Community-Based Application of Mild Therapeutic Hypothermia for Survivors of Cardiac Arrest:

Effects of Different Hypothermia on the Results of Cardiopulmonary Resuscitation in a Cardiac Arrest Rat Model

Objective

To investigate the optimal temperature of hypothermia treatment in rats with cardiac arrest caused by ventricular fibrillation (VF) after the return of spontaneous circulation (ROSC).

Methods

A total of forty-eight male Sprague-Dawley rats were induced by VF through the guidewire with a maximum of 5 mA current and untreated for 8 min. Cardiopulmonary resuscitation (CPR) was performed for 8 min followed by defibrillation (DF). Resuscitated rats were then randomized into the normothermia (37°C) group, milder (35°C) group, mild (33°C) group, or moderate (28°C) group. Hypothermia was immediately induced with surface cooling. The target temperature was maintained for 4 h before rewarming to 37 ± 0.5°C. Moreover, at the end of the 4 h, a rat in each group was randomly selected to be sacrificed for the cerebral cortex electron microscopy observation (n = 1). The other resuscitated animals were observed for up to 72 h after ROSC (n = 7). Left ventricular ejection fraction (LVEF) and left ventricular end diastolic volume (LVEDV) were measured. Survival time, survival rate, and neurological deficit score (NDS) were recorded for 72 h.

Results

During hypothermia, higher LVEF was observed in the hypothermia groups when compared with normothermia group (35°C vs. 37°C, p < 0.05, 33°C and 28°C vs. 37°C, p < 0.01). Among the hypothermia groups, LVEF was higher in the 28°C group than that of 35°C (p < 0.05). However, both the heart rate (HR) (p < 0.01) and LVEDV (28°C vs. 35°C, p < 0.01, 28°C vs. 37°C and 33°C, p < 0.05) were lowest in the 28°C group when compared with the other groups. There were no significant differences of LVEF and LVEDV between the group 35°C and 33°C (p > 0.05). After rewarming, the LVEF of 35°C group was higher than that of group 37°C, 33°C, and 28°C (35°C vs. 37°C and 28°C, p < 0.01, 35°C vs. 33°C, p < 0.05). Group 35°C and 33°C resulted in longer survival (p < 0.01), higher survival rate (p < 0.01), and lower NDS (35°C vs. 37°C and 28°C, p < 0.01, 33°C vs. 37°C and 28°C, p < 0.05) compared with the group 37°C and 28°C. The extent of damage to cerebral cortex cells in group of 35°C and 33°C was lighter than that in group of 37°C and 28°C. The 35°C group spent less time in the process of cooling and rewarming than the group 33°C and 28°C (p < 0.01).

Conclusions

An almost equal protective effect of milder hypothermia (35°C) and mild hypothermia (33°C) in cardiac arrest (CA) rats was achieved with more predominant effect than moderate hypothermia (28°C) and normothermia (37°C). More importantly, shorter time spent in cooling and rewarming was required in the 35°C group, indicating its potential clinical application. These findings support the possible use of milder hypothermia (35°C) as a therapeutic agent for postresuscitation.

The effect of mild induced hypothermia on outcomes of patients after cardiac arrest: a systematic review and meta-analysis of randomised controlled trials

INTRODUCTION

Mild induced hypothermia (MIH) is believed to reduce mortality and neurological impairment after out-of-hospital cardiac arrest. However, a recently published trial demonstrated that hypothermia at 33 °C did not confer a benefit compared with that of 36 °C. Thus, a systematic review and meta-analysis of randomised controlled trials (RCTs) was made to investigate the impact of MIH compared to controls on the outcomes of adult patients after cardiac arrest.

METHODS

We searched the following electronic databases: PubMed/MEDLINE, the Cochrane Library, Embase, the Web of Science, and Elsevier Science (inception to December 2014). RCTs that compared MIH with controls with temperature >34 °C in adult patients after cardiac arrest were retrieved. Two investigators independently selected RCTs and completed an assessment of the quality of the studies. Data were analysed by the methods recommended by the Cochrane Collaboration. Random errors were evaluated with trial sequential analysis.

