III. MANAGEMENT
The best strategy to prevent pulmonary edema is to ascend gradually to allow sufficient time for acclimatiza¬tion. Descend to a lower altitude as quickly as possible and administer a high inhaled concentration of oxygen. Simulated descent with a portable hyperbaric chamber can be lifesaving.
Prevention of pulmonary edema in people with a history of high-altitude pulmonary edema may be achieved by the use of nifedipine, a calcium antagonist that reduces pulmonary artery pressures. Slow release nifedipine 20 mg every 8 h has been shown to be effective in prevention after rapid ascent to greater than 4000 m.
Continuous positive airway pressure with a portable device is useful. Also, nifedipine 10 mg immediately, then provided that the systolic blood pressure is greater than 100 mmHg, slow-release nifedipine 20–30 mg every 12–24 h along with oxygen may be useful during descent. Nifedipine is a powerful vasodilator and antihypertensive agent that may cause severe hypotension and caution is required. The high pulmonary artery pressure is caused by hypoxemia, which must be relieved by high concentrations of inhaled oxygen.
Acetazolamide, a mild diuretic and carbonic anhy-drase inhibitor, causes elimination of bicarbonate by the kidney altering the blood pH and stimulating respiration. Acetazolamide should be commenced two days prior to a planned trip to high altitudes. The drug does not prevent high-altitude pulmonary edema, but it appears to be useful in the prevention of acute mountain sickness and for high-altitude flights. The dosage should be 250 mg twice or three times daily one day before ascent. A dose lower than 750 mg daily may be ineffective for some individuals. A combination of acetazolamide and dexamethasone 8 mg daily is more effective than either drug alone. Ginkgo biloba at a dose of 80 mg twice daily has been shown to be effective in a small study, but beneficial effects were variable in other studies in preventing acute mountain sickness.
Страницы: 1 | 2