Experimental chronic cerebrovascular spasm in the monkey: an assessment of the functional changes in the cerebral arteries and their protection by diltiazem

Correspondence between the time course of cerebral vasospasm and the level of cerebral dopamine-β-hydroxylase in rabbits

The aim of the study was to explore whether the biphasic time course of the vasospastic response following experimental subarachnoid hemorrhage is associated with any concomitant changes in the amount of cerebral dopamine beta-hydroxylase in the noradrenergic central nervous system. A single-hemorrhage animal model was used. Rabbits were sacrificed from day 1 to day 8 after subarachnoid hemorrhage. Intimal corrugation of the basilar artery and the amount of cerebral dopamine beta-hydroxylase in the hypothalamus and brain stem were measured each day. Vasospastic changes occurred in the biphasic manner following subarachnoid hemorrhage. More profound vasospastic corrugation occurred in the acute phase, followed by a slightly less intense corrugation in the chronic phase (between days 5 and 8 after the subarachnoid hemorrhage). Simultaneously, a clear concomitant biphasic time course developed in the form of an increased amount of dopamine-beta-hydroxylase in the noradrenergic nervous system of the rabbit hypothalamus and brain stem during the acute and chronic phases after the subarachnoid hemorrhage. Statistically significant correlation between basilar artery corrugation and the amount of dopamine beta-hydroxylase was found. These results suggest the possible role of the central sympathetic system in the pathogenesis of vasospasm. At the same time, this study demonstrates the chronological similarity of the vasospastic development after subarachnoid hemorrhage in the animal experimental model with the human time course of vasospasm.

Inflammatory cell adhesion molecules in ischemic cerebrovascular disease

BACKGROUND

In this review we discuss the role of inflammatory cell adhesion molecules (CAMs) in ischemic stroke and in delayed cerebral ischemia after subarachnoid hemorrhage. Vascular endothelial cells and leukocytes express several inflammatory adhesion receptors, the most important of which are the selectins, immunoglobulin gene superfamily CAMs, and beta2 integrins. They mediate the transmigration process of leukocytes to the abluminal side of the endothelium.

SUMMARY OF REVIEW

There is ample evidence from animal models of middle cerebral artery occlusion that expression of CAMs is associated with cerebral infarct size. Absence of CAMs in knockout animals resulted in reduced infarct size. When middle cerebral artery occlusion in experimental stroke was followed by reperfusion, administration of anti-CAM antibodies decreased infarct size. Thus far, anti-CAM treatment has not been successful in patients with ischemic stroke. Inflammatory CAM may also play a role in the pathogenesis of delayed cerebral ischemia after subarachnoid hemorrhage. In animal models, increased expression of CAMs has been observed in vasospastic arteries. Increased concentrations of CAMs have also been found in cerebrospinal fluid of patients with subarachnoid hemorrhage.

CONCLUSIONS

Further research on the role of inflammatory CAMs in the pathogenesis of ischemic cerebrovascular disorders should lead to new diagnostic and therapeutic strategies.

Effect of nicardipine and diltiazem on internal carotid artery blood flow velocity and local cerebral blood flow during cerebral aneurysm surgery for subarachnoid hemorrhage

STUDY OBJECTIVE

To determine the hemodynamic effects of a bolus injection of nicardipine 1 mg or diltiazem 5 mg on local cerebral blood flow (LCBF) and internal carotid blood flow velocity (ICBFV) with isoflurane anesthesia.

DESIGN

Randomized study.

SETTING

Inpatient neurosurgery and anesthesia clinic at a city hospital.

PATIENTS

26 patients with subarachnoid hemorrhage who were scheduled for cerebral aneurysm clipping.

INTERVENTIONS

A bolus injection of either nicardipine or diltiazem was administered to patients whose systolic blood pressure increased to over 150 mmHg after opening of the dura.

MEASUREMENTS AND MAIN RESULTS

After the bolus injection, both drugs rapidly decreased arterial blood pressure. Nicardipine increased LCBF [before injection, 42.1 +/- 12.3 ml/100 g/min; after injection, 47 +/- 10.7 ml/100g/min; (p < 0.05 vs control); after recovery, 42.4 +/- 11.1 cm/sec], but diltiazem did not change LCBF. Nicardipine 1 mg moderately increased ICBFV [before injection, 34.2 +/- 9.3 cm/sec; after injection, 40.6 +/- 8.7 cm/sec (p < 0.01 vs. control); after recovery, 34.1 +/- 8.9 cm/sec], but diltiazem did not change ICBFV. In addition, venous partial oxygen pressure and saturation of the internal jugular did not change throughout the study. There was a close correlation between presurgical neurologic status and LCBF (rs = -0.743; p < 0.01) and ICBFV (rs = -0.721; p < 0.01).

CONCLUSIONS

Nicardipine increased LCBF and ICBFV, but diltiazem did not change either. These results suggest that both drugs are useful and safe for the treatment of intraoperative hypertension during cerebral aneurysm surgery.

