Patient-Controlled Analgesia: An Update on Its Use in the Treatment of Postoperative Pain

Summary It is impossible to accurately predict how much pain a patient will experience after an operation or how much analgesic medication will be required to provide adequate pain relief. Thus, physicians and nurses necessarily rely on subjective methods to determine the analgesic regimen for patients experiencing postoperative pain. In reviewing the literature, it is obvious that “there is a deficient link in the chain that involves the patient who experiences pain and requests medication, the physician prescribing the analgesic drugs, and the nurse who assesses the pain and makes the decision about when to administer analgesics.”46 Problems arise because of the inherent difficulties in determining the appropriate dose and dosing interval, resulting in some patients being overmedicated while others continue to experience unacceptable levels of pain. Given the narrow “therapeutic window” for an individual patient, a carefully titrated dose of analgesic drug is needed to maintain adequate analgesia without undesirable side effects. PCA is a system designed to accommodate the wide range of analgesic requirements that can be anticipated when managing acute postoperative pain.33 PCA can also minimize the anxiety resulting from the slow onset of pain relief associated with most commonly used therapeutic modalities. A major psychological advantage with PCA therapy relates to its ability to minimize the time delay between the perception of pain and the administration of analgesic medication. In addition, the increased attention being paid to the PCA-treated patient both preoperatively and postoperatively might provide a psychological benefit to the patient. The comfort that patients experience as a result of compassionate and attentive nursing and medical care would be expected to significantly decrease their analgesic drug requirement.15 Although the concept of PCA therapy is not new,21, 30, 36 recent progress in the area of infusion pump technology has renewed interest in this concept. Early clinical studies have demonstrated that safe and effective postoperative pain relief can be achieved with a variety of PCA infusers. With PCA therapy, Graves et al have reported that patients experience minimal sedation during awake hours and progressively increase their physical activity during the postoperative period.24 These investigators suggested that results are better when patients control their own analgesia. In the postoperative situation, PCA is used for maintenance of analgesia. Thus, patients should receive a titrated loading dose prior to initiating self-administered analgesic therapy. If the therapy is to be successful, it is important that the nurse assess the individual patient’s response to the analgesic regimen. Given the marked pharmacodynamic variability that exists among patients with respect to their postoperative analgesic requirements, it will occasionally be necessary to alter the amount of the bolus dose and the duration of the lockout interval in order to optimize the therapeutic regimen. To achieve optimal results with PCA, both the patient and the staff should understand the basic principles upon which the therapy is based. Finally, applications of PCA therapy are not limited to the postsurgical ward. This concept can be applied to the management of acute and chronic cancer pain on medical and oncology wards. Others have suggested that PCA therapy could be used in obstetric suites, intensive care units, coronary care units, as well as in clinical research. Individuals with either markedly increased or decreased analgesic requirements can be adequately managed using a PCA delivery system. Thus, the rational use of a PCA infusion device allows the individual to overcome variations in both pharmacokinetic and pharmacodynamic factors by titrating the rate of narcotic administration to meet their individual analgesic needs. If recurrent (or intractable) nausea or vomiting develops, the patient can be switched to a different narcotic analgesic or antiemetic therapy can be administered. The commonly used antiemetic drugs (for example, droperidol, hydroxyzine) would be expected to enhance the sedation produced by the opioid analgesics. In conclusion, PCA provides improved titration of analgesic drugs, thereby minimizing individual pharmacokinetic and pharmacodynamic differences. PCA therapy decreases patient anxiety resulting from delays in receiving pain-relieving medication and from the slow onset of analgesic action when these drugs are administered either intramuscularly or in the extradural space. With PCA therapy, patients are able to maintain an acceptable level of analgesia with minimal sedation and few side effects. The potential for overdose can be minimized if small bolus doses are used with a mandatory lockout interval between successive doses. Finally, studies of the cost-effectiveness of PCA therapy are important if this therapeutic approach is to achieve even more widespread acceptance.