Limited effect of mild therapeutic hypothermia on outcome after prolonged resuscitation

Hypothermia may reduce mortality and improve neurologic outcomes in adult patients treated with VA-ECMO: A systematic review and meta-analysis

BACKGROUND

VA-ECMO can greatly reduce mortality in critically ill patients, and hypothermia attenuates the deleterious effects of ischemia-reperfusion injury. We aimed to study the effects of hypothermia on mortality and neurological outcomes in VA-ECMO patients.

METHODS

A systematic search of the PubMed, Embase, Web of Science, and Cochrane Library databases was performed from the earliest available date to 31 December 2022. The primary outcome was discharge or 28-day mortality and favorable neurological outcomes in VA-ECMO patients, and the secondary outcome was bleeding risk in VA-ECMO patients. The results are presented as odds ratios (ORs) and 95% confidence intervals (CIs). Based on the heterogeneity assessed by the I2 statistic, meta-analyses were performed using random or fixed-effects models. GRADE methodology was used to rate the certainty in the findings.

RESULTS

A total of 27 articles (3782 patients) were included. Hypothermia (33-35 °C) lasting at least 24 h can significantly reduce discharge or 28-day mortality (OR, 0.45; 95% CI, 0.33-0.63; I2 = 41%) and significantly improve favorable neurological outcomes (OR, 2.08; 95% CI, 1.66-2.61; I2 = 3%) in VA-ECMO patients. Additionally, there was no risk associated with bleeding (OR, 1.15; 95% CI, 0.86-1.53; I2 = 12%). In our subgroup analysis according to in-hospital or out-of-hospital cardiac arrest, hypothermia reduced short-term mortality in both VA-ECMO-assisted in-hospital (OR, 0.30; 95% CI, 0.11-0.86; I2 = 0.0%) and out-of-hospital cardiac arrest (OR, 0.41; 95% CI, 0.25-0.69; I2 = 52.3%). Out-of-hospital cardiac arrest patients assisted by VA-ECMO for favorable neurological outcomes were consistent with the conclusions of this paper (OR, 2.10; 95% CI, 1.63-2.72; I2 = 0.5%).

CONCLUSIONS

Our results show that mild hypothermia (33-35 °C) lasting at least 24 h can greatly reduce short-term mortality and significantly improve favorable short-term neurologic outcomes in VA-ECMO-assisted patients without bleeding-related risks. As the grade assessment indicated that the certainty of the evidence was relatively low, hypothermia as a strategy for VA-ECMO-assisted patient care may need to be treated with caution.

Effect of Moderate vs Mild Therapeutic Hypothermia on Mortality and Neurologic Outcomes in Comatose Survivors of Out-of-Hospital Cardiac Arrest: The CAPITAL CHILL Randomized Clinical Trial

IMPORTANCE

Comatose survivors of out-of-hospital cardiac arrest experience high rates of death and severe neurologic injury. Current guidelines recommend targeted temperature management at 32 °C to 36 °C for 24 hours. However, small studies suggest a potential benefit of targeting lower body temperatures.

OBJECTIVE

To determine whether moderate hypothermia (31 °C), compared with mild hypothermia (34 °C), improves clinical outcomes in comatose survivors of out-of-hospital cardiac arrest.

DESIGN, SETTING, AND PARTICIPANTS

Single-center, double-blind, randomized, clinical superiority trial carried out in a tertiary cardiac care center in eastern Ontario, Canada. A total of 389 patients with out-of-hospital cardiac arrest were enrolled between August 4, 2013, and March 20, 2020, with final follow-up on October 15, 2020.

INTERVENTIONS

Patients were randomly assigned to temperature management with a target body temperature of 31 °C (n = 193) or 34 °C (n = 196) for a period of 24 hours.

MAIN OUTCOMES AND MEASURES

The primary outcome was all-cause mortality or poor neurologic outcome at 180 days. Neurologic outcome was assessed using the Disability Rating Scale, with poor neurologic outcome defined as a score greater than 5 (range, 0-29, with 29 being the worst outcome [vegetative state]). There were 19 secondary outcomes, including mortality at 180 days and length of stay in the intensive care unit.

