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Relationship Between Patient State Index and Richmond Agitation Sedation Scale for Sedation in Critically Ill
Nishant Kumar1, Kritika Tiwari1, Maitree Pandey1
1Lady Hardinge Medical College and Associated Hospitals, Department of Anaesthesiology and Critical Care, New Delhi, India.
Objective:
The objective of this study was to find the relationship between Patient State Index (PSI) and Richmond Agitation Sedation Scale (RASS) for sedation in critically ill patients.
Methods:
This was a prospective, observational study. Thirty-five patients were recruited to assess the correlation between PSI and RASS scores of 0 to -3 for sedation in mechanically ventilated, critically ill patients. Paired observations (RASS and PSI) were made for each patient every 4 hours for at least 72 hours or until discontinuation of monitoring, whichever occurred earlier. Appropriate statistical analyses were applied; a P < 0.05 was considered significant.
Results:
Out of the expected 665 pairs of observations, only 608 pairs were observed. The median PSI value with all sedation regimen was 72 with an interquartile range of 60 and 86 (1st and 3rd quartile) respectively. There was significant and strong correlation between PSI and RASS 0 to -3 with Spearman correlation coefficient of 0.822; R2=0.675 (P < 0.001) which dropped to 0.786 with repeated measures correlation. The sensitivity and specificity were 88.66% and 88.57%, respectively, with an area under the receiver operating characteristic curve of 0.947; these improved to 100% and an area under the curve of 1 when analysed per patient. To maintain RASS between 0 and -3, the PSI cutoff was found to be 50-52.
Conclusion:
PSI correlates well with RASS across sedation regimens in critically ill patients and assists in monitoring of sedation. Adequate sedation to reach an RASS of 0 to -3 may be achieved at a PSI of 50-52. However, these findings are preliminary and require validation in larger cohorts.
