Sporting regulatory bodies need to be aware of a newly-emerging doping threat in the form of artificial blood substitutes - or 'oxygen carriers' - which have potentially lethal side effects, warn a team of German scientists.

Although the use of recombinant human erythropoietin (rhEPO) has been banned as a means of boosting maximal oxygen uptake and can be screened for in blood and urine samples, no screening procedures have been developed so far for this new class of substances.

As the researchers explain: 'The next step to improve the crucial oxygen transport to the tissue might be the misuse of a new, emerging category of intravenously administered pharmaceuticals that immediately deliver oxygen to the body's tissues and enhance the offloading of oxygen from circulating red blood cells... There is the possibility that one or more of these blood substitutes will be approved for clinical use within a few years. Like rhEPO, artificial oxygen carriers might be used to artificially improve athletic performance as soon as they become available.'

The two main classes of artificial blood substitutes which have been investigated for medical purposes are:

Haemoglobin-based solutions. Haemoglobin (Hb) is the natural oxygen carrier of human blood, which is available in bovine form and can also be produced by genetic engineering. Although no studies investigating the effects of such solutions on maximal exercise capacity have been published, available data suggest that they might improve endurance performance. Several side effects have complicated their development, including raised arterial pressure and gastrointestinal problems. Detection in drug tests should be practicable since they can be screened for in urine and blood;

Perfluorocarbon-based solutions. Perfluoro-carbons (PFC), which can dissolve large quantities of oxygen, are closely related to teflon and can be manufactured at low cost. Human testing has been promising and, although no studies investigating the effects of PFC on exercise capacity in healthy subjects has been published, several investigations have shown that it could improve tissue oxygenation, even at low doses. The most commonly-reported side effects were flu-like symptoms. Since these substances are chemically and metabolically inert, detection in blood and urine tests might be difficult. However, they can be measured in expired air using gas chromatography.

'Although there are not many studies considering the influence of artificial oxygen carriers on endurance performance, these substances are said to have entered the world of sports already,' warn the researchers. 'As for EPO in the 1980s, the misusers might well be ahead of science and anti-doping regulations.

'Artificial oxygen carriers present with severe and possibly lethal side effects. For this reason and to discourage potential misusers, international sporting federations and the sports medicine community should be aware of the threat constituted by these substances. Legal and scientific background to introduce regular testing for modified Hb and PFC solutions must be provided as soon as possible.'

Int J Sports Med 2001 Nov 22(8) pp566-71.