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

Cerebral oximetry: a developing tool for monitoring cerebral oxygenation during cardiopulmonary resuscitation

Despite improvements in cardiopulmonary resuscitation (CPR), survival and neurologic recovery after cardiac arrest remain very poor because of the impact of severe ischemia and subsequent reperfusion injury. As the likelihood of survival and favorable neurologic outcome decreases with increasing severity of ischemia during CPR, developing methods to measure the magnitude of ischemia during resuscitation, particularly cerebral ischemia, is critical for improving overall outcomes. Cerebral oximetry, which measures regional cerebral oxygen saturation (rSO₂ ) by near-infrared spectroscopy, has emerged as a potentially beneficial marker of cerebral ischemia during CPR. In numerous preclinical and clinical studies, higher rSO₂ during CPR has been associated with improved cardiac arrest survival and neurologic outcome. In this narrative review, we summarize the scientific rationale and validation of cerebral oximetry across populations and pathophysiologic states, discuss the evidence surrounding its use to predict return of spontaneous circulation, rearrest, and neurologic outcome, and provide suggestions for incorporation of cerebral oximetry into CPR practice.

Monitoring the Relationship Between Changes in Cerebral Oxygenation and Electroencephalography Patterns During Cardiopulmonary Resuscitation: A Feasibility Study

OBJECTIVES

To date, no studies have examined real-time electroencephalography and cerebral oximetry monitoring during cardiopulmonary resuscitation as markers of the magnitude of global ischemia. We therefore sought to assess the feasibility of combining cerebral oximetry and electroencephalography in patients undergoing cardiopulmonary resuscitation and further to evaluate the electroencephalography patterns during cardiopulmonary resuscitation and their relationship with cerebral oxygenation as measured by cerebral oximetry.

DESIGN

Extended case series of in-hospital and out-of-hospital cardiac arrest subjects.

SETTING

Tertiary Medical Center.

PATIENTS

Inclusion criteria: Convenience sample of 16 patients undergoing cardiopulmonary resuscitation during working hours between March 2014 and March 2015, greater than or equal to 18 years. A portable electroencephalography (Legacy; SedLine, Masimo, Irvine, CA) and cerebral oximetry (Equanox 7600; Nonin Medical, Plymouth, MN) system was used to measure cerebral resuscitation quality.

INTERVENTIONS

Real-time regional cerebral oxygen saturation and electroencephalography readings were observed during cardiopulmonary resuscitation. The regional cerebral oxygen saturation values and electroencephalography patterns were not used to manage patients by clinical staff.

MEASUREMENTS AND MAIN RESULTS

In total, 428 electroencephalography images from 16 subjects were gathered; 40.7% (n = 174/428) were artifactual, therefore 59.3% (n = 254/428) were interpretable. All 16 subjects had interpretable images. Interpretable versus noninterpretable images were not related to a function of time or duration of cardiopulmonary resuscitation but to artifacts that were introduced to the raw data such as diaphoresis, muscle movement, or electrical interference. Interpretable data were able to be obtained immediately after application of the electrode strip. Seven distinct electroencephalography patterns were identified. Voltage suppression was commonest and seen during 78% of overall cardiopulmonary resuscitation time and in 15 of 16 subjects at some point during their cardiopulmonary resuscitation. Other observed patterns and their relative prevalence in relation to overall cardiopulmonary resuscitation time were theta background activity 8%, delta background activity 5%, bi frontotemporal periodic discharge 4%, burst suppression 2%, spike and wave 2%, and rhythmic delta activity 1%. Eight of 16 subjects had greater than one interpretable pattern. At regional cerebral oxygen saturation levels less than or equal to 19%, the observed electroencephalography pattern was exclusively voltage suppression. Delta background activity was only observed at regional cerebral oxygen saturation levels greater than 40%. The remaining patterns were observed throughout regional cerebral oxygen saturation categories above a threshold of 20%.

CONCLUSIONS

Real-time monitoring of cerebral oxygenation and function during cardiac arrest resuscitation is feasible. Although voltage suppression is the commonest electroencephalography pattern, other distinct patterns exist that may correlate with the quality of cerebral resuscitation and oxygen delivery.

Protective effects of ghrelin on brain mitochondria after cardiac arrest and resuscitation

