BACKGROUND AND PURPOSE: Hetereothermic mammals tolerate hypoxia during euthermy and torpor, and evidence suggests this tolerance may extend beyond hypoxia to cerebral ischemia. During hibernation, CA1 hippocampal neurons endure extreme fluctuations in cerebral blood flow during transitions into and out of torpor as well as reductions in cerebral blood flow during torpor. In vitro studies likewise show evidence of ischemia tolerance in hippocampal slices harvested from euthermic ground squirrels; however, no studies have investigated tolerance in a clinically relevant model of in vivo global cerebral ischemia. The purpose of the present study was to test the hypothesis that the euthermic Arctic ground squirrel (AGS; Spermophillus parryii) is resistant to injury from asphyxial cardiac arrest (CA). METHODS: Estrous-matched female rats were used as a positive control. Female euthermic AGS and rats were subjected to 8-minute CA. At the end of 7 days of reperfusion, AGS and rats were fixed for histopathological assessment. RESULTS: In rats subjected to CA, the number of ischemic neurons was significantly higher (P
To evaluate the effects of therapeutic hypothermia (HT) of 33 degrees C after cardiac arrest (CA) on cardiac arrhythmias, heart rate variability (HRV), and their prognostic value.
Prospective, comparative substudy of a randomized controlled trial of mild HT after out-of-hospital CA, the European Hypothermia After Cardiac Arrest study.
Intensive care unit of a tertiary referral hospital (Helsinki University Hospital).
Seventy consecutive adult patients resuscitated from out-of-hospital ventricular fibrillation were randomly assigned either to therapeutic HT of 33 degrees C or normothermia.
Patients randomized to HT were cooled with an external cooling device for 24 hours and then allowed to rewarm slowly during 12 hours. In the normothermia group, the core temperature was kept 100 msec of the 24-48-hour recording in the HT group (p = 0.018) predicted good outcome.
The use of therapeutic HT of 33 degrees C for 24 hours after CA was not associated with an increase in clinically significant arrhythmias. Preserved 24 to 48-hour HRV may be a predictor of favorable outcome in patients with CA treated with HT.
Comment In: Crit Care Med. 2009 Feb;37(2):735-619325360
Reduced heart rate (HR) variability is associated with increased risk of cardiac arrest in patients with coronary artery disease. In this study, the power spectral components of HR variability and their circadian pattern in 22 survivors of out-of-hospital cardiac arrest not associated with acute myocardial infarction were compared with those of 22 control patients matched with respect to age, sex, previous myocardial infarction, ejection fraction and number of diseased coronary arteries. Survivors of cardiac arrest had significantly lower 24-hour average standard deviation of RR intervals than control patients (29 +/- 10 vs 51 +/- 15 ms, p less than 0.001), and the 24-hour mean high frequency spectral area was also lower in survivors of cardiac arrest than in control patients (13 +/- 7 ms2 x 10 vs 28 +/- 14 ms2 x 10, p less than 0.01). In a single cosinor analysis, a significant circadian rhythm of HR variability was observed in both groups with the acrophase of standard deviation of RR intervals and high-frequency spectral area occurring between 3 and 6 A.M. which was followed by an abrupt decrease in HR variability after arousal. The amplitude of the circadian rhythm of HR variability did not differ between the groups. Thus, HR variability is reduced in survivors of cardiac arrest but its circadian rhythm is maintained so that a very low HR variability is observed in the morning after awakening, corresponding to the time period at which the incidence of sudden cardiac death is highest.
