Diagnosis & Treatment — Hospital
General problems
This Diagnosis & Treatment section is based on analysis of envenoming caused by V. aspis and V. berus and to a small extent by V. ammodytes (see the Biomedical database entry for Vipera sp. (European vipers)). Documented cases of envenoming due to V. latasti, V. kaznakovi, V. lebetina, V. seonaei and V. ursini are rare or simply not available. See also Diagnosis & Treatment: Terrestrial snakes: North Africa, Near and Middle East and the Biomedical database entry. The signs and symptoms of envenoming caused by V. ammodytes, V. aspis, V. berus, V. latasti and V. ursini are described as being similar with the exception of V.berus, V.ammodytes and in particular V.aspis in which neurotoxic effects are observed in certain geograpgical areas (Warrell 2010). Envenoming due to colubrids and the pitviper Gloydius halys in Europe is similarly poorly documented or not at all.
Who requires antivenom?
Antivenom indications
- Drop in blood pressure (systolic to <80 mmHg or around >50 mmHg compared to the systolic blood pressure at the initial investigation) with or without signs of shock (Warrell 2005, 2010).
- Signs of systemic envenoming, such as spontaneous bleeding, coagulopathy, pulmonary oedema or pulmonary haemorrhage (chest X-ray), ECG abnormalities, leucocytosis and elevated serum creatin kinase (Warrell 2005, 2010).
- Severe local signs of envenoming, even in the absence of systemic signs of envenoming: swelling that involves >1/2 of the affected extremity within 48 h, or rapidly spreading local swelling that reaches the forearm or lower leg within about 4 h of the bite (Warrell 2005, 2010).
- Cranial nerve deficits, such as facial diplegia, pharyngo-laryngeal paralysis, bilateral ptosis and external ophthalmoplegia, dysphonia, dysphagia, paraysis of skeletal muscles may be an additional indication given the experince e.g. in Souh-Eastern France (de Harro et al 2002)
see the Biomedical database entry.
Autopharmacological effects
- Nausea, vomiting, diarrhoea, abdominal colic, incondinence for urine and faeces
- urticaria, angio-oedema
- dyspnoea, bronchospasm
- arterial hypotension, shock.
Clinical.
- Treatment of the anaphylactic/anaphylactoid shock,
- antivenom.
Persistent or recurrent arterial hypotension.
Clinical.
- Treatment of acute transient, persistent or recurrent arterial hypotension (fluids iv)
- antivenom.
One of the major complications following bites from European vipers is a state of acute transient, persistent or recurrent arterial hypotension. Arterial hypotension combined with other signs of an allergic/anaphylactic reaction, such as urticaria, angio-oedema and bronchospasm, generally commence directly following the bite, can, however, be delayed for several hours (Warrell 2005, 2010). This applies to autopharmacological but also to allergic, IgE-mediated reactions which also can be delayed or biphasic (Stark and Sullivan 1986)
Local effects
- Local swelling that can extend to the trunk,
- local signs of haemorrhage (ecchymoses).
- Clinical:
- extent and intensity of the swelling.
- intravenous fluids to correct hypotension if there is extensive or rapidly progressive swelling,
- antivenom.
The oedema can take on immense proportions and involve large areas of the trunk, such that it may be a cause of hypovolaemia and arterial hypotension.
If swelling is the only symptom of envenoming present, then the benefits and risks of antivenom treatment must be carefully weighed. In the great majority of such cases antivenom is not necessary (see Biomedical database entry).
Extreme swelling of the bitten extremity, pain and difficulty moving the fingers or toes can mimic compartment syndrome. Compartment syndrome following European viper bites is extremely uncommon, if it occurs at all. A tentative diagnosis of compartment syndrome must therefore always be confirmed by Doppler investigation and measurement of intra-compartmental pressure before surgical intervention is considered.
Permanent tissue damage is almost always the result of inappropriate first aid and paramedical measures.
Haemostatic effects
- Clinical signs of systemic bleeding,
- clinical signs of haemolysis.
- Clinical,
- laboratory parameters:
- Hb, Hct,
- clotting time,
- PT/aPTT,
- TT,
- fibrinogen,
- FSP,
- D-dimers,
- free haemoglobin in plasma and urine,
- haptoglobin,
- blood group/blood sample for cross-matching.
