Contraindications to altitude exposure beyond 20 weeks of gestation include co-existing hypertension, preeclampsia, intrauterine growth restriction, anemia, and maternal smoking. Acetazolamide is also contraindicated in pregnant women.93 Should an extended stay at altitude be necessary for a pregnant woman, extra vigilance in the form of frequent prenatal checks is necessary to promptly identify problems that may arise.14

Little is known about the specific effects of altitude on patients with Raynaud’s phenomenon (RP). However, it is well known that patients with RP are at increased risk of cold injury. Because the high altitude environment may include extremes of cold, these patients should travel to altitude during warmer months or to high altitude destinations with less severe climates. However, should they travel in winter climates, these individuals should take extra precautions to maintain the warmth of their extremities. High Crizotinib quality boots and mittens are essential; disposable chemical handwarmers are

also recommended.120 Calcium channel blockers (eg, nifedipine) are the drugs of choice for the treatment of RP and should be considered in patients with RP who wish to participate in cold weather recreation at altitude.121–123 Patients who have undergone radial keratotomy to correct their myopia are at risk of significant visual deterioration at high altitude. The incisions made during this procedure weaken the cornea and cause Cytoskeletal Signaling inhibitor it to deform with exposure to hypoxic conditions.124 Progressive hyperopic shift with deterioration in both near and far vision has been reported in a number of mountaineers at high altitude.124–126 Patients who have undergone radial keratotomy should travel to altitude with multiple pairs of corrective spectacles with varying degrees of correction click here for hyperopia.127 Some people who have undergone myopic laser in situ keratomileusis (LASIK) also experience significant visual changes with high altitude exposure.128–130 The visual changes correct with descent to low altitude or with prolonged altitude exposure131 but

can persist for a number of weeks following descent. It is recommended that patients allow a minimum of 6 months following LASIK before traveling to altitude. Patients who have undergone myopic LASIK should carry spectacles with myopic corrective power while at altitude.128 The carotid bodies provide the stimulus for the hypoxic ventilatory response to hypoxia and thus their function is key to high altitude acclimatization and prevention of AMS.131,132 Neck irradiation or surgery involving one or both of the carotid arteries can potentially damage or ablate the carotid bodies, and thus alter or eliminate their function. Roeggla and colleagues132 analyzed blood gas samples taken at moderate altitude from four patients before and after unilateral carotid endarterectomy.