Cardiac Arrest, Mild Therapeutic Hypothermia, and Unanticipated Cerebral Recovery

Enhancing cardiac arrest survival with extracorporeal cardiopulmonary resuscitation: insights into the process of death

Extracorporeal cardiopulmonary resuscitation (ECPR) is an emerging method of cardiopulmonary resuscitation to improve outcomes from cardiac arrest. This approach targets patients with out-of-hospital cardiac arrest previously unresponsive and refractory to standard treatment, combining approximately 1 h of standard CPR followed by venoarterial extracorporeal membrane oxygenation (VA-ECMO) and coronary artery revascularization. Despite its relatively new emergence for the treatment of cardiac arrest, the approach is grounded in a vast body of preclinical and clinical data that demonstrate significantly improved survival and neurological outcomes despite unprecedented, prolonged periods of CPR. In this review, we detail the principles behind VA-ECMO-facilitated resuscitation, contemporary clinical approaches with outcomes, and address the emerging new understanding of the process of death and capability for neurological recovery.

The current significance of the FOUR score: A systematic review and critical analysis of the literature

BACKGROUND

The Full Outline of Un-Responsiveness Score (FOURs) is a scale for clinical assessment of consciousness that was introduced to overcome disadvantages of the widely accepted Glasgow Coma Scale (GCS).

OBJECTIVE

To carry out a systematic review and critical analysis of the available literature on the clinical application of FOURs and perform a comparison to GCS, in terms of reliability and predictive value.

METHODS

Initial search retrieved a total of 147 papers. After applying strict inclusion criteria and further article selection to overcome data heterogeneity, a statistical comparison of inter-rater reliability, in-hospital mortality and long-term outcome prediction between the two scales in the adult and pediatric population was done.

RESULTS

Even though FOURs is more complicated than GCS, its application remains quite simple. Its reliability, validity and predictive value have been supported by an increasing number of studies, especially in critical care. A statistically significant difference (p = .034) in predicting in-hospital mortality in adults, in favor of FOURs when compared to GCS, was found. However, whether it poses a clinically significant advantage in detecting patients' deterioration and outcome prediction, compared to other scaling systems, remains unclear.

CONCLUSIONS

Further studies are needed to discern the FOURs' clinical usefulness, especially in patients in non-critical condition, with milder disorders of consciousness.

Performing the Brain Death Examination and the Declaration of Pediatric Brain Death

Declaration of brain death is a clinical diagnosis made by the absence of neurological function in a comatose patient secondary to a known irreversible cause. Brain death determination is not an infrequent process in pediatric intensive care units. It is important that pediatric intensive care providers understand the definition of brain death and intensivists are able to implement brain death testing. The following is a narration detailing the process of brain death determination by physical examination. First, the prerequisites that determine patients' eligibility for brain death testing will be outlined. Next, each part of the physical exam, including the apnea test, will be described in detail. Finally, how the declaration of brain death is made is stated. In addition, special considerations and ancillary testing will be briefly highlighted.

Blood pressure and neuropsychological test performance in healthy postmenopausal women

PURPOSE

To study the association between blood pressure and neuropsychological test performance in healthy postmenopausal women.

METHODS

Data from 88 healthy postmenopausal women aged 46-73 years, who were not experiencing hot flashes, and who had participated in a prior drug trial, were analyzed to find whether baseline blood pressure was associated with impaired performance on neuropsychological testing done at 3 follow-up visits separated by 4 weeks. Factor analysis was used to reduce the dimensions of neuropsychological test performance. Mixed linear modeling was used to evaluate the association between baseline blood pressure and repeatedly measured neuropsychological test performance at follow-up in a complete case analysis (n=53). In a sensitivity analysis (n=88), multiple-imputation using the Markov Chain Monte Carlo method was used to account for missing data (blood pressure results) for some visits.

RESULTS

The variables recording neuropsychological test performance were reduced to two main factors (Factor 1=selective attention; Factor 2=complex processing). In the complete case analysis, the association between a 20-mmHg increase in diastolic blood pressure and Factor 1 remained statistically significant after adjusting for potential confounders, before adjusting for systolic blood pressure (slope=0.60; 95%CI=0.04,1.16), and after adjusting for systolic blood pressure (slope=0.76; 95%CI=0.06, 1.47). The positive slopes indicated an increase in the time spent performing a given task (i.e., a decrease in neuropsychological test performance). No other significant associations were found between systolic blood pressure and either factor. The results did not materially change after applying the multiple-imputation method.

