An up-down determination of the required seated duration after intrathecal injection of bupivacaine and fentanyl for the prevention of hypotension during Cesarean delivery

A prolonged seated time after intrathecal injection of hyperbaric bupivacaine and morphine is related to the incidence of hypotension during Cesarean delivery, but results in a high incidence of pain during peritoneal closure. We conducted this study to determine the effect of the addition of intrathecal fentanyl on the relationship between seated time and hypotension and intraoperative analgesia requirements. Women undergoing Cesarean delivery were randomized to receive an intrathecal injection of either 11.25 or 15 mg of hyperbaric bupivacaine with morphine 150 µg and fentanyl 15 µg using a combined spinal-epidural technique. The seated duration following intrathecal injection was assigned using up-down methodology. If the preceding patient was hypo- or normotensive, the next patient sat for 15 sec more or less, respectively. A systolic blood pressure < 80% of the preoperative value was defined as hypotension; a standardized anesthetic was administered, and the presence of pain during the procedure was recorded. Isotonic regression of pooled adjacent violators was used to determine the time at which 50% of each group would avoid hypotension (i.e., the median effective seated time). There were 15 patients in each group. The median seated time was 129 sec (95% confidence interval [CI], 116 to 150) for the 11.25-mg group and 459 sec (95% CI, 444 to 471) for the 15-mg group. Only one (3%) of the 30 patients in the study had pain on peritoneal closure, and this was successfully treated with intravenous fentanyl. We have determined the seated time required following intrathecal injection of hyperbaric bupivacaine, morphine, and fentanyl to prevent hypotension in 50% of patients undergoing Cesarean delivery. www.clinicaltrials.gov , NCT01896960. Registered 2 July 2013.