Mitochondrial dysfunction plays a critical role in brain injury after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Our recent study demonstrated that ghrelin protected against post-resuscitation brain injury with an elevated expression of mitochondrial uncoupling protein 2 (UCP2). However, the effects of ghrelin on mitochondrial dysfunction after CA are not clear. In the present study, the protective role of ghrelin was evaluated on mitochondrial dysfunction and the subsequent damage induced by CA in rats. In addition, mitochondrial unfolded protein response (UPRmt), an intrinsic cytoprotective pathway, was observed at the same time. Either vehicle (saline) or ghrelin (80 μg/kg) was injected blindly immediately after 6 min of CA and successful resuscitation. Neurological deficit was evaluated 6 h after CA and then cortex was collected for assessments. As a result, we found that ghrelin significantly improved the neurological deficit score in rats after CA. The functional analysis of isolated mitochondria revealed that ghrelin improved the mitochondrial ATP synthesis capacity and significantly reduced the reactive oxygen species (ROS) leakage after 6 h of CA. Concomitantly, we observed an increased ATP level and an attenuated oxidative stress in ghrelin treated animals. Moreover, ghrelin markedly improved the mitochondrial morphology compared with the vehicle animals. Further research revealed that ghrelin treatment significantly activated the UPRmt as demonstrated by the increased expression of heat shock protein 60 (HSP60), heat shock protein 10 (HSP10), caseinolytic protease 1 (CLPP1), and high-temperature requirement protein A2 (HTRA2). Our results suggest that ghrelin protected against cerebral mitochondria dysfunction after CA and the mechanism may involve a UPRmt pathway.

Prognostication in Anoxic Brain Injury

Cardiac arrest is a common cause of coma with frequent poor outcomes. Palliative medicine teams are often called upon to discuss the scope of treatment and future care in cases of anoxic brain injury. Understanding prognostic tools in this setting would help medical teams communicate more effectively with patients’ families and caregivers and may promote improved quality of life overall. This article reviews multiple tools that are useful in determining outcomes in the setting of postarrest anoxic brain injury.

Prehospital removal improves neurological outcomes in elderly patient with foreign body airway obstruction

OBJECTIVE

In Japan, the number of patients with foreign body airway obstruction by food is rapidly increasing with the increase in the population of the elderly and a leading cause of unexpected death. This study aimed to determine the factors that influence prognosis of these patients.

METHODS

This is a retrospective single institutional study. A total of 155 patients were included. We collected the variables from the medical records and analyzed them to determine the factors associated with patient outcome. Patient outcomes were evaluated using cerebral performance categories (CPCs) when patients were discharged or transferred to other hospitals. A favorable outcome was defined as CPC 1 or 2, and an unfavorable outcome was defined as CPC 3, 4, or 5.

RESULTS

A higher proportion of patients with favorable outcomes than unfavorable outcomes had a witness present at the accident scene (68.8% vs. 44.7%, P=0.0154). Patients whose foreign body were removed by a bystander at the accident scene had a significantly high rate of favorable outcome than those whose foreign body were removed by emergency medical technicians or emergency physician at the scene (73.7% vs. 31.8%, P<0.0075) and at the hospital after transfer (73.7% vs. 9.6%, P<0.0001).

CONCLUSIONS

The presence of a witness to the aspiration and removal of the airway obstruction of patients by bystanders at the accident scene improves outcomes in patients with foreign body airway obstruction. When airway obstruction occurs, bystanders should remove foreign bodies immediately.

MRI default mode network connectivity is associated with functional outcome after cardiopulmonary arrest

BACKGROUND

We hypothesized that the degree of preserved functional connectivity within the DMN during the first week after cardiopulmonary arrest (CPA) would be associated with functional outcome at hospital discharge.

METHODS

Initially comatose CPA survivors with indeterminate prognosis at 72 h were enrolled. Seventeen CPA subjects between 4 and 7 days after CPA and 17 matched controls were studied with task-free fMRI. Independent component analysis was performed to delineate the DMN. Connectivity strength in the DMN was compared between CPA subjects and controls, as well as between CPA subjects with good outcome (discharge Cerebral Performance Category or CPC 1-2) and those with bad outcome (CPC 3-5). The relationship between connectivity strength in the posterior cingulate cortex (PCC) and precuneus (PC) within the DMN with discharge CPC was evaluated using linear regression.

RESULTS

Compared to controls, CPA subjects had significantly lower connectivity strength in subregions of the DMN, the PCC and PC (p < 0.0001). Furthermore, connectivity strength in the PCC and PC was greater in CPA subjects with good outcome (n = 8) than those with bad outcome (n = 9) (p < 0.003). Among CPA subjects, the connectivity strength in the PCC and PC showed strong linear correlations with the discharge CPC (p < 0.005).

CONCLUSIONS

Among initially comatose CPA survivors with indeterminate prognosis, task-free fMRI demonstrated graded disruption of DMN connectivity, especially in those with bad outcomes. If confirmed, connectivity strength in the PC/PCC may provide a clinically useful prognostic marker for functional recovery after CPA.

Value of post-resuscitation electrocardiogram in the diagnosis of acute myocardial infarction in out-of-hospital cardiac arrest patients

BACKGROUND

Diagnosis of acute myocardial infarction (AMI) in out-of-hospital cardiac arrest (OHCA) patients is important because immediate coronary angiography with coronary angioplasty could improve outcome in this setting. However, the value of acute post-resuscitation electrocardiographic (ECG) data for the detection of AMI is debatable.

METHODS

We assessed the diagnostic characteristics of post-resuscitation ECG changes in a retrospective single centre study evaluating several ECG criteria of selection of patients undergoing AMI, in order to improve sensitivity, even at the expense of specificity. Immediate post resuscitation coronary angiogram was performed in all patients. AMI was defined angiographically using coronary flow and plaque morphology criteria.

