Possible role of calcium blockers in cerebral resuscitation: a review of the literature and synthesis for future studies

The influence of nicardipine and ifenprodil on the brain free arachidonic acid level and behavior in hypoxia-exposed rats

1. The effects of the calcium channel blockers, nicardipine and ifenprodil, on the brain free arachidonic acid level and learning ability in rats exposed to hypoxia were examined. 2. Adult rats were injected with 0.003; 0.01; 0.03; 0.1; 0.3 or 1.0 mg/kg of tested drugs i.p. Thirty min later the learning ability was tested in a passive avoidance task according to the step-through procedure. Immediately after the training trial, the animals were subjected to a period of oxygen deprivation hypoxia until the loss of the righting reflex. The retention trial was carried out 24 hr later. 3. The other groups of animals were pretreated with mentioned substances before hypoxia-exposure. Fifteen min after the loss of the righting reflex they were decapitated and brains were frozen in liquid nitrogen. The brain free arachidonic acid level was quantified by gas chromatography. 4. Both nicardipine and ifenprodil were effective in preventing a memory decline in hypoxia-exposed rats but did not prevent the accumulation of the brain free arachidonic acid in hypoxia-exposed rats. 5. The protective effects of both substances in behavioral studies during acute brain damage caused by hypoxia could not be explained by the prevention of the increase of the brain free arachidonic acid, but by some other mechanism.

Active compression-decompression CPR improves vital organ perfusion in a dog model of ventricular fibrillation

OBJECTIVES

This study was designed to assess whether a new method of cardiopulmonary resuscitation (CPR), termed active compression-decompression CPR, or ACD-CPR, improves organ perfusion when compared with standard (S) CPR in a dog model of ventricular fibrillation.

BACKGROUND

ACD-CPR has recently been shown to improve hemodynamic and respiratory parameters during cardiac arrest when compared with standard CPR. However, to our knowledge, the effects of ACD-CPR on tissue perfusion have not been investigated.

METHODS

Ventricular fibrillation was induced in eight anesthetized, intubated animals. ACD-CPR and standard CPR were each performed twice in alternating order. All interventions were preceded by 1 min of ventricular fibrillation, in which no CPR was performed, and consisted of 6 min of CPR with either technique during which tissue perfusion was measured. Compressions were performed at 80/min with a 50 percent duty cycle and 175 to 200 N downward force applied to the chest wall for both techniques. Epinephrine was administered at the beginning of each 6-min CPR interval. Hemodynamic monitoring of aortic and right atrial pressure was performed continuously and myocardial, cerebral, and renal blood flows were measured using the radiolabeled microsphere technique at baseline and during all interventions.

RESULTS

Baseline organ perfusion and hemodynamics were similar for all dogs. Baseline left ventricular, brain, and renal blood flows were 62.0 +/- 5.5, 14.1 +/- 2.1, and 476.3 +/- 55.5 ml/min/100 g, respectively (mean +/- SEM). Compared with standard CPR, ACD-CPR resulted in higher global left ventricular (22.5 +/- 6.2 vs 14.1 +/- 4.0 ml/min/100 g, p < 0.01), cerebral (12.0 +/- 2.4 vs 8.5 +/- 2.3 ml/min/100 g, p < 0.01), and renal cortical (27.8 +/- 5.0 vs 17.5 +/- 5.0 ml/min/100 g, p < 0.05) blood flows. Regional flows to the epicardium, endocardium, and midmyocardium as well as to the frontal, parietal, and occipital lobes of the brain were all significantly improved by ACD-CPR. Aortic systolic (61.7 +/- 4.1 vs 49.5 +/- 3.1 mm Hg, p < 0.01), aortic mean (31.6 +/- 2.8 vs 27.2 +/- 2.2 mm Hg, p = 0.001), and myocardial perfusion pressure (12.9 +/- 3.4 vs 10.4 +/- 3.4 mm Hg, ACD-CPR vs standard CPR, p < 0.01) were all higher during ACD-CPR than during standard CPR.

CONCLUSIONS

We conclude that ACD-CPR improves tissue perfusion and systemic hemodynamics compared with standard CPR.

Dihydropyridine ligand binding decreases earlier in adolescent than in infant swine after global cerebral ischemia

BACKGROUND AND PURPOSE

Voltage-dependent calcium channels (VDCCs) are thought to play a major role in the alteration of calcium homeostasis during ischemia. Tissue functional state as well as responsiveness to therapy with calcium channel blockers may be a function of regional changes in the density of VDCCs. This study determined whether VDCCs are altered by global ischemia in infant and adolescent swine.

METHODS

We employed the radioligand 3HPN200-110 to quantify the binding characteristics of VDCCs in cerebral cortex, caudate, and hippocampus by equilibrium binding analysis. Adolescent and infant pigs underwent 3, 5, 10, and 20 minutes of global cerebral ischemia without reperfusion by ligation of the brachiocephalic and left subclavian arteries combined with hypotension to a mean arterial blood pressure of 50 mm Hg. Brain cortex, hippocampus, and caudate samples were taken during ischemia and frozen immediately in liquid nitrogen, and crude synaptosomal membranes were isolated by differential centrifugation/filtration. 3HPN200-110 equilibrium binding assays were performed in the presence or absence of 1.0 mumol/L unlabeled nitrendipine to determine total and nonspecific binding.

RESULTS

Infant cortex maximal binding (Bmax) increased to 176% of control after 5 minutes of global cerebral ischemia and remained significantly elevated (172% of control) after 10 minutes before falling to near control levels by 20 minutes. Adolescent cortex Bmax increased to 157% of control levels after 5 minutes but did not remain elevated, falling to 131% of control by 10 minutes and near control by 20 minutes. Infant caudate and hippocampus binding were significantly elevated after 10 (124% and 149% of control, respectively) and 20 (115% and 120% of control, respectively) minutes of ischemia. Adolescent caudate and hippocampus binding was either not significantly different from control levels (hippocampus at 10 minutes) or less than control after 10 and 20 minutes of global cerebral ischemia. The decrease in binding following the initial upregulation, which appeared earlier in the adolescent than the infant pigs, may indicate decreased tolerance to ischemia in the adolescent.

CONCLUSIONS

The binding of 3HPN200-110 in brain is altered during 20 minutes of global cerebral ischemia, and these changes are region- and age-dependent.

