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Snakebite Treatment & Management

  • Author: Brian J Daley, MD, MBA, FACS, FCCP, CNSC; Chief Editor: Joe Alcock, MD, MS  more...
 
Updated: Apr 08, 2016
 

Severity of Envenomation

Treatment is based on the severity of envenomation; it is divided into field care and hospital management. See Tables 1 and 2 below.

Table 1. Snakebite Severity Scale (Open Table in a new window)

Criteria Signs/Symptoms Score
Pulmonary    
  No symptom/sign 0
  Dyspnea, minimal chest tightness, mild or vague discomfort, or respirations of 20-25 breaths/min 1
  Moderate respiratory distress (tachypnea, 26-40 breaths/min, accessory muscle use) 2
  Cyanosis, air hunger, extreme tachypnea, or respiratory insufficiency/failure 3
Cardiovascular    
  No symptom/sign 0
  Tachycardia (100-125 beats/min), palpitations, generalized weakness, benign dysrhythmia, or hypertension 1
  Tachycardia (126-175 beats/min) or hypotension with systolic blood pressure < 100 mm Hg 2
  Extreme tachycardia (>175 beats/min) or hypotension with systolic blood pressure < 100 mm Hg, malignant dysrhythmia, or cardiac arrest 3
Local wound No symptom/sign (swelling or erythema < 2.5 cm of fang mark) 0
  Pain, swelling, or ecchymosis within 5-7.5 cm of bite site 1
  Pain, swelling, or ecchymosis involving less than half of the extremity (7.5 cm from site) 2
  Pain, swelling, or ecchymosis extending beyond affected extremity (>100 cm from site) 3
Gastrointestinal    
  No symptom/sign 0
  Pain, tenesmus, or nausea 1
  Vomiting or diarrhea 2
  Repeated vomiting or diarrhea, hematemesis, hematochezia 3
Hematological    
  No symptom/sign 0
  Coagulation parameters slightly abnormal (PTa < 20 seconds, PTTb < 50 seconds, platelets 100,000-150,000/µL, fibrinogen 100-150 mcg/mL) 1
  Coagulation parameters abnormal (PT < 20-50 seconds, PTT < 50-75 seconds, platelets 50,000-100,000/µL, fibrinogen 50-100 mcg/mL) 2
  Coagulation parameters abnormal (PT < 50-100 seconds, PTT < 75-100 seconds, platelets 20,000-50,000/µL, fibrinogen < 50 mcg/mL) 3
  Coagulation parameters markedly abnormal, with serious bleeding or threat of spontaneous bleeding (PT or PTT unmeasurable, platelets < 20,000/µL, fibrinogen undetectable), with severe abnormalities in other laboratory values, including venous clotting time 4
Central nervous system    
  No symptom/sign 0
  Minimal apprehension, headache, weakness, dizziness, chills, or paresthesia 1
  Moderate apprehension, headache, weakness, dizziness, chills, paresthesia, confusion, or fasciculation in area of bite site, ptosis, and dysphagia 2
  Severe confusion, lethargy, seizure, coma, psychosis, or generalized fasciculation 3
  Extremely severe envenomation leading to death 4
a PT = Prothrombin time.



b PTT = Partial thromboplastin time.



Patients are eligible for therapy with CroFab if they have moderate or severe envenomation as described or any degree of envenomation with progression of the envenomation syndrome. Note: As the antivenom dose reflects venom size, not patient size, the US Food and Drug Administration recommends the same initial and subsequent doses for pediatric patients. Data show efficacy and safety for patients as young as 14 months.

