I would like to thank Oti et al [1] for the interesting case report about the use of Intralipid for unconsciousness after a mixed overdose.

This novel use of Intralipid is based on a chance observation of apparent bupivacaine-induced cardiac arrhythmias during tumescent liposuction in a patient with isovaleric acidemia and carnitine deficiency [2-3]. Fatty acid transport into mitochondria is dependent on carnitine. In the heart, this process is essential to the maintenance of normal oxidative phosphorylation and energy generation. An experiment provoked by the above case, assessed the effect of lipid supplementation on bupivacaine-induced arrhythmias in a rat model. Surprisingly, this experiment demonstrated that treatment with 30% lipid emulsion after cardiac arrest resulted in a significant rightward shift in the dose–response curve, indicating that this therapy was efficacious.

Whether lipid therapy works by providing an energy substrate to the myocardium, or provides a more lipid-rich environment in the vascular compartment, with consequent reduction of tissue distribution of lipophilic medications, is still unknown.

The human experience with lipid resuscitation is impressive, although sporadic. Multiple case reports tout its efficacy even after prolonged periods of resuscitation. However, these reports are anecdotal in nature and a certain amount of publication bias must exist, with unsuccessful cases not being reported. Thus, at the present time it is unknown whether lipid resuscitation is truly beneficial in the real world of human cardiac arrest.

The Resuscitation Council of the United Kingdom published guidelines in July 2008 endorsing lipid therapy for the treatment of cardiac arrest or cardiovascular collapse caused by local anaesthetic toxicity [4]. Similarly, in 2007, the Association of Anaesthetists of Great Britain and Ireland published guidelines for its use [5]. Despite these guidelines, presently there is no consensus in the critical care or medical toxicology community regarding the benefit of lipid resuscitation for the treatment of cardiac arrest by cardiotoxic agents such as tricyclic antidepressants, beta-receptor blockers, or calcium channel antagonists

The current state of knowledge dictates that the initial approaches to patients with cardiac arrest due to cardiotoxic drugs follow standard resuscitation guidelines. However, in the absence of expeditious and sustained resuscitation, it is reasonable to then quickly move to a trial of lipid therapy. It is fair to say that based on what we know so far, no patient dying of cardiotoxic drug poisoning should do so without a trial of lipid rescue

Ashwani Gupta, ST5

Department of Anaesthetics, Norfolk and Norwich UniversityHospital. Norwich

E-mail: ashwani_doc@yahoo.com

References

1. Oti C, Uncles D,  Sable N, Willers J. The use of Intralipid for unconsciousness after a mixed          overdose. Anaesthesia 2010 ; 65: 110-11.  

2. Brent J. Poisoned patients are different - Sometimes fat is a good thing. Critical Care Medicine 2009; 37:            1157-1158.

3. Weinberg GL, Laurito CE, Geldner P, et al; Journal of Clinical Anesthesia 1997; 9: 668–70.     

4.  http://www.resus.org.uk/pages/caLocalA.htm

5. http://www.aagbi.org/publications/guidelines/docs/la_toxicity_2010.pdf