Autoradiographic analysis of L- and N-type voltage-dependent calcium channel binding in canine brain after global cerebral ischemia/reperfusion

Binding of antagonists to L- and N-type voltage-dependent calcium channels (VDCC) was measured in canine brain following global ischemia and reperfusion. Ischemia was induced by 10 min cardiac arrest, followed by restoration of spontaneous circulation for periods of up to 24 h. Binding of [3H]PN200-110 and [125I]omega-conotoxin GVIA to frozen sections from hippocampus, striatum, parietal cortex and temporal cortex was analyzed using quantitative receptor autoradiography. The binding patterns of the two radioligands were similar in cortex and striatum, but differed in hippocampus. In the latter tissue, [125I]omega-conotoxin GVIA binding was dense over synaptic regions, especially the presynaptic polymorph layer of the dentate gyrus, but was virtually absent over cell body layers. In contrast, [3H]PN200-110 binding was more homogenously distributed, with highest binding in the molecular layer of the dentate gyrus. The binding of [125I]omega-conotoxin GVIA was not different from sham controls at any time point following cardiac arrest. [3H]PN200-110 binding was decreased in each region immediately following ischemia, recovering within 30 min of recirculation. These findings are in contrast to earlier findings of rapid increases in L-type VDCC binding to membrane fractions obtained from cortex and striatum in this model, and suggest that the previously detected increases may be due to a redistribution of channels from subcellular compartments to the plasma membrane during ischemia.

Cerebral resuscitation after cardiac arrest: research initiatives and future directions

At present, fewer than 10% of cardiopulmonary resuscitation (CPR) attempts prehospital or in hospitals outside special care units result in survival without brain damage. Minimizing response times and optimizing CPR performance would improve results. A breakthrough, however, can be expected to occur only when cerebral resuscitation research has achieved consistent conscious survival after normothermic cardiac arrest (no flow) times of not only five minutes but up to ten minutes. Most cerebral neurons and cardiac myocytes tolerate normothermic ischemic anoxia of up to 20 minutes. Particularly vulnerable neurons die, in part, because of the complex secondary post-reflow derangements in vital organs (the postresuscitation syndrome) which can be mitigated. Brain-orientation of CPR led to the cardiopulmonary-cerebral resuscitation (CPCR) system of basic, advanced, and prolonged life support. In large animal models with cardiac arrest of 10 to 15 minutes, external CPR, life support of at least three days, and outcome evaluation, the numbers of conscious survivors (although not with normal brain histology) have been increased with more effective reperfusion by open-chest CPR or emergency cardiopulmonary bypass, an early hypertensive bout, early post-arrest calcium entry blocker therapy, or mild cerebral hypothermia (34 C) immediately following cardiac arrest. More than ten drug treatments evaluated have not reproducibly mitigated brain damage in such animal models. Controlled clinical trials of novel CPCR treatments reveal feasibility and side effects but, in the absence of a breakthrough effect, may not discriminate between a treatment's ability to mitigate brain damage in selected cases and the absence of any treatment effect. More intensified, coordinated, multicenter cerebral resuscitation research is justified.

Alteration of voltage-dependent calcium channels in canine brain during global ischemia and reperfusion

Elevated intracellular calcium (iCa2+) plays an important role in the pathophysiology of ischemic brain damage. The mechanisms by which iCa2+ increases are uncertain. Recent evidence implicates the voltage-dependent calcium channel (VDCC) as a likely site for the alteration in Ca2+ homeostasis during ischemia. The purpose of this study was to determine whether VDCCs are altered by global ischemia and reperfusion in a canine cardiac arrest, resuscitation model. We employed the radioligand, [3H]PN200-110, to quantitate the equilibrium binding characteristics of the VDCCs in the cerebral cortex. Twenty-five adult beagles were separated into four experimental groups: (a) nonischemic controls, (b) those undergoing 10-min ventricular fibrillation and apnea, (c) those undergoing 10-min ventricular fibrillation and apnea followed by spontaneous circulation and controlled respiration for 2 and (d) 24 h. Brain cortex samples were taken prior to killing of the animal, frozen immediately in liquid nitrogen, and crude synaptosomal membranes isolated by differential centrifugation/filtration. After 10 min of ischemia the maximal binding (Bmax) of [3H]PN200-110 increased to greater than 250% of control values (control Bmax 11.16 +/- 0.98; ischemic 28.35 +/- 2.78 fmol/mg protein; p less than 0.05). Bmax returned to near control values after 2 h of reperfusion but remained significantly greater than the control at 24 h. Although the affinity constant (Kd) (control = 0.12 +/- 0.03 nM) appeared to increase with ischemia and normalize with reperfusion, the changes were not statistically significant. We conclude that the binding of [3H]PN200-110 to L-type VDCCs is increased after 10 min of global ischemia/anoxia produced by ventricular fibrillation and apnea in the dog.(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized clinical trial of calcium entry blocker administration to comatose survivors of cardiac arrest. Design, methods, and patient characteristics. The Brain Resuscitation Clinical Trial II Study Group

The Brain Resuscitation Clinical Trial (BRCT) II was a double-masked, randomized, controlled clinical study of cardiopulmonary-cerebral resuscitation (CPCR) designed to test therapy for the amelioration of brain damage after cardiac arrest. Lidoflazine, a calcium entry blocker, was chosen for investigation because of its beneficial effects on postischemic encephalopathy in animals, its minimal cardiovascular depressant effects, and its protective actions in myocardial ischemia in patients. Twenty-four hospitals in eight countries participated. Over 4 years, 520 patients were recruited, of whom 4 were subsequently lost to follow-up. Patients' age averaged 63 years and 62% were men. Cardiac arrest occurred prior to hospitalization in 63%. All patients received basic and advanced life support until circulation was restored, and then standardized extracerebral organ support. After restoration of spontaneous circulation with normal blood pressure, patients who failed to awaken were randomly assigned to receive IV administration of either lidoflazine or placebo. In each patient, outcome was evaluated by cerebral performance during a 6-month follow-up period. Periodic safety monitoring was carried out to assure that no excess of mortality or complications occurred in the lidoflazine-treated group compared with the placebo-treated group.

