Targeted Temperature Management; efficacy, duration, and the optimal method of implementation on OHCA patients

Abstract

Background: Out-of-hospital cardiac arrest (OHCA) is associated with a high mortality rate and poor neurological function. Targeted temperature management (TTM) is a modality used with comatose survivors to attenuate the secondary brain injury and improve survival rate. However, the evidence base behind this intervention is generally low. Furthermore, the optimal method and interval period for which to implement this intervention have not been well defined. Aims of the study: The principal aim of the study is to identify the benefits of implementing TTM on OHCA patients in relation to the rate of mortality and neurological outcomes. Additionally, the study aims to determine the ideal cooling interval and the optimal method to perform the procedure. Method: A systematic search was conducted in the following databases: PubMed, Cochrane Library database, and the U.S National Library of Medicine (Clincaltrials.gov). Solely prospective, randomised, and quasi-randomised controlled trials were included. Results: The search yielded 318 citations of which 7 articles met the systematic inclusion criteria. Two RCTs found superior survival and neurologic outcomes of mild hypothermia compared to normothermia for patients with shockable rhythms. The largest paper included contrasted the implementation of 33°C to 36°C temperature ranges and failed to detect any significant difference measuring the same outcomes. For patients with non-shockable rhythms, one study found and indicated comparable mortality rate, but significant favourable neurologic functions in the TTM arm. One trial compared a 24h period of cooling to 48h and revealed insignificant mortality and neurological outcomes. One small RCT compared the use of the Arctic Sun device with a standard cooling blanket as modalities to perform TTM. However, no significant variation was identified in either the mortality rate or the neurological function, this was despite the fact the use of the Artic Sun device has been identified as a more efficient technique. The final paper compared the use of an intravascular catheter to external basic methods and reported a similar mortality rate at 90 days, but superior neurologic outcomes in favour of the intravascular catheter. Conclusion: Mild therapeutic hypothermia improves survival rate and neurological outcomes for OHCA comatose patients presenting with initial shockable rhythms, specifically if it is compared with no temperature control. At this stage, the optimum TTM administration length is unknown. The intravascular catheter and implementation of surface cooling by the Arctic Sun device appeared to be more efficient in implementing TTM compared to conventional techniques. However, the intravascular catheter only showed a high probability of neurological recovery.