Influence of temperature management at 33 °C versus normothermia on survival in patients with vasopressor support after out-of-hospital cardiac arrest: a post hoc analysis of the TTM-2 trial

Effect of targeted temperature management on systemic inflammatory responses after out-of-hospital cardiac arrest: A prospective cohort study

BACKGROUND

Interleukin (IL)-6 is a major inflammatory cytokine that predicts mortality after out-of-hospital cardiac arrest (OHCA). Targeted temperature management (TTM) is associated with improved all-cause mortality in patients with OHCA. However, the effect of TTM on IL-6 production remains unclear. This study investigated whether TTM has additional anti-inflammatory effects after OHCA.

METHODS

This prospective cohort study included a total of 141 hospitalized patients with OHCA who were treated between January 2015 and June 2023. The study was conducted in the intensive care unit of China Medical University Hospital, Taichung. Postcardiac arrest care included TTM or the control approach (no TTM). The primary outcomes included the 90-day mortality rate and neurologic outcomes after OHCA. Differences between the TTM and control groups were examined using Student t test, chi-square test, and Kaplan-Meier survival curve analysis. Multivariate analysis of variance model was used to examine interaction effects.

RESULTS

Plasma IL-6 and IL-6/soluble IL-6 receptor complex levels were measured at 6 and 24 hours after resuscitation. IL-6 and IL-6/soluble IL-6 receptor complex production was lower in the TTM group than in the control group (-50.0% vs +136.7%, P < .001; +26.3% vs +102.40%, P < .001, respectively). In addition, the 90-day mortality rate and poor neurologic outcomes were lower in the TTM group than in the control group (36.8% vs 63.0%, relative risk 0.39, 95% confidence interval 0.24-0.64, P < .001; 65.5% vs 81.5%, relative risk 0.80, 95% confidence interval 0.66-0.98, P = .04).

CONCLUSION

TTM improves both the mortality rate and neurologic outcomes in patients resuscitated from OHCA, possibly by reducing IL-6-induced proinflammatory responses.

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.

Ten rules for optimizing ventilatory settings and targets in post-cardiac arrest patients

Cardiac arrest (CA) is a major cause of morbidity and mortality frequently associated with neurological and systemic involvement. Supportive therapeutic strategies such as mechanical ventilation, hemodynamic settings, and temperature management have been implemented in the last decade in post-CA patients, aiming at protecting both the brain and the lungs and preventing systemic complications. A lung-protective ventilator strategy is currently the standard of care among critically ill patients since it demonstrated beneficial effects on mortality, ventilator-free days, and other clinical outcomes. The role of protective and personalized mechanical ventilation setting in patients without acute respiratory distress syndrome and after CA is becoming more evident. The individual effect of different parameters of lung-protective ventilation, including mechanical power as well as the optimal oxygen and carbon dioxide targets, on clinical outcomes is a matter of debate in post-CA patients. The management of hemodynamics and temperature in post-CA patients represents critical steps for obtaining clinical improvement. The aim of this review is to summarize and discuss current evidence on how to optimize mechanical ventilation in post-CA patients. We will provide ten tips and key insights to apply a lung-protective ventilator strategy in post-CA patients, considering the interplay between the lungs and other systems and organs, including the brain.

Outcomes of mild-to-moderate postresuscitation shock after non-shockable cardiac arrest and association with temperature management: a post hoc analysis of HYPERION trial data

BACKGROUND

Outcomes of postresuscitation shock after cardiac arrest can be affected by targeted temperature management (TTM). A post hoc analysis of the "TTM1 trial" suggested higher mortality with hypothermia at 33 °C. We performed a post hoc analysis of HYPERION trial data to assess potential associations linking postresuscitation shock after non-shockable cardiac arrest to hypothermia at 33 °C on favourable functional outcome.

METHODS

We divided the patients into groups with vs. without postresuscitation (defined as the need for vasoactive drugs) shock then assessed the proportion of patients with a favourable functional outcome (day-90 Cerebral Performance Category [CPC] 1 or 2) after hypothermia (33 °C) vs. controlled normothermia (37 °C) in each group. Patients with norepinephrine or epinephrine > 1 µg/kg/min were not included.

RESULTS

Of the 581 patients included in 25 ICUs in France and who did not withdraw consent, 339 had a postresuscitation shock and 242 did not. In the postresuscitation-shock group, 159 received hypothermia, including 14 with a day-90 CPC of 1-2, and 180 normothermia, including 10 with a day-90 CPC of 1-2 (8.81% vs. 5.56%, respectively; P = 0.24). After adjustment, the proportion of patients with CPC 1-2 also did not differ significantly between the hypothermia and normothermia groups (adjusted hazards ratio, 1.99; 95% confidence interval, 0.72-5.50; P = 0.18). Day-90 mortality was comparable in these two groups (83% vs. 86%, respectively; P = 0.43).

CONCLUSIONS

After non-shockable cardiac arrest, mild-to-moderate postresuscitation shock at intensive-care-unit admission did not seem associated with day-90 functional outcome or survival. Therapeutic hypothermia at 33 °C was not associated with worse outcomes compared to controlled normothermia in patients with postresuscitation shock. Trial registration ClinicalTrials.gov, NCT01994772.