EMS defibrillation-first policy may not improve outcome in out-of-hospital cardiac arrest

OBJECTIVE: Early defibrillation using automated external defibrillators (AEDs) has been advocated to improve survival in witnessed out-of-hospital cardiac arrest (OHCA) due to pulseless ventricular tachycardia (VT) and ventricular fibrillation (VF). However, when VT/VF is untreated and prolonged for more than a few minutes, defibrillation using AEDs may fail. METHODS: This retrospective study reviewed the charts from local emergency medical service (EMS) between the years 1993 to 2001 to evaluate the value of the AED after its introduction into our EMS. All witnessed OHCA due to VT/VF were analysed; cases of collapse witnessed by EMS were excluded. The primary endpoint was defined as survival to hospital discharge and at 1-year follow-up, and the secondary endpoint as survival without major neurological deficit. A total of 76 patients were treated for witnessed VT/VF before the implementation of the AED and 92 patients after its implementation. RESULTS: Before the introduction of paramedic AED defibrillation, physician defibrillation was performed at 15.6 min (+/-5.5, S.D.). After the introduction of AED defibrillation, paramedic defibrillation was performed at 5.7 min (+/-2.4, S.D.); the mean response interval from the call to defibrillation was shortened significantly (P<0.001). At the same time, survival to hospital discharge decreased from 23.7% (18/76 patients) to 14.1% (13/92) (P=0.112) and at 1-year follow-up from 17.1% (13/76) to 9.8% (9/92) (P=0.161). Favourable neurological outcome at 1-year follow-up also decreased from 14.5% (11/76) to 8.7% (8/92) (P=0.239). CONCLUSION: Implementation of the AED did not improve survival or a favourable neurological outcome in patients with OHCA due to VF/VT. However, with 5.7 min time to defibrillation, our EMS did not meet the criteria for early defibrillation. For prolonged periods of VT/VF, initial basic life support (BLS) may be superior to immediate AED. If response times of <4 min cannot be attained by the emergency systems, reconsidering of resuscitation algorithms seems to be advisable.     

Epinephrine,vasopressin, and nitroglycerin improve neurologic outcome in porcine asphyxial cardiac arrest

Aim

The aim of the present study was to assess whether the combination of epinephrine, vasopressin, and nitroglycerin would improve initial resuscitation success, 24-hour survival, and neurologic outcome compared with epinephrine alone in a swine model of asphyxial cardiac arrest (CA).

Materials and Methods

This prospective randomized experimental study was conducted at a laboratory research department. Twenty male Landrace/Large-White pigs 12 to 15 weeks of age were investigated. Asphyxial CA was induced by occlusion of the endotracheal tube. Pigs remained untreated for 4 minutes before attempting resuscitation by unclamping the endotracheal tube, mechanical ventilation, chest compressions, and epinephrine (group E) or a combination of epinephrine with vasopressin and nitroglycerin (group EVN) administered intravenously. In case of restoration of spontaneous circulation, the animals were supported for 30 minutes and then observed for 24 hours.

Results

Coronary perfusion pressure and mean arterial pressure were significantly increased during cardiopulmonary resuscitation in group EVN. In both groups, restoration of spontaneous circulation and survival rates were comparable (P value, nonsignificant). At 24 hours after CA, neurologic deficit score was significantly better in animals treated with the combination pharmacotherapy (P < .001). Brain histologic damage score was also higher in group EVN compared with group E (P < .001). Total histologic damage score and neurologic deficit score showed a statistical significant correlation (P < .001).

Conclusion

In this porcine model of asphyxial CA, the addition of nitroglycerin to vasopressin and epinephrine maintained elevated coronary perfusion pressure during asphyxia CA and resulted in significantly better neurologic and histopathologic outcome in comparison with epinephrine alone.     

