Cooling to Hypothermic Circulatory Arrest by Immersion vs. Cardiopulmonary Bypass (CPB): Worse Outcome After Rewarming in Immersion Cooled Pigs

Introduction

Cooling by cardiopulmonary bypass (CPB) to deep hypothermic cardiac arrest (HCA) for cardiac surgical interventions, followed by CPB-rewarming is performed on a routine basis with relatively low mortality. In contrast, victims of deep accidental hypothermia rewarmed with CPB generally have a much worse prognosis. Thus, we have developed an intact pig model to compare effects on perfusion pressures and global oxygen delivery (DO₂) during immersion cooling versus cooling by CPB. Further, we compared the effects of CPB-rewarming between groups, to restitute cardiovascular function, brain blood flow, and brain metabolism.

Materials and Methods

Total sixteen healthy, anesthetized juvenile (2–3 months) castrated male pigs were randomized in a prospective, open placebo-controlled experimental study to immersion cooling (IMM_c, n = 8), or cooling by CPB (CPB_c, n = 8). After 75 minutes of deep HCA in both groups, pigs were rewarmed by CPB. After weaning from CPB surviving animals were observed for 2 h before euthanasia.

Results

Survival rates at 2 h after completed rewarming were 4 out of 8 in the IMM_c group, and 8 out of 8 in the CPB_c group. Compared with the CPB_c-group, IMM_c animals showed significant reduction in DO₂, mean arterial pressure (MAP), cerebral perfusion pressure, and blood flow during cooling below 25°C as well as after weaning from CPB after rewarming. After rewarming, brain blood flow returned to control in CPB_c animals only, and brain micro dialysate-data showed a significantly increase in the lactate/pyruvate ratio in IMM_c vs. CPB_c animals.

Conclusion

Our data indicate that, although global O₂ consumption was independent of DO₂, regional ischemic damage may have taken place during cooling in the brain of IMM_c animals below 25°C. The need for prolonged extracorporeal membrane oxygenation (ECMO) should be considered in all victims of accidental hypothermic arrest that cannot be weaned from CPB immediately after rewarming.

Accidental Hypothermia: 2021 Update

Accidental hypothermia is an unintentional drop of core temperature below 35 °C. Annually, thousands die of primary hypothermia and an unknown number die of secondary hypothermia worldwide. Hypothermia can be expected in emergency patients in the prehospital phase. Injured and intoxicated patients cool quickly even in subtropical regions. Preventive measures are important to avoid hypothermia or cooling in ill or injured patients. Diagnosis and assessment of the risk of cardiac arrest are based on clinical signs and core temperature measurement when available. Hypothermic patients with risk factors for imminent cardiac arrest (temperature < 30 °C in young and healthy patients and <32 °C in elderly persons, or patients with multiple comorbidities), ventricular dysrhythmias, or systolic blood pressure < 90 mmHg) and hypothermic patients who are already in cardiac arrest, should be transferred directly to an extracorporeal life support (ECLS) centre. If a hypothermic patient arrests, continuous cardiopulmonary resuscitation (CPR) should be performed. In hypothermic patients, the chances of survival and good neurological outcome are higher than for normothermic patients for witnessed, unwitnessed and asystolic cardiac arrest. Mechanical CPR devices should be used for prolonged rescue, if available. In severely hypothermic patients in cardiac arrest, if continuous or mechanical CPR is not possible, intermittent CPR should be used. Rewarming can be accomplished by passive and active techniques. Most often, passive and active external techniques are used. Only in patients with refractory hypothermia or cardiac arrest are internal rewarming techniques required. ECLS rewarming should be performed with extracorporeal membrane oxygenation (ECMO). A post-resuscitation care bundle should complement treatment.

The use of minimal invasive extracorporeal circulation for rewarming after accidental hypothermia and circulatory arrest

BACKGROUND

Extracorporeal cardiopulmonary resuscitation has become a recommended treatment option for patients with severe hypothermia with cardiac arrest. Minimal invasive extracorporeal circulation (MiECC) may offer advantages over the current standard extracorporeal membrane oxygenation (ECMO).

