Effect of nimodipine on platelet function in patients with subarachnoid hemorrhage

The Impact of Enteral Nimodipine on Endothelial Cell Apoptosis in an Animal Subarachnoid Hemorrhage Model

BACKGROUND

Enteral nimodipine is the most evidence-based and widely used drug for the treatment of delayed cerebral ischemia and is known to have various neuroprotective functions. However, the neuroprotective mechanism of nimodipine still remains unclear, and the effects of nimodipine remain ambiguous. Herein, we studied the effect of enteral nimodipine on endothelial apoptosis after subarachnoid hemorrhage (SAH).

METHODS

SAH was experimentally introduced in white rabbits (n = 42) that were grouped as follows: enteral nimodipine (SAH-nimodipine group, n = 14), a control that received normal saline (SAH-saline group, n = 13), and a control without hemorrhage (control group, n = 15). On the third day after SAH induction, the brain stem, including the vertebrobasilar vascular system, was extracted. The effects of enteral nimodipine were analyzed by group using histopathologic analysis, including immunohistochemical staining of apoptosis-related proteins (Bcl2 [anti-apoptotic] and Bax [pro-apoptotic]).

RESULTS

Cytoplasmic vacuolation of smooth muscle cells was observed in two SAH hemorrhagic groups and was more prominent in the SAH-saline group. Endothelial desquamation was observed only in the SAH-saline group. For the basilar artery, expression of Bcl2 and Bax in the SAH-nimodipine group was lower than that in the SAH-saline group, but significant differences were not observed (pBcl2 = 0.311 and pBax = 0.720, respectively). In penetrated arterioles, the expression of Bax in the SAH-nimodipine group was significantly lower than that of the SAH-saline group (p < 0.001). The thickness of the tunica media in the basilar artery was thinner in the SAH-nimodipine group than in the SAH-saline group (p < 0.001).

CONCLUSIONS

This study suggests that enteral nimodipine may have a neuroprotective function by inhibiting endothelial apoptosis in small arterioles and preventing smooth muscle cell proliferation in large arteries.

Role of platelets in the pathogenesis of delayed injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) patients develop delayed cerebral ischemia and delayed deficits (DCI) within 2 weeks of aneurysm rupture at a rate of approximately 30%. DCI is a major contributor to morbidity and mortality after SAH. The cause of DCI is multi-factorial with contributions from microthrombi, blood vessel constriction, inflammation, and cortical spreading depolarizations. Platelets play central roles in hemostasis, inflammation, and vascular function. Within this review, we examine the potential roles of platelets in microthrombi formation, large artery vasospasm, microvessel constriction, inflammation, and cortical spreading depolarization. Evidence from experimental and clinical studies is provided to support the role(s) of platelets in each pathophysiology which contributes to DCI. The review concludes with a suggestion for future therapeutic targets to prevent DCI after aSAH.

Nimodipine Reappraised: An Old Drug With a Future

Nimodipine is a dihydropyridine calcium channel antagonist that blocks the flux of extracellular calcium through L-type, voltage-gated calcium channels. While nimodipine is FDAapproved for the prevention and treatment of neurological deficits in patients with aneurysmal subarachnoid hemorrhage (aSAH), it affects myriad cell types throughout the body, and thus, likely has more complex mechanisms of action than simple inhibition of cerebral vasoconstriction. Newer understanding of the pathophysiology of delayed ischemic injury after a variety of acute neurologic injuries including aSAH, traumatic brain injury (TBI) and ischemic stroke, coupled with advances in the drug delivery method for nimodipine, have reignited interest in refining its potential therapeutic use. In this context, this review seeks to establish a firm understanding of current data on nimodipine's role in the mechanisms of delayed injury in aSAH, TBI, and ischemic stroke, and assess the extensive clinical data evaluating its use in these conditions. In addition, we will review pivotal trials using locally administered, sustained release nimodipine and discuss why such an approach has evaded demonstration of efficacy, while seemingly having the potential to significantly improve clinical care.

