Comparison of Pain Assessment Tools and Numeric Rating Scale Thresholds for Analgesic Administration in the Postanaesthetic Care Unit.

Purpose: The aim of this study was to assess the correlation between the Visual Analog Scale (VAS), Numeric Rating Scale (NRS), and Verbal Rating Scale (VRS). Additionally, the study aimed to determine NRS threshold values for both mild analgesic administration (= without risk of nausea and vomiting [NV] side effects) and strong analgesic administration (= with risk of NV side effects) in the postanaesthetic care unit (PACU).

Design: Prospective, observational study design.

Methods: The study was conducted between August 2019 and April 2022. Patients scheduled for elective surgery under general anesthesia were included. The primary outcome was the correlation between the VAS, NRS, and VRS, assessed at PACU admission and discharge. Secondary outcomes included pain evolution, desire for analgesic administration with or without risk of NV side effects, and preferred tool for pain assessment.

Findings: VAS, NRS, and VRS were significantly correlated (r = 0.82 to 0.94, P < .001) at both PACU admission and discharge. The median VAS scores significantly improved from 32 (interquartile range [IQR]: 9 to 22) at PACU admission to 27 (IQR: 8 to 39) at PACU discharge (P < .001), while the median NRS scores significantly improved from 3 (IQR: 1 to 6) at PACU admission to 3 (IQR: 1 to 4) at PACU discharge (P < .001). At PACU admission, receiver-operating characteristics curve analysis indicated that an optimal NRS threshold value for the administration of a mild analgesic (= without risk of NV side effects) was greater than 2, and greater than 5 for the administration of a strong analgesic (= with risk of NV side effects). At PACU discharge, patients reported a preferred median NRS score of 5 to be treated with a mild analgesic (= without risk of NV side effects), and a preferred median NRS score of 8 to be treated with a strong analgesic (= with risk of NV side effects).

Conclusions: All three pain assessment tools can be used to evaluate postoperative pain in the PACU setting during the recovery from general anesthesia.