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BACKGROUND: Hypoxic pulmonary vasoconstriction (HPV) helps match pulmonary perfusion to ventilation. The peptide endothelin-1 (ET-1) may be involved in the cellular mechanisms of this response. We hypothesized that increasing plasma ET-1 concentration during hypoxia would enhance HPV in humans and might represent a strategy for improving gas exchange during single-lung anaesthesia or respiratory disease. METHODS: Nine healthy volunteers were each exposed twice to a 7-h protocol consisting of 1 h breathing air, 4 h of eucapnic hypoxia (end-tidal Po(2), 50 mm Hg), and 2 h of eucapnic euoxia (end-tidal Po(2), 100 mm Hg). Volunteers received a 7-h i.v. infusion of ET-1 during one protocol (1.0-2.5 ng kg(-1) min(-1)) and normal saline during the other. At intervals of 30-60 min, cardiac output and the maximum tricuspid pressure gradient during systole (DeltaP(max), an index of HPV) were measured using Doppler echocardiography, systemic arterial pressure was measured using sphygmomanometry, and plasma samples were obtained to determine ET-1 concentration. RESULTS: During hypoxia, DeltaP(max) increased for around 2 h before reaching a plateau. Compared with saline, ET-1 had no effect on DeltaP(max), either at baseline or during hypoxia. ET-1 infusion slightly increased diastolic arterial pressure and reduced cardiac output, but had no specific effect on the change in these variables during hypoxia. During the final 1 h of hypoxia, plasma ET-1 concentration was 1.7 (0.4) pg ml(-1) [mean (sd)] in the saline protocol and 21.9 (12.2) pg ml(-1) in the ET-1 protocol. CONCLUSIONS: ET-1 infusion seems unlikely to represent a therapeutic strategy for enhancing HPV during acute (<4 h) hypoxia.

Original publication

DOI

10.1093/bja/aen214

Type

Journal article

Journal

Br J Anaesth

Publication Date

10/2008

Volume

101

Pages

466 - 472

Keywords

Adult, Anoxia, Blood Pressure, Carbon Dioxide, Cardiac Output, Echocardiography, Doppler, Endothelin-1, Female, Humans, Male, Oxygen, Partial Pressure, Pulmonary Circulation, Vasoconstriction