Depth of Anesthesia: Difference between revisions

Heart rate, blood pressure, purposeful movement and end tidal anesthetic concentration (ETAC) may be useful in recognizing awareness during general anesthesia. However, some drugs may mask these signs (calcium channel blockers, neuromuscular blockers).

Processed EEG monitor, translating EEG waves into a numeric scale ranging from 0 (complete EEG suppression) to 100 (fully awake). It is said that adequate anesthesia may be present with a BIS value of 40-60. Studies have shown that intraoperative BIS, compared to clinical signs, may have a reduction of intraoperative awareness (OR) 0.36, 95% CI 0.21 to 0.60; I2 = 61%; 27 studies; 9765 participants<ref name=":0">https://pubmed.ncbi.nlm.nih.gov/31557307/</ref>, time to eye opening, time to orientation, and time to discharge patient from PACU<ref name=":0" />. However, BIS guided anesthesia did not show a clinical difference to anesthesia guided by end tidal anesthetic gas concentration (ETAC). Furthermore, studies show that neuromuscular blockade alone, without other anesthetics, decrease the value of BIS.<ref>Schuller PJ, Newell S, Strickland PA, Barry JJ. Response of bispectral index to neuromuscular block in awake volunteers. Br J Anaesth. 2015 Jul;115 Suppl 1:i95-i103.</ref> Therefore, the accuracy and reliability of BIS are questionable.