Abstract
To the Editor:
We thank Dr Zafren for his insightful comments and questions. We acknowledge that the Frostbite Guidelines are not an exhaustive treatise, but are recommendations from a group of subject matter experts after review of the most relevant frostbite literature. They are intended to be concise so that practitioners can access pertinent clinical and treatment information quickly and easily.
Regarding Dr Zafren's remarks on frostbite classification, our committee discussed all published frostbite classification schemes. Many authors supported the classification system based on 4 degrees of anatomical extent of injury within the skin and underlying tissues. We regretfully and erroneously cited the 4 grades presented by Cauchy 1 in this section. The panel also discussed the 4 grades presented by Cauchy and the 2-tier superficial/deep classification methods. Both the degree and grade descriptions are retrospective descriptions based on outcomes observed after rewarming and/or imaging. We describe the 4 anatomical degrees of injury to serve as a foundation when discussing specific therapies later in the article. For evaluation and treatment strategies, the expert committee consensus favored the 2-tier system that is less precise but probably more useful in a field setting. By classifying the injury as superficial or deep, the provider is guided in decisions such as the need for immediate evacuation, hospital vs field management, and consideration of advanced therapies such as thrombolysis. Dr Zafren rightly credits Mills et al 2 for suggesting this scheme decades ago, but since the expert group slightly changed the superficial definition to include the fact that some superficial injuries can include mild tissue loss, we did not directly reference the Mills definition. We thank Dr Zafren for making this point.
The frostbite prevention section is primarily expert opinion based upon years of empiric observations and experience by members of the committee, unsupported by high quality scientific studies. We agree that many wilderness medicine topics do not yet have solid scientific evidence; therefore, the American College of Chest Physicians (ACCP) evidence classification scheme is often challenging to apply. The panel discussed modifying the ACCP evidence classification scheme to accommodate this particular (eg, frostbite) limited evidence structure; however, it decided against this.
The questions raised by Dr Zafren regarding methods to maintain peripheral perfusion are rightfully the subject of a detailed chapter. We did not describe specific methods for “protecting skin from moisture, wind, and cold” because these strategies depend on numerous practical situational aspects. Stating that the main method is to “cover skin so that it is not directly exposed to the cold environment” does little to clarify. For instance, covering skin that is already wet in a severely cold and windy environment may offer scant protection. Ultimately, one must use an approach that takes into account available materials to protect skin, environmental conditions, concurrent acute and chronic medical conditions, medications, tobacco use, and nicotine-based therapies in order to satisfactorily answer this question. We encourage interested persons to seek additional information from comprehensive sources.
Recommendations given in the Frostbite Guidelines are based on many factors, in addition to strength of evidence, that include the ease of therapy and the balance of risks and benefits. Dr Zafren questions the 1C recommendation of ibuprofen and states that limited evidence supports this therapy. We agree that limited evidence exists. We are of the opinion that ibuprofen should be administered because it is easily administered in oral form, present in most mountain medical kits, harmless in the majority of patients, an effective analgesic, and has the potential to decrease prostaglandin and thromboxane production, which may ultimately improve survival of frostbitten tissue.
With regard to thrombolytic therapy, the expert panel was of the opinion that, although published data are limited, this therapy appears to offer the potential to improve morbidity from frostbite. The panel debated a 1C or 2C recommendation and, ultimately, decided on 1C with specific caveats: “Although further studies are needed to determine the absolute efficacy of tPA for frostbite injury … we recommend IV or intra-arterial tPA within 24 hours of injury as a reasonable choice in a proper facility.” This seems prudent and, as do all of the recommendations, leave the ultimate decision to the treating clinician to select the most appropriate therapies.