The effect of temperature on the QTc interval in the newborn infant receiving extracorporeal membrane oxygenation (ECMO).

OBJECTIVE: To explore the changes in the QTc interval during mild hypothermia in neonates receiving extracorporeal membrane oxygenation (ECMO). DESIGN: Twenty seven neonates (median gestation 40 weeks; range 33-41 weeks) enrolled in a pilot study of mild hypothermia were studied during the first five days of ECMO. The first group (N=7) were maintained at 37 degrees C throughout the study period. Subsequent groups (N=5) were cooled to 36 degrees C, 35 degrees C and 34 degrees C respectively for twenty four hours and the final group to 34 degrees C for forty eight hours before being rewarmed to 37 degrees C. Using a 24 h digital monitor, the QT and QTc intervals were recorded continuously during the cooling and rewarming period and validated using standard 12 lead electrocardiograms. Patients were carefully assessed clinically and routine biochemistry (including magnesium and calcium) laboratory tests measured pre ECMO and at timed intervals during cooling and rewarming. RESULTS: The mean difference between the continuous digital and 12 lead ECG values for QTc was -13.3 ms. During the first 24 h of cooling, the mean (95th centile) values for the digitally measured QTc interval at 37 degrees C=431(506) milliseconds (ms); 36 degrees C=459(521) ms; 35 degrees C=445(516) ms; 34 degrees C=465(531) ms; 34 degrees C for 48 h=466(521) ms. During this period overall QTc increased by 3.12 ms (95% confidence intervals 6.17 to 0.84; p=0.04) for each degree fall in body temperature. During rewarming, there was no significant relationship between QTc and temperature change. No serious arrhythmias were during cooling. Using univariate analysis, no relationship was found between QTc and electrolytes, heart rate and blood pressure. CONCLUSIONS: QTc shows significant variability in individuals, and only a small proportion of this can be explained by rectal temperature. Mild hypothermia was not associated with serious cardiac arrhythmias.

Lack of influence of mild hypothermia on amplitude integrated-electroencephalography in neonates receiving extracorporeal membrane oxygenation.

OBJECTIVE: To observe amplitude integrated electroencephalography (aEEG) in neonates receiving ECMO and to determine whether mild hypothermia influenced the aEEG recording. METHODS: Twenty-six consecutive neonates enrolled in a pilot study of mild hypothermia during ECMO were studied. The first group (N=6) was maintained at 37 degrees C throughout the study period. Subsequent groups were cooled to 36 degrees C (N=4), 35 degrees C (N=5), and finally 34 degrees C (N=6) respectively for 24 h and the final group (N=5) to 34 degrees C for 48 h before being rewarmed to 37 degrees C. The aEEG was recorded continuously during the first 5 days of ECMO. The aEEG was classified as normal, moderately or severely suppressed and examined for the occurrence of seizures. To assess the effect of temperature, the aEEG was compared over 12 h during the final 6 h of cooling and during the first 6 h once infants were rewarmed. RESULTS: No change in aEEG amplitude was noted over the temperature range studied. Of the 26 traces obtained, 16 (62%) were normal throughout, 6 (23%) were intermittently moderately abnormal and 1 (14%) was severely abnormal. Three (11%) traces had periods of frequent seizure activity and these were not associated with clinical manifestations in two neonates. In one infant who suffered a cerebral haemorrhage, the aEEG became abnormal before cranial ultrasound abnormalities were apparent. CONCLUSIONS: Continuous cerebral monitoring with aEEG is feasible during ECMO and may add information to clinical examination. Mild hypothermia to 34 degrees C for up to 48 h does not influence the aEEG suggesting that cerebral monitoring with aEEG is possible during mild hypothermia.

A pilot investigation of mild hypothermia in neonates receiving extracorporeal membrane oxygenation (ECMO).

OBJECTIVE: To investigate the safety and feasibility of using mild hypothermia in neonates receiving extracorporeal membrane oxygenation (ECMO). Study design A prospective, nonrandomized pilot study of 25 neonates referred for ECMO. Whole body cooling was achieved by adjustment of the temperature of the extracorporeal circuit water bath. Five groups (N=5 per group) were each studied for the first 5 days of ECMO. The first group was maintained at 37 degrees C throughout the study period. Subsequent groups were cooled to 36 degrees C, to 35 degrees C, and, finally, to 34 degrees C, respectively, for 24 hours and the final group to 34 degrees C for 48 hours before being rewarmed to 37 degrees C. Patients were carefully assessed clinically and biologically. In addition to routine laboratory tests, cytokines (IL-6 and IL-8), complement (C3a), and molecular markers of coagulation (thrombin/antithrombin III [TAT], antithrombin III, and plasmin-alpha2plasminogen) were measured. RESULTS: No major clinical or circuit problems were noted during cooling or rewarming. In particular, there were no problems of bleeding or cardiac arrhythmia. No significant difference was found between groups in terms of molecular markers of coagulation, complement, cytokines, and platelet transfusions. CONCLUSIONS: Applying mild hypothermia (34 degrees C) for 24 or 48 hours to neonates receiving ECMO is both feasible and safe.