Erik Popp

Cerebral Resuscitation After Cardiocirculatory Arrest

Cardiopulmonary resuscitation can restore spontaneous circulation in up to 50% of patients suffering from cardiac arrest. However, most of these patients still die during the postresuscitation period. Mortality is largely due to neuronal injury after global cerebral ischemia. There is, therefore, a clear need for therapies, which restore and protect brain function after cardiac arrest. Several years ago, mild therapeutic hypothermia was introduced into clinical practice. It represents the first treatment to improve both survival and neurological outcome of patients after out-of-hospital cardiac arrest, according to randomized clinical trials. In addition to therapeutic hypothermia, various other therapeutic options are currently being investigated experimentally and/or clinically. These include thrombolytic therapy, specific infusion regimens, or antiapoptotic drugs. In this article, we review both the pathophysiological background and the efficacy of different measures that might be useful for cerebral resuscitation.

Time course of caspase activation in selectively vulnerable brain areas following global cerebral ischemia due to cardiac arrest in rats

This study evaluated the time course of caspase activation in selectively vulnerable brain areas (hippocampus, nucleus reticularis thalami (NRT), cortex and striatum) following cardiopulmonary resuscitation (CPR) after global cerebral ischemia due to cardiac arrest (CA) in rats. Caspases are well known to play a crucial role in the apoptotic cascade and inflammatory syndromes and, therefore, represent potential therapeutic postischemic targets. Given the delayed neurodegeneration following CA, it is highly important to study the time course of caspase activation in regard to therapeutic interventions after CA. To assess caspase activity, in situ staining was applied to detect general caspase activity at 6h, 3d and 7d and caspase-3 activity at 3d after return of spontaneous circulation (ROSC). For detection of neuronal apoptosis, TUNEL staining was applied at 7d after ROSC. Distinct patterns of early caspase activation were observed at 6h and 3d in the NRT and striatum and of late activation at 7d in the hippocampal CA-1 sector. General caspase and caspase-3 activity correlated strongly at 3d after ROSC in all areas studied. At 7d, the TUNEL-positive neuron counts in the hippocampal CA-1 sector correlated strongly with caspase activation. In conclusion, general caspase and caspase-3 activity after 6 min of CA and the delayed occurrence of TUNEL-positive neurons strongly indicate that neuronal degeneration after CA is at least strongly associated with apoptosis. Therefore, postischemic antiapoptotic interventions might offer potential future therapeutic opportunities global cerebral ischemia due to CA.

Improved resuscitation after cardiac arrest in rats expressing the baculovirus caspase inhibitor protein p35 in central neurons.

Background Global cerebral ischemia is associated with delayed neuronal death. Given the role of caspases in apoptosis, caspase inhibitors may provide neuronal protection after cardiac arrest. To this end, the authors generated a transgenic rat line expressing baculovirus p35, a broad-spectrum caspase inhibitor, in central neurons. Its effects were evaluated on neuronal cell death and outcome after global cerebral ischemia. Methods Global cerebral ischemia was induced by cardiocirculatory arrest. After 6 min, animals were resuscitated by controlled ventilation, extrathoracic cardiac massage, epinephrine, and electrical countershocks. Neuronal death was assessed after 7 days by histologic evaluation of the hippocampal cornu ammonis 1 sector. Postischemic outcome was assessed by determination of overall survival and according to neurologic deficit scores 24 h, 3 days, and 7 days after resuscitation. Results The rate of 7-day survival after cardiac arrest for the transgenic rats (85%) was significantly higher than that for the nontransgenic controls (52%;P < 0.05). However, no differences were observed either in the number of terminal deoxynucleotidyltransferase–mediated d-uracil triphosphate–biotin nick end-labeling–positive cells or viable neurons in the cornu ammonis 1 sector or in the neurologic deficit score when comparing surviving transgenic and nontransgenic rats. These findings suggest that neuronal apoptosis after cardiac arrest is not primarily initiated by activation of caspases. Conclusion Expression of baculovirus p35 can improve survival after cardiac arrest in rats, but the mode and site of action remain to be elucidated.

Altered protein expression levels of Fas/CD95 and Fas ligand in differentially vulnerable brain areas in rats after global cerebral ischemia.

