The effect of combined spinal-epidural (CSE) anaesthesia and size of spinal needle on postoperative hearing loss after elective caesarean section

The exact aetiology of vestibulocochlear dysfunction after spinal anaesthesia is unknown. Low-frequency hearing loss occurs after spinal anaesthesia. The aim of this study was to investigate the effects of combined spinal-epidural (CSE) anaesthesia and size of spinal needle on vestibulocochlear dysfunction, using pure tone audiometry performed pre- and on the first and the second day postoperatively. Forty-five patients who were to undergo elective caesarean section were evaluated. In group I, CSE anaesthesia (18 G Tuohy, 25 G Whitacre pencil-point-design spinal needles) was performed in 15 patients. In group II, spinal anaesthesia was performed in 15 patients with 25 G Whitacre pencil-point-design spinal needles and, in group III, spinal anaesthesia was performed in 15 patients with 22 G Whitacre pencil-point-design spinal needles. In the pre- and on the first and the second day postoperatively, the pure tone audiogram was performed in the audiology laboratory of our hospital, using a calibrated Kamplex Diagnostic Audiometer AC 40 in a noise-free room. When the CSE anaesthesia group and 22 G spinal group were compared for change in hearing between the pre- and postoperative periods, a statistically significant difference was observed at R-right ear 125 Hz (P < 0.025) and at L-left ear 125 Hz (P < 0.023), and at L-left ear 1000 Hz (P < 0.036) and at R-right ear 1500 Hz (P < 0.006), and at L-left ear 1500 Hz (P < 0.022). At other frequencies, the difference was insignificant. When the CSE anaesthesia group and 25 G spinal group were compared for change in hearing between the pre- and postoperative periods, no statistically significant difference was detected at any frequency tested. When 22 G spinal group and 25 G spinal group were compared for change in hearing between the pre- and postoperative periods, there was some hearing loss at low frequency, although this difference did not reach statistical significance. The positive correlation of low-frequency hearing loss and increased pressure in the epidural space (which decrease the risk of cerebrospinal fluid leakage through the dura) suggests that cerebrospinal fluid leakage via the spinal puncture hole is not the only factor involved. Perioperative fluid replacement alone may not prevent hearing loss but CSF loss through the dural puncture site should also be prevented.