Effects of red blood cell transfusion on patients undergoing cardiac surgery in Queensland – a retrospective cohort study by Obonyo, NG, Dhanapathy, V, White, N, Sela, DP, Rachakonda, RH, Tunbridge, M, Sim, B, Teo, D, Nadeem, Z, See Hoe, LE, Bassi, GL, Fanning, JP, Tung, J, Suen, JY, Fraser, JF