Hypertonic versus isotonic crystalloid infusion for cerebral perfusion pressure in a porcine experimental cardiac arrest model

BackgroundThe effect of intravenous (IV) fluid administration type on cerebral perfusion pressure (CePP) during cardiopulmonary resuscitation (CPR) is controversial. The purpose of this study was to evaluate the association between IV fluid type and CePP in a porcine cardiac arrest model.MethodsWe randomly assigned 12 pigs to the hypertonic crystalloid, isotonic crystalloid and no-fluid groups. After 4 min of untreated ventricular fibrillation (VF), chest compression was conducted for 2 cycles (CC only). Chest compression with IV fluid infusion (CC + IV) was followed for 2 cycles. Advanced life support, including defibrillation and epinephrine, was added for 8 cycles (ALS phase). Mean arterial pressure (MAP), intracranial pressure (ICP) and CePP were measured. A paired t-test was used to measure the mean difference in CePP.ResultsTwelve pigs underwent the experiment. The hypertonic crystalloid group showed higher CePP values than those demonstrated by the isotonic crystalloid group from ALS cycles 2 to 8. The MAP values in the hypertonic group were higher than those in the isotonic group starting at ALS cycle 2. The ICP values in the hypertonic group were lower than those in the isotonic group starting at ALS cycle 4. From ALS cycles 2 to 8, the reduction in the mean difference in the isotonic group was larger than that in the other groups.ConclusionIn a VF cardiac arrest porcine study, the hypertonic crystalloid group showed higher CePP values by maintaining higher MAP values and lower ICP values than those of the isotonic crystalloid group.     

Perfluorocarbon induced intra-arrest hypothermia does not improve survival in a swine model of asphyxial cardiac arrest

Background

Pulseless electrical activity is an important cause of cardiac arrest. Our purpose was to determine if induction of hypothermia with a cold perfluorocarbon-based total liquid ventilation (TLV) system would improve resuscitation success in a swine model of asphyxial cardiac arrest/PEA.

Methods

Twenty swine were randomly assigned to control (C, no ventilation, n = 11) or TLV with pre-cooled PFC (n = 9) groups. Asphyxia was induced by insertion of a stopper into the endotracheal tube, and continued in both groups until loss of aortic pulsations (LOAP) was reached, defined as a pulse pressure less than 2 mmHg. The TLV animals underwent asphyxial arrest for an additional 2 min after LOAP, followed by 3 min of hypothermia, prior to starting CPR. The C animals underwent 5 min of asphyxia beyond LOAP. Both groups then underwent CPR for at least 10 min. The endpoint was the resumption of spontaneous circulation maintained for 10 min.

Results

Seven of 9 animals achieved resumption of spontaneous circulation (ROSC) in the TLV group vs. 5 of 11 in the C group (p = 0.2). The mean pulmonary arterial temperature was lower in total liquid ventilation animals starting 4 min after induction of hypothermia (TLV 36.3 ± 0.2 °C vs. C 38.1 ± 0.2 °C, p < 0.0001). Arterial pO₂ was higher in total liquid ventilation animals at 2.5 min of CPR (TLV 76 ± 12 mmHg vs. C 44 ± 2 mmHg; p = 0.03).

Conclusion

Induction of moderate hypothermia using perfluorocarbon-based total liquid ventilation did not improve ROSC success in this model of asphyxial cardiac arrest.     

Comparison of epinephrine and norepinephrine in the treatment of asphyxial or fibrillatory cardiac arrest in a porcine model

Many animal experiments have shown that alpha-receptor stimulation is a prerequisite for the improvement of myocardial perfusion during CPR. As there are no recent reports on the effectiveness of norepinephrine in the treatment of cardiac arrest, we investigated the effectiveness of epinephrine and norepinephrine after asphyxial or ventricular fibrillation cardiac arrest using a porcine model. After 3 min of asphyxial cardiac arrest, seven animals each received either 45 micrograms/kg epinephrine, 45 micrograms/kg norepinephrine, or placebo (controls). All drugs were given blind. All seven animals given epinephrine could be resuscitated after 174 +/- 53 sec, whereas six of seven given norepinephrine could be resuscitated after 473 +/- 116 sec. None of the seven given the placebo could be resuscitated. After 4 min of ventricular fibrillation cardiac arrest, none of the seven animals that received defibrillating countershocks at 4 min without either mechanical measures or drug therapy, and none of the seven that received CPR and countershocks but no drugs, could be resuscitated. In the group that received CPR plus 45 micrograms/kg epinephrine, defibrillation and restoration of spontaneous circulation were achieved in six of seven animals in 667 +/- 216 sec. In the group that received CPR plus 45 micrograms/kg norepinephrine, defibrillation and restoration of spontaneous circulation were achieved in all seven animals in the significantly shorter time of 86 +/- 18 sec. In this porcine model, norepinephrine appeared superior to the same dose of epinephrine in the treatment of ventricular fibrillation, with respect to resuscitation time.     