Vasodilators during cerebral aneurysm surgery

The objective of this review is to review the anaesthetic implications of vasoactive compounds particularly with regard to the cerebral circulation and their clinical importance for the practicing anaesthetist. Material was selected on the basis of validity and application to clinical practice and animal studies were selected only if human studies were lacking. Hypotensive drugs have been used to induce hypotension and in the treatment of intraoperative hypertension during cerebral aneurysm surgery. After subarachnoid haemorrhage, cerebral blood flow is reduced and cerebral vasoreactivity is disturbed which may lead to brain ischaemia. Also, cerebral arterial vasospasm decreases cerebral blood flow, and may lead to delayed ischaemic brain damage which is a major problem after subarachnoid haemorrhage. Recently, the use of induced hypotension has decreased although it is still useful in patients with intraoperative aneurysm rupture, giant cerebral aneurysm, fragile aneurysms and multiple cerebral aneurysms. In this review, a variety of vasodilating agents, prostaglandin E1, sodium nitroprusside, nitroglycerin, trimetaphan, adenosine, calcium antagonists, and inhalational anaesthetics, are discussed for their clinical usefulness. Sodium nitroprusside, nitroglycerin and isoflurane are the drugs of choice for induced hypotension. Prostaglandin E1, nicardipine and nitroglycerin have the advantage that they do not alter carbon dioxide reactivity. Local cerebral blood flow is increased with nitroglycerin, decreased with trimetaphan and unchanged with prostaglandin E1. Intraoperative hypertension is a dangerous complication occurring during cerebral aneurysm surgery, but its treatment in association with subarachnoid haemorrhage is complicated in cases of cerebral arterial vasospasm because fluctuations in cerebral blood flow may be exacerbated. Hypertension should be treated immediately to reduce the risk of rebleeding and intraoperative aneurysmal rupture and the choice of drugs is discussed. Although the use of induced hypotension has declined, the control of arterial blood pressure with vasoactive drugs to reduce the risk of intraoperative cerebral aneurysm rupture is a useful technique. Intraoperative hypertension should be treated immediately but the cerebral vascular effects of each vasodilator should be understood before their use as hypotensive agents.

The effect of a new calcium antagonist, TA3090 (clentiazem), on experimental transient focal cerebral ischemia in cats

BACKGROUND AND PURPOSE

TA3090 (Clentiazem) has been shown to have cerebrovascular protective properties in three experimental studies. An in vivo investigation was undertaken to determine its effects on pial arteries and cerebral blood flow and its therapeutic value in transient focal cerebral ischemia.

METHODS

This experiment was divided into two protocols. In the first, 200 or 400 micrograms/kg per hour TA3090 was administered continuously for 3 hours in cats without ischemic insult (n = 6 for each group). The effects on pial arteries and cerebral blood flow were estimated. In the second protocol, 400 micrograms/kg per hour TA3090 (treated group, n = 14) or physiological saline (control group, n = 10) was administered 5 minutes before 1 hour of middle cerebral artery occlusion in cats. The effects on the pial arteries and cerebral blood flow were observed continuously, followed by autoradiography for a quantitative measurement of cerebral blood flow 5 hours after middle cerebral artery recirculation. The volumes of the cerebral edema and infarct were estimated by planimetry from cerebral preparations made for histological examination.

RESULTS

Pial arteries dilated by up to approximately 10% in the 400-micrograms group and 3% in the 200-micrograms group 30 minutes after administration of TA3090. Increases in cerebral blood flow of about 10% in the 400-micrograms group and 2% in the 200-micrograms group were demonstrated with laser Doppler flowmetry. In the second protocol, dilatation of pial arteries was significantly smaller during and after the ischemic insult in the treated group compared with the control group (p < 0.01). Cerebral blood flow decreased less significantly during ischemia (p < 0.01 at the end of ischemia) and increased less significantly after ischemia (p < 0.01 at the end) in the treated group compared with the control group. Autoradiography showed a more remarkable increase in cerebral blood flow due to luxury perfusion in the cerebral cortex, which was mainly perfused by the middle cerebral artery on the affected side in the control group (p < 0.01). Cerebral blood flow in the cerebral cortex, thalamus, and caudate nucleus on the contralateral side of the treated group increased by about 20% more than that of the control group (p < 0.05). Cerebral edema and infarction were much smaller in the treated group than in the control group (p < 0.01).

CONCLUSIONS

1) TA3090 dilates pial arteries and increases cerebral blood flow in normal brain regions in a dose-response fashion; 2) in ischemic regions compared with those in untreated animals, TA3090 results in a lesser reduction of cerebral blood flow during ischemia and in a lesser degree of hyperemia during reperfusion; 3) TA3090 is associated with less pial artery dilatation during ischemia, presumably due to improved collateral flow; and 4) the improved hemodynamic state with TA3090 is associated with significant reduction of cerebral edema and infarct size.

