Factors influencing variable outcomes after ventricular fibrillation cardiac arrest of 15 minutes in dogs

Animal experiments with cardiac arrest and cardiopulmonary resuscitation (CPR) despite controlled insult and postinsult life support, have yielded variable individual outcomes. This report concerns 10 dog experiments with a standardized model of VF cardiac arrest with no flow for 10 min followed by CPR basic life support (BLS) from VF 10 to 15 min and then CPR advanced life support (ALS) with epinephrine at 15 min. Defibrillating countershocks began at 17 min, for restoration of spontaneous circulation. After controlled ventilation to 20 h and intensive care to 96 h, outcome was evaluated using the overall performance category (OPC) 1 (normal) (n5) vs. OPC 2-4 (impaired) (n5) (P less than 0.001). We searched for correlations between normal vs. impaired outcome in various prearrest, arrest and postarrest factors that are suspected to influence postarrest neurologic deficit. Prearrest variables were similar in the normal and impaired groups. Resuscitation variables were similar in both. Coronary perfusion pressure during CPR-ALS was higher in the normal outcome group (P = 0.03). Among postarrest variables, postarrest reperfusion pressure pattern (initial hypertensive bout), blood glucose, cardiac output, Hct, pHa, PaO2 and PaCO2 were the same. Our data support the importance of maximizing coronary perfusion pressure not only for restoration of heart beat but also as a possible predictor of improved cerebral outcome.

Cardiac resuscitability with cardiopulmonary bypass after increasing ventricular fibrillation times in dogs

Previous studies in dogs have shown resuscitation from prolonged cardiac arrest to conscious survival to be more effective with the use of cardiopulmonary bypass (CPB) than with standard advanced cardiac life support. This study compared cardiovascular resuscitability with CPB only after varying periods of cardiac arrest without artificial circulatory support in a canine model. Group 1 (ten) was subjected to ventricular fibrillation for 15 minutes; group 2 (ten) for 20 minutes; and group 3 (ten) for 30 minutes. All received total CPB after ventricular fibrillation without advanced cardiac life support to defibrillation at two to five minutes and partial CPB to four hours. In all three groups CPB with epinephrine generated normal coronary perfusion pressure and increased ventricular fibrillation amplitude significantly. In groups 1 and 2, CPB reperfusion allowed for successful defibrillation in less than five minutes, weaning from CPB in all dogs at four hours, and stable spontaneous circulation thereafter. In group 3, only five of ten dogs could be weaned from bypass at four hours, and all died early with myocardial necroses. It was concluded that CPB may be of value in the setting of prolonged cardiac arrest when advanced cardiac life support has not been provided or is unable to restore spontaneous heart-beat.

Hypertension with or without hemodilution after cardiac arrest in dogs

We studied blood flow-promoting therapies after cardiac arrest in 18 dogs. Our model consisted of ventricular fibrillation (no blood flow) lasting 12.5 minutes, controlled reperfusion with cardiopulmonary bypass and defibrillation within 5 minutes, controlled intermittent positive-pressure ventilation to 20 hours, and intensive care to 96 hours. Group I (control, n = 6) dogs were reperfused under conditions of normotension (mean arterial blood pressure 100 mm Hg) and normal hematocrit (greater than or equal to 35%). Group II (n = 6) and III (n = 6) dogs were treated with norepinephrine at the beginning of reperfusion to induce hypertension for 4 hours. In addition, group III dogs received hypervolemic hemodilution to a hematocrit of 20% using dextran 40. There were no differences in the time to recovery of electroencephalographic activity among groups. All six group I dogs remained severely disabled; in groups II and III combined, six of the 12 dogs achieved good outcome (p less than 0.01). Some regional histopathologic damage scores at 96 hours were better in groups II and/or III than in group I (neocortex: p less than 0.05 group II different from group I; hippocampus: p less than 0.01 both groups II and III different from group I). Total histopathologic damage scores were similar among the groups. A hypertensive bout with a peak mean arterial blood pressure of greater than or equal to 200 mm Hg beginning 1-5 minutes after the start of reperfusion was correlated with good outcome (p less than 0.01). Our results support the use of an initial bout of severe hypertension, but not the use of delayed hemodilution.