CONCLUSIONS

An increase in diastolic blood pressure was associated with a decrease in neuropsychological test performance among older healthy postmenopausal women experiencing hot flashes.

Early neurologic examination is not reliable for prognostication in post-cardiac arrest patients who undergo therapeutic hypothermia

BACKGROUND

Recent advances in post-cardiac arrest (CA) care including therapeutic hypothermia (TH) have improved survival and favorable neurologic outcomes for survivors of CA. Survivors often present with deep coma and lack of brainstem reflexes, which are generally associated with adverse outcomes in many disease processes. Little is known regarding the role of initial emergency department (ED) neurological examination and its potential for prognostication.

OBJECTIVES

The purpose of this study is to determine if components of a standardized neurologic examination are reliable prognosticators in patients recently resuscitated from CA. We hypothesize that lack of neurologic function does not reliably predict an adverse outcome and, therefore, should not be used to determine eligibility for TH.

METHODS

A standardized neurologic examination was performed in the ED on a prospective, convenience cohort of post-CA patients presenting to a CA resuscitation center who would undergo a comprehensive postarrest care pathway that included TH. Data such as prior sedation or active neuromuscular blockade were documented to evaluate for the presence of possible confounders. Examination findings were then compared with hospital survival and neurologic outcome at discharge as defined by the cerebral performance category (CPC) score as documented in the institutional TH registry.

RESULTS

Forty-nine subjects were enrolled, most of whom presented comatose with a Glasgow Coma Scale of 3 (n=41, 83.7%). Nineteen subjects (38.8%) had absence of all examination findings, of which 4 of 19 (21.1%) survived to hospital discharge. Of those with at least 1 positive examination finding, 13 of 30 subjects (43.3%) survived to hospital discharge. Subgroup analysis showed that 9 of the 19 patients with absence of brainstem reflexes did not have evidence of active neuromuscular blockade at the time of the examination; 2 of 9 (22.1%) survived to hospital discharge. Eight of these subjects in this group had not received any prior sedation; 1 of 8 (12.5%) survived to hospital discharge. Only 1 of the 17 subjects who survived was discharged with poor neurologic function with a CPC score=3, whereas all others who survived had good neurologic function, CPC score=1.

CONCLUSION

In this cohort of patients treated in a comprehensive postarrest care pathway that included TH, absence of neurologic function on initial ED presentation was not reliable for prognostication. Given these findings, clinicians should refrain from using the initial ED neurological examination to guide the aggressiveness of care or in counseling of family members regarding anticipated outcome.

Automated quantitative pupillometry for the prognostication of coma after cardiac arrest

BACKGROUND

Sedation and therapeutic hypothermia (TH) delay neurological responses and might reduce the accuracy of clinical examination to predict outcome after cardiac arrest (CA). We examined the accuracy of quantitative pupillary light reactivity (PLR), using an automated infrared pupillometry, to predict outcome of post-CA coma in comparison to standard PLR, EEG, and somato-sensory evoked potentials (SSEP).

METHODS

We prospectively studied over a 1-year period (June 2012-June 2013) 50 consecutive comatose CA patients treated with TH (33 °C, 24 h). Quantitative PLR (expressed as the % of pupillary response to a calibrated light stimulus) and standard PLR were measured at day 1 (TH and sedation; on average 16 h after CA) and day 2 (normothermia, off sedation: on average 46 h after CA). Neurological outcome was assessed at 90 days with Cerebral Performance Categories (CPC), dichotomized as good (CPC 1-2) versus poor (CPC 3-5). Predictive performance was analyzed using area under the ROC curves (AUC).

RESULTS

Patients with good outcome [n = 23 (46 %)] had higher quantitative PLR than those with poor outcome [n = 27; 16 (range 9-23) vs. 10 (1-30) % at day 1, and 20 (13-39) vs. 11 (1-55) % at day 2, both p < 0.001]. Best cut-off for outcome prediction of quantitative PLR was <13 %. The AUC to predict poor outcome was higher for quantitative than for standard PLR at both time points (day 1, 0.79 vs. 0.56, p = 0.005; day 2, 0.81 vs. 0.64, p = 0.006). Prognostic accuracy of quantitative PLR was comparable to that of EEG and SSEP (0.81 vs. 0.80 and 0.73, respectively, both p > 0.20).

