Optic Nerve Sheath Diameter Increase on Ascent to High Altitude: Correlation With Acute Mountain Sickness.

OBJECTIVES: Elevated optic nerve sheath diameter on sonography is known to correlate with increased intracranial pressure and is observed in acute mountain sickness. This study aimed to determine whether optic nerve sheath diameter changes on ascent to high altitude are associated with acute mountain sickness incidence. METHODS: Eighty-six healthy adults enrolled at 1240 m (4100 ft), drove to 3545 m (11,700 ft) and then hiked to and slept at 3810 m (12,500 ft). Lake Louise Questionnaire scores and optic nerve sheath diameter measurements were taken before, the evening of, and the morning after ascent. RESULTS: The incidence of acute mountain sickness was 55.8%, with a mean Lake Louise Questionnaire score ± SD of 3.81 ± 2.5. The mean maximum optic nerve sheath diameter increased on ascent from 5.58 ± 0.79 to 6.13 ± 0.73 mm, a difference of 0.91 ± 0.55 mm (P = .09). Optic nerve sheath diameter increased at high altitude regardless of acute mountain sickness diagnosis; however, compared to baseline values, we observed a significant increase in diameter only in those with a diagnosis of acute mountain sickness (0.57 ± 0.77 versus 0.21 ± 0.76 mm; P = .04). This change from baseline, or Δ optic nerve sheath diameter, was associated with twice the odds of developing acute mountain sickness (95% confidence interval, 1.08-3.93). CONCLUSIONS: The mean optic nerve sheath diameter increased on ascent to high altitude compared to baseline values, but not to a statistically significant degree. The magnitude of the observed Δ optic nerve sheath diameter was positively associated with acute mountain sickness diagnosis. No such significant association was found between acute mountain sickness and diameter elevation above standard cutoff values, limiting the utility of sonography as a diagnostic tool.

Prehospital medical care and the National Ski Patrol: how does outdoor emergency care compare to traditional EMS training?

OBJECTIVE: The purpose of this study was to identify the differences between the educational curricula, skill sets, and funds of knowledge required for certification as an Outdoor Emergency Care Technician (OEC-T), Emergency Medical Technician (EMT), and Emergency Medical Responder (EMR). METHODS: We directly and in detail compared topics and skills presented in the OEC-T curriculum with those presented in the EMT and EMR education and training curricula. RESULTS: The information and skills taught in the OEC-T curriculum are in general more extensive than those taught in EMR training but are not equivalent to EMT. The OEC-T program has more depth in environmental medical issues, such as altitude illness, hyperthermia and hypothermia. Completion of the EMR program is 112 hours shorter and constitutes 30% of the duration of the EMT program. Completion of the OEC-T program (for certification only and not including additional "on-hill" patroller training) is 80 hours shorter and is half the duration of the EMT program. CONCLUSIONS: The OEC-T curriculum includes a skill set and fund of knowledge that exceeds those of the EMR program, but does not include all the knowledge needed for an EMT program. The OEC-T program prepares out-of-hospital providers to care for patients in the wilderness, with special emphasis on snowsports pathology. The EMT program places a greater emphasis on medical disease and emergency medication administration. These differences should be considered when determining staffing requirements for agencies caring for patients with snowsports pathology.

Ibuprofen prevents altitude illness: a randomized controlled trial for prevention of altitude illness with nonsteroidal anti-inflammatories.

STUDY OBJECTIVE: Acute mountain sickness occurs in more than 25% of the tens of millions of people who travel to high altitude each year. Previous studies on chemoprophylaxis with nonsteroidal anti-inflammatory drugs are limited in their ability to determine efficacy. We compare ibuprofen versus placebo in the prevention of acute mountain sickness incidence and severity on ascent from low to high altitude. METHODS: Healthy adult volunteers living at low altitude were randomized to ibuprofen 600 mg or placebo 3 times daily, starting 6 hours before ascent from 1,240 m (4,100 ft) to 3,810 m (12,570 ft) during July and August 2010 in the White Mountains of California. The main outcome measures were acute mountain sickness incidence and severity, measured by the Lake Louise Questionnaire acute mountain sickness score with a diagnosis of ≥ 3 with headache and 1 other symptom. RESULTS: Eighty-six participants completed the study; 44 (51%) received ibuprofen and 42 (49%) placebo. There were no differences in demographic characteristics between the 2 groups. Fewer participants in the ibuprofen group (43%) developed acute mountain sickness compared with those receiving placebo (69%) (odds ratio 0.3, 95% confidence interval 0.1 to 0.8; number needed to treat 3.9, 95% confidence interval 2 to 33). The acute mountain sickness severity was higher in the placebo group (4.4 [SD 2.6]) than individuals receiving ibuprofen (3.2 [SD 2.4]) (mean difference 0.9%; 95% confidence interval 0.3% to 3.0%). CONCLUSION: Compared with placebo, ibuprofen was effective in reducing the incidence of acute mountain sickness.