Table 2. Severity of Envenomation (Open Table in a new window)

Type of Signs/Symptoms Minimal Moderate Severe
Local Swelling, erythema, or ecchymosis confined to bite site Progression of swelling, erythema, or ecchymosis beyond bite site Rapid swelling, erythema, or ecchymosis involving the entire body part
Systemic No systemic signs or symptoms Non–life-threatening signs or symptoms (nausea/vomiting, mild hypotension, perioral paresthesias, myokymia) Markedly severe signs or symptoms (hypotension [systolic < 80 mm Hg], altered sensorium, tachycardia, tachypnea, and respiratory distress)
Coagulation No coagulation abnormalities or other laboratory abnormalities Mild abnormal coagulation profile without significant bleeding Abnormal coagulation profile with bleeding (INRa, aPTTb, fibrinogen, platelet count < 20,000/µL
Snakebite Severity Score 0-3 4-7 8-20
a INR = International normalized ratio.



b aPTT = Activated partial thromboplastin time.



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General Management Principles

Important considerations when encountering patients with snakebites are described.

Patients with acute presentations still require starting with a rapid assessment of the patient's airway. Obstruction or respiratory failure requires the acquisition of a definitive airway, which might require rapid sequence intubation (RSI). Breathing and circulation should also be assessed in the initial state once an airway has been established.

Remove the patient from the snake's territory as soon as stabilization has occurred in order to avoid further harm.

Remove any jewelry or constricting clothing from the patient's affected area. If clothing is not causing any compression or constriction, it can be left alone until the patient is transferred to a hospital for further care.

In the immediate/acute setting, withhold all alcohol and any drugs that may confound clinical assessment or interfere with treatment.

Do not manipulate the wound site. It is not recommended to incise the site or perform oral suction.[10]

Further inpatient care

Admission to the hospital is routine for most envenomation cases. A "dry bite" without envenomation can occur in a significant percentage of cases (50% in coral snake, 25% from pit viper). For dry pit viper bites, observe in the emergency department for 8-10 hours; however, often this is not feasible. Patients with severe envenomation need specialized care in the ICU to administer blood products, provide invasive monitoring, and ensure airway protection. Observe coral snakebites for a minimum of 24 hours.

Perform serial evaluations for further grading and to rule out compartment syndrome. Depending on clinical scenarios, measure compartment pressures every 30-120 minutes. Fasciotomy can be considered for pressures greater than 30-40 mm Hg. However, fasciotomy has not been shown to improve outcomes, even when compartment pressures are elevated, and is not routinely indicated for crotalid snake envenomation.[11, 12]

Depending on the clinical severity of the bite, further blood work may be needed, especially clotting studies, platelet count, and fibrinogen level. Late coagulopathy has been reported after using FABAV. F(ab’)2 immunoglobulin derivatives under development have a longer half life than CroFab and have been shown to decrease late coagulopathy after antivenin treatment.[12, 13]

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Prehospital Care

As with all medical emergencies, the goal is to support the patient until arrival at the emergency department. The dictum " primum no nocere " (first, do no harm) has significant meaning here because many poorly substantiated treatments may cause more harm than good, including making an incision over the bite, mouth suctioning, tourniquet use, ice packs, or electric shock.

Appropriate field care should adhere to the basic tenants of emergency life support.

Reassure the patient during the implementation of ABCs.

Monitor vital signs and establish at least one large-bore IV and initiate crystalloid infusion. Administer oxygen therapy. Keep a close watch on the airway at all times in case intubation becomes necessary.

Restrict activity and immobilize the affected area (commonly an extremity); keep walking to a minimum.

Negative-pressure suctioning devices offer some benefit if used within several minutes of envenomation. Again, do not make an incision in the field.

Immediately transfer to definitive care.

Do not give antivenin in the field.

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Emergency Department Care

Physicians who have little experience treating snakebites frequently care for such patients.

Regional centers often have more experience in the care of snakebite victims. Surgical evaluation for an envenomation victim is paramount.

Definitive treatment includes reviewing the ABCs and evaluating the patient for signs of shock (eg, tachypnea, tachycardia, dry pale skin, mental status changes, hypotension).

