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Three Part Question

In [adult patients with local anaesthetic toxicity not in cardiac arrest] is [lipid emulsion more effective than placebo] at [preserving life]?

Clinical Scenario

A fifty-five year old male is administered a dose of local anaesthetic for an interscalene block in preparation for shoulder manipulation. Shorty after the drug is given he suffers a tonic-clonic seizure, after reading a local anaesthetic guideline recently published you question which action you should now take?

Search Strategy

Using Ovid interface; Medline 1950 to June week 4 2010, Embase 1980 to 2010 week 26, Cochrane database of systematic reviews 2005 May 2010.

[exp Anesthesia, Local/ OR (local adj1 anaesthe$).mp OR exp Anesthetics, Local/ OR exp bupivacaine$/ OR bupivacaine$.mp. OR lidocaine$/ OR lidocaine$.mp. OR exp prilocaine$/ OR prilocaine$.mp. OR exp lignocaine$/ OR lignocaine$.mp. OR exp marcaine$/ OR marcaine$.mp.] AND [exp Fat Emulsions, Intravenous/ OR IFE.mp OR intralipid.mp. OR Intravenous lipid emulsion.mp.] LIMIT to English language and humans.

Search Outcome

226 papers were found of which 3 papers were relevant and not repeated within the systematic review.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Jamaty C et al 2010 Canada	16 published and 23 unpublished human case reports of those administered with IFE for local anaesthetic toxicity. 8 of the published were not in cardiac arrest and 16 of the unpublished were not in cardiac arrest.	Systematic review	Mortality	No cases of mortality reported although evidence weak.	Incorrect analysis of results, incorrect figures in mortality result discussion. Incorrect referencing within review. Does not rate the methodological quality of case reports. Not clear what was measured in mental state discussion. Unpublished reports used of very poor quality, some incomplete.
			Electrocardiographic parameters	Reports of correcting dysaryhthmias in 9 cases.
			Mental state	14 cases of improved mental state.
			Haemodynamic parameters	9 cases reported of return to haemodynamic stability.
Espinet A et al 2009 Australia	36 year old male, 80kg, receiving IM 10ml 1% lidocaine with 1:200 000 adrenaline and 20 ml 0.5% bupivacaine for lower limb nerve block. He developed symptoms of systemic local anaesthetic toxicity. Received 2 100 ml boluses of 20% Intralipid and 100 ml given over an hour.	Case Report	Mortality and morbidity	Within first minute, heart rate fell from 153/min to 92/min, symptoms subsided. At 8 hours ECG did not show the ST elevation seen previously.	Does not contain any long term follow up.
Calenda E et al 2009 France	72 year old mal. Mix of ropivacaine (7.5mg/ml) 50% and mepivacaine (20mg/ml) 50% total of 30ml injected for an axillary plexus block. He experienced symptoms of local anaesthetic toxicity so was administered 250 ml Intralipid 20% 15 minutes after intubation.	Case report	Mortality and morbidity	Second seizure ten minutes after dose of Intralipid, controlled with 125mg thiopental. Patient well on waking.	No long term follow up reported. Guideline dose of Intralipid not used, may have been insufficient. Also used very late after onset of symptioms.

Comment(s)

The evidence is mixed on whether lipid emulsion should be given when signs of local anaesthetic toxicity are identified. The review by Jamaty C et al seems to support this, but the authors comment that the evidence presented is in fact very weak. They suggest that it should be used at the point of onset of either CNS or CVS symptoms due to lack of alternatives. Espinet A et al again supports this. Calenda E et al report that although CVS symptoms did resolve in the long term, a second seizure after the administration of Intralipid was observed. It seems that there is insufficient evidence to advocate the use of lipid emulsion in this way. More research is needed on the subject.

Clinical Bottom Line

Inconclusive evidence to support the use of intravenous lipid emulsion in those with local anaesthetic toxicity not in cardiac arrest. Continued use of conventional treatment methods advised, over the use of lipid emulsion.

References

1. Jamaty C et al Lipid emulsions in the treatment of acute poisoning: a systematic review of human and animal studies. Clin Toxicol (Phila). 2010 Jan;48(1):1-27.
2. Espinet A et al The successful use of Intralipid for treatment of local anesthetic-induced central nervous system toxicity: Some considerations for administration of Intralipid in an emergency Clin J Pain 2009 Nov-Dec;25(9):808-9.
3. Calenda E et al Failure of lipid emulsion to reverse neurotoxicity after an ultrasound-guided axillary block with ropivacaine and mepivacaine. J Anesth. 2009;23(3):472-3.