Key result
During rewarming of newborns with HIE, every 1°C increase in body temperature was associated with a 9.2 bpm increase in heart rate and a 21.6 ms decrease in the QTc interval.
Why the study?
How does rewarming after hypothermia therapy affect PQRST intervals and heart rate variability in newborns with hypoxic-ischemic encephalopathy?
Case Report (n=2)
How does rewarming after hypothermia therapy affect PQRST intervals and heart rate variability in newborns with hypoxic-ischemic encephalopathy?
Mean Difference: 9.2 (95% CI 6.8–11.6)
Rewarming after hypothermia therapy in newborns with HIE is associated with significant increases in heart rate and decreases in QTc interval and heart rate variability.
Describes ECG/HRV changes during rewarming in two HIE neonates; hypothesis-generating and should not yet change practice.
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). OBJECTIVES: 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.
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Lasky et al. (2009) conducted a case report in Hypoxic-ischemic encephalopathy (HIE) (n=2). Rewarming was evaluated on Change in heart rate per 1 degrees C increase in body temperature (MD 9.2 bpm, 95% CI 6.8-11.6). During rewarming of newborns with HIE, every 1°C increase in body temperature was associated with a 9.2 bpm increase in heart rate and a 21.6 ms decrease in the QTc interval.
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