RESULTS

We included 165 consecutive patients aged 56 (IQR 48-67) with sustained return of spontaneous circulation after OHCA between 2002 and 2008. 84 patients had shockable, 73 non-shockable and 8 unknown initial rhythm; 36% of the patients had an AMI. ST-segment elevation predicted AMI with 88% sensitivity and 84% specificity. The criterion including ST-segment elevation and/or depression had 95% sensitivity and 62% specificity. The combined criterion including ST-segment elevation and/or depression, and/or non-specific wide QRS complex and/or left bundle branch block provided a sensitivity and negative predictive value of 100%, a specificity of 46% and a positive predictive value of 52%.

CONCLUSION

In patients with OHCA without obvious non-cardiac causes, selection for coronary angiogram based on the combined criterion would detect all AMI and avoid the performance of the procedure in 30% of the patients, in whom coronary angiogram did not have a therapeutic role.

Quantitative assessment of somatosensory-evoked potentials after cardiac arrest in rats: prognostication of functional outcomes

OBJECTIVE

High incidence of poor neurologic sequelae after resuscitation from cardiac arrest underscores the need for objective electrophysiological markers for assessment and prognosis. This study aims to develop a novel marker based on somatosensory evoked potentials (SSEPs). Normal SSEPs involve thalamocortical circuits suggested to play a role in arousal. Due to the vulnerability of these circuits to hypoxic-ischemic insults, we hypothesize that quantitative SSEP markers may indicate future neurologic status.

DESIGN

Laboratory investigation.

SETTING

University Medical School and Animal Research Facility.

SUBJECTS

: Sixteen adult male Wistar rats.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

SSEPs were recorded during baseline, during the first 4 hrs, and at 24, 48, and 72 hrs postasphyxia from animals subjected to asphyxia-induced cardiac arrest for 7 or 9 mins (n = 8/group). Functional evaluation was performed using the Neurologic Deficit Score (NDS). For quantitative analysis, the phase space representation of the SSEPs-a plot of the signal vs. its slope-was used to compute the phase space area bounded by the waveforms recorded after injury and recovery. Phase space areas during the first 85-190 mins postasphyxia were significantly different between rats with good (72 hr NDS >or=50) and poor (72 hr NDS <50) outcomes (p = .02). Phase space area not only had a high outcome prediction accuracy (80-93%, p < .05) during 85-190 mins postasphyxia but also offered 78% sensitivity to good outcomes without compromising specificity (83-100%). A very early peak of SSEPs that precedes the primary somatosensory response was found to have a modest correlation with the 72 hr NDS subscores for thalamic and brainstem function (p = .066) and not with sensory-motor function (p = .30).

CONCLUSIONS

Phase space area, a quantitative measure of the entire SSEP morphology, was shown to robustly track neurologic recovery after cardiac arrest. SSEPs are among the most reliable predictors of poor outcome after cardiac arrest; however, phase space area values early after resuscitation can enhance the ability to prognosticate not only poor but also good long-term neurologic outcomes.

Cardiac arrest resuscitation: neurologic prognostication and brain death

PURPOSE OF REVIEW

Persistent coma after cardiac arrest is a source of great emotional and financial cost to grieving family members in particular and the healthcare system in general. Neurologic prognostication helps guide appropriate discussions between family members and healthcare providers. Recent advances in therapeutic care increase the challenges, both medical and financial, on local practitioners.

RECENT FINDINGS

Evidence-based reviews by prestigious associations add additional support and guidance to the practitioner who must guide family members in this very difficult decision process. Therapeutic hypothermia may alter findings, thus skewing the prognostic abilities of many accepted methodologies. This study reviews the usefulness of clinical examination, electrophysiologic studies, biochemical markers, and imaging modalities in predicting poor neurologic recovery in comatose survivors after cardiac arrest resuscitation. Some data from studies of therapeutic hypothermia are presented.

SUMMARY

Evidence-based tests of prognostication for neurologic outcome after cardiac arrest are presented. A review of the practice of withdrawal of life-sustaining therapies and the diagnosis of brain death is also provided. The reader is cautioned that most prognostic studies do not include possible amelioration with the use of therapeutic hypothermia.

Management of brain injury after resuscitation from cardiac arrest

The devastating neurologic injury in survivors of cardiac arrest has been recognized since the development of modern resuscitation techniques. After numerous failed clinical trials, two trials showed that induced mild hypothermia can ameliorate brain injury and improve survival and functional neurologic outcome in comatose survivors of out-of-hospital cardiac arrest. This article provides a comprehensive review of the advances in the care of brain injury after cardiac arrest, with updates on the process of prognostication, the use of therapeutic hypothermia and adjunctive intensive care unit care for cardiac arrest survivors.

