A study of low-dose S-ketamine infusion as "preventive" pain treatment for cesarean section with spinal anesthesia: benefits and side effects.

BACKGROUND: Attenuation of central sensitization with NMDA-active drugs such as S-Ketamine may play a role in postoperative analgesia and prevention of neuropathic pain. However, during cesarean section with neuraxial block, S-Ketamine might have adverse effects on the interaction between mothers and infants, including breastfeeding. METHODS: Women undergoing elective repeat cesarean section with subarachnoid anesthesia (0.5% hyperbaric bupivacaine 8-10 mg and sufentanil 5 µg) were enrolled in a double-blind, randomized study. Patients in the S-Ketamine group (N.=28) received i.v. midazolam 0.02 mg/kg and S-Ketamine 0.5 mg/kg i.m. bolus 10 minutes after birth followed by a 2 µg/kg/min i.v. continuous infusion for 12 h. The control group (N.=28) received placebo. Paracetamol and patient controlled analgesia with intravenous morphine were given postoperatively. Von Frey filaments were used to assess pain threshold on the inner forearm and T10-T11 dermatomes (supposed hyperalgesic area). RESULTS: S-Ketamine reduced morphine consumption at 4-8, 8-12, and 12-24 hours after surgery (total 31%), even after its effect has ceased, suggesting an anti-hyperalgesic action. Mild side effects were observed in the S-Ketamine group one hour after delivery. All side effects were rated as light and there were no serious adverse events. Pain threshold was not significantly different between groups. S-Ketamine patients showed a trend towards reduced pain sensitivity at the T10 dermatome, which is involved by surgical damage. After three years, patients reported no differences in residual pain, dysesthetic symptoms, or duration of breast-feeding. CONCLUSION: Preventive administration of S-Ketamine via 12-hour infusion was safe and may have anti-hyperalgesic action after cesarean section.

Remifentanil for cesarean section under general anesthesia: effects on maternal stress hormone secretion and neonatal well-being: a randomized trial.

BACKGROUND: Remifentanil may attenuate maternal hemodynamic response during cesarean section under general anesthesia, but could cause transient but significant neonatal depression. We investigated the effect of low-dose remifentanil on maternal neuroendocrine response and fetal wellbeing. METHODS: Forty-two ASA I-II parturients undergoing cesarean section at term under general anesthesia were randomized to receive either fentanyl after delivery (n=21, group C) or remifentanil bolus 0.5 microg/kg before induction followed by a continuous infusion at 0.15 microg x kg(-1)min(-1) until peritoneal incision, then restarted after delivery (n=21, group R). Maternal heart rate and blood pressure, and epinephrine, norepinephrine, adrenocorticotropic hormone (ACTH), and growth hormone levels were measured at baseline, uterine incision, and the end of surgery. Remifentanil was measured in maternal and umbilical arterial and venous blood. One- and 5-minute Apgar scores and umbilical arterial and venous pH were recorded. RESULTS: ACTH was significantly higher in group C at uterine incision (P<0.01). No significant differences were observed in hemodynamics, catecholamines or growth hormone. Apgar scores at 1 (P<0.05) and 5 min (P<0.01) were significantly higher in group C. Mean umbilical pH values were within normal range but significantly higher in group C. Three neonates in group R required intubation but recovered at 5 min without naloxone. Mean+/-SD maternal remifentanil concentration was 1.67+/-1.04 ng/mL. CONCLUSIONS: Remifentanil administration before peritoneal incision partially reduced the hormonal stress response. Maternal benefits must be weighed against transitory but significant neonatal respiratory depression. Neonatal resuscitation facilities are mandatory when remifentanil is used.