Hearing Loss after Spinal Anaesthesia: A Too Little Appreciated Complication?

Introduction: Spinal anaesthesia is one of the most frequently used regional anaesthesia techniques in surgical interventions, but unfortunately it may be associated with some degree of auditory dysfunction, notably low-frequency hearing loss. Several authors have investigated this phenomenon using pure tone audiometry for audiologic assessment, but only very few studies have been devoted as yet to the role of otoacoustic emissions in evaluation of hearing loss after spinal anaesthesia. Aims of the study: The present study was designed to: 1-Evaluate the incidence and magnitude of auditory dysfunction associated with spinal anaesthesia. 2-investigate the sensitivity of transient evoked otoacoustic emissions (TEOAEs) to the changes in auditory function as-sociated with spinal anaesthesia, and. 3-Determine the possible causes of the expected auditory dys-function associated with spinal anaesthesia. Material and Methods: Fifteen males, ASA physical sta-tus I or II patients, in the age between 20-40 years, who were scheduled for surgical repair of varicocoele under spinal anaes-thesia were enrolled into this study. All patients were subjected to otoscopy, tympanometry, pure tone audiometry and TEO-AEs. Measurements were taken twice on the day of surgery: Preoperatively, prior to administration of spinal anaesthesia and postoperatively, in the recovery room. Statistical analysis: Statistical analysis included the arithmetic mean, standard deviation (SD), standard error and hypothesis Student’s “t” test, and Pearson’s correlation tests. The level of statistical significance was determined by a probability value of p 0.05. Results: Five patients were excluded from the study. In the remaining ten patients (20 ears), a bilateral, highly-significant reduction in TEOAEs response was recorded at all frequencies, but with the greatest reductions occurring at 2000 and 3000Hz. No correlation could be found between TEOAEs amplitude and the haemodynamic changes associated with subarachnoid block. Pure tone audiometry (PTA) showed a highly-significant (p 0.001) increase in hearing threshold by more than 5 dB at the low frequencies (125, 250, 500 and 1000 Hz). At the higher frequencies (2000, 4000 and 8000 Hz), the hearing threshold increased by 1 dB only, but only the increase recorded at 2000 and 4000 Hz was statistically significant (p 0.05). Conclusion: Transient hearing loss after spinal anaesthesia may occur more often than it is generally assumed and the symptoms might not be recognized. Audiometry may be a more sensitive indication of cerebrospinal fluid leak than postspinal headache. OAEs can be used as an effective and objective way of evaluating the hearing loss in this particular group of patients. Future recommendations: The use of smallgauge (≤26- gauge) spinal needles of the splitting type, together with proper volume replacement, is strongly advised to minimize any possible auditory dysfunction occurring after subarachnoid block. For medicolegal reasons, all patients should be informed about any possible transient hearing loss that could be associated with spinal anaesthesia.