title: Field Ultrasound Evaluation of Central Volume Status and Acute Mountain Sickness.
abstract: OBJECTIVE
  To investigate whether ultrasonography can be used for field volume status assessment and to determine whether a detectable difference in intravascular volume exists in individuals with acute mountain sickness (AMS) compared with those without.
  
  
  METHODS
  Study was performed at the Himalayan Rescue Association Clinic in Manang, Nepal, located on the Annapurna trekking circuit at an altitude of 3519 m (11545 feet). A convenience sample was taken from individuals trekking over 5 to 8 days from 760 m (2490 feet) to 3519 m (11,545 feet), comparing asymptomatic trekkers vs those who experienced AMS. Subjects were evaluated for AMS based on the Lake Louise AMS Questionnaire (LLS ≥ 3 indicates AMS). After medical screening examination, both groups (control, n = 51; AMS, n = 18) underwent ultrasonography to obtain measurements of inferior vena cava collapsibility index (IVC CI) and left ventricular outflow tract velocity-time integral (LVOT VTI) before and after a passive leg raise (PLR) maneuver.
  
  
  RESULTS
  There was no statistically significant difference between groups regarding change in heart rate before and after PLR, or IVC CI; however, there was a statistically significant greater increase in LVOT VTI after PLR maneuver in control group subjects compared with those with AMS (18.96% control vs 11.71% AMS; P < .01).
  
  
  CONCLUSIONS
  Ultrasonography is a useful tool in the assessment of intravascular volume at altitude. In this sample, we found ultrasonographic evidence that subjects with AMS have a higher intravascular volume than asymptomatic individuals. These data support the hypothesis that individuals with AMS have decreased altitude-related diuresis compared with asymptomatic individuals.
authors: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA (Drs Pitman and Harris). Electronic address: jpitman@mgh.harvard.edu.
authors: Justin T
authors: JT
authors: Pitman
authors: Mountain Medicine Society of Nepal, Maharajgunj, Kathmandu, Bagmati, Nepal (Dr Thapa).
authors: Ghan B
authors: GB
authors: Thapa
authors: Department of Emergency Medicine, Massachusetts General Hospital, Boston, MA (Drs Pitman and Harris).
authors: N Stuart
authors: NS
authors: Harris
mesh_terms: D000208:Acute Disease; D000328:Adult; D000532:Altitude Sickness / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009051:Mountaineering; D009390:Nepal; D055815:Young Adult
keywords: acute mountain sickness; intravascular volume