Single-cell transcriptomics reveal a hyperacute cytokine and immune checkpoint axis after cardiac arrest in patients with poor neurological outcome

Combination of Hydrogen Inhalation and Hypothermic Temperature Control After Out-of-Hospital Cardiac Arrest: A Post hoc Analysis of the Efficacy of Inhaled Hydrogen on Neurologic Outcome Following Brain Ischemia During PostCardiac Arrest Care II Trial

OBJECTIVE

The Efficacy of Inhaled Hydrogen on Neurologic Outcome Following Brain Ischemia During Post-Cardiac Arrest Care (HYBRID) II trial (jRCTs031180352) suggested that hydrogen inhalation may reduce post-cardiac arrest brain injury (PCABI). However, the combination of hypothermic target temperature management (TTM) and hydrogen inhalation on outcomes is unclear. The aim of this study was to investigate the combined effect of hydrogen inhalation and hypothermic TTM on outcomes after out-of-hospital cardiac arrest (OHCA).

DESIGN

Post hoc analysis of a multicenter, randomized, controlled trial.

SETTING

Fifteen Japanese ICUs.

PATIENTS

Cardiogenic OHCA enrolled in the HYBRID II trial.

INTERVENTIONS

Hydrogen mixed oxygen (hydrogen group) versus oxygen alone (control group).

MEASUREMENTS AND MAIN RESULTS

TTM was performed at a target temperature of 32-34°C (TTM32-TTM34) or 35-36°C (TTM35-TTM36) per the institutional protocol. The association between hydrogen + TTM32-TTM34 and 90-day good neurologic outcomes was analyzed using generalized estimating equations. The 90-day survival was compared between the hydrogen and control groups under TTM32-TTM34 and TTM35-TTM36, respectively. The analysis included 72 patients (hydrogen [ n = 39] and control [ n = 33] groups) with outcome data. TTM32-TTM34 was implemented in 25 (64%) and 24 (73%) patients in the hydrogen and control groups, respectively ( p = 0.46). Under TTM32-TTM34, 17 (68%) and 9 (38%) patients achieved good neurologic outcomes in the hydrogen and control groups, respectively (relative risk: 1.81 [95% CI, 1.05-3.66], p < 0.05). Hydrogen + TTM32-TTM34 was independently associated with good neurologic outcomes (adjusted odds ratio 16.10 [95% CI, 1.88-138.17], p = 0.01). However, hydrogen + TTM32-TTM34 did not improve survival compared with TTM32-TTM34 alone (adjusted hazard ratio: 0.22 [95% CI, 0.05-1.06], p = 0.06).

CONCLUSIONS

Hydrogen + TTM32-TTM34 was associated with improved neurologic outcomes after cardiogenic OHCA compared with TTM32-TTM34 monotherapy. Hydrogen inhalation is a promising treatment option for reducing PCABI when combined with TTM32-TTM34.

Protocol for immunophenotyping out-of-hospital cardiac arrest patients

Immunophenotyping of out-of-hospital cardiac arrest (OHCA) patients is of increasing interest but has challenges. Here, we describe steps for the design of the clinical cohort, planning patient enrollment and sample collection, and ethical review of the study protocol. We detail procedures for blood sample collection and cryopreservation of peripheral blood mononuclear cells (PBMCs). We detail steps to modulate immune checkpoints in OHCA PBMC ex vivo. This protocol also has relevance for immunophenotyping other types of critical illness. For complete details on the use and execution of this protocol, please refer to Tamura et al. (2023).1.