Measurement of temperature change in paediatric patients undergoing MRI examinations under general anaesthesia
Background and objectives of study: Paediatric patients undergoing Magnetic Resonance Imaging (MRI) procedures are at risk of hypo- or hyperthermia. This study was aimed at determining if there is a change in core temperature in paediatric patients undergoing MRI examinations under general anaesthesia. The objectives included describing the change in temperature during MRI scans, and correlating temperature change with age, weight and MRI scan duration. Method: This study followed a prospective, contextual and descriptive research design. The study population was paediatric patients who presented for MRI scans under general anaesthesia at Chris Hani Baragwanath Academic Hospital. A convenience, consecutive sampling method was employed and 29 patients aged 6 months to 5 years whose baseline temperatures were below 37.5℃ participated in the study. Tympanic temperature was measured using an infrared thermometer before induction of general anaesthesia. Inhalational general anaesthesia was induced with incremental concentrations Sevoflurane in a mixture of Nitrous oxide and Oxygen (70:30 %) using an MRI compatible anaesthesia machine. General anaesthesia was maintained with spontaneous inhalation of Sevoflurane in a mixture of O₂ and Air (60:40 %) via a laryngeal mask airway. Tympanic temperature was measured again on completion of the MRI scan within 2 minutes of emergence from general anaesthesia. The change between pre and post scan temperatures was tested for significance using the paired t-test. Correlations were made using the Pearson correlation coefficient. Results: The mean age of the participants was 31 months and the median 24 months. The mean weight was 13.2 kg, the median 12 kg, and the range 5 to 29 kg. The mean MRI scan duration was 51 minutes, the median 50 minutes and range 30 minutes to 80 minutes. All participants experienced some loss of temperature (0.1 – 2.3 ℃). The mean temperature loss was 0.93℃ and was statistically significant (p=0.001). The 95% confidence interval for temperature change was 0.70 – 1.15 ℃. No statistically significant correlations were found between temperature loss and age (r=-0.028), weight (r=-0.042) and scan duration (r=-0.041). Conclusion: Heat loss in the harsh MRI environment is an underestimated problem. In addition, the ferromagnetic environment precludes continuous temperature monitoring. This study has shown that temperature does drop in paediatric patients undergoing MRI examinations under general anaesthesia. This change in temperature did not correlate with age, weight, and duration of the MRI scan.
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Masters of Medicine in Anaesthesia Johannesburg, 2014