Hemodilution of polycythemic mountaineers: effects on exercise and mental function

Area of Science:

• High-altitude physiology
• Sports medicine
• Cardiovascular research

Background:

• Polycythemia, characterized by elevated hematocrit, is common in high-altitude dwellers and athletes.
• High hematocrit is often perceived to enhance oxygen delivery, but its effect on exercise and cognitive function at extreme altitudes is debated.

Purpose of the Study:

• To investigate the impact of acute isovolemic hemodilution on exercise capacity and cognitive function in polycythemic individuals at high altitude.
• To determine if a hematocrit exceeding 50% offers benefits or drawbacks for performance and mental acuity.

Main Methods:

• Four polycythemic mountain climbers (mean hematocrit 58%) underwent isovolemic hemodilution (15% blood volume removed, replaced with albumin) at 5400 m.
• Subjects performed standardized exercise and psychological tests before and after the hemodilution procedure.

Main Results:

• No significant changes were observed in maximal work level, oxygen uptake, ventilation, or blood oxygen saturation post-hemodilution.
• A slight increase in heart rate across all work levels and a small, significant improvement in psychological test scores were noted.
• Final hematocrit levels averaged 50.5% after the procedure.

Conclusions:

• Isovolumetric hemodilution was well-tolerated in this cohort.
• A hematocrit above 50% did not enhance exercise performance at 5400 m and may have negatively impacted cerebral function.
• While hemodilution improved cognitive function in this study, the procedure is considered potentially hazardous and rarely indicated.