Venomous Snakebites: Symptoms and Treatment

1. Snakebites Kirsten Schlenker, RN Prehospital Coordinator, UPH Hospital

2. Snakebites • 45,000 total bites per year in U.S. • 8,000 bites from venomous snakes • 25% are dry bites (no venom injected) • 10 deaths

3. Anatomy of a rattlesnake bite • Rattlesnake venom has a complex protein makeup that includes a variety of enzymes and toxins. Rattlesnake venoms have primarily hemorrhagic enzyme fractions (hemotoxins), but also include neurotoxins and myotoxins to varying degrees. In certain local populations of some species, the neurotoxins may occur in much higher proportion and thus have treatment consequence. When an envenomation occurs, there may be both local and systemic effects. Local effects may include edema, hemorrhage, discoloration and pain. Systemic effects may cause changes in the respiratory, urinary, cardiovascular and urinary systems – watch for shock, renal compromise, hemolysis, coagulation factors, hypotension and more. In rare occasions, rattlesnake bites are fatal. In other cases they may result in permanent muscle or nerve damage resulting in loss of function to the affected area. If gone untreated, the likelihood and or severity of any of these consequences increases

4. Venomous Snakes • Types of U.S.venomous snakes • Pit vipers (Crotalidae) • Rattlesnakes • Copperheads • Water moccasins (cotton mouth) • Coral snakes (Elapidae)

5. Venomous Snakes • Pit vipers • Heavy bodies • Triangular-shaped heads • Vertical or elliptical pupil • Heat sensing pit on upper lip between eye and nostril • Erectile fangs • Venom primarily hemotoxic but there may be neurotoxic effects

6. Venomous Snakes • Rattlesnakes • 13 Species in Arizona • 7,000 bites/year in U.S. • 9 to 10 fatalities in U.S. • In Arizona, most deaths are from western diamondback and Mojave rattlesnakes

7. Venomous Snakes • Copperhead – not found in Arizona • Agkistrodon contortrix • Deaths VERY rare • Minimal edema and pain

8. Venomous Snakes • Watermoccasin (not found in Arizona) • Agkistrodon piscivorus • Causes an average of one death a year • Produces mild systemic symptoms, potential for severe local tissue injury and necrosis

9. Epidemiology • 25% are dry bites • 25-75% of stored venom may be discharged in a bite • Replenished in 3 to 4 weeks • Extremities are most common bite site • Most common victims: • Intoxicated males age 15-40 • Snake handlers and collectors

10. Pit Viper Envenomation • Pain, swelling at bite site • Progressive edema of bitten extremity • Bruising of bitten area • Formation of blood-filled vesicles

11. Pit Viper Envenomation • Weakness, sweating, nausea, vomiting • Tachycardia • Hypotension, shock • Prolonged clotting times • Bleeding gums • Hematemesis, melena, hematuria

12. Pit Viper Envenomation • Numbness, tingling, and neurological symptoms may develop • Presynaptic Neurotoxic effect - Produces few local effects - May cause a systemic intoxication syndrome • Decreased level of consciousness • Cranial nerve dysfunction • Respiratory paralysis

13. Grading of Pit Viper Envenomation • Dry Bite • Local abrasion or bite mark without severe pain or swelling • Normal vital signs • Normal coagulation studies • Normal platelet count

14. Grading of Pit Viper Envenomation • Mild Envenomation • Local pain and swelling • Normal vital signs • Normal to mildly abnormal coagulation studies • Platelet count >100,000

15. Grading of Pit Viper Envenomation • Moderate Envenomation • Local pain and moderate swelling • Normal vital signs • Abnormal coagulation studies (doubling of pT and pTT) • Thrombocytopenia (platelets <100,000)

16. Grading of Pit Viper Envenomation • Severe Envenomation • Initial presentation consistent with shock • Altered mental status with or without normal vital signs and/or poor peripheral perfusion • Abnormal coagulation studies (immeasurable pT and pTT) • Thrombocytopenia (platelets <20,000)

17. Venomous Snakes • Coral snakes • Two species in the U.S. • Arizona coral snake • Non-aggressive • No recorded human deaths • Eastern coral snake • Several bites reported annually (Florida to Texas) • About one death every 5 years

18. VenomousSnakes • Arizona Coral snake • Thin-bodied, small rounded snout, brightly colored ringed pattern, small non-erectile fangs • Venom usually delivered by chewing • Venom primarily postsynaptic neurotoxic • Little to no hemotoxic effects • Arizona coral snake is docile and rarely bites • No antivenin is made for this species

19. Coral Snake Envenomation • Little to no pain • Little to no swelling • Paresthesias around bitten area • Muscular incoordination, weakness

20. Coral Snake Envenomation(from eastern U.S. species) • Increased salivation • Difficulty swallowing, talking • Visual disturbances • Respiratory distress, failure • Shock, cardiovascular collapse Most deaths occur from respiratory arrest within 36 hours

21. Snakebite Management • Calm and reassure the patient • Secure and maintain airway • Prepare for immediate transport (do not delay treatment for any first aid/treatment measure or wait for signs of envenomation to occur) • Obtain vital signs including O2 saturation • Oxygen to keep saturation > 90% (method as best tolerated by patient) • Remove ALL watches, rings, and jewelry (not just from affected limb) • If bite on extremity, immobilize affected extremity at or below the level of the heart (make sure any immobilization device and practice does not result in becoming a tourniquet over time due to swelling) • Mark the proximal edge of any discoloration or swelling in ink and write the time on the line (if signs increase during transport, make new marks with the times)

22. Snakebite Management • Do NOT attempt to locate and bring the venomous snake to the hospital. If you find it, you will probably make a bad scene worse: it has already bitten one person! There is no medical reason to bring the snake in. All local species use the same antivenin.

23. Do NOT use ice or cold packs. It does not slow the enzyme activity. It slows the immune-response.

24. DO NOT use tourniquets or restricting bands. All you do is localize all those digestive enzymes.

25. DO NOT lance, or use cut and suck methods. Snakebite is an IM injection. The venom isn’t going to be sucked out. Cutting increases tissue damage to an area already infiltrated with digestive enzymes.

26. Here is a finger bite progressing well through proper treatment (note black ink marks where increases in edema were recorded)

28. Special thanks to the following for providing information and/or photographs. • Hugh McCrystal • D. Frank Retes • Drexel Heights Fire District • The Arizona-Sonora Desert Museum • The New York Zoological Society