Calcium antagonists for aneurysmal subarachnoid haemorrhage

BACKGROUND

Secondary ischaemia is a frequent cause of poor outcome in patients with subarachnoid haemorrhage (SAH). Its pathogenesis has been incompletely elucidated, but vasospasm probably is a contributing factor. Experimental studies have suggested that calcium antagonists can prevent or reverse vasospasm and have neuroprotective properties.

OBJECTIVES

To determine whether calcium antagonists improve outcome in patients with aneurysmal SAH.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (last searched April 2006), MEDLINE (1966 to March 2006) and EMBASE (1980 to March 2006). We handsearched two Russian journals (1990 to 2003), and contacted trialists and pharmaceutical companies in 1995 and 1996.

SELECTION CRITERIA

Randomised controlled trials comparing calcium antagonists with control, or a second calcium antagonist (magnesium sulphate) versus control in addition to another calcium antagonist (nimodipine) in both the intervention and control groups.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the data and assessed trial quality. Trialists were contacted to obtain missing information.

MAIN RESULTS

Sixteen trials, involving 3361 patients, were included in the review; three of the studies were of magnesium sulphate in addition to nimodipine. Overall, calcium antagonists reduced the risk of poor outcome: the relative risk (RR) was 0.81 (95% confidence interval (CI) 0.72 to 0.92); the corresponding number of patients needed to treat was 19 (95% CI 1 to 51). For oral nimodipine alone the RR was 0.67 (95% CI 0.55 to 0.81), for other calcium antagonists or intravenous administration of nimodipine the results were not statistically significant. Calcium antagonists reduced the occurrence of secondary ischaemia and showed a favourable trend for case fatality. For magnesium in addition to standard treatment with nimodipine, the RR was 0.75 (95% CI 0.57 to 1.00) for a poor outcome and 0.66 (95% CI 0.45 to 0.96) for clinical signs of secondary ischaemia.

AUTHORS' CONCLUSIONS

Calcium antagonists reduce the risk of poor outcome and secondary ischaemia after aneurysmal SAH. The results for 'poor outcome' depend largely on a single large trial of oral nimodipine; the evidence for other calcium antagonists is inconclusive. The evidence for nimodipine is not beyond all doubt, but given the potential benefits and modest risks of this treatment, oral nimodipine is currently indicated in patients with aneurysmal SAH. Intravenous administration of calcium antagonists cannot be recommended for routine practice on the basis of the present evidence. Magnesium sulphate is a promising agent but more evidence is needed before definite conclusions can be drawn.

Intravenous magnesium versus nimodipine in the treatment of patients with aneurysmal subarachnoid hemorrhage: a randomized study

OBJECTIVE

The prophylactic use of nimodipine in patients with aneurysmal subarachnoid hemorrhage reduces the risk of ischemic brain damage. However, its efficacy seems to be rather moderate. The question arises whether other types of calcium antagonists offer better protection. Magnesium, nature's physiological calcium antagonist, is neuroprotective in animal models, promotes dilatation of cerebral arteries, and has an established safety profile. The aim of the current pilot study is to evaluate the efficacy of magnesium versus nimodipine to prevent delayed ischemic deficits after aneurysmal subarachnoid hemorrhage.

METHODS

One hundred and thirteen patients with aneurysmal subarachnoid hemorrhage were enrolled in the study and were randomized to receive either magnesium sulfate (loading 10 mg/kg followed by 30 mg/kg daily) or nimodipine (48 mg/d) intravenously until at least postoperative Day 7. Primary outcome parameters were incidence of clinical vasospasm and infarction. Secondary outcome measures were the incidence of transcranial Doppler/angiographic vasospasm, the neuronal markers (neuron-specific enolase, S-100), and the patients' Glasgow Outcome Scale scores at discharge and after 1 year.