Modulation of nitric oxide expression with methylene blue does not improve outcome after hypovolemic cardiac arrest

Aim of the study

We recently reported that female sex protects against cerebral and cardiac injury after hypovolemic cardiac arrest (CA), independent of sex hormone effects. As female sex was also associated with a smaller increase in inducible and neuronal nitric oxide synthase (NOS), we hypothesised that nitric oxide inhibition with methylene blue (MB) improves the outcome, primarily in male animals.

Methods

Twenty sexually immature piglets (10 males and 10 females) were bled to mean arterial blood pressure of 35 mmHg, and were subjected to 2 min of untreated CA followed by 8 min of open chest cardiopulmonary resuscitation (CPR). Volume resuscitation was started during CPR with intravenous administration of 3 ml kg⁻¹ hypertonic saline-dextran. Methylene blue was then administered as bolus of 2.5 mg kg⁻¹ over 20 min, followed by 1.5 mg kg⁻¹ infusion over 40 min. Historical data from 21 animals were used as control (no MB). Hemodynamic parameters, myocardial injury (troponin I), and short-term survival (3-h) were evaluated. Histopathological evaluation of heart specimens was performed.

Results

There were no differences between male and female animals in survival or resuscitation rate. After CA female piglets had significantly greater systolic and mean arterial pressures, and had lower troponin I plasma concentrations compared to male piglets, with or without MB. No difference was observed in histopathological analysis of heart specimens between sexes.

Conclusions

After resuscitation from hypovolemic CA, female sex protects against cardiac injury, independent of sex hormones. Modulation of NO expression with MB does not improve survival or myocardial histological injury in either sex.     

Too cold may not be so cool: spontaneous hypothermia as a marker of poor outcome after cardiac arrest

In a recent issue of Critical Care, den Hartog and colleagues show an association between spontaneous hypothermia, defined by an admission body temperature <35°C, and poor outcome in patients with coma after cardiac arrest (CA) treated with therapeutic hypothermia (TH). Given that TH alters neurological prognostication, studies aiming to identify early markers of injury severity and outcome are welcome, since they may contribute overall to optimize the management of comatose CA patients. This study provides an important message to clinicians involved in post-resuscitation care and raises important questions that need to be taken into account in future studies.     

Comparison of epinephrine and vasopressin in a pediatric porcine model of asphyxial cardiac arrest

OBJECTIVE: This study was designed to compare the effects of vasopressin vs. epinephrine vs. the combination of epinephrine with vasopressin on vital organ blood flow and return of spontaneous circulation in a pediatric porcine model of asphyxial arrest. DESIGN: Prospective, randomized laboratory investigation using an established porcine model for measurement of hemodynamic variables, organ blood flow, blood gases, and return of spontaneous circulation. SETTING: University hospital laboratory. SUBJECTS: Eighteen piglets weighing 8-11 kg. INTERVENTIONS: Asphyxial cardiac arrest was induced by clamping the endotracheal tube. After 8 mins of cardiac arrest and 8 mins of cardiopulmonary resuscitation, a bolus dose of either 0.8 units/kg vasopressin (n = 6), 200 microg/kg epinephrine (n = 6), or a combination of 45 microg/kg epinephrine with 0.8 units/kg vasopressin (n = 6) was administered in a randomized manner. Defibrillation was attempted 6 mins after drug administration. MEASUREMENTS AND MAIN RESULTS: Mean +/- SEM coronary perfusion pressure, before and 2 mins after drug administration, was 13 +/- 2 and 23 +/- 6 mm Hg in the vasopressin group; 14 +/- 2 and 31 +/- 4 mm Hg in the epinephrine group; and 13 +/- 1 and 33 +/- 6 mm Hg in the epinephrine-vasopressin group, respectively (p = NS). At the same time points, mean +/- SEM left ventricular myocardial blood flow was 44 +/- 31 and 44 +/- 25 mL x min-(1) x 100 g(-1) in the vasopressin group; 30 +/- 18 and 233 +/- 61 mL x min(-1) x 100 g(-1) in the epinephrine group; and 36 +/- 10 and 142 +/- 57 mL x min(-1) x 100 g(-1) in the epinephrine-vasopressin group (p < .01 epinephrine vs. vasopressin; p < .02 epinephrine-vasopressin vs. vasopressin). Total cerebral blood flow trended toward higher values after epinephrine-vasopressin (60 +/- 19 mL x min(-1) x 100 g(-1)) than after vasopressin (36 +/- 17 mL x min(-1) x 100 g(-1)) or epinephrine alone (31 +/- 7 mL x min(-1) x 100 g(-1); p = .07, respectively). One of six vasopressin, six of six epinephrine, and four of six epinephrine-vasopressin-treated animals had return of spontaneous circulation (p < .01, vasopressin vs. epinephrine). CONCLUSIONS: Administration of epinephrine, either alone or in combination with vasopressin, significantly improved left ventricular myocardial blood flow during cardiopulmonary resuscitation. Return of spontaneous circulation was significantly more likely in epinephrine-treated pigs than in animals resuscitated with vasopressin alone.     