- Antivenom
- Blood transfusion (very rarely needed)
A decrease in haemoglobin levels has been observed as a consequence of extravasation of erythrocytes in the region of extensive swelling. From Sweden there have been reports of haemolysis following V. berus bites (Persson and Irestedt 1981).
Systemic bleeding is extremely rare. Significant changes in the haemostatic parameters with or without clinical manifestations are an exception even in cases of severe envenoming.
Ecchymoses in the region of the swelling are common and do not represent an indication for antivenom administration.
Neurological effects
- Predominately cranial nerve deficits, such as facial diplegia, pharyngo-laryngeal paralysis, bilateral ptosis and external ophthalmoplegia, dysphonia, dysphagia, but also dyspnoea
- Signs of paralysis of the skeletal musculature.
Clinical.
Antivenom.
Cases of V. aspis bites with signs and symptoms of neurotoxicity have been described for Italy (Antonini et al. 1991, Beer and Putorti 1998, Re et al 1999) and South-Eastern France (de Haro et al 1994, 2002). 5 patients with neurotoxic signs and symptoms in South-Eastern France responded favouably to Purified equine F(ab')2 antivenom (Viperfav™) (de Haro et 2002). Mild neurotoxicity has also been described after bites of other European vipers (Warrell 2010).
Cardiac effects
- Retrosternal pain,
- cardiac dysrhythmias,
- cardiac insufficiency/failure.
- Clinical,
- blood pressure, pulse,
- ECG,
- enzymes: CK-MB, GOT, LDH.
Antivenom.
Myocardial damage in association with bites by European vipers has been reported but is extremely rare (see the Biomedical database entry). There is no conclusive evidence of a primary cardiotoxic effect of the venom in humans. On the other hand, ECG changes (T-wave inversion, tachy and bradyarrhythmias, atrial fibrilation, second degree hardblock) have been observed in patients with European viper bites (Reid 1976, Paersson et al 1981, commented by Warrell 2010).
Renal effects
- Flank pain, renal bed sensitive to percussion,
- eyelid oedema,
- oliguria/anuria, polyuria.
- Clinical,
- urine output (balance, hourly),
- laboratory parameters:
- serum creatinine,
- serum potassium,
- serum bicarbonate.
Symptomatic treatment.
Clinically relevant renal dysfunction is rare. If it occurs, it is probably (always) secondary, i.e. primarily a consequence of arterial hypotension.
How is the appropriate antivenom chosen?
- See Emergency flowchart: Europe,
- see the WHO Antivenom list,
- see the Biomedical database entry.
The venoms of European vipers show a high degree of cross-antigenicity among each other. Thus the various antivenoms produced against the venoms of European vipers cross-react very well.
For detailed information on the experiences with the various antivenoms available see the Biomedical database entry).
How are antivenoms administered and complications caused by antivenoms treated?
Monitoring of the patient
1. After administration of antivenom (assessment of success of antivenom or indication for continued antivenom treatment)
Specific examinations are primarily based on the signs and symptoms as well as laboratory parameters that were used to determine the indications for antivenom administration.
Signs of envenoming can recur after successful treatment with antivenom. One explanation for this is the continued absorption of venom from a depot in the region of the bite.
A sufficiently long follow-up period (at least 24 h) is necessary.
2. Patients for whom the initial examination provided no indication for antivenom administration
At least hourly investigations initially:
- state of consciousness,
- heart rate and rhythm,
- arterial blood pressure,
- respiratory rate,
- spontaneous bleeding,
- ptosis,
- local swelling,
- other newly appearing signs and symptoms.
6-hourly investigations (or more frequently if necessary):
- monitoring of haemostasis.
A complicated course of envenoming requiring antivenom treatment can be excluded if within a 24-hour observation period
- the oedema ceases to increase in extent,
- neither hypotension nor shock have occurred,
- haemostasis is unimpaired,
- there are no cardiac symptoms and no ECG changes.
Follow-up
1. Wounds, in particular necrosis
- Inspection,
- bacterial smears.
- Change of dressing,
- antibiotic treatment.
2. Functional state of the bitten extremity
Clinical.
Physiotherapy.