Is it an Emergency?

Inquire

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

Assess

• state of consciousness.

Measure

• blood pressure/pulse,
• respiratory rate,
• oxygen saturation (pulse oximeter),
• 20WBCT (bedside test).

Observe/investigate

• bite marks,
• extent and intensity of local swelling,
• eyes: conjunctivitis, corneal lesions, uveitis (spitting cobras!),
• enlargement and painfulness of regional lymph nodes,
• swelling in the facial region, including the larynx/pharynx (angio-oedema),
• conjunctival oedema,
• clinical signs of a pleural effusion, pulmonary oedema,
• clinical signs of shock,
• bleeding in the region of the swelling,
• bleeding from bite marks and other injuries,
• gingival bleeding,
• blood-stained sputum, vomit ("coffee ground vomitus"), stools (melaena) or urine,
• acute abdomen (intra-abdominal bleeding!),
• focal neurological deficits, meningismus (intracranial bleeding!),
• cranial nerve deficits, such as ptosis, ophthalmoplegia, dysphagia, dysarthria,
• paralysis of the skeletal musculature including the respiratory musculature (→ respiratory insufficiency/respiratory failure),
• myalgia with active and passive movement and upon pressure,
• dark-brown/red urine (differential diagnosis haemoglobinuria)(rhabdomyolysis!),
• flank pain and renal bed sensitive to percussion,

Varibility of symptoms and degree of envenoming

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 
• the time interval between clinical examinations
• emergency care (see below)

Bite marks and dry bites

The fact that a patient has been bitten by a known venomous snake and the presence of bite marks do not automatically allow the conclusion that a clinically relevant injection of venom has taken place. A substantial proportion (up to 50 % are reported) of confirmed bites, including cobra bites, proceed with no detectable symptoms or at the most negligible local signs of envenoming.

Autopharmacological signs & symptoms

The venom of vipers in particular can cause clinical symptoms of autopharmacological venom effects and anaphylaxis in patients within minutes after the bite occuring with Actractaspis engaddensis and A. microlepidota, Bitis arientans, Daboia palaestinae and Macrovipera sp. (Efrati 1979, Leviton et al. 1992, Warrell et al. 1975).
“Acute profound hypotension with or without other features of anaphylaxis is part of the autopharmacological syndrome which may occur within minutes of bites by Daboia species. It may be caused by release of endogenous vasoactive compounds such as nitric oxide, kinins, histamine, serotonin and endothelins” (Warrell 2023).
"Early, repeated, usually transient but sometimes persistent and fatal, syncopal attacks with features of anaphylaxis may develop in patients not previously exposed to venom who have been bitten by some Viperidae, notably also Daboia palaestinae" (Warrell 2023).
Amr et al. (2020) describe “Within 15–20 min after the initial pain of the bite, victims report a sudden sense of weakness, and restlessness, and begin to vomit and sweat. Abdominal pain is associated with diarrhoea which may be watery and blood-stained. There is an anaphylactic syndrome: angioedema affects lips and face, the tongue, which may swell to “several times its normal size”, the glottis (requiring tracheostomy in one case); urticaria; tachycardia; hypotension and shock causing collapse and unconsciousness.”

Local signs & symptoms

Bitesite
The fact that a patient has been bitten by a known venomous snake and the presence of bite marks do not automatically allow the conclusion that a clinically relevant injection of venom has taken place.

On the other hand, local signs, e.g. swelling at the site of the bite, following viperid bites as well as bites of some elapid species (N. nigricollis, N. nubiae, N. katiensis, Walterinnesia aegyptia) are generally an indication that a significant injection of venom has occurred.

With bites from the Cobra species N. haje (and possibly N.arabica, N. melanleuca and N. senegalensis), however, local signs of envenoming may be absent even in cases of severe systemic envenoming (Visser and Chapman 1978, Warrell et al. 1976a).

Atractaspis sp.: as a rule there is generally at least mild local swelling following injection of venom (Warrell et al. 1976c).

Bitis arietans: marked local swelling that often extends to the trunk and causes necrosis (Warrell et al. 1975, Marsh and Whaler 1984).

Causus sp.: local swelling generally appears to occur following injection of venom, but is only marked in a small proportion of cases (Warrell et al. 1976c).

Cerastes cerastes: Local pain, local swelling extending to the entire bitten limb. Local necrosis (Schneemann et al. 2004).

Echis sp.: local swelling always occurs if venom has been injected, but may be only mild (Porath et al. 1992, Warrell et al. 1977).

Daboia palaestinae and Macrovipera lebetina: extensive swelling that may extend to the trunk, necrosis possible but rarely severe as long as the bite is not on the fingers or toes (Efrati 1979, Leviton et al. 1992).

Naja nigricollis: local swelling may be very extensive, possibly involving the trunk, necrosis (Warrell et al. 1976b).

Naja haje: local signs of envenoming usually absent or insignificant (Warrell et al. 1976b, Blaylock et al. 1985, Visser and Chapman 1978).

Walterinnesia aegyptia: local swelling (Yayon et al. 1988).

Compartment syndrome

Even extensive swelling of the extremities is not necessarily an indication of compartment syndrome. The decision to perform a fasciotomy must have a rational basis, see Compartment syndrome.

Eyes (Spitting cobras)
Naja nigricollis, N. katiensis and N. nubiae can cause lesions in the eye. Intense local pain; blepharospasm; palpebral oedema; leucorrhoea; photophobia, clouding of vision, temporary blindness (Chu et al. 2010, Warrell 2023, Warrell and Ormerod 1976; WHO 201a).

Non-clottable blood and bleeding

Even coagulation disorders that are severe according to laboratory tests may only be clinically apparent to a slight degree, or not at all. There is a threat of spontaneous haemorrhage with extensive loss of blood or focal bleeding (e.g. intracranial) as long as the haemostatic defect exists (untreated, i.e. without antivenom treatment, days to weeks).
Most typically caused by bites from carpet vipers (Echis spp.), desert horned vipers (Cerastes cerastes). More uncommonly it may sometimes follow bites by puff adders (B. arietans).

Thrombotic microangiopathy (TMA)

Is observed in the region, e.g. in Echis sp. and Daboia palaestinae envenoming.

Descending paralysis / Respiratory failure

Neurotoxic cobras Naja haje, N. anchietae, N. annulifera, N. melanoleuca.
Walterinnesia sp. ?

Acute kidney injury (AKI)

According to the available data, acute renal failure following a snakebite in North Africa and the Near and Middle East generally appears to be a secondary effect (arterial hypotension, shock, DIC).
For Bitis arietans and Cerastes cerastes venom a primary nephrogenic effect is discussed (Warrell et al. 1975, Schneemann et al. 2004).

Monitoring for signs and symptoms that would indicate systemic envenoming for at least 24h. 

At least hourly

• state of consciousness,
• ptosis,
• heart rate and rhythm,
• blood pressure,
• respiratory rate,
• bleeding,
• local swelling,
• other newly appearing signs and symptoms.

6-hourly (or more frequently if there is cause for suspicion)

• 20WBCT (bedside test),
• labortaory-based clotting tests (see above),
• CK, GOT (AST),
• urine output.

The absence of signs of envenoming in the first hours after the bite does not exclude the possibility that a relevant injection of venom has taken place. There may be a long delay before systemic signs of envenoming develop. Moreover, the continued absorption of venom from the region around the site of the bite can lead to renewed symptoms of systemic envenoming even after successful administration of antivenom (e.g correction of the haemostatic defect).