Peripartum colloid osmotic pressure changes: effects of controlled fluid management

A prospective, fluid-controlled study of serially measured colloid osmotic pressure changes in the peripartum period was undertaken. Seventeen patients with uncomplicated pregnancies undergoing elective cesarean section at term were administered a predelivery bolus of 15 ml/kg of lactated Ringer's solution prior to operation. Maintenance crystalloid fluids were infused at 125 to 150 ml/hr both intraoperatively and post partum without the addition of blood or other colloid solutions. Serial colloid osmotic pressure measurements were obtained before hydration, after hydration, after delivery, and at 6 and 24 hours post partum. The results demonstrated a 15.9% decline in colloid osmotic pressure immediately following the hydration bolus (20.7 +/- 1.5 to 17.4 +/- 1.8 mm Hg) (p less than 0.01). A further decline in colloid osmotic pressure to 16.6 +/- 1.7 mm Hg occurred after delivery and represented an overall 22% decrease from the baseline value (p less than 0.05). The lowest mean colloid osmotic pressure value occurred at 6 hours post partum (16.1 +/- 1.1 mm Hg). These data support previous observations that colloid osmotic pressure is uniformly lowered in the immediate postpartum period with peak reductions identified at 6 hours following delivery. In addition, intravenous crystalloid administration during the peripartum interval can substantially influence this decline in colloid osmotic pressure. Although no clinical evidence of cardiopulmonary compromise was observed in this set of normal gravid women, these data may be useful in the management of the parturient patient with established risk factors for pulmonary edema where alterations in the pulmonary capillary wedge pressure-colloid osmotic pressure gradient have been shown to correlate with the development of this complication.