Flowcharts | Clinic | Terrestrial Snakes

Crotalus sp. Agkistrodon sp.
Minutes (to hours)

Nausea, vomiting, abdominal pain, diarrhoea (urticaria, angio-oedema) (bronchospasm) arterial hypotension	Crotalus sp.
	Hours

	Non-cardiogenic pulmonary oedema Cerebral oedema	Generalised oedema

		Hypovolaemia/hypovolaemic shock

Cardiovascular failure

Crotalus sp. Sistrurus sp. Agkistrodon sp.
Minutes (to hours)

Local pain and swelling

Painful swelling of the regional lymph nodes

		Crotalus sp.
		Hours

		Extensive swelling

		Hypovolaemia

(Necrosis)

Crotalus sp.¹ (Agkistrodon sp.)²
< 1 hour to hours

Gingival bleeding

Bleeding from wounds remote from the site of the bite

Haematemesis, bleeding per rectum, haematuria

Systemic bleeding		Intracranial bleeding (focal neurological deficits, meningismus, coma)

Hypovolaemia/haemorrhagic shock

Cardiovascular failure	Renal failure	CNS failure

1	Oozing of blood from the bite site and ecchymosis are common. Even with severe defibrination or thrombocytopenia most patients do not develop medically significant bleeding. However, fatal bleeding complications have been reported (Lavonas et al. 2011). Crotalus sp.
2	Bleeding in very rare cases of severe envenoming.

Micrurus sp.
Crotalus scutulatus^1,2

Minutes to hours

Cranial nerve deficits (ptosis, ophthalmoplegia, dysphagia, dysarthria)
Myocomia¹

Paralysis of the skeletal musculature including the respiratory musculature

Respiratory failure

1	Myocomia Mycomia occurs in envenoming by some species of North American rattlesnakes (eg, Crotalus adamanteus, Crotalus horridus, Crotalus scutellatus, Crotalus lutosus, and Crotalus helleri) (Warrell and Willimas 2023, cit Lewis and Gutmann 2004). Crotalus sp.
2	Significant respiratory muscle involvement only described in California. Crotalus sp.

Crotalus horridus

Hours

Myalgia (at rest, with active/passive movement, upon pressure), dark urine, ECG changes

Signs of paralysis

Rhabdomyolysis

?

?¹

1	Secondary to rhabdomyolysis: see Crotalus sp.

Clinical Flowchart