Targeted Temperature Management for Cardiac Arrest with Nonshockable Rhythm

Targeted Temperature Management in Cardiac Arrest Patients With an Initial Non-Shockable Rhythm: A Systematic Review and Meta-Analysis

BACKGROUND

Targeted temperature management (TTM) is now recommended for patients presenting with an out-of-hospital cardiac arrest. However, there are limited data that support its use in patients with an initial non-shockable rhythm (NSR).

METHODS

A literature search of PubMed/MEDLINE, Cochrane Library, and Embase was conducted by two independent authors for studies that compared TTM along with standard care versus standard care alone in treating cardiac arrest with initial NSR. Outcomes were short-term and long-term survival, and a Cerebral Performance Category (CPC) score of 1 to 2 at the longest follow-up period. The Mantel-Haenszel random-effects model was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Trial sequential analysis (TSA) was performed on the randomized controlled trials (RCTs).

RESULTS

Thirty studies were included in the final analysis: 25 observational and five RCTs, totalling 10,703 patients, 4,023 of whom received TTM and 6,680 received standard care alone. Compared with standard care, patients who presented with an initial NSR cardiac arrest and received TTM (target of 32°C -34°C) had a significantly higher short-term survival (OR 1.44 95% CI 1.15-1.81; P = 0.002), long-term survival (OR 1.52 95% CI 1.03-2.26; P = 0.04), and CPC score of 1 to 2 (OR 1.63 95% CI 1.22-2.17; P = 0.0010). Sensitivity analyses by including only RCTs showed a trend, although not significant, toward better short-term survival (OR 1.25 95% CI 0.82-1.89; P = 0.30), long-term survival (OR 1.15 95% CI 0.80-1.66; P = 0.46), and neurologic outcomes (OR 1.51 95% CI 0.81-2.80; P = 0.19). However, TSA performed on the RCTs revealed that the results were inconclusive.

CONCLUSION

Among patients who survived cardiac arrest with an initial NSR, TTM is associated with a higher rate of survival and favorable neurological outcomes compared with no TTM. However, analyses from the included RCTs did not support this conclusion.

The current temperature: A survey of post-resuscitation care across Australian and New Zealand intensive care units

Aim

Targeted temperature management (TTM) in post-resuscitation care has changed dramatically over the last two decades. However, uptake across Australian and New Zealand (NZ) intensive care units (ICUs) is unclear. We aimed to describe post-resuscitation care in our region, with a focus on TTM, and to gain insights into clinician's opinions about the level of evidence supporting TTM.

Methods

In December 2017, we sent an online survey to 163 ICU medical directors in Australia (n ​= ​141) and NZ (n ​= ​22).

Results

Sixty-one ICU medical directors responded (50 from Australia and 11 from NZ). Two respondents were excluded from analysis as their Private ICUs did not admit post-arrest patients. The majority of remaining respondents stated their ICU followed a post-resuscitation care clinical guideline (n ​= ​41/59, 70%). TTM was used in 57 (of 59, 97%) ICUs, of these only 64% had a specific TTM clinical guideline/policy and there was variation in the types of patients treated, temperatures targeted (range ​= ​33-37.5 ​°C), methods for cooling and duration of cooling (range ​= ​12-72 ​h). The majority of respondents stated that their ICU (n ​= ​45/57, 88%) changed TTM practice following the TTM trial: with 28% targeting temperatures >36 ​°C, and 23 (of 46, 50%) respondents expressed concerns with current level of evidence for TTM. Only 38% of post-resuscitation guidelines included prognostication procedures, few ICUs reported the use of electrophysiological tests.

Conclusions

In Australian and New Zealand ICUs there is widespread variation in post-resuscitation care, including TTM practice and prognostication. There also seems to be concerns with current TTM evidence and recommendations.

Fixed and dilated pupils, not a contraindication for extracorporeal support: a case series