Biochemical markers (NSE, S-100, IL-8) as predictors of neurological outcome in patients after cardiac arrest and return of spontaneous circulation

Predicting the neurological outcome after resuscitation and a return of spontaneous circulation of resuscitated patients still remains a difficult issue. Over the past decade numerous studies have been elaborated to provide the physician with tools to assess as early as possible the neurological outcome of patients with cardiac arrest and return of spontaneous circulation and to decide about further therapeutic management. We summarise the most important ones, giving special focus to three biochemical markers (neuron specific enolase, a protein soluble in 100% ammonium sulfate and interleukin-8), which, when combined with standard neuro-functional and imaging techniques, can serve as potent predictors of neurological outcome in these patients. Despite current limitations about the prognostic significance of these markers - their inferior sensitivity, the different cut-off levels used by several investigators and their variable unequal rise over time - they can give useful information about short and long-term neurological outcome. A comprehensive set of clinical, electrophysiological, biochemical and imaging measures, obtained in a uniform manner in a cohort of patients without limitations in care, could provide a more objective set of comprehensive prognostic indicators.

Intensive care for brain injury after cardiac arrest: therapeutic hypothermia and related neuroprotective strategies

Neurologic injury is the predominant cause of poor functional outcome in patients who are resuscitated from cardiac arrest. The management of these patients in the ICU can be challenging because of the paucity of effective therapies and lack of readily available diagnostic and prognostic tools. After several decades of failed pharmacologic neuroprotection trials, recent and well-designed randomized trials showed that therapeutic hypothermia is an effective neuroprotective measure in comatose survivors of cardiac arrest. Therapeutic hypothermia has been recommended by the International Liaison Committee on Resuscitation and has been incorporated in the American Heart Association CPR Guidelines. The American Academy of Neurology recently enhanced the delivery of care in survivors of cardiac arrest by providing evidence-based practice parameters on the prediction of poor outcome in comatose survivors of cardiac arrest, based on clinical evaluation and diagnostic tests. This article discusses these advances and their potential impact on the care provided in the ICU.

Brain arrest neurological outcome scale (BrANOS): predicting mortality and severe disability following cardiac arrest

BACKGROUND

To create a predictive scale of neurological outcome following cardiac arrest (CA) that incorporates radiological and clinical markers of brain injury.

METHODS AND RESULTS

Brain arrest neurologic outcome scale (BrANOS) is a prospective 16-point scale. It consisted of three variables: (1) duration of arrest (DAR), (2) reversed Glasgow coma scale (GCS), and (3) Hounsfield unit (HU) ratio on non-contrast CT scan of the head. Reversed GCS score was defined as 15-GCS (best GCS in the first 24 h). HU ratio was defined as the density ratio of the caudate nucleus over the posterior limb of the internal capsule measured on unenhanced CT scan of the brain. We identified 32 comatose patients who had: (1) CT scan performed within 48 h of event; (2) no previous history of either coma, severe head trauma, cardiac arrest or stroke. Primary outcome was defined as alive or dead. Secondary outcome was the Glasgow outcome score recorded on discharge. Patient demographics were collated from retrospective chart review. Patients' mean age was 63 +/- 3 years (mean +/- S.E.M.); 44% were females. Mortality rate was 81%. Mean DAR was 21 +/- 2 min. Survivors had a significantly lower BrANOS score (8 +/- 2 points) compared to non-survivors (13 +/- 1) (P = 0.006). BrANOS was a strong predictor of mortality alone (ROC = 0.86) and mortality with severe disability combined (ROC = 0.9). The scale had a 100% specificity and positive predictive value.

CONCLUSIONS

BrANOS is a reliable predictor of neurological outcome following CA. It is the first scale to incorporate clinical and radiological markers of brain injury.

S-100 protein as early predictor of regaining consciousness after out of hospital cardiac arrest

BACKGROUND AND PURPOSE

Patients resuscitated from cardiac arrest (CA) have a high mortality rate. Prognostic evaluation based on clinical observations is uncertain and would benefit from the use of biochemical markers of hypoxic brain damage. The purpose of the study was to validate the use of the serum astroglial protein S-100 levels at admission with regard to regaining consciousness after out of hospital CA.

METHODS

Fifty-eight patients resuscitated from out-of-hospital CA were followed up until they regained consciousness or until their death or permanent vegetative state occurred. Serum samples for measurement of S-100, using an immunoradiometric assay, were obtained at admission.

RESULTS

At admission, the mean value+/-standard error of the mean of serum S-100 protein was significantly higher in patients who did not regain consciousness compared with patients who regained consciousness, respectively 4.66+/-0.61 microg/l and 0.84+/-0.21 microg/l. A serum S-100 value of >0.7 microg/l at admission was found to be a predictor that consciousness would not be regained, with a specificity of 85%, a sensitivity of 66.6%, a positive predictive value of 84%, a negative predictive value of 78% and an accuracy of 77.6%.

CONCLUSIONS

Serum S-100 protein at admission gives reliable and independent information concerning the short term neurological outcome after resuscitation; and could be a good marker of brain cell damage.

