The Use of Tannic Acid in the Local Treatment of Burn Wounds: Intriguing Old and New Perspectives

Wounds. 2001;13(4) 

In This Article

Objections Raised Toward the Tannic Acid Method of Burn Treatment

The tannic acid method was widely met with enthusiasm, and it came to assume a dominating position in the treatment of burn patients. Notwithstanding, this method could not satisfy all needs and had its limitations and disadvantages as may be expected in the case of an injury that was so difficult to treat and often demanded all of the clinician's skills to arrive at a positive outcome.

First, critics pointed out that this local therapeutic regimen did not consider specific measures to improve the general conditions of patients. The significance of such a systemic treatment, in particular fluid administration, had just become apparent with the work of Underhill and co-workers[73] and Blalock.[74] These authors demonstrated that the marked concentration of blood and lowering of blood pressure were due to the local loss of fluids and favored the suggestion that symptoms encountered in severely burned patients were due to this fluid loss rather than to the action of burn toxins.[75] Although from both clinical (vide supra) and experimental data[76,77] it could have been concluded that tanning may also improve the general condition of the patient by reducing the leakage of plasma from burn wounds, it was nevertheless feared that focusing mainly on the local treatment may incur the risk of distracting the attention from other systemic measures that could be beneficial to the patient's welfare.[78] In this respect, it was even suggested that the observed drop in the mortality rate could not be solely attributed to the introduction of tannic acid treatment but should, at least in part, be ascribed to the simultaneous advances in the general care of burn patients.[49,50,52,72,79,80]

Second, it was considered inappropriate by some to apply tannic acid to burns of the hands and face.[81,82,83] When used on the hands, tannic acid would form an inelastic eschar and prevent transudation, which could lead to edema formation, compression of the circulation, and finally necrosis of fingers or deformities of the hand. Tanning of facial burns may be detrimental in that, with the multiplicity of orifices in the vicinity, it was almost impossible to avoid infection. It could furthermore immobilize the eyelids, which may result in dehydration of the eyes and, consequently, inflammation and eventual loss of sight.

Third, it was put forward that tannic acid may destroy intact epithelium and in this way could inflict further damage, so that in some instances a second-degree burn is converted into a third-degree burn. With respect to this objection, considerable evidence both for and against has accumulated. In support of the belief that tannic acid damages epithelial cells, Taylor[79] noted that the viable epithelium stopped abruptly where the coagulum began. Ham[77] found a considerable thickness of dermis to be destroyed but only when the burned surface was denuded of epidermis prior to tanning. Similarly, Hirshfeld and associates[84] reported that in fresh wounds resulting from skin grafting, the dermis was destroyed to a great depth after application of tannic acid. The same authors observed a delay in epithelial regeneration and prolonged healing time, a finding that was confirmed by others.[80,83,85] The cause for these adverse effects on skin structure is not known exactly but might be related to the high acidity of the solutions[86] or the type of tannic acid used.[87] Opposed to this, a substantial body of evidence is available to refute the opinion that tannic acid is detrimental to epithelium. From the clinic, many reports on the prosperous healing of burn wounds have been issued (vide supra). In addition, Bancroft and Rogers,[40] looking into more detail to this aspect, found healthy skin to be apparently unaffected by tannic acid treatment. In microscopic examination of biopsies taken from one case, they also saw a thin layer of flat epithelium extending from the hair follicle and spreading out over the connective tissue. Likewise, Baltin[66] found the hair follicles and glands from which reepithelization may occur to be well preserved. Anagnostidis[88] did not observe any differences between tannic acid-treated and untreated burn wounds with respect to the microscopic wound characteristics and the healing process. Finally, Von Löhr and Zacher[58] examined the ability of tannic acid to fixate dead tissue in experimental burn wounds in animals and human operation material and showed the coagulating effect to be only superficial.

Fourth, the poor antibacterial capacity was assumed to be another negative aspect because it brought with it the risk of infections to spread under the eschar, thereby inducing further tissue damage.[58,82,83,89] The picture of heavily infected burn patients with profuse discharges and dressings soaked with odorous and often green pus was sometimes referred to as the "laudable pus days"[52] and was generally seen before the introduction of tannic acid treatment. This, however, was rarely encountered, though local foci of infection remained common. Thus, it was noted that in third-degree burns, there are a certain number of patients who develop infection,[41,85] and it was demonstrated that bacteria, in particular Streptococci, were present in burn wounds.[38,90] The insufficiency of tannic acid to prevent infection became particularly evident during the Second World War. While it was advocated by the Royal Navy as a first aid measure[91] and was considered to be the proper therapy in superficial burns by other war surgeons,[82,92] in more unfavorable situations it was far from adequate. For example, Porritt[93] reporting on the desert wars in the Middle East during the "Wavell," "Auchinleck," and "Alexander-Montgomery" periods found tanning in forward areas near the war front to be depressing in the extreme: Nine out of ten patients arrived in the hospital septic and in very poor general condition, and all that could be done for them was to remove the septic eschar. However, it should be noted that these battle casualty burns were, more frequently than not, serious and usually combined with other wounds, and transportation to the hospitals took, in general, several days or even more than a week. To overcome this particular problem of infection, several authors suggested the use of combined preparations of tannic acid and antiseptics (vide supra) or advocated the use of coagulating agents other than tannic acid, such as gentian violet, which had similar protein-precipitating properties but was a more potent bactericidal.[90]

However, none of these drawbacks associated with the use of tannic acid gave cause to reconsider its use on burn wounds. They were merely the reason for slight changes in the formulation or adaptations in the method of application. It was not until the late thirties and beginning of the forties, after reports on the potential hepatotoxic effects of tannic acid started to appear, that the opinion concerning the value of tannic acid treatment underwent a dramatic change.

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