ALKALINIZATION IMPROVES THE QUALITY OF LIDOCAINE-FENTANYL EPIDURAL-ANESTHESIA FOR CESAREAN-SECTION

This double-blind randomized study of 116 healthy women was undertaken to evaluate whether alkalinization potentiated the analgesic effects of epidural fentanyl-lidocaine for elective Caesarean section. After a test-dose of 3 ml, lidocaine 2% with adrenaline 1:200,000, all patien ts received 100 mug, fentanyl in 5 ml saline and they were then divide d into two groups, to receive incremental doses of 5 ml lidocaine 2% w ith adrenaline 1:200,000 with or without 0.1 mEq . ml-1 sodium bicarbo nate, to obtain anaesthesia to T4. The addition of bicarbonate to lido caine resulted in a mean (SD)pH increase from 6.58 (0.01) to 7.14 (0.0 2) and in a mean PCO2 increase from 3.8 (0.8) to 345.1 (5.9) mmHg. Ons et of sensory analgesia to the S1 segment as well as the interval betw een the block and the delivery of the baby were shorter in the bicarbo nate group (respectively 15.4 (6.9) vs 18.9 (4.8) min and 28.9 (9.5) v ersus 33.9 (11.8) min; P < 0.01 and 0.05). No differences were noted i n the onset to T4 or in the degree of motor block. The percentage of p atients experiencing pain during surgery and requiring intravenous ana lgesics was higher in the group which did not receive bicarbonate (3% vs 16%; P < 0.05). There were no differences in intraoperative materna l side-effects, neonatal outcome or in maternal venous and umbilical v enous and arterial lidocaine concentrations between the groups. The co ncentrations of fentanyl in maternal plasma, umbilical artery, and the umbilical artery to maternal vein ratio were greater in the alkaliniz ed group (P < 0.001). In conclusion, alkalinization improves the quali ty and reliability of epidural anaesthesia provided with fentanyl and lidocaine for Caesarean section in healthy mothers.