RESULTS

One hundred and four patients met the study requirements. In the magnesium group (n = 53), eight patients (15%) experienced clinical vasospasm and 20 (38%) experienced transcranial Doppler/angiographic vasospasm compared with 14 (27%) and 17 (33%) patients in the nimodipine group (n = 51). If clinical vasospasm occurred, 75% of the magnesium-treated versus 50% of the nimodipine-treated patients experienced cerebral infarction resulting in fatal outcome in 37 and 14%, respectively. Overall, the rate of infarction attributable to vasospasm was virtually the same (19 versus 22%). There was no difference in outcome between groups.

CONCLUSION

The efficacy of magnesium in preventing delayed ischemic neurological deficits in patients with aneurysmal subarachnoid hemorrhage seems to be comparable with that of nimodipine. The difference in their pharmacological properties makes studies on the combined administration of magnesium and nimodipine seem promising.

Cerebral Vasospasm After Aneurysmal Subarachnoid Hemorrhage: An Overview of Pharmacologic Management

Cerebral vasospasm remains one of the leading causes of mortality in patients who experience a subarachnoid hemorrhage but survive the initial 24 hours. Vasospasm generally occurs 3-4 days after the initial subarachnoid hemorrhage and peaks at 5-7 days. The pathophysiology of vasospasm is poorly understood, which directly contributes to the inconsistency of management and creates a formidable challenge in clinical practice. Traditionally, hemodilution, hypervolemia, and induced hypertension (so-called triple H therapy); calcium channel blockers; and endovascular therapy have been used as either prophylactic therapy or treatment. However, management of vasospasm varies among physicians and institutions mainly because of a lack of large clinical trials and inconsistent results. Practice has been based primarily on case reports and the preference of each practitioner. Several experimental therapies have been explored; however, large, prospective, randomized controlled trials are needed to elucidate the role of these therapies.

D-dimer Predicts Outcome after Aneurysmal Subarachnoid Hemorrhage: No Effect of Thromboprophylaxis on Coagulation Activity

OBJECTIVE

Approximately one-third of all patients with acute nontraumatic subarachnoid hemorrhage (SAH) experience complications owing to delayed ischemic deficit. We reported recently that enoxaparin 40 mg once daily for 10 days seems safe and demonstrates thromboprophylactic efficacy, but it failed to improve outcome in a randomized SAH trial. In the present study, we assessed hemostatic variables associated with clinical status and outcome of SAH. We also monitored the effect of enoxaparin on activation of coagulation and fibrinolysis after closure of the ruptured aneurysm.

METHODS

Blood samples to measure activation of coagulation and fibrinolysis were collected from 42 patients participating in the enoxaparin trial for acute aneurysmal SAH at four time points: 1) at hospital admission; 2) 12 to 24 hours after aneurysm surgery but before initiation of enoxaparin therapy; 3) 3 hours after the first dose; and 4) at the conclusion of treatment.

RESULTS

At admission, several variables of coagulation and fibrinolysis were elevated and correlated well with clinical status. Specifically, D-dimer levels at all four time points correlated with patients' long-term outcomes. A single dose of enoxaparin suppressed early coagulation activity, but thrombin generation was not inhibited during thromboprophylaxis. However, PAI-1 activity was suppressed.

CONCLUSION

D-dimer offers a useful laboratory tool for assessing early and late clinical severity of SAH. A thromboprophylactic dose of enoxaparin inhibited PAI-1 activity but failed to down-regulate coagulation activity and D-dimer. These findings are compatible with the lack of efficacy of enoxaparin in reducing ischemic deficit after SAH.

Calcium antagonists for aneurysmal subarachnoid haemorrhage

BACKGROUND

Secondary ischaemia is a frequent cause of poor outcome in patients with subarachnoid haemorrhage (SAH). Its pathogenesis has not been elucidated yet, but may be related to vasospasm. Experimental studies have indicated that calcium antagonists can prevent or reverse vasospasm and have neuroprotective properties. Several types of calcium antagonists have been studied in several clinical trials.