Extracorporeal membrane oxygenation is considered a relative contraindication for patients with severe neurological injury manifested by fixed and dilated pupils. The inability to provide adequate cardiopulmonary support while attempting to treat the underlying neurologic disease results in a fatal outcome. The impairment of cerebral perfusion, compounded by the underlying neurologic condition, results in signs of brainstem dysfunction often equated with a fatal prognosis. As a result, these patients are not considered to be candidates for initiation of extracorporeal membrane oxygenation. We present a case series of three patients with complex neurologic conditions with fixed and dilated pupils, who received extracorporeal membrane oxygenation. All three patients achieved a significant neurologic recovery. Two survived with a cerebral performance category scale of 1, and the third succumbed to multi-organ failure after achieving a Glasgow Coma Scale of 11T. The decision to initiate extracorporeal membrane oxygenation should be based upon the pathophysiology of the underlying neurologic condition and not solely upon isolated clinical findings. Extracorporeal membrane oxygenation use is normally reserved for patients with reversible underlying processes, and a neurologic exam with fixed and dilated pupils is often interpreted as an irreversible neurologic injury. The implementation and success of extracorporeal membrane oxygenation in this patient population require understanding of complex neurologic diseases, rapid recognition of neurocardiogenic shock, and expeditious initiation of cardiopulmonary support in carefully selected patients. The patients described demonstrate that fixed and dilated pupils are not a contraindication for extracorporeal support in select patients.

Association between Cardiac Arrest Time and Favorable Neurological Outcomes in Witnessed Out-of-Hospital Cardiac Arrest Patients Treated with Targeted Temperature Management

BACKGROUND

Patients who achieve a return of spontaneous circulation (ROSC) with prolonged cardiac arrest have been recognized to have a poor prognosis. This might lead to reluctance in the provision of post-resuscitation care. Hence, we evaluated the impact of cardiac arrest time on neurologic outcomes in out-of-hospital cardiac arrest (OHCA) patients.

METHODS

This cross-sectional study used a hospital-based nationwide registry of OHCAs in Korea between 2012 and 2016. All witnessed OHCA patients aged ≥ 15 years and treated with targeted temperature management were included. We collected the time from collapse to sustained ROSC, which was defined as the downtime. The primary outcome was a favorable neurological outcome at hospital discharge. A multiple logistic regression analysis was conducted to determine independent factors for primary outcome in patients with downtime > 30 minutes.

RESULTS

Overall, neurologically favorable outcome rates were 30.5% in 1,963 patients. When the downtime was stratified into categories of 0-10, 11-20, 21-30, 31-40, 41-50, 51-60, and > 60 minutes according to 10-minute intervals, neurologically favorable outcome rates were 58.2%, 52.3%, 37.3%, 24.6%, 14.1%, 17.4%, and 16.7%, respectively (P < 0.001). In patients with downtime > 30 minutes, age 51-70 years (odds ratio [OR], 5.35; 95% confidence interval [CI], 2.50-11.49), age ≤ 50 years (OR, 13.16; 95% CI, 6.06-28.57), shockable rhythm (OR, 3.92; 95% CI, 2.71-5.68), bystander resuscitation (OR, 1.80; 95% CI, 1.27-2.55), cardiac cause (OR, 3.50; 95% CI, 1.69-7.25), percutaneous coronary intervention (OR, 1.82; 95% CI, 1.18-2.81), and downtime ≤ 40 minutes (OR, 2.02; 95% CI, 1.42-2.88) were associated with favorable neurological outcomes.

CONCLUSION

In patients with prolonged downtime, predicting favorable neurologic outcome may be multifactorial. The cutoff value for downtime is not the only determining factor to provide post-resuscitation care.

Therapeutic strategies for ischemia reperfusion injury in emergency medicine

Ischemia reperfusion (IR) injury occurs when blood supply, perfusion, and concomitant reoxygenation is restored to an organ or area following an initial poor blood supply after a critical time period. Ischemia reperfusion injury contributes to mortality and morbidity in many pathological conditions in emergency medicine clinical practice, including trauma, ischemic stroke, myocardial infarction, and post‐cardiac arrest syndrome. The process of IR is multifactorial, and its pathogenesis involves several mechanisms. Reactive oxygen species are considered key molecules in reperfusion injury due to their potent oxidizing and reducing effects that directly damage cellular membranes by lipid peroxidation. In general, IR injury to an individual organ causes various pro‐inflammatory mediators to be released, which could then induce inflammation in remote organs, thereby possibly advancing the dysfunction of multiple organs. In this review, we summarize IR injury in emergency medicine. Potential therapies include pharmacological treatment, ischemic preconditioning, and the use of medical gases or vitamin therapy, which could significantly help experts develop strategies to inhibit IR injury.

Hypothermic to ischemic ratio and mortality in post-cardiac arrest patients

BACKGROUND

We studied the associations between ischemia and hypothermia duration, that is, the hypothermic to ischemic ratio (H/I ratio), with mortality in patients included in a trial on two durations of targeted temperature management (TTM) at 33°C.

