119 - Impact of Whole Body Hypothermia and Oxygenation on Pulmonary Hemodynamics in MAS, PPHN and HIE.

Monday, May 1, 2023

9:30 AM – 11:30 AM ET

Poster Number: 119
Publication Number: 119.427

Kirstie C. Tully, University of California, Davis, School of Medicine, Dixon, CA, United States; Amy Lesneski, University or California, Davis, Davis, CA, United States; Morgan Hardie, UC Davis, Davis, CA, United States; Houssam Joudi, University of California, Davis, Torrance, CA, United States; Victoria Hammitt, University of California, Davis, School of Medicine, Sacramento, CA, United States; Evan M. Giusto, UC Davis Health, Sacramento, CA, United States; Rebecca Valdez, University of California, Davis, School of Medicine, Davis, CA, United States; Deepika Sankaran, University of California, Davis, School of Medicine, Sacramento, CA, United States; Payam Vali, University of California, Davis, School of Medicine, sacramento, CA, United States; satyanarayana Lakshminrusimha, UC Davis Children's Hospital, Sacramento, CA, United States

Presenting Author(s)

KT

Kirstie C. Tully, BS (she/her/hers)

Staff Research Associate 3
University of California, Davis, School of Medicine
Dixon, California, United States

Background: Whole body hypothermia is standard of care in neonates with moderate to severe hypoxic ischemic encephalopathy (HIE). Almost 25% of cases of HIE are associated with persistent pulmonary hypertension of the newborn (PPHN), often secondary to meconium aspiration syndrome (MAS). The precise interaction between body temperature, oxygen saturation (SpO2) targets and pulmonary blood flow (Qp) is not known.

Objective: To compare the combined effect of oxygenation and body temperature on Qp in lambs with MAS, HIE and PPHN.

Design/Methods: _{Term fetal lambs (139-141d gestation, n=76) were instrumented, and asphyxia was induced by umbilical cord compression for 10min. The tracheal tube was filled with 20% solution of meconium in amniotic fluid that was aspirated into the lung during fetal gasping. Lambs were delivered and stabilized and randomized to preductal SpO2 target of 90-94% (low target) or 95-99% (high target) and ventilated for 6h. During this period, they received hypothermia (rectal target temperature of 33.5°C) for 3h and normothermia for 3h in random order. Plasma oxidative stress (xanthine/hypoxanthine) was analyzed at baseline and at the end of hypothermia and normothermia.}

Results: Baseline characteristics of lambs were similar between the two SpO2 target groups (table 1). At both SpO2 targets, preductal PaO2 values (corrected for temperature) were lower during hypothermia compared to normothermia although there was no difference in oxygen saturation by co-oximetry SaO2 between hypothermia and normothermia (table 2). Achieved SpO2 was lower than expected due to some lambs being hypoxemic despite FiO2 of 1.0. Pulmonary blood flow was significantly lower during hypothermia compared to normothermia in the high target group (table 2). There was no difference in hypoxanthine/xanthine ratios between the two temperature and SpO2 target groups. Due to differences in PaO2 between two groups, we pooled all data and analyzed Qp in different PaO2 ranges (figure 1). Qp increased with increasing PaO2 in both normothermia and hypothermia and was lower with hypothermia in high SpO2 target compared to normothermia. At PaO2 range 50-70 mmHg, Qp was significantly lower with hypothermia. No significant difference was observed when PaO2 was 70-100 mmHg.

Conclusion(s): In lambs with HIE, MAS and PPHN, whole body hypothermia to 33.5°C decreases temperature-corrected PaO2 (possibly due to shift of hemoglobin-oxygen dissociation curve) and reduces pulmonary blood flow, especially at SpO2 target 95-99%. Targeting higher preductal PaO2 (and not just SpO2) needs to be studied in management of PPHN during hypothermia.