Intermittent versus continuous neuromuscular blockade during target temperature management after cardiac arrest: A nationwide observational study

Association between neuromuscular blocking agent use and outcomes among out-of-hospital cardiac arrest patients treated with extracorporeal cardiopulmonary resuscitation and target temperature management: A secondary analysis of the SAVE-J II study

Background

Neuromuscular blocking agents are used to control shivering in cardiac arrest patients treated with target temperature management. However, their effect on outcomes in patients treated with extracorporeal cardiopulmonary resuscitation is unclear.

Methods

This study was a secondary analysis of the SAVE-J II study, a retrospective multicenter study of 2175 out-of-hospital cardiac arrest patients treated with extracorporeal cardiopulmonary resuscitation in Japan. We classified patients into those who received neuromuscular blocking agents and those who did not and compared in-hospital mortality and incidence rates of favorable neurological outcome and in-hospital pneumonia between the groups using multivariable regression models and stabilized inverse probability weighting with propensity scores.

Results

Six hundred sixty patients from the SAVE-J II registry were analyzed. Neuromuscular blocking agents were used in 451 patients (68.3%). After adjusting for potential confounders, neuromuscular blocking agents use was not significantly associated with in-hospital mortality (aHR 0.88; 95% CI, 0.67-1.14), favorable neurological outcome (aOR 0.85; 95% CI, 0.60-1.11), or pneumonia (aOR 1.52; 95% CI, 0.85-2.71). The results for in-hospital mortality (aHR 0.89; 95% CI, 0.64-1.25), favorable neurological outcome (aOR 0.94; 95% CI, 0.59-1.48) and pneumonia (aOR 1.59; 95% CI, 0.74-3.41) were similar after weighting was performed.

Conclusions

Although data on the rationale for using neuromuscular blocking agents were unavailable, their use was not significantly associated with outcomes in out-of-hospital cardiac arrest patients treated with extracorporeal cardiopulmonary resuscitation and targeted temperature management. Neuromuscular blocking agents should be used based on individual clinical indications.

Targeted Temperature Management in Cardiac Arrest: An Updated Narrative Review

The established benefits of cooling along with development of sophisticated methods to safely and precisely induce, maintain, monitor, and reverse hypothermia have led to the development of targeted temperature management (TTM). Early trials in human subjects showed that hypothermia conferred better neurological outcomes when compared to normothermia among survivors of cardiac arrest, leading to guidelines recommending targeted hypothermia in this patient population. Multiple studies have sought to explore and compare the benefit of hypothermia in various subgroups of patients, such as survivors of out-of-hospital cardiac arrest versus in-hospital cardiac arrest, and survivors of an initial shockable versus non-shockable rhythm. Larger and more recent trials have shown no statistically significant difference in neurological outcomes between patients with targeted hypothermia and targeted normothermia; further, aggressive cooling is associated with a higher incidence of multiple systemic complications. Based on this data, temporal trends have leaned towards using a lenient temperature target in more recent times. Current guidelines recommend selecting and maintaining a constant target temperature between 32 and 36 °C for those patients in whom TTM is used (strong recommendation, moderate-quality evidence), as soon as possible after return of spontaneous circulation is achieved and airway, breathing (including mechanical ventilation), and circulation are stabilized. The comparative benefit of lower (32-34 °C) versus higher (36 °C) temperatures remains unknown, and further research may help elucidate this. Any survivor of cardiac arrest who is comatose (defined as unarousable unresponsiveness to external stimuli) should be considered as a candidate for TTM regardless of the initial presenting rhythm, and the decision to opt for targeted hypothermia versus targeted normothermia should be made on a case-by-case basis.

Neuromuscular Blockade for Cardiac Arrest Patients Treated With Targeted Temperature Management: A Systematic Review and Meta-Analysis

Background: Neuromuscular-blocking agents (NMBA) are often administered to control shivering in comatose cardiac arrest (CA) survivors during targeted temperature management (TTM) management. Thus, we performed a systematic review and meta-analysis to investigate the effectiveness and safety of NMBA in such a patient population. Methods: We searched for relevant studies in PubMed, Embase, and the Cochrane Library until 15 Jul 2021. Studies were included if they reported data on any of the predefined outcomes in adult comatose CA survivors managed with any NMBA regimens. The primary outcomes were mortality and neurological outcome. Results were expressed as odds ratio (OR) or mean difference (MD) with an accompanying 95% confidence interval (CI). Heterogeneity, sensitivity analysis, and publication bias were also investigated to test the robustness of the primary outcome. Data Synthesis: We included 12 studies (3 randomized controlled trials and nine observational studies) enrolling 11,317 patients. These studies used NMBA in three strategies: prophylactic NMBA, bolus NMBA if demanded, or managed without NMBA. Pooled analysis showed that CA survivors with prophylactic NMBA significantly improved both outcomes of mortality (OR 0.74; 95% CI 0.64-0.86; I 2 = 41%; p < 0.0001) and neurological outcome (OR 0.53; 95% CI 0.37-0.78; I 2 = 59%; p = 0.001) than those managed without NMBA. These results were confirmed by the sensitivity analyses and subgroup analyses. Only a few studies compared CA survivors receiving continuous versus bolus NMBA if demanded strategies and the pooled results showed no benefit in the primary outcomes between the two groups. Conclusion: Our results showed that using prophylactic NMBA strategy compared to the absence of NMBA was associated with improved mortality and neurologic outcome in CA patients undergoing TTM. However, more high-quality randomized controlled trials are needed to confirm our results.

The Use of Neuromuscular Blockers to Prevent Shivering in the Setting of Postcardiac Arrest Targeted Temperature Management: A Narrative Review of an Off-Label Indication

Targeted temperature management (TTM) has become a standard of care over the past two decades for the improvement in neurologic function and mortality in postcardiac arrest patients. There are various mechanisms by which hypothermia helps to improve these outcomes, one of which is by reducing oxygen requirements. Less established is the use of nondepolarizing neuromuscular blockers (NMBs) to prevent shivering during TTM. Shivering can be disadvantageous in this setting as it increases oxygen requirements, which TTM is actively trying to decrease, in an already oxygen-deprived system as well as generates heat making it difficult to maintain hypothermia. Whether NMBs can improve these outcomes is conflicting in the currently available literature and there lacks a consensus on their role in shivering management. The pharmacokinetic and pharmacodynamic responses of these agents may be altered in hypothermic patients, therefore, their standard of monitoring may be unreliable. The accurate dosing and administration of these agents also remain unclear, further complicated by the lack of a standard use protocol. Various studies have been conducted regarding the use of NMBs to prevent shivering in postcardiac arrest patients undergoing TTM; however, it remains an off-label indication requiring further investigation.