Chapter 74: Pain: Epidemiology, Psychology, and Impact on Function

THE IMPACT OF PAIN

Some 30 million surgeries are performed annually in the United States, many resulting in significant acute postoperative pain. There also is an increasing trend toward utilization of oral opioids as the mainstay therapy.¹

Although most available literature on the prevalence of pain and its effects on patients focuses on chronic, rather than acute, pain, these studies nonetheless provide important insights into the impact of pain on quality of life. The prevalence of chronic pain is estimated to be approximately 4.1% for extremity pain to 10.1% for low back pain, although there is considerable variability among reports.^2,3 The percentage of patients who experience severe pain after surgery is difficult to determine in the literature, although it has been approximated in the 20%-40% range.⁴

Osteoarthritis and rheumatoid arthritis remain two of the most common causes of chronic pain. Chronic pain affects many important aspects of a patient’s life. These include sleep, exercise tolerance, activities of daily living, social activities, sexual function, and employment status.⁵ In a European study of patients with chronic pain of various types, it was reported that patients with chronic pain lost a mean time of 7.8 days of work over a 6-month period due to their pain.⁵ Approximately 60% of patients had visited a physician between two and nine times in the previous 6 months for pain-related issues. In this same study, 21% of respondents stated that they had been diagnosed with depression because of their pain.

Likewise, acute pain has many undesirable effects on patients beyond the unpleasantness of the sensory experience itself (Table 74–1). While the relationship between disturbed sleep and chronic pain remains somewhat difficult to discern, with evidence that either may exacerbate or facilitate the other,⁶ it is reasonably clear that acute, postoperative pain disturbs the sleep cycle,⁷ and that this may require time to revert toward normal, especially with regard to restoration of lost rapid-eye-movement sleep.⁸ The use of opioids in the perioperative period may further distort normal sleep patterns.⁹

Research suggests that both deep and superficial pain stimuli in muscle increase sympathetic nervous system activity, with concomitant elevations of heart rate and blood pressure.¹⁰ Such adrenergic excitation may predispose older patients with vascular occlusive disease to be at risk for adverse postoperative outcomes, since tachycardia is an independent risk factor for perioperative myocardial infarction.¹¹ Highly effective analgesic techniques, such as the use of regional anesthesia, have the potential to reduce such complications.¹²

It is difficult to separate the effects of surgical tissue trauma from the pain ...