Emergency Flowchart

Signs and symptoms¹	Supportive emergency medical treatment	Identification of the culprit	Antivenom

	Possible culprit²

Nausea, vomiting, abdominal pain, diarrhoea, urticaria, angio-oedema, bronchospasm, arterial hypotension (autopharmacological effects of the venom, including anaphylaxis)	Treatment of anaphylactic/anaphylactoid reactions.	In North America, with regard to antivenom treatment, only crotalids and elapids (M. fulvius) need to be distinguished as the cause. Identification strategies 1. Morphological identification key (if snake is available for identification) 2. Narrowing down the cause with the aid of indirect criteria (if the snake is unavailable or could not be unequivocally identified) Which snake species are present in the country where the snake bite took place? Under what circumstances did the snake bite occur, and how did the snake behave? Syndromic approach: How does the clinical picture of snakebite envenoming develop? Comparative observations of the various species responsible in the region. Follow also links to species- and family-specific 'clinical entries' in the column `possible culprit' of this flowchart.	WHO Snakebite Information and Data Platform Check for nationally / regionally available antivenoms (assure safety and effectiveness) Antivenom indications and antivenom therapy: go to 'clinical management' Check for updates in case of an accident

	Agkistrodon sp. Crotalus sp.

Generalised oedema → hypovolaemia → hypovolaemic shock (autopharmacological effect of the venom: increased capillary permeability)	Treatment of the hypovolaemia/hypovolaemic shock

	Crotalus sp.

Extensive local swelling possibly involving the trunk → hypovolaemia → hypovolaemic shock (local effect of the venom: regionally increased capillary permeability)	Treatment of the hypovolaemia/hypovolaemic shock

	Crotalus sp.

Systemic bleeding → hypovolaemia → haemorrhagic shock (haemostatic effects of the venom) Intracranial bleeding → focal neurological deficits, coma, meningismus (haemostatic effects of the venom)	Treatment of blood loss Treatment of intracranial bleeding

	Crotalus sp.³ (Agkistrodon sp.)⁴

Cranial nerve deficits, paralysis of skeletal musculature including respiratory musculature → respiratory insufficiency, respiratory failure (neurological effects of the venom).	Treatment of respiratory insufficiency/respiratory failure. In Micrurus ssp. envenoming trial of acetylcholinesterase inhibitors

	Micrurus sp. Crotalus scutulatus⁵

Myocomia	Calcium admistration: rapid reversal

	Crotalus sp.⁶

Myalgia, pain on active/passive movement and upon pressure, ECG changes (hyperkalaemia), signs of paralysis, urine colour (differential diagnosis haemoglobinuria), renal failure (muscular effect of the venom: rhabdomyolysis)	Treatment of hyperkalaemia, prevention and treatment of acute renal failure, treatment of respiratory insufficiency/respiratory failure

	Crotalus horridus

This section contains genera and species for which clinical data is either sparse or entirely missing. In this case, the link will lead you to the biological file. Under 'Risk', you will find what is known about the potential harm to humans. which are well described for adjacent regions but not for the region you are currently looking at. The link will take you to the biological file and from there to the clinical file. When using the clinical information, however, you must consider that it is not from your region and therefore may not be applicable to your situation.	Follow the ABCDE approach

	Colubridae Micruroides eurxyanthus

1	See also Clinical flowchart as a guide to the dynamics of envenoming.
2	Taxonomic name without parentheses/(in parentheses)/((in double parentheses)): these signs and symptoms are regularly/(rarely)/((questionably)) observed following bites by these species.
3	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.
4	Bleeding in very rare cases of severe envenoming.
5	Significant respiratory muscle involvement only described in California. Crotalus sp.
6	Myocomia 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.