pick your poison

Poisons, toxins, and venoms are obviously dangerous chemicals, but did you know that most of these nasty things act by interfering with enzymes?

Choose a particular poison, toxin, or venom and carry out research to learn about how it acts. Be sure to find out the following and share your research in a blog post:Poisons, toxins, and venoms are obviously dangerous chemicals, but did you know that most of these nasty things act by interfering with enzymes?

Choose a particular poison, toxin, or venom and carry out research to learn about how it acts. Be sure to find out the following and share your research in a blog post:

1-Where is this substance found or produced?-the substance if found in rattlesnakes

2-What kind of substance is it?-it is a poison that contains hemotoxic elements and nerotoxic elements

3-What are the specific molecules that it acts upon?-

4-What are the symptoms of exposure to this substance?-

• One or two puncture marks
• Pain, tingling or burning at the area of the bite
• Swelling at the area of the bite
• Bruising and discoloration at the site of the bite
• Numbness
• Nausea, weakness and lightheadedness.
• Difficulty breathing

5-How is exposure to this substance treated?The mainstay of treatment is the administration of intravenous fluids with isotonic crystalloid to maintain fluid homeostasis. Evidence of progressive swelling or laboratory evidence of coagulopathy (fibrinogen generally less than 100 mg/dL) or thrombocytopenia (platelets less than 90,000/mm3) should prompt antivenom therapy. In animal models and clinical experience, both the Wyeth Antivenin and CroFab are efficacious in the treatment of envenomations from pit vipers. However, CroFab is currently the preferred antivenom due to its low risk of side effects and because of the limited availability of the Wyeth product. The amount of antivenom needed to treat a particular pit viper bite depends on the severity of the envenomation and not on the patient’s weight. Therefore, children and adults generally receive the same amount of antivenom; however the practitioner must carefully consider fluid volumes and rates in small children.

Patients requiring antivenom therapy secondary to the clinical or laboratory findings of progressive swelling, hypotension, coagulopathy or thrombocytopenia should be admitted to a monitored setting (ED or ICU). Opioids such as fentanyl or morphine are commonly administered for pain control. Blood products such as fresh frozen plasma or platelets are generally ineffective in reversing the venom-induced coagulopathy, hypofibrinogenemia, or thrombocytopenia because they are rapidly consumed by circulating venom. In the absence of active bleeding, administration of blood products is not recommended.

The initial dose of CroFab is 4 - 6 vials reconstituted into 250 mL of normal saline. The infusion should be started slowly, and gradually titrated up to 250 mL/hr. Additional CroFab in increments of 4 - 6 vials may be required to establish control, defined by the cessation of progression of signs and symptoms (range of 4 - 48 or more vials with an average of 12). Recently, cases of recurrent coagulopathy, thrombocytopenia, and swelling in rattlesnake bite victims 36-72 hours after the initial control of signs and symptoms have been reported with the use of CroFab. These effects appear to be related to the relatively short half-life of the Fab fragments in the body as they are cleared by the kidneys. Patients should be observed for at least 24 - 48 hours after control of the envenomation, to monitor for recurrence of symptoms that may necessitate further antivenom therapy. Patients can then be followed up with outpatient lab testing for coagulopathy and platelet count in 48 -72 hours to assess for recurrence. If recurrence is documented, repeat doses of CroFab may be required and administered in 2 - 4 vial increments. In case where it is unclear whether follow up is necessary, a poison information specialist or medical toxicologist can be consulted through the California Poison Control System.

The initial dose of Wyeth Antivenin is 10 - 20 vials reconstituted in 500 mL of normal saline. The infusion should be started slowly and titrated up to 500 mL/hr. Additional vials may be required to establish control and have ranged up to 60 vials with an average of 15 - 20. Patients should again be observed for at least 24 – 48 hours after control of the envenomation.

Anaphylactoid reactions from the antivenom may manifest as pruritus, rash, hypotension, and/or wheezing. If the patient develops any of these reactions, the infusion should be stopped, followed by the administration of antihistamines, epinephrine (4 ug/min or 0.05 ug/kg/min), or both, as necessary. Steroids such as prednisone can also be administered for these reactions. Once the symptoms have abated, the antivenom may be restarted at a slower rate and run to completion.

Animal studies have shown that administering antivenom can increase perfusion into a bitten muscular compartment. Therefore, aggressive antivenom administration should precede any consideration of surgical intervention, such as fasciotomy, unless there is a delay in the presentation of the victim after the snakebite. Patients with minimal clinical signs or symptoms not initially requiring antivenom should be observed for 6 - 8 hours, because the clinical effects may be delayed by several hours especially with bites to the lower extremity.