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A Journal on Anesthesiology, Resuscitation, Analgesia and Intensive Care
Minerva Anestesiologica 2009 December;75(12):692-7
Relationship between A-line Autoregressive Index, Spectral Entropy and steady state predicted site-effect effective concentrations at 05-50-95 of propofol at different clinical endpoints
Iannuzzi E. 1, Iannuzzi M. 4, Mora B. 3, Sidro L. 1, Berrino L. 2, Chiefari M. 1, Tufano R. 4
1 Department of Anesthesiological, Surgical and Emergency Sciences, Second University of Naples, Naples, Italy;
2 Department of Experimental Medicine, Pharmacology Section, Second University of Naples, Naples, Italy;
3 Department of Anesthesia and Intensive Care, University of Vienna Hospital, Vienna, Austria;
4 Department of Anesthesia and Intensive Care, Federico II University Hospital, Naples, Italy
AIM: Target controlled infusion intravenous anesthesia is a growing phenomenon. Nowadays, many anesthesiologists feel the need to monitor depth of anesthesia during total intravenous anesthesia, even though it is not a standard technique worldwide. Spectral Entropy (SE) is a relatively new depth of anesthesia index. The aim of this study was to investigate whether predicted site-effect propofol concentrations, A-line Autoregressive Index (AAI) and SE values are useful for predicting loss of verbal contact (LVC) and loss of consciousness (LOC) during steady-state conditions.
METHODS: Forty-four patients scheduled for elective major abdominal surgery were recruited. All patients were unpremedicated. A target controlled infusion of propofol was administered using Schnider’s pharmacokinetic model. The initial propofol infusion provided a site-effect concentration of 1.0 mcg mL-1, and was increased stepwise by 1.0 mcg mL-1 every 4 minutes until the concentration reached 6.0 mcg mL-1. A 4 minute interval was chosen to assure that steady state site-effect concentrations were obtained. AAI, SE and propofol site-effect concentrations were recorded when LVC occurred and also when LOC occurred. Population values for predicted site-effect concentrations at the clinical endpoints were estimated and correlated with AAI and SE values.
RESULTS: In our study for LOC the effect-site concentration to include 90% of patients was 5.85 ?mcg mL-1 (5.70-5.90) and 3.4 mcg mL-1 (3.24-3.60) for LVC. In this study, 90% of patients lost verbal contact at an AAI value of 68 (64.6-71.4) and an SE value of 68.2 (66.2-70.2). LOC occurred in 90% of patients at an AAI value of 39.2 (37.2-41.1) and an SE value of 40.2 (38.1-41.3).
CONCLUSIONS: LOC and LVC occur within a defined range of predicted site-effect concentrations. More emphasis should be given to site-effect concentrations. SE and AAI have similar values at different endpoints and similar correlation with Ceprop. AAI and SE are both useful tools in predicting both LVC and LOC.