To assess the role of the apoptosis-inducing death receptor Fas/CD95 and Fas Ligand (FasL) after global cerebral ischemia, expression of these proteins was investigated in differentially, i.e. selectively vulnerable brain areas. Following experimentally induced cardiac arrest of 6 min duration, rats were resuscitated. After 3, 6, and 24 h of reperfusion, the thalamus and hippocampus of one hemisphere were analyzed for Fas/CD95 and FasL by immunoblotting and semiquantitative densitometry. Corresponding hemispheres were examined by immunohistochemistry. No significant changes in hippocampal Fas/CD95 expression were revealed in comparison to sham operated animals. In the thalamus, a significant reduction in Fas/CD95 expression was observed after 24 h of reperfusion. FasL expression in the hippocampus had declined after 3 and 6 h, as compared with control animals. In contrast, in the thalamus a significant induction of FasL expression was observed after 3 h. Immunohistochemistry revealed a predominantly neuronal expression of the two proteins. In light of the observed increased expression of FasL in the thalamus, such an induction may lead to significant activation of the Fas/CD95 signaling cascade. Our results suggest for the first time a possible role of the Fas/CD95-FasL system after global cerebral ischemia.

Comparison of stroke recognition and stroke severity scores for stroke detection in a single cohort

Objective First, to determine the sensitivity and specificity of six stroke recognition scores in a single cohort to improve interscore comparability. Second, to test four stroke severity scores repurposed to recognise stroke in parallel. Methods Of 9154 emergency runs, 689 consecutive cases of preclinically ‘suspected central nervous system disorder’ admitted to the emergency room (ER) of the Heidelberg University Hospital were included in the validation cohort. Using data abstracted from the neurological ER medical reports, retrospective assessment of stroke recognition scores became possible for the Cincinnati Prehospital Stroke Scale (CPSS), Face Arm Speech Test (FAST), Los Angeles Prehospital Stroke Screen (LAPSS), Melbourne Ambulance Stroke Screen (MASS), Medic Prehospital Assessment for Code Stroke (Med PACS) and Recognition of Stroke in the Emergency Room score (ROSIER), and that of stroke severity scores became possible for the Kurashiki Prehospital Stroke Scale (KPSS), Los Angeles Motor Scale (LAMS) and shortened National Institutes of Health Stroke Scale (sNIHSS)-8/sNIHSS-5. Test characteristics were calculated using the hospital discharge diagnosis as the reference standard. Results The CPSS and FAST had a sensitivity of 83% (95% CI 76 to 88) and 85% (78% to 90%) and a specificity of 69% (64% to 73%) and 68% (63% to 72%), respectively. The more complex LAPSS, MASS and Med PACS had a high specificity (92% to 98%) but low sensitivity (44% to 71%). In the ROSIER, sensitivity (80%, 73 to 85) and specificity (79%, 75 to 83) were similar. Test characteristics for KPSS, sNIHSS-8 and sNIHSS-5 were similar to the simple recognition scores (sensitivity 83% to 86%, specificity 60% to 69%). The LAMS offered only low sensitivity. Conclusions The simple CPSS and FAST scores provide good sensitivity for stroke recognition. More complex scores do not result in better diagnostic performance. Stroke severity scores can be repurposed to recognise stroke at the same time because test characteristics are comparable with pure stroke recognition scores. Particular shortcomings of the individual scores are discussed.

Neurological outcome and inflammation after cardiac arrest--effects of protein C in rats.

BACKGROUND The response of the human body to cardiac arrest (CA) and cardiopulmonary resuscitation is characterised by excessive coagulation, inadequate endogenous anti-coagulation and fibrinolysis as well as an inflammatory syndrome that closely resembles the immunological profile observed in patients with sepsis. Recombinant human activated protein C (rhAPC) has been found to be protective in severe sepsis and in animal models of stroke and spinal cord injury. In the present study, we evaluated the effects of rhAPC on neurological outcome after CA in rats. METHODS After 6 min of CA and subsequent cardiopulmonary resuscitation, male Wistar rats were randomized into 3 treatment groups: high dose rhAPC (2 mg/kg bolus and 0.1 mg/(kg h) for 6 h), low dose rhAPC (0.5 mg/kg and 0.025 mg/(kg h) for 6 h), and placebo (n=12 per treatment and reperfusion time). Neurological outcome was determined using a tape removal test and a composite neurological deficit score (NDS). As secondary measurements, we evaluated overall and neuronal survival, hippocampal caspase activity and inflammatory markers. RESULTS No difference between groups was found with the NDS. The tape removal test showed only a transitory improvement in the low dose group at 3 d after CA (P=0.041). No significant differences were observed for secondary measurements. CONCLUSION A clear and lasting effect of rhAPC on neurological outcome or inflammation after CA could not be shown in this study but the detailed analysis of the postresuscitation syndrome given here builds a firm basis for further research.

Pre- and postconditioning effect of Sevoflurane on myocardial dysfunction after cardiopulmonary resuscitation in rats.