RESULTS

Six RCTs, including one abstract, were included. The meta-analysis of included trials revealed that MIH did not significantly decrease the mortality at hospital discharge (risk ratio (RR) = 0.92; 95 % confidence interval (CI), 0.82-1.04; p = 0.17) or at 6 months or 180 days (RR = 0.94; 95 % CI, 0.73-1.21; p = 0.64), but it did reduce the mortality of patients with shockable rhythms at hospital discharge (RR = 0.74; 95 % CI, 0.59-0.92; p = 0.008) and at 6 months or 180 days. However, MIH can improve the outcome of neurological function at hospital discharge (RR = 0.80; 95 % CI, 0.64-0.98; p = 0.04) especially in those patients with shockable rhythm but not at 6 months or 180 days. Moreover, the incidence of complications in the MIH group was significantly higher than that in the control group. Finally, trial sequential analysis indicated lack of firm evidence for a beneficial effect.

CONCLUSION

The available RCTs suggest that MIH does not appear to improve the mortality of patients with cardiac arrest while it may have a beneficial effect for patients with shockable rhythms. Although MIH may result in some adverse events, it helped lead to better outcomes regarding neurological function at hospital discharge. Large-scale ongoing trials may provide data better applicable to clinical practice.

Therapeutic hypothermia post-cardiac arrest: a clinical nurse specialist initiative in Pakistan

PURPOSE

The purpose of this project was to assess the feasibility of an evidence-based therapeutic hypothermia protocol in adult post-cardiac arrest (CA) patients in a university hospital in Pakistan.

BACKGROUND

Cardiac arrest has a deleterious effect on neurological function, and survival is associated with significant morbidity. The International Liaison Committee of Cardiopulmonary Resuscitation and the American Heart Association recommend the use of mild hypothermia in post-CA victims to mitigate brain injury caused by anoxia. In Pakistan, the survival rate in CA victims is poor. At present, there are no hospitals in the country that use the evidence-based hypothermia intervention in adult post-CA victims.

DESCRIPTION

This pilot project of therapeutic hypothermia in adult post-CA patients was implemented in a university hospital in Pakistan by a clinical nurse specialist in collaboration with the cardiopulmonary resuscitation committee and the nursing leadership of the hospital. Various clinical nurse specialist competencies and roles were used to address the 3 spheres of influence: patient, nurses, and system, while executing an evidence-based hypothermia protocol. Process and outcome indicators were monitored to evaluate the effectiveness and feasibility of hypothermia intervention in this setting.

OUTCOME

The hypothermia protocol was successfully implemented in 3 adult post-CA patients using cost-effective measures. All 3 patients were extubated within 72 hours after CA, and 2 patients were discharged home with good neurological outcome.

CONCLUSION

Adoption of an evidence-based hypothermia protocol for adult CA patients is feasible in the intensive care setting of a university hospital in Pakistan.

IMPLICATIONS

The process used in the project can serve as a road map to other hospitals in resource-limited countries such as Pakistan that are motivated to improve post-CA outcomes. This experience reveals that advanced practice nurses can be instrumental in translation of evidence into practice in a healthcare system in Pakistan.

Therapeutic temperature management after cardiac arrest and the risk of bleeding: systematic review and meta-analysis

AIM

Prognosis after cardiac arrest in the era of modern critical care is still poor with a high mortality of approximately 90%. Around 30% of the survivors have neurological impairments. Targeted temperature management (TTM) is the only treatment option which can improve mortality and neurological outcome. It is so far unclear if bleeding complications occur more often in patients undergoing TTM treatment.

METHODS

We conducted a systematic literature research in September 2013 including three major databases i.e. MEDLINE, EMBASE and CENTRAL. All studies were rated in respect to the ILCOR Guidelines and concerning their level of evidence and quality. We then performed a meta-analysis on bleeding disposition under TTM.

