Sublingual glyceryl trinitrate as prehospital treatment for hypertension in Irukandji syndrome

To the Editor: We are concerned that a recent report announced that the Queensland Ambulance Service now treats patients with hypertension caused by Irukandji syndrome with sublingual glyceryl trinitrate, based on an uncontrolled, unrandomised, unblinded “trial” of three patients.1 We believe the authors have made the justification for such treatment on questionable assumptions.

The authors claim that venom from Carukia barnesi is a sodium channel agonist that causes massive noradrenaline release. This claim is based on a letter which reported whole C. barnesi being crudely blended and injected into piglets.2 There is no mention in this letter of any proven sodium channel agonist action.2 We are unconvinced that it was solely the venom of the jellyfish that resulted in a rise in noradrenaline levels in the piglets, especially since there has been a recent report of toxicity from homogenised jellyfish with the nematocysts (ie, venom) removed.3

While we believe that magnesium may be a promising treatment for patients with Irukandji syndrome, there has only been one case reported,4 and we are aware of several anecdotal failures, including the first patient in the letter by Fenner and Lewin.1 This does not constitute the justification for “proven effective treatment”.

Fenner and Lewin claim that patients were envenomed by Carukia barnesi and yet provide no evidence. Carukia barnesi has yet to be discovered or reported south of Townsville. Two of us have reported that more than one jellyfish is responsible for Irukandji syndrome, and a second jellyfish has recently been identified.5 Accurate identification of the envenoming animal is essential in toxinology.

Patients who present with Irukandji syndrome are in severe pain, and pain is a well known cause of hypertension. In a series of 116 patients with Irukandji syndrome, the mean dose of morphine administered was 31 mg.6 In the three patients reported by Fenner and Lewin, all were in severe pain, but only received 10 mg of morphine. In light of subtherapeutic analgesia, attributing the persistent hypertension solely to an unmanageable disease process is therefore premature and possibly incorrect. As a further confounder, might the reduction of blood pressure in two patients have resulted from the delayed onset of action of intramuscular morphine and promethazine? Without the addition of control patients to this trial, no conclusions can be drawn on the causative factors associated with this treatment.

Too often in the past, unsupported treatments have been adopted, only to be abandoned several years later when shown to be ineffectual, or even dangerous to patients. There are too many assumptions, unsupported claims and confounders in Fenner and Lewin’s letter. Toxinology research needs good science and not poor anecdotes.