METHODS

Retrospective cohort analysis of hospital database for patients with accidental hypothermia and extracorporeal rewarming with MiECC admitted between 2010 and 2019.

RESULTS

Overall, six of 17 patients survived to hospital discharge. Eleven patients suffered accidental hypothermia in an alpine and six in an urban setting. Sixteen patients arrived at the hospital under ongoing cardiopulmonary resuscitation (CPR). CPR time was 90 minutes (0-150). Four patients survived from an alpine setting and two from an urban setting with CPR duration of 90 minutes (0-150) and 85 minutes (25-100), respectively. Asphyctic patients tended to have lower survival (one of seven patients). Two patients of six with major trauma survived.

CONCLUSION

MiECC for extracorporeal rewarming from severe accidental hypothermia is a feasible alternative to ECMO, with comparable survival rates.

The Impact of Accidental Hypothermia on Mortality in Trauma Patients Overall and Patients with Traumatic Brain Injury Specifically: A Systematic Review and Meta-Analysis

Background

Accidental hypothermia is a known predictor for worse outcomes in trauma patients, but has not been comprehensively assessed in a meta-analysis so far. The aim of this systematic review and meta-analysis was to investigate the impact of accidental hypothermia on mortality in trauma patients overall and patients with traumatic brain injury (TBI) specifically.

Methods

This is a systematic review and meta-analysis using the Ovid Medline/PubMed database. Scientific articles reporting accidental hypothermia and its impact on outcomes in trauma patients were included in qualitative synthesis. Studies that compared the effect of hypothermia vs. normothermia at hospital admission on in-hospital mortality were included in two meta-analyses on (1) trauma patients overall and (2) patients with TBI specifically. Meta-analysis was performed using a Mantel–Haenszel random-effects model.

Results

Literature search revealed 264 articles. Of these, 14 studies published 1987–2018 were included in the qualitative synthesis. Seven studies qualified for meta-analysis on trauma patients overall and three studies for meta-analysis on patients with TBI specifically. Accidental hypothermia at admission was associated with significantly higher mortality both in trauma patients overall (OR 5.18 [95% CI 2.61–10.28]) and patients with TBI specifically (OR 2.38 [95% CI 1.53–3.69]).

Conclusions

In the current meta-analysis, accidental hypothermia was strongly associated with higher in-hospital mortality both in trauma patients overall and patients with TBI specifically. These findings underscore the importance of measures to avoid accidental hypothermia in the prehospital care of trauma patients.

Electronic supplementary material

The online version of this article (10.1007/s00268-020-05750-5) contains supplementary material, which is available to authorized users.

An observational study of self-monitoring in ad hoc health care teams

BACKGROUND

Working in ad hoc teams in a health care environment is frequent but a challenging and complex undertaking. One way for teams to refine their teamwork could be through post-resuscitation reflection and debriefing. However, this would require that teams have insight into the quality of their teamwork. This study investigates (1) the accuracy of the self-monitoring of ad hoc resuscitation teams and their leaders relative to external observations of their teamwork and (2) the relationship of team self-monitoring and external observations to objective performance measures.

METHODS

We conducted a quantitative observational study of real-world ad hoc interprofessional teams responding to a simulated cardiac arrest in an emergency room. Teams consisting of residents, consultants, and nurses were confronted with an unexpected, simulated, standardized cardiac arrest situation. Their teamwork was videotaped to allow for subsequent external evaluation on the team emergency assessment measure (TEAM) checklist. In addition, objective performance measures such as time to defibrillation were collected. All participants completed a demographic questionnaire prior to the simulation and a questionnaire tapping their perceptions of teamwork directly after it.

RESULTS

22 teams consisting of 115 health care professionals showed highly variable performance. All performance measures intercorrelated significantly, with the exception of team leaders' evaluations of teamwork, which were not related to any other measures. Neither team size nor cumulative experience were correlated with any measures, but teams led by younger leaders performed better than those led by older ones.

CONCLUSION

Team members seem to have better insight into their team's teamwork than team leaders. As a practical consequence, the decision to debrief and the debriefing itself after a resuscitation should be informed by team members, not just leaders.