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Snake Envenomation, Rattle: Treatment & Medication
Updated: Jul 24, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Treatment
Prehospital Care
Do nothing to injure the patient or impede travel to the ED.
- Give general support of airway, breathing and circulation per advanced cardiac life support (ACLS) protocol with oxygen, monitors, 2 large bore intravenous lines, and fluid challenge. Minimize activity (if possible), remove jewelry or tight-fitting clothes in anticipation of swelling, and transport the patient to the ED as quickly and as safely as possible. Use a pen to mark and time the border of advancing edema often enough to gauge progression.
- In recent studies, no benefit was demonstrated when a negative pressure venom extraction device (eg, The Extractor from Sawyer Products) was evaluated; additional injury can result. Incision across fang marks is not recommended. Mouth suction is contraindicated.
A recent study suggests that the Extractor (Sawyer Products) does not reduce swelling after rattlesnake envenomation and may be associated with skin necrosis beneath the suction cup. Photo by Sean Bush, MD.
- Lymphatic constriction bands and pressure immobilization techniques may inhibit the spread of venom, but whether they improve outcome is not clear. Limiting venom spread actually may be deleterious for pit viper envenomation if it increases local necrosis or compartment pressure. Tourniquets are not recommended.
- Maintain the extremity in a neutral position.
- First aid techniques that lack therapeutic value or are potentially more harmful than the snakebite include electric shock, alcohol, stimulants, aspirin, placing ice on the wound, and various folk and herbal remedies. Cost and risk of acute adverse reactions generally preclude field use of antivenom.
- Attempts to capture or kill the snake cannot be recommended because of the risk of additional injury. If uncertainty exists about whether a particular snake is venomous, consider taking photographs of the snake from a safe distance of at least 6 feet away using a digital or Polaroid camera.
Emergency Department Care
Adequate hydration with intravenous fluids is indicated. Patients with hypotension should be resuscitated first with two isotonic sodium chloride solution challenges (eg, 20 mL/kg). Treat persistent shock with colloids, followed by pressors as indicated.
- Administer antivenom for signs of envenomation progression or imminent risk of an acute complication of envenomation (see Complications). Because CroFab appears safer than Antivenin Crotalidae Polyvalent, it is indicated even if the envenomation is minimal or mild. It should be given as a preventative measure if any signs of envenomation exist. Do not wait for the envenomation to get worse—permanent injury could result.
- It is emphasized that grading envenomations is a dynamic process and additional antivenom should be given as indicated by a worsening clinical course. When considering the use of antivenom, the risk of adverse reaction to antivenom must be weighed against the benefits of reducing venom toxicity. Alternatives (eg, a different type of antivenom, if available) should be considered as well.
- Nonenvenomation, ie, dry bite (probably occurs in <10% of rattlesnake bites, although estimates as high as 50% exist)
- Local effects - Puncture wounds only
- Systemic effects - None
- Coagulation abnormalities - No laboratory evidence of coagulation abnormalities and no clinical evidence of abnormal bleeding or clotting
- Minimal or mild envenomation
- Local effects - Swelling, pain, tenderness, and/or ecchymosis confined to the immediate bite area
- Systemic effects - None
- Coagulation abnormalities - No laboratory evidence of coagulation abnormalities and no clinical evidence of abnormal bleeding or clotting
- Moderate envenomation
- Local effects - Swelling, pain, tenderness, and/or ecchymosis extending beyond the immediate bite area but involving less than the entire part
- Systemic effects - Present but not life threatening; may include nausea, vomiting, oral paresthesias or unusual tastes, fasciculations (myokymia), mild hypotension (systolic blood pressure <90 mm Hg), mild tachycardia (heart rate <150 bpm), and tachypnea
- Coagulation abnormalities - Laboratory evidence of coagulation abnormalities may be present, but no clinical evidence of abnormal bleeding or clotting exists; rattlesnake venom-induced coagulopathies commonly include thrombocytopenia, decreased fibrinogen, and/or elevated PT
- Severe envenomation
- Local effects - Swelling, pain, tenderness, and/or ecchymosis extending beyond the entire extremity or threatening the airway
- Systemic effects - May include severe hypotension or shock, severe tachycardia or tachypnea, respiratory insufficiency, and/or severe altered mental status
- Coagulation abnormalities - Markedly abnormal with serious bleeding or severe threat of bleeding
Consultations
- The American Association of Poison Control Centers may assist in the management of envenomations.
