Experimental cerebral vasospasm: resolution by chlorpromazine

Experimental cerebral vasospasm: resolution by iloprost

A new stable analogue of prostacyclin, iloprost, was tested on the basilar artery of anaesthetized rabbits constricted by electrical stimulation and intracisternal injection of autologous blood. The vasospasm induced by these stimuli was effectively relieved (about 100%) by topical application of iloprost, a stable analogue of prostacyclin (PGI2), and no constriction occurred on further stimulation within one hour. The mechanisms of the action of iloprost and its possible therapeutic value in subarachnoid haemorrhage are discussed.

Accumulation of intimal platelets in cerebral arteries following experimental subarachnoid hemorrhage in cats

From 2 hours to 23 days following experimental subarachnoid hemorrhage, the accumulation of indium-111-labeled platelets on the intimal surface of the middle cerebral artery was studied in 23 cats. Subarachnoid hemorrhage was produced by transorbital rupture of the right middle cerebral artery. Of the 23 cats, 17 exhibited right middle cerebral artery/left middle cerebral artery radioactivity ratios of greater than 1.25. When these results were compared with those of 12 control cats, 0.001 less than p less than 0.005 (chi2 test). Thus, the results from the control and experimental groups are significantly different and indicate early (after 2 hours) preferential accumulation of intimal platelets in the ruptured right middle cerebral artery compared with the unruptured left middle cerebral artery and new platelet deposition continuing for up to 23 days. However, the experimental group did not reveal a clear pattern for platelet accumulation following subarachnoid hemorrhage. There was no simple correlation between the magnitude of the radioactivity ratios and the time after hemorrhage when the cats were killed although the ratios for 2 hours to 7 days seemed greater than those for 8 to 23 days. Assuming the pivotal role of platelets in the angiopathy of subarachnoid hemorrhage, the administration of antiplatelet agents as soon as possible following its occurrence may be of value.

Cerebral vasospasm

Cerebral vasospasm is an important component of pathological entities such as migraine, subarachnoid hemorrhage (SAH), head trauma, post cerebral ischemia and/or hypoxia. The mechanisms underlying cerebral vasospasm in these diseases are not completely understood. Neurochemical and morphological factors involved in the cerebral circulation control are reviewed in this article. The circulatory changes observed after subarachnoid hemorrhage are taken as a model. It is concluded that multiple biochemical, physiological and morphological factors are involved in the cerebral vascular responses after SAH. Possible treatment alternatives for cerebral vasospasm based on its etiology are discussed.

Cerebral resuscitation: pathophysiology and therapy

The interest in the possibility of cerebral resuscitation has been growing exponentially during the last decade. It became clear that pharmacotherapeutic interaction can possibly alter the outcome of cerebral hypoxia/ischemia. The present review is an attempt to provide an organizational framework for a systematic integration of studies specifically dealing with pharmacological treatment post-insult.

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.

Cerebral vasospasm following aneurysmal subarachnoid hemorrhage

Cerebral vasospasm following aneurysmal subarachnoid hemorrhage is one of the most important causes of cerebral ischemia, and is the leading cause of death and disability after aneurysm rupture. There are two definitions of cerebral vasospasm: angiographic and clinical. Care must be exercised to be certain that it is clear which entity is being addressed. The diagnosis of the clinical syndrome is one of exclusion and can rarely be made with absolute certainty. The pathogenesis of cerebral vasospasm is poorly understood. Most current theories focus on the release of factors from the subarachnoid clot. More attention must be given to the role of endothelial damage and alterations in the blood-arterial wall barrier. The application of modern techniques for studying vascular smooth muscle which have been developed as a result of research in the areas of hypertension and atherosclerosis must be applied to the problem of cerebral vasospasm. A stress test to select patients with angiographic arterial narrowing who have adequate cerebral vascular reserve to undergo surgery should be developed. The optimal treatment of vasospasm awaits development of agents for blocking or inactivating spasmogenic substances or blocking arterial smooth muscle contraction. Rheological or hemodynamic manipulations to prevent or reverse ischemic consequences of vasospasm are relatively effective, but complicated and hazardous, and should be viewed principally as interim measures awaiting development of more specific therapies for the arterial narrowing.

Effects of chlorpromazine on experimental delayed cerebral vasospasm

Experimental delayed cerebral vasospasm was produced in the canine basilar artery by intracisternal injections of blood 2 days apart. The spastic basilar artery was exposed via the transclival route under a surgical microscope, and was dilated by topical application of chlorpromazine, a calmodulin antagonist. Dilatation was dose-dependent, with a median effective dose of 37 +/- 16 microM. In addition, 100 microM chlorpromazine was inserted into the cisterna magna until the intracranial pressure (ICP) reached 200 mm H2O for 30 minutes, inducing a complete reversal of angiographic delayed cerebral vasospasm in two of five animals. In other studies, the intracisternal perfusion of 100 microM chlorpromazine at 1.48 ml/min for 30 minutes with an ICP of less than 200 mm H2O induced no serious abnormalities in mean arterial blood pressure and pulse rate of normal animals. Electroencephalography during the intracisternal perfusion of chlorpromazine showed a slight to moderate increase in occurrence of theta waves. No neurological deficits or significant histological abnormalities ascribable to intracisternal chlorpromazine were found.

Responses of isolated canine basilar artery and human platelet to chlorpromazine and amitriptyline

Sustained contraction of isolated canine basilar artery was induced by addition of prostaglandin F2 alpha, prostaglandin E2, hemoglobin-containing solution, or serum. Human platelet aggregation was induced by 1.0 microM adenosine diphosphate. The sustained contraction of basilar artery and the aggregation of platelet, particularly its secondary aggregation, were inhibited in a dose-dependent manner by addition of chlorpromazine or amitriptyline; calmodulin antagonist. The molar concentrations at 50% inhibition by chlorpromazine or amitriptyline were 5.9 to 7.7 microM or 28 to 39 microM for the contraction of basilar artery and 57 microM or 111 microM for the secondary aggregation of platelet. The results were discussed mainly on the basis of interaction of psychotropic drugs and Ca2+, calmodulin-dependent enzymes, particularly myosin light chain phosphorylation.