Journal of wilderness medicine最新文献

Objective

Acetazolamide, a carbonic anhydrase inhibitor, is often used as a prophylactic drug for acute mountain sickness. It may interfere with erythropoietin production due to its action on ventilation and renal function.

Design

A randomized, double-blind, placebo-controlled trial with 2 × 250 mg acetazolamide daily beginning one day before ascent from 590 m to 4559 m.

Setting

High-altitude research facilities at the Capanna Regina Margherita (Italy) at an altitude of 4559 m.

Participants

Eighteen healthy volunteers, aged 24–42 years.

Main outcome measure: Plasma erythropoietin was measured by radioimmunoassay before and after the ascent.

Results

The increase of erythropoietin at high altitude was smaller in the acetazolamide group (increase by 10.8 ± 7.8 U/L or 58%) than in the placebo group (increase by 22.7 ± 13.8 U/L or 113%, p < .01).

Conclusion

Acetazolamide reduces the erythropoietin response to hypoxia in humans, which might also have therapeutic implications in conditions such as secondary polycythemia.

The brown recluse spider (Loxosceles reclusa) is a common inhabitant of the central United States. Loxoceles envenomation is a cause of significant medical problems, causing a necrotic skin lesion that often becomes a problem wound. Treatment of the skin lesion is controversial, with no current widely accepted therapy. The effects of treatment with hyperbaric oxygen or dapsone on brown spider bites were studied using guinea pigs. Progression and healing of experimental brown spider bites were measured in animals treated or pretreated with dapsone or hyperbaric oxygen and in controls. There was a significant decrease in lesion size in animals pretreated with hyperbaric oxygen at days 3,5, and 6 as compared to dapsone-pretreated animals or untreated controls. However, there were no differences noted between groups when treatment was begun 36 h after envenomation. There was a nonsignificant increase (p = 0.12) noted in myeloperoxidase levels from lesions of animals pretreated with hyperbaric oxygen. No other differences in levels of catalase, glutathione, or superoxide dismutase activity were noted between treatment groups. These results suggest that hyperbaric oxygen may have potential in the treatment of brown spider bites; however, further study is necessary to prove its efficacy.

Improved tissue survival after frostbite injury has been demonstrated with immediate postinjury use of a thromboxane inhibitor. However, most patients with frostbite injury present to the hospital hours after their injury and the efficacy of thromboxane inhibition at that time is unknown. The current study evaluated the efficacy of a thromboxane inhibitor on frostbite tissue survival when initiated at the time of injury compared to 4 h postinjury. In a prospective study, three groups of nine rabbits received a standardized frostbite injury using a modified Weatherley–White model. A control group received no pharmacologic therapy; the other two groups were treated with 1 mg kg⁻¹ methimazole initiated orally immediately or 4 h postinjury, respectively. Treatment was given every 8 h for a total of 96 h. Healing was followed until a clear line of demarcation was apparent (10 days). The percentage of viable ear surface area remaining at the end of the study was measured and used to compare the effectiveness of treatments. Analysis of variance was used to determine statistical significance. No significant difference (p = .388) was observed among the frostbite injury of the control group and either treatment group. Thirty percent of animals did not reach the study end point secondary to an outbreak of Escherichia coli diarrhea, reducing the study power to a 33% ability to detect a 35% difference in tissue survival. Despite the reduced power, this study questions the efficacy of thromboxane inhibition in improving frostbite tissue survival, whether therapy is initiated immediately or is delayed. These data suggest that further investigation is warranted to determine the role of thromboxane inhibition in frostbite injury.

A successful expedition requires technical ability as well as the ability to get along with others. Many expeditions are unsuccessful because attention is not directed toward the dynamics between group members. Positive relationships can assist an expedition to meet its goals, and may even contribute to the safety of participants. Conscious effort to utilize the concepts of expedition behavior is underutilized by most groups. The purpose of this article is to identify characteristics of group dynamics, expedition behavior and leadership concerns for expeditions.

A number of focal neurological conditions have been described at high altitude. This report presents two cases of isolated unilateral lateral rectus palsies developing shortly after ascent to high altitude. In both cases concomitant altitude illness was not present and symptoms resolved completely within weeks to months. Possible etiologies are discussed.

Cervical spine fractures can be difficult to diagnose solely upon the patient's symptoms and physical exam. There have been several case reports of trauma patients without any of the signs or symptoms of cervical spine injury who were subsequently found on radiography to have fractures. This article presents a case report of an occult cervical spine fracture occurring in a wilderness setting and discusses the special considerations of managing wilderness trauma patients who may have an occult cervical spine injury.

Disturbed mental status (DMS) is the most obvious sign of exertional heatstroke in humans, and is one of the main complications of severe exercise heat-stress (SHS). The cause of exertional heat-stroke has been attributed to many factors such as thermoregulatory failure or impairment of muscular function. This investigation was designed to assess muscle energy metabolism in two groups of rats running at 34 °C. One group (n = 17) stopped because of DMS (SHS rats), while the other group (n = 21) stopped because of mild or moderate exercise heat-stress (MHS rats). SHS rats ran longer and had a higher final rectal temperature (T_re): 66.5 ± 4.2 °C vs 47.3 ± 3.8 °C, p <0.05 and 42.7 ± 0.12 °C vs42.2 ± 0.15 °C, p < 0.05, respectively. SHS rats also had a slower rate of change of T_re (0.054 ± 0.007 °C min⁻¹ vs 0.072 ± 0.008 °C min⁻¹) and a lower mean rate of dehydration: 0.065 ± 0.006 vs 0.084 ± 0.005% bodyweight min⁻¹, p < 0.05. There were no significant differences between the two groups for skeletal muscle concentration of high energy phosphates and glycogen, but lactate was higher in SHS than in MHS rats: 25.0 ± 6.7 vs 11.8 ± 1.6 μmoles per mg protein respectively, p <0.05. These data suggest that DMS may be linked to T_re and that there is muscular functional impairment caused by SHS.