Quote:
Originally posted by Team4medic
Rattle Snakes, Cotton Mouths are anther story. They do cause Severe pain and swelling sometimes needing an escharotmy.Systemic tocxicity is common and antivenin is usually needed
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There are specific indications for the use of antivenom because of the risk ofa hypersensitivity reaction or anaphylaxis. Therefore, antivenom is indicated only if serious manifestations of envenomation are evident (coma, neurotoxicity, hypotension, shock, bleeding, DIC, acute renal failure, rhabdomyolysis and ECG changes for example). In the absence of the above, extensive swelling or increasing bruising or edema within a very short time (30-60 minutes) can also be an indication.
This is all taken off a site here online that I thought gave useful information
Dose
Despite widespread use of antivenom, there are virtually no clinical trials to determine the ideal dose. Conventionally 50 ml (5 vials) is infused for mild manifestations like local swelling with or without lymphadenopathy, purpura or echymosis. Moderate envenomation defined by presence of coagulation defects or bradycardia or mild systemic manifestations, merits the use of 100 ml (10 vials). 150 ml (15 vials) is infused in severe cases, which includes rapid progression of systemic features, DIC, encephalopathy and paralysis.
Administration
The freeze dried powder is reconstituted with 10 ml of injection water or saline or dextrose . A test dose is administered on one forearm with 0.02 ml of 1:10 solution intradermally. Similar volume of saline in the other forearm serves as control. Appearance of erythema or wheal greater than 10 mm within 30 min is taken as a positive test. In this event, desensitization is advised starting with 0.01 ml of 1:100 solution and increasing concentration gradually at intervals of 15 minutes till 1.0 ml s.c can be given by 2 hours. Infusion is started at 20 ml/kg per hour initially and slowed down later.
Antivenom is administered by the intravenous route and never into fingers or toes. Some authors recommend that 1/3 to 1/2 the dose be given at the local site to neutralize venom there. However, animal experiments have established that absorption begins almost instantly from bite sites. Besides this, systemic administration of antivenom has been shown to be effective at the local site as well. Therefore most experts do not advise local injection of antivenin.
Efficacy of intramuscular administration of antivenom followed by standard hospital management has also been evaluated and a definite reduction in the number of patients with systemic envenomation, complications and mortality from Russell's viper toxemia has been noted. This route of administration is likely to have value in a field setting prior to transfer to better facilities.
Timing
There is no consensus as to the outer limit of time of administration of antivenom. Best effects are observed within four hours of bite. It has been noted to be effective in symptomatic patients even when administered up to 48 hours after bite. Reports suggest that antivenom is efficacious even 6-7 days after the bite. In experimental settings, rats injected with antivenom even 3 weeks after the bite showed good response. It is obvious that when indicated, antivenom must be administered as early as possible and data showing efficacy with delayed administration is based on use in settings where patients present late.
Response
Response to infusion of antivenom is often dramatic with comatose patients sitting up and talking coherently within minutes of administration. Normalization of blood pressure is another early response. Within 15 to 30 minutes, bleeding stops though coagulation disturbances may take up to 6 hours to normalize. Neurotoxicity improves from the first 30 minutes but may require 24 to 48 hours for full recovery
If response to antivenom is not satisfactory use of additional doses is advocated. However, no studies establishing an upper limit are available and infusion may be discontinued when satisfactory clinical improvement occurs even if recommended dose has not been completed. In experimental settings, normalization of clotting time has been taken as end-point for therapy.
Reactions
Hypersensitivity reactions including the full range of anaphylactic reactions may occur in 3-4% of cases, usually within 10 to 180 minutes after starting infusion. These usually respond to conventional management including adrenaline, anti-histamines and corticosteroids.
Linear Mode