RESULTS

Among 367 patients included in the primary analysis (mean age, 61 years; 69 women [19%]), 366 (99.7%) completed the trial. The primary outcome occurred in 89 of 184 patients (48.4%) in the 31 °C group and in 83 of 183 patients (45.4%) in the 34 °C group (risk difference, 3.0% [95% CI, 7.2%-13.2%]; relative risk, 1.07 [95% CI, 0.86-1.33]; P = .56). Of the 19 secondary outcomes, 18 were not statistically significant. Mortality at 180 days was 43.5% and 41.0% in patients treated with a target temperature of 31 °C and 34 °C, respectively (P = .63). The median length of stay in the intensive care unit was longer in the 31 °C group (10 vs 7 days; P = .004). Among adverse events in the 31 °C group vs the 34 °C group, deep vein thrombosis occurred in 11.4% vs 10.9% and thrombus in the inferior vena cava occurred in 3.8% and 7.7%, respectively.

CONCLUSIONS AND RELEVANCE

In comatose survivors of out-of-hospital cardiac arrest, a target temperature of 31 °C did not significantly reduce the rate of death or poor neurologic outcome at 180 days compared with a target temperature of 34 °C. However, the study may have been underpowered to detect a clinically important difference.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02011568.

Comparison of in-hospital and out-of-hospital cardiac arrest patients receiving targeted temperature management: A matched case-control study

BACKGROUND

Evidences that support the use of targeted temperature management (TTM) for in-hospital cardiac arrest (IHCA) are lacking. We aimed to investigate the hypothesis that TTM benefits for patients with IHCA are similar to those with out-of-hospital cardiac arrest (OHCA) and to determine the independent predictors of resuscitation outcomes in patients with cardiac arrest receiving subsequent TTM.

METHODS

This is a retrospective, matched, case-control study (ratio 1:1) including 93 patients with IHCA treated with TTM after the return of spontaneous circulation, who were admitted to Partners HealthCare system in Boston from January 2011 to December 2018. Controls were defined as the same number of patients with OHCA, matched for age, Charlson score, and sex. Survival and neurological outcomes upon discharge were the primary outcome measures.

RESULTS

Patients with IHCA were more likely to have experienced a witnessed arrest and receive bystander cardiopulmonary resuscitation, a larger total dosage of epinephrine, and extracorporeal membrane oxygenation. The time duration for ROSC was shorter in patients with IHCA than in those with OHCA. The IHCA group was more likely associated with mild thrombocytopenia during TTM than the OHCA group. Survival after discharge and favorable neurological outcomes did not differ between the two groups. Among all patients who had cardiac arrest treated with TTM, the initial shockable rhythm, time to ROSC, and medical history of heart failure were independent outcome predictors for survival to hospital discharge. The only factor to predict favorable neurological outcomes at discharge was initial shockable rhythm.

CONCLUSION

The beneficial effects of TTM in eligible patients with IHCA were similar with those with OHCA. Initial shockable rhythm was the only independent predictor of both survival and favorable neurological outcomes at discharge in all cardiac arrest survivors receiving TTM.

Trends in survival from out-of-hospital cardiac arrests defibrillated by paramedics, first responders and bystanders

BACKGROUND

Although survival from out-of-hospital cardiac arrest (OHCA) is increasing, little is known about the long-term trends in survival for patients defibrillated by first responders and bystanders.

METHODS

Between 2000 and 2017, we included adult non-traumatic OHCA with an initial shockable rhythm from the Victorian Ambulance Cardiac Arrest Registry. Adjusted logistic regression analyses were used to assess trends in survival to hospital discharge according to whether the patient was initially shocked by paramedics, first responders or bystanders.