Deferred consent: use in clinical resuscitation research. Brain Resuscitation Clinical Trial II Study Group

Deferred consent, a new approach to the requirement for informed consent in clinical research, was used in a randomized clinical trial of brain resuscitation after cardiac arrest. Because patients were comatose and therapy had to be initiated immediately, traditional prospective consent usually could not be obtained. Using the deferred consent mechanism, family members were contacted after the first dose of experimental drug or placebo was administered and asked to consent for continued study participation. The vast majority of families were satisfied with the deferred consent mechanism. Their main concerns were about the safety of the experimental drug and whether the active drug or placebo was given. The concepts of randomization, blinding, and placebo-treated controls were generally not well understood. Although our experiences confirmed the impracticality of attempting to obtain traditional prospective consent in clinical resuscitation research, deferred consent was found to be a reasonable solution.

Therapeutic deep hypothermic circulatory arrest in dogs: a resuscitation modality for hemorrhagic shock with 'irreparable' injury

Early deaths from trauma are often caused by exsanguinating hemorrhage from injuries that appear "irreparable." We explored the limits of deep hypothermic circulatory arrest induced during hemorrhagic shock to enable repair of these injuries in a bloodless field. In 15 dogs, after 30 minutes of hemorrhagic shock (mean arterial pressure, 40 mm Hg), cardiopulmonary bypass (CPB) was used to cool to 15 degrees C in 13-37 minutes. After circulatory arrest of 60 (Group 1), 90 (Group 2), or 120 (Group 3) minutes, reperfusion and rewarming were accomplished by CPB. All dogs survived greater than 72 hours. Best neurologic deficit scores (ND) (0% = normal, 100% = brain death) were 0 +/- 0% (normal) in Group 1, 10 +/- 8% (mild disability) in Group 2, and 27 +/- 24% in Group 3. Outcome in Group 3 dogs ranged from near-normal to comatose. After perfusion-fixation sacrifice, brain histopathologic damage scores correlated with insult time, as did ND scores. Deep hypothermia can allow 60-90 min of circulatory arrest with good neurologic recovery, even after a period of severe hemorrhagic shock. This technique may allow repair of otherwise lethal injuries and survival without brain damage.

Evaporative cooling as an adjunct to ice bag use after resuscitation from heat-induced arrest in a primate model

Heat stroke and other hyperthermia-related crises are serious clinical problems in childhood and adolescence. Rapid cooling is required to reduce morbidity and mortality. A variety of effective cooling methods exist, and some may interfere with monitoring and resuscitation or are not readily available. We studied in 12 pigtail monkeys the pathophysiology of immersion hyperthermia (42 degrees C) to cardiac arrest (1 min no flow) and CPR plus cooling to normothermia for restoration and stabilization of spontaneous normotension. This was followed by intractable shock and secondary arrest. These studies gave us the opportunity to compare two simple cooling methods applied during and after CPR: group I (n = 6) received application of ice bags to the groins, axillae, and neck. Group II (n = 6) received ice bags plus cold water wetting (sponging) over the entire anterior surface of trunk and extremities, plus fanning. CPR restored spontaneous circulation in four of six in each group, after CPR of 1.5-16 min (NS between groups). Speed of cooling correlated with speed of stabilization of spontaneous normotension. After cardiac arrest and during and after CPR, rectal temperature had declined from a lethal level of 42.2 degrees C to a safe level of 38.5 degrees C within 45 +/- 6 (38-53) min in group I, and within 28 +/- 4 (23-32) min in group II (p less than 0.05). Epidural and esophageal temperatures declined more rapidly than rectal temperature. For critical hyperthermia, we recommend immediate application of ice bags, cold water wetting (sponging), fanning, and head cooling combined when invasive blood cooling (the most effective method) is not immediately available.

