• S Rinaldi, G Consales, E Gallerani, O Ortolani, and A R De Gaudio.
• Department of Critical Care, Section of Anaesthesiology and Intensive Care, University of Florence, Viale Morgagni 85, 50125 Florence, Italy.
• Acta Anaesthesiol Scand. 2005 May 1;49(5):692-7.

BackgroundA-line autoregression index (AAI) is a parameter derived from auditory evoked potentials proposed as depth of anaesthesia monitor. We evaluated the effects of AAI guidance on sevoflurane consumption, emergence time, explicit and implicit memory.MethodsOne hundred patients submitted to major abdominal surgery were randomized into two groups. In group A (n = 50), sevoflurane was titrated according to AAI (target = 20 +/- 5), in group B (n = 50) according to clinical signs. Anaesthesia was induced with fentanyl, propofol, atracurium and maintained with sevoflurane. The mean value of sevoflurane consumption (g/min) and emergence time has been assessed in both groups. After emergence, A test of explicit memory was administered. We assessed implicit memory using a category generation test.ResultsIn group A, mean sevoflurane consumption was significantly (P = 0.0001) reduced by 20.4% and mean emergence time was significantly (P = 0.00012) shorter by 2 min with respect to group B. No patients experienced explicit memory while the difference between the two groups in implicit memory results was not significant (P = 0107).ConclusionsAAI titration of anaesthesia allows a significant reduction in sevoflurane consumption and emergence time without significant effects on the incidence of explicit and implicit memory. Nevertheless the relationship between AAI and memory requires studies in larger groups of patients.

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