Rav Chaim Kanievsky: Blood Transfusions - Jewish Blood and Blood of a Goy
One time when the Ponevezher Rav was abroad he became sick and needed a blood transfusion. He asked the Doctor to please make sure he receives only blood from a Jew. The Doctor assured him that would do so but did not keep his word and he received blood from a non-Jew. The transfusion was not successful and they were ultimately forced to find blood from a Jew. With the new blood the Ponevezher Rav was brought back to health.
Rav Chaim Kanievsky was asked if there is a Mekor for taking blood specifically from a Jew. He answered that indeed some people are Makpid on this and the Mekor is the Gemara in Shabbos that says that Shichvas Zera that comes out from a woman after three days is not Tamei because it decomposed in her body. The gemara asks does it also decompose inside a non-Jewish woman? The reason to say not, reasons the gemara, is because a Jew's body is warmer since we constantly worry about doing mitzvos. The heat can cause decomposition which you may not find in a Goy. For this reason some are Makpid to use a Jew's blood. (Verapo Yirapei)
Important Note: Rav Chaim (according to this source) did not say that one must use Jewish blood or that it is preferred. Nor did he say that there is any issue whatsoever with taking blood from a Goy. He merely found a Mekor in the gemara when asked about a personal decision made by another Gadol. This Mekor is not based on Halacha, rather it raises the issue of compatibility based on the divergent lifestyles of a Jew and a Goy. Additionally the gemara does not discuss blood per se. Furthermore the gemara remains undecided and leaves the issue unresolved.
Disclaimer: We try to convey the Tshuva to the best of our ability. We admit that our understanding may not be accurate. Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.