METHODS

The TTH48 (NCT01689077) trial compared 24 and 48 hours of TTM in patients after cardiac arrest. We calculated the hypothermia time from return of spontaneous circulation (ROSC) until the patient reached 37°C after TTM and the ischemic time from CA to ROSC. We compared continuous variables with the Mann-Whitney U test. Using COX regression, we studied the independent association of the logarithmically transformed H/I ratio and time to death as well as interaction between time to ROSC, hypothermia duration, and intervention group. We visualized the predictive ability of variables with receiver operating characteristic curve analysis.

RESULTS

Of the 338 patients, 237 (70%) survived for 6 months. The H/I ratio was 155 (IQR 111-238) in survivors and 114 (IQR 80-169) in non-survivors (P < .001). In a Cox regression model including factors associated with outcome in univariate analysis, the logarithmically transformed H/I ratio was a significant predictor of outcome (hazard ratio 0.52 (0.37-0.72, P = .001)). After removing an outlier, we found no interaction between time to ROSC and intervention group (P = .55) or hypothermia duration in quartiles (P = .07) with mortality. There was no significant difference in the area under the curve (AUC) between time to ROSC and H/I ratio (ΔAUC 0.03 95% CI -0.006-0.07, P = .10).

CONCLUSIONS

We did not find any consistent evidence of a modification of the effect of TTM based on ischemia duration.

Resuscitating the Globally Ischemic Brain: TTM and Beyond

Cardiac arrest (CA) afflicts ~ 550,000 people each year in the USA. A small fraction of CA sufferers survive with a majority of these survivors emerging in a comatose state. Many CA survivors suffer devastating global brain injury with some remaining indefinitely in a comatose state. The pathogenesis of global brain injury secondary to CA is complex. Mechanisms of CA-induced brain injury include ischemia, hypoxia, cytotoxicity, inflammation, and ultimately, irreversible neuronal damage. Due to this complexity, it is critical for clinicians to have access as early as possible to quantitative metrics for diagnosing injury severity, accurately predicting outcome, and informing patient care. Current recommendations involve using multiple modalities including clinical exam, electrophysiology, brain imaging, and molecular biomarkers. This multi-faceted approach is designed to improve prognostication to avoid "self-fulfilling" prophecy and early withdrawal of life-sustaining treatments. Incorporation of emerging dynamic monitoring tools such as diffuse optical technologies may provide improved diagnosis and early prognostication to better inform treatment. Currently, targeted temperature management (TTM) is the leading treatment, with the number of patients needed to treat being ~ 6 in order to improve outcome for one patient. Future avenues of treatment, which may potentially be combined with TTM, include pharmacotherapy, perfusion/oxygenation targets, and pre/postconditioning. In this review, we provide a bench to bedside approach to delineate the pathophysiology, prognostication methods, current targeted therapies, and future directions of research surrounding hypoxic-ischemic brain injury (HIBI) secondary to CA.

State-of-the-art considerations in post-arrest care

Cardiac arrest has a high rate of morbidity and mortality. Several advances in post-cardiac arrest management can improve outcome, but are time-dependent, placing the emergency physician in a critical role to both recognize the need for and initiate therapy. We present a novel perspective of both the workup and therapeutic interventions geared toward the emergency physician during the first few hours of care. We describe how the immediate care of a post-cardiac arrest patient is resource intensive and requires simultaneous evaluation for the underlying cause and intensive management to prevent further end organ damage, particularly of the central nervous system. The goal of the initial focused assessment is to rapidly determine if any reversible causes of cardiac arrest are present and to intervene when possible. Interventions performed in this acute period are aimed at preventing additional brain injury through optimizing hemodynamics, providing ventilatory support, and by using therapeutic hypothermia when indicated. After the initial phase of care, disposition is guided by available resources and the clinician's judgment. Transfer to a specialized cardiac arrest center is prudent in centers that do not have significant support or experience in the care of these patients.