Prognostic significance of early intracranial and cerebral perfusion pressures in post-cardiac arrest anoxic coma

The prognosis of prolonged cardiac arrests is generally related to brain damage due to the cerebral anoxia. A neurological worsening leading to irreversibility is sometimes associated with an increase in intracranial pressure. We studied for 5 years the early intracranial and cerebral perfusion pressures in 84 patients with deep anoxic coma after cardiac arrest. Intracranial pressure monitoring was set up as soon as possible with an extradural screw over a period of 6 days. No complications occurred using this technique. We recorded the percentage of patients suffering from intracranial pressure peaks over 15 mmHg (a), over 25 mmHg (b) or cerebral perfusion pressures drops under 50 mmHg (c). We obtained during the 1st day of monitoring: (a) 46.4%, (b) 21.4%, (c) 39%; during the 2nd day: (a) 73.6%, (b) 26.3%, (c) 55.9%. Eight patients (9.5%) were still alive after a couple of months, 4 of whom had no neurological sequelae; among the 76 non-survivors 63 (82.9%) had died because of cerebral anoxic damage. A daily comparison between survivors and non-survivors points out that the survivors' intracranial pressures were always lower than in the non-survivors and the survivors' cerebral perfusion pressures higher than in the non-survivors. Moreover, none of the patients showing intracranial peak pressures over 25 mmHg survived without after-effects. It is clear that many patients suffer early periods of high intracranial pressures and low cerebral perfusion pressures leading to a bad neurological prognosis. Intracranial pressure monitoring may allow assessment of patients' neurological status and prognosis after cardiac resuscitation.

Nimodipine decreases resuscitability in a cardiopulmonary arrest model in the rat

Although calcium has been implicated in ischemia-induced brain death or dysfunction, many animal studies do not show a beneficial effect of calcium-entry blockers given after resuscitation from a cardiopulmonary arrest (CPA). This may be due to the fact that treatment was started too late; we, therefore, evaluated the effect of the calcium-entry blocker nimodipine administered at the earliest feasible postischemic moment, i.e. at the start of the resuscitation attempts. In anesthetized Wistar rats, CPA was induced by an intra-cardiac injection of KCl, and maintained for 7 min by chest restriction. At the start of the resuscitation attempts, 50 rats were blindly and randomly assigned to intravenous treatment with either nimodipine (10 micrograms/kg over 2 min, followed by 1 micrograms/kg per min for 60 min; n = 25) or saline (n = 25). In the nimodipine group, significantly less rats could be resuscitated (11/25 versus 20/25) and the survival rate at the end of the 7 days evaluation period tended to be lower (5/25 versus 11/25). In the rats surviving after 7 days, there was no difference between both groups in incidence of seizures, neurological status and histological lesions in the hippocampus. It is concluded that nimodipine, in the dose tested and given during resuscitation in this rat model, has a detrimental effect on resuscitability and no beneficial effect on the neurological outcome in the surviving animals.

Risk monitoring of randomized trials in emergency medicine: experience of the Brain Resuscitation Clinical Trial II

Risk monitoring for the Brain Resuscitation Clinical Trial II, a multicenter, placebo-controlled trial to evaluate the efficacy of the calcium-entry blocker lidoflazine in the amelioration of brain damage in comatose cardiac-arrest survivors, posed unexpected challenges. Concern arose when monitoring of adverse reactions showed an excess of dangerous cardiac arrhythmias, including rearrest, in the lidoflazine group. To ascertain the cause of this problem and determine whether it was ethical for the trial to continue, an in-depth review of data was conducted, outside experts were consulted, and additional data were collected. These efforts suggested possible causes for the problem. Existing drug administration protocols for blood pressure control were reinforced, resulting in lower subsequent arrhythmia rates. Thus, through an efficient monitoring system, an important problem was uncovered and resolved, allowing the trial to be completed without major changes.

Global cerebral ischemia and subsequent selective hypothermia. A neuropathological and morphometrical study on ischemic neuronal damage in cat

A new method of external selective brain cooling is described, showing its effectiveness in reducing neuronal damage following global cerebral ischemia in cat. The cooling apparatus consists of a specially fitted kind of water jacket in which the animal's head was laid. In a preliminary study it was verified that the device effectively reduces brain temperature without the risk of cardiac arrhythmias due to lowering of core temperature. In the main study cardiac arrest was induced in 23 adult cats, followed after 15 min by cardiopulmonary resuscitation (CPR). Eight cats could not be revived; of the 15 remaining animals, 7 were assigned to the control group (normothermia) and 8 to the treatment group (cerebral hypothermia). The latter received external brain cooling for 30 min, starting as soon as CPR was begun. Four hours after cardiac arrest all animals were transcardiacally perfused with glutardialdehyde. The brains were stored in fixative and subsequently processed for histopathological and morphometrical evaluation by light microscopy. Analysis of the resulting data showed that animals in the treatment group had a significantly higher percentage of undamaged neurons than animals in the control group, both in the cingulate gyrus (38% vs 10%) and in the parietal cortex (39% vs 14%). The treatment group also had more undamaged neurons in the hippocampus and fewer severely damaged neurons in all three regions, but these differences, though suggestive, were not statistically significant.

Early effects of nimodipine on intracranial and cerebral perfusion pressures in cerebral anoxia after out-of-hospital cardiac arrest

Some calcium entry blockers seem to improve the neurological survival of anoxic comas. The early monitoring of intracranial pressure shows the frequency of intracranial hypertension. A calcium channel blocker has been shown to increase the cerebral blood flow which can potentially lead to deleterious increases of the intracranial pressure. This study presents 39 out-of-hospital cardiac arrests resuscitated with success. The intracranial pressures were registered by means of an extra dural screw set up as soon as possible. Nineteen patients received an early continuous 5 days nimodipine treatment (0.58 gamma/kg weight/min. after a 12.3 gamma/kg weight bolus). The other 20 patients did not receive any calcium entry blocker. The two groups were similar in terms of age, origin and electrical type of cardiac arrest, duration of cardiac arrest before BLS and before ACLS, principles of the treatment, initial neurological status and biological values. The maximum and mean intracranial pressures of the nimodipine group were always lower than the intracranial pressure of the control group. The cerebral perfusion pressure was never significantly different in both groups. If the nimodipine treatment proves to be efficient on neurological survival, it would be all the more interesting because it seems to limit the intracranial hypertension phenomenon which aggravates the neurological prognosis.