For victims of pit viper (crotaline snake) bites, evenomation grading determines the need for antivenin. Grades are defined as mild, moderate, or severe. Mild envenomation is characterized by local pain, edema, no signs of systemic toxicity, and normal laboratory values. Moderate envenomation is characterized by severe local pain; edema larger than 12 inches surrounding the wound; and systemic toxicity including nausea, vomiting, and alterations in laboratory values (eg, decreased hematocrit or platelet count). Severe envenomation is characterized by generalized petechiae, ecchymosis, blood-tinged sputum, hypotension, hypoperfusion, renal dysfunction, changes in prothrombin time and activated partial thromboplastin time, and other abnormal test results defining consumptive coagulopathy. See Tables 1 and 2 above.

Grading envenomations is a dynamic process. Over several hours, an initially mild syndrome may progress to a moderate or even severe reaction.

For pit viper envenomations, horse-serum antivenin has been available since 1956; a purer antivenin with improved properties was released in 2000 (see Medication). With the reduced side-effect profile of antigen-binding fragment antivenom (FabAV) and the improvement in tissue injury with antivenin administration, the threshold for dosing is lower. One study from the southwest United States demonstrated a reduction in rate of fasciotomy after more liberal FabAV dosing.[14] In a randomized study of scheduled versus as-needed FabAV dosing in patients whose symptoms were worsening, the Rocky Mountain Poison and Drug Center demonstrated a reduction in pain and other venom effects but noted a 20% acute and 23% delayed drug reaction.[15]

Although copperhead bites are generally self-limiting, morbidity was reduced in moderate envenomation 4 hours after 4 vials of FabAV in 88% of cases. The cases that failed to respond were not changed by further FabAV doses.[16]

FabAV is generally considered safe for children, as many of the studies did not discriminate in age. One large study from Mexico demonstrated no immediate or late allergic reactions to FabAV when administered according to grade of envenomation.[6]

Although FabAV helps control local tissue effects and hemotoxicity, aggressive antivenom therapy does not usually ameliorate neurotoxic effects such as myokymia (spontaneous, fine fascicular contractions of muscle without muscular atrophy or weakness) and major muscle fasciculations. The physician must maintain continuous monitoring of those patients with myokymia especially of the shoulders, chest, and diaphragm for the development of respiratory failure and need for mechanical ventilation.[17, 18]

Coral snakes are not pit vipers and their bites should not be treated with FabAV. A previously available Wyeth antivenin for Micruris fulvius is no longer manufactured. Victims of bites by M fulvius (eastern coral snake) and M tener (Texas coral snake) should receive general wound care and supportive care, including respiratory support in the event of respiratory failure. Poison control and toxicologist consultation should be contacted for suspected coral snake envenomations to obtain the latest location-specific treatment recommendations. See also Coral Snake Envenomation.

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Surgical Care

Surgical assessment focuses on the injury site and concern for the development of compartment syndrome. Fasciotomy is indicated only for those patients with objective evidence of elevated compartment pressure. Liberal monitoring of compartment pressure is warranted. If this is not available, use the physical hallmark of compartment hypertension (pain with passive range of motion), along with distal pallor, paresthesia, or pulselessness for the clinical assessment.

Tissue injury after compartment syndrome is not reversible but is preventable.

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Consultations

Contacting the poison control center is important. Consultation with a surgeon often is warranted in bite management. General and trauma surgeons often have experience with envenomation, resuscitation, complications, and wound care. They can lead the inpatient treatment.

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Complications

Coagulopathy, including delayed coagulopathy, is a frequent complication of pit viper snakebite. Local wound complications may include infection and skin loss.

Cardiovascular complications, hematologic complications, and pulmonary collapse may occur. Neurotoxicity with myokymia of the respiratory muscles may lead to respiratory failure and mechanical ventilation. True compartment syndrome is a rare complication. Death is rare.

Prolonged neuromuscular blockade may occur from coral snake envenomation.

