Background: Serum fibrinogen of less than 100 mg/dL is recommended for predicting systemic bleeding risk in hematotoxic snake bite patients, but it is not widely available. Data on using venous clotting time (VCT), 20-minute whole blood clotting test (20WBCT), platelets, prothrombin time (PT), international normalized ratio (INR), and partial thromboplastin time (PTT) to predict systemic bleeding in hematotoxic snake bite patients are limited.

Objective: To determine association between clotting tests (VCT, 20WBCT, platelets, PT, PTT, and INR) and 1) serum fibrinogen of less than 100 mg/dL, and 2) systemic bleeding in patients bitten by green pit viper (GPV) or Russell’s viper (RV).

Materials and Methods: This prospective cohort study included patients bitten by GPV or RV at Sawanpracharak Hospital, Nakhon Sawan, Thailand, between October 2016 and December 2017. Patient’s blood specimens were collected for fibrinogen, PT, INR, PTT, platelet count, VCT, and 20WBCT at initial presentation and every six hours until 24 hours of admission, or patients’ recovery. The association were determined by using Fisher’s exact test.

Results: There were 30 patients, 21 were bitten by GPV, and nine were bitten by RV. One hundred sixty-one sets of blood specimens were collected. There were four cases with systemic bleeding. Factors associated with fibrinogen of less than 100 mg/dL were VCT of 20 minutes or more (p=0.01), unclotted 20WBCT (p=0.01), PT of more than 13 seconds (p=0.04), and INR of 1.2 or more (p<0.01). Factors that associated with systemic bleeding were VCT of 20 minutes or more (p<0.01), unclotted 20WBCT (p<0.01), INR of 1.2 or more (p=0.04), and fibrinogen of less than 100 mg/dL (p=0.01).

Conclusion: VCT of 20 minutes or more, unclotted 20WBCT, and INR of 1.2 or more are associated with serum fibrinogen less than 100 mg/dL and systemic bleeding in GPV and RV envenomation.

Keywords: Green pit viper, Russell’s viper, Fibrinogen, 20WBCT, VCT

Received 29 Apr 2019 | Revised 26 Jun 2019 | Accepted 3 Jul 2019