Automated responsiveness test and bispectral index monitoring during propofol and propofol/N2O sedation.
ABSTRACT Sedation practice, especially when non-anaesthesia personnel are involved, requires efficient anaesthetic depth monitoring. Therefore, we used prediction probability (PK) to evaluate the performance of the bispectral index (BIS) of the EEG and automated responsiveness test (ART) to predict sedation depth and loss of subject's responsiveness during propofol sedation, with and without N2O.
Twenty volunteers were studied during propofol administration with (N2O) and without (Air) N2O. The protocol consisted of sequential 15-min cycles. After a control period, propofol was infused to a target effect-site concentration of 0.25 microg/ml (N2O) or 1.5 microg/ml (Air), which was subsequently increased by 0.25 or 0.5 microg/ml, respectively, until loss of responsiveness was detected by loss of response to command [observer's assessment of alertness/sedation (OAA/S) score <or= 2].
Deeply sedated patients did not respond to ART indicating that the sensitivity was 1.0 with or without N2O. The specificity of ART was 0.24 with Air and 0.98 with N2O. The BIS was better than ART in predicting OAA/S score (PK = 0.84 vs. 0.77) and loss of responsiveness (PK = 0.87 vs. 0.69) during the Air trial. Nitrous oxide decreased the performance of BIS in predicting OAA/S score (PK = 0.76), but increased the performance of ART to predict loss of responsiveness (PK = 0.85).
BIS and ART comparably predict sedation and loss of responsiveness. However, ART, because of its resistance to false-normal responses, might prove to be more useful on an individual patient basis - especially in the presence of agents that impair BIS sensitivity.
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ABSTRACT: To test the hypothesis that sedation in elderly patients is often electrophysiologically equivalent to general anesthesia (GA). Prospective, observational study. Operating room of a university medical center. 40 elderly patients (>or=65 yrs of age) undergoing hip fracture repair with spinal anesthesia and propofol-based sedation. In the routine practice group (RP; n = 15), propofol sedation was administered per the usual routine of the anesthesiologist. In the targeted sedation group (TS; n = 25), sedation was titrated to an observer's assessment of alertness/sedation (OAA/S) score of 4 (ie, lethargic in response to name called) to 5 (ie, awake and alert). Both patient groups underwent processed electroencephalographic monitoring using bispectral index (BIS) intraoperatively. BIS levels were compared between groups to determine amount of surgical time spent in GA (BIS <or= 60). In the RP group, subjects spent 32.2% of surgical time at BIS levels consistent with GA. Although averaged BIS values during surgery increased from (mean +/- SD) 71 +/- 16 to 88 +/- 9 (P < 0.001), GA was still observed during 5% of surgical time in the TS group. Overall, 13 of 15 (87%) RP group patients and 11 of 25 (44%) TS group patients (P < 0.010) experienced some period of GA. BIS levels consistent with GA occur frequently in elderly patients during propofol-based sedation for spinal anesthesia. Altering routine practice such that sedation is titrated to a targeted clinically-determined sedation level reduces - but does not eliminate - this incidence.Journal of clinical anesthesia 05/2010; 22(3):179-83. DOI:10.1016/j.jclinane.2009.06.005 · 1.21 Impact Factor
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ABSTRACT: An increasing number of minimally invasive diagnostic and therapeutic procedures are susceptible to be performed under sedation, but the depth varies between light (anxiolysis) and deep (general anesthesia). Evaluation of the sedation's depth is of primary importance because it determines not only surgeons and patients’ comfort, but also the incidence of related side effects. Clinical appraisal based on the MOAA/S (Modified Observer's Assessment of Alertness/Sedation) scale is the method most commonly used to discriminate between light/moderate and deep sedation levels (grade 2 = abolition of response to verbal stimulations). Monitoring of the cerebral electrical activity provides values correlated with the depth of sedation but is not reliable enough to significantly discriminate between light and deep sedation because of intra- and inter-individual variabilities. Monitoring of the plasmatic or alveolar concentrations of hypnotic agents could be a valuable indication only if a single drug is used.Le Praticien en Anesthésie Réanimation 04/2014; DOI:10.1016/j.pratan.2014.02.005