Resuscitation in the hospital: relationship of year and rhythm to outcome

OBJECTIVE

determine the frequency of initial rhythms in in-hospital resuscitation and examine its relationship to survival. Assess changes in outcome over time.

METHODS

retrospective cohort (registry) including all admissions to the Medical Center of Central Georgia in which a resuscitation was attempted between 1 January, 1987 and 31 December, 1996.

RESULTS

the registry includes 3327 admissions in which 3926 resuscitations were attempted. Only the first event is reported. There were 961 hospital survivors. Survival increased from 24.2% in 1987 to 33.4% in 1996 (chi(2)=39.0, df=1, P<0.0001). Survival was affected strongly by initial rhythm (chi(2)=420.0, df=1, P<0.0001) and decreased from 63.2% for supraventricular tachycardia (SVT) to 55.3% for ventricular tachycardia (VT), 51.0% for perfusing rhythms (PER), 34.8% for ventricular fibrillation (VF), 14.3% for pulseless electrical activity (PEA) and 10.0% for asystole (ASYS). PEA was the most frequent rhythm (1180 cases) followed by perfusing (963), asystole (580), VF (459), VT (94) and SVT (38).

DISCUSSION

the powerful effect of initial rhythm on survival has been reported in pre-hospital and in-hospital resuscitation. VF is considered the dominant rhythm and generally accounts for the most survivors. We report good outcome for each; however, VF represents only 13.8% of events and 16.7% of survivors. PEA accounts for more survivors (169) than does VF (160). Our improved outcome is partially explained by changes in rhythms, but other institutional variables need to be identified to fully explain the results. Further studies are needed to see if our findings can be sustained or replicated.

Standard and higher doses of atropine in a canine model of pulseless electrical activity

OBJECTIVE

To determine whether standard or increased doses of atropine improve the return of spontaneous circulation (ROSC) rate in a canine model of pulseless electrical activity (PEA).

METHODS

A prospective, controlled, blinded laboratory investigation was performed using an asphyxial canine cardiac arrest model. After the production of asphyxial PEA, 75 dogs remained in untreated PEA for 10 minutes and then were randomized to receive placebo (group 1) or one of four doses of atropine (group 2, 0.04 mg/kg; group 3, 0.1 mg/kg; group 4, 0.2 mg/kg; group 5, 0.4 mg/kg). All the animals received mechanical external CPR and epinephrine (0.02 mg/kg every 3 minutes) throughout resuscitation.

RESULTS

The ROSC rates were not significantly different between the groups (group 1, 73%; group 2, 67%; group 3, 40%; group 4, 47%; group 5, 27%; p = 0.06). The heart rates and hemodynamics during resuscitation were not significantly different between the groups.

CONCLUSION

In this canine model of asphyxial PEA cardiac arrest, standard-dose atropine did not improve ROSC rates, compared with placebo. Increasing doses of atropine tended to decrease ROSC rates, compared with placebo and standard-dose atropine.

Combined continuous monitoring of systemic and cerebral oxygen metabolism after cardiac arrest

Cerebral oxygenation was assessed in 8 patients in cardiac arrest during the 24 h after resuscitation, by continuous fiber-optic monitoring of jugular bulb venous oxygen saturation (SjO2), in conjunction with continuous monitoring of mixed venous oxygen saturation (SvO2). Three patients survived and 5 died. SjO2 and SvO2 patterns were compared between surviving and non-surviving patients with regard to their prognostic and therapeutic implications. The mean SjO2 of the survivors (67%) was significantly lower than that of the non-survivors (80%) (P < 0.001), whereas the corresponding SvO2 value was higher in the survivor group (74%) than in the non-survivor group (64%) (P < 0.001). Three of the non-survivors died of brain death within 5 days after resuscitation, and then the others died of respiratory or cardiovascular failure without recovering from deep coma. The high SjO2 of the non-survivors suggests that an inability of damaged neurons to use oxygen may be an indicator of poor neurological outcome in resuscitated patients after cardiac arrest. When SjO2 was < 45%, Sv-O2 was extremely low, reflecting cardiovascular failure after resuscitation. SjO2 may thus serve to warn of deterioration in cardiopulmonary function and serve as a predictor of outcome in cardiac arrest survivors.

Resuscitation time limits in experimental pulseless electrical activity cardiac arrest using cardiopulmonary bypass

STUDY OBJECTIVE

The objective of this study was to determine the time limits of resuscitation following increasing intervals of untreated pulseless electrical activity using cardiopulmonary bypass as the resuscitation tool.

DESIGN

Prospective controlled laboratory investigation using a canine model of pulseless electrical activity.

SUBJECTS

20 mechanically ventilated mongrel dogs of either sex under Halothane anesthesia.

