The oxygen uptake efficiency slope is not influenced by beta-blockade in end-stage liver disease patients

Matthew Wallen, Adrian Hall, Katrin Dias, Joyce S. Ramos, Shelley E. Keating, Tina L. Skinner, Aidan J. Woodward, Graeme A. MacDonald, Ross Arena, Jeff S. Coombes

Research output: Contribution to journalMeeting Abstractpeer-review

Abstract

Portal hypertension is a typical complication of end-stage liver disease (ESLD). Beta-blockade is used as prophylaxis to minimize the risk of gastroesophageal variceal haemorrhage. The use of beta-blockers may negatively impact peak oxygen uptake (V̇ O2peak) and ventilatory threshold (VT) by reducing cardiac output. V̇ O2peak and VT have shown to predict short- and long-term complications after liver transplantation but may be limited by peripheral fatigue due to beta-blockade. The oxygen uptake efficiency slope (OUES) represents the effectiveness of the body to extract oxygen from ventilation and may offer an effort-independent measure of cardiorespiratory fitness (CRF) in patients with ESLD. PURPOSE: To determine whether OUES is influenced by beta-blocker therapy compared to V̇ O2peak and VT in patients with ESLD. METHODS: Participants completed a symptom-limited cardiopulmonary exercise test (CPX) as part of pre-liver transplant risk stratification. Those who reached a respiratory exchange ratio (RER) ≥ 1.05 were included in the analysis. V̇ O2peak was determined as the highest 30-second average values during the test. VT was measured using the Vslope method. OUES [VO2 (L/min) = m(log10VE) + B, where m = OUES] was calculated at 50% (OUES50), 75% (OUES75) and 100% (OUES100) of the test. Independent t-tests and Mann-Whitney U tests compared the mean difference in CPX variables between participants on and off beta-blockade. RESULTS: Sixty-three participants [age 55.9 (interquartile range 51.4-59.5); model of end-stage liver disease score 15.5±4.7; male 85.7%] were included. Twenty-six participants (41%) were receiving beta-blockade at the time of CPX. Compared to those off beta-blockers, patients taking the medication demonstrated significantly (p<0.05) reduced VO2peak (3.9±3.7 vs. 16.1±2.6 ml.kg-1.min-1) and VT (10.7±2.6 vs. 12.6±2.1 ml.kg-1.min-1). However, there were no significant differences (p>0.05) at OUES100 (1.59± 0.48 vs. 1.76±0.51), OUES75 (1.61±0.43 vs. 1.72±0.52) and OUES50 (1.24±0.52 vs. 1.54±0.66) between beta-blocked and non-beta-blocked cohorts. CONCLUSION: Unlike traditional CRF measures, the OUES does not appear to be influenced by beta-blocker in patients with ESLD. The OUES may therefore have utility as an effort-independent measure of CRF in this patient cohort.
Original languageEnglish
Pages (from-to)711
JournalMedicine and Science in Sports and Exercise
Volume48
Issue number5S
Publication statusPublished - May 2016
Externally publishedYes
EventAmerican College of Sports Medicine's 63rd Annual Meeting -
Duration: 1 Jan 2016 → …

Keywords

  • End-stage liver disease (ESLD)
  • Oxygen uptake
  • Beta blockers
  • Cardio-respiratory fitness

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