Compositions and methods for preventing or reducing vasoconstriction in a mammal following administration of a vasoactive oxygen carrier (e.g., a heme-based oxygen carrier such as a hemoglobin-based oxygen carrier) are disclosed. The methods include administering to a mammal a composition containing a vasoactive oxygen carrier in combination with one or more of a nitric oxide-releasing compound, a therapeutic gas containing gaseous nitirc oxide, a phosphodiesterase inhibitor, and/or a soluble guanylate cyclase sensitizer.本發明揭示用於預防或減輕哺乳動物在投與血管活性氧載劑(例如基於血色素之氧載劑，諸如基於血紅蛋白之氧載劑)之後的血管收縮之組合物及方法。該等方法包括向哺乳動物投與含有血管活性氧載劑之組合物，組合以一或多種釋放氧化氮之化合物、含有氣態氧化氮之治療性氣體、磷酸二酯酶抑制劑及/或可溶性鳥苷酸環化酶敏化劑。
