Acute hypoxic brain injury in singleton term fetuses: Factors associated with a low pH

Abstract

CIATED WITH A LOW PH JEFFREY PHELAN, LISA KORST, GILBERT MARTIN, Childbirth Injury Prevention Foundation, Pasadena, California, University of Southern California, Obstetrics and Gynecology, Los Angeles, California, University of California, Irvine, Pediatrics, Orange, California OBJECTIVE: To describe the clinical characteristics associated with low umbilical artery pH in fetuses with acute hypoxic brain injury. STUDY DESIGN: Data were obtained from a registry of singleton term liveborn neonates with permanent brain injury due to hypoxic-ischemic encephalopathy. Cases were included if the FHR was reactive on admission, followed by a sudden, rapid, and sustained deterioration that lasted until delivery and an umbilical cord artery pH. pH ! 6.7 was defined as ‘‘low.’’ Intrafetal shunting(IFS) was defined as any one of the following: CPK O 300, SGOT or SGPT O 100 U/L, platelet count ! 150,000 within 5 days of life, creatinine R 1.5 mg/dl, urine output ! 1 cc/kg/hr on day 1 of life. The deceleration onset to delivery(D-D) time relationship to the pH was determined. A multivariate logistic regression model was used to examine the independent association of a variety of clinical characteristics with a low pH. RESULTS: Of 39 eligible cases, sentinel hypoxic events occurred in 31(79%):uterine rupture with or without abruption, 26(84%);Other5(16%);none, 8 (21%). The mean D-D Time:31.53 G 9.45 minutes, median 30.00, range (15.00-57.00). The mean pH was 6.73 G 0.11, median 6.70, range (6.58-7.08), and 17 neonates (43.6%) had a low pH. A logistic regression model (P = 0.0083) yielded the following OR and 95%CI for the clinical characteristics tested: D-D Time O 30 minutes: 2.524 (0.586-13.108); repetitive decelerations or tachycardia prior to FHR deterioration: 3.127 (0.541-18.084); IFS: 1.603 (0.292-8.802); abruption: 3.546 (0.700-17.948), and fetal and/or placental expulsion: 8.669 (1.504-49.960). There was no statistical difference in the D-D Time between those neonates with and without a low pH: 32.45 G 11.99 minutes, median 29.00, range (16.00-57.00) vs. 30.38 G 4.87 minutes, median 30.00, range (19.00-41.00), P = 0.1122. CONCLUSION: Low umbilical artery pH in term neonates with acute brain injury does not appear to be associatedwith a predictable decline in the pHbut, is primarily associated with uterine rupture with fetal and/or placental expulsion.