Emergency cardiopulmonary bypass for resuscitation from prolonged cardiac arrest

After cardiac arrest (no flow) of more than approximately 5 minutes' duration, standard external cardiopulmonary resuscitation (CPR) basic, advanced, and prolonged life support (BLS, ALS, PLS) do not reliably produce cerebral and coronary perfusion pressures to maintain viability and achieve stable spontaneous normotension; nor do they provide prolonged control over pressure, flow, composition, and temperature of blood. Since these capabilities are often needed to achieve conscious survival, emergency closed-chest cardiopulmonary bypass (CPB) by veno-arterial pumping via oxygenator is presented in this review as a potential addition to ALS-PLS for selected cases. In six dog studies by the Pittsburgh group (n = 221; 1982 through 1988), all 179 dogs that received CPB after prolonged cardiac arrest (no flow) or after CPR (low flow) states had restoration of stable spontaneous circulation. The use of CPB enhanced survival and neurological recovery over those achieved with CPR-ALS attempts only. With CPB and standard intensive care, it was possible to reverse normothermic ventricular fibrillation (VF) cardiac arrest (no flow) of up to 15 minutes and to achieve survival without neurologic deficit; VF of 20 minutes to achieve survival but with neurologic deficit; and VF of 30 minutes to achieve transient restoration of spontaneous circulation followed by secondary cardiac death. CPB could restore stable spontaneous circulation after ice water submersion of up to 90 minutes. Other groups' laboratory and clinical results agree with these findings in general. Clinical feasibility trials are needed to work out logistic problems and to meet clinical challenges. Future possibilities for emergency CPB require further research and development.

Mild cerebral hypothermia during and after cardiac arrest improves neurologic outcome in dogs

We previously found mild hypothermia (34-36 degrees C), induced before cardiac arrest, to improve neurologic outcome. In this study we used a reproducible dog model to evaluate mild hypothermia by head cooling during arrest, continued with systemic cooling (34 degrees C) during recirculation and for 1 h after arrest. In four groups of dogs, ventricular fibrillation (no flow) of 12.5 min at 37.5 degrees C was reversed with cardiopulmonary bypass and defibrillation in less than or equal to 5 min, and followed by controlled ventilation to 20 h and intensive care to 96 h. In Study A we resuscitated with normotension and normal hematocrit; Control Group A-I (n = 12) was maintained normothermic, while Treatment Group A-II (n = 10) was treated with hypothermia. In Study B we resuscitated with hypertension and hemodilution. Control Group B-I (n = 12) was maintained normothermic (6 of 12 were not hemodiluted), while Treatment Group B-II (n = 10) was treated with hypothermia. Best overall performance categories (OPCs) achieved between 24 and 96 h postarrest were in Group A-I: OPC 1 (normal) in 0 of 12 dogs, OPC 2 (moderate disability) in 2, OPC 3 (severe disability) in 7, and OPC 4 (coma) in 3 dogs. In Group A-II, OPC 1 was achieved in 5 of 10 dogs (p less than 0.01), OPC 2 in 4 (p less than 0.001), OPC 3 in 1, and OPC 4 in 0 dogs. In Group B-I, OPC 1 was achieved in 0 of 12 dogs, OPC 2 in 6, OPC 3 in 5, and OPC 4 in 1 dog. In Group B-II, OPC 1 was achieved in 6 of 10 dogs (p less than 0.01), OPC 2 in 4 (p less than 0.05), and OPC 3 or 4 in 0 dogs. Mean neurologic deficit and brain histopathologic damage scores showed similar significant group differences. Morphologic myocardial damage scores were the same in all four groups. We conclude that mild brain cooling during and after insult improves neurologic outcome after cardiac arrest.

Effects of combined superoxide dismutase and deferoxamine on recovery of brainstem auditory evoked potentials and EEG after asphyxial cardiac arrest in dogs

In a randomized study in 23 dogs, we tested the following anti-free radical combination therapy, administered at the beginning of CPR, following apnea-induced cardiac arrest of 7 min: a) ventilation with 100% nitrogen for 30 s to allow the delivery of therapy before oxygen; b) superoxide dismutase (10 mg/kg i.a. followed by 10 mg/kg i.v. over 1 h) to scavenge the superoxide anion radical; and c) deferoxamine (20 mg/kg i.v. over 1 h) to prevent membrane lipid peroxidation. We evaluated the effects of this treatment on the recovery of cardiovascular and cerebral variables short term (6 h) after resuscitation. We reported previously that this treatment mitigated the post-arrest cerebral blood flow changes and enhanced the recovery of somatosensory evoked potentials. This is a secondary report from the same study concerning the effects of this treatment on the recovery of brainstem auditory evoked potentials (BAEPs) and EEG. Compared to control (n = 10), the experimental treatment (n = 10) did not exert a clearcut, significant effect on the recovery of BAEP which normalized in both groups at 1 h post-arrest and enhanced the post-arrest recovery of EEG spectra total power by reducing the post-arrest increase in slow frequency bands. However, the relative distribution of EEG frequencies never recovered the pre-arrest pattern in either group, during the 6 h post-arrest observation period. We conclude that the combination treatment tested enhances the recovery but does not normalize cerebral function post-arrest, suggesting that other treatments should also be entertained or that, indeed, such an insult may not be completely ameliorated by any such treatments.