- For assistance regarding use of CroFab for a patient bitten by a snake, contact the CroFab hotline at 1-87-SERPDRUG (1-877-377-3784).
- Consider consulting a surgeon (eg, general, orthopedic, hand) if compartment syndrome is suspected.
Medication
The only proven therapy for snakebites is antivenom. The physician also must be prepared to support the victim's cardiovascular and respiratory systems.
Antivenom
This agent neutralizes toxins from snakebites. Two antivenoms are available: CroFab and Antivenin Crotalidae Polyvalent. CroFab has been available since December 2000. CroFab is manufactured by Protherics Inc, Nashville, Tennessee and distributed by Fougera, Melville, New York (800-231-0206). Antivenin Crotalidae Polyvalent, manufactured by Wyeth-Ayerst, is still available on the shelves of many hospital pharmacies but is no longer being produced. Whether the production of Antivenin will resume is unknown. Meanwhile, another antivenom (Antivipmyn, manufactured by Instituto Bioclon S.A. de C.V.) has been FDA approved for experimental use and is currently undergoing phase III clinical trials.
CroFab
CroFab (Crotalidae Polyvalent Immune Fab Ovine) appears to be more specific against rattlesnake venom and less allergenic than Antivenin Crotalidae Polyvalent. The usual starting dose is 4-6 vials. Reconstitute each vial with 10 mL of sterile water for USP injection and mix by continuous swirling. Once CroFab goes into solution, dilute the vials further into total volume of 250 mL of NS. Start infusion slowly at rate of 50 mL/h for first 10 min. During initial infusion, observe patient for allergic reaction. If no reaction occurs, may increase infusion rate to 250 mL/h until completion. Observe patient for up to 1 h after completion to determine if initial control of envenomation achieved, as defined by arrest of progression of any and all components of envenomation syndrome (ie, no further advancement of swelling, improvement of systemic effects, and improving coagulopathy).
Adult
Initial: 4-6 vials given as above; repeat until initial control of envenomation syndrome achieved (as defined above)
Once initial control achieved, administer 2-vial dose IV q6h for 18 h, although this may not completely prevent local recurrence of progressive venom effects
May administer additional 2-vial doses prn based on patient's clinical course (eg, for recurrent progressive swelling or coagulopathy)
Pediatric
Administer as in adult; no change in dose for pediatrics (may need to adjust volume for very small infants and children)
Not established
Documented hypersensitivity; previous exposure and even allergy are not absolute contraindications to receiving CroFab; consider risks, benefits, and alternatives before administering antivenom
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Patients with dust mite allergies and some latex allergies may be sensitive (specifically ask if patient allergic to papaya or sheep serum; sensitivity to sheep wool not a contraindication); skin testing not required before administration
Venom-induced abnormalities have reported to return after successful treatment with CroFab; local recurrence is return of new progressive swelling after initial control, ie, the leading edge of tenderness and edema begins to advance again; coagulopathy recurrence is return of abnormal bleeding parameters after resolution with antivenom; indications for additional 2 vials of CroFab are abnormal bleeding, fibrinogen <50 mcg/mL, platelet count <25/mm3, INR >3, multicomponent coagulopathy, worsening trend in patient with prior severe coagulopathy, high-risk behavior for trauma, or comorbid conditions that increase bleeding risk; coagulopathy can recur 2 wk or more after treatment of envenomation
Contains mercury, which, in high doses, may be associated with neurologic and renal toxicities, particularly in developing fetuses and very young patients
Antivenin (Crotalidae) Polyvalent
Manufactured by Wyeth-Ayerst. To mix antivenom, dissolve in 10 mL warm saline by gentle agitation. May take anywhere from 20-90 min or more to dissolve. Further dilute it 1:2 or 1:4 or more (eg, mix 10 dissolved vials into a total dilution of 200 cm3). Start infusion at 1 mL/min for 10 min, closely monitoring for signs of allergic reaction. If no allergic reaction occurs, increase rate to complete infusion over 1 h. For children, run infusion at 10 mL/kg/h. Diluting antivenom in greater volume of fluid and infusing slowly may reduce occurrence acute adverse reactions.
