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  • Safety and Patient-Controlled Analgesia

Controlled Analgesia

Patient-controlled analgesia (PCA) has considerable potential to improve pain management, allowing patients to self-administer more frequent but smaller doses of analgesia. When used as intended, PCA actually reduces the risk of oversedation, which is an unintended consequence of the more traditional method of nurse-administered analgesia in larger, less frequent doses. In fact, with PCA, patients often develop a synergism with the device and can quickly learn how to manage their pain while avoiding undue mental clouding. However, errors with the use of PCA therapy happen frequently, sometimes with tragic consequences.

Part 1 of this two-part series addresses the factors that have frequently contributed to the problem of safety and PCA use. online canadian pharmacy


Several safety features exist with PCA to ensure that patients do not receive too much analgesia. These include a lockout interval, which specifies the minimum amount of time between each dose, and a maximum allowable amount during one-or four-hour intervals.

Another built-in, often overlooked safety feature relates to the purpose of the device: it is intended for the patient’s use. Sedated patients generally do not press the button to deliver more opiate medication; thus toxicity is usually avoided. However, family members and health professionals have administered doses for patients by proxy, hoping to keep them comfortable. This well-intentioned effort has resulted in oversedation, respiratory depression, and even death.


Because an important safety feature of PCA is the capability of patients to deliver each dose, candidates for PCA should have the mental alertness and cognitive, physical, and psychological ability to manage their own pain. However, the benefits of PCA have led providers to extend its use to less-than-ideal candidates, such as infants, young children, and confused elderly patients. This has facilitated the dangerous practice of PCA by proxy. In addition, oversedation has occurred in unsuitable candidates who are at risk for respiratory depression because of obesity, asthma, sleep apnea, or the use of concurrent drugs that potentiate opiates.


Even at therapeutic doses, opiates can suppress respiration, heart rate, and blood pressure. As a consequence, nurses or other caregivers typically monitor patients at frequent intervals while they are using PCA. However, these monitoring activities may not alert caregivers to opiate toxicity.

First, patients are not always monitored frequently enough, especially during the first 24 hours and at night, when nocturnal hypoxia can occur. More often, however, the way in which caregivers assess patients might be at the root of the problem. Patients who are experiencing opiate-induced respiratory depression or over-sedation can easily be stimulated to a higher level of consciousness and an increased respiratory rate. Thus, if patients are disturbed during the assessment, their observed level of consciousness and respiratory rate are not helpful in detecting toxicity. After the stimulus is removed, patients quickly revert to an oversedated state.

There is also too much reliance on pulse oximetry readings. These readings can offer a false sense of security, because oxygen saturation is usually maintained even at low respiratory rates, especially if supplemental oxygen is in place.
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Most patients who are suitable candidates for PCA can be taught how to use the device successfully. However, patients who have been taught to use the device during the immediate postoperative period have often been too groggy to fully understand its use, and they often report poor pain control during the first 12 hours after surgery. Alert, intelligent patients also have misunderstood the directions for use; usually they believe that they must press the button every six minutes or so, even when they are sleepy and comfortable.

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