Presented at the Neonatal Society 2007 Summer Meeting.

Kapetanakis A¹, Iwata S¹, Olson L², Iwata O¹, Kato T¹, Samantha Evans S¹, Setterwall F³, Lagercrantz H², Robertson NJ¹

¹ Centre for Perinatal Brain Research, EGA UCL Institute for Women’s Health, University College London, UK
² Department of Woman and Child Health, Karolinska Institute, Stockholm, Sweden
³ Dept of Chemical Engineering, Royal Institute of Technology, Stockholm, Sweden

Background: Therapeutic hypothermia shows promise as a potent therapy in neonatal encephalopathy (NE) in a developed world setting (1,2). As NE rates are considerably higher in low-resource settings, designing safe, low-tech methods may have beneficial impact globally.

Aim: To assess the application and cooling characteristics of two low tech cooling methods: Group a) commercially available water bottles (WB) filled with tepid water (25ºC); Group b) phase changing material (PCM) mattress (melting point 32ºC – PCM works as a heat buffer and thus stabilizes the temperature of whatever is in contact with it close to its set melting point); in an experimental porcine model of NE (in accordance with Home Office licence).

Methods: Rectal Temperature (Tr) was monitored following transient hypoxia-ischaemia (HI) in 6 anesthetized (isoflufane) with newborn piglets (group a; n=2, group b; n=4). Hypothermia was instituted 2-26 hours after HI followed by gradual rewarming. The target Tr was 33-35ºC. Tr was adjusted using cotton blankets or replacing the cooling device when Tr > 35ºC.

Results: Therapeutic hypothermia was achieved in all groups although the cooling characteristics differed. Tr reached 34ºC in (a)1.8h and 1.3h and (b) (mean(SD)) 2.3 (0.7h). Brief Tr undershoot below 33ºC preceded the stable hypothermic period (Fig). Gradual rewarming at ~0.5ºC/hr was achieved by removing the cooling source in a) and b) Tr deviations and the number of required manipulations to maintain a stable Tr are shown in the Table.

Conclusion: Simple cooling modalities can induce and maintain mild-moderate hypothermia effectively in a porcine model of NE. PCM may require fewer adjustments compared to WB although may be less flexible in target Tr. Safe and effective cooling in low-resouce settings requires standardised protocols, adequate staffing levels and appropriate monitoring.

References
1. Shankaran S, Laptook AR, Ehrenkranz RA, et al. N Engl J Med 2005;353(15):1574-84
2. Gluckman PD, Wyatt JS, Azzopardi D, et al. Lancet 2005;365(9460):663-70.