When lungs on mountains leak. Studying pulmonary edema at high altitudes

Atrial natriuretic peptide blockade exacerbates high altitude pulmonary edema in endotoxin-primed rats

High altitude pulmonary edema (HAPE) is associated with increases in pulmonary arterial and hydrostatic pressures and an increase in pulmonary vascular permeability. There is evidence to suggest that inflammatory mediators may cause some forms of HAPE, and Salmonella enteritidis endotoxin (ETX) is known to activate neutrophils and inflammatory mediators, such as TNF-alpha and IL1-beta. Since HAPE has been produced in rats primed with ETX, we hypothesized that ANP release and action may ameliorate HAPE and that ANP blockade may exacerbate HAPE in ETX-primed rats exposed to high altitude (HA). Plasma ANP, right atrial ANP mRNA, and indexes of lung injury were measured in rats primed with endotoxin (ETX) (0.1 mg/kg BW, i.p.) and exposed to simulated HA (4267 m; P(B) = 440 mmHg) for either 12 or 24 h. Catheters were chronically inserted into the right carotid artery, pulmonary artery, and jugular vein for assessment of hemodynamic parameters in response to ETX and/or HA. In addition, some rats were injected with an antibody against ANP (alphaANP) prior to normoxic (NX) or HA exposure. Pulmonary arterial pressure increased in the alphaANP group (50 +/- 20%; p < or = 0.05) and in the HA + alphaANP (51 +/- 15%; p < or = 0.05) group at 12 h compared to NX sham rats injected with normal rabbit serum. In addition, systemic arterial pressure was significantly lower in the HA + ETX rats compared to HA + ETX + alphaANP rats (p < or = 0.001). Plasma ANP levels were significantly higher at 12 and 24 h in ETX, HA, and HA + ETX groups (p <or = 0.05) compared to NX controls. There was an inverse relationship (p <or = 0.001) between plasma ANP levels and lung wet to dry (W/D) weight when data from NX, ETX, HA, and HA + ETX groups were pooled. The HA + alphaANP rats had significantly higher lung W/D ratios (p < 0.001) compared to sham rats. These results support the hypothesis that ANP, at physiological levels, modulates the development of pulmonary edema in HA-exposed ETX-primed rats.

Urinary leukotriene E4 levels in high-altitude pulmonary edema. A possible role for inflammation

STUDY OBJECTIVES

Inflammation may contribute to the pathogenesis of high-altitude pulmonary edema (HAPE). This study was designed to determine whether a marker of inflammation, urinary leukotriene E4 (LTE4), is elevated in patients with HAPE.

DESIGN

We conducted a case-control study to collect clinical data and urine samples from HAPE patients and healthy control subjects at moderate altitude (> or = 2727 m), and follow-up urine samples from HAPE patients following their return to low altitude (< or = 1,600 m).

SETTING

Five medical clinics in Summit County, Colorado.

PATIENTS

Questionnaire data were evaluated in 71 HAPE patients and 36 control subjects. Urinary LTE4 levels were determined from a random subset of 38 HAPE patients and 10 control subjects presenting at moderate altitude, and on 5 HAPE patients who had returned to low altitude.

MEASUREMENTS AND RESULTS

Using an enzyme immunoassay technique, urinary LTE4 levels were found to be significantly higher in HAPE patients (123 [16 to 468] pg/mg creatinine, geometric mean [range]) than in control subjects (69 [38 to 135]), p = 0.02. Following return to low altitude, urinary LTE4 levels fell significantly from 122 (41.8 to 309) to 53.6 (27.6 to 104) pg/mg creatinine (p = 0.05). Urinary LTE4 levels were not related to age, sex, time at altitude, physical condition or habitual exercise, recent use of alcohol or nonsteroidal anti-inflammatory drugs (NSAIDs), or oxygen saturation. Clinical factors associated with HAPE included male sex, regular exercise, and recent use of NSAIDs.

CONCLUSIONS

We conclude that urinary LTE4 levels are elevated in patients with HAPE, supporting the view that HAPE involves inflammatory mechanisms.

Doctor on a mountaineering expedition

Doctors are welcome members on mountaineering expeditions to remote areas, but practical advice on how to prepare and what kit to take can be difficult to find. This article is a ragbag of useful advice on diverse topics. It explains the necessary preparation, provides tips for a healthy expedition, and summarises the common disorders encountered at high altitude. The comprehensive drug and equipment lists and first aid kit for climbers were used for the 1992 Everest in winter expedition. They are there to be sacrificed to personal preference and the experience and size of individual expeditions.

Southwestern Internal Medicine Conference: pulmonary complications of high-altitude exposure

The primary physiologic disturbance at high altitude is hypoxemia, which leads to a cascade of secondary changes in each step of the oxygen-transport chain. The author, in this review, focuses on the alterations in ventilatory control and alveolar-capillary gas exchange at high altitude and discusses the clinical pulmonary complications associated with these alterations, as well as their prevention and management.

High-altitude pulmonary edema with pulmonary thromboembolism

High-altitude pulmonary edema (HAPE) is a form of noncardiogenic pulmonary edema. The pathophysiology of HAPE remains unclear. A case of HAPE was associated with pulmonary thromboembolism of a left upper pulmonary artery. Pulmonary thromboembolism was an important factor in development of HAPE in this case.