Review question

We wanted to discover whether using brain electrical activity monitoring to guide doses of anaesthetics can reduce the risk of postoperative delirium (POD) and cognitive dysfunction (POCD) in adults undergoing general anaesthesia for non-cardiac and non-neurological surgical procedures.

Background

Postoperative delirium (POD) is a disturbed state of mind which occurs a few days after surgery. POD involves a fluctuating course of confusion and disorganized behaviour. Postoperative cognitive dysfunction (POCD) is a decline in the ability of a person to think clearly after an operation. This may persist for weeks or months. POCD can affect a person’s concentration, attention, memory, learning, and the speed of their movement and mental responses. POD and POCD can complicate the quality of a person’s recovery from anaesthesia, as well as the quality of their life after surgery.

Processed electroencephalogram (EEG) monitors generate numerical values of brain electrical activity. The number provides information about the depth of anaesthesia during surgery, and is used to guide the dose of anaesthetic given. This is to prevent someone receiving either too small or too large a dose of anaesthetics.

Search date

The evidence is current to March 2017. We found six completed studies, five ongoing studies, and one awaiting classification.

Study characteristics

All six completed studies were randomized controlled trials (RCT) conducted in 2929 male or female participants undergoing a surgical procedure and aged 60 years or over. An RCT is a study (or trial) which aims to reduce bias when testing a new treatment. The people taking part in the trial are randomly allocated to either the group receiving the treatment under investigation, or to a group receiving standard treatment (or placebo treatment) as the control. RCTs provide the most reliable evidence.

Key results

Results from three studies (2529 participants) indicate that using the processed EEG to help deliver the optimal depth of anaesthesia could reduce the incidence of POD from 21.3% to 15.2%. Results from three studies (2051 participants) indicate that this could also reduce the incidence of POCD at three months from 9.1% to 6.4%.

Quality of the evidence

Our review provides moderate-quality evidence that anaesthesia guided by processed EEG indices could reduce the risk of postoperative delirium in patients aged 60 years or over undergoing non-cardiac and non-neurological surgical procedures. We found some moderate-quality evidence that postoperative cognitive dysfunction at three months could be reduced in these participants. There is insufficient evidence supporting the effect on POCD at one week and over one year after surgery or in younger patients.