LACTATE COMPARED WITH PH ANALYSIS AT FETAL SCALP BLOOD-SAMPLING - A PROSPECTIVE RANDOMIZED STUDY

Objective Fetal scalp blood sampling is a widely used method for asses sing fetal condition in the event of ominous fetal heart rate patterns . The purpose of this randomised trial was to compare the value of fet al scalp blood lactate and pH management in cases of abnormal intrapar tum fetal heart rate tracings. Methods Of 341 cases of ominous fetal h eart rate patterns, 169 were randomly assigned to pH analysis, and 172 to lactate measurements. Lactate was measured using a lactate card re quiring 5 mu L of blood and yielding the result within 60 seconds. pH analysis was performed with an ABL 510 acid-base analyser requiring 35 mu L of blood and yielding the results within 47 seconds. Results Uns uccessful fetal blood sampling procedures (no result or an unreliable result) occurred significantly more often in the pH subgroup than in t he lactate subgroup (OR 16.1 with 95% CI 5.8-44.7). In the pH subgroup the failure rate was inversely related to the degree of cervical dila tation. Compared with the pH subgroup, the lactate subgroup was charac terised by fewer fetal scalp incisions per blood sampling attempt (med ian 1.0 [interquartile range (IQR) 1-1] vs 2.0 [IQR 1-2]), and signifi cantly less time required for the sampling procedure (median 120 s [IQ R 90-147] vs 230 s [IQR 180-300]). The groups did not differ in mode o f delivery, neonatal outcome and umbilical artery acid-base balance an d lactate levels. Conclusion This trial showed the levels of lactate a nd pH in fetal scalp blood to be comparable in predicting perinatal ou tcome, but the procedure to measuring lactate was more successful than that for pH. Owing to its simplicity of performance, lactate analysis is an attractive alternative for intrapartum fetal monitoring.