Association between preoperative haemoglobin concentration and cardiopulmonary exercise variables: a multicentre study

James M Otto,Toby Richards,Hugh E Montgomery,John B Carlisle,Michael Pw Grocott,Jackie A Cooper,Michael Swart,Chris Snowdon,Alasdair F O’Doherty,Philip J Hennis

doi:10.1186/2047-0525-2-18

Abstract

BackgroundPreoperative 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 ( peak) and anaerobic threshold (AT) in elective surgical patients.MethodsBetween 1999 and 2011, preoperative [Hb] and cardiopulmonary exercise tests were recorded in 1,777 preoperative patients in four hospitals. The associations between [Hb], peak and AT were analysed by linear regression and covariance.ResultsIn 436 (24.5%) patients, [Hb] was <12 g dl-1 and, in 83 of these, <10 g dl-1. Both AT and 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 peak, and a rise of 4.4 to 6.0% in AT. Haemoglobin concentration accounted for 9% and 6% of the variation in peak and AT respectively.ConclusionsTo 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.

Highlights

Preoperative anaemia and low exertional oxygen uptake are both associated with greater postoperative morbidity and mortality
V_O2 peak increased with each [Hb] group for maxillofacial patients after adjusting for testing and weight, but not when additional confounders were added to the model. To our knowledge, this is the largest study to explore the relationship between oxygen uptake and haemoglobin concentration in the clinical setting, and the first to control for body mass with allometric scaling
The relatively small explained variance in anaerobic threshold (AT) and V_O2 peak by [Hb] in the current study suggests that other factors may play an important role in determining aerobic capacity

Summary

Introduction

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. Increased mitochondrial oxygen uptake requires increased cellular oxygen delivery. Utilization, fails to meet metabolic demand, anaerobic cytoplasmic metabolism significantly augments aerobic mitochondrial ATP generation with a consequent increase in lactic acid production and accumulation. It has been suggested that an imbalance in oxygen demandsupply contributes to the point during cardiopulmonary exercise testing (CPET) known as the anaerobic threshold (AT) [1], this physiological underpinning is not without controversy [2,3]. Commonly defined as a haemoglobin concentration ([Hb]) below 13 g dl-1 (males) and 12 g dl-1 (non-pregnant females), reduces the blood’s oxygen carriage capacity. Anaemia and blood transfusion are associated with poor postoperative outcomes [10,11,12,13,14,15,16]

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