CONCLUSIONS

Quantitative PLR is more accurate than standard PLR in predicting outcome of post-anoxic coma, irrespective of temperature and sedation, and has comparable prognostic accuracy than EEG and SSEP.

ED prognostication of comatose cardiac arrest patients undergoing therapeutic hypothermia is unreliable

BACKGROUND

Therapeutic hypothermia (TH) improves patient survival with good neurologic outcome after cardiac arrest. The value of early clinician prognostication in the emergency department (ED) has not been studied in this patient population.

OBJECTIVE

To determine if physicians can accurately predict survival and neurologic outcome at hospital discharge of resuscitated, comatose out-of-hospital cardiac arrest (OHCA) patients treated in a post-cardiac arrest clinical pathway that included TH.

METHODS

This was a prospective, observational study conducted at a tertiary referral center. Participants were physicians involved in the resuscitation of OHCA patients treated with a clinical pathway that included TH. Immediately after patient resuscitation in the ED, physicians recorded their prediction of patient survival and neurologic outcome on a standardized questionnaire. Neurologic outcome was assessed by the cerebral performance category.

RESULTS

Forty-two physicians completed questionnaires on 17 patients enrolled from October 2009 to March 2010. Sensitivity and specificity of physician prediction of patient survival were 0.67 (95% confidence interval [CI], 0.45-0.83) and 0.82 (95% CI, 0.59-0.94), respectively, with an area under the curve of 0.74 (95% CI, 0.61-0.88), a positive likelihood ratio (+LR) of 3.72 (95% CI, 1.30-11.02), and a -LR of 0.40 (95% CI, 0.21-0.77). Sensitivity and specificity of physician prediction of good neurologic outcome were 0.40 (95% CI, 0.20-0.64) and 0.69 (95% CI, 0.50-0.84), respectively, with an area under the curve of 0.55 (95% CI, 0.39-0.70), a +LR of 1.29 (95% CI, 0.56-3.03), and a -LR of 0.87 (95% CI, 0.53-1.41).

CONCLUSIONS

Physicians poorly prognosticate both survival and neurologic outcome in comatose OHCA patients undergoing TH. Premature prognostication in the ED is unreliable and should be avoided.

Brain Death: Assessment, Controversy, and Confounding Factors

When brain injury is refractory to aggressive management and is considered nonsurvivable, with loss of consciousness and brain stem reflexes, a brain death protocol may be initiated to determine death according to neurological criteria. Clinical evaluation typically entails 2 consecutive formal neurological examinations to document total loss of consciousness and absence of brain stem reflexes and then apnea testing to evaluate carbon dioxide unresponsiveness within the brain stem. Confounding factors such as use of therapeutic hypothermia, high-dose metabolic suppression, and movements associated with complex spinal reflexes, fasciculations, or cardiogenic ventilator autotriggering may delay initiation or completion of brain death protocols. Neurodiagnostic studies such as 4-vessel cerebral angiography can rapidly document absence of blood flow to the brain and decrease intervals between onset of terminal brain stem herniation and formal declaration of death by neurological criteria. Intracranial pathophysiology leading to brain death must be considered along with clinical assessment, patterns of vital signs, and relevant diagnostic studies.

Timing of neuroprognostication in postcardiac arrest therapeutic hypothermia*

OBJECTIVE

Early assessment of neurologic recovery is often challenging in survivors of cardiac arrest. Further, little is known about when to assess neurologic status in comatose, postarrest patients receiving therapeutic hypothermia. We sought to evaluate timing of prognostication in cardiac arrest survivors who received therapeutic hypothermia.

DESIGN

A retrospective chart review of consecutive postarrest patients receiving therapeutic hypothermia (protocol: 24-hr maintenance at target temperature followed by rewarming over 8 hrs). Data were abstracted from the medical chart, including documentation during the first 96 hrs post arrest of "poor" prognosis, diagnostic tests for neuroprognostication, consultations used for determination of prognosis, and outcome at discharge.

SETTING

Two academic urban emergency departments.

PATIENTS

A total of 55 consecutive patients who underwent therapeutic hypothermia were reviewed between September 2005 and April 2009.

