Bleeding Following Rattlesnake Envenomation in Patients With Preenvenomation Use of Antiplatelet or Anticoagulant Medications

Abstract

Objectives: Rattlesnake envenomations commonly produce coagulopathy and thrombocytopenia, yet clinically significant bleeding is uncommon. It is unknown if patients who use antiplatelet or anticoagulant medications prior to envenomation are at increased risk for bleeding after envenomation.Methods: This was a retrospective cohort study of patients age 14 years and older who were admitted to a single academic medical center for rattlesnake envenomation. Patients who reported use of antiplatelet or anticoagulant medications prior to envenomation were compared to patients not on those medications. Severity and timing of bleeding was compared between groups, as was a composite endpoint of major bleeding at any time, shock, readmission, or death.Results: A total of 319 patients met inclusion criteria; 31 (9.7%) were documented to be taking antiplatelet or anticoagulant medications including aspirin, clopidogrel, and/or warfarin. Seventeen of the 319 patients developed bleeding associated with envenomation (major = 9; minor = 4; trivial = 4), with major bleeding occurring in five patients on antiplatelet or anticoagulant medications versus four patients not on antiplatelet or anticoagulant medications (p < 0.001). Seven of the 17 presented with early bleeding. This early bleeding occurred in three of 31 (9.7%) patients on antiplatelet or anticoagulant medications and four of 288 (1.4%) patients not on antiplatelet or anticoagulant medications (relative risk [RR] = 6.9; 95% confidence interval [CI] = 1.6 to 29.4; p = 0.022). Clinical outcome data were available for 300 of the 319 (94%) subjects following discharge. Late bleeding (bleeding after discharge from the index hospitalization) occurred in nine subjects, one of whom also had early bleeding (major = 2, minor = 3, trivial = 4). Three of these nine subjects with late bleeding were on antiplatelet or anticoagulant medications, compared with six not on antiplatelet or anticoagulant medications (p = 0.042). Both cases of late major bleeding occurred in patients on antiplatelet or anticoagulant medications. Therefore, among patients with follow-up data available, the overall rate of bleeding (early and late) was seven of 28 (25%) in patients taking antiplatelet or anticoagulant medications and 10 of 273 (3.7%) in patients not taking antiplatelet or anticoagulant medications (p < 0.001). The use of antiplatelet or anticoagulant medications was also associated with an increased risk of reaching the composite endpoint of major bleeding, shock, readmission, or death (6 of 31, or 19.4% vs. 14 of 288, or 4.9%; RR = 3.98; 95% CI = 1.65 to 9.62; p = 0.008). Conclusions:The risk of developing bleeding following rattlesnake envenomation is increased in patients who use antiplatelet or anticoagulant medications. This risk is greatest early after envenomation during the index hospitalization. However, risk of late, major bleeding appears also to be greatest in patients on antiplatelet or anticoagulant medications. Extra vigilance should be taken in patients on antiplatele...

The Epidemiology, Clinical Course, and Management of Snakebites in the North American Snakebite Registry

“…Only a single patient out of 450 was reported to develop a major late bleeding complication. This low incidence is consistent with two previous studies which found very low rates of late major bleeding complications [10,27].…”

“…Early nuisance-type bleeding was reported in 6.3% of cases. A previous large retrospective review of patients with rattlesnake envenomation in Arizona found only 2.0% of patients to have early bleeding [10]. Considering that the NASBR population includes copperhead and cottonmouth envenomations, which are less likely to experience bleeding due to the lower incidence of venom-induced coagulopathy and thrombocytopenia, our rate of bleeding is surprisingly high.…”

“…Despite approximately 5000 cases of venomous snakebite reported to poison centers each year, even the largest published case series and studies are generally limited to a few hundred cases. In such reports, cases often derive from a single center or geographic region [1,[7][8][9][10]. While clinical trials of antivenom may better represent the geographic diversity of species responsible for snakebite in the US, these studies also tend to be limited by small numbers [2,11].…”

“…Patients who take anticoagulant or antiplatelet medications have been reported to have greater bleeding risk following rattlesnake envenomation than patients not on these medications [10]. In the NASBR, there were 27 (6.0%) patients taking anticoagulants or antiplatelet medications and only one was reported to have nuisance bleeding at initial presentation.…”

Envenomation by Trimeresurus stejnegeri stejnegeri: clinical manifestations, treatment and associated factors for wound necrosis

“…The mechanism might have involved platelet aggregation/agglutination and the action of SVMPs on the microvessel wall [ 48 , 49 ]. Antiplatelet therapy may worsen severe bleeding [ 50 ], while administration of FFP in patients with T . s .…”