Associations between Central Obesity and Outcomes of Adult In-hospital Cardiac Arrest: A Retrospective Cohort Study

To investigate the association between central obesity and outcomes following in-hospital cardiac arrest (IHCA). A single-centred retrospective study was conducted. Adult patients that experienced IHCA during 2006-2015 were screened. Body mass index (BMI) was calculated at hospital admission. Central obesity-related anthropometric parameters were measured by analysing computed tomography images. A total of 648 patients were included, with mean BMI of 23.0 kg/m2. The proportions of BMI-defined obesity in this cohort were underweight (13.1%), normal weight (41.4%), overweight (31.5%) and obesity (14.0%). The mean waist circumference was 85.9 cm with mean waist-to-height ratio (WHtR) of 0.53. The mean sagittal abdominal diameter was 21.2 cm with mean anterior and posterior abdominal subcutaneous adipose tissue (SAT) depths of 1.6 and 2.0 cm, respectively. Multivariate logistic regression analyses indicated BMI of 11.7-23.3 kg/m2 (odds ratio [OR]: 2.53, 95% confidence interval [CI]: 1.10-5.85; p-value = 0.03), WHtR of 0.49-0.59 (OR: 3.45, 95% CI: 1.56-7.65; p-value = 0.002) and anterior abdominal SAT depth <1.9 cm (OR: 2.84, 95% CI: 1.05-7.74; p-value = 0.04) were positively associated with the favourable neurological outcome. Central obesity was associated with poor IHCA outcomes, after adjusting for the effects of BMI.

Acute Cardiovascular Care Association position statement for the diagnosis and treatment of patients with acute myocardial infarction complicated by cardiogenic shock: A document of the Acute Cardiovascular Care Association of the European Society of Cardiology

Most of the guideline-recommended treatment strategies for patients with acute coronary syndromes have been tested in large randomised clinical trials. Still, a major challenge is represented by patients with acute myocardial infarction admitted with impending or established cardiogenic shock. Despite early revascularization the mortality of cardiogenic shock remains high and roughly half of patients do not survive until hospital discharge or 30-day follow-up. However, there is only limited evidence-based scientific knowledge in the cardiogenic shock setting. Therefore, recommendations and actual treatments are often based on retrospective or prospective registry data and extrapolations from randomised clinical trials in acute myocardial infarction patients without cardiogenic shock. This position statement will summarise the current consensus of the diagnosis and treatment of patients with acute myocardial infarction complicated by cardiogenic shock based on current evidence and will provide advice for clinical practice.

Association between health insurance status and transfer of patients with return of spontaneous circulation after out-of-hospital cardiac arrest

AIM

To explore the factors related to the probability of inter-hospital transfer to a heart attack centre in patients with return of spontaneous circulation after out-of-hospital cardiac arrest (OHCA) in the Republic of Korea.

METHODS

This cross-sectional observational study used data from a Korean national emergency medical service OHCA database for cases between 2015 and 2017. Adult OHCA patients with a presumed cardiac origin who initially presented at a non-heart-attack centre were included in the analysis. The main exposure variable was health insurance type (national health insurance versus medical aid), which was used as a proxy measure of individual socioeconomic status. The primary outcome was emergency department disposition (transfer to a heart attack centre versus no transfer). A multivariate logistic analysis using propensity score matching was conducted. We also analysed the associations between patient transfer and neurologic recovery as well as survival to discharge.

RESULTS

Of 7804 eligible OHCA patients, 1804 23.0%) were transferred to a heart attack centre. Patients on medical aid were less likely to be transferred (adjusted odds ratio [OR], 0.75; 95% confidence interval [CI], 0.59-0.95 in a matched cohort) compared with patients with national health insurance. Transfer to a heart attack centre was significantly associated with a lower risk of death (adjusted OR, 0.38; 95% CI, 0.33-0.45) and better neurologic recovery (adjusted OR, 0.46; 95% CI, 0.38-0.56).

CONCLUSION

Socioeconomic status appears likely to influence the probability of transfer to a heart attack centre after resuscitation.

Meta-analysis of targeted temperature management in animal models of cardiac arrest

BACKGROUND

Targeted temperature management (TTM) of 32 to 34 °C has been the standard treatment for out-of-hospital cardiac arrest since clinical trials in 2002 indicated benefit on survival and neurological outcome. In 2013, a clinical trial showed no difference in outcome between TTM of 33 °C and TTM of 36 °C. In this meta-analysis, we investigate the evidence for TTM in animal models of cardiac arrest.

METHODS

We searched PubMed and EMBASE for adult animal studies using TTM as a treatment in different models of cardiac arrest or global brain ischemia which reported neurobehavioural outcome, brain histology or mortality. We used a random effects model to calculate estimates of efficacy and assessed risk of bias using an adapted eight-item version of the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES) quality checklist. We also used a scoring system based on the recommendations of the Stroke Treatment Academic Industry Roundtable (STAIR), to assess the scope of testing in the field. Included studies which investigated a post-ischemic induction of TTM had their treatment regimens characterized with regard to depth, duration and time to treatment and scored against the modified STAIR criteria.

