title: Autonomic cardiovascular regulation in subjects with acute mountain sickness. Reproducibility of Acute Mountain Sickness in Children and Adults: A Prospective Study Vascular endothelial growth factor and acute mountain sickness A randomized trial of dexamethasone and acetazolamide for acute mountain sickness prophylaxis.
abstract: The aims of this study were 1 ) to evaluate whether subjects suffering from acute mountain sickness ( AMS ) during exposure to high altitude have signs of autonomic dysfunction and 2 ) to verify whether autonomic variables at low altitude may identify subjects who are prone to develop AMS . Forty-one mountaineers were studied at 4,559-m altitude . AMS was diagnosed using the Lake Louise score , and autonomic cardiovascular function was explored using spectral analysis of R-R interval and blood pressure ( BP ) variability on 10-min resting recordings . Seventeen subjects ( 41 % ) had AMS . Subjects with AMS were older than those without AMS ( P < 0.01 ) . At high altitude , the low-frequency ( LF ) component of systolic BP variability ( LF(SBP ) ) was higher ( P = 0.02 ) and the LF component of R-R variability in normalized units ( LF(RR)NU ) was lower ( P = 0.001 ) in subjects with AMS . After 3 mo , 21 subjects ( 43 % with AMS ) repeated the evaluation at low altitude at rest and in response to a hypoxic gas mixture . LF(RR)NU was similar in the two groups at baseline and during hypoxia at low altitude but increased only in subjects without AMS at high altitude ( P < 0.001 ) and did not change between low and high altitude in subjects with AMS . Conversely , LF(SBP ) increased significantly during short-term hypoxia only in subjects with AMS , who also had higher resting BP ( P < 0.05 ) than those without AMS . Autonomic cardiovascular dysfunction accompanies AMS . Marked LF(SBP ) response to short-term hypoxia identifies AMS-prone subjects , supporting the potential role of an exaggerated individual chemoreflex vasoconstrictive response to hypoxia in the genesis of AMS OBJECTIVE : Although a history of previous acute mountain sickness ( AMS ) is commonly used for providing advice and recommending its prophylaxis during subsequent exposure , the intraindividual reproducibility of AMS during repeated high-altitude exposure has never been examined in a prospect i ve controlled study . METHODS : In 27 nonacclimatized children and 29 adults ,  AMS  was assessed during the first 48 hours after rapid ascent to 3450 m on 2 consecutive occasions 9 to 12 months apart . RESULTS : During the first exposure , 18 adults ( 62 % ) and 6 children ( 22 % ) suffered from AMS ; during the second exposure , 14 adults ( 48 % ) and 4 children ( 15 % ) suffered from this problem ( adults versus children , P ≤ .01 ) . Most importantly , the intraindividual reproducibility of AMS  was very different ( P < .001 ) between children and adults . None of the 6 children having suffered from AMS during the first exposure suffered from AMS during the second exposure , but 4 children with no AMS during the first exposure did experience this problem during the second exposure . In contrast , 14 of the 18 adults who suffered from AMS on the first occasion also presented with this problem during the second exposure , and no new case developed in those who had not experienced AMS on the first occasion . CONCLUSIONS : In adults , a history of AMS is highly predictable of the disease on subsequent exposure , whereas in children it has no predictive value . A history of AMS should not prompt practitioners to advise against reexposure to high altitude or to prescribe drugs for its prophylaxis in children Study Objective : Despite causing significant morbidity throughout the mountainous regions of the world , the pathophysiology of acute mountain sickness ( AMS ) remains poorly understood . This study aims to improve the underst and ing of altitude illness by determining if vascular endothelial growth factor ( VEGF ) plays a role in the development of AMS . The purpose of this study was to determine if elevated plasma VEGF correlates with increased symptoms of AMS at high altitude . Patients and Methods : This is a prospect i ve study of a cohort of healthy climbers on Denali ( Mount McKinley ) in Alaska at 14 , 200 feet . Baseline demographics , medications , rates of ascent , and AMS scores were recorded .  Pulse oximetry measurements and venous blood sample s were obtained . Comparisons were made between mountaineers with and without AMS . Results : Seventy-two climbers were approached for participation in the study ; 21 ( 29 % ) refused . Of the 51 climbers participating in the study , 14 subjects ( 27.5 % ) had symptoms of AMS and 37 subjects ( 72.5 % ) were free of symptoms of AMS . Plasma VEGF levels were 79.14 pg/dl ( SD : 121.44 ) and 57.57pg/dl ( SD : 102.71 ) in the AMS and non-AMS groups , respectively . These results were nonsignificant . Similarly , comparison of sex , age , rate of ascent , pulse oximetry values , or history of altitude illness did not reveal significant differences between the AMS and non-AMS groups . Conclusion : This study does not provide evidence in support of the theory that plasma VEGF correlates with symptoms of AMS Forty-seven climbers participated in a double-blind , r and omized trial comparing acetazolamide 250 mg , dexamethasone 4 mg , and placebo every eight hours as prophylaxis for acute mountain sickness during rapid , active ascent of Mount Rainier ( elevation 4,392 m ) . Forty-two subjects ( 89.4 percent ) achieved the summit in an average of 34.5 hours after leaving sea level . At the summit or high point attained above base camp , the group taking dexamethasone reported less headache , tiredness , dizziness , nausea , clumsiness , and a greater sense of feeling refreshed ( p less than or equal to 0.05 ) . In addition , they reported fewer problems of runny nose and feeling cold , symptoms unrelated to acute mountain sickness . The acetazolamide group differed significantly ( p less than or equal to 0.05 ) from other groups at low elevations ( 1,300 to 1,600 m ) , in that they experienced more feelings of nausea and tiredness , and they were less refreshed . These drug side effects probably obscured the previously established prophylactic effects of acetazolamide for acute mountain sickness . Separate analysis of an acetazolamide subgroup that did not experience side effects at low elevations revealed a prophylactic effect of acetazolamide similar in magnitude to the dexamethasone effect but lacking the euphoric effects of dexamethasone . This study demonstrates that prophylaxis with dexamethasone can reduce the symptoms associated with acute mountain sickness during active ascent and that acetazolamide can cause side effects that may limit its effectiveness as prophylaxis against the disease
target: Ensuring that the characteristics of the history and future ascents are similar may improve the clinical utility of AMS history
background: PURPOSE The goal of this meta- analysis was to determine the clinical utility of  acute mountain sickness ( AMS ) history to predict future incidents of AMS .