BACKGROUND: Information from the Swedish Cardiac Arrest Registry was used to investigate: (a) The proportion of patients suffering an out-of-hospital cardiac arrest who were given bystander cardiopulmonary resuscitation (B-CPR). (b) Where and by whom B-CPR was given. (c) The effect of B-CPR on survival. METHOD: a prospective, observational study of cardiac arrests reported to the Swedish Cardiac Arrest Registry. Analyses were based on standardised reports of out-of-hospital cardiac arrests from ambulance organisations in Sweden, serving 60% of the Swedish population. From 1983 to 1995 approximately 15-20% of the population had been trained in CPR. RESULTS: Of 9877 patients, collected between January 1990 and May 1995, B-CPR was attempted in 36%. In 56% of these cases, the bystanders were lay persons and in 25% they were medical personnel. Most of the arrests took place at home (69%) and only 23% of these patients were given B-CPR in contrast to cardiac arrest in other places where 53% were given CPR. Survival to 1 month was significantly higher in all cases that received B-CPR (8.2 vs. 2.5%). The odds ratio for survival to 1 month with B-CPR was in a logistic regression analysis 2.5 (95% CI 1.9-3.1). CONCLUSIONS: In Sweden, the willingness and ability to perform B-CPR appears to be relatively widespread. More than half of B-CPR was performed by laypersons. B-CPR resulted in a two to threefold increase in survival.
In the context of post-mortem organ donation, there is an obvious need for certainty regarding the legal definition and determination of death, as individuals must be legally pronounced dead before organs may be procured for donation. Surprisingly then, the legal situation in Canada with regard to the definition and determination of death is uncertain. The purpose of this review is to provide anesthesiologists and critical care specialists with a medico-legal perspective regarding the definition and determination of death (particularly as it relates to non-heart-beating donor protocols) and to contribute to ongoing improvement in policies, protocols, and practices in this area.
The status quo with regard to the current legal definition of death is presented as well as the criteria for determining if and when death has occurred. A number of important problems with the status quo are described, followed by a series of recommendations to address these problems.
The legal deficiencies regarding the definition and determination of death in Canada may place health care providers at risk of civil or criminal liability, discourage potential organ donation, and frustrate the wishes of some individuals to donate their organs. The definition and criteria for the determination of death should be clearly set out in legislation. In addition, the current use of non-heart-beating donor protocols in Canada will remain inconsistent with Canadian law until more persuasive evidence on the potential return of cardiac function after cardiac arrest is gathered and made publicly available or until a concrete proposal to abandon the dead donor rule and amend Canadian law is adopted following a process of public debate and intense multidisciplinary review.
Comment In: Can J Anaesth. 2009 Nov;56(11):789-9219711143
A 36-year-old male, who 1 year previously had survived a large anterior myocardial infarction, followed by cardiac arrest, was treated a few months for psoriasis with oral methotrexate, at single weekly oral doses of up to 10 mg, when he had to be hospitalized due to anginal pain and palpitation. Repeated 24-hour electrocardiogram recordings revealed ventricular ectopy up to 580 premature beats per hour. The ventricular premature beats were almost completely abolished after a few days' discontinuation of methotrexate therapy but recurred a few hours after an attempt to restart it had been made. A coronary angiogram showed only minimal wall abnormalities. Electrophysiological testing and endomyocardial biopsy were normal.
In advanced life support (ALS), time-cycled "loops" of chest compressions form the basis of action. However, the provider must compromise between interrupting compressions and detecting a change in cardiac rhythm. An "optimal" loop duration would best balance these choices. The current international CPR guidelines recommend 2-min loop durations. The aim of this study was to investigate the "optimal" loop duration in patients with initial asystole or pulseless electrical activity (PEA).
Detailed defibrillator recordings from 249 in-hospital cardiac arrests at the University of Chicago Medicine (Chicago, IL) and St. Olav University Hospital (Trondheim, Norway) were analysed. The clinical states of asystole, PEA, ventricular fibrillation/-tachycardia (VF/VT) and return of spontaneous circulation (ROSC) were annotated along the time axis. PEA and asystole were combined as a single state for the analysis of state development. The probability of staying in PEA/asystole over time was estimated non-parametrically. In addition, to distinguish between initial and secondary PEA/asystole, the latter was defined by the transition from VF/VT or ROSC.
Among patients with initial PEA (n=179), 25% and 50% of patients had left PEA/asystole after 4 and 9 min of ALS efforts, respectively. The corresponding time points for patients with initial asystole (n=70) were 7.3 and 13.3 min, respectively. The probability of transition from secondary PEA/asystole to ROSC or VF/VT varied between 10% and 20% in each 2-4 min interval.
The "optimal" first loop duration may be 4 min in initial PEA and 6-8 min in initial asystole. If secondary PEA/asystole is encountered, 2-min loop duration seems appropriate.