RESULTS

The initial and updated search generated 17809 studies after duplicate removal. One hundred eighty-one studies met the inclusion criteria, including data from 1,787, 6,495 and 2,945 animals for neurobehavioural, histological and mortality outcomes, respectively. TTM was favoured compared to control for all outcomes. TTM was beneficial using short and prolonged cooling, deep and moderate temperature reduction, and early and delayed time to treatment. Median [IQR] study quality was 4 [3 to 6]. Eighteen studies checked seven or more of the eight CAMARADES quality items. There was no clear correlation between study quality and efficacy for any outcome. STAIR analysis identified 102 studies investigating post-ischemic induction of TTM, comprising 147 different treatment regimens of TTM. Only 2 and 8 out of 147 regimens investigated comorbid and gyrencephalic animals, respectively.

CONCLUSIONS

TTM is beneficial under most experimental conditions in animal models of cardiac arrest or global brain ischemia. However, research on gyrencephalic species and especially comorbid animals is uncommon and a possible translational gap. Also, low study quality suggests risk of bias within studies. Future animal research should focus on mimicking the clinical scenario and employ similar rigour in trial design to that of modern clinical trials.

Left Ventricular Function During Epinephrine Stimulation and Hypothermia: Effects at Spontaneous and Paced Heart Rates in a Porcine Model

Postcardiac arrest patients treated with hypothermia, frequently require vasopressors and inotropic medication. The aim of this experimental study was to investigate the effect of epinephrine on left ventricular (LV) function during hypothermia. In an open-chest porcine model, seven animals were equipped with LV micromanometer and epicardial ultrasound transducers to provide LV pressure, Tau, and wall thickness and thickening velocities in systole (S') and early diastole (e'). Arterial, central venous, and pulmonal artery pressures were recorded. Cardiac output (CO) was measured by transit-time flow probe on the ascending aorta. Hypothermia was induced using a cooling catheter through the femoral vein. Pacemaker leads were attached to the right atrium for pacing. LV volumes were obtained by two-dimensional echocardiography. Measurements were made at normothermia (38°C) and hypothermia (33°C), without and with epinephrine infusion (0.03 μg/kg/min), at spontaneous and paced heart rates (HRs) 120 and 140 beats/min. Hypothermia reduced LV stroke volume (SV). Epinephrine during hypothermia increased the SV with reduced end-systolic volumes. LV dP/dt_max and wall-thickening velocity increased. During normothermia, epinephrine increased CO mainly due to accelerated HR, but during hypothermia, the increased CO resulted from augmented SV and, to a lesser degree, elevated HR. The incomplete relaxation and shortened diastolic filling time and the following reduction in SV seen in hypothermic animals, was repealed by epinephrine. The CO remained elevated also due to a shortened systolic duration, which gave time for complete relaxation during higher HRs. Epinephrine infusion improved systolic and diastolic function during hypothermia, and thereby reversed the effects induced by hypothermia considerably. Epinephrine augmented CO at hypothermia through increases in both SV and HR, in contrast to a mainly HR-dependent effect during normothermia. Systolic duration was shortened, which gave sufficient diastolic duration for complete relaxation. This allowed diastolic filling and maintained CO at elevated HRs.

High Quality Targeted Temperature Management (TTM) After Cardiac Arrest

Targeted temperature management (TTM) is a complex intervention used with the aim of minimizing post-anoxic injury and improving neurological outcome after cardiac arrest. There is large variability in the devices used to achieve cooling and in protocols (e.g., for induction, target temperature, maintenance, rewarming, sedation, management of post-TTM fever). This variability can explain the limited benefits of TTM that have sometimes been reported. We therefore propose the concept of “high-quality TTM” as a way to increase the effectiveness of TTM and standardize its use in future interventional studies.

Nanotherapeutic modulation of excitotoxicity and oxidative stress in acute brain injury

Excitotoxicity is a primary pathological process that occurs during stroke, traumatic brain injury (TBI), and global brain ischemia such as perinatal asphyxia. Excitotoxicity is triggered by an overabundance of excitatory neurotransmitters within the synapse, causing a detrimental cascade of excessive sodium and calcium influx, generation of reactive oxygen species, mitochondrial damage, and ultimately cell death. There are multiple potential points of intervention to combat excitotoxicity and downstream oxidative stress, yet there are currently no therapeutics clinically approved for this specific purpose. For a therapeutic to be effective against excitotoxicity, the therapeutic must accumulate at the disease site at the appropriate concentration at the right time. Nanotechnology can provide benefits for therapeutic delivery, including overcoming physiological obstacles such as the blood–brain barrier, protect cargo from degradation, and provide controlled release of a drug. This review evaluates the use of nano-based therapeutics to combat excitotoxicity in stroke, TBI, and hypoxia–ischemia with an emphasis on mitigating oxidative stress, and consideration of the path forward toward clinical translation.

