From the Guidelines
Bispectral Index (BIS) monitoring is recommended during general anesthesia for high-risk patients, such as the elderly, those with significant cardiovascular disease, and patients receiving total intravenous anesthesia (TIVA) with neuromuscular blocking agents. The use of BIS monitoring can help reduce the risk of awareness during anesthesia and postoperative delirium by maintaining an appropriate anesthetic depth, typically targeting values between 40-60 for surgical anesthesia 1. This is particularly important in patients where traditional clinical signs of anesthetic depth may be masked, such as those receiving TIVA with propofol and remifentanil. Key patient populations who may benefit from BIS monitoring include:
- Elderly patients
- Patients with significant cardiovascular disease
- Patients with previous awareness during anesthesia
- Patients receiving TIVA with neuromuscular blocking agents BIS monitoring works by processing EEG signals to generate a dimensionless number between 0-100, where lower numbers indicate deeper anesthesia. While BIS monitoring can help guide anesthetic management, it should complement rather than replace clinical judgment, as factors like certain medications, hypothermia, and neurological disorders can affect BIS readings independently of anesthetic depth 1. Recent guidelines recommend the use of processed electroencephalogram (pEEG) monitoring, such as BIS, when TIVA is administered together with a neuromuscular blocking (NMB) drug, and consider its use during other anaesthetic techniques, including inhalational anaesthesia, and for high-risk patients 1. Overall, the use of BIS monitoring can help improve patient outcomes by reducing the risk of awareness and postoperative delirium, and should be considered in high-risk patients undergoing general anesthesia.
From the Research
Utility of BIS Monitor
The Bispectral Index (BIS) monitor is a device used to measure the depth of anesthesia by analyzing the electrical activity in the brain. The following points highlight the utility of BIS monitoring during general anesthesia:
- Reduction in postoperative cognitive dysfunction risk: BIS monitoring has been shown to reduce the risk of postoperative cognitive dysfunction [ 2 ].
- Shortened recovery times: The use of BIS monitoring has been associated with shorter eye-opening times, orientation recovery times, extubation times, and postanesthesia care unit stay times [ 2 ].
- Lowered anesthesia drug dosage: BIS monitoring can help guide the dose of anesthesia, leading to lower drug dosages and potentially reducing the risk of adverse effects [ 2 ].
- Comparison with other monitoring methods: Studies have compared BIS monitoring with other methods, such as phase lag entropy (PLE) and clinical signs, and found that BIS can be an effective tool for monitoring the depth of anesthesia [ 3, 4, 5 ].
- Technical ease and effectiveness: BIS monitoring has been shown to be technically easy and effective for detecting whether patients are awake or sleeping [ 5 ].
Recommendations for BIS Monitoring
Based on the available evidence, BIS monitoring is recommended during general anesthesia to:
- Reduce the risk of intraoperative awareness: BIS monitoring can help reduce the risk of intraoperative awareness, particularly in patients at high risk [ 4 ].
- Improve early recovery times: The use of BIS monitoring has been associated with improved early recovery times, including shorter times to eye opening, orientation, and discharge from the postanesthesia care unit [ 2, 4 ].
- Guide anesthesia dosage: BIS monitoring can help guide the dose of anesthesia, leading to more effective and efficient anesthesia administration [ 2, 6 ].