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

PURPOSE: 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. METHODS: 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). RESULTS: 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. CONCLUSION: 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. TRIAL REGISTRATION: www.clinicaltrials.gov , NCT01896960. Registered 2 July 2013.

The Labor Analgesia Requirements in Nulliparous Women Randomized to Epidural Catheter Placement in a High or Low Intervertebral Space.

BACKGROUND: We hypothesized that an epidural catheter placed in a lower vertebral interspace will require less medication for labor analgesia. METHODS: Nulliparous women requesting neuraxial labor analgesia were randomized to epidural catheter placement at the ultrasound-confirmed L1-2 or L4-5 interspace. Patient-controlled epidural analgesia and breakthrough manual epidural boluses of 10 mL of 0.125% bupivacaine with 50 µg of fentanyl or 8 mL of 2% lidocaine were utilized. Abdominal and perineal pain scores were assessed at 30 and 60 minutes after standardized initiation of epidural analgesia. Pain scores during pushing were assessed after delivery. The primary outcome was the proportion of patients requiring manual boluses and was compared using a χ test. Secondarily, we analyzed the number of boluses given in early (up to 4 hours before delivery) versus late labor using χ tests and the pain scores using Mann-Whitney U tests, with adjustment of P values for multiple testing. RESULTS: We analyzed 148 patients. Overall, the percentage of patients in the low versus high groups who required manual boluses was 46% vs 51% (P = 1.0). For the 56 patients in each group who delivered vaginally, 22 (52%) vs 20 (48%) manual boluses were given to the low epidural group in early versus late labor, compared to 9 (20%) vs 36 (80%) in the high epidural group (P = .014). There was no statistical difference in patient-controlled epidural analgesia requirements or patient satisfaction. Comparing the low versus high groups, the median (interquartile range) pain scores were: 3 (1, 6) vs 0 (0, 2) (P = .013) at 30 minutes and 1 (1, 3) vs 0 (0, 1) (P = .013) at 60 minutes for abdominal pain; 0 (0, 2) vs 1 (1, 3) (P = .36) and 0 (0, 1) vs 1 (1, 3) (P = .014) at these same time points for perineal pain; and 1 (0, 5) vs 0 (0, 3) (P = .9) for abdominal and 2 (0, 5) vs 4 (1, 8) (P = .025) for perineal pain during pushing. The percentage of patients who underwent instrumental delivery was 15% vs 5% (P = .06) for the low versus high group. CONCLUSIONS: An L4-5 epidural catheter initially provides less relief of abdominal pain but more relief of perineal labor pain. Patients with an L4-5 catheter require more manual boluses during early labor but less during late labor. The possible association of low epidural catheters with instrumental delivery merits further investigation.

The median effective seated time for hypotension induced by spinal anesthesia at Cesarean delivery with two doses of hyperbaric bupivacaine: a randomized up-down sequential allocation study.

BACKGROUND: Extending the time a parturient is left sitting after induction of spinal anesthesia (i.e., the seated time) has had varying success in decreasing hypotension at Cesarean delivery. This may be due to the current lack of information concerning the dose-response relationship of seated time and rates of hypotension. METHODS: Term parturients scheduled for Cesarean delivery were randomized to receive 11.25 or 15.0 mg of 0.75% intrathecal hyperbaric bupivacaine, and they remained seated after injection for a length of time determined by an up-down sequential method. They were then placed in a wedged position and their blood pressure was measured every minute. Pre-delivery hypotension was considered present if there was a > 20% from baseline drop in systolic blood pressure. The seated time at which 50% of parturients avoided pre-delivery hypotension (median effective seated time) was determined with isotonic regression. RESULTS: Fifty patients were studied. For the 11.25-mg and 15.0-mg groups, the median effective seated time (95% confidence interval [CI]) was 130 sec (95% CI 117 to 150) and 385 sec (95% CI 381 to 396), respectively. CONCLUSIONS: There exists a seated time after intrathecal injection of hyperbaric bupivacaine where 50% of parturients do not experience hypotension. This seated time increases with an increased dose of bupivacaine. Further work is required to determine the full relationship between seated time and hypotension for other doses of anesthetic and to investigate the clinical utility of this technique for prevention of hypotension. This trial was registered at www.clinicaltrials.gov (NCT01561274).