| 
      Data presented as median (interquartile range). P value by Kruskall-Wallis.
    Intergroup differences (p<0.05) by Tukey’s test after log transformation: N.S=Non
    Significant. **P<0.01 compared to Tbaseline *P<0.05 compared to Tbaseline ***P<0.001
    compared to Tbaseline.
        |  | Morphine | Fentanyl | Significance |  
        | Pre-induction    (Tbaseline) | 88.27 ± 13.78 | 83.67 ± 6.6 | N.S |  
        | 30    min post-induction (T1) | 71.87 ± 9.2 *** | 77.1 ± 14.67 * | N.S |  
        | 30 min post-bypass (T2) | 69.8 ± 8.9 *** | 69.13 ± 9.49 *** | N.S |  
        | 1    hour post-bypass (T3) | 67 ± 10.64 *** | 71 ± 8.4 *** | N.S |  
        | 2    hours post-bypass (T4) | 68.73 ± 8.2 *** | 74.87 ± 7.51 ** | N.S |  
        | On    ICU admission (T5) | 70.13 ± 6.1 *** | 78.87 ± 6.1 | P<0.001 |  
        | 3    hours after ICU admission (T6) | 72.47 ± 5.05 *** | 79.9 ± 6 | P<0.01 |  
        | 6    hours after ICU admission (T7) | 76.4 ± 6 *** | 80.33 ± 5.3 | N.S |  |