Wilderness & Environmental Medicine

To document changes in body composition and body mass in male and female tree planters.

Height, mass, skin-fold thickness, and limb girths were measured in 17 male and 5 female tree planters before and after 10 weeks of work.

Significant decreases were found in body mass (80.6 ± 10.7 kg vs 76.8 ± 8.5 kg) and body fat (13.3% ± 5.5% vs. 10.4% ± 5.0%) in the men (P < .05). No changes in skin-fold–corrected limb girths were found in the men or women. Initial body mass was significantly (P < .05) correlated with mass loss in men (r² = .46) and women (r² = .67). Estimated daily energy consumption was 20680.1 ± 2204.5 kJ for men and 14516.6 ± 2077.3 kJ for women, and estimated daily fat consumption was 194.2 ± 30.1 g for men and 132.3 ± 35.6 g for women.

Ten weeks of tree planting leads to significant decreases in body mass and body fat in men while maintaining skin-fold–corrected limb girths.

Over 2 million adolescents participate in summer-camp experiences, placing themselves at risk for mosquito-borne illness. Insect repellent is recommended but often not used. It is unknown whether permethrin treatment of a location, such as a campsite, provides passive prophylaxis reducing mosquito bites among all persons in the immediate vicinity.

This randomized, double-blind controlled trial used 0.4% permethrin (2.5% permethrin diluted by 7 parts water) sprayed once onto the external surface of canvas tents at a Boy Scout summer camp. During a 9-week period, subjects (n = 545) completed nightly mosquito-bite and -landing counts for 5 minutes at dusk and recorded insect-repellent use within 2 hours of counting. Weekly mosquito sampling with CO₂-baited Centers for Disease Control and Prevention traps occurred at study campsites. The primary outcome measure was the number of mosquito bites per 5 minutes.

A total of 1614 person nights averaged 5.1 ± 7.2 (±SD) mosquito bites per 5 minutes. The permethrin-treated campsites had decreased mosquito landings and bites (relative risk reduction [RRR] 44%; 95% CI 34% to 55%; P < .001) compared with controls. Insect repellent was used only 32% of nights, decreasing bites by 36% (RRR 36%; 95% CI 25% to 47%; P < .001). Permethrin was superior to insect repellent alone (RRR 20%; 95% CI 4% to 37%; P = .01).

Permethrin treatment of tents is an effective, inexpensive public health measure to reduce mosquito bites. Permethrin is effective among all individuals in a camping setting and was more effective than topical insect repellent alone, which, although recommended, was inconsistently used.

To determine whether volunteers (with or without prior medical training) can correctly apply pressure immobilization (PI) in a simulated snakebite scenario after receiving standard instructions describing the technique.

Twenty emergency medicine physicians (residents and attendings) and 20 lay volunteers without prior formal medical training were given standard printed instructions describing the application of PI for field management of snakebite. They were then supplied with appropriate materials and asked to apply the technique five separate times (twice to another individual [one upper and one lower extremity] and three times to themselves [nondominant upper extremity, dominant upper extremity, and one lower extremity]). Successful application was defined a priori by four criteria previously published in the literature: wrap begins at the bite site, entire extremity is wrapped, splint or sling is applied, and pressures under the dressing are between 40 and 70 mm Hg in upper-extremity application and between 55 and 70 mm Hg in lower-extremity use. Pressures were determined using a specially designed skin interface pressure-measuring device placed at the simulated bite site.

The technique was correctly applied as judged by the preset criteria in only 13 out of 100 applications by emergency medicine physicians and in only 5 out of 100 applications by lay people. There was no significant difference in success rates between physicians and lay volunteers. Likewise, there was no significant difference in success based on which extremity was being wrapped. More detailed analysis revealed that the major contributor to failure was inability to achieve recommended target pressures.

Volunteers in a simulated snakebite scenario have difficulty applying PI correctly, as defined in the literature. The major source of failure is an inability to achieve recommended pressure levels under the dressing. New methods of instructing people in the proper use of PI or new technologies to guide or automate application are needed if this technique is to be used consistently in an effective manner for field management of bites by venomous snakes not known to cause significant local wound necrosis.

To determine the effects of hypoxia and hypoxic exercise (HE) on the norepinephrine levels of various tissues in rats.

Male Wistar rats were randomly assigned to 3 groups: an HE group (n = 6), a hypoxic-sedentary (HS) group (n = 6), and a normoxic-sedentary (NS) group (n = 6). The HE rats had access, ad lib, to an exercise wheel for 8 weeks. HE and HS rats were maintained in a normobaric hypoxic chamber with an Fio₂ of 16%. Norepinephrine levels were measured and compared in liver, heart, diaphragm, soleus, and gastrocnemius tissues from the 3 groups.

