Onset Time of Spinal Anaesthesia in Pregnant Females in Knee-Chest Position: A Randomized Controlled Study

To assess the efficacy of knee-chest position in shortening the time of spinal induction in pregnant women undergoing elective cesarean section. We also assessed for any untoward adverse events that might limit their usefulness in real-life clinical scenarios.

Prospective, randomized controlled study was done in maternity operating room of tertiary care institution in 45 ASA II pregnant women undergoing elective cesarean section under spinal anaesthesia. Patients were randomly assigned to groups S (supine) and K (kneechest position). After performing subarachnoid block (9 mg of 0.5% hyperbaric bupivacaine and 25 µg fentanyl) in the sitting position, women in group K were maintained in the knee-chest position for 60 seconds. Time to attain block height of T6 and maximum sensory blockade, intraoperative hemodynamics, Bromage score, intraoperative fluid, vasopressor requirement, and respiratory parameters were recorded. The newborn was evaluated using Apgar scores at 1 and 5 minutes.

Data of 45 patients were analyzed. Time to attain T6 block height (group K=2.1 ± 0.65 minutes, 95% CI: 1.83-2.39; group S=6.4 ± 0.77 minutes, 95% CI: 6.10-6.78) and time to achieve maximum sensory block height were significantly lower in group K (group K=3.2 ± 1.35 minutes, 95% CI: 2.61-3.78; group S=6.6 ± 0.89 min, CI: 6.19-6.98). The degree of motor block was higher in group K than that of group S at 2 minutes (P=.0002), 4 minutes (P < .0001), and 6 minutes (P < .0001), with no difference at 8 minutes. No statistically significant difference was observed in fluids and vasopressors requirement intraoperatively.

This study provides evidence that the onset of adequate surgical anaesthesia for the cesarean section can be hastened by placing the patient in the knee-chest position for a minute after performing the subarachnoid block in the sitting position.