By Christina W. Chin, M.D.

(presented at the 1998 CAMS Annual Scientific Meeting)

Over the last decade, treatment of pain syndrome is more recognized by our society. In fact, more physicians dedicate themselves in the subspecialty of pain management. In the acute situation, pain is a protective mechanism as a result of physical insult or injury. Conversely, chronic pain syndrome causes both physiological and psychological derangement. Therefore, pain management is the state-of-the-art in both mind and body.

The principle in pain management includes detailed history and physical examination. Detailed history includes onset, location, frequency, duration of the pain, aggravating as well as alleviating factors. Measurement of the degree of pain can be expressed in descriptive terms (e.g., dull, aching, burning), verbal numerical scale (from 0 to 10 scale), and visual analog scale. Sleep disturbance is a major cause of depression, functional impairment and can cause disruption of life. After the initial evaluation, the pain specialist can interpret the physical findings and order diagnostic tests warranted.

Neural blockade is one of the diagnostic tools frequently used. It is also a tool for therapy as well as prognosis prior to the neurolytic procedure. Understanding the indications for neural blockade is as important as interpreting the result obtained from the procedure. For instance, differential blockade is used to determine whether the origin of pain is peripheral (e.g., neuroma, nerve entrapment), spinal (e.g., spinal cord compression), central (e.g., thalamic pain) or somatoform. One should remember that both non-cancer and cancer pain can be caused by several co-existing mechanisms.

Once the diagnosis is established, a therapeutic plan can be formulated. Medical therapy is usually the initial management for both cancer and non-cancer pain. However, one should bear in mind the limitation of medical modality. Concomitant physical therapy, optional surgical intervention and alternative medicine are also important.

According to the WHO (World Health Organization) guideline, a three-step ladder should be followed. Narcotic combinations are limited by the side effects of acetaminophen in causing liver damage and of NSAID in causing gastro-enterologic irritation. The efficacy of the newly marketed NSAID's has yet to be determined. Other analgesics include antidepressants, anxiolytics, anticonvulsants, local anesthetics, adrenergic agents and antihypertensive agents. Use of narcotics in non-cancer patient is controversial. In my opinion, with appropriate justification, establishment of narcotic contract with the patient, careful observation of the patient's behavior and frequent monitor of prescription, narcotics should not be deprived from this group of patients. In fact, while physical dependency is unavoidable, additcion behavior or psychological dependency is rare. The knowledge of pharmacodynamic and pharmacokinetic properties of narcotics is essential. Relative potency of different narcotics is shown in Table 1.

Table 1. Oral Potency Ratio of Narcotics

Narcotic Oral Potency Ratio

Morphine 1

Codeine 1/12

Meperidine 1/8

Oxycodone 1

Hydrocodone 1

Hydromorphone 6

Methadone 1.2

Proproxyphene 1/12

Levophanol 5

Pentazocine 1/5

(from Wall/Melzack)

The side effects of narcotics such as nausea, constipation, urinary retention and sedation are not considered as complication and can be managed easily. In patients who can not tolerate oral, transdermal, rectal or parental analgesic, interventional pain procedure, such as spinal cord stimulator, and implantable drug delivery system (e.g., morphine pump) can be considered. Careful screening and psychological evaluation is particularly important for choosing the appropriate candidate.

Pain specialist work hand in hand with other specialists in surgery, rehabilitation, psychology/psychiatry, oncology and also with primary care physicians. The goal is aimed at improving patient's functional capacity, quality of life while controlling pain with optimal analgesia.