Reducing ventilation frequency during cardiopulmonary resuscitation in a porcine model of cardiac arrest

INTRODUCTION: American Heart Association/American College of Cardiology guidelines recommend a compression-to-ventilation ratio (C/V ratio) of 15:2 during cardiopulmonary resuscitation (CPR) for out-of-the-hospital cardiac arrest. Recent data have shown that frequent ventilations are unnecessary and may be harmful during CPR, since each positive-pressure ventilation increases intrathoracic pressure and may increase intracranial pressure and decrease venous blood return to the right heart and thereby decrease both the cerebral and coronary perfusion pressures. HYPOTHESIS: We hypothesized that reducing the ventilation rate by increasing the C/V ratio from 15:2 to 15:1 will increase vital-organ perfusion pressures without compromising oxygenation and acid-base balance. METHODS: Direct-current ventricular fibrillation was induced in 8 pigs. After 4 min of untreated ventricular fibrillation without ventilation, all animals received 4 min of standard CPR with a C/V ratio of 15:2. Animals were then randomized to either (A) a C/V ratio of 15:1 and then 15:2, or (B) a C/V ratio of 15:2 and then 15:1, for 3 min each. During CPR, ventilations were delivered with an automatic transport ventilator, with 100% oxygen. Right atrial pressure, intratracheal pressure (a surrogate for intrathoracic pressure), aortic pressure, and intracranial pressure were measured. Coronary perfusion pressure was calculated as diastolic aortic pressure minus right atrial pressure. Cerebral perfusion pressure was calculated as mean aortic pressure minus mean intracranial pressure. Arterial blood gas values were obtained at the end of each intervention. A paired t test was used for statistical analysis, and a p value < 0.05 was considered significant. RESULTS: The mean +/- SEM values over 1 min with either 15:2 or 15:1 C/V ratios were as follows: intratracheal pressure 0.93 +/- 0.3 mm Hg versus 0.3 +/- 0.28 mm Hg, p = 0.006; coronary perfusion pressure 10.1 +/- 4.5 mm Hg versus 19.3 +/- 3.2 mm Hg, p = 0.007; intracranial pressure 25.4 +/- 2.7 mm Hg versus 25.7 +/- 2.7 mm Hg, p = NS; mean arterial pressure 33.1 +/- 3.7 mm Hg versus 40.2 +/- 3.6 mm Hg, p = 0.007; cerebral perfusion pressure 7.7 +/- 6.2 mm Hg versus 14.5 +/- 5.5 mm Hg, p = 0.008. Minute area intratracheal pressure was 55 +/- 17 mm Hg . s versus 22.3 +/- 10 mm Hg . s, p < 0.001. End-tidal CO(2) with 15:2 versus 15:1 was 24 +/- 3.6 mm Hg versus 29 +/- 2.5 mm Hg, respectively, p = 0.001. Arterial blood gas values were not significantly changed with 15:2 versus 15:1 C/V ratios: pH 7.28 +/- 0.03 versus 7.3 +/- 0.03; P(aCO(2)) 37.7 +/- 2.9 mm Hg versus 37.6 +/- 3.5 mm Hg; and P(aO(2)) 274 +/- 36 mm Hg versus 303 +/- 51 mm Hg. CONCLUSIONS: In a porcine model of ventricular fibrillation cardiac arrest, reducing the ventilation frequency during CPR by increasing the C/V ratio from 15:2 to 15:1 resulted in improved vital-organ perfusion pressures, higher end-tidal CO(2) levels, and no change in arterial oxygen content or acid-base balance.     