Antivenin-associated complications include immediate (anaphylaxis, type I) and delayed (serum sickness, type III) hypersensitivity reactions. Anaphylaxis is an event mediated by immunoglobulin E (IgE), involving degranulation of mast cells that can result in laryngospasm, vasodilatation, and leaky capillaries. Death is common without pharmacological intervention. Serum sickness occurs 1-2 weeks after administering antivenin. Precipitation of antigen-immunoglobulin G (IgG) complexes in the skin, joints, and kidneys is responsible for the arthralgias, urticaria, and glomerulonephritis (rarely). Usually more than 8 vials of antivenin must be given to produce this syndrome. Supportive care consists of antihistamines and steroids. Newer studies now report a lower incidence (5.4%) of acute hypersensitivity reactions with FabAV.[19]

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Prevention

Wear protective clothing and never handle snakes.

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Contributor Information and Disclosures
Author

Brian J Daley, MD, MBA, FACS, FCCP, CNSC Professor and Program Director, Department of Surgery, Chief, Division of Trauma and Critical Care, University of Tennessee Health Science Center College of Medicine

Brian J Daley, MD, MBA, FACS, FCCP, CNSC is a member of the following medical societies: American Association for the Surgery of Trauma, Eastern Association for the Surgery of Trauma, Southern Surgical Association, American College of Chest Physicians, American College of Surgeons, American Medical Association, Association for Academic Surgery, Association for Surgical Education, Shock Society, Society of Critical Care Medicine, Southeastern Surgical Congress, Tennessee Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

Sneha Bhat, MD Resident Physician, Department of Surgery, University of Tennessee Health Science Center College of Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Daniel R Ouellette, MD, FCCP Associate Professor of Medicine, Wayne State University School of Medicine; Chair of the Clinical Competency Committee, Pulmonary and Critical Care Fellowship Program, Senior Staff and Attending Physician, Division of Pulmonary and Critical Care Medicine, Henry Ford Health System; Chair, Guideline Oversight Committee, American College of Chest Physicians

Daniel R Ouellette, MD, FCCP is a member of the following medical societies: American College of Chest Physicians, Society of Critical Care Medicine, American Thoracic Society

Disclosure: Nothing to disclose.

Chief Editor

Joe Alcock, MD, MS Associate Professor, Department of Emergency Medicine, University of New Mexico Health Sciences Center

Joe Alcock, MD, MS is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Additional Contributors

Lisa Kirkland, MD, FACP, FCCM, MSHA Assistant Professor, Department of Internal Medicine, Division of Hospital Medicine, Mayo Clinic; Vice Chair, Department of Critical Care, ANW Intensivists, Abbott Northwestern Hospital

Lisa Kirkland, MD, FACP, FCCM, MSHA is a member of the following medical societies: American College of Physicians, Society of Hospital Medicine, Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Chandler Long, MD Resident Physician, Department of Surgery, University of Tennessee Medical Center-Knoxville

Disclosure: Nothing to disclose.

A Mariah Alexander, MD Resident Physician, Department of Surgery, University of Tennessee Graduate School of Medicine, Knoxville

A Mariah Alexander, MD is a member of the following medical societies: American College of Surgeons, Society of American Gastrointestinal and Endoscopic Surgeons

Disclosure: Nothing to disclose.

References
  1. Barlow A, Pook CE, Harrison RA, Wüster W. Coevolution of diet and prey-specific venom activity supports the role of selection in snake venom evolution. Proc Biol Sci. 2009 Jul 7. 276(1666):2443-9. [Medline].

  2. Johnson CA. Management of snakebite. Am Fam Physician. 1991 Jul. 44 (1):174-80. [Medline].

  3. Kasturiratne A, Wickremasinghe AR, de Silva N, Gunawardena NK, Pathmeswaran A, Premaratna R, et al. The global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths. PLoS Med. 2008 Nov 4. 5 (11):e218. [Medline].

  4. Alirol E, Sharma SK, Bawaskar HS, Kuch U, Chappuis F. Snake bite in South Asia: a review. PLoS Negl Trop Dis. 2010 Jan 26. 4 (1):e603. [Medline].

  5. Vaiyapuri S, Vaiyapuri R, Ashokan R, Ramasamy K, Nattamaisundar K, Jeyaraj A, et al. Snakebite and its socio-economic impact on the rural population of Tamil Nadu, India. PLoS One. 2013. 8 (11):e80090. [Medline].