OBJECTIVES

To determine whether calcium antagonists improve outcome in patients with aneurysmal SAH.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (September 2003). In addition, we searched MEDLINE (1966 to October 2003) and EMBASE (1980 to October 2003), handsearched two Russian journals (1990 to 2003) and contacted trialists and pharmaceutical companies (in 1995 and 1996) to identify further studies.

SELECTION CRITERIA

All unconfounded, truly randomised controlled trials comparing any calcium antagonist with control.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted the data and assessed trial quality. Trialists were contacted to obtain missing information.

MAIN RESULTS

We analysed 12 trials totalling 2844 patients with SAH (1396 in the treatment group and 1448 in the control group). The drugs analysed were: nimodipine (eight trials, 1574 patients), nicardipine (two trials, 954 patients), AT877 (one trial, 276 patients) and magnesium (one trial, 40 patients). Overall, calcium antagonists reduced the risk of poor outcome: relative risk (RR) 0.82 (95% confidence interval (CI) 0.72 to 0.93); the absolute risk reduction was 5.1%, the corresponding number of patients needed to treat to prevent a single poor outcome event was 20. For oral nimodipine alone the RR was 0.70 (0.58 to 0.84). The RR of death on treatment with calcium antagonists was 0.90 (95% CI 0.76 to 1.07), that of clinical signs of secondary ischaemia 0.67 (95% CI 0.60 to 0.76), and that of CT or MR confirmed infarction 0.80 (95% CI 0.71 to 0.89).

AUTHORS' CONCLUSIONS

Calcium antagonists reduce the risk of poor outcome and secondary ischaemia after aneurysmal SAH. The results for 'poor outcome' depend largely on a single large trial with oral nimodipine; the evidence for nicardipine, AT877 and magnesium is inconclusive. The evidence for nimodipine is not beyond every doubt, but given the potential benefits and modest risks of this treatment, against the background of a devastating natural history, oral nimodipine (60 mg every 4 hours) is currently indicated in patients with aneurysmal SAH. Intravenous administration of calcium antagonists cannot be recommended for routine practice on the basis of the present evidence.

The effect of nimodipine on cerebral oxygenation in patients with poor-grade subarachnoid hemorrhage

Object. Nimodipine has been shown to improve neurological outcome after subarachnoid hemorrhage (SAH); the mechanism of this improvement, however, is uncertain. In addition, adverse systemic effects such as hypotension have been described. The authors investigated the effect of nimodipine on brain tissue PO2.

Methods. Patients in whom Hunt and Hess Grade IV or V SAH had occurred who underwent aneurysm occlusion and had stable blood pressure were prospectively evaluated using continuous brain tissue PO2 monitoring. Nimodipine (60 mg) was delivered through a nasogastric or Dobhoff tube every 4 hours. Data were obtained from 11 patients and measurements of brain tissue PO2, intracranial pressure (ICP), mean arterial blood pressure (MABP), and cerebral perfusion pressure (CPP) were recorded every 15 minutes.

Nimodipine resulted in a significant reduction in brain tissue PO2 in seven (64%) of 11 patients. The baseline PO2 before nimodipine administration was 38.4 ± 10.9 mm Hg. The baseline MABP and CPP were 90 ± 20 and 84 ± 19 mm Hg, respectively. The greatest reduction in brain tissue PO2 occurred 15 minutes after administration, when the mean pressure was 26.9 ± 7.7 mm Hg (p < 0.05). The PO2 remained suppressed at 30 minutes (27.5 ± 7.7 mm Hg [p < 0.05]) and at 60 minutes (29.7 ± 11.1 mm Hg [p < 0.05]) after nimodipine administration but returned to baseline levels 2 hours later. In the seven patients in whom brain tissue PO2 decreased, other physiological variables such as arterial saturation, end-tidal CO2, heart rate, MABP, ICP, and CPP did not demonstrate any association with the nimodipine-induced reduction in PO2. In four patients PO2 remained stable and none of these patients had a significant increase in brain tissue PO2.

