Under GAA rules, however, each team is subject to a maximum of 20 players - including the use of blood substitutes.

Although the county points out that two of the players were introduced as blood substitutes, the rule governing replacements is straightforward.

WASHINGTON, April 28 (Reuters) - Certain experimental blood substitutes raise the risk of heart attack and sudden death, researchers said on Monday.

Blood substitutes are more than just a mad scientist's folly ­ they're big business, a US$5 billion--a-yearindustryworldwide.