Introduction:
The Vipera berus (common viper) is the only species of venomous snake found in Poland. The aim of this study was to determine to what extent coagulopathy has occurred as a post-bite complication.

Material and methods:
The medical records of 138 adult patients in the Sucha Beskidzka hospital with the diagnosis of snake bite between 2001–2014 were retrospectively analyzed. Demographic, clinical and laboratory data were collected. Antivenom was given to all patients, except one, with snake bites, but laboratory test were taken prior to administration of antivenom. Obtained results were compared to those of the control group, composed of 176 adults hospitalized in the same period for an elective laparoscopic cholecystectomy.

Results:
The mean platelet count in the study group was 239.94×109/L (SD=56.56) and 248.77×109/L (SD=57.82) in the control group. In 98% of the study group and 100% of the control group the platelet value (PLT) fell within laboratory norms (130 to 420×109/L), 2 patients after snake bites had a PLT lower than normal, and thrombocytosis was not observed in either group. A reference range of 0.85–1.3 INR below normal was found in 2 patients in the study group and 15 from the control group, while values above the normal range were found in 8 patients (6.7%) from the snake bite group and no patients from the control group. In the study group, the INR ranged from 0.78–1.43 with a mean of 1.046 (SD=0.14), while in the control group the range was from 0.79–1.28, with a mean of 0.95 (SD=0.08). There was a significant difference in INR between the study and control groups (p<0.0001).

Conclusions:
The bite from V. berus does not result in severe thrombocytopenia, with only a moderate increase in INR values observed in about 7% of patients.