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Clin Toxicol (Phila). 2005;43(3):201-6.

Conservative management of delayed, multicomponent coagulopathy following rattlesnake envenomation.

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Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, University of California, Davis Medical Center, Sacramento, CA 95817, USA.



Crotaline Fab therapy is recommended for controlling local tissue effects, coagulation abnormalities, and other systemic signs following mild-to-moderate N American Crotaline envenomations. Occasionally, coagulation abnormalities emerge after control of tissue effects has been achieved. These coagulation changes range from minor, single parameter abnormalities to multicomponent, critical value derangements. The bleeding risk associated with these abnormalities is unknown, and dosing guidelines for Crotaline Fab therapy in treating coagulation abnormalities that are severe or delayed-in-onset have not been clearly established.


A 40-year-old man was envenomated in the right hand by a rattlesnake. Crotaline Fab therapy was started within 1 h of envenomation and arrest of edema progression was achieved by 48 h of admission. Although fibrinogen, platelet count, aPTT, and INR were all normal on initial assessment, hematologic changes were evolving over post-envenomation days 1 to 5 despite 32 vials of Crotaline Fab. The patient was transferred to our tertiary care center on the fifth postenvenomation day with a platelet count of 15,000/mm3 and unmeasurable values for fibrinogen, aPTT, and INR. The patient was managed with close observation alone, with no additional antivenom, and was discharged home on day 12 with no improvement in fibrinogen, aPTT or INR. Follow up lab assessment showed resolution of the hematologic effects sometime between day 17 and 37.


We report a case of rattlesnake envenomation with profound, delayed hematologic effects that were resistant to 32 vials of Crotaline Fab given over post-envenomation days 1 to 4. After day 4, no further attempt was made to achieve normal lab indices using antivenom. Close observation alone may be adequate in cases of multicomponent, critical value coagulopathies following rattlesnake envenomation as long as there is no evidence of bleeding and local tissue effects and systemic effects have been adequately controlled.

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