INTERVENTIONS

Pulseless electrical activity was produced by clamping the endotracheal tube. The ECG and hemodynamics were monitored until loss of pressure fluctuations by aortic catheter. Animals were then randomized to remain in untreated pulseless electrical activity for 10 min (Group I), 15 min (Group II) or 20 min (Group III). Following each interval, resuscitation was begun using fixed-flow closed-chest cardiopulmonary bypass (50 ml/kg/min) and an epinephrine infusion (4 micrograms/kg/min). Cardiopulmonary bypass was continued for 30 min or until return of spontaneous circulation. Following return of spontaneous circulation, animals were weaned from bypass and observed for 1 h.

MEASUREMENTS AND MAIN RESULTS

Return of spontaneous circulation was achieved in 100% (7/7) Group I, 50% (3/6) Group II and 29% (2/7) Group III animals (P < or = 0.02, Group I vs. Group III). One-hour survival was achieved in 71% (5/7) Group I, 33% (1/3) Group II and 0% (0/2) Group III animals (P > 0.05). Coronary perfusion pressure, bypass flow and arterial blood gases during reperfusion were similar between groups.

CONCLUSION

Cardiopulmonary bypass is effective at restoring spontaneous circulation when used early in asphyxial pulseless electrical activity cardiac arrest. Cardiopulmonary bypass is less effective when used after 15 min of pulseless electrical activity with no survivors following 20 min of arrest.

Assessment of neurological prognosis in comatose survivors of cardiac arrest. BRCT I Study Group

When a patient resuscitated from cardiac arrest remains unconscious the clinician would like to have a reliable early method for predicting the outcome. The objective of our study was to predict cerebral outcome after cardiac arrest by clinical neurological examination. The data were drawn from an international multicentre controlled clinical trial of thiopentone. Twelve hospitals in nine countries took part. 262 comatose cardiac arrest survivors were followed up for one year. These patients were given advanced life support (American Heart Association guidelines) followed by intensive care to a standardised protocol. Glasgow and Glasgow-Pittsburgh coma scores and their constituent signs were recorded at fixed times. Outcome was taken to be the best cerebral performance at any time during follow-up, and for that purpose we used cerebral performance categories (CPC 1-5) of the Glasgow outcome categories. A poor outcome (CPC 3-5) could be predicted immediately after reperfusion (at entry into the study) with an accuracy ranging from 52% to 84% for various signs and scores. On the third day it was possible to identify severely disabled or permanently comatose survivors without false predictions using both coma scores and several of their constituent variables. The best predictor was absence of motor response to pain. This modelling exercise now needs to be repeated on a new series of patients but the results do suggest that, after 3 days, stringent ethical criteria can be met and used in decision-making about termination of care in comatose cardiac arrest survivors.

Effects of vagal tone on resuscitation from experimental electromechanical dissociation

STUDY OBJECTIVE

To determine if complete loss of vagal tone improves the return of spontaneous circulation rate in a canine model of electromechanical dissociation cardiac arrest.

DESIGN

Prospective, controlled laboratory investigation using an asphyxial canine cardiac arrest model randomized to receive bilateral cervical vagotomy or no vagotomy.

INTERVENTIONS

After the production of asphyxial electromechanical dissociation arrest, 16 mongrel dogs remained in untreated electromechanical dissociation for ten minutes and then were randomized to receive bilateral cervical vagotomy or no vagotomy. All animals received standard external CPR and epinephrine (0.02 mg/kg every five minutes) throughout resuscitation.

MEASUREMENTS AND MAIN RESULTS

Return of spontaneous circulation was achieved in 13% (one of eight) of no vagotomy and 75% (six of eight) of vagotomy animals (P = .02). Survival to one hour was achieved in 100% (one of one) of no vagotomy and 83% (five of six) of vagotomy animals (P = NS). The hemodynamic and arterial blood gas values at five, ten, and 15 minutes into resuscitation were not significantly different between groups.

CONCLUSION

In this canine model of asphyxial electromechanical dissociation cardiac arrest, surgical vagotomy and complete loss of vagal tone improved the rate of return of spontaneous circulation.

Rhythm changes during resuscitation from ventricular fibrillation

Defibrillation of patients with primary ventricular fibrillation (VF) results in a variety of rhythm changes. We analysed these changes in rhythm in 200 patients, using the American Heart Association's recommendation of two defibrillations prior to drug therapy. Sixty-three (31.5%) patients were immediate survivors with 38 (19%) being discharged from hospital alive. There was no difference between the age of immediate survivors (66.5 years, S.D. = 11.2) and non-survivors (68.3 years, S.D. = 13.7, P = 0.37). Immediate survivors were significantly more likely to be discharged alive from hospital if they were younger (70.0 years, S.D. 8.5 vs. 62.1 years, S.D. 15.8, P = 0.014). Increasing delays to the initiation of basic life support (CPR) and to defibrillation were associated with significantly less likelihood of cardioversion to sinus rhythm (P < 0.005 and P < 0.002, respectively). Those patients who stayed in VF were not more likely to be defibrillated into asystole or electro-mechanical dissociation. Seventeen percent (34) of patients were defibrillated to sinus rhythm after the first defibrillation and 14% (19) after the second, with similar hospital discharge rates (62% and 58%, respectively). Sixty percent (32) of patients in sinus rhythm, after two defibrillations, were discharged alive, compared to only 4% (6) of those patients not in sinus rhythm after two defibrillations. Our data provide new information on rhythm changes during resuscitation and supports the need for the earliest possible initiation of basic life support and defibrillation to improve survival from cardiac arrest due to ventricular fibrillation.

