Determination of Reference Intervals for Umbilical Cord Arterial and Venous Blood Gas Analysis of Healthy Thoroughbred Foals

Abstract

Abstract Although umbilical cord blood gas analysis is considered the best way to assess in utero oxygenation in human neonates, there is limited evaluation of this method in equine neonatology. Our objectives were to assess the practicality of obtaining umbilical cord blood gas samples in the field and to determine umbilical cord arterial and venous blood gas reference intervals (RI) for healthy, newborn foals. Thoroughbred foals >320 days gestation from healthy mares with uneventful pregnancies at one stud farm were evaluated. All parturitions were observed, with paired umbilical arterial and venous whole-blood samples obtained immediately following parturition for blood gas and lactate concentrations measured in duplicate. Apgar scores were assigned immediately and 10 min after birth, with all foals subsequently examined on days 1–28 to monitor for development of perinatal asphyxia syndrome. Foals were excluded from analysis based on abnormalities of stage 2 labour, Apgar scores and gross and histological placental assessment. Data was analysed using a Student's t-test, Pearson's correlation and the Robust method with P ≤ 0.05 significant. Umbilical cord samples were simple to obtain with minimal disruption to the foaling environment. Of the n = 34 foals assessed, n = 7 were excluded based on premature placental separation deliveries. The mean time for stage 2 labour and blood gas analysis after parturition was 17.3 ± 5.1 min and 5.0 ± 2.3 min, respectively. RI were identified for umbilical arterial and venous pH (7.19–7.42 vs. 7.34–7.44), PO2 (15.5–48.39 mmHg vs. 16.6–52.7 mmHg), PCO2 (49.5–82.29 mmHg vs. 45.4–63.1 mmHg), SO2 (9.19–76.89% vs. 39.9–84.88%), bicarbonate (27.3–38.7 mmol/l vs. 27.7–37.8 mmol/l), base excess (0.36–12.9 mmol/l vs. 1.97–13.1 mmol/l), TCO2 (28.99–40.3 mmHg vs. 29.0–39.5 mmHg) and lactate (1.4–7.3 mmol/l vs. 1.3–4.9 mmol/l). Umbilical arterial samples had lower pH (P