Comparative Evaluation of Postoperative Cognitive Dysfunction following General Anaesthesia with Propofol and Isoflurane in Elderly Patients

Postoperative Cognitive Dysfunction is a well-recognized clinical phenomenon and the incidence is much higher in elderly patients. There are conflicting reports on the incidence of postoperative cognitive dysfunction following the use of inhalational and intravenous anaesthetic agents. We will be doing a comparative evaluation of the incidence of Postoperative cognitive dysfunction following general anaesthesia with propofol and isoflurane in elderly patients. 

Patients aged 60-80 years requiring general anaesthesia would be evaluated. Those fulfilling inclusion/exclusion criteria will be recruited. Baseline evaluation using Hindi Mental State Examination, Digit Span test and Digit symbol substitution test will be done. Following which the enrolled patients will be randomized into the two intervention arms. The subjects of both groups will be taken into the operation theatre, standard monitors, including bispectral index(BIS) attached, Inj Fentanyl 2mcg/kg will be administered and baseline vitals will be recorded. Induction will be done with Inj Propofol 1.5-2mg/kg in titrated doses till loss of verbal response. Inj Vecuronium 0.1mg/kg will be used to achieve neuromuscular  blockade and airway will be secured with an appropriate sized endotracheal tube when BIS decreases to 40-60. In patients of group P, anaesthesia will be maintained with IV infusion of propofol at the rate of 50-150mcg/kg/min and controlled ventilation provided using 50% oxygen in nitrous oxide. In patients of group I anaesthesia will be maintained with 50% oxygen in nitrous oxide and isoflurane at MAC 1.0-1.5. Muscle relaxation will be maintained with Inj Vecuronium top up of 0.02mg/kg. Depth of anaesthesia will be monitored by BIS and propofol and isoflurane concentrations will be titrated to maintain BIS in the range of 40-60. After ensuring isovolumia, if there is an increase in heart rate and systolic blood pressure of >20% from baseline, Inj Fentanyl 0.25mcg/kg IV top-up will be administered. Local anaesthetic infiltration at the surgical incision site will be given at the end of the surgery. Anaesthetics will be stopped at the end of the surgery and neuromuscular blockade will be antagonized with neostigmine 0.05mg/kg and glycopyrrolate 0.01mg/kg. Patients will be extubated after they recover spontaneous breathing and BIS increases to >80. Postoperative cognitive dysfunction will be assessed 24 hours postoperatively by means of the above mentioned tests. Statistical analysis will be done using Mann Whitney-U test for quantitative data and Chi-square test or Fisher’s exact test to find association between these 2 groups.