Routine premedication with antihistamines (H1 and H2 blockers) recommended. Pretreatment with epinephrine (1:1000) 0.25 mL SC was shown to reduce acute adverse reactions to antivenom in one series, although risks of epinephrine should be considered. Pretreatment with steroids is unlikely to prevent immediate reactions but may be helpful later if continued antivenom indicated despite allergic reaction.
Adult
No envenomation: Do not use
Mild envenomation: Do not use unless no alternative and determined through informed consent of patient that benefit likely exceeds risk
Moderate envenomation: Start with 5-10 vials IV and administer more prn for progression of venom effects
Severe envenomation: Start with 15-20 vials IV and administer more prn for progression or lack of improvement in severity
Pediatric
Administer as in adults
None reported
Documented hypersensitivity; however, may administer in severe envenomation, despite hypersensitivity, although risks, benefits, and alternatives should be considered
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Because anaphylaxis may occur whenever Antivenin (Crotalidae) Polyvalent is given, appropriate therapeutic agents and resuscitative equipment should be ready for immediate use
Antihistamines
These agents are used for treatment of acute allergic reactions to antivenom or venom (not for treatment of envenomation).
Diphenhydramine (Benadryl)
Used for the symptomatic relief of allergic symptoms caused by histamine released in response to allergens
Adult
25-50 mg IV/IM
Pediatric
5 mg/kg/d IV/IM or 150 mg/m2/d IV/IM divided qid
Potentiates effect of CNS depressants; due to alcohol content, do not give syrup dosage form to patient taking medications that can cause disulfiramlike reactions
Documented hypersensitivity; MAOIs
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
May exacerbate angle-closure glaucoma, hyperthyroidism, peptic ulcer, and urinary tract obstruction
Immunizations
Patients should be immunized against tetanus.
Diphtheria-tetanus toxoid (dT)
Used to induce active immunity against tetanus in selected patients. Tetanus and diphtheria toxoids are the immunizing agents of choice for most adults and children >7 y. Booster doses are necessary to maintain tetanus immunity throughout life because tetanus spores are ubiquitous.
Pregnant patients should receive only tetanus toxoid, not diphtheria antigen–containing product. In children and adults, may administer into deltoid or midlateral thigh muscles. In infants, preferred site of administration is mid-thigh laterally.
Adult
Primary immunization: Administer 0.5 mL IM, administer 2 injections 4-8 wk apart and third dose 6-12 mo after second injection
Booster dose: Administer 0.5 mL IM q10y
Pediatric
Administer as in adults
Patients receiving immunosuppressants, including corticosteroids or radiation therapy, may remain susceptible despite immunization because of poor immune response; cimetidine may enhance or augment delayed-hypersensitivity responses to skin-test antigens; avoid concurrent use of medication with systemic chloramphenicol because it may impair amnestic response to tetanus toxoid; concurrent use of tetanus immune globulin may delay development of active immunity by several days (nevertheless, interaction is clinically insignificant and does not preclude its concurrent use)
Documented hypersensitivity; a history of any type of neurologic symptoms or signs following administration of this product; FDA recommends that elective tetanus immunization be deferred during any outbreak of poliomyelitis because tetanus toxoid injections are an important cause of provocative poliomyelitis
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Do not use to treat actual tetanus infections or for immediate prophylaxis of unimmunized individuals (use tetanus antitoxin instead, preferably human tetanus immune globulin); diminished antibody response to active immunization may be observed in patients receiving immunosuppressive therapy; better to defer primary diphtheria immunization until immunosuppressive therapy discontinued; routine immunization of symptomatic and asymptomatic HIV-infected persons is recommended
Antibiotics
Prophylactic antibiotics are not routinely indicated. However, wound infections should be treated with antibiotics. Common etiologic bacteria in wound infections include Pseudomonas aeruginosa, Staphylococcus epidermidis, Enterobacteriaceae species, and Clostridium species. For infected wounds, empiric therapy may include ciprofloxacin (contraindicated in pediatric patients and pregnant women) as a single agent or a combination of ceftriaxone plus amoxicillin-clavulanate, pending wound culture and sensitivity results. Retained foreign bodies (eg, a fang, other tooth) are a common cause of wound infection.
