Postoperative delirium and cognitive decline are recognized as one of the most frequent surgical complications in older patients. The aging brain is more sensitive to develop delirium when exposed to anesthetic agents. Therefore, it is necessary to study the effect of anesthesia on the incidence of delirium and cognitive decline in elderly patients.

A randomized comparative trial was conducted among 100 obese patients to investigate the incidence of delirium and cognitive decline, wake-up times and its regulation using different anesthesia. The patients underwent total knee replacement under general anesthesia (Propofol or Desflurane) with a femoral nerve block catheter. Patients were divided into two groups, one received Propofol, and other received Desflurane.

The results were evaluated at two endpoints, primary and secondary. The primary endpoint was delirium which was measured by the Confusion Assessment Method (CAM). The secondary endpoint was a battery of six different tests of cognitive function and wake-up times.

Out of 100 patients, 4 patients that provided informed consent were withdrawn from the study. Now of the remaining 96 patients, 6 did not complete the full CAM test. Further, Propofol group was known to have one patient with delirium compared to zero in Desflurane group. One of the patients in desflurane group also developed a confused state, but not characterized as delirium. The duration of surgery and anesthesia, amount of intraoperative fentanyl and preoperative pain scores were same in both the groups. Same as these, there was no difference in the incidence of postoperative nausea, vomiting and length of post-anesthesia care unit (PACU) between the groups. Additionally, 50% of the patients showed a 20% decrease in results of at least one cognitive test on the first two days after the surgery, and there was no any difference among the groups.

This study demonstrated a low prevalence of delirium, but the significant cognitive decline was noted in the first 48 h after surgery. The study had a small sample size, and there was no difference in the occurrence of postoperative delirium, early cognitive outcomes, or wake up times between the Desflurane or Propofol group. Further studies with big sample size are desired to guide clinical practice in choosing suitable anesthesia for elderly patients undergoing surgery.