The effects of nicardipine given after 10-minutes complete global cerebral ischemia on neurologic recovery in dogs

The effect of nicardipine (NC) on neurologic recovery from ischemic insult after 10-minutes complete global cerebral ischemia was evaluated in dogs by examination of neurologic recovery score (NRS: complete recovery = 100, death = 0). Ischemia was achieved by occlusion of ascending aorta, and NC, 10 microg.kg(-1) in bolus followed by infusion of 0.33 microg.kg(-1).min(-1) for 2 hours, was administered immediately after re-establishment of circulation. The mortality at 7th day was 2/9 in the control Copyright and 1/9 in the NC group (ns). NRS on 2nd day was 52.3 +/- 6.8 in the C and 70.6 +/- 6.5 in the NC ( P < 0.05), but that on 7th day did not differ between the two groups. The numbers of dogs recovered to over 80 in NRS on the 2nd day was 1/9 in the C and 5/9 in the NC ( P < 0.05), but that on the 7th day increased to 3/9 in the C and remained at 5/9 in the NC (ns). These results suggest that NC accelerates the early neurologic recovery from ischemic damage, but influences little the final outcome.

The clinical rationale of cardiac resuscitation

After failure of external defibrillation, return of cardiac activity with spontaneous circulation is contingent on rapid and effective reversal of myocardial ischemia. Closed-chest cardiopulmonary resuscitation (CPR) evolved about 30 years ago and was almost universally implemented by both professional providers and lay bystanders because of its technical simplicity and noninvasiveness. However, there is growing concern since the limited hemodynamic efficacy of precordial compression accounts for a disappointingly low success rate; especially so if there is a delay of more than 3 minutes before resuscitation is started. There is also increasing concern with the lack of objective hemodynamic measurements currently available for the assessment and quantitation of the effectiveness of resuscitation efforts. Accordingly, the resuscitation procedure proceeds without confirmation that it increases systemic and myocardial blood flows to levels that would be likely to restore spontaneous circulation. Continuous monitoring of end-tidal carbon dioxide (PETCO2) now appears to be a practical measurement which provides a noninvasive quantitative indication of both systemic blood flow and coronary perfusion pressure. Consequently, PETCO2 predicts the likelihood of successful resuscitation and guides the operator who may modify the technique of precordial compression to improve systemic and myocardial perfusion. Among the large polypharmacy for cardiac resuscitation, only alpha-adrenergic agents (which increase coronary perfusion pressure) and especially epinephrine are of proven benefit. Neither buffer agents nor calcium salts appear to improve outcome except under unique conditions. To the contrary, there is increasing awareness of adverse effects of pharmacologic interventions such that they may hinder the return of viable myocardial and cerebral function. This has constrained the routine use of all drugs except for the use of alpha-adrenergic agonists. More invasive interventions by which blood flow is restored such as open-chest cardiac massage or extra-corporeal pump oxygenation (ECPO) are consistently more effective than conventional CPR. Experimentally, both methods promptly restore systemic and myocardial perfusion to viable levels and thereby increase the likelihood that spontaneous circulation is restored even after prolonged cardiac arrest or failure of conventional CPR.

The use of a calcium-channel blocker, nicardipine, for severely asphyxiated newborn infants

A continuous infusion of nicardipine was given to four severely asphyxiated fullterm infants who were at high risk for adverse outcome and had abnormal cerebral Doppler haemodynamic studies. The heart rate increased in all four infants and mean arterial blood pressure (MAP) fell in three. Two infants had a sudden and marked fall in MAP, together with severe impairment of skin blood-flow and a concurrent fall in cerebral blood-flow velocity. The serum level of nicardipine was less than 40ng/mL in all cases. The use of nicardipine, and possibly other calcium-channel blockers, may be associated with marked hypotension, and if there is no cerebral autoregulation, may cause further cerebral hypoperfusion, so use of these drugs in asphyxiated newborn infants should only be attempted if blood pressure is carefully monitored.

Clinical neuropharmacology of calcium antagonists

Experimental and clinical data clearly demonstrate that calcium antagonists (CA) may have an action on the central nervous system (CNS). The cerebrovascular action of CA justifies their use in cerebral ischaemia, vasospasm and hypoxia. Several clinical trials have demonstrated such beneficial effects. On the other hand a number of reports indicate that CA may have a direct neuronal effect, although most of such trials have not been verified or are mere case reports. In addition, the large number of conditions susceptible to being corrected by CA is impressive: epilepsy, pain, dystonia, dyskinesia, psychiatric conditions, etc. Other papers are disconcerting that report extrapyramidal disorders induced by flunarizine and cinnarizine in the elderly, whereas nicardipine does not produce such side effects and may even alleviate some parkinsonian symptoms. In various experimental models (e.g. stroke, oedema), pharmacological effects have been shown to vary from one compound to the other. Two main questions are yet to be answered: 1) has the direct neuronal effect of CA been clearly established? 2) are the multiple clinical effects on the CNS really linked to calcium antagonism?

In vitro modulation of human neutrophil superoxide anion generation by various calcium channel antagonists used in ischemia-reperfusion resuscitation

Generation of toxic oxygen species by activated polymorphonuclear leukocytes (PMNs) may represent an important mechanism of ischemia-reperfusion injury. Concentration-response data concerning inhibition of superoxide anion (O2-) generation by NADPH oxidoreductase (NADPH OR) from isolated human PMN were generated for five calcium channel antagonists commonly utilized in ischemia-reperfusion investigational therapeutics. Regression analysis derived IC50 values for verapamil, nimodipine, nicardipine and lidoflazine were 45, 20, 12 and 7 microM respectively. Inhibition of the extent of reaction at 5 min paralleled inhibition of initial velocity. No inhibition by flunarizine was noted at concentrations less than or equal to 25 microM (where it did not alter reaction mixture composition). Only nicardipine demonstrated a significant concentration-response effect relative to prolonging lag time preceding O2- synthesis. Inhibition appeared at least partially reversible for all five agents. Neither PMN activation/desensitization, free-radical scavenging, nor PMN cytotoxicity appeared to be involved in the inhibition of PMN O2- synthesis by these agents. Ca2+ antagonist inhibition of PMN NADPH OR appears to involve more than simple inhibition of Ca2+ flux across the PMN plasma membrane. Direct inhibition of the intracellular events involved in the activation and/or activity of NADPH OR may be operative.

