Targeted Temperature Management: Effects of Initial Protocol Implementation on Patient Outcomes

Quality of targeted temperature management and outcome of out-of-hospital cardiac arrest patients: A post hoc analysis of the TTH48 study

BACKGROUND

No data are available on the quality of targeted temperature management (TTM) provided to out-of-hospital cardiac arrest (OHCA) patients and its association with outcome.

METHODS

Post hoc analysis of the TTH48 study (NCT01689077), which compared the effects of prolonged TTM at 33 °C for 48 h to standard 24-h TTM on neurologic outcome. Admission temperature, speed of cooling, rewarming rates, precision (i.e. temperature variability), overcooling and overshooting as post-cooling fever (i.e. >38.0 °C) were collected. A specific score, ranging from 1 to 9, was computed to define the "quality of TTM".

RESULTS

On a total of 352 patients, most had a moderate quality of TTM (n = 217; 62% - score 4-6), while 80 (23%) patients had a low quality of TTM (score 1-3) and only 52 (16%) a high quality of TTM (score 7-9). The proportion of patients with unfavorable neurological outcome (UO; Cerebral Performance Category of 3-5 at 6 months) was similar between the different quality of TTM groups (p = 0.90). Although a shorter time from arrest to target temperature and a lower proportion of time outside the target ranges in the TTM 48-h than in the TTM 24-h group, quality of TTM was similar between groups. Also, the proportion of patients with UO was similar between the different quality of TTM groups when TTM 48-h and TTM 24-h were compared.

CONCLUSIONS

In this study, high quality of TTM was provided to a small proportion of patients. However, quality of TTM was not associated with patients' outcome.

High Quality Targeted Temperature Management (TTM) After Cardiac Arrest

Targeted temperature management (TTM) is a complex intervention used with the aim of minimizing post-anoxic injury and improving neurological outcome after cardiac arrest. There is large variability in the devices used to achieve cooling and in protocols (e.g., for induction, target temperature, maintenance, rewarming, sedation, management of post-TTM fever). This variability can explain the limited benefits of TTM that have sometimes been reported. We therefore propose the concept of “high-quality TTM” as a way to increase the effectiveness of TTM and standardize its use in future interventional studies.

Factors associated with the provision of targeted temperature management: A balanced factorial experiment

AIM

This study examined the influence of patient attributes and provider or organizational factors on the decision to apply targeted temperature management (TTM) to resuscitated out-of-hospital cardiac arrest (OHCA) patients.

METHODS

A balanced factorial experiment was conducted among emergency medicine physicians (EMPs). Sixteen OHCA patient scenarios with balanced factors were presented. The balancing factors were dichotomous categories of patient age (45 ± 2 vs. 70 ± 2 years), patient sex (men vs. women), socioeconomic status (SES; higher vs. lower), and guardian attitudes (positive vs. reluctant) regarding TTM. Information on participant and organizational characteristics was collected. The outcome variable was a score (0-100) based on responses to questions that indicated how likely the participants were to apply TTM.

RESULTS

Seventy-five EMPs completed the experiment. The median score for the likelihood of TTM application was 85 (interquartile range, 70-95). Scores differed significantly for patient age (90% vs. 80%, p = 0.001), SES (90% vs. 80%, p = 0.001), and guardian attitude regarding TTM (90% vs. 70%, p = 0.001). The likelihood of TTM application was associated with EMP experience with TTM (more or <50 times) (90% vs. 80%, p = 0.001). EMPs working in hospitals with commercial TTM devices or operating protocols were more likely to use TTM than those working in hospitals without TTM devices or protocols (88 vs. 80 and 90 vs. 80; p = 0.001, respectively).

CONCLUSION

Patient demographics and provider and organizational factors significantly affected the decision to apply TTM.

Therapeutic Hypothermia and Targeted Temperature Management for Traumatic Arrest and Surgical Patients

Therapeutic hypothermia (TH) and targeted temperature management (TTM) have been shown to improve outcomes in survivors of cardiac arrest, but prior research has excluded trauma and postoperative patients. We sought to determine whether TH/TTM is safe in trauma and surgical patients. A retrospective cohort study was conducted at a single level I trauma center reviewing adults presenting as a traumatic arrest or cardiac arrest in the postoperative period with a Glasgow Coma Scale <8 after return of circulation who were treated with either TH or TTM. Neurological recovery is considered favorable if a patient was discharged following commands. A total of 32 cardiac arrest patients were included in the study, 14 of whom were treated with TH and 18 with TTM protocols, with goal temperatures of 33°C and 36°C, respectively. Mean age of the cohort was 60 ± 13, with 26 (81%) men. There were 18 trauma patients and 14 postoperative patients. Complications included pneumonia (13%), sepsis (6%), bleeding requiring transfusion (22%), arrhythmias (6%), and seizures (9%), which are similar to prior published series. Overall survival to discharge was 41% (n = 13), and all survivors had favorable neurological recovery. Traumatic arrest and perioperative cardiac arrest patients previously excluded from TH/TTM studies appear to have an acceptable incidence of complications compared with standard TH/TTM patients.

Precise Control of Target Temperature Using N6-Cyclohexyladenosine and Real-Time Control of Surface Temperature

Targeted temperature management is standard of care for cardiac arrest and is in clinical trials for stroke. N⁶-cyclohexyladenosine (CHA), an A₁ adenosine receptor (A₁AR) agonist, inhibits thermogenesis and induces onset of hibernation in hibernating species. Despite promising thermolytic efficacy of CHA, prior work has failed to achieve and maintain a prescribed target core body temperature (T_b) between 32°C and 34°C for 24 hours. We instrumented Sprague-Dawley rats (n = 19) with indwelling arterial and venous cannulae and a transmitter for monitoring T_b and ECG, then administered CHA via continuous IV infusion or intraperitoneal (IP) injection. In the first experiment (n = 11), we modulated ambient temperature and increased the dose of CHA in an attempt to manage T_b. In the second experiment (n = 8), we administered CHA (0.25 mg/[kg·h]) via continuous IV infusion and modulated cage surface temperature to control T_b. We rewarmed animals by increasing surface temperature at 1°C h^-1 and discontinued CHA after T_b reached 36.5°C. T_b, brain temperature (T_brain), heart rate, blood gas, and electrolytes were also monitored. Results show that titrating dose to adjust for individual variation in response to CHA led to tolerance and failed to manage a prescribed T_b. Starting with a dose (0.25 mg/[kg·h]) and modulating surface temperature to prevent overcooling proved to be an effective means to achieve and maintain T_b between 32°C and 34°C for 24 hours. Increasing surface temperature to 37°C during CHA administration brought T_b back to normothermic levels. All animals treated in this way rewarmed without incident. During the initiation of cooling, we observed bradycardia within 30 minutes of the start of IV infusion, transient hyperglycemia, and a mild hypercapnia; the latter normalized via metabolic compensation. In conclusion, we describe an intravenous delivery protocol for CHA at 0.25 mg/(kg·h) that, when coupled with conductive cooling, achieves and maintains a prescribed and consistent target T_b between 32°C and 34°C for 24 hours.