Fig. 2. Cumulative morphine consumption. Consumption was lowest at all time points in the combination group, which received epidural morphine and intravenous ketamine. Statistics are the same as in figure 1. The two-factor mixed-design analysis of variance with repeated measurement on one factor and the Dunn test were used. *P < 0.05, **P < 0.005 versus the control group. ¶P < 0.05, ¶¶P < 0.005 versus the combination group. See table 1for a definition of abbreviated terms.