The effect of bloodletting on exercise performance in a subject with a high-affinity hemoglobin variant

Abstract

We studied two young army recruits with erythrocytosis. One had a variant hemoglobin with high affinity for oxygen (hemoglobin Osler, also known as Fort Gordon and Nancy, beta 145 Tyr leads to Asp). The other had normal oxygen affinity and erythrocytosis of undetermined etiology. Both were asymptomatic. We studied exercise capacity on a cycle ergometer before and after hemodilution. In the subject with high oxygen affinity, hemodilution resulted in reduced maximal work and increased heart rate at every work level. In addition, minute ventilation and arterial lactic acid increased, while anaerobic threshold decreased, indicating diminished oxygen supply to tissues. In contrast, the subject with normal oxygen affinity had no significant changes in exercise performance after hemodilution. These results suggest that when blood oxygen affinity is high, loss of efficiency in tissue oxygenation can be expected after phlebotomy or hemodilution. Therefore, it may be useful to measure blood oxygen affinity and exercise performance in polycythemic subjects in whom such procedures are intended to ameliorate symptoms of hyperviscosity.

How we diagnose and manage altered oxygen affinity hemoglobin variants

“…In one instance of a woman with Hb Yakima, symptoms of hyperviscosity improved following phlebotomy down to an HCT of 0.52, and there was no difference in the patient's exercise performance pre‐phlebotomy and post‐phlebotomy, as measured by the maximum time achieved on the Bruce protocol. There are other reports, however, showing decreased exercise performance in patients with high affinity variants following phlebotomy . It is important to note that the target HCT proposed here is higher than that currently employed in patients with polycythemia vera (PV) …”

Guidelines for the diagnosis, investigation and management of polycythaemia/erythrocytosis

“… Most individuals remain asymptomatic. Experimentally, isovolaemic venesections performed in asymptomatic individuals with a high oxygen affinity haemoglobin, and resulting in a reduction in Hct from mean values of 0·55 to 0·41, can reduce exercise performance (Butler et al , 1982; Winslow et al , 1983). Hyperviscosity symptoms and thromboembolic episodes have been reported (Fairbanks et al , 1971; Weatherall et al , 1977).…”

“…Experimentally, isovolaemic venesections performed in asymptomatic individuals with a high oxygen affinity haemoglobin, and resulting in a reduction in Hct from mean values of 0·55 to 0·41, can reduce exercise performance (Butler et al , 1982; Winslow et al , 1983).…”

Venesection in Haemoglobin Yakima, a high oxygen affinity haemoglobin

“…Over 30 high affinity Hbs associated with polycythaemia have been described (Winslow & Anderson 1982). Most individuals are asymptomatic as illustrated in this kindred, it is unlikely that the other affected members would have been investigated on the basis of their Hb and PCV values.…”

“…In addition, our patient felt non-specifically better. However, it has been demonstrated that following isovolumetric haemodilution there is a reduction in the anaerobic threshold at the lower haematocrit Winslow et al 1983). Thus a modest reduction of high PCV values to relieve symptoms of hyperviscosity can be beneficial, but the response should be carefully monitored.…”