Changes in the PQRST intervals and heart rate variability associated with rewarming in two newborns undergoing hypothermia therapy.
BACKGROUND
Little is known about the effects of hypothermia therapy and subsequent rewarming on the PQRST intervals and heart rate variability (HRV) in term newborns with hypoxic-ischemic encephalopathy (HIE).


OBJECTIVE
This study describes the changes in the PQRST intervals and HRV during rewarming to normal core body temperature of 2 newborns with HIE after hypothermia therapy.


METHODS
Within 6 h after birth, 2 newborns with HIE were cooled to a core body temperature of 33.5 degrees C for 72 h using a cooling blanket, followed by gradual rewarming (0.5 degrees C per hour) until the body temperature reached 36.5 degrees C. Custom instrumentation recorded the electrocardiogram from the leads used for clinical monitoring of vital signs. Generalized linear mixed models were calculated to estimate temperature-related changes in PQRST intervals and HRV.


RESULTS
For every 1 degrees C increase in body temperature, the heart rate increased by 9.2 bpm (95% CI 6.8-11.6), the QTc interval decreased by 21.6 ms (95% CI 17.3-25.9), and low and high frequency HRV decreased by 0.480 dB (95% CI 0.052-0.907) and 0.938 dB (95% CI 0.460-1.416), respectively.


CONCLUSIONS
Hypothermia-induced changes in the electrocardiogram should be monitored carefully in future studies.
Lasky
Robert E
RE
Division of Neonatal-Perinatal Medicine, Department of Pediatrics and Center for Clinical Research and Evidence-Based Medicine, University of Texas Medical School, Houston, TX 77030, USA. Robert.E.Lasky@uth.tmc.edu
Parikh
Nehal A
NA
Williams
Amber L
AL
Padhye
Nikhil S
NS
Shankaran
Seetha
S
D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D001831:Body Temperature; D003080:Cold Temperature; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D007036:Hypothermia, Induced / Q000009:adverse effects*; D020925:Hypoxia-Ischemia, Brain / Q000628:therapy; D007231:Infant, Newborn; D017694:Rewarming / Q000009:adverse effects*