensioni on the autoregulation of cerebral blood flow was studied in anaesthetised baboons. Progressive hypotension was produced over a period of four to five hours, either by graded haemorrhage or by the administration of increasing concentrations of hypotensive drugs. During haemorrhagic hypotension autoregulation was maintained until the mean arterial pressure had decreased to 65% of its baseline value, below which cerebral blood flow was pressure passive. In those animals subjected to drug-induced hypotension, autoregulation persisted to lower levels of mean arterial pressure (35-40% of baseline). It is postulated that under conditions of haemorrhagic hypotension, constriction of the extraparenchymal cerebral vessels in response to sympathetic stimulation decreases the possible range ofautoregulation in the anaesthetised baboon.Since its introduction into anaesthetic and surgical practice (Gardner, 1946), controlled hypotension has been used extensively to reduce bleeding and to facilitate surgery. However, despite the widespread use of the technique, the indications for induced hypotension have not been defined clearly and considerable disagreement exists regarding its safety (Davison, 1958;Enderby, 1958; Mayrhofer, 1971). The primary objections stem from uncertainties regarding the adequacy of cerebral tissue perfusion during the period of lowered arterial pressure (Brierley and Cooper, 1962;Adams et al., 1966).The present investigations were undertaken to measure the effect of a graded and progressive decrease in systemic arterial pressure on the cerebral blood flow of anaesthetised baboons and to compare the effects of haemorrhagic and pharmacologically-induced hypotension. METHODSYoung adult baboons (9-14 kg) were tranquillised with phencyclidine (12 mg intramuscularly) and then anaesthetised with thiopentone (7.5 mg/kg intravenously), nitrous oxide and oxygen (70%:30%). In addition, half-hourly doses of phencyclidine (2 mg intramuscularly) and suxamethonium (100 mg intiamuscularly) were administered to prevent awareness and to produce muscular relaxation. The trachea was intubated and ventilation was controlled throughout each investigation (Starling respiratory pump), the minute volume and the inspired oxygen concentration being adjusted to produce normocapnia and normoxia. The end-tidal carbon dioxide concentration was monitored continuously by an infra-red analyser (URAS 4: Hartmann and Braun). During each determination of cerebral blood flow, the arterial pH and blood-gas tensions were measured using appropriate, suitably calibrated electrodes (Radiometer). Body temperature was maintained within normal limits (36°C-38°C) by means of heating lamps. Correction was made, where necessary, for any temperature difference existing between the animal and the electrode system (Severinghaus, 1966).Cerebral blood flow was determined by external scintillation counting over the right parietal area after 014 Protected by copyright. on 11 May 2018 by guest.

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Section: Clinical Significancementioning

confidence: 61%

Autoregulation of cerebral blood flow during controlled hypotension in baboons

Fitch

Ferguson

Sengupta

et al. 1976

Journal of Neurology, Neurosurgery & Psychiatry

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“…1 In view of variable loss of autoregulation in patients with aneurysm, however, hypotension could unpredictably cause cerebral ischemia. A practical method is needed to monitor the CNS response to hypotensive stress.…”

Section: Discussionmentioning

confidence: 99%

“…Profound controlled hypotension reduces the risk of rupture and aids dissection. 1 Hypotension "defuses" the aneurysm by markedly decreasing wall tension. 2 As one reduces cerebral perfusion pressure, however, the lower limit of autoregulation is approached, and risks of cerebral ischemia increase.…”

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confidence: 99%

EEG monitoring for induced hypotension for surgery of intracranial aneurysms.

Jones¹,

Chiappa²,

Young³

et al. 1979

Stroke

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SUMMARY EEG was monitored at bilateral scalp sites outside the operative field during hypotensive aneurysm surgery in 21 patients. Mean arterial blood pressure at axillary level was 50-60 mm Hg (average 55 mm) for 1.9-5.3 hours (average 3.6). Four new deficits were noted immediately post-operatively, all related to the operated site: these were attributable to intra-operative rupture with forced vascular clipping, vasospasm, or edema. In no instance was hypotension solely responsible for a new deficit. EEG showed persistent slowing in relation to surgery in only 1 patient, where aneurysmal rupture led to severe hypotension, forced clipping of 1 posterior cerebral artery, and subsequent brain stem infarction. In the 3 other patients with fresh focal postoperative deficits, no persistent intraoperative EEG changes were observed. EEG monitoring did not detect ischemia in these 3 patients because 1) hypotension was moderate and did not perse cause new deficit, and 2) EEG electrodes did not survey the area at maximal risk, namely the operative field. EEG scalp electrodes near but outside the operative site do not seem useful for monitoring cerebral function in the region of aneurysm surgery. Epidural or cortical electrodes in the operative field may prove to be more useful.Stroke Vol 10, No 3, 1979RUPTURE OF an intracranial aneurysm during surgery remains a threat even in the era of microsurgery. Profound controlled hypotension reduces the risk of rupture and aids dissection. 1 Hypotension "defuses" the aneurysm by markedly decreasing wall tension. As one reduces cerebral perfusion pressure, however, the lower limit of autoregulation is approached, and risks of cerebral ischemia increase. This is particularly true when subarachnoid hemorrhage or surgical manipulation has already compromised autoregulation. Therefore, reliable techniques are needed for monitoring the CNS response to lowered blood pressure during aneurysm surgery.Since the electroencephalogram (EEG) continuously assesses certain aspects of electrophysiologic function of the brain, this test seemed potentially useful for monitoring hypotension during aneurysm surgery. EEG monitoring during carotid endarterectomy during cardiopulmonary bypass can likewise warn of cerebral ischemia during hypotension. In a series of 75 patients undergoing cardiopulmonary bypass, intraoperative EEG accurately predicted postoperative neuropsychiatric deficits and in several instances ischemic EEG changes were reversed by raising mean arterial blood pressure." Therefore, we have studied the clinical usefulness of intraoperative EEG as a monitor of the CNS response to induced hypotension during aneurysm surgery. Methods PatientsTwenty-one patients undergoing aneurysm surgery were studied. Characteristics of these patients are

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Anaesthesia

Whitby¹

1986

Subarachnoid Haemorrhage

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A Technique of Anesthesia with Induced Hypotension for Surgical Correction of Intracranial Aneurysms

Cited by 29 publications

References 0 publications

Autoregulation of cerebral blood flow during controlled hypotension in baboons

Autoregulation of cerebral blood flow during controlled hypotension in baboons

EEG monitoring for induced hypotension for surgery of intracranial aneurysms.

Anaesthesia

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