British journal of anaesthesia
-
Researchers induced awake paralysis in 10 volunteers using separately both suxamethonium and rocuronium. Both the BIS A2000 (2003) and BIS Vista monitor (2013) were tested.
BIS decreased immediately after paralysis and did not fully recover until muscle recovery. BIS values decreased to as low as 44, despite the subject being awake.
In more than half of the 20 trials the BIS value decreased to below 60 at some point. In one case this lasted for almost 4 minutes, representing 76% of the total paralysis time for that subject.
summary -
The use of EEG monitors to assess the level of hypnosis during anaesthesia has become widespread. Anaesthetists, however, do not usually observe the raw EEG data: they generally pay attention only to the Bispectral Index (BIS™) and other indices calculated by EEG monitors. This abstracted information only partially characterizes EEG features. ⋯ EEG waveforms vary in the presence of noxious stimuli (surgical skin incision), which is not always reflected in BIS™, or other processed EEG indices. Spindle waves are adequately sensitive, however, to noxious stimuli: under surgical anaesthesia they disappear when noxious stimuli are applied, and reappear when adequate analgesia is obtained. To prevent awareness during anaesthesia, I speculate that the most effective strategy is to administer anaesthetic agents in such a way as to maintain anaesthesia at a level where spindle waves predominate.
-
Editorial Comment
Restrict relaxants, be aware, and know the limitations of your depth of anaesthesia monitor.
Interesting editorial accompanying Dr Peter Schuller's excellent study of BIS values in awake, paralysed volunteers.
The editors make a very interesting point critiquing the probabilistic, database-based approach to processed-EEG awareness monitors like BIS: (emphasis added)
summary"This database-driven approach may have limitations, in particular for the detection of intraoperative wakefulness: it is very unlikely that data from an awake and paralyzed subject are included in this database. Therefore, the resulting anaesthesia index has not been trained with a dataset that contains this clinical situation..."
-
Randomized Controlled Trial
Effect of propofol on the medial temporal lobe emotional memory system: a functional magnetic resonance imaging study in human subjects.
Subclinical doses of propofol produce anterograde amnesia, characterized by an early failure of memory consolidation. It is unknown how propofol affects the amygdala-dependent emotional memory system, which modulates consolidation in the hippocampus in response to emotional arousal and neurohumoral stress. We present an event-related functional magnetic resonance imaging study of the effects of propofol on the emotional memory system in human subjects. ⋯ NCT00504894.
-
Randomized Controlled Trial
Effect of subanaesthetic ketamine on plasma and saliva cortisol secretion.
The commonality between chronic conditions that are treated with low-dose ketamine, such as specific chronic pain conditions, depression, and post-traumatic stress disorder, can be found in relation to the stress system, particularly the hypothalamus-pituitary-adrenal axis. In this study we assess the effect of ketamine on the stress system by measuring plasma and saliva cortisol production during and following exposure to low-dose ketamine. ⋯ This study was registered in the Dutch Trial Register under number NTR2717 at www.trialregister.nl.