Brain-oriented intensive care after resuscitation from cardiac arrest

The 'chain-of-survival' concept has gained general acceptance in the care of cardiac arrest victims. Most standards and guidelines for cardiopulmonary resuscitation, however, focus on the initial links in the chain. We consider appropriate in-hospital care for the survivors a logical extension of the chain of survival. In recent years extensive research activity has probed the pathophysiology and pharmacology of postischemic reperfusion. The present review discusses the current understanding of mechanisms for cerebral damage following global ischemia. Promising pharmacological principles for protection or resuscitation from cerebral ischemia are reviewed. None of them are considered ready for clinical application. Clinical guidelines are proposed, based on the reviewed data and previously published clinical observations. Cornerstones of the proposed brain-oriented intensive care protocol are: (1) hemodynamic monitoring and meticulous treatment of circulatory disturbances, (2) controlled ventilation providing normoventilation and normoxia to all comatose patients, (3) avoiding hyperglycemia and hyperthermia in comatose patients, (4) adequate analgesia and sedation, tempered by the understanding that oversedation impedes neurological evaluation without promoting recovery. An accurate prognosis can usually be made 48-72 h after resuscitation. This permits reevaluation and assignment to an appropriate level of continued hospital care.

Use of cardiopulmonary bypass, high-dose epinephrine, and standard-dose epinephrine in resuscitation from post-countershock electromechanical dissociation

STUDY OBJECTIVE

To determine the effects of cardiopulmonary bypass with standard-dose epinephrine, high-dose epinephrine, and standard-dose epinephrine on perfusion pressures, myocardial blood flow, and resuscitation from post-countershock electromechanical dissociation.

DESIGN

Prospective, controlled laboratory investigation using a canine cardiac arrest model randomized to receive one of three resuscitation therapies.

INTERVENTIONS

After the production of post-countershock electromechanical dissociation, 25 animals received ten minutes of basic CPR and were randomized to receive cardiopulmonary bypass with standard-dose epinephrine, high-dose epinephrine, or standard-dose epinephrine.

MEASUREMENTS AND MAIN RESULTS

Myocardial blood flow was measured using a colored microsphere technique at baseline, during basic CPR, and after intervention. Immediate and two-hour resuscitation rates were determined for each group. Return of spontaneous circulation was achieved in eight of eight cardiopulmonary bypass with standard-dose epinephrine compared with four of eight high-dose epinephrine and three of eight standard-dose epinephrine animals (P less than .04). One animal was resuscitated with CPR alone and was excluded. Survival to two hours was achieved in five of eight cardiopulmonary bypass with standard-dose epinephrine, four of eight high-dose epinephrine, and three of eight standard-dose epinephrine animals (NS). Coronary perfusion pressure increased significantly in the cardiopulmonary bypass with standard-dose epinephrine group when compared with the other groups (cardiopulmonary bypass with standard-dose epinephrine, 76 +/- 45 mm Hg; high-dose epinephrine, 24 +/- 12 mm Hg; standard-dose epinephrine, 3 +/- 14 mm Hg; P less than .005). Myocardial blood flow was higher in cardiopulmonary bypass with standard-dose epinephrine and high-dose epinephrine animals compared with standard-dose epinephrine animals but did not reach statistical significance. Cardiac output increased during cardiopulmonary bypass with standard-dose epinephrine (P = .001) and standard-dose epinephrine (NS) compared with basic CPR but decreased after epinephrine administration in the high-dose epinephrine group (NS).

CONCLUSION

Resuscitation from electromechanical dissociation was improved with cardiopulmonary bypass and epinephrine compared with high-dose epinephrine or standard-dose epinephrine alone. However, there was no difference in survival between groups. Cardiopulmonary bypass with standard-dose epinephrine resulted in higher cardiac output, coronary perfusion pressure, and a trend toward higher myocardial blood flow. A short period of cardiopulmonary bypass with epinephrine after prolonged post-countershock electromechanical dissociation cardiac arrest can re-establish sufficient circulation to effect successful early resuscitation.

Prediction of hospital discharge in immediate survivors of ventricular fibrillation or asystole

Survival from ventricular fibrillation and asystole is influenced by variables measured during resuscitation that affect both immediate survival and discharge from hospital. These variables have been used to develop a formula to calculate an individuals chances of immediate survival and hospital discharge. It has allowed this heterogenous group to be subdivided into groups which can be compared both within and between institutions for the purposes of audit and evaluation of resuscitation protocols. This study evaluates the addition of clinical parameters to the prognostic index. One hundred twelve immediate survivors of ventricular fibrillation or asystole were examined immediately after resuscitation and clinical parameters measured and recorded. At the same time parameters previously described were recorded. The increase in the numbers of survivors improved the reliability (area under the receiver operator curve (ROC) improved from 0.79 to 0.83) of the index for predicting hospital discharge. Addition of the clinical variables of conscious state, respiratory state, blood pressure and pulse rate improved the prognostic index further to an ROC area of 0.86. This ensures that the predictive power of the new index is now highly reliable for predicting hospital discharge after successful resuscitation from ventricular fibrillation and asystole.

