CHAPTER 6: Definitions and Classification of Pain

INTRODUCTION

Relief of pain is one of the great objectives of medicine. Pain is the most common symptom reported to physicians; more than 80% of all patients who see physicians do so because of pain. It has been a predominant concern of humankind since the beginning of recorded history. Chronic pain affects hundreds of millions of people worldwide, altering their physical and emotional functioning, decreasing their quality of life, and impairing the ability to work. According to an Institute of Medicine report released in 2011, one in three Americans experiences chronic pain—more than the total affected by heart disease, cancer, and diabetes combined. In Europe, the prevalence of chronic pain is 25% to 30%. It affects general health, psychological health, and social and economic well-being. Pain as a symptom—now considered the fifth vital sign—accounts for approximately 80% of physician visits and is estimated to cause $650 billion (in U.S. dollars) annually between health care expenditures and lost productivity percentage. More than 550 million workdays are lost every year because of chronic pain.

In October 2000, the 106th U.S. Congress passed HR 3244, which was then signed into law. Title VI, Section 1603, provides for the “Decade of Pain Control and Research,” to begin in January 2001. It follows the “Decade of the Brain” and is only the second congressionally declared, medically related decade. Pain is now designated as a public health problem of national significance. Beginning in 2001, the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) implemented new standards to assess and treat pain. To qualify for accreditation, all facilities—including rehabilitation centers, outpatient surgical centers, hospitals, and nursing homes—must recognize the right of patients to appropriate assessment and management of pain. All health care facilities must identify pain in patients during initial assessment and, where required, during ongoing periodic assessments and must educate patients and their families about pain management.

The word pain is derived from the Latin poena, meaning punishment. The International Association for the Study of Pain (IASP) defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” This definition may appear somewhat convoluted, but it clearly states that pain is subjective. It is both a physiologic sensation and an emotional reaction to that sensation. Viewed from an evolutionary prospective, pain is perceived as a threat or damage to one's biological integrity and has three components: sensory-discriminative, motivational-affective, and cognitive-evaluative.

The concepts of pain and suffering are frequently mixed and sometimes confused in the dialogue between patient and physician, especially because pain is commonly used as if it were synonymous with suffering. However, pain and suffering are distinct phenomena. Suffering is loosely defined as a “state of severe distress associated with events that threaten the ...