Total haemoglobin mass, but not haemoglobin concentration, is associated with preoperative cardiopulmonary exercise testing-derived oxygen-consumption variables

J. M. Otto, J. O.M. Plumb, D. Wakeham, E. Clissold, L. Loughney, W. Schmidt, H. E. Montgomery, M. P.W. Grocott, T. Richards

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Background: Cardiopulmonary exercise testing (CPET) measures peak exertional oxygen consumption (V˙O2peak) and that at the anaerobic threshold (V˙O2 at AT, i.e. the point at which anaerobic metabolism contributes substantially to overall metabolism). Lower values are associated with excess postoperative morbidity and mortality. A reduced haemoglobin concentration ([Hb]) results from a reduction in total haemoglobin mass (tHb-mass) or an increase in plasma volume. Thus, tHb-mass might be a more useful measure of oxygen-carrying capacity and might correlate better with CPET-derived fitness measures in preoperative patients than does circulating [Hb]. Methods: Before major elective surgery, CPET was performed, and both tHb-mass (optimized carbon monoxide rebreathing method) and circulating [Hb] were determined. Results: In 42 patients (83% male), [Hb] was unrelated toV˙O2 at AT andV˙O2peak (r=0.02, P=0.89 and r=0.04, P=0.80, respectively) and explained none of the variance in either measure. In contrast, tHb-mass was related to both (r=0.661, P<0.0001 and r=0.483, P=0.001 forV˙O2 at AT andV˙O2peak, respectively). The tHb-mass explained 44% of variance inV˙O2 at AT (P<0.0001) and 23% inV˙O2peak (P=0.001). Conclusions: In contrast to [Hb], tHb-mass is an important determinant of physical fitness before major elective surgery. Further studies should determine whether low tHb-mass is predictive of poor outcome and whether targeted increases in tHb-mass might thus improve outcome.

Original languageEnglish
Pages (from-to)747-754
Number of pages8
JournalBritish Journal of Anaesthesia
Issue number5
Publication statusPublished - May 2017
Externally publishedYes


  • anaemia
  • anaerobic threshold
  • cardiopulmonary exercise test
  • oxygen consumption
  • physical fitness
  • surgery

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