RESULTS

Of the 10,451 initial shockable arrests, 796 (7.6%) and 526 (5.0%) were initially shocked by first responders and bystanders, respectively. Between 2000-02 and 2015-17, the proportion of cases initially shocked by first responders and bystanders increased from 3.8% to 8.2% and from 2.0% to 11.2%, respectively. Over the same period, survival to hospital discharge increased from 11.6% to 28.8% for cases initially shocked by paramedics, from 10.5% to 37.8% for cases initially shocked by first responders, and from 6.7% to 55.5% for cases initially shocked by bystanders (p trend <0.001 for all). In the adjusted analyses, patients initially shocked by first responders (AOR 1.40, 95% CI: 1.18, 1.67; p < 0.001) and bystanders (AOR 2.11, 95% CI: 1.72, 2.59; p < 0.001) were more likely to survive to hospital discharge than those initially shocked by paramedics. The odds of survival increased year-on-year by 8.1% for patients shocked by paramedics (p < 0.001), 6.1% for patients shocked by first responders (p = 0.004), and 11.8% for patients shocked by bystanders (p < 0.001).

CONCLUSION

OHCA patients initially defibrillated by bystanders yielded the largest improvements in survival over time.

Age-dependent effect of targeted temperature management on outcome after cardiac arrest

BACKGROUND

In elder patients after out-of-hospital cardiac arrest, diminished neurologic function as well as reduced neuronal plasticity may cause a low response to targeted temperature management (TTM). Therefore, we investigated the association between TTM (32-34°C) and neurologic outcome in cardiac arrest survivors with respect to age.

MATERIAL AND METHODS

This retrospective cohort study included patients 18 years of age or older suffering a witnessed out-of-hospital cardiac arrest with presumed cardiac cause, which remained comatose after return of spontaneous circulation. Patients were a priori split by age into four groups (<50 years (n = 496); 50-64 years (n = 714); 65-74 years (n = 395); >75 years (n = 280)). Subsequently, within these groups, patients receiving TTM were compared to those not treated with TTM.

RESULTS

Out of 1885 patients, 921 received TTM for 24 hours. TTM was significantly associated with good neurologic outcome in patients <65 years of age whereas showing no effect in elders (65-74 years: OR: 1.49 (95% CI: 0.90-2.47); > 75 years: OR 1.44 (95% CI 0.79-2.34)).

CONCLUSION

In our cohort, it seems that TTM might not be able to achieve the same benefit for neurologic outcome in all age groups. Although the results of this study should be interpreted with caution, TTM was associated with improved neurologic outcome only in younger individuals, patients with 65 years of age or older did not benefit from this treatment.

Derivation and Validation of the CREST Model for Very Early Prediction of Circulatory Etiology Death in Patients Without ST-Segment-Elevation Myocardial Infarction After Cardiac Arrest

BACKGROUND

No practical tool quantitates the risk of circulatory-etiology death (CED) immediately after successful cardiopulmonary resuscitation in patients without ST-segment-elevation myocardial infarction. We developed and validated a prediction model to rapidly determine that risk and facilitate triage to individualized treatment pathways.

METHODS

With the use of INTCAR (International Cardiac Arrest Registry), an 87-question data set representing 44 centers in the United States and Europe, patients were classified as having had CED or a combined end point of neurological-etiology death or survival. Demographics and clinical factors were modeled in a derivation cohort, and backward stepwise logistic regression was used to identify factors independently associated with CED. We demonstrated model performance using area under the curve and the Hosmer-Lemeshow test in the derivation and validation cohorts, and assigned a simplified point-scoring system.

RESULTS

Among 638 patients in the derivation cohort, 121 (18.9%) had CED. The final model included preexisting coronary artery disease (odds ratio [OR], 2.86; confidence interval [CI], 1.83-4.49; P≤0.001), nonshockable rhythm (OR, 1.75; CI, 1.10-2.77; P=0.017), initial ejection fraction<30% (OR, 2.11; CI, 1.32-3.37; P=0.002), shock at presentation (OR, 2.27; CI, 1.42-3.62; P<0.001), and ischemic time >25 minutes (OR, 1.42; CI, 0.90-2.23; P=0.13). The derivation model area under the curve was 0.73, and Hosmer-Lemeshow test P=0.47. Outcomes were similar in the 318-patient validation cohort (area under the curve 0.68, Hosmer-Lemeshow test P=0.41). When assigned a point for each associated factor in the derivation model, the average predicted versus observed probability of CED with a CREST score (coronary artery disease, initial heart rhythm, low ejection fraction, shock at the time of admission, and ischemic time >25 minutes) of 0 to 5 was: 7.1% versus 10.2%, 9.5% versus 11%, 22.5% versus 19.6%, 32.4% versus 29.6%, 38.5% versus 30%, and 55.7% versus 50%.

