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.
- Oliguria or anuria
- Lungs
- ARDS
- Often preventable if shock has been avoided
- ARDS
- 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 indications for snake antivenom include
- 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
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