Association between preoperative haemoglobin concentration and cardiopulmonary exercise variables: a multicentre study.
BACKGROUND
Preoperative anaemia and low exertional oxygen uptake are both associated with greater postoperative morbidity and mortality. This study reports the association among haemoglobin concentration ([Hb]), peak oxygen uptake (V˙O2 peak) and anaerobic threshold (AT) in elective surgical patients.


METHODS
Between 1999 and 2011, preoperative [Hb] and cardiopulmonary exercise tests were recorded in 1,777 preoperative patients in four hospitals. The associations between [Hb], V˙O2 peak and AT were analysed by linear regression and covariance.


RESULTS
In 436 (24.5%) patients, [Hb] was <12 g dl-1 and, in 83 of these, <10 g dl-1. Both AT and V˙O2 peak rose modestly with increasing [Hb] (r2 = 0.24, P <0.0001 and r2 = 0.30, P <0.0001, respectively). After covariate adjustment, an increase in [Hb] of one standard deviation was associated with a 6.7 to 9.7% increase in V˙O2 peak, and a rise of 4.4 to 6.0% in AT. Haemoglobin concentration accounted for 9% and 6% of the variation in V˙O2 peak and AT respectively.


CONCLUSIONS
To a modest extent, lower haemoglobin concentrations are independently associated with lower oxygen uptake during preoperative cardiopulmonary exercise testing. It is unknown whether this association is causative.
Division of Surgery and Interventional Science, University College London, 21 University Street, London WC1E 6DE, UK. james.otto@ucl.ac.uk.
James M
JM
Otto
Alasdair F
AF
O'Doherty
Philip J
PJ
Hennis
Jackie A
JA
Cooper
Michael Pw
MP
Grocott
Chris
C
Snowdon
John B
JB
Carlisle
Michael
M
Swart
Toby
T
Richards
Hugh E
HE
Montgomery