Fluid preload in obstetric patients. How to do it?

In has been shown in non-obstetric patients, that a fast acute fluid preload immediately after spinal anesthesia was more effective than a slow preload before regional block to decrease the incidence and severity of arterial hypotension after spinal anesthesia. This study aimed at comparing the incidence of arterial hypotension and vasopressants consumption in parturients submitted to C-section under spinal anesthesia with different fluid preload regimens.

Sixty term pregnant women submitted to C-section under spinal anesthesia. Patients were randomly distributed in three groups receiving acute preload (10 ml kg(-1) lactated Ringer's) as follows: Group 1 (n = 20), before spinal anesthesia through 18G catheter; Group 2 (n = 20), after spinal anesthesia through 18G catheter and Group 3 (n = 20), after spinal anesthesia through 16G catheter with pressurizer. Blood pressure (BP) was monitored at 1-minute intervals until delivery and 0.2 mg bolus metaraminol was administered for any BP decrease from baseline values; 0.4 mg was administered for BP decrease >or= 20%. Control blood pressure was defined as the mean of three successive SBP values obtained before acute preload and spinal block. Variables studied were: preload rate, incidence of maternal arterial hypotension, nausea, vomiting, vasopressants consumption, Apgar scores and umbilical artery pH.

Acute preload was faster in Group 3 as compared to Groups 1 and 2 (201 +/- 61 vs 56 +/- 13 and 59 +/- 21 ml min(-1), p < 0.05). Groups were similar regarding the incidence of arterial hypotension, nausea and vomiting, metaraminol consumption, Apgar scores and umbilical artery pH.

Acute preload before or after spinal anesthesia performance, in a slow or fast rate, does not change vasopressants consumption, the incidence of maternal arterial hypotension, nausea and vomiting, as well as fetal wellbeing.