  6. Sotelo N. Review of treatment and complications in 79 children with rattlesnake bite. Clin Pediatr (Phila). 2008 Jun. 47(5):483-9. [Medline].

  7. Weinstein S, Dart R, Staples A, White J. Envenomations: an overview of clinical toxinology for the primary care physician. Am Fam Physician. 2009 Oct 15. 80(8):793-802. [Medline].

  8. Spiller HA, Bosse GM. Prospective study of morbidity associated with snakebite envenomation. J Toxicol Clin Toxicol. 2003. 41(2):125-30. [Medline].

  9. Scharman EJ, Noffsinger VD. Copperhead snakebites: clinical severity of local effects. Ann Emerg Med. 2001 Jul. 38(1):55-61. [Medline].

  10. Gold BS, Dart RC, Barish RA. Bites of venomous snakes. N Engl J Med. 2002 Aug 1. 347 (5):347-56. [Medline].

  11. Darracq MA, Cantrell FL, Klauk B, Thornton SL. A chance to cut is not always a chance to cure- fasciotomy in the treatment of rattlesnake envenomation: A retrospective poison center study. Toxicon. 2015 Jul. 101:23-6. [Medline].

  12. Cumpston KL. Is there a role for fasciotomy in Crotalinae envenomations in North America?. Clin Toxicol (Phila). 2011 Jun. 49 (5):351-65. [Medline].

  13. Mazer-Amirshahi M, Boutsikaris A, Clancy C. Elevated compartment pressures from copperhead envenomation successfully treated with antivenin. J Emerg Med. 2014 Jan. 46 (1):34-7. [Medline].

  14. Corneille MG, Larson S, Stewart RM, et al. A large single-center experience with treatment of patients with crotalid envenomations: outcomes with and evolution of antivenin therapy. Am J Surg. 2006 Dec. 192(6):848-52. [Medline].

  15. Dart RC, Seifert SA, Boyer LV, et al. A randomized multicenter trial of crotalinae polyvalent immune Fab (ovine) antivenom for the treatment for crotaline snakebite in the United States. Arch Intern Med. 2001 Sep 10. 161(16):2030-6. [Medline].

  16. Lavonas EJ, Gerardo CJ, O'Malley G, et al. Initial experience with Crotalidae polyvalent immune Fab (ovine) antivenom in the treatment of copperhead snakebite. Ann Emerg Med. 2004 Feb. 43(2):200-6. [Medline].

  17. Vohra R, Cantrell FL, Williams SR. Fasciculations after rattlesnake envenomations: a retrospective statewide poison control system study. Clin Toxicol (Phila). 2008 Feb. 46(2):117-21. [Medline].

  18. Richardson WH, Goto CS, Gutglass DJ, Williams SR, Clark RF. Rattlesnake envenomation with neurotoxicity refractory to treatment with crotaline Fab antivenom. Clin Toxicol (Phila). 2007 Jun-Aug. 45(5):472-5. [Medline].

  19. Cannon R, Ruha AM, Kashani J. Acute hypersensitivity reactions associated with administration of crotalidae polyvalent immune Fab antivenom. Ann Emerg Med. 2008 Apr. 51(4):407-11. [Medline].

