Which organ systems are affected by postoperative pain?
Multiple organ systems are affected by improperly treated postoperative pain. After thoracic or upper abdom-inal procedures, postoperative pain is associated with a decrease in the ability to breathe deeply and cough, and with reduced lung volumes. These effects predispose patients to atelectasis and impaired pulmonary toilet, pos-sibly leading to postoperative fevers. Involuntary splinting of thoracic and abdominal muscles, reflex muscle spasm, and premature airway closure cause ventilation-perfusion mismatch, leading to postoperative hypoxemia.
Pain causes stimulation of the sympathetic nervous system, resulting in release of catecholamines, such as nor-epinephrine and epinephrine. These circulating amines can result in tachycardia and peripheral vasoconstriction, increasing the workload on the heart. An increased incidence of ischemia, dysrhythmias, and hypertension has been shown to occur in patients whose pain is not adequately controlled.
The sympathetic discharge noted above has an adverse effect on the gastrointestinal (GI) system, causing an ileus and decreased GI motility. This effect must be considered with the use of systemic opioids, which can decrease the peristaltic activity of the GI tract even further.
Pain increases urinary bladder sphincter tone, with the potential for urinary retention.
The neuroendocrine stress response has been a topic of recent research. Postoperative pain has been demonstrated to be associated with a state of increased catabolism and decreased anabolism, leading to an overall catabolic state with negative nitrogen balance. This is associated with an increase in oxygen use and metabolism. This stress response has been associated with decreased wound healing. In addi-tion, activation of the stress response may be associated with maintenance of a hypercoagulable state, predisposing the patient to thromboses and embolic events.
Poor postoperative pain control can result in states of helplessness, depression, and increased anxiety.