Post-resuscitation myocardial dysfunction is an important cause of death in the intensive care unit after initially successful cardiopulmonary resuscitation (CPR) of pre-hospital cardiac arrest (CA) patients. Volatile anaesthetics reduce ischaemic-reperfusion injury in regional ischaemia in beating hearts. This effect, called anaesthetic-induced pre- or postconditioning, can be shown when the volatile anaesthetic is given either before regional ischaemia or in the reperfusion phase. However, up to now, little data exist for volatile anaesthetics after global ischaemia due to CA. Therefore, the goal of this study was to clarify whether Sevoflurane improves post-resuscitation myocardial dysfunction after CA in rats. Following institutional approval by the Governmental Animal Care Committee, 144 male Wistar rats (341±19g) were randomized either to a control group or to one of the 9 interventional groups receiving 0.25 MAC, 0.5 MAC or 1 MAC of Sevoflurane for 5min either before resuscitation (SBR), during resuscitation (SDR) or after resuscitation (SAR). After 6min of electrically induced ventricular fibrillation CPR was performed. Before CA (baseline) as well as 1h and 24h after restoration of spontaneous circulation (ROSC), continuous measurement of ejection fraction (EF), and preload adjusted maximum power (PAMP) as primary outcome parameters and end systolic pressure (ESP), end diastolic volume (EDV) and maximal slope of systolic pressure increment (dP/dtmax) as secondary outcome parameters was performed using a conductance catheter. EF was improved in all Sevoflurane treated groups 1h after ROSC in comparison to control, except for the 0.25 MAC SDR and 0.25 MAC SAR group (0.25 MAC SBR: 38±8, p=0.02; 0.5 MAC SBR: 39±7, p=0.04; 1 MAC SBR: 40±6, p=0.007; 0.5 MAC SDR: 38±7, p=0.02; 1 MAC SDR: 40±6, p=0.006; 0.5 MAC SAR: 39±6, p=0.01; 1 MAC SAR: 39±6, p=0.002, vs. 30±7%). Twenty-four hours after ROSC, EF was higher than control in all interventional groups (p<0.05 for all groups). EF recovered to baseline values 24h after ROSC in all SBR and SAR groups. PAMP was improved in comparison to control (4.6±3.0mW/μl(2)) 24h after ROSC in 0.5 MAC SBR (9.4±6.9mW/μl(2), p=0.04), 1 MAC SBR (8.9±4.4mW/μl(2), p=0.04), 1 MAC SDR (8.0±5.7mW/μl(2), p=0.04), and 1 MAC SAR (7.3±3.5mW/μl(2), p=0.04). ESP, EDV, and dP/dtmax was not different from control 1h as well as 24h after ROSC with the exception of 1 MAC SDR with a reduced ESP 1h after ROSC (89±16 vs. 103±22mmHg, p=0.04). Sevoflurane treatment did not affect survival rate. This animal study of CA and resuscitation provides the hypothesis that pharmacological pre- or postconditioning with the volatile anaesthetic Sevoflurane - administered before CA, during resuscitation or after ROSC - results in an improved myocardial inotropy 24h after ROSC. Sevoflurane treatment seems to improve EF even in the early phase of reperfusion 1h after ROSC. Therefore further targeted studies on the optimal dose and time point of administration of Sevoflurane in cardiopulmonary resuscitation seem to be worthwhile (Institutional protocol number: 35-9185.81/G-24/08).

Extracorporeal versus conventional cardiopulmonary resuscitation after ventricular fibrillation cardiac arrest in rats: a feasibility trial.

