Surgical pain(1) is a universal phenomenon affecting all patients in the intraoperative and postoperative period. Pain is defined by the International Association for the Study of Pain (IASP) as an “unpleasant sensory and emotional experience associated with actual or potential tissue damage(2).
From this definition we see that pain is a perception, not really a sensation, in the same way that vision and hearing are. It involves sensitivity to chemical changes in the tissues and then interpretation that such changes are harmful. This perception is real, whether or not harm has occurred or is occurring. Cognition is involved in the formulation of this perception. There are emotional consequences, and behavioral responses to the cognitive and emotional aspects of pain(3).
Apart from an agonizing sensory experience associated with acute pain, it has several deleterious effects on the physic and the psyche of the sufferer. An anticipation of these effects combined with a humanitarian urge to relieve pain, play a pivotal role in provision and optimization of postoperative analgesia. (4)
Ineffective postoperative pain management can result in a significant dysfunctional complication in substantial number of organ system which may progress to organ damage and even failure.
Consequences of poor pain control
Postoperative pain can affect all organ systems including:
1. Respiratory system (5-8)
Respiratory complications are considered the most common and most important effect of pain associated with abdominal or thoracic surgeries. The pattern of ventilation is characterized by small tidal volume, high inspiratory and expiratory pressures, decreased vital capacity, decreased functional residual capacity, and decreased alveolar ventilation.
These are associated with considerable impairment of pulmonary gas exchange leading to hypoxemia and hypercapnia. Also, the patient is unable to cough and clear secretions which contributes to lobar or lobular collapse. Infection often follows this situation leading to pneumonia.
2. Cardiovascular system (9-11)
Severe acute pain results in sympathetic over activity with increase in heart rate, peripheral resistance, arterial blood pressure, and cardiac output.