RESULTS

We initially found 941 studies out of which 34 matched our requirements and were thus included in our overview. Five studies including 599 patients were summarized in a meta-analysis concerning bleeding complications of all severities. There was a trend toward higher bleeding in patients treated with TTM (RR: 1.30, 95% CI: 0.97-1.74) which did not reach significance (p=0.085). Seven studies with an overall 599 patients were included in our meta-analysis on bleeding requiring transfusion. There was no significant difference in the incidence of severe bleeding with a risk ratio of 0.97 (95% CI: 0.61-1.56, p=0.909).

CONCLUSIONS

The data included in our meta-analysis indicate that, concerning the risk of bleeding, TTM is a safe method for patients after cardiac arrest. We did not observe a significantly higher risk for bleeding in patients undergoing TTM.

How effective is "code freeze" in post-cardiac arrest patients?

The use of therapeutic hypothermia or "code freeze" dates back to over 100 years in attempts to resuscitate injured soldiers, preserve limbs, and to provide analgesia for amputations. The purpose of this study was to determine the effectiveness of code freeze through a retrospective review of 187 charts of patients who had a cardiac arrest while hospitalized in a 1-year period. Data were collected to determine which post-cardiac arrest patients received the induced therapeutic hypothermia intervention and why they were selected for induced therapeutic hypothermia. The data were compared with post-cardiac arrest patients who did not receive the code-freeze intervention and why they were not eligible for the intervention. Mortality rates between the 2 patient populations were also compared. The results from this study are presented in this article.

Therapeutic hypothermia for cardiac arrest: real-world utilization trends and hospital mortality

BACKGROUND

Therapeutic hypothermia (TH) improves outcomes following cardiac arrest in small clinical trials.

OBJECTIVE

To study real-world utilization and outcomes in US hospitals.

DESIGN

Retrospective cohort study.

SETTING

California hospitals.

PATIENTS

Patients eligible for therapeutic hypothermia after cardiac arrest.

INTERVENTIONS

We analyzed all discharges from California (1999-2008) to identify patients eligible for TH after cardiac arrest. Patients were considered eligible for TH if both cardiac arrest and anoxic brain injury were among the administrative diagnoses (n = 46,833). Patients undergoing TH (n = 204) were identified through billing codes.

MEASUREMENTS

TH utilization and in-hospital mortality.

RESULTS

Use of TH increased over the study period with 87.3% (178/204) of TH occurring between 2006 and 2008. Few hospitals appeared to perform TH over the study period (47/419, 11.2%). Utilization of TH was concentrated in a few centers, with the top 3 of 419 centers accounting for 31.4% (64/204) of cases. Patients undergoing TH were younger, less likely to be male, more likely to be treated at teaching centers, and had similar comorbidities compared to eligible individuals who did not undergo TH. The adjusted odds ratio for hospital mortality among patients undergoing TH was 0.80 (95% confidence interval [CI] 0.60-1.06, P = 0.11).

CONCLUSIONS

TH utilization appears low, but implementation is increasing. Case selection and referral biases limit the analysis of the relationship between center TH volume and in-hospital mortality.

Therapeutic hypothermia after cardiac arrest: experience at an academically affiliated community-based veterans affairs medical center

At laboratory and clinical levels, therapeutic hypothermia has been shown to improve neurologic outcomes and mortality following cardiac arrest. We reviewed each cardiac arrest in our community-based Veterans Affairs Medical Center over a three-year period. The majority of cases were in-hospital arrests associated with initial pulseless electrical activity or asystole. Of a total of 100 patients suffering 118 cardiac arrests, 29 arrests involved comatose survivors, with eight patients completing therapeutic cooling. Cerebral performance category scores at discharge and six months were significantly better in the cooled cohort versus the noncooled cohort, and, in every case except for one, cooling was offered for appropriate reasons. Mean time to initiation of cooling protocol was 3.7 hours and mean time to goal temperature of 33°C was 8.8 hours, and few complications clearly related to cooling were noted in our case series. While in-patient hospital mortality of cardiac arrest was high at 65% mortality during hospital admission, therapeutic hypothermia was safe and feasible at our center. Our cooling times and incidence of favorable outcomes are comparable to previously published reports. This study demonstrates the feasibility of implementing, a cooling protocol a community setting, and the role of neurologists in ensuring effective hospital-wide implementation.