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Snake Envenomation, Mohave 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.
- Provide general support of airway, breathing, and circulation per advanced cardiac life support (ACLS) protocol; use oxygen, monitors, 2 large-bore intravenous lines (but minimize sticks when possible), and fluid challenge. In addition, 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. Mark and time the border of advancing tenderness and edema often enough to gauge progression. No benefit was demonstrated when a negative pressure venom extraction device (eg, The Extractor from Sawyer Products) was evaluated in recent studies. Incision across fang marks is not recommended. Mouth suction is contraindicated.
- Maintain the extremity in a neutral position of comfort.
- Lymphatic constriction bands and pressure immobilization techniques may inhibit the spread of venom, but whether they improve outcome is not clear. These techniques may actually be deleterious for pit viper envenomation if they increase local necrosis or compartment pressure. Special consideration of these techniques may be warranted for confirmed Venom A Mohave rattlesnake bites because local tissue injury is usually less. However, this application has not specifically been studied. Furthermore, it may not be possible to distinguish Venom A from Venom B snakes just by looking at the snake. The use of tourniquets is not recommended.
- First aid techniques that lack therapeutic value or are potentially more harmful than the snakebite include electric shock, alcohol, stimulants, aspirin, ice application, and various folk and herbal remedies. Cost and risk of acute adverse reactions generally preclude field use of antivenom.
- Although identification of the snake in suspected Mohave rattlesnake bites may be helpful, attempts to capture or kill the snake are not recommended because of the risk of additional injury. If the venomousness of a particular snake is uncertain, 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 2 isotonic sodium chloride solution challenges (eg, 20 mL/kg). Treat persistent shock with colloids, followed by pressors as indicated.
- Patients with Mohave rattlesnake envenomation may present with predominantly systemic and laboratory abnormalities, with only mild local and no hematological effects.
- Administer antivenom for signs of envenomation progression or imminent risk of an acute complication of envenomation (see Complications).
- Because Crotaline Fab antivenom (CroFab) appears safer than Antivenin Crotalidae Polyvalent, it is indicated even if the envenomation is minimal mild. It should be given as a preventative measure if there are any signs of envenomation at all. Do not wait for it to get worse—permanent injury could result.
- Grading envenomations is a dynamic process; administer additional antivenom as indicated by a worsening clinical course. When considering the use of antivenom, weigh the risk of adverse reaction to antivenom against the benefits of reducing venom toxicity.
- Nonenvenomation, ie, dry bite (probably occurs in <10% of rattlesnake bites)
- 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 in treating snakebitten patients with crotaline Fab antivenom (CroFab), contact the CroFab hotline at 87-SERPDRUG (877-377-3784).
Medication
Be prepared to support the patient's cardiovascular and respiratory systems after a Mohave rattlesnake or similar envenomation.
Antivenom
This agent neutralizes toxins from snakebites. Two antivenoms are available: Crotaline Fab antivenom (CroFab) and Antivenin Crotalidae Polyvalent. CroFab has been available since December 2000. CroFab is manufactured by Protherics, Inc, Nashville, Tenn, and distributed by Fougera, Melville, NY (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 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 (Crotalidae Polyvalent Immune Fab Ovine)
Appears to be more specific against rattlesnake venom and less allergenic than Antivenin (Crotalidae) Polyvalent. Remarkably effective for treatment of Venom A Mohave rattlesnake envenomation, probably because it is made using venom from Venom A Mohave rattlesnakes. 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, the vials should be further diluted into a total volume of 250 mL of NS.
The infusion should be started slowly at a rate of 50 mL/h for the first 10 min. During initial infusion, observe patient for allergic reaction. If no reaction occurs, infusion rate may be increased up to 250 mL/h until completion. Observe the patient for up to 1 h after completion to determine if initial control of envenomation has been achieved, as defined by the arrest of progression of any and all components of the envenomation syndrome (ie, no further advancement of swelling, improvement of systemic
effects, and improving coagulopathy).
Adult
4-6 vials given as above; repeat until initial control of the envenomation syndrome achieved (defined above); once initial control achieved, administer a 2-vial dose IV q6h for 18 h
Additional 2-vial doses may be administered prn on the basis of the patient's clinical course (eg, for recurrent progressive swelling or coagulopathy)
Pediatric
Administer as in adults
Studies of drug interactions have not been conducted with CroFab
Documented hypersensitivity; previous exposure and even allergy are not absolute contraindications to receiving CroFab, although risks, benefits, and alternatives must be considered before proceeding with 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 is allergic to papaya or sheep serum, although sensitivity to sheep wool not a contraindication; skin testing not required before administration; venom-induced abnormalities reported to return after successful treatment with CroFab
Local recurrence is the return of new progressive swelling after initial control, ie, the leading edge of edema begins to re-advance
Coagulopathy recurrence is the return of abnormal bleeding parameters after resolution with antivenom Indications for an additional 2 vials of CroFab are abnormal bleeding, fibrinogen <50 mcg/mL, platelet count <25 per mm3, INR >3, multicomponent coagulopathy, worsening trend in a patient with prior severe coagulopathy, high-risk behavior for trauma, or comorbid conditions that increase bleeding risk; coagulopathy can recur as late as 2 wk after 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 of warm saline by using gentle agitation. May take at least 20-90 min to dissolve. Further dilute it 1:2-4 (eg, mix 10 dissolved vials into a total dilution of 200 mL). Start the infusion at 1 mL/min for 10 min, closely monitoring for signs of allergic reaction. If no allergic reaction occurs, increase the rate to complete the infusion over 1 h. In children, run the infusion at 10 mL/kg/h. Diluting this antivenom in a greater volume of fluid and infusing it slowly may reduce the occurrence acute adverse reactions.
