Snake Bites =========== þ Thrombocyopenia - venom component found in timber rattler not covered by most antivenins causes this. þ Antivenin: - acute reactions in about 20%, serum sickeness in 70-80% - wait for an hour while it dissolves (45-60 minutes) - polyvalent horse antivenin from 4 species: + Crotalus Atrox (W Diamondback) + C adamanteaus (E diamondback) + C durissiu rettificus terrifucus + Bothrop Atrox (fer-de-lance) - active against 17 species of crotalid þ New antivenin, Fab fragments (Protherix, from Savage Labs): - made from venom of four species + Crotalus Atrox (W Diamondback) + C adamanteaus (E diamondback) + C scutalatus scuatlatus (mojave) + Agkistrodon (Ancistrodon) piscivorus (cottonmouth) - avoid if allergy to papain, latex, sheep - may have anaphylactoid reaction. but no serum sickness reported (serum sickness seems to be from the Fc portion) - doseage: 4-6 vials, then 2 vials Q6H for three doses diluted in 10 cc NS, dilute to total volume 250 cc, give over 60 minutes. þ Delayed Reactions to Antivenin - delayed up to one month - occurs in 75% of those who get 10 vials or more of Wyeth North American trivalent antivenin - Type IV (serum sickness) reaction - Signs: + vasculitis + urticaria + arthralgia and joint swelling + lymphadenopathy + peripheral neuritis - treatment: + steroids + antihistamines þ Delayed pit viper toxicity: - John Guisto wrote a case report in the Sept. '95 Annals of EM that described a 32yo male in Arizona who was bitten on a finger by a crotalid and seen shortly thereafter in the ED. The pt initially showed some swelling in the dorsum of the hand which appeared to be beginning to resolve when the patient left AMA 3 hours later. Approx 12 hours later the patient returned to the ED with severe pain and swelling, as well as a marked coagulopathy (PT > 100; PTT >200; fibrinogen <50 mg/dl). The patient was treated successfully with approx. 11 vials of antivenin. - This is the longest delayed toxicity from a snakebite that I am aware of. - this is not all that unusual (citation: Hurlbut KM, Dart RC, Spaite D, McNally JT: Reliability of clinical presentation for predicting significant pit viper envenomation. Abstract. Ann Emerg Med 17:438- 439.1988.) Unfortunately the full manuscript was never finished. Thus, John's case remains the only report in the literature to my knowledge. - In the spirit of well-meaning one-ups-manship which has bothered me greatly ever since it occurred about 10 years ago. This is a completely true and accurate rendition gathered from our records and examination of the ED record in detail. - A 7 yo boy was playing game at camp. Came out of the bushes stating that he had been bitten by brown snake. Taken to ED where a 1.5 cm laceration was noted on medial aspect of knee. For reasons that were never entirely clear, the lac was sutured after anesthesia with lido/epi and the patient was discharged. He was brought back in by his mother 4-5 hours later because of recurrent vomiting. Unfortunately he was brought by auto and apparently arrested during the trip. He was resuscitated in the ED, given antivenom, but died about 12 hours later. - This was certainly the best case of delaying manifestation of crotalid snake bite that I have seen or heard of (out of 2000-3000) cases. Yet many have told me that I must have the facts wrong. Can anyone verify similar episodes in their experience? - Rick Dart, Rocky Mountain Poison and Drug Center þ Dried Venom? I have heard of people, anectodally, being poisoned by old dried venom on things like old boots and such that gets wet and migrates thru breaks in the skin - only with the pit vipers, not the corals. þ Premedication for Antivenom Allergy? - An opinion from Australia, regarding death from intracranial hemorrhage (ICH): "Struan Sutherland reviews all know deaths from snakebite in Oz from 1981-1991 [1]: "a 62 yo woman (in hospital with multiple sclerosis)... was reaching to the floor to pick up a box of tissues when she was bitten by a Tiger Snake... This patient was unfortunate to be bitten by a tiger snake while in hospital. Such an occurence has been described before, when an elderly woman recovering from a coronary occlusion was bitten by a tiger snake which crawled into her bed in the Delegate Hospital in southern New South Wales" Three patients in this series of deaths suffered ICH at the hands of snakes (2 brown, one tiger. The first received INTRAVENOUS adrenaline 0.3 mg well before antivenom to improve his BP (it improved quite a bit from 50/ to 160/90)- antivenom was also delayed considerably while people waited for coagulation studies- one could argue that his rather serious collapse should have led them to give antivenom much earlier.. The second, an 11 yo boy also received INTRAVENOUS adrenaline as part