INTERVENTION

None.

RESULTS

Of our cohort of comatose postarrest patients, 59% (29 of 49) were male, and the mean age was 56 ± 16 yrs. Chart documentation of "poor" or "grave" prognosis occurred "early": during induction, maintenance of cooling, rewarming, or within 15 hrs after normothermia in 57% (28 of 49) of cases. Of patients with early documentation of poor prognosis, 25% (seven of 28) had care withdrawn within 72 hrs post arrest, and 21% (six of 28) survived to discharge with favorable neurologic recovery. In the first 96 hrs post arrest: 88% (43 of 49) of patients received a head computed tomography, 90% (44 of 49) received electroencephalography, 2% (one of 49) received somatosensory evoked potential testing, and 71% (35 of 49) received neurology consultation.

CONCLUSIONS

Documentation of "poor prognosis" occurred during therapeutic hypothermia in more than half of patients in our cohort. Premature documentation of poor prognosis may contribute to early decisions to withdraw care. Future guidelines should address when to best prognosticate in postarrest patients receiving therapeutic hypothermia.

Optimizing community resources to address sudden cardiac death

The "chain of survival" (early access, early cardiopulmonary resuscitation, early defibrillation, and early advanced care) defines the proven interventions necessary for successful resuscitation and survival of patients with cardiac arrest. Low survival rates from cardiac arrest are not due to lack of understanding of effective interventions, but instead are due to weak links in the chain of survival and the inability of communities to make sure these links function in an efficient, timely, and coordinated fashion. This article reviews how quality is defined for each link, how communities can strengthen each link, and how communities can forge a strong relationship between each link. By optimizing local leadership and stakeholder collaboration, communities have the potential to vastly improve outcomes from this devastating disease.

Implementing the 2005 American Heart Association Guidelines improves outcomes after out-of-hospital cardiac arrest

OBJECTIVE

The purpose of the study was to determine whether applying highly recommended changes in the 2005 American Heart Association (AHA) Guidelines would improve outcomes after out-of-hospital cardiac arrest.

BACKGROUND

In 2005, AHA recommended multiple ways to improve circulation during cardiopulmonary resuscitation (CPR).

METHODS

Conglomerate quality assurance data were analyzed during prospective implementation of the 2005 AHA Guidelines in five emergency medical services (EMS) systems. All EMS personnel were trained in the key new aspects of the 2005 AHA Guidelines, including use of an impedance threshold device. The primary outcome was survival to hospital discharge. Secondary outcomes were return of spontaneous circulation (ROSC), survival by initial cardiac arrest rhythm, and the cerebral performance category (CPC) score at hospital discharge.

RESULTS

There were 1,605 patients in the intervention group and 1,641 patients in the control group. Demographics, the rate of bystander CPR, and time from the 911 call for help to arrival of EMS personnel were similar between groups. Survival to hospital discharge was 10.1% in the control group versus 13.1% in the intervention group (P = .007). For patients with a presenting rhythm of ventricular fibrillation/ventricular tachycardia, survival to discharge was 20% in controls versus 32.3% in the intervention group (P <.001). Survival to discharge with a CPC classification of 1 or 2 was 33.3% (10/30) in the control versus 59.6% (31/52) in the intervention group (P = .038).

CONCLUSIONS

Compared with controls, patients with out-of-hospital cardiac arrest treated with a renewed emphasis on improved circulation during CPR had significantly higher neurologically intact hospital discharge rates.

Regional Systems of Care for Out-of-Hospital Cardiac Arrest

Out-of-hospital cardiac arrest continues to be an important public health problem, with large and important regional variations in outcomes. Survival rates vary widely among patients treated with out-of-hospital cardiac arrest by emergency medical services and among patients transported to the hospital after return of spontaneous circulation. Most regions lack a well-coordinated approach to post–cardiac arrest care. Effective hospital-based interventions for out-of-hospital cardiac arrest exist but are used infrequently. Barriers to implementation of these interventions include lack of knowledge, experience, personnel, resources, and infrastructure. A well-defined relationship between an increased volume of patients or procedures and better outcomes among individual providers and hospitals has been observed for several other clinical disorders. Regional systems of care have improved provider experience and patient outcomes for those with ST-elevation myocardial infarction and life-threatening traumatic injury. This statement describes the rationale for regional systems of care for patients resuscitated from cardiac arrest and the preliminary recommended elements of such systems. Many more people could potentially survive out-of-hospital cardiac arrest if regional systems of cardiac resuscitation were established. A national process is necessary to develop and implement evidence-based guidelines for such systems that must include standards for the categorization, verification, and designation of components of such systems. The time to do so is now.

