A theory of postoperative fatigue: an interaction of biological, psychological, and social processes.

The concept of postoperative fatigue has been developed to explain the feelings of malaise and the reduction in activity during the convalescent period that follows surgery in humans. Fatigue has been assumed to reflect the degree of surgical trauma and to be a consequence of muscle weakness caused by physiological sequelae of the trauma. The evidence is inconsistent with this reductionist view. Instead we propose a theory that postoperative fatigue is based on an emotional and motivational change that has the function of ensuring inactivity so as to preserve homeostasis in vital systems in response to injury while preserving the physical capacity to respond to new challenge. This response, triggered by the patient's perception of the surgical stimulus, is prolonged by the influence of staff and patient expectations, which, in turn, reflect cultural beliefs in the necessity of convalescence. This theory can be tested by manipulation of clinical practice at pharmacological and psychological levels.