Washington—Although sevoflurane anesthesia can cause declines in short-term cognitive function after surgery in elderly patients, preoperative infusion of dexmedetomidine can mitigate these effects, a new study suggests.

Lead investigator Hui Xu, MD, a consultant anesthesiologist at the University of Science and Technology, in Wuhan, China, and her colleagues enrolled 60 patients (aged 65-75 years) into the randomized, double-blind trial. Before undergoing anesthesia with sevoflurane, half the patients received an infusion of 1 mcg/kg dexmedetomidine (Precedex, Hospira) over 15 minutes, the other half received saline. Both groups underwent an otherwise identical standardized anesthetic regimen. As part of that regimen, 0.6 mg/kg of rocuronium was used to facilitate tracheal intubation. Anesthesia was induced with sevoflurane and a single IV injection of 5 mcg/kg of fentanyl. Rocuronium was titrated throughout the procedure as needed.

The researchers evaluated cognitive function using the Mini-Mental State Examination (MMSE), assessing patients preoperatively and one, three, six, 24 and 72 hours postoperatively. A postoperative decline of at least 2 points in at least two of the tested domains was defined as cognitive function decline.

As Dr. Xu reported at the American Society of Anesthesiologists’ 2012 annual meeting (abstract 149), the time to eye opening and extubation were comparable between groups. However, the time to react on command occurred sooner in patients given dexmedetomidine-sevoflurane than in those receiving only sevoflurane (P<0.05).

MMSE scores showed no statistically significant differences between groups before surgery. Although these scores decreased significantly in both groups at one and three hours postoperatively (P<0.05), they were significantly lower in the sevoflurane-only group (P<0.05). MMSE scores took six hours to recover to preoperative levels in the dexmedetomidine-sevoflurane group compared with 24 hours in the sevoflurane-only group.

Two markers of brain injury, serum 100B and C-reactive protein (CRP), also appeared to be elevated in patients who received sevoflurane alone (P<0.05).

“These results show that although sevoflurane anesthesia can cause short-term postoperative cognitive dysfunction, dexmedetomidine is effective at improving cognitive function associated particularly with respect to return to preoperative levels,” Dr. Xu said.

Critical Care Pharmacist’s View

John W. Devlin, PharmD, an associate professor of pharmacy practice at Northeastern University, in Boston, noted that mounting evidence suggests that inhalational anesthetics may be neurotoxic to the aging brain, leading to postoperative cognitive dysfunction that can persist long after surgery.

“In their rigorous, double-blind study, Dr. Xu and colleagues report that a high dose of dexmedetomidine administered prophylactically over a short period before sevoflurane anesthesia leads to faster postsurgical cognitive recovery,” Dr. Devlin said. “The fact that postoperative serum CRP and serum 100B concentrations were lower in the dexmedetomidine-treated patients suggests that the drug may exert a protective effect against the effects of inhalational anesthetics in the brain through both anti-inflammatory and decreased blood–brain permeability mechanisms.

“While additional, larger studies are needed to evaluate the safety of dexmedetomidine in this setting and the benefits of its administration on longer-term cognitive and clinical outcomes,” Dr. Devlin added, “this important study suggests that the prophylactic use of dexmedetomidine may play an important role in improving short-term outcome in elderly patients who require surgery with an inhalational anesthetic.”