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Chapter 16: ENVIRONMENTAL CONDITIONS

Ken Zafren; R. Jason Thurman; Ian D. Jones

INTRODUCTION

Multiple Lightning Strikes. (Photo contributor: Lawrence B. Stack, MD.)

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The authors acknowledge the special contributions of Peter Hackett, MD, The Institute for Altitude Medicine Telluride, CO; Edward Otten, MD, University of Cincinnati, Cincinnati, OH; James O’Malley, MD, Providence Alaska Medical Center, Anchorage, Alaska; Murray Hamlet, DVM, and Kathy McCue, MD, Alaska Native Medical Center, Anchorage, Alaska; Sheryl Olson, RN, Manitou Springs, CO; Luanne Freer, MD, Yellowstone National Park, The Nashville Zoo, Nashville, TN; and the Nova Scotia Museum of Natural History, Halifax, Nova Scotia, Canada. The authors thank Joseph C. Schmidt, MD, Lawrence B. Stack, MD, and Alan B. Storrow, MD, for their contributions to prior editions.

HIGH-ALTITUDE RETINAL HEMORRHAGE

Clinical Summary

Retinal hemorrhages are common above 5200 m (17,000 ft) and are not always associated with acute mountain sickness (AMS). High-altitude retinal hemorrhages (HARH) are rarely symptomatic, but if found over the macula, these hemorrhages may cause temporary blindness. The diagnosis can be established by ophthalmoscopy. Without visualization of the lesion, the differential diagnosis of unilaterally decreased vision or blindness at high altitude includes migraine equivalent, cerebrovascular accident, and dry eye (often unilateral, due to strong winds), as well as all conditions found at sea level.

Management and Disposition

HARH generally resolve spontaneously after descent to lower altitudes. No treatment is necessary for asymptomatic HARH. Patients with HARH associated with a decrease in vision should be referred to an ophthalmologist for follow-up.

Pearls

  1. Patients with blurred vision and unilateral mydriasis at the high altitude should be asked about use of medications, including transdermal scopolamine patches.

  2. As with almost all altitude-related problems, descent is the primary treatment. This is not emergent unless associated with severe altitude illness or progressive visual loss.

  3. Although most symptomatic HARH resolve completely in 2 to 8 weeks, cases of permanent paracentral scotomata have been reported.

FIGURE 16.1

High-Altitude Retinal Hemorrhage. Fundoscopic appearance of high-altitude retinal hemorrhage. (Photo contributor: Peter Hackett, MD.)

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HIGH-ALTITUDE PULMONARY EDEMA

Clinical Summary

High-altitude pulmonary edema (HAPE) is a form of noncardiogenic pulmonary edema, generally beginning within the first 2 to 4 days after ascent above 2500 m (8200 ft). The earliest symptoms are fatigue, weakness, dyspnea on exertion, and decreased exercise performance. Symptoms of Acute mountain sickness (AMS) such as headache, anorexia, and lassitude may also be present, but HAPE may develop without AMS. First symptoms usually include persistent dry cough and dyspnea followed by tachycardia, tachypnea, and cyanosis at rest. Patients suffering from HAPE often experience sudden onset of symptoms upon awakening after the second night at altitude. Eventually the victim ...

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