Relationship between the patient state index and sedation scale during dexmedetomidine sedation during spinal anesthesia

Background & Objectives: Dexmedetomidine, a highly selective alpha-2 adrenoceptor agonist, is a widely used sedative during spinal anesthesia. Indices devised using processed electroencephalographic monitors are useful for identifying the level of sedation without disturbing the patient. However, we lack studies on the relationship between the patient state index (PSI) and dexmedetomidine sedation. We investigated the relationship between the PSI and sedation scale during dexmedetomidine sedation in patients undergoing spinal anesthesia.Methodology: This study entailed a review of the anesthetic records of patients who underwent dexmedetomidine sedation under SEDLineTM monitoring. After intrathecal injection, dexmedetomidine 1 mu g/kg was injected intravenously over 10 min, followed by maintenance infusion at 0.4 mu g/kg/h for 50 min. The PSI, mean blood pressure, heart rate, and oxygen saturation were recorded at regular intervals. The patients' 'Observer's Assessment of Alertness/Sedation' (OAA/S) scores were measured repeatedly until deep sedation (OAA/S <= 2) was achieved. The Spearman test was used to evaluate the correlation between the PSI value and OAA/S score. The cut-off PSI value for identifying OAA/S scores <= 2 was calculated using receiver operating characteristic curve analysis.Results: The PSI values corresponding to OAA/S scores of 5, 4, 3, 2, and 1 during dexmedetomidine sedation were 86.56 +/- 10.45, 76.90 +/- 13.99, 68.16 +/- 16.18, 61.48 +/- 15.26, and 55.67 +/- 16.75, respectively (P < 0.001). The Spearman correlation coefficient for the PSI and OAA/S scores was 0.6228 (P < 0.001). The cut-off value of PSI for OAA/S scores <= 2 was 76. The mean blood pressure and heart rate decreased significantly compared to baseline and 60 min after continuous dexmedetomidine infusion (P < 0.001).Conclusion: The patient state index decreased with the progression of dexmedetomidine sedation. Patient state index assessment could prove useful for evaluating the depth of sedation without distressing the patients.Abbreviations: BIS: Bispectral index; Dex: Dexmedetomidine; EEG: Electroencephalography; OAA/S: 'Observer's Assessment of Alertness/Sedation'; PSI: Patient state index; SA: Spinal anesthesia