Kim Annink

223 Measurement of brain temperature using MRS measurements before, during and after MRI, followed by post-hoc comparison with Wilcoxon-signed rank test when differences were statistically significant. Lastly, multivariable linear regression analysis was performed to explore the association between therapeutic hypothermia and head circumference as independent variables and the difference between rectal temperature before MRI and the brain temperature during MRI as dependent variable, because these might be factors that influence the risk of cooling down during MRI. p-values <0.05 were considered statistically significant. All p-values have been corrected for multiple comparisons by multiplying the p-value with the number of performed tests. RESULTS Subjects Between December 2011 and June 2017, 49 patients with NE, who were treated with therapeutic hypothermia, had 1 H-MRS and temperature data available. Of those patients, 13 patients were excluded because of insufficient quality of the 1 H-MRS data. So, 36 patients were included in the study. Table 1 shows the baseline characteristics of the included infants. Usually patients were scanned during or after the rewarming process following therapeutic hypothermia (body temperature >35.5˚C). Seven infants had an MRI during therapeutic hypothermia or early rewarming for clinical reasons. In one infant scanned during rewarming, therapeutic hypothermia was stopped before the MRI was conducted and therefore the temperature is higher at the end of the MRI. Table 1: Baseline characteristics for the two temperature groups during MRI. Characteristic Normothermic (n=29) Hypothermia (n=7) Male sex, n (%) 15 (51.7) 5 (71.4) Gestational age in weeks, median (IQR) 40.0 (38.6 – 40.9) 39.7 (37.6 – 40.0) Birth weight in grams, median (IQR) 3500 (2976 – 3889) 3170 (3100-3575) Head circumference in cm, median (IQR) 35.0 (32.9 – 36.0) 35.0 (33.0 – 35.3) Apgar score at 5 minutes, median (IQR) 4.0 (2.8 – 5.0) 4.5 (1.0 – 8.8) Apgar score at 10 minutes, median (IQR) 5.0 (4.0 – 7.0) 5.0 (4.0 – 5.0) Postnatal age at MRI in hours, median (IQR) 131.7 (115.0 –152.3) 85.8 (65.7 – 94.0) Peripheral Temperature before MRI in ˚C, median (IQR) 36.8 (36.6 – 37.1) 33.6 (33.4 – 34.3) 10