Plasma arginine vasopressin response to water load during labor

ABSTRACT

To find out whether plasma vasopressin (PAVP) response to a water load during pregnancy is inappropriately high, as had been speculated, we measured PAVP by radio-immunoassay in 30 women at the time of delivery. Ten women had received infusion of aqueous glucose solution during labor for hydration (GW group); another ten received infusion of glucose solution as a vehicle for oxytocin (OT group), and ten women did not receive any intrapartum intravenous fluid therapy (controls). Serum sodium and osmolality were also determined in all the subjects. PAVP levels were significanty lower in GW (0.70) ñ 0.4 pg/ml)and OT groups (0.7 ñ 0.6 pg/ml) (P< 0.05). Significant negative correlation was seen between the amount of glucose solution infused and levels of PAVP (r = 0.61; P< 0.01). These findings suggest that during labor, the physiological relationship between serum osmolality and PAVP is intact, and that infusion of a water load in the form of aqueous glucose solution is attended by an expected lowering of PAVP. We infer that inappropriate ADH response is not the cause of water retention and hyponatremia often seen in women receiving aqueous glucose solution during labor.(AU)