Pulse co-oximetry perfusion index as a tool for acute postoperative pain assessment and its correlation to visual analogue pain score

Abstract

Background A painful stimulus can produce vasoconstriction and a decrease in perfusion index (PI). The visual analogue scale (VAS) is the most common pain assessment scale. However, it is affected by psychometric instability. This study was designed to evaluate the correlation between VAS as a subjective indicator of pain and PI as an objective indicator of pain. Patients and methods At postanesthesia care unit, a Masimo pulse co-oximetry perfusion index was attached to 70 adult patients of ASA I who underwent lumbar spine discectomy. At the time of the first request for analgesia (T1) VAS was recorded together with the PI, heart rate (HR), mean arterial blood pressure (MAP), peripheral oxygen saturation, and axillary temperature, following which analgesia was given. Thirty minutes thereafter (T2) second measurements for the mentioned parameters were taken. Results The PI was significantly higher at T2 than at T1 (mean increase% = 94.3 ΁ 82.7%). This increase was associated with a statistically significant decrease in VAS, HR, and MAP. The mean decrease% was 70.5 ΁ 19.88%, 11.1 ΁ 7.2%, and 3.96 ΁ 5.01% in VAS, HR, and MAP, respectively. This means that the PI increases with adequate relief from pain, as indicated by a decrease in VAS, HR, and MAP. A decrease in VAS was associated with an increase in PI, but the correlation was not statistically significant as the degree of the increase in PI in relation to the decrease in VAS was variable among patients. Conclusion PI can be added to other indicators of pain assessment in the postanesthesia care unit.