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Abstract
Go beyond the push-button approach to patient-controlled analgesia and learn what it takes to keep him both safe and pain-free.
PATIENT-CONTROLLED ANALGESIA (PCA), an attractive short-term option for managing acute postoperative pain, puts the patient in the driver's seat. At the push of a button, he can give himself a dose of pain medication without having to call a nurse and ask for it. Research has shown that PCA offers many advantages over clinician-controlled medication delivery, including better patient satisfaction with postoperative pain control, fewer pulmonary complications, earlier ambulation, and shorter hospital stays.1,2 (See Why choose PCA?)
But beware of taking a push-button approach to PCA. As it's grown in popularity, so have errors and other problems associated with its use. Reports of overdose and even the deaths of patients using PCA have cropped up, with PCA directly linked to the events.3-5
Safe PCA use requires proper patient selection, education, assessment, and monitoring. In this article, I'll explain your role and responsibilities in detail, including best-practice strategies for improving PCA safety. Let's start by reviewing the ABCs of PCA.
Not just a pump
The term "PCA" refers to a process, not simply a piece of equipment. Besides the PCA pump, the process includes the patient, nurse, pharmacist, and prescriber. If any component of the process falters, safety is compromised. Let's start with a look at the basic setup.
Patient-controlled analgesia pumps are computerized systems programmed for individual patient use. The prescriber chooses the medication, typically morphine or another opioid, and orders the dose, demand (bolus) dose interval, and lockout interval.
The dose interval is usually set at 6 or 8 minutes for postoperative patients. This means the patient can give himself one dose of medication every 6 or 8 minutes. The lockout interval is set at 1 hour or 4 hours, depending on facility policy. The lockout interval controls how much medication a patient can receive in the 1- or 4-hour period.
Current American Pain Society guidelines recommend the 6- or 8-minute dose interval and the 1-hour lockout.6Here's how an order might look:
PCA morphine, 1 mg/mL
Dose: 1 mg
Dose interval: 6 minutes
1-hour lockout: 10 mg
Even if the patient pushes the button more frequently than once every 6 minutes, he'll receive only one dose of medication in that period.
Compared with the 4-hour lockout, the 1-hour lockout lets you monitor PCA use more closely and adjust dosing as needed to control pain. For this reason, the 4-hour lockout is falling out of favor. If the patient uses all his allotted doses early in the 4-hour period, he may have to wait a long time before his PCA use is assessed and his poorly controlled pain is detected.
How do you know his pain control is inadequate? If his attempts to activate PCA are twice the number of doses actually delivered, you should increase the dose according to standing orders or request an order for a dose increase or a shorter dose interval.
Parameters for clinician boluses-extra doses of medication that you can administer to manage increased pain-should be included in the health care provider's orders: for example, 1 mg morphine intravenous (I.V.) bolus b.i.d. p.r.n. for dressing changes or before removing chest tubes. You'd then enter the PCA pump with the key or code and administer the specified bolus. At no time should anyone but the patient push the button.
Depending on its style, the PCA pump may be loaded with a bag or a syringe of I.V. solution (or, less commonly, a cassette). Drug concentrations can be adjusted as needed; for example, an opioid-tolerant patient would likely need a higher opioid concentration than an opioid-naive patient. However, differences in opioid concentrations can also contribute to errors associated with PCA use. The Joint Commission (TJC, formerly JCAHO) and the Institute for Safe Medication Practices (ISMP) recommend using standard doses and concentrations for safety; these are commonly available as prefilled syringes and bags.3,4
In the past, PCAs were often programmed to deliver a basal (continuous) I.V. infusion in addition to patient-administered bolus dosing. This is no longer recommended for opioid-naive patients because basal infusions add little to pain control while increasing the risk of oversedation.6,7
Making a point about decimals
A recent review of PCA practice in a hospital with 9,000 PCA patients per year revealed 56 PCA-related adverse events. Of these, 71% resulted from PCA programming errors causing overmedication or undermedication of patients. One reason for programming errors was a mistake involving a decimal point while programming the pump. For example, if an order called for morphine, 0.5 mg, the PCA might be incorrectly programmed for 5 mg. Other programming errors were wrong concentration, wrong dose, and using the loading dose for the bolus dose.
