Changes in cerebral blood flow and metabolism following intraarterial or local administration of nimodipine, before and after experimental subarachnoid hemorrhage in baboons

Continuous Local Intra-arterial Nimodipine Administration in Severe Symptomatic Vasospasm After Subarachnoid Hemorrhage

BACKGROUND:

Cerebral vasospasm (CV) is a potentially disastrous consequence of subarachnoid hemorrhage despite medical treatment. Nimodipine is a potent drug for vessel relaxation, but side effects may preclude a sufficient dose.

OBJECTIVE:

To explore whether continuous local intra-arterial nimodipine administration (CLINA) can reverse vasospasm and prevent delayed ischemic neurological deficit.

METHODS:

Six consecutive subarachnoid hemorrhage patients (5 women; mean age, 47.2 years) with severe CV despite maximum medical therapy underwent CLINA within 2 hours after the onset of clinical symptoms. After anticoagulation, microcatheters were inserted distally in the concerning supra-aortic vessels. Glyceryl trinitrate injection (2 mg) was followed by CLINA (nimodipine 0.4 mg/h for 70-147 hours). Duration of CLINA was determined by neurological status, transcranial Doppler sonography, and partial tissue oxygen pressure values.

RESULTS:

In all patients, neurological deficits improved or partial tissue oxygen pressure values returned to normal and transcranial Doppler sonography confirmed a reduced blood flow velocity within 12 hours. Magnetic resonance imaging showed no ischemic lesion caused by CV. Neurological outcome was good (modified Rankin Scale score, 0–2) in 3 patients, whereas 1 patient had a moderate clinical outcome (modified Rankin Scale score, 3–4) and 2 patients had a poor outcome (modified Rankin Scale score, 5) because of the SAH.

CONCLUSION:

Preliminary data show that CLINA is a straightforward, effective, and safe option for patients with severe CV refractory to medical therapy. Dilation of spastic arteries starts within a few hours and is lasting. Indication for CLINA is peripheral and diffuse CV at any location.

Anesthesia for Endovascular Neurosurgery

Endovascular neurosurgical procedures are complex, requiring significant planning, foresight, and coordination. The neuroanesthetist is an integral part of these procedures, organizing efforts of the technicians and nurses and responding to the needs of the neurointerventionalist. The purpose of this article is to review, in detail, the role of the neuroanesthetist in the endovascular operating room. An overview of all areas either partially or completely managed by the anesthetist is provided.

Experimental isobaric subarachnoid hemorrhage: regional mitochondrial function during the acute and late phase

Patients treated for aneurysmal subarachnoid hemorrhage show, in the long-term follow up, an elevated rate of cognitive disturbances that are mainly related to the impact of the initial bleeding: the neurotoxic effects of blood deposition in subarachnoidal spaces may result in a diffuse encephalopathy, but the intrinsic mechanism and the biochemical correlates are not known. In the present study we have evaluated mitochondrial function after experimental induction of subarachnoid hemorrhage. Mitochondrial function was evaluated in four different rat brain areas (frontal cortex, occipital cortex, hippocampus, and brain stem) after experimental isobaric subarachnoid hemorrhage in rats. Subarachnoid hemorrhage was induced by injecting 0.07 mL of arterial autologous blood into the cisterna magna. Intracranial pressure did not significantly increase. The nonsynaptic mitochondrial fraction was isolated from different rat brain areas, and the maximal rate of enzymatic reactions of some key enzymatic activities related to the Krebs cycle [nicotinamide adenine dinucleotide (oxidized form) (NAD+)-isocitrate dehydrogenase, citrate synthase, and succinate dehydrogenase] and of the electron transfer chain (cytochrome oxidase) were evaluated. The nonsynaptic mitochondrial fraction was utilized also to check parameters related to the mitochondrial respiration: state 3, state 4, uncoupled state, respiratory control ratio, and adenosine 5'-diphosphate/oxygen ratio. The biochemical parameters were measured at 1 and 72 hours after the subarachnoidal injection of blood. Subarachnoid hemorrhage did not affect the mitochondrial enzymatic activities both at 1 and 72 hours, while the mitochondrial enzymatic activities parameters were significantly affected: in particular, a significant decrease of respiratory control ratio in all tested brain areas was demonstrated. The increased mitochondrial vulnerability in the delayed phases could be one of the biochemical correlates of post-hemorrhagic encephalopathy.

Changes in contractile response and effect of a calcium antagonist, nimodipine, in isolated intracranial arteries of baboon following experimental subarachnoid hemorrhage

