Adder (Vipera berus) bite

Essentials

  • An adder bite may be dangerous to a child. If a bite is suspected refer the child to a hospital.
  • Mortality is 1–2 ‰.
  • The symptoms are variable. About 75% of viper bite victims have local symptoms only, and about 25% have more severe general symptoms. Anaphylactic reactions also occur.
  • The bite wound may be atypical.
  • The venom is "injected" deep in the tissues. It is no use trying to remove the venom.

Venom

  • The venom is pharmacologically complex, and its composition varies (several enzymes causing tissue destruction, fibrinogen degradation, etc., other proteins and peptides, free amino acids).
  • The most important effects are on the circulatory system and blood coagulation (hemotoxin).
  • The body's reactions may further complicate the situation.
    • The liberation of bradykinin, histamine, etc. causes vasodilatation and collapse.

Effects of the venom

  • Rapid increase in capillary permeability lasting 2–3 days
    • Local swelling and pain
    • Skin discolouration (skin turns dark and purple), petechiae
    • Fluid extravasation leading to shock
    • Platelet extravasation
  • Cell destruction
    • Liberation of histamine and other vasoactive substances leading to vasodilatation and shock
  • Central nervous system symptoms are common.
    • Impaired consciousness, convulsions, headache
  • Gastointestinal symptoms are common
    • Vomiting, diarrhoea, abdominal pain
  • Kidneys
    • Oliguria or anuria
      • Can often be avoided with sufficient fluid therapy.
  • Lungs
    • ARDS
      • Often preventable if shock has been avoided
  • Blood
    • Haemolysis leading to free haemoglobin in the plasma
    • Platelet destruction and extravasation
    • Degradation of some clotting factors
    • Disseminated intravascular coagulation
  • Heart
    • Arrhythmias, ST changes, ischaemia

Other symptoms

  • Sweating
  • Allergic symptoms
    • Exanthema, urticaria, angioneurotic oedema, bronchospasm, anaphylaxis, etc.
  • Delayed symptoms
    • Toxic neuropathy of the extremities (sensory disturbance lasting for months)
    • Secondary infections
    • Large bullae, necroses
    • Skin discolouration may last for 1–2 months.

Treatment

At the site of the bite accident

  • Self-help package (containing e.g. 150 mg of hydrocortisone)
    • Stabilizes cell membranes and decreases the liberation of vasoactive substances.
    • The efficacy has not been proven and cannot be relied upon.
    • Incisions and sucking of blood from the wound are ineffective.
  • Tourniquet [Evidence Level: C]
    • May be beneficial if transportation takes a long time.
    • Must be opened for five minutes every hour.
  • Immobilization [Evidence Level: C]
    • It is very important for the patient to avoid moving the limb him/herself, since the muscle pump pumps the poison forward
    • Immobilize with a splint and carry the patient from the site of the accident
    • Elevation of the limb reduces swelling if the transportation distance is long.

First aid

  • I.v. infusion (physiological saline) as soon as possible
  • Methylprednisolone 2 mg/kg i.v. (maximum dose 120 mg/24 h)
    • The efficacy has not been proven.
  • Treatment of anaphylaxis if necessary (Anaphylaxis)
  • Transportation to a hospital, preferably with an escort

Treatment in the hospital

  • Follow-up
    • Adults should be followed up for 6–8 hours, children for 1–2 days. The follow-up should be intensive for small children.
  • If systemic symptoms develop the patient should be transferred to an intensive care unit.
  • Fluid therapy in the beginning (during the first 2–4 days) is crucially important.
    • Ringer's solution + colloid, large amounts if necessary
    • The infusion rate is determined by the clinical response (peripheral circulation, diuresis, haematocrit, heart rate, acid-base balance).
  • Methylprednisolone i.v. in doses of 2 mg/kg once or several times
    • The efficacy has not been proven.
  • Treatment of the kidneys
    • Fluid therapy and diuretics if necessary
  • Antimicrobials are only given if there are signs of infection.
  • Tetanus immunization
  • Pain relief: paracetamol 15–20 mg/kg every 8 hours. Maximum daily dose for adults 4 g, for children 60 mg/kg. Anti-inflammatory drugs should be avoided because of possible kidney damage.
  • Snake antivenom [Evidence Level: C]
    • The indications for snake antivenom include
      • rapidly progessing or disseminated oedema
      • recurrent or therapy-resistant cardiovascular symptoms
      • prolonged or recurrent intensive abdominal pain and vomiting
      • angioneurotic oedema and risk of obstruction of the respiratory passages.
    • In controversial cases the decision to start antivenom therapy is supported by the following laboratory findings: early leucocytosis (> 15–20 × 109/l) 1 , metabolic acidosis, haemolysis, ECG abnormalities, disturbances of blood coagulation.
    • Administer the antivenom with glucocorticoids to avoid allergic reactions; be prepared for allergic reactions.
    • The antivenom should be given as soon as possible after indications have been established.
    • A fragmented antivenom is available (Viperatab® as primary therapy).
    • The dose is per bite, not per kilogram.
  • The vital functions should be monitored and supported by means of intensive care.
  • Blood component therapy as necessary: red cells, coagulation factors, platelets, etc.
  • The site of the bite should be kept dry. Do not break any vesicles.
  • Symptomatic treatment (e.g. analgesic, sedative, diuretic, anticonvulsant drugs)
  • Thromboprophylaxis at discretion. Thromboprophylaxis is particularly necessary in adults if oedema and pain prevent moving the limb.

Follow-up

  • Always
    • Body weight, limb circumference, heart rate, blood pressure, diuresis
    • Peripheral pulses and sensation; pay attention to the risk of muscle compartment syndrome (Muscle compartment syndromes) if the bite is in a limb.
  • In mild systemic symptoms
    • As above + basic blood count, blood group, urinalysis (protein, haemoglobin)
  • In moderate systemic symptoms
    • As above + acid-base balance, plasma sodium and potassium, cross test, chest radiograph, ECG
  • In severe systemic symptoms
    • As above + plasma urea, creatinine, bleeding time, APTT, INR, plasma calcium, serum osmolality, protein, plasma creatine kinase, urine sodium and potassium, urine osmolality; reservation of transfusable blood
    • It is important to follow up the patient's bleeding/blood coagulability status both clinically and with laboratory tests.
  • 1–2 weeks after treatment with antivenom the patient may have fever, limb pains and fatigue (serum sickness). Give glucocorticoids if needed.
  • A control visit is scheduled after 1–2 weeks if the patient has had severe general symptoms or has received snake antivenom.

References

1. Grönlund J, Vuori A, Nieminen S. Adder bites. A report of 68 cases. Scand J Surg 2003;92(2):171-4.  [PMID:12841560]
2. Gold BS, Dart RC, Barish RA. Bites of venomous snakes. N Engl J Med 2002 Aug 1;347(5):347-56.  [PMID:12151473]

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