Table 3. Hierarchical linear models of the trajectories for average and worst postoperative pain.
| Average pain (n = 203) | Coefficient (SE) | |
| Unconditional model | Final model | |
| Fixed effects | ||
| Intercept | 5.286 (0.133)*** | 5.284 (0.122)*** |
| Piecewise 1—linear rate of change | -2.682(0.158)*** | -2.682 (0.153)*** |
| Piecewise 2 –linear rate of change | 1.629 (0.298)*** | 1.568 (0.290)*** |
| Piecewise 2 –quadratic rate of change | -0.858 (0.192)*** | -0.827 (0.187)*** |
| Piecewise 2 –cubic rate of change | 0.130 (0.032)*** | 0.126 (0.031)*** |
| Time invariant covariates | ||
| Intercept: | ||
| Number of comorbidities | 0.213 (0.079)** | |
| C-reactive protein | 0.062 (0.026)* | |
| Pain interference with function | 0.362 (0.047)*** | |
| Piecewise 1—linear rate of change | ||
| Consequences | -0.242 (0.051)*** | |
| Piecewise 2—linear rate of change | ||
| Average dose of opioids+ | 0.099 (0.033)** | |
| Average preoperative pain | -0.323 (0.146)* | |
| Piecewise 2—quadratic rate of change | ||
| Average dose of opioids+ | -0.040 (0.023) | |
| Average preoperative pain | 0.194 (0.102) | |
| Piecewise 2 –cubic rate of change | ||
| Average dose of opioids+ | 0.004 (0.004) | |
| Average preoperative pain | -0.028 (0.017) | |
| Variance components | ||
| In intercept | 1.168*** | 0.734*** |
| Goodness of fit deviance (df) | 4145.191 (7) | 4033.050 (17) |
| Model comparison χ2 (df) | 112.141 (10)*** | |
| Worst pain (n = 203) | Coefficient (SE) | |
| Unconditional model | Final model | |
| Fixed effects | ||
| Intercept | 5.512 (0.174)*** | 5.512 (0.164)*** |
| Piecewise 1—linear rate of change | -1.279 (0.212)*** | -1.295 (0.205)*** |
| Piecewise 2 –linear rate of change | 1.975 (0.404)*** | 1.902 (0.391)*** |
| Piecewise 2—quadratic rate of change | -0.852 (0.259)** | -0.817 (0.251)** |
| Piecewise 2 –cubic rate of change | 0.101 (0.043)* | 0.097 (0.041)* |
| Time invariant covariates | ||
| Intercept: | ||
| Age | -0.026 (0.012)* | |
| Fatigue severity | 0.206 (0.057)*** | |
| Identity | 0.253 (0.076)** | |
| Emotional response | 0.189 (0.047)*** | |
| Piecewise 1—linear rate of change | ||
| Sex (men as reference) | -0.475 (0.228)* | |
| Average preoperative pain | -0.216 (0.068)** | |
| Piecewise 2—linear rate of change | ||
| Worst preoperative pain | -0.603 (0.171)*** | |
| Piecewise 2 –quadratic rate of change | ||
| Worst preoperative pain | 0.343 (0.117)** | |
| Piecewise 2 –cubic rate of change | ||
| Worst preoperative pain | -0.050 (0.020)* | |
| Variance component | ||
| In intercept | 1.810*** | 1.374*** |
| Goodness of fit deviance (df) | 4792.618 (7) | 4695.011 (16) |
| Model comparison χ2 (df) | 97.607 (9)*** | |
Note: Time was coded as zero on the day of admission
Intercept = day of admission. Piecewice 1 = day of admission to DOS. Piecewice 2 = POD1 to POD4
+ Variable included in analysis as a covariate
*p < .05
**p < .01
***p < .001
Abbreviations: df = degrees of freedom; SE = standard error