Effect of fluid preload on maternal haemodynamics for low-dose epidural analgesia in labour

We prospectively studied 30 women in labour who requested epidural analgesia. They were randomly allocated into two groups; one received a preload of 7 mL/kg normal saline and the other no preload. All patients had a standard epidural solution consisting of 0.1% bupivacaine 20 mL containing fentanyl 2 microg/mL. Mean arterial blood pressure and cardiac index were measured serially for 20 min after epidural drug administration. Cardiac index was measured using transthoracic electrical bioimpedance (BOMED). Power calculation showed that a sample size of 30 had 80% power to detect a difference of more than 20% in cardiac index using a two-sided test at a significance level of <0.05. No significant changes in cardiac index or mean arterial pressure occurred at any time in either group. These results suggest that routine fluid preloading is not necessary for 0.1% bupivacaine 20 mL with fentanyl 2 microg/mL as epidural bolus in labour.