Functional, behavioral, and histological changes induced by transient global cerebral ischemia in rats: effects of cinnarizine and flunarizine

Temporary cerebral ischemia (15 min) produced by "four-vessel occlusion" in the rat causes neurological disorders, changes in behavior (locomotor hyperactivity), and neuronal damage in the neocortex, striatum, and especially the CA1 zone of the hippocampus. We have studied the effects of two calcium overload blockers, flunarizine (50 mg/kg p.o. twice a day) and cinnarizine (100 mg/kg p.o. twice a day), on these alterations. Cinnarizine markedly improved the functional abnormalities of ischemia but had little or no effect upon the neuronal damage. In contrast, flunarizine provided far greater neuronal protection but with less obvious effects upon behavioral parameters. However, there was evidence of sedation 2 h after treating animals with this dose of flunarizine that might have masked any positive effect of the drug on behavior. We conclude that under the present experimental conditions, there is no correlation between the early and late behavioral changes observed following a temporary cerebral ischemic episode and the histological damage observed in certain vulnerable neurons, particularly in the hippocampus, 72 h after the insult.

Verapamil treatment of canine hemorrhagic shock

The entry of calcium (Ca++) into ischemic cells is the first of a series of steps leading to irreversible cellular damage. This study examined the ability of verapamil, which may delay or diminish the injury-induced influx of Ca++, to prolong survival in three groups of chronically instrumented dogs subjected to a single, rapid hemorrhage. In untreated animals (group 1, N = 6), hemorrhage decreased mean arterial blood pressure from 101 +/- 3 mm Hg to 23 +/- 2 mm Hg. Following hemorrhage, arterial pressure recovered to 61 +/- 5 mm Hg before the secondary fall (decompensation) occurred. As decompensation progressed, arterial pressure fell to 25 mm Hg, and the animals were euthanized. In group 2 (N = 6), verapamil treatment (2 mg bolus, 1 mg/hr infusion) was initiated 30 minutes before the hemorrhage. This treatment significantly increased both the time to decompensation (184 +/- 15 minutes vs 72 +/- 9 minutes) and survival time (262 +/- 20 minutes vs 128 +/- 8 minutes). Arterial pressure recovery during the first 60 minutes following hemorrhage, however, was not affected by the verapamil pretreatment. Verapamil treatment immediately after the hemorrhage (group 3, N = 4) increased the survival rate to 75% (three of four animals). These results indicate that calcium channel blockade may be a useful initial intervention in the treatment of hemorrhagic shock.

A double-blind, randomized trial of PY108-068 in acute ischemic cerebral infarction

A double-blind, randomized, pilot trial of the calcium channel antagonist PY108-068 was completed in patients with acute ischemic cerebral infarction. Nine treated patients received PY108-068 orally (150 mg/day in divided doses) and 10 control patients received placebo within 48 hours of stroke onset for 21 days. The mean age of the treated patients (four men, five women) was 63.7 years and of the control patients (seven men, three women) 64.4 years. Most infarctions were in the territory of the middle cerebral artery. One treated patient died of sudden cardiac death on Day 12; one control patient died of cerebral herniation. Two treated patients had episodes of clinically insignificant hypotension during Day 1 of treatment. Two control patients had myocardial infarctions during the trial. The mean Toronto Stroke Scale scores at stroke onset were 67 and 90 and at Week 12 were 22.5 and 34.7 in the treated and control groups, respectively. There was parallel improvement in the two groups, with no significant difference between groups (p = 0.12). The mean Barthel Index functional scores at stroke onset were 32.8 and 33 and at Week 12 were 90 and 78.8 in the treated and control groups, respectively. There was a trend in favor of the treated group, but differences between groups did not reach significance. In this pilot trial, PY108-068 was found to be safe but not effective in patients with acute ischemic cerebral infarction.

Out-of-hospital cardiac arrest: the teaching of experience at the SAMU of Lyon

Because of the improvement resuscitation techniques have shown since the 1960s and because of the development of the out-of-hospital medical care, a cardiac arrest is no longer synonymous with death in every case. However the cardiac arrest resuscitation is only relevant if its adverse consequences can be limited. That is mainly the neurological after-effects and the cellular anoxia. Therefore, the "Service d'Aide Medicale Urgente" (SAMU) of Lyon has been concentrating its research aiming at: (a) Shortening the duration of cardiopulmonary resuscitation to limit the cerebral anoxia. (b) Analysing and treating some of the causes responsible for the aggravation of anoxia. On the basis of several studies in Lyon, here are some suggestions: (1) The use of high doses of epinephrine that unables a better percentage of primary recoveries (47.5% vs. 39%) (P less than 0.05) and secondary recoveries (21.3% vs. 14.8%) (P less than 0.01) without modifying the qualitative survival at long term. (On the basis of: 5 mg intravenous bolus repeated every 3 min in case of asystole instead of 1 mg every 5 min as it is usually recommended). (2) The choice of a peripheral intravenous line instead of a central intravenous line each time it is possible for the administration of drugs since it is as efficient as the second one. (40.7% vs. 33.4%) (P:NS). (3) The alkalinisation of the prolonged cardiac arrest in order to keep the acid-base balance. Most of the survivors show a pH equal or superior to the normal standard. (On the basis of 1 mmol/kg of sodium bicarbonate if the cardiac arrest lasts for more than 10 min). (4) The abolition of the dextrose solution as maintaining infusion the patients who are in a "coma depasse" (brain death) after the resuscitation have an average glycemia superior to the survivors without after-effects. (19.7 vs. 14.8 mmol/l) (P less than 0.05). (5) The monitoring at once at the hospital of the intra-cranial pressure. It reveals the frequency of high pression at an early stage (superior to 15 mmHg in 51.1% of the cases) and the absence of favourable evolution in case of high intracranial pressure. At the moment the absence of consequences on the ICR of a calcium entry blocker (Nimodipine) is being studied. The first results do not seem to show any improvement of the cerebral survival. (6) The prophylactic treatment of septicemia with intestinal origin since they occur frequently and prove to be fatal.

