Effect of pre-warming on paediatric patients presenting for magnetic resonance imaging under general anaesthesia

Abstract

Background: The combination of anaesthesia and environmental factors in the magnetic resonance imaging (MRI) suite increases patient susceptibility to hypothermia. Pre-warming patients with a forced-air warmer prior to anaesthesia has been shown to decrease the incidence of peri-operative hypothermia. This study aimed to determine whether pre-warming paediatric patients presenting for MRI under general anaesthetic prevented them from developing hypothermia. Methods: A prospective, quasi-experimental research design was followed. A total of 102 patients were enrolled during the 4-month study period and were divided equally into pre-warmed and control groups. Inclusion criteria were patients aged 6 months to 6 years, ASA physical status I or II and with written informed consent from a caregiver. The pre-warmed group received 30 minutes of active warming with a forced-air warmer. The MRI examination was conducted using a volatile-based general anaesthetic. Tympanic temperatures were measured at baseline, pre-scan and post-scan. Results: The pre-warmed group received an average (SD) of 34.8 (4.3) minutes of warming. The median (IQR) time spent inside the MRI unit was 60 (50 to 77) minutes. The incidence of hypothermia was 1.96%. The pre-warmed group had a statistically significant increase of 0.3°C in core body temperature (CBT) compared to the control group following the pre-warming period (p=0.0001). There was a statistically significant difference in CBT between the pre-warmed and control groups (0.15°C; p=0.0001). A weak negative correlation between patient weight and temperature change (r=-0.220, p=0.026) and between length of time of pre-warming and temperature change (r=-0.268, p=0.006) was found.

Conclusions: The effect of pre-warming to prevent hypothermia under general anaesthetic in the MRI unit could not be established due to the low incidence of hypothermia. Pre-warming patients for a period of 30 minutes prevented a statistically significant decline in CBT compared to the control group, however, this finding was not clinically significant.