PS1592 EFFECT OF ANAEMIA ON MUSCLE OXYGEN SATURATION DURING EXERCISE

Background: Transfusion of red cells in chronic hypoproliferative anemia aims to improve function in the recipients. Few studies examine functional measures as a trigger for transfusion, in part due to limited tools to functionally assess anemia. Aims: To evaluate the effect of anemia on muscle oxygen saturation (SmO 2 ) during exercise. Methods: Haematology patients with and without anaemia and normal controls were invited to participate. Each undertook a six minute walk test (6MWT) with continuous gastrocnemius SmO 2 monitoring. Patients with a significant change in haemoglobin (such as due to transfusion) were invited to repeat the investigation, up to three subsequent times. Changes in SmO 2 were examined in the pooled results of controls, key parameters identified and then extracted from individual participants. The correlation of each parameter with 6WWT distance, as a measure of functional capacity, was evaluated by linear and multifactorial regression. Participants with repeated 6MWT before and after hemoglobin changes were compared with paired T tests. Results: There were 73 participants, including 28 with known or presumed normal haemoglobin levels, undertaking 93 walking tests. Examination of control participant curves identified the SmO 2 parameters at baseline, nadir and plateau levels, with the fall in SmO 2 defined as the difference between baseline and nadir SmO 2 . In univariate analysis the distance walked correlated with haemoglobin (r = 0.47, p  < 0.001), baseline SmO 2 , (r = 0.34, p = 0.001), nadir SmO 2 (r = 0.26, p = 0.013) and the plateau SmO 2 (r = 0.4, p = 0.001) however these were not independent cofactors in multivariate analysis. The fall in SmO 2 did not correlate with the distance walked. There were 17 paired sets of walks with changed hemoglobin levels. An improved 6MWT distance was observed with increased hemoglobin concentration ( p  < 0.01), but there was no significant improvement in SmO2 values in individuals with higher haemoglobin concentrations. Summary/Conclusion: Anemia is associated with reduced function as measured by 6MWT distance and reduced SmO 2 before and during exercise. The absolute fall in SmO 2 during submaximal exercise was not increased by anemia. This may be due to decreased rate of oxygen demand with shorter walk distances seen in anemia. Although SmO 2 values are associated with the functional impairment of anemia, they are not superior to currently used triggers.