The venom of North American crotalines contains anticoagulants, procoagulants, fibrinolysins and hemorrhagins, as well as components that alter endothelial and platelet function. Effects include thrombocytopenia, prolonged PT and PTT, fibrinolysis, hypofibrinogenemia, and hypoprothrombinemia. Recurrence of these effects has been described after cessation of Fab antivenom treatment. This case illustrates an obscured presentation of envenomation and a common decision-making problem with recurrent hematologic effects. Case Report: An 80-year-old female, with a history of hypertension, presented after having fallen in her kitchen, sustaining a laceration to the back of her scalp. On presentation, she was confused, diaphoretic, and hypotensive, with a systolic BP 65 mmHg. She was given an IV NS bolus and started on dopamine. Two punctures at the base of her right thumb were noted, with swelling and ecchymosis of the hand. History was obtained from her of gardening a short time before her fall and possibly being bitten on the hand by something unseen. Initial lab showed platelets 15,000/mm 3 , serum fibrinogen 115 mg/dL, and INR 1.8. A presumptive diagnosis of rattlesnake bite was made. She was treated with 6 vials of ovine Fab antivenom (CroFab ®) over an hour, and then 2 vials every six hours for three additional doses. A CT scan of the head showed no intracranial bleeding. Blood pressure stabilized to 92/48, and continued to improve following antivenom. Progression of swelling stopped at the level of the elbow and did not recur. Platelets rebounded within the hour to 230,000/mm 3 , but fibrinogen continued to fall, with a nadir of 65 mg/dL and the INR increased to a maximum of 2.3. Dopamine was discontinued on hospital day 2. At discharge on hospital day 5, fibrinogen was 338 mg/dL, INR 1.1 and platelets 140,000/mm 3. Two days post-discharge, the patient had a recurrent hypofibrinogenemia of 50 mg/dL. INR was 1.2 and platelets 177,000/mm 3. She had hematuria on urine dipstick, was given two vials of antivenom IV, and followed daily. Fibrinogen was 110 mg/dL the following day and remained in that range for several more days. She had no recurrence of thrombocytopenia or elevation of her INR, hematuria did not recur, and she did not have clinically significant bleeding at any time in her course. Discussion: Recognition of signs and symptoms of a rattlesnake envenomation in an endemic area, and rapid response to crotaline antivenom, confirms the diagnosis. Although early, severe hematologic effects are risk factors for late, severe recurrence of the same components, this patient had a recurrence only of one of her hematologic abnormalities, demonstrating the unpredictable nature of this phenomenon. Neutralization, exhaustion or persistence of particular venom components will determine the specific clinical effects. This patient improved following additional antivenom given in response to recurrence of severe hypofibrinogenemia and evidence of bleeding. Conclusion: Recognition of crotaline envenomation is critical in end...
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