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snakebite

Etiology: 1) pit vipers (Crotalidae) - 99% of snakebite poisonings in U.S. - Russell's viper (India) - saw-scaled viper (India) 2) coral snakes (Elapidae) 3) sea snakes 4) cobra (India) 5) krait (India) Epidemiology: 1) 8000-10,000 snakebites annually; 10-15 deaths annually U.S. 2) worldwide, 65,000 deaths (2019). 81% in India [4] - in India, cobra & krait (neurotoxic venom) & Russell's viper & saw-scaled viper (hemotoxic venom) account for 90% of deaths [4] - neurotoxic snakes with double the case-fatality rate of hemotoxic snakes (8.8% vs 4.2%) [4] 3) southeastern & gulf states have highest per capita incidence 4) most snakebites occur from April to October with peak months July & August Pathology: - hemotoxic vemom: clotting disorders estimated to occur in 40%-90% - neurotoxic venom: respiratory failure, paralysis, vision disturbance [4] Laboratory: 1) complete blood count (CBC) with differential & peripheral smear a) hemolysis b) leukocytosis (20,000-30,000/mm3) c) thrombocytopenia 2) prolonged PT/PTT 3) DIC panel: 1) decreased plasma fibrinogen 2) increased fibrin degradation products (D-dimer) 4) type & screen 5) serum chemistries a) increased serum urea nitrogen b) increased serum creatinine c) serum electrolyte abnormalities d) increased serum transaminases e) increased serum bilirubin f) increased serum creatine kinase 6) urinalysis a) proteinuria b) hematuria Special laboratory: - electrocardiogram Complications: - long-term health effects may occur - chronic kidney disease - skin necrosis - amputation [4] Staging: Grading of envenomation: - Grade 0: no envenomation: no local or systemic manifestations - Grade 1: minimal envenomation: local pain & edema, no systemi manifestations - Grade 2: moderate envenomation: local & mild systemic manifestations &/or positive laboratory findings - Grade 3: severe envenomation: local, systemic & laboratory abnormalities Management: 1) in the field a) reassurance b) immobilization of affected extremity c) exertion will increase systemic absorbtion d) wide constriction bands may prevent lymphatic drainage without compromising blood flow e) use of tourniquets is discouraged f) incision & suction not indicated g) transport to nearest available hospital 2) 2 large bore IVs 3) antivenin is the only specific therapy a) IV administration b) local injection not recommended c) skin testing necessary prior to administration of antivenin d) dosage based upon clinical grading of envenomation - Grade 0: no antivenin necessary - Grade 1: 1-5 vials of antivenin - Grade 2: 5-15 vials of antivenin - Grade 3: 20+ vials of antivenin e) additional infusions every 2 hours until signs & symptoms have resolved 4) complications of treatment generally related to reactions to antivenin a) hypersensitivity with anaphylaxis may occur in as many as 25% of patients b) serum sickness in 50-75% of patients - fever, malaise, arthralgias, lymphadenopathy, morbilliform rash in 7-14 days 5) tetanus toxoid 6) broad spectrum antibiotics if wound infection suspected - snake oral flora includes gram-positive & gram-negative rods 7) no role for cryotherapy or ice packs 8) fasciotomy & surgical debridement a) massive necrosis or gangrene b) decompression of compartment syndrome 9) ICU admission

Related

crotalidae (pit viper) polyvalent antivenin (CroFab) Crotalidae (pit vipers) snake venom

General

reptile bite

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 1175-77
  2. Hussain T, Jan RA A Viper Bite. N Engl J Med 2015; 373:1059. September 10, 2015 PMID: 26352817 http://www.nejm.org/doi/full/10.1056/NEJMicm1410237
  3. Gerardo CJ, Vissoci JRN, Evans CS et al Does This Patient Have a Severe Snake Envenomation? The Rational Clinical Examination Systematic Review. JAMA Surg. Published online February 13, 2019. PMID: 30758508 https://jamanetwork.com/journals/jamasurgery/fullarticle/2724359
  4. Walker M World's Deadliest Neglected Disease: Snakebite Slithers Under the Radar. - Pick your poison: neurotoxic or hemotoxic. MedPage Today November 25, 2020 https://www.medpagetoday.com/infectiousdisease/publichealth/89905