Perfusion index versus visual analogue scale: as an objective tool of renal colic pain in emergency department

Perfusion index (PI) has use to monitor sympathetic response changes to pain. In this study, we aimed to evaluate the utility of using perfusion index as an objective marker of pain relief and of the need for rescue analgesia in ED patients with documented renal colic.

We conducted a prospective observational study between January 2020 and December 2020. The demographic characteristics of the patients, their complaints, nephrolithiasis histories, vital signs, PI, and VAS scores (on admission and after treatment) were recorded.

A total of 144 patients were included. All patients were administered 20 mg of Tenoxicam on admission. There was a statistically significant difference between the PI (<0.001) and VAS scores (<0.001) on admission and after the administration of Tenoxicam. 43.1% (n = 62) of the patients needed rescue analgesia. Accordingly to ROC curve, the ability of both PI₂ (AUC: 0.615, 95%CI 0.519-0.711, p = 0.018) and ΔPI (AUC: 0.601, 95%CI 0.508-0.694, p = 0.039) indices were determined as statistically significant. The cutoff value of the PI₂ level for the prediction of the needed rescue analgesia was 4.65 and the cutoff value for ΔPI (PI_2-PI₁) was 2. All patients had a pain VAS score of <3 and a mean PI of 5.7 ± 2.9 at discharge from the emergency department.

In patients presenting to the emergency department with renal colic, the PI value on admission and after analgesic therapy can be helpful in assessing the severity of pain and predict the need for rescue analgesia.