Optimizing Community Resources to Address Sudden Cardiac Death

The "chain of survival" (early access, early cardiopulmonary resuscitation, early defibrillation, and early advanced care) defines the proven interventions necessary for successful resuscitation and survival of patients with cardiac arrest. Low survival rates from cardiac arrest are not due to lack of understanding of effective interventions, but instead are due to weak links in the chain of survival and the inability of communities to make sure these links function in an efficient, timely, and coordinated fashion. This article reviews how quality is defined for each link, how communities can strengthen each link, and how communities can forge a strong relationship between each link. By optimizing local leadership and stakeholder collaboration, communities have the potential to vastly improve outcomes from this devastating disease.

Coma due to cardiac arrest: prognosis and contemporary treatment

Approximately 80% of patients who are successfully resuscitated from cardiac arrest do not regain consciousness immediately after return of spontaneous circulation, and may remain in a coma for hours or weeks, or even be in a persistent vegetative state. Recent investigations have focused on the identification of early clinical characteristics and biomarkers that can reliably predict emergence from coma in those who survive, and on therapies that might improve neurologic outcome from the ischemic brain injury that can be caused by cardiac arrest.

From laboratory science to six emergency medical services systems: New understanding of the physiology of cardiopulmonary resuscitation increases survival rates after cardiac arrest

OBJECTIVE

The purpose of this study is to: 1) describe a newly mechanism of blood flow to the brain during cardiopulmonary resuscitation using the impedance threshold device in a piglet model of cardiac arrest, and 2) describe the survival benefits in humans of applying all of the highly recommended changes in the 2005 guidelines related to increasing circulation during cardiopulmonary resuscitation, including use of the impedance threshold device, from six emergency medical services systems in the United States.

DESIGN

Animal studies prospective trial with each piglet serving as its own control. Historical controls were used for the human studies.

SUBJECTS

Piglets and patients with out-of-hospital cardiac arrest.

INTERVENTIONS

Piglets (10-12 kg) were treated with an active (n = 9) or sham (n = 9) impedance threshold device after 6 mins of ventricular fibrillation. Humans were treated with cardiopulmonary resuscitation per the American Heart Association 2005 guidelines and the impedance threshold device.

MEASUREMENTS AND MAIN RESULTS

ANIMALS

The primary endpoint in the piglet study was carotid blood flow which increased from 59 mL/min without an impedance threshold device to 91 mL/min (p = 0.017) with impedance threshold device use. Airway pressures during the chest recoil phase decreased from -0.46 mm Hg to -2.59 mm Hg (p = 0.0006) with the active impedance threshold device. Intracranial pressure decreased more rapidly and to a greater degree during the decompression phase of cardiopulmonary resuscitation with the active impedance threshold device. Humans: Conglomerate quality assurance data were analyzed from six emergency medical services systems in the United States serving a population of approximately 3 million people. There were 920 patients treated for cardiac arrest after implementation of the 2005 American Heart Association guidelines, including impedance threshold device use, and 1750 patients in the control group during the year before implementation. Demographics were similar between the two groups. Survival to hospital discharge was 9.3% in the control group versus 13.6% in the intervention group. The odds ratio, 95% confidence interval, and p value were 1.54 (1.19-1.99) and p = 0.0008, respectively. This survival advantage was conferred to patients with a presenting cardiac arrest rhythm of ventricular fibrillation (28.5% vs. 18.0%, p = 0.0008).

CONCLUSIONS

Use of the impedance threshold device in piglets increased carotid blood flow and coronary and cerebral perfusion pressures and reduced intracranial pressure during the decompression phase of cardiopulmonary resuscitation at a faster rate than controls, resulting in a longer duration of time when intracranial pressures are at their nadir. Patients in six emergency medical services systems treated with the impedance threshold device together with the renewed emphasis on more compressions, fewer ventilations, and complete chest wall recoil had a nearly 50% increase in survival rates after out-of-hospital cardiac arrest compared with historical controls.