Predicting postoperative fatigue: importance of preoperative factors.

Postoperative fatigue as defined by a 10-point scale (1 = fit, 10 = fatigued) was determined prospectively in 84 patients undergoing major surgery. Results from this scale correlated well with standard psychological assessment of fatigue (Profile of Mood States Questionnaire) (r = 0.767; p < 0.0001). Fatigue values were 3.46 +/- 0.19 arbitrary units (mean +/- SEM) preoperatively; and postoperatively they were 5.61 +/- 0.24 at day 7, 5.02 +/- 0.24 at day 14, 3.74 +/- 0.19 at day 28, and 2.77 +/- 0.18 at day 90. Fatigue during the postoperative period was integrated to give a total fatigue score (332 +/- 14 arbitrary units, range 90-664), and this score was correlated with preoperative and early postoperative factors. The best predictor of postoperative fatigue was preoperative fatigue (r = 0.545; p = 0.001), with lesser correlations with diagnosis (especially cancer); preoperative weight, particularly total body protein (r = 0.317; p = 0.01); and weight loss (r = 0.29; p = 0.03), grip strength (r = 0.352; p = 0.01), and age (r = 0.267; p = 0.01). Postoperative fatigue was not correlated with preoperative anxiety, depression, or hostility, involuntary muscle function, gender, preoperative stress, or changes in total body protein or fat over the two postoperative weeks. It is concluded that patients who present for surgery already fatigued are the ones who are most likely to suffer from prolonged postoperative fatigue, particularly so if they are elderly, suffer from cancer, or have few extra reserves of body protein.