082 - Core temperature gradient during therapeutic hypothermia is associated with hemodynamic changes in neonates with hypoxic ischemic encephalopathy

Publication Number: 82.4524

Jayde Fernandez, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States; Tai-Wei Wu, University of Southern California, Keck School of Medicine, Los Angeles, CA, United States; Eni Jano, Children's Hospital Los Angeles, Los Angeles, CA, United States

Background: Whole-body cooling (WBC) is achieved by servo-controlling core body temperature at the esophagus or rectum to 33.5 degrees Celsius. However, simultaneous measurement of esophageal and rectal temperatures reveals a core body temperature gradient. In general, esophageal temperature is higher than rectal temperature during cooling. We hypothesize that hemodynamic changes are associated with core temperature differences.

Objective: We aim to study the hemodynamic changes associated with esophageal-rectal temperature gradient.

Design/Methods: This is a prospective observational study where 63 infants (48 moderate and 15 severe) underwent WBC with simultaneous esophageal and rectal temperature monitoring. WBC was servo-controlled to esophageal temperature in 30 infants (E-group) and to rectal temperature in 33 infants (R-group). Hourly esophageal, rectal temperature, and hemodynamic variables (heart rate-HR, blood pressure-BP, cerebral regional oxygenation-CrSO2, renal regional oxygenation-RrSO2) were collected during the 72 hour of WBC and divided into 3 periods (1-24, 25-48, and 49-72 hours). E-R gradient was calculated as esophageal minus rectal temperature. Repeated measures correlation (rmcorr) was performed to determine the association between E-R gradient and hemodynamic variables, accounting for within-subject variability.

Results: E-group and R-group methods of WBC produced different temperature profiles, Figure1. Mean E-R gradient was 0.5 +/- 1.1Celsius (1-24h), 0.5+/-0.6 C (25-48h), and 0.2+/- 0.4C in the E-group and 0.2+/-0.6C (1-24h), 0.2+/-0.4C (25-48h), 0.2+/-0.5C (48-72h). Repeated measures correlation analysis reveals a weak, but significant positive correlations between E-R gradient and HR, BP, CrSO2, and CrSO2-RrSO2 gradient. There was also a significant negative correlation between E-R gradient and RrSO2, Figure 2. In summary, the magnitude of esophageal-rectal temperature gradient was associated with in increases in HR, BP, CrSO2, and decrease in RrSO2.

Conclusion(s): Duo-site temperature monitoring during whole-body cooling reveals differences in core body temperatures. Core body temperature gradient is associated with hemodynamic changes that suggest shunting of blood flow from non-vital to vital organ. Further studies are needed to investigate the impact of the hemodynamic changes during hypothermic neuroprotection.

Figure 1. Core temperature profile in infants undergoing whole body cooling
The mean esophageal temperature is higher than rectal temperature during cooling but is reversed during rewarming. Core body temperature gradient exists in both esophageal and rectal group.

Table 1. Repeated measures correlation (r) between esophageal-rectal temperature gradient and hemodynamic parameters

Results are presented in repeated measures correlation r, [95% confidence intervals]. Bald numbers denote significance, p<0.05. *denotes p<0.01. HR: heart rate (bpm); MBP: mean blood pressure (mmHg); SBP: systolic blood pressure; DBP: diastolic blood pressure; CrSO2: regional cerebral oxygenation(%), RrSO2: regional renal oxygenation (%).

Figure 2. Sample repeated measures correlation plot for regional renal oxygenation vs. esophageal-rectal temperature gradient
This plot illustrates the relationship that increased esophageal-rectal temperature gradient is associated with a reduction in regional renal oxygenation or a reduction in renal blood flow.