LAUSR

Bispectral index (BIS) monitoring can be used to help assess the hypnotic component of general anesthesia, but its use varies widely. Using retrospectively collected intraoperative data on 55,210 surgical cases at a tertiary care hospital, Gelfand et al. [1] found the following factors to be related to BIS usage: increased age, greater ASA physical status, extremes of BMI, use of TIVA, use of a long-acting paralytic agent, use of an endotracheal tube, emergency surgery, increasing length of case, and certain surgical services. BIS use was also associated with previously documented risk factors for intraoperative awareness. These factors are also indicators of case complexity, which by itself increases the likelihood of using BIS. Giménez et al. [2] examined the intriguing possibility of expanding the use of the BIS monitor beyond monitoring the intra-operative hypnotic state. They found the BIS index to be highly correlated with the hypnogram obtained during polysomnography. They suggest to explore the use of BIS to monitor sleep depth in the intensive care units, to reduce polysomnography derived costs, and to increase accessibility of sleep monitoring in ambulatory care. When surgery involves the forehead and BIS electrodes cannot be used, auditory evoked potentials with registering electrodes placed at the nose may provide a useful alternative to monitor electrical activity in the brain (Ishioka et al. [3]). Melia et al. [4] used different components of the EEG signal to try to selectively monitor the hypnotic and analgesic component of anesthesia, referred to as the qCON and qNOX indices, respectively. In 140 patients undergoing general anesthesia with propofol and remifentanil, the qCON and qNOX index did show different performances in the detection of loss of consciousness and loss of response to noxious stimuli during induction and recovery of consciousness: the qCON decreased faster during induction and the qNOX increased faster at the end of the surgery, which is congruent with the thesis that loss of response to stimuli (analgesic effect) is reached after the loss of consciousness (hypnotic effect) and that a higher probability of response to stimuli might be reached before the recovery of consciousness, respectively. Pupillometry has gained considerable attention over the last several years as a tool to monitor the analgesic component of anesthesia (or the nociception/anti-nociception balance). Shirozu et al. [5] demonstrate that the components of the anesthetic mixture (opioids, inhaled agents, propofol) differently affect several pupillometry components. For example, the authors suggest that the difference in pupil reactivity between inhalational anesthetic and propofol may indicate these drugs differently affect midbrain reflexes. Heart rate variability, an index of the sympathetic/parasympathetic balance, continues to be explored as an index of the nociception/anti-nociception balance or as a predictor of hypotension after spinal anesthesia (Prashanth et al. [6]). Hight et al. [7] studied the relationship between return of the forehead EMG during emergence from anesthesia with inhaled agents and the effect site minimum alveolar concentration (MAC) or CeMAC. The authors found that patients emerging from general anesthesia with an endotracheal tube Most anesthesia related submissions to the Journal of Clinical Monitoring and Computing pertain to depth of anesthesia monitoring. Anesthesia machine related submissions remain notably scarce.