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Three Part Question

After [scorpion envenomation] does the [use of antivenom] [improve outcome]?

Clinical Scenario

A woman presents to the emergency department after being stung by a scorpion, which was hiding in a bunch of bananas in her local supermarket. She is in a lot of pain and feels sick. You wonder whether she should be given an antivenom.

Search Strategy

Medline 1966-11/04 using the OVID interface
[exp Scorpions OR scorpion.mp) OR (exp Scorpion Venoms OR scorpion venom.mp OR scorpionism.mp] AND [envenoming.mp OR envenomation.mp] AND [exp Antivenins OR antivenom.mp OR exp Immunization, Passive OR serotherapy.mp OR exp Immunoglobulins, Fab] LIMIT to human AND English language.

Search Outcome

Altogether 69 papers were found, only four of which presented any comparison of treatment with or without scorpion antivenom.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Sofer S et al, 1994, Israel	Children admitted to PICU after scorpion envenomation. Comparison of 52 children given antivenom between 10 July 1885 and 1 July 1989 and 52 children treated without antivenom between 1 July 1989 and Dec 31 1992.	Cohort	Duration of PICU stay	No significant difference	Historical comparison. Children treated without antivenom may have benefitted from improved supportive care.
			Duration of hospital stay	No significant difference
			Full recovery	49 in antivenom group, 52 in control group
			Death	2 in antivenom group, 0 in control group
Belghith M et al, 1999, Tunisia	Patients participating in a study on the efficacy of high-dose hydrocortisone after scorpion sting. Matched-pair comparison of 135 patients given scorpion antivenom in addition to their trial medication.	Cohort	Clinical improvement	50% of antivenom group, 64% control group	Retrospective review of patients recruited into another trial. Results not stratified according to hydrocortisone treatment.
			Prevention of progression of symptoms	13% antivenom group, 10% control group
			Duration of hospital stay	No significant difference
			Death	1 in control group
Abroug F et al, 1999, Tunisia	825 consecutive patients aged 10 or older presenting to a non-teaching hospital emergency department	Randomised placebo-controlled trial of intravenous scorpion antivenom	Clinical improvement	55% antivenom group, 66% control group	Trial found to be underpowered to show any difference in mortality as mortality was so low.
			Prevention of symptom progression	94% in antivenom group, 96% in control group
			Hospital admission	13% in antivenom group, 9% in control group
			Duration of hospital stay	No significant difference
			Death	1 in each group
Ghalim N et al, 2000, Morocco	275 patients with scorpion envenomation, 179 of whom were treated with antivenom (IM, SC or both routes)	Prospective cohort	Effectiveness of antivenom according to sting admission interval	Antivenom more effective if sting admission interval < 1 hour	90% of patients had only grade I envenomation. No evidence that patients were randomised or that treatment was blinded. Statistical analysis of clinical features unclear. There appears to be a 50% baseline difference in incidence of systemic symptoms between the antivenom and no antivenom groups, in favour of the antivenom group.
			Local symptoms	Greater reduction in local pain and burning reported with antivenom
			Systemic symptoms	Lower incidence of systemic symptoms in the antivenom group

Comment(s)

While there are many case series and retrospective reviews in the literature suggesting that scorpion antivenom is safe and effective, there is only one RCT of this treatment. This showed no improvement in symptoms or in preventing symptom progression. There was no difference in hospital admission rate or duration of stay, and no difference in mortality. Two other studies had similar results. Only Ghalim et al found any clinical improvement and this was mainly for local symptoms. Deaths in adults are very rare and most patients have only local or mild systemic symptoms, which resolve with symptomatic treatment.

Clinical Bottom Line

In an adult who has been stung by a scorpion there is very little evidence that giving antivenom will improve clinical outcome.

Level of Evidence

Level 2 - Studies considered were neither 1 or 3.

References

1. Sofer S, Shahak E, Gueron M. Scorpion envenomation and antivenom therapy. J Pediatr 1994;124(6):973-8.
2. Belghith M, Boussarsar M, Haguiga H, et al. Efficacy of serotherapy in scorpion sting: a matched-pair study. J Toxicol Clin Toxicol 1999;37(1):51-7.
3. Abroug F, Elatrous S, Nouira S, et al. Serotherapy in scorpion envenomation: a randomised controlled trial. Lancet 1999;354(9182):906-9.
4. Ghalim N, El-Hafny B, Sebti F, et al. Scorpion envenomation and serotherapy in Morocco. Am J Trop Med Hyg 2000;62(2):277-83.