Liver norepinephrine levels in the HE and HS groups were significantly lower than the levels in the NS group (P < .05). No significant difference was found in liver norepinephrine levels between the HE and the HS groups. The heart norepinephrine levels in the NS group were significantly lower than the levels in the HE (P < .01) and HS groups (P < .01). In contrast, no significant differences were found in the norepinephrine levels for the diaphragm and soleus muscle among the 3 groups. The norepinephrine levels in the gastrocnemius white muscles were significantly higher in the HS group than in the HE (P < .05) and NS groups (P < .01). P < .01 represents a significant difference at the level of 1%.

This study demonstrated that hypoxia and HE both elicit a decreased sympathetic response in the liver tissue of male Wistar rats but cause an increased response in heart tissue. These results suggest that the sympathetic responses to long-term hypoxia and HE training are different in various rat tissues.

Glacial sports continue to be a popular form of wilderness activity, but no published studies have commented on this type of sport or focused on the injury patterns of glacial accidents. The objectives of this study were to investigate the types and frequency of injuries associated with a glacial-crevasse or ice-field fall.

The trauma registry data and radiology record system of a pediatric and adult level 1 trauma center were evaluated from January 1997 through August 2003. All admissions with injuries caused by a glacial-crevasse or ice-field fall were reviewed.

During the 5½-year period we identified 12 patients, of whom 9 (75%) were male. The average age was 30.2 years with an age range of 9 to 57 years. Six patients fell into glacial crevasses, and the other 6 slid down an ice field of a glacier. Leading diagnoses were head injury (44.6%), thorax injury (20.1%), and lower extremity injury (18.4%). Serious injuries were observed in 66.6% of the patients with a Glasgow Coma Scale of 3 to 8.

A wide spectrum of injuries is associated with glacial accidents. They range from common extremity injuries with fracture or joint instability and peripheral frostbite to potentially life-threatening nonorthopedic trauma, which requires intensive clinical and radiological work-up. Injury prevention strategies should focus on wearing helmets to reduce head injuries and adequate clothing to forestall or prevent hypothermia, for these are the most severe and life-threatening injuries.

Physicians practicing in remote areas are typically limited in their choice of diagnostic tools. The goal of this study was to determine whether the use of a portable ultrasound (US) device on selected patients in a remote setting would alter physician diagnosis and management.

This was a prospective observational study of the affects of US on physician decision making deep in the Amazon jungle. A battery-operated Sonosite 180 Plus with 2 interchangeable transducers (4–7-MHz broadband intercavitary transducer and 2–5-MHz broadband abdominal transducer) was used. The patient population consisted of local tribal people. Two of the physicians on the team performed all US examinations. Team physicians requesting US examinations filled out a survey before and after the US examination. Before the US, the referring physician filled out a survey describing the patient's initial complaint, pertinent past medical history and physical findings, and an initial (pre-US) differential diagnosis and planned treatment with expected disposition. After the results of the US were reviewed with the referring physicians, the doctors were asked to fill out the remainder of the survey, allowing comparison of pre- and post-US differential diagnosis, treatment plan, and disposition.

A total of 25 US studies were performed during this study (1 trauma US scan, 6 hepatobiliary studies, 5 transabdominal pelvic scans, 7 transvaginal pelvic studies, 3 renal studies, and 3 abdominal aortic scans). The monitor on the US unit experienced a rare failure shortly after being used at 17,000 ft and then 10 times at sea level, and no further US scans could be performed. US scan results dramatically altered the disposition of 7 patients, including 4 patients who avoided a potentially dangerous 2-day evacuation to more definitive medical care. Three patients were found to need rapid referral to the nearest clinic for surgical evaluation.

When used in a remote location, portable US provides a significant benefit that can dramatically alter disposition and treatment.

To establish a simple measure of ataxia for use at high altitude.

Twenty healthy subjects took part in a trek to 5005 m. At 5 different altitudes on the route, they undertook a balance test using a wobble board. The primary objectives were to investigate disturbances of ataxia at altitude and to correlate any observed disturbances with acute mountain sickness (AMS) scores. Secondary outcomes were correlations with cerebral regional oxygenation, pulse oximetry, and age.

After a short learning curve, the wobble board test was found to be reproducible. Subjects over 31 years of age were significantly less steady than younger subjects. Subjects suffering acute mountain sickness scored significantly worse on the wobble board test, although scores did not correlate with a specific question on unsteadiness. A positive test defined as equal to or more than 2.5 contacts over 2 minutes gave a predictive value for acute mountain sickness of 66.7% at 4650 m and 100% at 5005 m. Cerebral regional oxygenation in 9 subjects at 5005 m correlated with the wobble board test (r = 0.73; p < .05), whereas pulse oximetry did not.

The wobble board may be a useful adjunct in quantitating ataxia in the field. A positive result may indicate the presence of AMS and may be a useful clinical measure of cerebral hypoxia but should be correlated with other clinical features.