Selective retrograde cerebral cooling in complete cerebral circulatory arrest

BACKGROUND AND PURPOSE:

Cerebral hypothermia is a known neuroprotectant with promising applications in the treatment of ischemic events. Although systemic cooling is standard in post-cardiac arrest care, the deleterious effects of whole-body cooling have precluded it from translation into a viable treatment option for acute ischemic stroke (AIS). Selective cerebral cooling has been proposed as a method to minimize these risks while granting the neuroprotection of therapeutic hypothermia in AIS.

METHODS:

In a porcine model (n = 3), the efficacy of selective retrograde cerebral cooling through the internal jugular vein was evaluated in the setting of complete cerebral circulatory arrest. Furthermore, a novel endovascular device and cooling system enabling selective retrograde cerebral cooling were studied in a normothermic perfused cadaver.

RESULTS AND CONCLUSION:

Neurologic assessment of animals receiving this therapy reflected substantial neuroprotection in animals undergoing both 15 min and 30 min of otherwise catastrophic complete cerebral circulatory arrest. The novel endovascular device and cooling system were validated in human anatomy, demonstrating successful cerebral cooling, and feasibility of this mechanism of selective retrograde cerebral cooling.

Temporal trends in the use of targeted temperature management after cardiac arrest and association with outcome: insights from the Paris Sudden Death Expertise Centre

Purpose

Recent doubts regarding the efficacy may have resulted in a loss of interest for targeted temperature management (TTM) in comatose cardiac arrest (CA) patients, with uncertain consequences on outcome. We aimed to identify a change in TTM use and to assess the relationship between this change and neurological outcome.

Methods

We used Utstein data prospectively collected in the Sudden Death Expertise Center (SDEC) registry (capturing CA data from all secondary and tertiary hospitals located in the Great Paris area, France) between May 2011 and December 2017. All cases of non-traumatic OHCA patients with stable return of spontaneous circulation (ROSC) were included. After adjustment for potential confounders, we assessed the relationship between changes over time in the use of TTM and neurological recovery at discharge using the Cerebral Performance Categories (CPC) scale.

Results

Between May 2011 and December 2017, 3925 patients were retained in the analysis, of whom 1847 (47%) received TTM. The rate of good neurological outcome at discharge (CPC 1 or 2) was higher in TTM patients as compared with no TTM (33% vs 15%, P < 0.001). Gender, age, and location of CA did not change over the years. Bystander CPR increased from 55% in 2011 to 73% in 2017 (P < 0.001) and patients with a no-flow time longer than 3 min decreased from 53 to 38% (P < 0.001). The use of TTM decreased from 55% in 2011 to 37% in 2017 (P < 0.001). Meanwhile, the rate of patients with good neurological recovery remained stable (19 to 23%, P = 0.76). After adjustment, year of CA occurrence was not associated with outcome.

Conclusions

We report a progressive decrease in the use of TTM in post-cardiac arrest patients over the recent years. During this period, neurological outcome remained stable, despite an increase in bystander-initiated resuscitation and a decrease in “no flow” duration.

Therapeutic hypothermia and Type II errors: Do not throw out the baby with the ice water

After initial enthusiasm for mild therapeutic hypothermia (TH) treatment after brain injuries, including global cerebral ischemia after cardiac arrest, subsequent trials suggested similar benefit using only targeted temperature management (TTM), with fewer side effects. Globally, effective treatment of brain ischemia with TH has declined. Recent data suggest, however, that TH to 33°C may be superior to TTM. We review the background and rationale underlying TH and TTM. We present previously published data from our own laboratory that confirms TH to 33°C provides superior brain cytoprotection, compared to 35°C or 37°C, over a range of delays to treatment and several durations of TH. We illustrate that the treatment effect size of either or 35 is superior to 37, but the effect size difference between 33 and 35, although significant, is small. We estimate that to demonstrate the superiority of TTM over TH, a clinical trial would need between 3,000 and 9,000 patients depending on the desired treatment effect size. Our review and our own data suggest that TH to 33°C is superior to TTM to 36°C, but an extremely large clinical trial would be needed to demonstrate the difference.