First-aid treatment of hydrofluoric acid skin burns with 2.5% calcium gluconate gel: an experimental controlled study

Introduction

Present in various industrial and household products, hydrofluoric acid (HF) is one of the most dangerous mineral acids. Extremely aggressive for the skin, HF is responsible for immediate tissue damage and potentially systemic complications, especially life-threatening hydro-electrolytic perturbations. Calcium gluconate in the form of a 2.5% gel is considered the first-aid treatment for accidental HF skin burns. In France, a ready-to-use form is produced and distributed to hospitals by the AGEPS. Although the use of this gel is based on clinical practice, there is no available controlled study on its efficacy.

Materials and methods

Thirty male Wistar–Han rats of 250 g were burned with 60 μl of a 40% HF aqueous solution on two spots of 4 cm² (right flank) under pentobarbital anesthesia. After a 2 min contact with HF, one lesion was treated by repeated (n = 10) topical applications of 1 g of 2.5% calcium gluconate gel for 4 days; the other one was untreated (control). The AGEPS formulation and two other alternatives were evaluated in a blind fashion (10 rats/gel). Burn severity was assessed on days 1, 2, 3, 7, 10, 14 and 17 post-injury by a visual semi-quantitative scaling system (0–4). Treatment efficacy was evaluated by comparing burn severity scores and areas under the curve (AUC) of treated and untreated lesions for each animal. Statistical analysis was performed by analysis of variance followed by the Student–Newman–Keuls test.

Results

The untreated lesion started to develop upon HF application; it reached a maximum between days 2 and 7 (median score: 3), before beginning to recover (day 17, median score: 1). Treatment significantly limited the severity of burns at all time intervals (median: -0.5 to -2) and for all scores (median: -1 for severity scores 1, 2 and 4, -2 for score 3 lesions, P < 0.0001). Treatment reduced the AUC days 1–17 of burn injury from 34.0 (untreated) to 17.7 (P < 0.001); there were only three cases of treatment failure (AUC of untreated/treated: 15/21, 53.5/58.5, 51.5/50.5). At day 17, full wound recovery was obtained in 14 cases by gel therapy compared with six cases in the absence of treatment. The efficacy of the three gel formulations was comparable (severity scores and AUC of burn injury, number of full recoveries).

Conclusion

Calcium gluconate in the form of a 2.5% gel reduces the severity of skin burns induced by 40% HF in a rat model. These data support the use of the AGEPS gel as a rapid, safe, and economical 'first-aid' treatment for accidental HF skin burns; more severe burns may require additional injection of calcium gluconate.