Pearls and Pitfalls of Patient-Controlled Analgesia

Diana Stewart, PharmD

Disclosures

US Pharmacist. 2017;42(3):HS24-HS28. 

In This Article

Selecting Appropriate Candidates for PCA

PCA is commonly used to manage postoperative pain, and a significant proportion of clinical studies have evaluated PCA in this setting. Patients with acute pain from other causes, such as sickle cell disease and cancer, may also benefit from on-demand analgesia.[5,6] Factors to consider when determining whether a patient may safely benefit from PCA include age, cognitive function, physical ability to use the infusion pump, and comorbid conditions.[1,4] PCA should not be used in very young children who are unable to understand and follow directions reliably; however, children as young as 4 to 12 years have demonstrated successful PCA use for pain after bone marrow transplantation.[7]

Reasonable levels of consciousness and cognitive function are required to effectively manage PCA. Although conservative dosing in patients with confusion may prevent a safety event, it is also likely that the pain will not be controlled. Patients should receive PCA education in the preoperative setting rather than immediately after a surgical intervention, when the ability to process directions may be impaired.[8] Psychological factors in the absence of confusion and cognitive impairment have the potential to affect successful use of PCA. Autonomy through patient self-determination of the timing of analgesic administration is perhaps the fundamental advantage of PCA. Higher pain scores have previously been correlated with high levels of anxiety. Many patients experience a reduction in anxiety, and therefore have improved analgesia, because of the autonomy of PCA use.[9] Conversely, other patients may be fearful to request demand doses—leading to inadequate analgesia—but would accept administration by a trusted professional, such as a nurse or physician.

Comorbid conditions that increase the risk of respiratory depression with PCA include obstructive sleep apnea, morbid obesity, head injury, respiratory failure, renal failure, hypovolemia, and concurrent use of sedative medications, such as benzodiazepines.[10] Although these conditions are not absolute contraindications to PCA, conservative dosing and more stringent monitoring are warranted. Sedation always precedes respiratory depression and is a more reliable indicator than respiratory rate. Renal function should be considered in drug-selection and dosing strategies. Fentanyl and hydromorphone are preferred over morphine or meperidine in the setting of renal dysfunction to avoid accumulation of active neurotoxic metabolites (morphine-6-glucuronide and normeperidine).[11] Morphine is the most commonly used and studied opioid for PCA, closely followed by fentanyl and hydromorphone. Although methadone and meperidine also may be administered by PCA, the use of these agents is limited by adverse effects and complex pharmacokinetics, and they should be initiated only by a clinician with specialized training.

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