Effect of Propfol Versus Sevoflurane on Auditory and Cognitive Function: A Compartive Study

Perioperative hearing loss is a rarely reported phenomenon. However, it occurs more frequently than most anaesthesiologists suspect. Perioperative hearing impairment is often subclinical and may go unnoticed unless audiometry is performed.

It can be conductive or sensorineural, unilateral or bilateral, and transient or permanent. Hearing loss has been reported following virtually every type of anaesthetic technique.

The hearing mechanism may be less susceptible to acoustic trauma during general anaaesthesia. But other mechanisms are capable of causing both conductive and sensorineural hearing losses (SNHL) in the perioperative period. The aetiologies include mechanical, traumatic, noise-induced, changes in cerebrospinal fluid (CSF) pressure, embolism, pharmacologic, and other miscellaneous causes.

Stress may influence central vestibular function in health and disease either directly through the actions of glucocorticoids (cortisol and corticosterone) on ion channels and neurotransmission in the brain, or indirectly through the effects of stress-related neuroactive substances (e.g., histamine, neurosteroids) on these structures.

The auditory brainstem response (ABR) provides a good estimate of the shape of the behavioral audiogram [and is thus an extremely useful tool for studying hearing sensitivity as well as the functionality of the auditory system.

An awareness of the potential for and the causes of hearing loss during anesthesia may permit the anesthesiologist to prevent or minimize the risk of significant hearing deficit. The suggestion that this risk be discussed in the preoperative period with patients who are at high risk for perioperative hearing loss may be good medical-legal advice. Better understanding of the incidence, causes, and prognoses for perioperative hearing loss is essential for the anesthesiologist.

Much Concern has been raised about the effects of anaesthetic drugs on cognition. Postoperative cognitive dysfunction may manifest as impairment in attention, memory, language or executive functions following surgery, and can persist for weeks, months, or more with varying severity. Such post-operative cognitive dysfunction can be quite mild and only diagnosed through psychometric assessment using specific neuropsychological tests.

AIM OF THE STUDY The aim of this work is to study the possible deleterious effect of propfol versus sevoflurane on auditory and cognitive function.