Glucocorticoid treatment does not improve neurological recovery following cardiac arrest. Brain Resuscitation Clinical Trial I Study Group

Glucocorticoids are commonly given to patients with global brain ischemia, although their efficacy has not been proved. The database of the Brain Resuscitation Clinical Trial I, a multi-institutional study designed to evaluate the effect of thiopental sodium therapy on neurological outcome following brain ischemia, was used for a retrospective review of the effects of glucocorticoid treatment on neurological outcome after global brain ischemia. This study included 262 initially comatose cardiac arrest survivors who made no purposeful response to pain after restoration of spontaneous circulation. The standard treatment protocol left glucocorticoid therapy to the discretion of the hospital investigators. This resulted in four patient groups that received either no, low, medium, or high doses of glucocorticoids in the first 8 hours after arrest. Neurological outcome was scored using a modification of the Glasgow Cerebral Performance Category Scale. None of the steroid regimens statistically improved mean group survival rate or neurological recovery rate over that observed in the group that did not receive steroids. The routine clinical practice of administrating glucocorticoids after global brain ischemia may be associated with serious complications and is not justified.

Effect of excitatory amino acid receptor blocker MK-801 on overall, neurologic, and morphologic outcome after prolonged cardiac arrest in dogs

Excitatory amino acids accumulating in the brain during ischemia may cause selective neuronal damage postischemia. This hypothesis was tested in a series of studies using MK-801, an N-methyl-D-aspartate (NMDA) receptor blocker, in a reproducible outcome model of prolonged cardiac arrest in dogs. After normothermic ventricular fibrillation cardiac arrest, the dogs were resuscitated with closed-chest femoral veno-arterial cardiopulmonary bypass. At 4 h they were separated from bypass, ventilation was controlled for 20 h, and intensive care was continued to 96 h. In Study I, ventricular fibrilation cardiac arrest (no-flow) was 17 min; starting immediately with reperfusion, MK-801 1200 mg/kg (n = 5) or an equal volume of placebo (n = 5) was infused over 12 h in blinded, randomized fashion. In Study II, the duration of the no-flow period was reduced to 15 min, and MK-801 2400 mg.kg-1 (n = 4) or placebo (n = 4) was infused. In Study III, no-flow lasted for 15 min, and MK-801 2400 mg/kg was started 30 min before ventricular fibrillation (n = 4); comparison was with Study II controls. In all three studies, MK-801 plasma concentrations peaked at greater than 50 ng/ml and were 15-30 ng/ml over 12 h. All 22 dogs of experiments within protocol survived with severe brain damage. MK-801 delayed return of pupillary reactivity, EEG activity, consciousness, and respiration, necessitating longer periods of controlled ventilation. Neurologic deficit scores, overall performance categories, and brain and heart morphologic damage scores at 96 h did not differ between placebo and MK-801 pretreatment or post-treatment groups. These negative outcome results after prolonged cardiac arrest do not negate the hyperexcitability hypothesis of selective vulnerability, but suggest the existance of additional mechanisms of secondary brain damage.

Initiation of closed-chest cardiopulmonary resuscitation basic life support. A personal history

Modern external (closed-chest) cardiopulmonary resuscitation (CPR) basic life support (BLS) gives everyone anywhere a chance to initiate the reversal of death from airway obstruction, apnea, or pulselessness. The history of modern CPR has its roots around 1900, but lay dormant for half a century, until in the 1950s several fortunate circumstances merged to allow for documentation of Steps A (airway control by head-tilt and jaw-thrust), B (breathing control by mouth-to-mouth ventilation), and C (circulation control by closed-chest cardiac massage, i.e. chest compressions) and their combination into BLS Steps A-B-C. BLS is only for borderline emergency oxygenation, i.e. Phase I of the life support chain. Both the non-authoritarian environment of the U.S.A. and several role players with keen interest in resuscitation were needed to enable the systematic research (Steps A and B), a chance rediscovery (Step C), and the integration of BLS with advanced life support (ALS, drugs and defibrillation, transferred from open-chest CPR) and brain-oriented prolonged life support (PLS, intensive care) to result in the development of an effective cardiopulmonary-cerebral resuscitation system. A fertile environment led rapidly to the development of resuscitation delivery systems in hospitals and communities. This paper is a story told by one of the role players.

