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Diagnosis & Treatment — General practitioner / health post

 

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.

 

At particular risk are: children, elderly people, patients with pre-existing conditions, such as coronary heart disease, arterial hypertension, lung disease, kidney disease, allergies (sensitisation), patients with predilection sites for bleeding such as gastrointestinal ulcers, kidney stones, pulmonary cavities (tuberculous), and patients taking particular drugs, such as coumarin derivatives, platelet aggregation inhibitors and beta-blockers.

Patient presents with a tourniquet or compression bandage on the affected extremity

D  Diagnostics

Check venous and arterial blood supply in the extremity.

C  Comments

If a tourniquet or compression bandage has been applied, it should not be removed until antivenom is at hand, venous access has been accomplished and the means for treating complications, including possible complications caused by the antivenom, are available.

If these requirements cannot be met within a suitable period of time, it is necessary to weigh the risk of the systemic effects of the venom that could occur after removing the tourniquet or compression bandage against the risk of progressive local tissue damage that may arise if the bandage is left in place.

Is it likely that a clinically relevant injection of venom has taken place?

D  Diagnostics

Inquire:

  • time of the bite,
  • local pain,
  • nausea, vomiting, diarrhoea, abdominal pain,
  • retrosternal pain.

Assess:

  • state of consciousness.

Measure:

  • blood pressure/pulse,
  • respiratory rate.

Observe/investigate:

  • bite marks,
  • extent and intensity of the swelling,
  • bleeding in the region of the swelling (ecchymoses),
  • enlargement and painfulness of regional lymph nodes,
  • swelling in the facial region, including the larynx/pharynx (angio-oedema),
  • bronchospasm,
  • clinical signs of shock,
  • signs of systemic bleeding (very rare),
  • signs of paralysis (very rare).

Determine:

  • venom concentration in the serum/urine using the ELISA method (clinically proven and standardised tests are not yet commercially available), 
  • clotting time (bedside test),
  • urinary output.
C  Comments

The symptoms and degree of envenoming depend not only on the amount of venom injected and numerous other variables, but also on the time that has elapsed since the bite. This variable factor must be taken into account when making the following decisions:

  • exclusion of envenoming (see below),
  • the time interval between clinical examinations (see Therapy phase: Hospital),
  • emergency care.

The following signs and symptoms are observed following European viper bites and are indicative of a relevant injection of venom:

  • local pain, swelling and skin changes (in particular ecchymoses),
  • nausea, vomiting, diarrhoea, abdominal pain,
  • arterial hypotension,
  • signs of shock (pallor, sweating, tachycardia, arterial hypotension, alterations in consciousness).
  • neurological signs and symptoms, in particular cranial nerve deficits (rare and only in certain geographical areas).

The severity of envenoming at the time of investigation can be estimated from the constellation of signs and symptoms found (see Table 4.12).

ELISA tests are not yet commercially available. However, they are a promising method that will have a high predictive value for the expected severity of envenoming as soon as they are clinically proven and standardised (see Table 4.12).

Exclusion of a relevant injection of venom

D  Diagnostics

Clinical:

No swelling/oedema in the region of the bite within 2 h and no signs or symptoms apart from those that can be attributed to the psychological trauma of a snakebite.

C  Comments

The relationship between swelling oedema at the site of the bite and systemic envenoming was investigated in a prospective study by Audebert et al. (1992). With regard to systemic envenoming, swelling / oedema at the bite site had a sensitivity of 100%, a specificity of 85%, a positive predictive value of 65% and a negative predictive value of 100%. In this study it was also found that in all patients who developed swelling /oedema at the site of the bite, it commenced within the first 2 h.

Symptomatic emergency medical treatment

S  Signs & Symptoms

Clinical signs of anaphylactic/anaphylactoid shock.

T  Treatment
  • Treatment of the anaphylactic/anaphylactoid shock,
  • antivenom.
S  Signs & Symptoms

Persistent or recurrent arterial hypotension.

T  Treatment
  • Treatment of acute transient, persistent or recurrent arterial hypotension (fluids iv),
  • antivenom.
S  Signs & Symptoms

Extensive swelling, possibly involving the trunk (regional fluid sequestration caused by increased capillary permeability) → hypovolaemia, hypovolaemic shock.

T  Treatment
  • Treatment of the hypovolaemia/hypovolaemic shock,
  • possibly antivenom.
S  Signs & Symptoms

Clinical signs of myocardial damage/cardiogenic shock (extremely uncommon).

T  Treatment
  • Treatment of cardiac ischaemia/cardiogenic shock,
  • antivenom.
C  Comments

Symptomatic emergency medical treatment and antivenom treatment are complementary strategies.

The aim of symptomatic emergency medical treatment is the rapid correction of critical parameters (fluid balance, blood pressure, oxygenation etc.) and the maintenance of vital functions (respiratory, cardiovascular).

Symptomatic measures help bridge the gap until specific treatment (antivenom) can be administered and starts being effective. If no antivenom is available or if the required effect is not achieved with antivenom, the goal is to employ symptomatic measures until such time as the venom naturally starts losing its activity. 

Retrospective and prospective studies have shown that the majority of cases of envenoming caused by European vipers can be successfully treated with symptomatic treatment alone, under optimal intensive care conditions (see the Biomedical database entry).

However, in certain circumstances administration of antivenom is indicated (see below).

Who requires antivenom?

D  Diagnostics

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.

How is the appropriate antivenom chosen?

D  Diagnostics

How are antivenoms administered and complications caused by antivenoms treated?

T  Treatment
C  Comments

Symptomatic emergency medical treatment and antivenom treatment are complementary strategies.

The aim of antivenom treatment is neutralisation of the venom. The success of antivenom treatment depends on the quality of the antivenom, the specific properties of those venom components relevant to envenoming and the time point at which antivenom is administered.

Local treatment
Bite wound, including the surrounding reaction

D  Diagnostics
  • Assessment of the wound according to the usual criteria.
  • Swelling: assessment of the extent and increase in magnitude; regional signs of haemorrhage.
  • Long-term: observation for the formation of necrosis.
T  Treatment
  • Cleaning and dressing the wound.
  • Immobilisation of the extremity with a splint.
  • Padding and monitoring to prevent pressure necrosis and disturbance of the blood circulation if the oedema increases.
C  Comments

Prophylactic antibiotic treatment is controversial. In most cases that occur in Europe, regular wound inspection and treatment will be sufficient initially. The decision to start antibiotic treatment should be made as soon as the infection criteria are fulfilled.

Tetanus

T  Treatment

Tetanus prophylaxis.