Objectives:Extracorporeal cardiopulmonary resuscitation with cardiopulmonary bypass potentially provides cerebral reperfusion, cardiovascular support, and temperature control for resuscitation from cardiac arrest. We hypothesized that extracorporeal cardiopulmonary resuscitation is feasible after ventricular fibrillation cardiac arrest in rats and improves outcome versus conventional cardiopulmonary resuscitation. Design:Prospective randomized study. Setting:University laboratory. Subjects:Adult male Sprague-Dawley rats. Interventions:Rats (intubated, instrumented with arterial and venous catheters and cardiopulmonary bypass cannulae) were randomized to conventional cardiopulmonary resuscitation, extracorporeal cardiopulmonary resuscitation with/without therapeutic hypothermia, or sham groups. After 6 minutes of ventricular fibrillation cardiac arrest, resuscitation was performed with drugs (epinephrine, sodium bicarbonate, and heparin), ventilation, either cardiopulmonary resuscitation or extracorporeal cardiopulmonary resuscitation, and defibrillation. Temperature was maintained at 37.0°C or 33.0°C for 12 hours after restoration of spontaneous circulation. Neurologic deficit scores, overall performance category, histological damage scores (viable neuron counts in CA1 hippocampus at 14 days; % of sham), and microglia proliferation and activation (Iba-1 immunohistochemistry) were assessed. Measurements and Main Results:Extracorporeal cardiopulmonary resuscitation induced hypothermia more rapidly than surface cooling (p < 0.05), although heart rate was lowest in the extracorporeal cardiopulmonary resuscitation hypothermia group (p < 0.05). Survival, neurologic deficit scores, overall performance category, and surviving neurons in CA1 did not differ between groups. Hypothermia significantly reduced neuronal damage in subiculum and thalamus and increased the microglial response in CA1 at 14 days (all p < 0.05). There was no benefit from extracorporeal cardiopulmonary resuscitation versus cardiopulmonary resuscitation on damage in any brain region and no synergistic benefit from extracorporeal cardiopulmonary resuscitation with hypothermia. Conclusions:In a rat model of 6-minute ventricular fibrillation cardiac arrest, cardiopulmonary resuscitation or extracorporeal cardiopulmonary resuscitation leads to survival with intact neurologic outcomes. Twelve hours of mild hypothermia attenuated neuronal death in subiculum and thalamus but not CA1 and, surprisingly, increased the microglial response. Resuscitation from ventricular fibrillation cardiac arrest and rigorous temperature control with extracorporeal cardiopulmonary resuscitation in a rat model is feasible, regionally neuroprotective, and alters neuroinflammation versus standard resuscitation. The use of experimental extracorporeal cardiopulmonary resuscitation should be explored using longer insult durations.

Hypothermia and neuroprotection by sulfide after cardiac arrest and cardiopulmonary resuscitation.

BACKGROUND Poor neurological outcome remains a major problem in patients suffering cardiac arrest. Recent data have demonstrated potent neuroprotective effects of the administration of sulfide donor compounds after ischaemia/reperfusion injury following cardiac arrest and resuscitation. Therefore, we sought to evaluate the impact of sodium sulfide (Na(2)S), a liquid hydrogen sulfide donor on core body temperature and neurological outcome after cardiac arrest in rats. METHODS Fifty male Wistar rats were randomized into two groups (sulfide vs. placebo, n=25 per group). Cardiac arrest was induced by transoesophageal ventricular fibrillation during general anaesthesia. After 6 min of global cerebral ischaemia, animals were resuscitated by external chest compressions combined with defibrillation. An investigator blinded bolus of either Na(2)S (0.5 mg/kg body weight) or placebo 1 min before the beginning of CPR, followed by a continuous infusion of Na(2)S (1 mg/kg body weight/h) or placebo for 6 h, was administered intravenously. 1 day, 3 days, and 7 days after restoration of spontaneous circulation, neurological outcome was evaluated by a tape removal test. After 7 days of reperfusion, coronal brain sections were analyzed by TUNEL- and Nissl-staining. A caspase activity assay was used to determine antiapoptotic properties of Na(2)S. RESULTS Temperature course was similar in both groups (mean minimal temperature in the sulfide group 31.3±1.2°C vs. 30.8±1.9°C in the placebo group; p=0.29). Despite significant neuroprotection demonstrated by the tape removal test after 3 days of reperfusion in the sulfide treated group, there was no significant difference in neuronal survival at day 7. Likewise results from TUNEL-staining revealed no differences in the amount of apoptotic cell death between the groups after 7 days of reperfusion. CONCLUSION In our rat model of cardiac arrest, sulfide therapy was associated with only a short term beneficial effect on neurological outcome.

Time course of the hypothermic response to continuously administered neurotensin

Intracerebroventricular administration of the tridecapeptide neurotensin is known to elicit hypothermia in rodents for few hours. In the present study, we investigated a continuous intracerebroventricular infusion regimen for prolongation of the hypothermic effect. Male Wistar-Han rats (n=13) received neurotensin 10-50 microg/h for 48 h, while their body temperature was monitored continuously. This protocol led to a dose-dependent decrease of body temperature down to 35-36 degrees C. The nadir of hypothermia lasted for approximately 4h and normothermia was re-established after 12-24h. Furthermore, abundance of neurotensin in the hypothalamus was determined after 6 and 30 h by western blotting. High levels were still found at 30 h, while the rats had already become normothermic at that time. In summary, continuous infusion of neurotensin led to prolongation of the known hypothermic response, however resulted in development of tolerance.