Introduction

Hypothermia is currently recognized as the only therapy that has been demonstrated in rigorous randomized controlled trials to alter the outcome of late preterm and term infants with evidence of hypoxia–ischaemia accompanied by encephalopathy [1–6]. Hypothermia is a broad term when used in clinical care and can span profound reductions in temperature used for repair of congenital heart defects [7] to very mild reductions in temperature beyond the thermal neutral zone among infants with cold stress at birth [8]. Hypothermia as investigated for treatment of hypoxic–ischaemic encephalopathy (HIE) refers to a targeted temperature reduction regimen and is characterized by sequential phases of induction, maintenance and rewarming whereby each phase has specific temperature characteristics. There are currently two principal methods to achieve targeted temperature reduction: selective cooling with mild systemic hypothermia or whole body cooling. The following is an overview of whole body cooling which was used in four of the six large randomized trials of this therapy. This report will focus on two of the trials that used whole body cooling, the NICHD Body Cooling Trial [2] and the Total Body Hypothermia for Neonatal Encephalopathy Trial (TOBY) [3], since they share many similarities but also some differences. These two trials will be used as a template for discussion of specific aspects of this mode of therapeutic hypothermia and will provide an overview of whole body cooling to emphasize important background, rationale, implementation, monitoring and potentially unrecognized caveats regarding this therapy.