Case
A 69-year-old female with metastatic ovarian cancer and chronic pain syndrome presented to the hospital with seven days of progressively worsening abdominal pain. The pain had been similar to her chronic cancer pain but more severe. She has acute renal failure secondary to volume depletion from poor intake. A CT scan of the abdomen and pelvis reveal progression of her cancer with acute pathology. What is the best method of treating this patient’s pain?
Overview
Pain is pandemic. It is the most common reason patients seek healthcare.1 Almost one-third of Americans will experience severe chronic pain at some point in their lives. Every year, approximately 25 million Americans experience acute pain and 50 million experience chronic pain. Only one in four patients with pain receives appropriate therapy and control of their pain.
Pain is the most common symptom experienced by hospitalized adults.2 Acute or chronic pain can be particularly challenging to treat because these patients are frequently opioid dependent and have many psychosocial factors. No one method of pain control is superior to another. However, one method to gain rapid control of an acute pain crisis in a patient with chronic pain is to use patient-controlled analgesia (PCA).
Review of the Data
The first commercially available PCA pumps became available in 1976.3 They were created after studies in the 1960s demonstrated that small doses of opioids given intravenously provided more effective pain relief than conventional intramuscular injections.
The majority of studies on PCAs are in the postoperative patient, with cancer pain being next most commonly studied. PCAs utilize microprocessor-controlled infusion pumps that deliver a preprogrammed dose of opioid when the patient pushes the demand button. They allow programming of dose (demand dose), time between doses (lockout interval), background infusion rate (basal rate), and nurse-initiated dose (bolus dose).
The PCA paradigm is based on the opioid pharmacologic concept of minimum effective analgesic concentration (MEAC).4,5 The MEAC is the smallest serum opioid concentration at which pain is relieved. The dose-response curve to opioids is sigmoidal such that minimal analgesia is achieved until the MEAC is reached, after which minute increases in opioid concentrations produce analgesia, until further increases produce no significant increased analgesic effect.
PCAs allow individualized dosing and titration to achieve the MEAC, with small incremental doses administered whenever the serum concentration falls below the MEAC. A major goal of PCA technology is to regulate drug delivery to rapidly achieve and maintain the MEAC.