  20. Gold BS, Dart RC, Barish RA. Bites of venomous snakes. N Engl J Med. 2002 Aug 1. 347(5):347-56. [Medline].

 
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Snakebite. Western diamondback rattlesnake.
Snakebite. Western coral snake.
Snakebite. Southern Copperhead snake, from snakesandfrogs.com
Snakebite. Copperhead bite day 3; initial wounds to finger.
Snakebite. Copperhead bite day 3; initial wounds to finger.
Snakebite. Copperhead bite day 3; initial wounds to finger.
Snakebite. Comparison of the harmless Lampropeltis triangulum annulata (Mexican milksnake) (top) with Micrurus tener (Texas coral snake) (bottom). Photo by Charles Alfaro.
Snakebite. Juvenile southern Pacific rattlesnake (Crotalus oreganus helleri). Photo by Sean Bush, MD.
Snakebite. Moderate rattlesnake envenomation in a toddler after treatment with antivenom. Photo by Sean Bush, MD.
Table 1. Snakebite Severity Scale
Criteria Signs/Symptoms Score
Pulmonary    
  No symptom/sign 0
  Dyspnea, minimal chest tightness, mild or vague discomfort, or respirations of 20-25 breaths/min 1
  Moderate respiratory distress (tachypnea, 26-40 breaths/min, accessory muscle use) 2
  Cyanosis, air hunger, extreme tachypnea, or respiratory insufficiency/failure 3
Cardiovascular    
  No symptom/sign 0
  Tachycardia (100-125 beats/min), palpitations, generalized weakness, benign dysrhythmia, or hypertension 1
  Tachycardia (126-175 beats/min) or hypotension with systolic blood pressure < 100 mm Hg 2
  Extreme tachycardia (>175 beats/min) or hypotension with systolic blood pressure < 100 mm Hg, malignant dysrhythmia, or cardiac arrest 3
Local wound No symptom/sign (swelling or erythema < 2.5 cm of fang mark) 0
  Pain, swelling, or ecchymosis within 5-7.5 cm of bite site 1
  Pain, swelling, or ecchymosis involving less than half of the extremity (7.5 cm from site) 2
  Pain, swelling, or ecchymosis extending beyond affected extremity (>100 cm from site) 3
Gastrointestinal    
  No symptom/sign 0
  Pain, tenesmus, or nausea 1
  Vomiting or diarrhea 2
  Repeated vomiting or diarrhea, hematemesis, hematochezia 3
Hematological    
  No symptom/sign 0
  Coagulation parameters slightly abnormal (PTa < 20 seconds, PTTb < 50 seconds, platelets 100,000-150,000/µL, fibrinogen 100-150 mcg/mL) 1
  Coagulation parameters abnormal (PT < 20-50 seconds, PTT < 50-75 seconds, platelets 50,000-100,000/µL, fibrinogen 50-100 mcg/mL) 2
  Coagulation parameters abnormal (PT < 50-100 seconds, PTT < 75-100 seconds, platelets 20,000-50,000/µL, fibrinogen < 50 mcg/mL) 3
  Coagulation parameters markedly abnormal, with serious bleeding or threat of spontaneous bleeding (PT or PTT unmeasurable, platelets < 20,000/µL, fibrinogen undetectable), with severe abnormalities in other laboratory values, including venous clotting time 4
Central nervous system    
  No symptom/sign 0
  Minimal apprehension, headache, weakness, dizziness, chills, or paresthesia 1
  Moderate apprehension, headache, weakness, dizziness, chills, paresthesia, confusion, or fasciculation in area of bite site, ptosis, and dysphagia 2
  Severe confusion, lethargy, seizure, coma, psychosis, or generalized fasciculation 3
  Extremely severe envenomation leading to death 4
a PT = Prothrombin time.



b PTT = Partial thromboplastin time.



Table 2. Severity of Envenomation
Type of Signs/Symptoms Minimal Moderate Severe
Local Swelling, erythema, or ecchymosis confined to bite site Progression of swelling, erythema, or ecchymosis beyond bite site Rapid swelling, erythema, or ecchymosis involving the entire body part
Systemic No systemic signs or symptoms Non–life-threatening signs or symptoms (nausea/vomiting, mild hypotension, perioral paresthesias, myokymia) Markedly severe signs or symptoms (hypotension [systolic < 80 mm Hg], altered sensorium, tachycardia, tachypnea, and respiratory distress)
Coagulation No coagulation abnormalities or other laboratory abnormalities Mild abnormal coagulation profile without significant bleeding Abnormal coagulation profile with bleeding (INRa, aPTTb, fibrinogen, platelet count < 20,000/µL
Snakebite Severity Score 0-3 4-7 8-20
a INR = International normalized ratio.



b aPTT = Activated partial thromboplastin time.



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