The presenting ECG pattern in survivors of cardiac arrest and its relation to the subsequent long-term survival. Brain Resuscitation Clinical Trial I Study Group

In a prospective multi-center study, 262 patients were given general intensive care therapy following cardiopulmonary resuscitation if they were still comatose and unresponsive to pain 10 min after restored spontaneous circulation. Mortality (mainly cardiac) was 53.4% over the first 10 days, and 49% of the remaining survivors died between 10 days and 6 months. In the subsequent 6 months few patients died. Presenting electrocardiograms (ECG) showed ventricular fibrillation (VF) in 54.2%, asystole in 29.8% and electromechanical dissociation (EMD) in 9.2% of the patients. One-year survival, 14.1% for asystole, 4.2% for EMD and 26.0% for VF and VT (ventricular tachycardia), differed significantly (P less than 0.01). VF/VT patients were older and had more cardiovascular disease. Adjustments of these and other covariates increased the significance of difference between ECG groups. Successful resuscitations from asystole or EMD appeared to be more common than has previously been reported, but this group of patients experienced an extremely high cardiac mortality over the first 6 months following resuscitation.

Effect of cardiac arrest time on cortical cerebral blood flow during subsequent standard external cardiopulmonary resuscitation in rabbits

Standard external cardiopulmonary resuscitation (SECPR) produces high cerebral venous and intracranial pressure peaks, low cerebral perfusion pressure, and low cerebral blood flow (CBF). Cerebral viability seems to require 20% of normal CBF, which SECPR cannot reliably generate. We tested the hypothesis that SECPR can produce adequate CBF if started immediately, but not if started after a long period of cardiac arrest (no flow, stasis). Cardiac arrest times of 1, 3, 5, 7 and 9 min were studied in rabbits. We measured unifocal cortical CBF with H2 clearance curves after saturation with H2 10%, O2 50% and N2O 40% by intermittent positive-pressure ventilation (IPPV). Measurements were made during spontaneous circulation (control condition), and then after resaturation immediately before induction of asystole by KCl i.v., and H2 clearance starting at end of arrest time during SECPR-basic life support with IPPV 100% and manual chest compressions (120/min) during asystole. Control cortical CBF was 30-40 ml/100 g brain per min. During asystole and SECPR, CBF greater than 20% normal was achieved only after no-flow of 1 min. After longer arrest (no-flow) times, CBF was less than 20% normal. Values were near zero after 7 and 9 min of cardiac arrest. Decrease in mean arterial pressures (MAP) produced by SECPR during asystole paralleled CBF values. Thus, the longer the preceding period of stasis, the lower the MAP and CBF generated by SECPR without epinephrine. This effect may be the result of anoxia-induced vasoparalysis and stasis-induced increased blood viscosity.

The physician's responsibility toward hopelessly ill patients. A second look

Physicians have a specific responsibility toward patients who are hopelessly ill, dying, or in the end stages of an incurable disease. In a summary of current practices affecting the care of dying patients, we give particular emphasis to changes that have become commonplace since the early 1980s. Implementation of accepted policies has been deficient in certain areas, including the initiation of timely discussions with patients about dying, the solicitation and execution in advance of their directives for terminal care, the education of medical students and residents, and the formulation of institutional guidelines. The appropriate and, if necessary, aggressive use of pain-relieving substances is recommended, even when such use may result in shortened life. We emphasize the value of a sensitive approach to care--one that is adjusted continually to suit the changing needs of the patient as death approaches. Possible settings for death are reviewed, including the home, the hospital, the intensive care unit, and the nursing home. Finally, we consider the physician's response to the dying patient who is rational and desires suicide or euthanasia.