Comparison of standard external CPR, open-chest CPR, and cardiopulmonary bypass in a canine myocardial infarct model

STUDY OBJECTIVES

After cardiac arrest, open-chest CPR (OCCPR) and cardiopulmonary bypass (CPB) have demonstrated higher resuscitation rates when compared individually with standard external CPR (SECPR). We compared all three techniques in a canine myocardial infarct ventricular fibrillation model.

TYPE OF PARTICIPANTS

Twenty-six mongrel dogs were block-randomized to receive SECPR and advanced life support (nine), CPB (nine), or OCCPR (eight).

DESIGN AND INTERVENTIONS

All dogs received left anterior descending coronary artery occlusion followed by four minutes of ventricular fibrillation without CPR and eight minutes of Thumper CPR. At 12 minutes, dogs received one of three resuscitation techniques. After resuscitation, all animals received four hours of intensive care. Animals that were resuscitated had histochemical determination of ischemic and necrotic myocardial areas.

MEASUREMENTS

Intravascular pressures were measured and coronary perfusion pressure was calculated during baseline, cardiac arrest, resuscitation, and postresuscitation periods. Percent necrotic myocardium, percent ischemic myocardium, and necrotic-to-ischemic ratios were determined for resuscitated animals. Epinephrine dosage and number of countershocks were determined for each group.

MAIN RESULTS

Nine of nine CPB and six of nine OCCPR, compared with two of eight SECPR animals, were resuscitated (P less than .01). Three of nine CPB and OCCPR and two of eight SECPR dogs survived to four hours (P = NS). Coronary perfusion pressure two minutes after institution of technique was significantly higher with CPB (75 +/- 37 mm Hg) and OCCPR (56 +/- 31 mm Hg) than in SECPR animals (16 +/- 16 mm Hg, P less than .04). Epinephrine required for resuscitation was significantly less with CPB (0.10 +/- 0.02 mg/kg) than for SECPR (0.28 +/- 0.11 mg/kg, P less than .002). The ratio of necrotic to ischemic myocardium at four hours was significantly lower with CPB (0.15 +/- 0.31) and OCCPR (0.39 +/- 0.25) than for SECPR (1.16 +/- 0.31, P less than .02).

CONCLUSION

OCCPR and CPB produce higher coronary perfusion pressures and improved resuscitation rates from ventricular fibrillation when compared with SECPR in this canine myocardial infarct cardiac arrest model. CPB and OCCPR yielded similar resuscitation results, although less epinephrine was required with CPB.

Cause of death in unsuccessful prehospital resuscitation

During 1987-1988, prehospital resuscitation was unsuccessful in 204 of 381 patients who suffered a witnessed cardiac arrest due to presumed coronary heart disease in Helsinki. The cause of death was verified by autopsy in 80 (39%) of the 204 patients. Their cause of death could not be estimated on the basis of previous patient history, and their autopsy diagnoses were then related to the initial cardiac rhythm recorded at the scene. At autopsy, coronary heart disease was considered to have been the cause of death in 78% of the patients with ventricular fibrillation, in 43% of the patients with electromechanical dissociation (EMD), and in 60% of the patients in asystole. Cardiac tamponade or massive pulmonary embolism was the cause of death in 15 of the 28 patients with EMD who underwent autopsy. These findings support previously noted relationships between some causes of cardiac arrest and the initial cardiac rhythm, and also in prehospital cardiac arrest patients with unsuccessful resuscitation.

Initiation of resuscitation in patients with prehospital bradyasystolic cardiac arrest in Helsinki

The factors influencing the decision to initiate resuscitation in prehospital cardiac arrest patients encountered in bradyasystole due to presumed heart disease were studied. For this purpose, the characteristics and circumstances of arrest of the patients encountered in asystole and electromechanical dissociation, seen by a physician-staffed prehospital emergency care unit in a tiered emergency medical system, were reviewed. During the study period, resuscitation was initiated in 83 bradyasytolic patients. The characteristics of these patients were compared with those of 72 patients in asystole or electromechanical dissociation declared dead on the scene without resuscitation. The presence of EMD was the most important factor influencing the decision to resuscitate (P less than 0.001), even if the arrest was unwitnessed, while the patient's age was of less importance. For the patients with a witnessed arrest, the delay before treatment was initiated also affected the decision. Successful resuscitation and survival of the patients was similar to earlier reports. The results provide guidelines in the decision making of initiation of resuscitation when developing our emergency care system into one with non-physicians as advanced life support providers.