of prophylaxis, rather than the recommended IM/SC adrenaline. Sufficent antivenom also does not appear to have been given. The third was given 3 boluses of 1 mg adrenaline IV, despite an initially normal BP, leading to a systolic above 200! This case amounts to extreme negligence. Sutherland also reviews antivenom use (86 cases of snakebite receiving antivenom) in Australia 1989-1990 in another article [2] and makes the following observations: -significant improvement, compared to a previous survey, in incidence of immediate reactions to antivenom (4.6%, down from 10%) - lowest recorded level of serum sickness (3 cases out of the 79 that were adequately followed up- none of these patients received prophylactic steroids) In contrast, overseas studies indicate: -40% incidence of severe anaphylaxis -serum sickness at rates as high as 35% Sutherland points out the routine use of oral prednisone courses (4-5 days) whenever more than one ampoule of small volume antivenom is given, or if one or more ampoule of large volume (taipan or polyvalent) antivenom is given. He also notes that recommendations at that time included routine premedication with 0.25 mg adrenaline SC (proportionally less for children), parenteral antihistamine and corticosteroids for those known to be allergic to antivenom. Also notable, is the recommedded 1:10 dilution in saline/CSL for infusion. Granted, all this proves nothing, but I think it is worth noting the marked management deficiencies in the cases suffering intracerebral haemorrhage- notably that the coagulaopathy was probably not adequately reversed, and that *in every case*, adrenaline was given intravenously. It suggests a good safety profile for routine premedication with adrenaline SC/IM and routine 4-5 day oral steriod courses following large doses of antivenom. Most important of course, is the observation that when in Australia, you are not even safe from suffering snakebite when you are admitted to a hospital... And we thought only the doctors were dangerous! REFERENCES: 1. Deaths from snakebite in Australia, 1981-1991. Med J Aust 1992; 157:740-746. 2. Antivenom use in Australia. Premedication, adverse reactions and the use of venom detection kits. Med J Aust 1992; 157: 734-739. Simon G A Brown MBBS(Tas) DA(UK) FACEM Department of Emergency Medicine Royal Hobart Hospital Hobart, Tasmania Australia þ Identification of Snakes - An opinion from Australia: "I use the venom detection kits (VDK) to try & identify the snake by either swabing the snake's mouth if available, the bite site if identifiable & the patient's urine. If the patient presents in extremis I feel you are obliged to push on with polyvalent antivenom & sort things out as time permits. I do not rely on anyones visual identification of a snake & then I will only accept opinions from individuals from only two snake houses in this state, only to confirm a snake is not poisonous after a negative VDK screen in a completely asymptomatic patient. There is no liciencing for herpetologists in the state of NSW. I am not into picking these beasties up to count scales etc. I once tried to measure a little Tiger snake which was brought in two pieces after someone sliced it's head off with a shovel. I was standing next to an RN (female), Path tech (female) doing a VDK sceen at the bite site on the patient. Having put the head on a ruler I got the body holding it at one end & then running my fingers along it's back to straighten it out & measure it. You guessed it. The spinal reflexes in the snakes body caused the body to whip up & spiral around my hand & forearm. I am not afraid to admit I out ran the RN & Path tech who were following me as I bolted out of the cubicle do an imitation of a magpie's call (a black & white Australian bird which has a distinctive call often mistaken for a four lettered word) þ Incidence of Snakebite/Antivenom Anaphylaxis in Australia - With about 100 cases of envenomation nation wide & approximately 10 episodes of life threatening anaphylaxis following antivenom administration per year a prospective radomized trial over 10 - 15 years would probably settle the issue. --Tony Nocera, NRMA CareFlight & Nepean Hospital, Sydeny, Australia þ envenomation in Australia - Sorry for leaving that out, envenomation occurs in about 10% of our snake bites. The venom glands are located posterior to the eye & it appears that the snake can control venom ejection. --Dr Tony Nocera NRMA CareFlight & Nepean Hospital, Sydeny, Australia þ Statistics - One stat I thought interesting when reading this (Rosen) is that 1 in 10 people bitten by poisonous snakes worldwide die of their envenomations (40,000 of 400,000) whereas only 1 in 500 people bitten by poisonous snakes in the U.S. die of their bites (15 of 8000). Hmmm. - James Li, MD