Bacteremia following cardiac arrest and cardiopulmonary resuscitation

After out of hospital CPR thirty three resuscitated patients were studied for bacteremic complications. Thirteen patients (39%) had two or more positive blood cultures during the twelve hours following CPR. Source of superinfection was a central venous catheter in one case (staphylococcus). The twelve other bacteremic patients had fetid diarrhea a few hours after admission. The same organism were found in blood and faeces (streptococcus D, Escherichia coli, Pseudomonas aeruginosa, acinetobacter, enterobacter). Mesenteric ischemia caused by a low cardiac output may explain the diarrhea and the intestinal origin of the septicemia. All patients (12 cases) with diarrhoea and bacteremia died. Patients who recovered without neurologic sequelae (4 cases) had never been septic and never had diarrhea.

A controlled trial of nimodipine in acute ischemic stroke

Recent investigations suggest that increased cellular calcium concentrations may be implicated in neuronal death after ischemia. To determine whether treatment with a calcium-channel blocker would improve survival and neurologic outcome in acute ischemic stroke, we enrolled 186 patients in a prospective, double-blind, randomized, placebo-controlled trial of nimodipine (30 mg every six hours), begun within 24 hours of the onset of symptoms of an acute ischemic stroke. During the four-week treatment period, mortality from all causes was significantly reduced with nimodipine as compared with placebo (8 deaths [8.6 percent] vs. 19 [20.4 percent]). The improvement in survival was restricted to men. During the follow-up period of six months, an additional eight patients in each group died. A significantly better neurologic outcome, as assessed by the Mathew scale of neurologic deficit, was also observed in the nimodipine group. The improvement in neurologic status was greatest in patients with a moderate to severe deficit at base line. There were no important side effects except for one episode of reversible azotemia that may have been related to treatment with nimodipine. Our data suggest that patients with acute ischemic stroke may benefit from early treatment with nimodipine, but this therapeutic effect appears to be limited to men.

Peroxidation of brain lipids following cyanide intoxication in mice

Lipid peroxidation of brain lipids as determined by the conjugated diene method was observed in mice following administration of sublethal doses of potassium cyanide (KCN). Conjugated diene production was dose- and time-dependent; 10 mg/kg KCN produced detectable levels of conjugated dienes at 30 min post cyanide, whereas, 15 mg/kg produced marked levels of conjugated dienes over a 10-60-min period after KCN. Pretreatment of mice with either diltiazem (600 micrograms/kg, i.v.) or allopurinol (25 mg/kg, i.v.) blocked the generation of conjugated dienes. These results suggest lipid peroxidation of neuronal membranes play a role in cyanide intoxication and this action is related to altered regulation of neuronal calcium homeostasis and activation of xanthine oxidase.

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.

Prevention of "irreversible" hemorrhagic shock by the preservation of cellular integrity

The clinically encountered state of hypovolemic shock results from a series of metabolic and cardiovascular responses to tissue hypoperfusion. Recent advances have increased our understanding of the consequences of tissue hypoxia, and identified at the cellular level those changes which cause the damage to be "irreversible", or refractory to treatment. To be successful, therapeutic interventions should be designed to 1) limit, if not reverse, the subcellular alterations in membrane stability and mitochondrial function which herald the transition from compensated to decompensated shock, and 2) re-hydrate the individual to restore normal circulatory dynamics and to prevent further cellular damage. It is proposed that calcium channel blocking agents and/or high energy phosphate compounds may delay the positive feedbacks which cause irreversible tissue damage, and thus may be useful initial interventions in the treatment of hypovolemic shock.

Regional brain calcium changes in the rat middle cerebral artery occlusion model of ischemia

Entry of Ca ions into ischemic neurons is believed to cause cell damage. Although several investigators have demonstrated changes in extracellular Ca ionic activity consistent with Ca movement into cells, direct and quantitative evidence for Ca entry into ischemic cells is lacking. We used atomic absorption spectroscopy to measure the regional distribution of tissue Ca contents of rat brains sampled at 2, 4, and 24 hours after middle cerebral artery occlusion (MCAo). At 4 hours after MCAo, Ca concentrations increased significantly (p less than 0.005) in the ischemic middle cerebral artery territory, i.e., the pyriform and frontoparietal cortices, but not in the surrounding brain. At 24 hours, Ca concentrations in the pyriform and frontoparietal cortex were respectively 30.79 (+/- 2.90) and 29.19 (+/- 3.28) mumol/g dry tissue wt compared with 11.9 (+/- 1.7) mumol/g in sham-occluded rats. Tissue Ca concentration changes in the parasagittal cortex and basal ganglia adjacent to the infarct site were much smaller and did not differ significantly from controls until 24 hours. In the ischemic middle cerebral artery territory, greater than 1.0 mumoles of Ca entered per gram of dry tissue weight per hour during the first 4 hours after MCAo. Linear regression analysis revealed a significant correlation (r = 0.9722) between changes in tissue Ca and water, with a slope indicating that 5.88 mumoles of Ca accompanied each milliliter of water entering the lesioned hemisphere. Such massive accumulations of Ca not only confirm Ca entry into injured cells, but indicate the presence of a remarkable Ca sink which sequestered within 24 hours more than 17 times the amount of free Ca present in the tissue before MCAo.

Calcium channel antagonists decrease the ethanol withdrawal syndrome

Withdrawal from chronic ethanol intake results in a syndrome of tremor and hyperexcitability, which can progress to seizures and death. Drugs used therapeutically to alleviate the syndrome have sedative actions and dependence liability of their own. The basis of the syndrome is unclear, although ethanol affects many neuronal functions, including membrane calcium conductance. Calcium channel blocking drugs have been used in cardiovascular disorders; they bind to high affinity sites in the brain but have few overt actions on the central nervous system. We have tested the effects of four calcium channel antagonists on the ethanol withdrawal syndrome in rats. Nitrendipine and nimodipine abolished all spontaneous seizures and prevented or reduced seizures following an audiogenic stimulus, and mortality. Verapamil significantly decreased seizure incidence and both it and flunarizine lowered mortality. The dihydropyridines were considerably more effective than diazepam in the withdrawal syndrome but had little effect on pentylenetetrazol seizures, against which diazepam gave good protection. The calcium channel inhibitors showed no sedative activity in normal animals. The results provide evidence that alterations in calcium conductance may be involved in the ethanol withdrawal syndrome and offer possibilities for the development of non-sedative therapeutic treatment of this syndrome.

