Nielsen N et al. Targeted temperature management at 33°C versus 36°C after cardiac arrest. N Engl J Med Nov 17 2013 (full text here)
In this RCT, 950 out of hospital cardiac arrest patients (VF and other) were randomised into targeted temperature management (TTM) at either 33°C or 36°C for 36 hours post arrest. There was no difference in all-cause mortality (primary endpoint) or a composite of poor neurologic outcome or death at 180 days (secondary endpoint). One of the proposed reasons this differs from the initial studies in 2002 (Bernard et al and HACA) that started the whole therapeutic hypothermia institution is that the control group in this trial were kept normothermic (ie not allowed to go febrile), whereas in the prior trials the control group had no temperature control.
Kim F, Nichol G, Maynard C, et al. Effect of Prehospital Induction of Mild Hypothermia on Survival and Neurological Status Among Adults With Cardiac Arrest: A Randomized Clinical Trial. JAMA. Nov 17 2013 (full text here)
In this trial, 1359 patients with cardiac arrest (VF and other) and ROSC were randomised to receive standard prehospital care with or without cooling, via 2L of 4°C normal saline whilst en route to hospital. Nearly all VF patients received in-hospital cooling. Despite reaching target temperature sooner, there was no difference in survival to hospital discharge (primary endpoint) or good neurological outcome (secondary endpoint) in both VF and non-VF arrests. There was a higher rate of re-arrests and pulmonary oedema on first CXR in patients receiving cooling.
A Warm Change is Coming...
An inside word - the ICU at the RAH is looking to change TTM in the post cardiac arrest care protocol from 33°C to a new target of 36°C, with prognostication at 72 hours post cooling. Avoidance of fever with active cooling will be included. FMC are also looking at changing their protocol.
This probably means that we will no longer be cooling in ED - watch this space.
In addition, SAAS have been taking part in a pre-hospital cooling trial that is now uncertain to continue, especially since we'd just end up warming them up once they arrive.