Conclusions. Although nimodipine use is associated with improved outcome following SAH, in some patients it can temporarily reduce brain tissue PO2.

No effect of enoxaparin on outcome of aneurysmal subarachnoid hemorrhage: a randomized, double-blind, placebo-controlled clinical trial

Object. From the moment an intracranial aneurysm ruptures, cerebral blood flow is impaired, and this impairment mainly determines the outcome in patients who survive after the initial bleeding. The exact mechanism of impairment is unknown, but activation of coagulation and fibrinolysis correlate with clinical condition and outcome after aneurysmal subarachnoid hemorrhage (SAH). The purpose of this study was to determine whether enoxaparin, a low-molecular-weight heparin, which is a well-known anticoagulating agent, has any effect on the outcome of aneurysmal SAH postoperatively.

Methods. In this randomized, double-blind, single-center clinical trial, 170 patients (85 per group) with aneurysmal SAH were randomly assigned to receive either enoxaparin (40 mg subcutaneously once daily) or a placebo, starting within 24 hours after occlusion of the aneurysm and continuing for 10 days. Analysis was done on an intention-to-treat basis. Outcome was assessed at 3 months on both the Glasgow Outcome and modified Rankin Scales. Patients were eligible for the study if surgery was performed within 48 hours post-SAH, and no intracerebral hemorrhage was larger than 20 mm in diameter on the first postoperative computerized tomography scan.

At 3 months, there were no significant differences in outcome by treatment group. Of the 170 patients, 11 (6%) died, and only 95 (56%) had a good outcome. Principal causes of unfavorable outcome were poor initial condition, delayed cerebral ischemia, and surgical complications. There were four patients with additional intracranial bleeding in the group receiving enoxaparin. The bleeding was not necessarily associated with the treatment itself, nor did it require treatment, and there were no such patients in the placebo group.

Conclusions. Enoxaparin seemed to have no effect on the outcome of aneurysmal SAH in patients who had already received routine nimodipine and who had received triple-H therapy when needed. Routine use of low-molecular-weight heparin should be avoided during the early postoperative period in patients with SAH, because this agent seems to increase intracranial bleeding complications slightly, with no beneficial effect on neurological outcome.

Platelets play an essential role in the aetiology of cerebral vasospasm after subarachnoid haemorrhage

Platelets have long been implicated in the aetiology of cerebral vasospasm (CV) after subarachnoid haemorrhage (SAH). It was noticed that vasospastic CSF (CSF(V)) could be formed in vitro by the mixing of control blood (with platelets) and non-SAH CSF. We also propose a hypothesis for the aetiology of CV after SAH based on this and previous research. This study also aims to determine which blood fraction is responsible for the stimulation of O(2) consumption and vasospasm of blood vessels. Control blood was separated into various fractions and mixed with non-SAH CSF. The activity of the resulting mixture and the blood fraction alone were assessed. Only the fractions containing platelets mixed with CSF showed vasoactivity. These data suggest that platelets plus some component in the CSF produce vasoactive factors with actions similar to CSF(V). This study may help to elucidate the aetiology of CV after SAH.

Anti-phospholipid antibodies and cerebral vasospasm following subarachnoid haemorrhage

