Zhiyi Zuo

Research Committee Chair, Department of Anesthesiology  M.D., Ph.D

Postoperative cognitive dysfunction (POCD) is now a well-known clinical entity. Old age is a significant risk factor for it. About 40% or 10% patients who are older than 60 years are affected by POCD at hospital discharge or 3 months after non-cardiac surgery. POCD not only affects the daily living but also carries poorer long-term outcome, such as increased mortality. Thus, it is extremely important to develop interventions to reduce POCD. Identifying modifiable risk factors for POCD should help reduce the occurrence of this complication after surgery.

Since the majority of surgeries are performed under general anesthesia in the developed countries, general anesthesia/anesthetics have been suspected to contribute to POCD development. There are two types of genera anesthetics: intravenous anesthetics, such as propofol, and volatile anesthetics, such as isoflurane, sevoflurane and desflurane.

Many studies have shown that volatile anesthetics, such as isoflurane and sevoflurane, can affect cognitive functions of animals, although no effects have also been reported. Our recent studies showed that isoflurane induced cognitive impairment and mild neuroinflammation in rats. Neuroinflammation is a possible pathophysiological process for POCD. Propofol-based general anesthesia neither affected the cognition nor induced neuroinflammation in rats. However, the degree of cognitive impairment and neuroinflammation is similar in elderly rats after common carotid artery exposure under isoflurane-based or propofol-based general anesthesia.

These results suggest that anesthetic choice may not affect the development of POCD. Consistent with this observation, clinical studies have not identified anesthetic choice or volatile anesthetic use is a risk factor for POCD. Three clinical studies have compared POCD occurrence after volatile anesthetics-based or propofol based general anesthesia. Two studies showed that patients with volatile anesthetics-based general anesthesia had reduced POCD rate at the hospital discharge after cardiac surgery. The third study showed that propofol-based general anesthesia reduced POCD occurrence at hospital discharge after carotid endarterectomy. Thus, there is no evidence yet to suggest that anesthetic choice is a modifiable factor for POCD.