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Existing Evidence Does Not Support the Use of Hexafluorine

We appreciate the interest by the Prevor Group (Hall, Blomet, Mathieu) (1) in our article on topical treatments for hydrofluoric acid (HF) burns (2), although we feel concerned with the commercial promotion of Hexafluorine—after all, the authors represent the manufacturer (3–5). They begin their letter by implying that if an issue is investigated repeatedly, one study may sooner or later report negative results. This comment is irrelevant, as proper scientific documentation of Hexafluorine was practically nonexistant prior to our study. A Medline search in May 2003 results in three hits only. One of these references is a compilation of uncontrolled cases conducted mainly by the manufacturer (4), another is a letter questioning that paper (6), and the third is our blind controlled experimental study (2). Furthermore, we do not agree with the use of the word ‘‘negative’’ in this context. In the scientific vocabulary, a negative result generally represents a lack of statistical significance. The mentioned ‘‘weight-of-theevidence approach’’ fails to demonstrate any superior efficacy of Hexafluorine in comparison with water. Moreover, since Hexafluorine is an expensive product and the only controlled and peer reviewed study so far shows that Hexafluorine is significantly less effective than decontamination with water rinsing plus topical calcium and at the most is equally effective to water rinsing (2), it does not seem justified to recommend it. Hall and coauthors question our animal model, especially the 3-min contact duration of the 50% HF. The aim of our injury model was to create a reproducible burn, severe enough to be measurable despite early rinsing, but yet not too severe to be inaccessible to any treatment. After testing for different durations of exposure, a burn model well in accordance with methods used in previously published experimental studies on HF (7–11) was established. A shorter duration of exposure than 3min followed by water rinsing resulted in too mild on burns to be accurately measured. The same experience has been reported by several other independent investigators: Murao M, rat model, 20% and 50% HF, 5-min exposure (7); Yasuda et al., rat model, 23% and 46% HF, 3-min exposure (8); Bracken et al., rat model, 70% HF, 1-min exposure (9); Burkhart et al., rabbit model, 36% HF, 3-min exposure (10); and Dunn et al., pig model, 38% HF, 3-min exposure (11). In summary, a shorter exposure than 3min of 50% HF is simply too short to get a reproducible burn if the HF is washed away with water after the exposure. On sound, scientific grounds it is not possible to rely on the preliminary, owner-performed and unpublished data which the Prevor Group is repeatedly referring to. Moreover, the Prevor Group writes that it would be highly unlikely that any decontamination measure would be efficacious after a 3-min contact duration of 50% HF, and that what we actually studied was treatment with topical calcium gluconate. Again, this statement is incorrect. The rats in the control group in our study received the same HF exposure as the other animals, but did not receive any rinsing decontamination or topical calcium. This resulted in very severe burns rated as 5, i.e., maximum severity, on the scoring scale used. The animals that were treated with water rinsing had an average score well below 3 (p< 0.001) (2). It is remarkable that the Prevor Group now focuses on the ‘‘3-minute issue,’’ since they recently have stated that: ‘‘In three cases of exposure to dilute HF reported here, even delayed decontamination with Hexafluorine allowed prevention of chemical burns’’ (12) and ‘‘Hexafluorine is hypertonic and can thus osmotically recover a portion of the HF which penetrated into the tissues’’ (4).