Effect of Therapeutic Hypothermia on Survival to Hospital Discharge in Out-of-hospital Cardiac Arrest Secondary to Nonshockable Rhythms

Temperature Control in Acute Brain Injury: An Update

Temperature control in severe acute brain injury (SABI) is a key component of acute management. This manuscript delves into the complex role of temperature management in SABI, encompassing conditions like traumatic brain injury (TBI), acute ischemic stroke (AIS), intracerebral hemorrhage (ICH), aneurysmal subarachnoid hemorrhage (aSAH), and hypoxemic/ischemic brain injury following cardiac arrest. Fever is a common complication in SABI and is linked to worse neurological outcomes due to increased inflammatory responses and intracranial pressure (ICP). Temperature management, particularly hypothermic temperature control (HTC), appears to mitigate these adverse effects primarily by reducing cerebral metabolic demand and dampening inflammatory pathways. However, the effectiveness of HTC varies across different SABI conditions. In the context of post-cardiac arrest, the impact of HTC on neurological outcomes has shown inconsistent results. In cases of TBI, HTC seems promising for reducing ICP, but its influence on long-term outcomes remains uncertain. For AIS, clinical trials have yet to conclusively demonstrate the benefits of HTC, despite encouraging preclinical evidence. This variability in efficacy is also observed in ICH, aSAH, bacterial meningitis, and status epilepticus. In pediatric and neonatal populations, while HTC shows significant benefits in hypoxic-ischemic encephalopathy, its effectiveness in other brain injuries is mixed. Although the theoretical basis for employing temperature control, especially HTC, is strong, the clinical outcomes differ among various SABI subtypes. The current consensus indicates that fever prevention is beneficial across the board, but the application and effectiveness of HTC are more nuanced, underscoring the need for further research to establish optimal temperature management strategies. Here we provide an overview of the clinical evidence surrounding the use of temperature control in various types of SABI.

Targeted Temperature Management After Out-of-Hospital Cardiac Arrest: Integrating Evidence Into Real World Practice

Targeted temperature management (TTM) after out-of-hospital cardiac arrest (OHCA) has been a focus of debate in an attempt to improve post-arrest outcomes. Contemporary trials examining the role of TTM after cardiac arrest suggest that targeting normothermia should be the standard of care for initially comatose survivors of cardiac arrest. Differences in patient populations have been demonstrated across trials, and important subgroups may be under-represented in clinical trials compared with real-world registries. In this review, we aimed to describe the populations represented in international OHCA registries and to propose a pathway to integrate clinical trial evidence into practice. The patient case mix among registries including survivors to hospital admission was similar to the pivotal trials (shockable rhythm, witnessed arrest), suggesting reasonable external validity. Therefore, for the majority of OHCA, targeted normothermia should be the strategy of choice. There remains conflicting evidence for patients with a nonshockable rhythm, with no clear evidence-based justification for mild hypothermia over targeted normothermia.

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.

Targeted Temperature Management and Postcardiac arrest Care

Despite recent advances, care of the post-cardiac arrest patient remains a challenge. In this article, the authors discuss an approach to the initial care of post-cardiac arrest patients with particular focus on targeted temperature management (TTM). The article starts with history, physiologic rationale, and the major randomized controlled trials that have shaped guidelines for post-cardiac arrest care. It also reviews controversial topics, including TTM for nonshockable rhythms, TTM dose, and surface versus endovascular cooling. The article concludes with a brief review of other key aspects of post-arrest care: coronary angiography, hemodynamic optimization, ventilator management, and prognostication.

Neutrophil-lymphocyte ratio: A prognostic tool in patients with in-hospital cardiac arrest

BACKGROUND

In-hospital cardiac arrest (IHCA) portends a poor prognosis and survival to discharge rate. Prognostic markers such as interleukin-6, S-100 protein and high sensitivity C reactive protein have been studied as predictors of adverse outcomes after return of spontaneous circulation (ROSC); however; these variables are not routine laboratory tests and incur additional cost making them difficult to incorporate and less attractive in assessing patient’s prognosis. The neutrophil-lymphocyte ratio (NLR) is a marker of adverse prognosis for many cardiovascular conditions and certain types of cancers and sepsis. We hypothesize that an elevated NLR is associated with poor outcomes including mortality at discharge in patients with IHCA.

AIM

To determine the prognostic significance of NLR in patients suffering IHCA who achieve ROSC.

