A study of low-dose S-ketamine infusion as "preventive" pain treatment for cesarean section with spinal anesthesia: benefits and side effects
Minerva Anestesiologica, 06/26/2012

Suppa E et al. – Preventive administration of S–Ketamine via 12–hour infusion was safe and may have anti–hyperalgesic action after cesarean section.

• Women undergoing elective repeat cesarean section with subarachnoid anesthesia (0.5% hyperbaric bupivacaine 8–10 mg and sufentanil 5µg) were enrolled in a double–blind, randomized study.
• Patients in the S–Ketamine group (N=28) received i.v. midazolam 0.02mg/kg and S–Ketamine 0.5mg/kg i.m. bolus 10minutes after birth followed by a 2µg/kg/min i.v. continuous infusion for 12h.
• 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).

• S–Ketamine reduced morphine consumption at 4–8, 8–12, and 12–24hours 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.