Delayed ischaemic deficits due to cerebral vasospasm contribute to the high morbidity and mortality rates associated with subarachnoid haemorrhage. We evaluated the usefulness of measuring anti-phospholipid antibodies (aPLs) for prediction of the occurrence of symptomatic vasospasm and the outcome after subarachnoid haemorrhage. 32 consecutive patients with subarachnoid haemorrhage due to ruptured cerebral aneurysms were studied. They were admitted and operated on within 72 hours after the onset of subarachnoid haemorrhage. aPLs such as lupus anticoagulants, anti-cardiolipin IgG and anti-cardiolipin IgM were measured repeatedly after admission. Furthermore, platelet count, platelet aggregability and plasma platelet factor 4 were also measured. Eleven among the 32 patients (34.4%) showed positive in the examination for aPLs. Although aPLs could not predict symptomatic vasospasm, once symptomatic vasospasm occurred, patients with aPLs frequently demonstrated cerebral infarction and therefore their outcome was worse. aPLs were associated with a severe initial clinical grade and SAH grade on CT scan. Therefore it may explain the association of aPLs with worse outcome. aPLs were detected between 1 and 7 days. Four of 6 patients (67%) with aPLs became negative between 7 and 13 days after subarachnoid haemorrhage. The mechanism of transient aPLs is unclear but it is more likely to occur in the severer grade patients. The reduction in platelet count, the increased platelet aggregability, and the increased plasma platelet factor 4 concentration were also observed in aPLs-positive patients with symptomatic vasospasm.

Hypotensive effect of nimodipine during treatment for aneurysmal subarachnoid haemorrhage

To determine the incidence of induced systemic hypotension in patients after aneurysmal subarachnoid haemorrhage (SAH) and nimodipine treatment 87 consecutive cases were reviewed. The patients were managed according to the same Nimodipine treatment protocol. After confirmation of SAH the nimodipine treatment was started as a continuous intravenous perfusion at a dosage of 0.5 mg/h and gradually increased every 6 hours if haemodynamically tolerated until the maintenance dose of 2 mg/h was reached. Median systemic pressure was continuously measured and tolerated until a lowest limit of 75 mmHg. In 31 patients (36%) hypotension with values below 75 mmHg during at least 30 minutes was noted and needed Nimodipine reduction. Intravenous Nimodipine administration was responsible for hypotension in 26 cases as compared to 5 cases due to oral administration. 38% of all patients required support by vaso-active agents (Dopamine or Nor-adrenaline). There was no statistically significant difference of incidence of delayed ischaemic deterioration comparing the Nimodipine-reduction group with the normal dose group. This study demonstrates that a considerable risk exists of Nimodipine induced hypotension in intravenous administration despite gradually increasing the doses. Correction of hypotension through further induced hypervolaemia accompanied by vasoactive agents can lead to critical haemodynamic situations. We therefore recommend oral Nimodipine administration.

Attenuation of ischemic and postischemic damage to brain metabolism and circulation by a novel Ca2+ channel antagonist, NC-1100, in spontaneously hypertensive rats

We investigated the effect of a newly synthesized Ca2+ channel antagonist, NC-1100, on cerebral blood flow (CBF) and metabolism in spontaneously hypertensive rats. The rats received a bolus injection of 0.2 or 1.0 mg/kg NC-1100 i.v. and 1-h cerebral ischemia was then induced by bilateral carotid artery occlusion (group 1). The rats in group 2 were continuously infused with NC-1100 0.03 or 0.1 mg/kg per min, starting immediately after bilateral carotid artery occlusion, for the 1 h of ischemia and following 3-h recirculation. Group 1: during ischemia, CBF in all rats decreased to 6-8% of the resting values. At 1 h cerebral ischemia, brain tissue lactate increased 11.5-, 10.1- and 9.8-fold of the normal control given vehicle or NC-1100, 0.2 and 1.0 mg/kg, respectively. The ATP levels were better preserved by NC-1100 administration; 0.61 +/- 0.04 (mean +/- S.E.M.), 0.80 +/- 0.09 and 0.97 +/- 0.14 mmol/kg (P < 0.05 vs. vehicle), respectively. Group 2: during recirculation, CBF in NC-1100-treated rats returned to 83-90% of the resting values, but to only 65% in the vehicle group. Postischemic brain lactate at 3 h was less well preserved and ATP was dose dependently better preserved in NC-1100- than vehicle-treated rats. It is considered that pre- as well as postischemic administration of a Ca2+ channel antagonist, NC-1100, is beneficial to attenuate and also ameliorate the metabolic and circulatory derangement in the ischemic brain.