Routine premedication with antihistamines (H1 and H2 blockers) is recommended. Pretreatment with epinephrine (1:1000) 0.25 mL SC was shown to reduce acute adverse reactions to antivenom in one series, although the risks of epinephrine should be considered. Pretreatment with steroids is unlikely to prevent immediate reactions but may be helpful later if continued antivenom is indicated despite allergic reaction.
Adult
No envenomation: Do not administer
Mild envenomation: Do not administer unless no alternative and it is determined through informed consent of the patient that the benefit likely exceeds the risk
Moderate envenomation: 5-10 vials IV initially; administer more prn for progression of venom effects
Severe envenomation: 15-20 vials IV initially; administer more prn if lack of improvement in severity
Pediatric
Administer as in adults; higher doses for children have been recommended
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 of presence of horse serum, agents for emergency treatment of anaphylaxis should be available
Immunizations
Patients should be immunized against tetanus.
Diphtheria-tetanus toxoid (dT)
Used to induce active immunity against tetanus in selected patients. The immunizing agent of choice for most adults and children >7 y are tetanus and diphtheria toxoids. Necessary to administer booster doses to maintain tetanus immunity throughout life.
Pregnant patients should receive only tetanus toxoid, not a diphtheria antigen–containing product. In children and adults, may administer into deltoid or midlateral thigh muscles. In infants, preferred site of administration is the mid thigh laterally.
Adult
Primary immunization: 0.5 mL IM, administer 2 injections 4-8 wk apart and a third dose 6-12 mo after the second injection.
Booster dose: 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 probably not indicated routinely, although they are widely prescribed. Common etiologic bacteria suspected in snakebite wound infections include Pseudomonas aeruginosa species, Enterobacteriaceae species, Clostridium species, and Staphylococcus epidermidis. 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, 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 gm IV qd/bid; not to exceed 4 g/d
Pediatric
75 mg/kg/d divided bid; 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 penicillin allergy
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 with painful skin lesions. Use opiates with caution in unintubated patients because Mohave rattlesnake envenomation may cause respiratory difficulties.
Morphine (Astramorph, Duramorph, 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 is commonly titrated until the desired effect is obtained
Adult
2-10 mg IV/IM; titrate to relieve pain
Pediatric
0.1 mg/kg IV/IM
Phenothiazines may antagonize analgesic effects of opiate agonists; coadministration with tricyclic antidepressants, MAOIs, and other CNS depressants may potentiate adverse effects
Documented hypersensitivity; hypotension; potentially compromised airway with uncertain rapid airway control
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
Antihistamines
These agents are used to treat minor allergic reactions and anaphylaxis to antivenom or venom. Diphenhydramine may be used to pretreat patients with prior documentation of minor allergic reactions. Antihistamines are used for premedication to antivenom administration to reduce acute adverse reactions (not for direct treatment of snakebite).
Diphenhydramine (Benadryl)
Used for symptomatic relief of allergic symptoms caused by histamine released in response to allergens.
Adult
25-50 mg IV/IM; not to exceed 400 mg/d
Pediatric
5 mg/kg/d IV/IM divided q6h or 150 mg/m2/d divided qid; not to exceed 300 mg/d
Potentiates effect of CNS depressants; because of alcohol content, do not give syrup dosage form to patients taking medications that can cause disulfiramlike reactions
Documented hypersensitivity
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
More on Snake Envenomation, Mohave Rattle |
| Overview: Snake Envenomation, Mohave Rattle |
| Differential Diagnoses & Workup: Snake Envenomation, Mohave Rattle |
 Treatment & Medication: Snake Envenomation, Mohave Rattle |
| Follow-up: Snake Envenomation, Mohave Rattle |
| Multimedia: Snake Envenomation, Mohave Rattle |
| References |
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References
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Further Reading
Keywords
Mohave rattlesnake, Mojave rattlesnake bite, rattle snake envenomation, rattlesnake bite, Crotalus scutulatus, Mojave rattlesnake, snake envenomation, venom A, venom B, lethal venom, antivenom
