Hump-nosed pit viper (Hypnale hypnale) envenoming causes mild coagulopathy with incomplete clotting factor consumption

Abstract

Context. Limited information exists on the coagulopathy caused by hump-nosed pit viper (Hypnale hypnale) envenoming. Objectives. This study aimed to characterise the coagulopathy in hump-nosed pit viper bites by measuring laboratory clotting times and factor studies. Materials and methods. Cases of hump-nosed pit viper envenoming were included from a prospective cohort study of Sri Lankan snake-bite patients. Patient age, sex, snake identification, time of bite and clinical effects were recorded. Patients did not receive anti-venom because no specific anti-venom to hump-nosed vipers exists. All patients received supportive care and serial 20-min whole blood clotting tests (WBCT20). The prothrombin time (PT), international normalised ratio (INR), activated partial thromboplastin time (aPTT), coagulation factors I, II, V, VII, VIII, IX and X, von Willebrand factor (vWF) antigen and D-Dimer concentrations were measured. The median of highest or lowest test result for each patient was reported with interquartile range (IQR). Results. There were 80 hump-nosed pit viper bites, median age was 37 years (IQR: 26–51 years) and 48 were male. The WBCT20 was positive in one patient. The median highest INR was 1.9 (1.5–2.2; Range: 1.3 to > 12) and median highest aPTT was 54 s (46–72 s; Range: 35–170 s). There was low fibrinogen [median: 1.3 g/L;1, –1.8 g/L; Range: < 0.2–2.9], low factor VIII levels [median: 23%; 16–37%] and low factor V levels [median: 43%; 23–74%]. D-Dimer concentrations [median: 3.4 mg/L; 2–7.4 mg/L] were slightly elevated. Factors II, VII and X and vWF antigen concentrations were normal. Discussion and Conclusions. Hump-nosed pit viper bites result in a mild coagulopathy which is usually not detected by a WBCT20. It is characterised by mild elevation of INR, low fibrinogen and Factors V and VIII which may be consistent with the venom containing a thrombin-like enzyme.

Keywords:

• Clotting factors
• Hypnale
• Hump-nosed viper
• Coagulopathy
• Snake envenoming
• Venom

Acknowledgements

We acknowledge the assistance of the medical and nursing staff at Chilaw hospital, Central West Province, Sri Lanka for identifying patients for the study. We acknowledge Andrew Dawson for assistance throughout the study.

Ethical statement

The study was approved by the Ethical Review Committee, Faculty of Medicine, University of Colombo.

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

The study was supported in part by NHMRC Project Grant 631073 and by IRQUE Project Grant C1A2 MBBS SPQEF. Geoff Isbister is funded by an NHMRC Clinical Career Development Award ID 605817. C. Ariaranee Gnanathasan is funded by an IRQUE Project.