Isolated pial arteries from a previously well-characterized model of experimental subarachnoid hemorrhage (SAH) in baboon were tested for their contractile response to 5-hydroxytryptamine (5-HT), norepinephrine (NE), and prostaglandin F2 alpha (PGF2 alpha) and the effect of the calcium antagonist, nimodipine. Autologous blood was injected cisternally at three times with one-day intervals to a total amount of 11.5-29.5 ml (mean: 18.5 ml), and the animals were killed 7 days after the first injection. Untreated animals served as controls. The degree of maximum contraction (EAm) with 5-HT and NE in the control situation was for the three arteries tested in the order middle cerebral greater than anterior cerebral greater than basilar artery. Experimental SAH markedly increased EAm, by 190-370 percent above control values (depending on type of vessel) for 5-HT and 170-185 percent for NE. In addition, the sensitivity to 5-HT was significantly increased, as evidenced by a left-shift of the concentration-response curve. Previous exposure of the artery to 10(-6) M nimodipine reduced the contractile response of both amines to approximately half, the inhibition being slightly less pronounced post-SAH. When vessels were contracted beforehand with the amines or with PGF2 alpha, followed by administration of increasing amount of nimodipine (10(-9) M to 10(-6) M), a concentration-dependent relaxation was obtained by up to 60 percent of the original level. This relaxing effect was significantly less following SAH in the experiments with NE and PGF2 alpha compared to 5-HT; the contraction in the presence of 5-HT did not differ before and after experimental SAH. The experiments show that SAH markedly enhances the intrinsic activity for both 5-HT and NE. Nimodipine inhibits the contractile response less efficiently following experimental SAH. The difference in the responsiveness to 5-HT on the one hand, and to NE and PGF2 alpha on the other, could be due to differences in the blood-induced alterations of those calcium channels that are influenced by the calcium antagonist, nimodipine.

Photothrombotic occlusion of rat middle cerebral artery: histopathological and hemodynamic sequelae of acute recanalization

The histopathological and hemodynamic consequences of photochemically induced middle cerebral artery (MCA) thrombosis and recanalization were studied in the rat. Recanalization of the thrombosed MCA segment was achieved by the topical application of nimodipine at 1 h following photochemically induced occlusion. Pathological consequences of permanent and temporary occlusion were compared by morphometric procedures 7 days following thrombus formation. Rats with permanent thrombosis exhibited consistent infarction of both striatum and cortex. MCA recanalization at 1 h was associated with a significant reduction in total infarct volume. In recanalized rats, small cortical infarcts, confined to the peripheral MCA territory, were observed in only three of six rats. In contrast, a mixed pattern of infarction and ischemic cell damage was documented throughout the striatum in all rats. Local CBF (1CBF), measured autoradiographically, was significantly reduced in the MCA territory following 1 h of MCA occlusion, especially within the striatum. At 1 h after recanalization, 1CBF recovered within the previously ischemic brain regions to greater than 50% of control. Perfusion deficits were detected by carbon black infusion within focal areas of the striatum following reperfusion. Thus, cortical neurons appear to tolerate 1 h of MCA occlusion in this model. In contrast, reperfusion following 1 h of photochemically induced MCA occlusion gives rise to selective injury to the striatum.

Effect of nimodipine on mitochondrial respiration in different rat brain areas after subarachnoid haemorrhage

The mitochondrial respiration was evaluated in three different rat brain areas (cerebral cortex, hippocampus and brain stem) after experimental subarachnoid haemorrhage (SAH). The haemorrhage was induced by injecting 0.35 ml of autologous arterial blood into cisterna magna. Intravenous administration of Nimodipine (2 micrograms/kg/min for 30 minutes) was started immediately after the haemorrhage induction. At the set time (1 hour after SAH procedure), animals were sacrificed and non-synaptic mitochondria from the above mentioned areas were isolated. The following respiratory parameters were evaluated utilizing glutamate plus malate and succinate plus rotenone as substrates: state 3, state 4, uncoupled state, respiratory control ratio (RCR) and ADP/O ratio. SAH significantly influences respiratory parameters, mainly RCR; the cerebral cortex and brain stem seem to be more sensitive during the acute phase of vasospasm which follows SAH procedure. Nimodipine treatment significantly ameliorates mitochondrial respiratory conditions.

Cerebrovascular and metabolic changes during the delayed vasospasm following experimental subarachnoid hemorrhage in baboons, and treatment with a calcium antagonist

A model has been designed in baboons for simulating the clinical situation during the late phase of vasospasm in patients with subarachnoid hemorrhage (SAH). A total amount of 14-33 ml autologous blood was injected into the cisternal system on 3 occasions in the course of 4 days. Neurological symptoms were seen, and the mortality rate was 29%. Angiography 3 days after the last injection showed arterial vasoconstriction amounting to 23% in the vertebro-basilar system, and 11% (right) and 18% (left) in the carotid system. Cerebral blood flow (CBF) measured by the intra-arterial 133Xe technique and the cerebral metabolic rate of oxygen (CMRO2) were reduced by 18% and 11%, respectively. The hypercapnic CBF response was significantly impaired, from a mean of 3.90 ml/100 g/min to 1.72 ml/100 g/min of flow increase for each mm Hg elevation of paCO2. Autoregulation, tested by administration of angiotensin II, was also significantly affected as evidenced by a pressure-dependent increment of CBF during hypertension in 5 out of 7 animals tested. The impaired autoregulation was reflected in the autoregulatory index, which in the whole group increased from 0.06 ml/100 g/min for each mm Hg increase in MABP in the pre-SAH animals to 0.29 ml/100 g/min per mm Hg post-SAH. Treatment with the calcium antagonist, nimodipine (0.5 microgram/kg/min i.v. during 45 min), enhanced CBF significantly by 17% before experimental SAH, whereas after SAH the effect was slight and did not reach statistical significance; CMRO2 was not significantly affected in either group. Intravenous nimodipine combined with hypertension resulted in a marked increase in the autoregulatory index to 1.58 ml/100 g/min per mm Hg in pre-SAH animals and a less pronounced increment to 0.58 ml/100 g/min per mm Hg following experimental SAH. The beneficial effect of nimodipine reported in SAH patients is therefore, in view of our findings, more likely due primarily to a protective mechanism at the cellular level than to an influence on the vascular bed.