Ceftriaxone (Rocephin)
Third-generation cephalosporin with broad-spectrum gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against resistant organisms. Arrests bacterial growth by binding to one or more penicillin-binding proteins.
Adult
1-2 g IV qd or divided bid; not to exceed 4 g/d
Pediatric
>7 days: 25-50 mg/kg/d IV/IM; not to exceed 125 mg/d
Infants and children: 50-75 mg/kg/d IV/IM divided q12h; not to exceed 2 g/d
Probenecid may increase levels; coadministration with ethacrynic acid, furosemide, and aminoglycosides may increase nephrotoxicity
Documented hypersensitivity
Pregnancy
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Precautions
Adjust dose in renal impairment; caution in breastfeeding women and allergy to penicillin
Analgesics
Pain control is essential to quality patient care. It ensures patient comfort and promotes pulmonary toilet. Most analgesics have sedating properties, which are beneficial for patients who have sustained painful snakebites. Opioid analgesics are recommended for pain control as needed. NSAIDs may contribute to coagulopathies.
Morphine sulfate (Astramorph, Duramorph, and MS Contin)
DOC for narcotic analgesia because of its reliable and predictable effects, safety profile, and ease of reversibility with naloxone.
Morphine sulfate administered IV may be dosed in a number of ways and commonly is titrated until the desired effect is obtained.
Adult
2-10 mg IV/IM; titrate to relief of pain
Pediatric
0.1 mg/kg IV/IM
Phenothiazines may antagonize analgesic effects of opiate agonists; tricyclic antidepressants, MAOIs, and other CNS depressants may potentiate adverse effects
Documented hypersensitivity; hypotension; potentially compromised airway where establishing rapid airway control would be difficult
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Avoid in hypotension, respiratory depression, nausea, emesis, constipation, and urinary retention; caution in atrial flutter and other supraventricular tachycardias; has vagolytic action and may increase ventricular response rate
Hematologic Agents
Consider transfusion if antivenom does not correct coagulopathy or if imminent risk of serious bleeding. Transfusion is generally recommended for life-threatening bleeding (rare), platelets <20,000 mm3, or hemoglobin <7 g/dL. Transfusion should be utilized after antivenom as a temporizing or adjuvant measure because antivenom may correct coagulopathies more definitively (although this is an area with particularly contradictory literature). Coagulopathy often recurs and may persist for 2 weeks or more after envenomation.
Platelets, fresh frozen plasma (FFP), and packed RBCs
Used preferentially to whole blood because they limit volume, immune, and storage complications. PRBCs have 80% less plasma, are less immunogenic, and can be stored about 40 d (versus 35 d for whole blood). PRBCs are obtained after centrifugation of whole blood. Leukocyte-poor PRBCs are used in patients who are transplant candidates/recipients or in those with prior febrile transfusion reactions. Washed or frozen PRBCs are used in individuals with hypersensitivity transfusion reactions. Blood can be administered over 3-4 hours, premedicating with acetaminophen and diphenhydramine to prevent febrile transfusion reactions.
Adult
1 unit of PRBCs should raise the hemoglobin by 1 g/dL or hematocrit by 3%
Pediatric
10 mL/kg IV bolus, whole blood is preferred
5 mL/kg IV bolus if PRBCs used
None reported
Refusal of blood product by a competent adult or a legal guardian of a minor can be very difficult; immediate consultations with hospital ethical and legal staff strongly recommended
Pregnancy
A - Fetal risk not revealed in controlled studies in humans
Precautions
Viral contamination and infection are possible but unlikely because of prescreening; ineffective in patients with factor IX inhibitors; may induce an anamnestic response
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References
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Further Reading
Keywords
rattlesnake, rattlesnake bite, rattlesnake venom, rattlesnake envenomation, Crotalus species, Sistrurus species, rattle snake envenomation, pit vipers