Shen-fu injection attenuates postresuscitation myocardial dysfunction in a porcine model of cardiac arrest

To investigate the effect of Shen-Fu injection (SFI) for the management of postresuscitation myocardial dysfunction in a porcine model of cardiac arrest. Ventricular fibrillation was induced electrically in anesthetized domestic swine. After 4 min of untreated ventricular fibrillation, cardiopulmonary resuscitation was initiated. Sixteen successfully resuscitated pigs were randomized to receive a continuous infusion of either SFI (0.24 mg/min) or saline placebo for 6 h, beginning 15 min after return of spontaneous circulation (ROSC). The SFI treatment produced better left ventricular +dP/dtmax, -dP/dtmax, cardiac output, and ejection fraction after ROSC. The SFI treatment also produced lower serum cardiac troponin I, lactate levels, and left ventricle malondialdehyde content after ROSC, whereas left ventricle superoxide dismutase, Na-K-ATPase, and Ca-ATPase activity were significantly increased in the SFI group when compared with saline group. The cardioprotective effect of SFI was further confirmed by myocardial ultrastructure examination. Shen-Fu injection can attenuate postresuscitation myocardial dysfunction through beneficial effects on energy metabolism and remarkable antioxidant capacity.     

Shen-fu injection attenuates postresuscitation lung injury in a porcine model of cardiac arrest

ObjectiveTo investigate the effects of Shen-Fu injection (SFI) on postresuscitation lung injury in a porcine model of cardiac arrest.MethodsTwenty-four anaesthetised male Landrace pigs were subjected to 4 min of untreated ventricular fibrillation (VF), followed by standard cardiopulmonary resuscitation. Sixteen successfully resuscitated pigs were randomised into two groups (eight pigs per group); one group received an SFI infusion and the other group received a normal saline infusion, at an infusion rate of 0.24 mg/min from 15 min after the return of spontaneous circulation (ROSC) until 6 h after ROSC.ResultsOxygenation index, respiratory index, oxygen delivery, oxygen consumption, oxygen extraction, dynamic lung compliance, airway resistance, external vascular lung water index, and pulmonary vascular permeability index at 15 min, 30 min, 1 h, 2 h, 4 h, and 6 h after ROSC were all worse than baseline in the saline group, and were all better in the SFI group than in the saline group. The pulmonary protective effects of SFI were further confirmed by histopathological and ultrastructural observations of lung tissue. SFI infusion resulted in lower apoptosis index, caspase-3 protein expression, and malondialdehyde content of lung tissue after ROSC, and increased Bcl-2 protein expression and superoxide dismutase, Na⁺-K⁺-ATPase, and Ca²⁺-ATPase activity compared with the saline group.ConclusionShen-Fu injection can attenuate postresuscitation lung injury through suppression of lung cell apoptosis and improvement of energy metabolism and antioxidant capacity.     

Early diffusion-weighted magnetic resonance imaging in children after cardiac arrest may provide valuable prognostic information on clinical outcome

Objective

We examined whether early diffusion-weighted magnetic resonance imaging (DW-MRI) abnormalities of the brain and variation of apparent diffusion coefficient (ADC) values can provide prognostic information on clinical outcome in children following cardiac arrest (CA).

Design

Retrospective study.

Setting

A 12-bed paediatric intensive care unit (PICU).

Patients

Children aged between 1 month and 18 years who had DW-MRI with ADC measurement within the first week following CA. Neurological outcomes were assessed using the Pediatric Cerebral Performance Category Scale (PCPC). Differences between the favourable (PCPC ≤3) and unfavourable (PCPC ≥4) groups were analysed with regard to clinical data, electrophysiological patterns as well as qualitative and quantitative DW-MRI abnormalities.