METHODS

A retrospective study was performed on all patients who had IHCA with the advanced cardiac life support protocol administered in a large urban community United States hospital over a one-year period. Patients were divided into two groups based on their NLR value (NLR < 4.5 or NLR ≥ 4.5). This cutpoint was derived from receiving operator characteristic curve analysis (area under the curve = 0.66) and provided 73% positive predictive value, 82% sensitivity and 42% specificity for predicting in-hospital death after IHCA. The primary outcome was death or discharge at 30 d, whichever came first.

RESULTS

We reviewed 153 patients with a mean age of 66.1 ± 16.3 years; 48% were female. In-hospital mortality occurred in 65%. The median NLR in survivors was 4.9 (range 0.6-46.5) compared with 8.9 (0.28-96) in non-survivors (P = 0.001). A multivariable logistic regression model demonstrated that an NLR above 4.55 [odds ratio (OR) = 5.20, confidence interval (CI): 1.5-18.3, P = 0.01], older age (OR = 1.03, CI: 1.00-1.07, P = 0.05), and elevated serum lactate level (OR = 1.20, CI: 1.03-1.40, P = 0.02) were independent predictors of death.

CONCLUSION

An NLR ≥ 4.5 may be a useful marker of increased risk of death in patients with IHCA.

Editor's Choice-Effects of targeted temperature management on mortality and neurological outcome: A systematic review and meta-analysis

AIMS

The purpose of this study was to conduct a systematic review, and where applicable meta-analyses, examining the evidence underpinning the use of targeted temperature management following resuscitation from cardiac arrest.

METHODS AND RESULTS

Multiple databases were searched for publications between January 2000-February 2016. Nine Population, Intervention, Comparison, Outcome questions were developed and meta-analyses were performed when appropriate. Reviewers extracted study data and performed quality assessments using Grading of Recommendations, Assessment, Development and Evaluation methodology, the Cochrane Risk Bias Tool, and the National Institute of Health Study Quality Assessment Tool. The primary outcomes for each Population, Intervention, Comparison, Outcome question were mortality and poor neurological outcome. Overall, low quality evidence demonstrated that targeted temperature management at 32-36°C, compared to no targeted temperature management, decreased mortality (risk ratio 0.76, 95% confidence interval 0.61-0.92) and poor neurological outcome (risk ratio 0.73, 95% confidence interval 0.60-0.88) amongst adult survivors of out-of-hospital cardiac arrest with an initial shockable rhythm. Targeted temperature management use did not benefit survivors of in-hospital cardiac arrest nor out-of-hospital cardiac arrest survivors with a non-shockable rhythm. Moderate quality evidence demonstrated no benefit of pre-hospital targeted temperature management initiation. Low quality evidence showed no difference between endovascular versus surface cooling targeted temperature management systems, nor any benefit of adding feedback control to targeted temperature management systems. Low quality evidence suggested that targeted temperature management be maintained for 18-24 h.

CONCLUSIONS

Low quality evidence supports the in-hospital initiation and maintenance of targeted temperature management at 32-36°C amongst adult survivors of out-of-hospital cardiac arrest with an initial shockable rhythm for 18-24 h. The effects of targeted temperature management on other populations, the optimal rate and method of cooling and rewarming, and effects of fever require further study.

The Role of Targeted Temperature Management in Adult Patients Resuscitated from Nonshockable Cardiac Arrests: An Updated Systematic Review and Meta-Analysis

Routine targeted temperature management is recommended for comatose adult patients with return of spontaneous circulation after cardiac arrest. However, the role of targeted temperature management in patients resuscitated from nonshockable cardiac arrests remains uncertain. We conducted an updated systematic review and meta-analysis to evaluate the effects of targeted temperature management in this population. Medline, EMBASE, and Cochrane databases were systematically reviewed for studies published between January 2005 and March 2016, in which targeted temperature management was compared with standard care or normothermia for adult patients resuscitated from nonshockable cardiac arrests. A total of 25 trials that included 5715 patients were identified from 10985 relevant papers. Pooled data showed that targeted temperature management not only associated with improved short-term survival (RR = 1.42, 95% CI: 1.28-1.57) and neurological function (RR = 1.63, 95% CI: 1.39-1.91) but also associated with improved long-term survival (RR = 1.64, 95% CI: 1.27-2.12) and neurological recovery (RR = 1.42, 95% CI: 1.07-1.90) in observational cohort studies. However, more frequent infectious complications were reported in hypothermia-treated patients (RR = 1.46, 95% CI: 1.26-1.70) and the quality of the evidence ranged from moderate to very low.