Low peripheral perfusion index values may indicate the need for antivenom in the early phase of scorpion envenomation

Scorpion envenomation may cause local symptoms as well as life-threatening situations including shock, and death. Antivenom administration is the cornerstone of therapy, meticulous patient selection is needed because of the possible side effects of the antivenom including anaphylaxis. Peripheral perfusion index (PPI) is a simple, non-invasive test that is widely used for the detection of peripheral hypoperfusion. We aimed to investigate the value of using PPI to predict the need for antivenom administration for scorpion envenomation.

This prospective observational study was conducted in the ED of a tertiary care center. We consecutively enrolled patients with scorpion envenomation on the extremities who are over 18 years old without pregnancy and a peripheral arterial disease between March 1, 2021, to October 31, 2021. Demographics included age, sex, sting zone, the time between sting and the ED admission, and vital parameters, we blindly measured PPI both on affected and contralateral extremities before any therapeutic intervention. We compared PPI levels, vital parameters, and the outcome including discharge from the ED, admission to ward or ICU, and death between patients who received antivenom and those who did not.

Twenty-nine male (58.0%) and 21 (42.0%) female patients with scorpion envenomation were enrolled in the study. The median age was 46.5 [IQR 33.3]. Thirty-eight (76.0%) patients had Class I, 12 (24.0%) patients had Class II and III envenomation. The median duration of the ED admission after the sting was 90 [IQR 120] minutes. Antivenom was administered in 13 (26.0%) patients. PPI was significantly lower both on the affected and the contralateral extremities (p = 0.043 and p = 0.045, respectively) in patients who required antivenom. With a cut-off value of 2.4, PPI can predict the need for antivenom with a sensitivity of 61.54%, a specificity of 86.5%, a positive likelihood ratio of 4.55, a negative likelihood ratio of 0.44, a positive predictive value of 61.54%, a negative predictive value of 86.49%, and an accuracy of 80% (AUC 0.691, p < 0.05).

PPI can better reflect the ongoing systemic inflammation and the need for antivenom compared to other vital parameters. Therefore, we suggest this noninvasive and objective test may have a significant role in detecting patients who need antivenom in the early phase of scorpion envenomation. However, more studies are needed to elucidate the role of PPI in scorpion envenomation.