Results

Twenty children with a median age of 20 months (1.5–185) and a male/female sex ratio of 1.5 underwent DW-MRI after CA with a median delay of 3 days (1–7). Aetiologies of CA were (i) asphyxia (n = 10), (ii) haemodynamic (n = 5) or (iii) unknown (n = 5). With regard to DW-MRI findings, the unfavourable outcome group (n = 8) was associated with cerebral cortex (p = 0.02) and basal ganglia (p = 0.005) lesions, with a larger number of injured brain regions (p = 0.001) and a global decrease in measured ADC signal (p = 0.008). Normal DW-MRI (n = 5) was exclusively associated with the favourable outcome group (n = 12).

Conclusion

Qualitative, topographic and quantitative analysis of early DW-MRI with ADC measurement in children following CA may provide valuable prognostic information on neurological outcomes.     

Comparison of the efficacy of nifekalant and amiodarone in a porcine model of cardiac arrest

Objective

To compare the efficacy of nifekalant and amiodarone in the treatment of cardiac arrest in a porcine model.

Methods

After 4 min of untreated ventricular fibrillation, animals were randomly treated with nifekalant (2 mg kg⁻¹), amiodarone (5 mg kg⁻¹) or saline placebo (n = 12 pigs per group). Precordial compression and ventilation were initiated after drug administration and defibrillation was attempted 2 min later. Hemodynamics were continuously measured for 6 h after successful resuscitation.

Results

Compared with saline, nifekalant and amiodarone equally decreased the number of electric shocks, defibrillation energy, epinephrine dose, and duration of cardiopulmonary resuscitation required for successful resuscitation (P < 0.01). The incidence of restoration of spontaneous circulation (ROSC) and the 24-h survival rate were higher in both antiarrhythmic drug groups (P < 0.05) vs. the saline group. Furthermore, post-resuscitation myocardial dysfunction at 4-6 h after successful resuscitation was improved in animals given antiarrhythmic drugs as compared with the saline group (P < 0.05). There were no differences between nifekalant and amiodarone for any of these parameters.

Conclusion

The effect of nifekalant was similar to that of amiodarone for improving defibrillation efficacy and for the treatment of cardiac arrest. Administration of either nifekalant or amiodarone before defibrillation increased the ROSC and 24-h survival rates and improved post-resuscitation cardiac function in this porcine model.     

Haemodynamic variables and functional outcome in hypothermic patients following out-of-hospital cardiac arrest

Aim of the study

To evaluate the association between haemodynamic variables during the first 24 h after intensive care unit (ICU) admission and neurological outcome in out-of-hospital cardiac arrest (OHCA) victims undergoing therapeutic hypothermia.

Methods

In a multi-disciplinary ICU, records were reviewed for comatose OHCA patients undergoing therapeutic hypothermia. The hourly variable time integral of haemodynamic variables during the first 24 h after admission was calculated. Neurologic outcome was assessed at day 28 and graded as favourable or adverse based on the Cerebral Performance Category of 1–2 and 3–5. Bi- and multivariate regression models adjusted for confounding variables were used to evaluate the association between haemodynamic variables and functional outcome.

Results

67/134 patients (50%) were classified as having favourable outcome. Patients with adverse outcome had a higher mean heart rate (73 [62–86] vs. 66 [60–78] bpm; p = 0.04) and received noradrenaline more frequently (n = 17 [25.4%] vs. n = 9 [6%]; p = 0.02) and at a higher dosage (128 [56–1004] vs. 13 [2–162] μg h⁻¹; p = 0.03) than patients with favourable outcome. The mean perfusion pressure (mean arterial blood pressure minus central venous blood pressure) (OR = 1.001, 95% CI  = 1–1.003; p = 0.04) and cardiac index time integral (OR = 1.055, 95% CI = 1.003–1.109; p = 0.04) were independently associated with adverse outcome at day 28.

Conclusion

Mean perfusion pressure and cardiac index during the first 24 h after ICU admission were weakly associated with neurological outcome in an OHCA population undergoing therapeutic hypothermia. Further studies need to elucidate whether norepinephrine-induced increases in perfusion pressure and cardiac index may contribute to adverse neurologic outcome following OHCA.