Longitudinal time course of reversible and irreversible components of chronic cerebrovasospasm of the rabbit basilar artery

Multiple injections of autologous blood were made around the basilar artery of rabbits through a silicone catheter placed into the prepontine cistern. The total blood injected was 3 ml/kg in aliquots of 0.5 to 0.8 ml over a 4-hour period. Control angiograms were obtained 7 days before this procedure. Groups of animals were examined by angiography on each of 9 days after the injections of blood. An angiogram was obtained 15 minutes after the first injection of blood, 20 seconds after the intra-arterial injection of a maximum dilating dose of papaverine. All surviving animals showed basilar artery narrowing, which was greatest 24 hours after the hemorrhage, when the vessel diameter was reduced to 54% of the control value. The narrowing then decreased to a reduction of about 30%, which was maintained throughout the rest of the study period. A papaverine-resistant component of narrowing was not seen until the 3rd day. It increased progressively to Day 9 when it represented 63% of the total. This model has a number of features that are reminiscent of human cerebrovasospasm, including the fact that there is an initial phase of narrowing that is completely reversed by an intra-arterially administered vasodilator, and a second phase beginning on Day 3 which exhibits a progressively increasing papaverine-resistant component.

Clentiazem reduces infarct size in rabbit middle cerebral artery occlusion

We assessed the value of pretreatment with clentiazem (8-chlorodiltiazem), a diltiazem derivative with cerebroselective properties, on the consequences of surgical occlusion of the middle cerebral artery via a transorbital approach in 38 rabbits. Nineteen rabbits received 1.7 (n = 5), 5 (n = 8), or 15 (n = 6) mg/kg clentiazem orally four times a day for 24 hours before and 48 hours after occlusion. Upon sacrifice, a segment of the right middle cerebral artery distal to the occlusion and a corresponding segment from the nonoccluded left middle cerebral artery were mounted on myographs for in vitro study of their reactivity to histamine, acetylcholine, serotonin, norepinephrine, and electrical stimulation of intramural sympathetic nerves. Morphometric measurements of 2,3,5-triphenyltetrazolium chloride-stained brain slices permitted us to estimate infarct volume. Pretreatment with 1.7, 5, and 15 mg/kg clentiazem significantly reduced infarct volume (p less than 0.05, p less than 0.01, and p less than 0.01, respectively). Mean infarct volume of the 15 mg/kg-treated group was only 4% that of the untreated group. There were no postoperative deaths in any treated group compared with a death rate of 36% in the untreated group. Mean values for vascular smooth muscle contractility to histamine and relaxation to acetylcholine were significantly enhanced in vessels from treated rabbits. These studies indicate that pretreatment with clentiazem offers cerebral protection and significantly reduces infarct volume as well as arterial wall damage beyond the occlusion.

Comparison of intraluminally versus extraluminally administered nimodipine on serotonin-induced cerebral vascular responses in vitro and in situ

The purpose of our study was to compare the ability of intraluminally and extraluminally administered nimodipine to inhibit serotonin-induced cerebral vascular responses in vitro and in situ. No difference was noted in the ability of nimodipine, whether administered intraluminally or extraluminally, to reduce the contractile response of extraluminally administered serotonin in a closed, pressurized, in vitro bovine middle cerebral artery preparation; histologic studies indicated that the tight endothelial junctions normally found in cerebral arteries remained intact in this preparation. In cats, pretreatment with nimodipine did not significantly reduce the ability of intracisternally injected serotonin to decrease cerebral blood flow; however, nimodipine did reduce the changes in cerebral artery diameter normally noted angiographically after serotonin injection. Although minor differences were noted between the intraluminal and extraluminal routes of administration of nimodipine in situ, in general the effects were comparable.

Functional arterial changes in chronic cerebrovasospasm in monkeys: an in vitro assessment of the contribution to arterial narrowing

Cerebral arteries from monkeys with chronic cerebral vasospasm arising from experimental subarachnoid hemorrhage produced 5-6 days previously were examined for changes in their functional properties in an attempt to understand the basis of the narrowing. Hemorrhage was caused by puncture of the internal carotid artery just proximal to the circle of Willis. Segments taken close to the origins of the anterior and middle cerebral arteries consistently showed decreased distensibility. In addition, they exhibited large, prolonged, spontaneous increases in muscle tone. Other alterations observed include a marked reduction in the capacity of the vessel wall to contract, reduction in constrictor and dilator nerve influences on vascular tone, and some increased sensitivity to serotonin. Small pial arteries (150-200 micron o.d.) from the side of the injury showed large spontaneous irregular increases in tone. It is proposed that 5-6 days after experimental subarachnoid hemorrhage in monkeys the change most responsible for persistent narrowing in the larger arteries is an increased rigidity of the vessel wall. This is probably caused by an inflammatory response. In the smaller arteries, abnormal spontaneous contractile activity is a major factor in narrowing. This activity is not stretch-dependent. We suggest that the initial cause of the arterial narrowing after hemorrhage is the action of vasoactive substances released in the close vicinity of the arterial wall, which lead to tissue damage, abnormal tone, and an inflammatory response with fibrosis.