An electrocardiogram, chest radiograph and blood tests were ordered including arterial blood gas analysis. Results showed that the patient was in atrial fibrillation, and a serum potassium level of 2.7 mmols/litre. Cardiac markers and arterial blood gases were within the normal range. Other than hypokalaemia, electrolytes were normal including renal function. Baseline thyroid functions were ordered which showed T4, T3 and TSH within the normal range.

     The patient had the powder from his skin thoroughly washed off in the emergency department and he was transferred to the intensive care unit for monitoring and correction of the potassium level; this was achieved with intravenous potassium administration over the course of the next 2-3 hours.  The atrial fibrillation reverted spontaneously to a sinus rhythm of 70/minute after 2 hours at which time the serum potassium was 3.9 mmols/litre.  Observation and monitoring were continued overnight and the patient transferred to the medical ward where he remained stable; cardiology and dermatology consults were obtained.  The skin condition was managed, but no cause for the atrial fibrillation other than hypokalemia was identified.  Feeling well, the patient discharged himself later that day.  He agreed to an internal medicine follow up appointment a week later at which biochemistry showed normal electrolytes and renal function. The patient had had no further symptoms, and was discharged from follow-up with instructions to return should he experience any complaints.  The patient did not have cause to visit the hospital again for the same problem.

     Facilities for measuring blood levels of permethrin were not available in the hospital and these were therefore not known. Due to the spatial sequence of events it was presumed that dermal absorption of permethrin from a raw skin surface led to systemic toxicity culminating in hypokalemia induced atrial fibrillation.

Discussion 

     "Piff-Paff" powder is one form of many types of insecticides that contain the class of substances known as pyrethroids, permethrin being one of these; it exists in two isomeric forms.  Permethrin itself is also used in medical practice and most physicians will be familiar with the 1% creams used for pediculosis and the 5% creams used for treating scabies.  "Piff-Paff" powder contains permethrin at a strength of 0.5%, the remainder being accounted for by an inert vehicle.

     In insects, permethrin acts as a neurotoxin by depolarising  nerve cell membranes by its action on the sodium channels.  Although pyrethroids are widely used in agriculture, relatively few reports of systemic poisoning in humans exist (1) and the major part of toxicological knowledge on them comes from data derived from animal studies.

     Pyrethroids can cause neurotoxic symptoms and skin irritation (2).  Rats fed high doses of permethrin demonstrate tremors, salivation, hyperactivity and hyperexcitability.  Additionally in humans it can cause numbing, tingling and burning sensations of the skin which is reversible and usually settles within 12 hours (3) . In one review (4) of ingestions of insecticides containing permethrin, 33% of patients exhibited central nervous system involvement including seizures, and 7% had cardiovascular involvement including arrhythmias and shock, in addition to involvement of other body organs.  Whether acute toxicity leads to hypokalemia and with what frequency is not documented in humans, and toxicity in animals is very species dependent; mammals and birds are less prone and fish species are extremely sensitive.  Acute systemic toxicity also depends on the ratio of isomers present in the formulation(5) ; the cis-isomer is more toxic than the trans-isomer as it is cleared  more slowly(6) .  However, there has not been a report of such systemic poisoning leading to an arrhythmia from transdermal absorption of permethrin.  Although systemic absorption of 5% creams used for scabies results in only 0.5% of the total dose being absorbed (7) , it is possible that in abraded skin the amount absorbed may be higher leading to toxic effects, but this has not been studied in humans. 

     Although treatment of systemic poisoning with insecticides is generally supportive (8), this case highlights the importance of early identification that toxicity may have occurred and treatment of manifestations.  As far as the author is aware, this is the only such case to have been reported in the medical literature and welcomes any comments from other clinicians who may have experienced similar cases.

1.  Ray DE, Forshaw PJ. Pyrethroid insecticides: poisoning syndromes, synergies, and therapy. J Toxicol Clin Toxicol. 2000; 38(2): 95-101

2.  Schulze M, et al  Pyrethroid exposure following indoor treatments with a dog flea powder (article in  German) Dtsch Med Wochenschr. 2002 Mar 22; 127(12): 616-8

3.  Permethrin fact sheet  National Pesticide Telecommunications Network, Oregon State University Reviewed September 1997

4.  Yang PY, et al Acute ingestion poisoning with insecticide formulations containing the pyrethroid permethrin, xylene, and surfactant: a review of 48 cases  J Toxicol Clin Toxicol. 2002; 40(2): 107-13

5.  Kid H, and James DR, Eds. The Agrochemicals Handbook, Third Edition. The Royal     Society of Chemistry Information Services, Cambridge,UK 1991 ( as updated). 2-13

6.  Gotoh Y, et al  Permethrin emulsion ingestion: clinical manifestations and clearance of isomers  J Toxicol Clin Toxicol. 1998; 36(1-2): 57-61

7.  van der Rhee HJ, Farquhar JA, Vermeulen NP  Efficacy and transdermal absorption of permethrin in scabies patients Acta Derm Venereol. 1989; 69(2): 170-3

8.  Peter JV, Cherian AM  Organic insecticides.  Anaesth Intensive Care. 2000 Feb; 28(1): 11-21