CONCLUSIONS

The CREST model stratified patients immediately after resuscitation according to risk of a circulatory-etiology death. The tool may allow for estimation of circulatory risk and improve the triage of survivors of cardiac arrest without ST-segment-elevation myocardial infarction at the point of care.

Relationship between timing of cooling and outcomes in adult comatose cardiac arrest patients treated with targeted temperature management

AIM OF THE STUDY

Studies examining associations between time to target temperature and outcomes in cardiac arrest patients who underwent targeted temperature management (TTM) have shown inconsistent results. We examined these associations separately for time from restoration of spontaneous circulation to TTM initiation (pre-induction time) and time from TTM initiation to target temperature (induction time). Furthermore, we examined whether critical time thresholds exist if there is an association.

METHODS

This was a single-centre retrospective observational study including adult cardiac arrest patients treated with TTM from 2008 to 2015. We tested the associations of pre-induction time and induction time with outcomes at hospital discharge using multivariate logistic regression analysis. We then performed additional multivariate analyses, each with the significant timing variable at different binary cutoffs.

RESULTS

A total of 515 patients were analysed. At hospital discharge, 357 patients (69.3%) were alive, of whom 161 (31.3%) had a favourable neurologic outcome. In multivariate analysis, a shorter pre-induction time was independently associated with a favourable neurologic outcome (odds ratio [OR], 1.110; 95% confidence interval [CI], 1.025-1.202), whereas the induction time was not (OR, 0.954; 95% CI, 0.852-1.067). We found two pre-induction time thresholds (120 and 360min) that were associated with neurologic outcome.

CONCLUSION

We found that a shorter pre-induction time was independently associated with a favorable neurologic outcome at hospital discharge, whereas induction time was not. We also found two time thresholds at 120 and 360min, after which initiation of cooling was associated with a worse neurologic outcome.

Time to Cooling Is Associated with Resuscitation Outcomes

Our purpose was to analyze evidence related to timing of cooling from studies of targeted temperature management (TTM) after return of spontaneous circulation (ROSC) after cardiac arrest and to recommend directions for future therapy optimization. We conducted a preliminary review of studies of both animals and patients treated with post-ROSC TTM and hypothesized that a more rapid cooling strategy in the absence of volume-adding cold infusions would provide improved outcomes in comparison with slower cooling. We defined rapid cooling as the achievement of 34°C within 3.5 hours of ROSC without the use of volume-adding cold infusions, with a ≥3.0°C/hour rate of cooling. Using the PubMed database and a previously published systematic review, we identified clinical studies published from 2002 through 2014 related to TTM. Analysis included studies with time from collapse to ROSC of 20–30 minutes, reporting of time from ROSC to target temperature and rate of patients in ventricular tachycardia or ventricular fibrillation, and hypothermia maintained for 20–24 hours. The use of cardiopulmonary bypass as a cooling method was an exclusion criterion for this analysis. We compared all rapid cooling studies with all slower cooling studies of ≥100 patients. Eleven studies were initially identified for analysis, comprising 4091 patients. Two additional studies totaling 609 patients were added based on availability of unpublished data, bringing the total to 13 studies of 4700 patients. Outcomes for patients, dichotomized into faster and slower cooling approaches, were determined using weighted linear regression using IBM SPSS Statistics software. Rapid cooling without volume-adding cold infusions yielded a higher rate of good neurological recovery than slower cooling methods. Attainment of a temperature below 34°C within 3.5 hours of ROSC and using a cooling rate of more than 3°C/hour appear to be beneficial.