RESUMO
PURPOSE: Oxytocin infusions for uterine tone maintenance are recommended following initial low oxytocin doses during cesarean section. Very limited literature is available on the optimal infusion rates in laboring patients who have been earlier exposed to oxytocin. METHODS: 105 patients, having received oxytocin for induction/augmentation of labor, received oxytocin infusions at rates of 2.5 IU/h (Group 2.5), 5 IU/h (Group 5) or 10 IU/h (Group 10) following 3 IU slow bolus. The primary outcome measure was estimated intraoperative blood loss; secondary outcome measures included uterine tone adequacy, requirements for additional uterotonics, and any side effects. Minor postpartum hemorrhage (PPH) was defined as blood loss > 500 ml and major/severe hemorrhage as blood loss > 1000 ml. RESULTS: Group 10 had minimum blood loss (311.1 ± 44.9 ml) and uterotonic requirements compared to other groups (p < 0.001). Group 2.5 had maximum blood loss (549.4 ± 74.3 ml) and uterotonic requirements; Group 5 had intermediate values (402.0 ± 49.5 ml). Twenty-six patients in group 2.5 had minor PPH against only one in group 5 and none in group 10 (p < 0.001). No patient in either group had major PPH. The incidence of hypotension was higher in group 10 than in group 2.5 (p = 0.004). Nausea and vomiting were also more frequent in group 10 than in the other two groups. CONCLUSION: Oxytocin infusions at 5 IU/h and 10 IU/h are more effective in reducing blood loss and preventing PPH than 2.5 IU/h. The dose of 10 IU/h, although the most efficacious, is associated with a high incidence of side effects. Hence, further studies are needed to find out the optimal maintenance infusion rate of oxytocin during cesarean section in laboring patients who have received oxytocin earlier.