Nicardipine increases cerebral blood flow but does not improve neurologic recovery in a canine model of complete cerebral ischemia

The effects of the calcium entry blocker nicardipine on CBF, CMRO2, and neurologic outcome following 10 min of complete cerebral ischemia were examined in dogs. In CBF and CMRO2 studies, the CBF in the untreated group (seven dogs) and the nicardipine group (seven dogs; 20 micrograms kg-1 at 30 min postischemia and a subsequent infusion of 2 micrograms kg-1 min-1 for 90 min) initially increased to 300-400% and then returned to preischemic values at 30 min postischemia. Thereafter the CBF in the untreated group significantly decreased to 50% of preischemic values for the following 90-min period (hypoperfusion), while the CBF in the nicardipine group did not differ from preischemic values. The CMRO2 in both groups decreased to approximately 50-80% of preischemic values after 15 min postischemia and did not differ between the groups throughout the study. In neurologic outcome studies, 18 dogs were divided into three groups (of six dogs each): untreated; saline infusion only, posttreated; nicardipine as in CBF and CMRO2 studies, pretreated; nicardipine 20 micrograms kg-1 at 2 min preischemia and a subsequent infusion of 2 micrograms kg-1 min-1 from immediately postischemia to 120 min postischemia. Nicardipine treatment initiated either before or after ischemia failed to improve neurologic outcome at 48 h postischemia. Thus, the increase of postischemic global CBF by nicardipine is not accompanied by neurologic recovery in a canine model of complete cerebral ischemia.

Inhibition of thromboxane A2 production does not improve post-ischemic brain hypoperfusion in the dog

In a canine model of global brain ischemia, six dogs received a selective thromboxane A2 synthetase inhibitor, UK 38,485 (dazmagrel) before the ischemic event; six received a saline placebo. Cerebral blood flow (CBF), systolic and diastolic arterial pressure, cardiac output, pH, PaCO2, PaO2, and arterial and jugular-vein thromboxane B2 (a stable metabolite of thromboxane A2) and 6-keto PGF1 alpha (a stable metabolite of prostacyclin) were measured at baseline, after release of aortic and venae caval occlusion and at intervals up to 120 min thereafter. Treated animals showed nearly complete post-ischemic inhibition of thromboxane B2 production; control animals showed increases in jugular venous thromboxane B2. Arterial and jugular venous levels of 6-keto PGF1 alpha were significantly higher in treated animals at most post-ischemic intervals. CBF in both groups was similar to baseline values at time 0, then declined similarly in both groups by 30 min to approximately equal to 35% of baseline values where it remained thereafter. There were no significant differences in other variables at any interval. We conclude that inhibition of thromboxane A2 production does not alter post-ischemic brain hypoperfusion.

Effects of nimodipine on acute focal cerebral ischemia

Nimodipine is a calcium slow channel blocker with several pharmacologic properties suggesting the potential to favorably modify outcome in focal cerebral ischemia. Thirty adult cats underwent unilateral middle cerebral artery (MCA) occlusion for 4 hours. Seventeen cats were treated with an ipsilateral intracarotid infusion of nimodipine (1 microgram kg-1 min -1) beginning 15 minutes before MCA occlusion and continuing throughout the occlusion period. Eight nimodipine treated cats maintaining MAP greater than 90 mmHg were assigned to a Higher Pressure Nimodipine (HPN) group. The remaining nine treated cats with MAP less than 90 mmHg were assigned to the Lower Pressure Nimodipine (LPN) group. Thirteen cats were untreated, receiving an isovolumetric amount of vehicle through the ipsilateral carotid artery. Local cerebral blood flow (ICBF) was continuously monitored using thermal diffusion probes. The brains, assessed for colloidal carbon perfusion, fluorescein and Evans blue staining, electroencephalographic activity (EEG), and histological changes, revealed no significant differences by any of these methods between the HPN and control animals with the exceptions of: HPN treated cats exhibited a preservation of EEG activity at 15 minutes post-occlusion compared to the untreated cats, and Post-ischemic surface colloidal carbon perfusion was better preserved in the treated cats than in the untreated cats. Mild hypotension, as demonstrated by the LPN group, negated these two positive effects. Prior to MCA occlusion, ICBF was bilaterally significantly increased after nimodipine infusion in the HPN group as compared to vehicle infusion. Intra-arterially infused nimodipine did not reduce infarct size.

Should calcium be used in cardiac arrest?

Calcium salts have been recommended for and used in the treatment of various forms of cardiac arrest for many years. Although calcium plays a major role in excitation-contraction coupling, it can have a deleterious effect in some processes of cellular injury. Clinical trials suggest that calcium salts are not effective in ventricular fibrillation and asystole, but that some patients with electromechanical dissociation may have a favorable hemodynamic response. Because of the potential risks of calcium salts, their use should be limited to specific subsets of patients with cardiac arrest.

Cyanide-induced neurotoxicity: role of neuronal calcium

The effect of cyanide on whole-brain calcium levels was determined in mice administered KCN and correlated with the neurotoxic signs manifested during acute cyanide poisoning. KCN (10mg/kg, sc) significantly increased whole-brain total calcium levels from 48.1 +/- 1.8 to 66.5 +/- 3.9 micrograms/g dry wt within 15 min after administration. The levels remained elevated for 3 hr and returned to control readings after 12 hr. Dose-response studies revealed KCN, at doses of 10-15 mg/kg, produced significant elevations of whole-brain calcium 30 min after administration. No measurable effect was obtained from lower doses which suggested a threshold effect. Pretreatment 15 min before KCN with diltiazem, a calcium channel blocker, prevented the cyanide-induced rise in whole-brain total calcium. Cyanide-induced tremors, which are centrally mediated symptoms of intoxication, were quantified and correlated with the observed changes in whole-brain calcium. Tremors were detected at 10 and 12 mg/kg KCN and peak intensity was observed at 15 min postcyanide. Pretreatment with diltiazem markedly attenuated the cyanide-induced tremors. It appears that a correlation exists between cyanide-induced change in whole-brain calcium and tremors. This study suggests that intraneuronal calcium may play an important role in mediating cyanide neurotoxicity and calcium channel blocking agents may be useful in limiting the severity of the centrally mediated symptoms of acute cyanide intoxication.

