Abstract
Objective: To study the correlation between, propofol effect-site concentration (Ce prop), Bispectral Index (BIS) and Spectral entropy (state/response, SE/RE), as well as to investigate their threshold values best to detect the desired level of propofol sedation, during spinal anesthesia.
Design: Observational study
Setting: King Fahad Hospital of Dammam University-Saudi Arabia
Subjects: Thirty patients scheduled for total knee replacement under combined spinal epidural anesthesia
Intervention(s): After spinal anesthesia, propofol sedation using target-controlled infusion (TCI) was started at 0.5 mu g/ml and increased incrementally by 0.5 mu g/ml. Depth of sedation was evaluated, as well as, BIS, SE and RE every 5 min after each Ce prop equilibrium.
Main outcome measure(s): The correlation between BIS, SE, RE, and Ce prop with different level of sedation score. Also the cut off values of BIS, SE, RE, and Ce prop best to detect the desired level of sedation.
Results: The changes of Ce prop significantly correlated with the changes of BIS, SE and RE values. All are significantly correlated with the changes in the Observer's Assessment of Alertness and Sedation (OAA/S) score. The cut-off values for Ce prop., BIS, SE and RE corresponding to the desired OAA/S score were, 1 mu g/ml, 75, 75 and 85 respectively, with SE showed significant higher specificity at the level of 100% sensitivity.
Conclusion: During spinal anesthesia under propofol sedation, BIS, SE, RE and Ce propofol were equally correlated with OAA/S score. At 100% level of sensitivity, SE showed the highest specificity, whereas the Ce propofol had the lowest specificity to detect the desired level of sedation.