REPLY
The Physiologic Basis of High-Altitude Diseases
John B. West, MD, PhD
5 April 2005 | Volume 142 Issue 7 | Page 592
IN RESPONSE:
All 3 letters make useful points.
In my article, I inserted the statement "Gingko biloba has been suggested as a useful prophylactic agent but has not been sufficiently studied" because there are several conflicting published reports, as noted by Gertsch and colleagues (1). However, I agree with Basnyat that their randomized, double-blind, placebo-controlled study is strong evidence against the value of gingko for the prevention of acute mountain sickness.
I also agree with Pandit that there is compelling evidence that alveolar fluid clearance in pulmonary edema is assisted by the sodium–potassium ATPase pump, and this might well have been referred to in the review. However, in my defense, it seems likely that the initial events in the pathogenesis of high-altitude pulmonary edema are the increased pulmonary vascular pressures leading to stress failure of pulmonary capillaries, as set out in the review. It is not necessary to invoke defective alveolar fluid clearance in the initial mechanism. The convincing study showing the prophylactic effects of inhalation of the ß-adrenergic agonist salmeterol on the incidence of high-altitude pulmonary edema (2) is consistent with the fact that stimulation of the sodium–potassium ATPase pump helps to remove alveolar fluid but does not prove that this is a factor in the initial pathogenesis of the condition.
Matiram Pun, who must be an exceptional third-year medical student, argues that the review should have said more about focal neurologic deficits at high altitude. Again in my defense, the review stated that "patients may have papilledema and occasionally focal neurologic signs affecting cranial nerves, or even hemiparesis." Certainly, however, the review could have cited one of the recent articles on this subject, such as that by Basnyat and colleagues (3). Possible genetic factors involved in high-altitude illnesses are a topic of interest but so far are mainly speculative. The possible role of vascular endothelial growth factor in high-altitude pulmonary edema is the subject of a very recent article (4).
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Author and Article Information
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From University of California, San Diego, La Jolla, CA 92093-0623.
1. Gertsch JH, Basnyat B, Johnson EW, Onopa J, Holck PS. Randomised, double blind, placebo controlled comparison of ginkgo biloba and acetazolamide for prevention of acute mountain sickness among Himalayan trekkers: the prevention of high altitude illness trial (PHAIT). BMJ. 2004;328:797 [PMID: 15070635].[Abstract/Free Full Text]
2. Sartori C, Allemann Y, Duplain H, Lepori M, Egli M, Lipp E, et al. Salmeterol for the prevention of high-altitude pulmonary edema. N Engl J Med. 2002;346:1631-6. [PMID: 12023995].[Abstract/Free Full Text]
3. Basnyat B, Wu T, Gertsch JH. Neurological conditions at altitude that fall outside the usual definition of altitude sickness. High Alt Med Biol. 2004;5:171-9. [PMID: 15265338].[Medline]
4. Kaner RJ, Crystal RG. Pathogenesis of high altitude pulmonary edema: does alveolar epithelial lining fluid vascular endothelial growth factor exacerbate capillary leak? High Alt Med Biol. 2004;5:399-409. [PMID: 15671629].[Medline]
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