Effect of deferoxamine on late deaths following CPR in rats

The iron-chelating agent deferoxamine was studied in an animal model as postresuscitation therapy to prevent late deaths and brain damage following total circulatory arrest and resuscitation. Cardiorespiratory arrest was induced by injection of cold, 1% KCl into the left ventricles of ketamine-anesthetized rats pretreated with succinylcholine, and by discontinuation of positive pressure ventilation. CPR was begun after six minutes, and animals with return of spontaneous circulation were entered into the study. Within five minutes after return of spontaneous circulation, treated animals received deferoxamine (50 mg/kg, IV). At ten days, 16 of 25 (64%) of treated animals had survived without neurologic deficit, compared to nine of 25 (36%) of controls (chi square = 3.92, P less than .05). Chelation of intracellular iron by deferoxamine may have prevented free-radical-mediated reactions that led to late deaths in control animals.

Shock following generalized hypoxic-ischemic injury in previously healthy infants and children

Eighteen previously healthy patients with hypoxic-ischemic shock were observed longitudinally by means of data measured or derived from systemic arterial and pulmonary artery catheters. Shock was characterized by low cardiac index, elevated right and left heart filling pressures, elevated systemic and pulmonary vascular resistances, decreased oxygen consumption, and elevated oxygen extraction indices. Oxygen consumption was significantly correlated with oxygen delivery (r = 0.74, P less than 0.0001). This pattern fits that of cardiogenic shock. Cardiopulmonary data were not significantly different in survivors (n = 10) and nonsurvivors (n = 8). Outcome was determined by neurologic injury.

Endogenous opioids in spinal cord injury: a critical evaluation

Based upon evidence that opioid antagonists improve neurological outcome following either traumatic or ischemic spinal cord injury, endogenous opioids have been implicated in the pathophysiology of these disorders. Naloxone improved both spinal cord perfusion and neurological function following traumatic spinal cord injury in cats, and was subsequently observed to improve neurological outcome following ischemic spinal cord injury in rabbits. Using several opioid antagonists with varied selectivities for different types of opioid receptors, it was suggested that kappa opioid receptors are involved in both these models of spinal cord injury. In addition, spinal cord trauma in rats is associated with increased concentrations of the endogenous kappa agonist dynorphin A, and increased kappa opioid receptor binding capacity localized to the injury site. Furthermore, dynorphin A induces hindlimb and tail flaccidity following intrathecal injection in rats. Thus, the pathophysiological effects of endogenous opioids in spinal cord injury have been proposed to involve dynorphin A interactions with kappa opioid receptors. However, disparities between the actions of intrathecally injected dynorphin A in rats and the presumed actions of endogenous dynorphin A in cat and rabbit spinal cord injury have been revealed in recent experiments. Paralysis resulting from intrathecal dynorphin A is not altered by opioid receptor antagonists or TRH, produced by non-opioid dynorphin A fragments but not by other selective kappa opioid agonists, and associated with non-opioid mediated reductions in spinal cord blood flow. Furthermore, despite reports of endogenous opioid changes following rat spinal cord trauma, in contrast to cats and rabbits, naloxone failed to improve neurological outcome following traumatic rat spinal cord injury. Thus, the specific endogenous opioids and opioid receptor types involved in spinal cord injury remain to be resolved, and do not appear to be universal among different models of spinal cord injury in different species. Additionally, dynorphin A may participate in spinal cord injury mechanisms in the rat through non-opioid actions.

Role of iron ions in the genesis of reperfusion injury following successful cardiopulmonary resuscitation: preliminary data and a biochemical hypothesis

Presented is a rationale for use of a new class of drugs, the iron chelating agents, in advanced cardiac life support (ACLS) to prevent late deaths and brain damage following successful cardiopulmonary resuscitation. The relevant biochemical hypothesis states that free iron ions, liberated from bound intracellular stores during ischemia, catalyze initiation of free radical mediated reactions that propagate through membrane lipids and proteins. Progressive ultrastructural damage may result, ultimately causing deterioration of function and death. Chelation of intracellular iron by deferoxamine, a commercially available drug that distributes to the intracellular space and has a great affinity for iron ions, may prevent such reactions. A hypothesis concerning relevant pathological chemistry is developed in detail.

Special problems in the diagnosis and treatment of surgical sepsis

Since sepsis is the most frequent single cause of death after surgery and trauma, its development should be anticipated in elderly patients or those with disease or trauma causing intestinal leaks, particularly if the patient had massive transfusions or was in shock. Diagnosis may be extremely difficult, particularly if the infection is intraperitoneal. Furthermore, patients with impaired host defenses may show only a failure to thrive and then a progressive MOF. Physical examination is usually not very helpful. Gallium and indium scans and ultrasonography are only about 50 to 60 per cent accurate. Ultrasonography followed by HIDA and PIPIDA scans may be very useful in diagnosing acute acalculous cholecystitis, which appears to be an increasingly frequent problem in these patients. Computerized tomographic scans are at least 80 to 90 per cent accurate in diagnosing intra-abdominal abscesses, but the diagnosis of peritonitis is still largely clinically based. Even without clear evidence of infection, the critically ill patient with MOF and previous abdominal trauma, surgery, or disease should probably have the abdomen explored (that is, a blind laparotomy). If generalized peritonitis is found, it may be wise to leave the abdomen open and re-explore and débride it daily until it is clean. Percutaneous drainage of abdominal abscesses is being performed increasingly and is of special value in the 30 to 50 per cent of patients with single bacterial abscesses in which the drainage tract does not cross bowel or peritoneum and there is no underlying intestinal leak. Antibiotics are only a second line of defense, and their use should be directed by smear and culture results when possible. For abdominal infections, coverage for gram-negative anaerobes and Bacteroides fragilis is essential. If the infection persists for more than 2 to 3 weeks, infection by enterococci and fungi must be considered. If shock develops, maintaining an O2 consumption of at least 130 to 160 ml per minute per m2 is a particularly important part of the resuscitation. Although controversial, raising the hematocrit to 40 to 45 per cent or higher is often of value.