Acute mountain sickness and acetazolamide. Clinical efficacy and effect on ventilation
E. B. Larson, R. C. Roach, R. B. Schoene and T. F. Hornbein
Sixty-four climbers participated in a randomized clinical trial of
acetazolamide prophylaxis for acute mountain sickness (AMS) during rapid,
active ascent of MT Rainier. Twenty-nine (93.6%) of 31 climbers receiving
acetazolamide and 25 (75.8%) of 33 receiving placebo attained the summit.
Time spent ascending from sea level to the summit (4,394 m) averaged 33.5
hours (range, 23 to 48 hours). On the summit AMS was less common in
climbers receiving acetazolamide, and they experienced less headache,
nausea, drowsiness, shortness of breath, and dizziness and a greater sense
of satisfaction and psychological well-being. Minute ventilation on the
summit was significantly greater in subjects taking acetazolamide (24.9 +/-
2.0 L/min compared with 16.9 +/- 3.8 L/min). Expired vital capacity was
also greater on the summit in the acetazolamide group (6.9 +/- 0.4 L
compared with 5.8 +/- 0.4 L). We conclude that acetazolamide is effective
in the prophylaxis of AMS for climbers attempting rapid, active ascent.
Increased ventilation at altitude, producing an increased alveolar oxygen
tension, may be related to the observed amelioration of symptoms.
