Postoperative hemodynamic and metabolic changes in patients with subarachnoid hemorrhage.

Abstract

Positron emission tomography was performed using an oxygen-15 gas inhalation technique to measure regional cerebral blood flow, metabolic rate for oxygen, oxygen extraction fraction, and cerebral blood volume in 13 patients with subarachnoid hemorrhage during the period of delayed vasospasm after surgery as well as in 10 volunteers as controls. Compared with the controls, the patients showed decreased hemoglobin concentration and decreased total arterial oxygen content due to postoperative hemodilution. Global reductions in the metabolic rate for oxygen and in the tissue oxygen supply were noted even in the apparently normal cortex of the patients in spite of adequate blood flow and adequate oxygen extraction fraction. In addition, regional reductions in blood flow and in perfusion reserve were seen in the cortical territory corresponding to cerebral vasospasm. Our results indicate that two processes are involved in the pathophysiology of cerebral vasospasm: 1) generalized impairment of oxygen metabolism with a reduced tissue oxygen supply, even in the apparently normal cortex, and 2) additional impairment of regional perfusion in the territory of vasospasm. (Stroke 1989;20:1504-1510 C erebral vasospasm is one of the most important causes of cerebral dysfunction after aneurysmal rupture. It is generally believed that neurologic symptoms become overt as arteries narrow and blood flow falls below the ischemic threshold.1 However, cerebral function during vasospasm might be affected by factors other than low perfusion, such as possible toxicity from subarachnoid clots 2 -4 or changes in the patient's general condition due to postoperative management. 56Cerebral vasospasm also differs from other causes of cerebral ischemia in its pathogenesis, in the duration and distribution of vascular narrowing, and in the reversibility of low perfusion. Thus, the hemodynamic and metabolic sequences during vasospasm may not necessarily be similar to those Received February 1, 1989; accepted June 23, 1989. during acute ischemia, which have been described in humans in previous positron emission tomography (PET) studies. 7 -8 The aim of our study was to investigate the pathophysiologic mechanism of cerebral dysfunction during the period of delayed vasospasm after subarachnoid hemorrhage (SAH), in addition to clarifying the problems of current postoperative management of SAH patients under usual clinical settings. Subjects and MethodsWe selected 13 SAH patients, nine women and four men, mean age 50 (range 25-70) years between June 1986 and June 1988. We also selected 10 persons without SAH, seven men and three women with a similar age range, to serve as controls.The patients had SAH due to an initial aneurysmal rupture in the anterior circulation; no history of other intracranial, cardiopulmonary, or metabolic disease; no intracerebral hematoma either on admission or during their entire clinical course; and underwent successful neck-clipping of aneurysms without any complications related to either surgery or anesthesia. The dia...

Effect of hemodilution on cerebral hemodynamics and oxygen metabolism.

“…In the Scandinavian Stroke Study group, the dilution was from 44.3% to 37.1% after 5 days 22 ; in the Italian Stroke Study Group, the decrease was from 43% to 37% after 2 days. 23 We designed the present hemodilution protocol after considering that the optimal hematocrit reduction in the human brain is not established 91213 ; that many of our postoperative neurosurgery patients are in a state of moderate hemodilution, similar to that induced in this study 14 ; and that the acute effect of hemodilution is most important, 22 -24 but a more aggressive strategy may have adverse effects if it is applied to patients with ischemic stroke. 23 We thus studied the immediate effect of slightly hypervolemic, moderate hemodilution in normal human brains.…”

“…However, a similar degree of hemodilution can easily occur in many postoperative neurosurgery patients. 14 This can be tolerated in most patients, but might be dangerous in those with delayed vasospasm after subarachnoid hemorrhage. Further study is needed to determine if that is the case.…”

Impact of Cerebral Microcirculatory Changes on Cerebral Blood Flow During Cerebral Vasospasm After Aneurysmal Subarachnoid Hemorrhage

“…[5][6][7] The weak response to the PaCO 2 or acetazolamide administration has been attributed to maximal dilation in the peripheral arterioles in an attempt to maintain sufficient CBF in the face of decreased cerebral perfusion pressure (CPP) due to vasospasm. Increased cerebral blood volume (CBV) after SAH detected by positron emission tomography (PET) 8,9 or the radioisotope tracer method 10 could explain this maximal dilation of peripheral arterioles.…”

Assessment of Pre- and Post-Operative Cerebral Perfusion in Anterior Circulation Intracranial Aneurysm Clipping Patients at Hospital Sungai Buloh Using CT Perfusion Scan and Correlations to Fisher, Navarro and WFNS Scores

“…Reduction in cerebral blood flow is associated with a reduction in cerebral metabolism (11,15). This reduction in cerebral metabolism, measured by CMRO 2 , occurs in the early stage after an intracranial aneurysm ruptures, prior to the onset of vasospasm (19).…”