Effect of Increase in pH of Local Anaesthetics on Quality of Epidural Anesthesia

Background: The most persistent criticisms for epidural analgesia for surgery are the latency of onset and marginal intensity of sensory and motor block, so clinical trials were carried out to find out a method to decrease the latency of onset of epidural block. The present study was carried out to determine the effect of increasing pH of 2% lignocaine hydrochloride with adrenaline (1:200000) and 0.5% bupivacaine hydrochloride by addition of sodium bicarbonate administered for epidural anesthesia in inguinal herniorrhaphy. Methods: Eighty male patients aged 18–60 years physical status American Society of Anesthesiology I and II posted for inguinal herniorrhaphy, were enrolled in this study. After placing epidural catheter in epidural space at L3–L4, test dose of 2% lignocaine with adrenaline 3ml was given. After making patient supine, epidural dose is given with local anesthetic according to the group. Group I ‑ 15 ml of 2% lignocaine hydrochloride with adrenaline (1:200000) +0.5 ml normal saline (pH 3.58), Group II ‑ 15 ml of 2% lignocaine hydrochloride with adrenaline (1:200000) +0.5 ml of 7.5% (w/v) sodium bicarbonate (pH 6.78), Group III ‑ 15 ml of 0.5% bupivacaine hydrochloride (pH 5.5) and Group IV ‑ 15 ml of 0.5% bupivacaine hydrochloride + 0.1 ml of 7.5% (w/v) sodium bicarbonate (pH 7.5). In Groups II and IV, pH of solution was increased by addition of sodium bicarbonate. All patients were monitored for the onset of sensory and motor block, intensity of sensory and motor block, highest level of analgesia, duration of sensory and motor blockade, and effects on cardiovascular and respiratory parameters. Results: Onset of sensory and motor block was significantly faster in study Groups (II and IV) as compared to control Groups (I and III). Intensity of block even duration of block was significantly better in pH adjusted group. Conclusion: Increase in pH of local anesthetic solutions used in epidural blockade improves the quality of epidural block.