Human factors leading to the administration of wrong drugs and equipment problems accounted for 9% of adverse events. (Human factors are related to the fact that a human has to physically enter information into the pump; because of the significant potential for error, two nurses should check pump orders against the pump setting when initiating PCA or making a change.) Prescription errors accounted for 5%.8
What can we do to ensure safer drug administration via PCA? Let's look at some common PCA pitfalls and consider ways to guard against them.
Problems with PCA
These practices undermine PCA safety.
Improper patient selection. Patients who receive PCA after surgery must be able to understand the concept and willing to follow instructions for using PCA. For this reason, a confused patient isn't a good candidate for PCA. Besides being mentally alert and willing to learn how to use PCA, the patient must also be physically able to push the button independently.
Although PCA isn't appropriate for babies, children as young as age 5 have successfully used PCA. Parents typically worry that giving their children opioids will lead to addiction. In one study involving 93 children ages 8 to 18, researchers found that preoperative patient education on PCA use didn't improve analgesia, but it allayed the parents' concerns about opioid use, including the fear that their children would get "hooked" on opioid drugs or experience an overdose.2 Given the popularity of computer and video games, most children know how to push a button to produce a result, so a child's ability to understand PCA use is a more significant factor than his age.
Both TJC and the ISMP have weighed in on patient selection for PCA. Patient groups who generally aren't good candidates for PCA include:
* infants and young children
* confused older adults
* patients who are obese or have asthma or sleep apnea when their condition is a significant risk factor for oversedation
* patients taking other drugs that potentiate opioids, such as muscle relaxants, antiemetics, and sleeping medications.9-11
PCA by proxy. This term means that the PCA pump is activated by someone other than the patient, commonly relatives or friends. Well-intentioned family members can cause significant oversedation by delivering unneeded doses to patients who are sleeping or already sedated. This practice overrides an important safeguard built into PCA: A patient who's already sedated won't push the button and give himself unnecessary and excessive medication. This is why a patient who can't activate PCA himself isn't a good candidate and needs a different method of pain control.
But despite growing evidence that PCA by proxy is unsafe, it continues to be controversial. Some clinicians argue that the practice is appropriate in certain settings, such as pediatrics; some facilities allow family members to activate PCA when a patient is too young or otherwise unable to push the button independently. Facilities that allow this practice must define the parameters of the practice and thoroughly educate family members and other caregivers.
The American Society for Pain Management Nursing has developed a position statement for the use of "authorized agent controlled analgesia" to provide analgesia for patients who can't self-administer doses. It provides detailed guidelines for using nurse- or caregiver-activated PCA with specific orders and parameters for use. Information on the statement is available at http://www.aspmn.org .
Only one adverse event relating to PCA by proxy appears in TJC's database, but that may reflect the fact that reporting in this system is voluntary. The errors database for the United States Pharmacopeia lists 6,069 PCA errors, with 460 of them resulting in harm or death. Of these 460 errors, 12 were attributed to PCA by proxy. One of the 12 cases was fatal, with a nurse listed as the person who pushed the button for the patient.9
These adverse events involving PCA by proxy occurred in various patient-care units, including intensive care, postanesthesia, oncology, pediatrics, maternity, outpatient surgery, endoscopy/gastrointestinal lab, and preholding areas-all units where patients and family members should be under close observation.
Pump problems. Equipment design flaws can lead to adverse events associated with PCA use. For example, if the activation button resembles the call light button, a patient may inadvertently give himself an extra dose when he intended to call a nurse. And, unless the pump has a feature to alert the patient that a dose has been delivered, he may not be able to tell if he received medication when he pressed the button. He may then press the button more times than he would have with accurate feedback.3 "Smart pump" features have improved the safety of other types of I.V. pumps, but the technology for PCA pumps lags behind. Know your pump's features and shortcomings and teach your patient accordingly.
Human errors. Improperly programming the PCA pump is by far the most common type of human error. For safety, PCA pumps should be easy to program and designed to prevent free-flow. They should also require a review of all entered settings before use.10 At least one newer pump model has a screen that asks the programmer for a second confirmation of the settings.
Most reported programming errors involve one or more of the following:
* confusing milliliters and milligrams
* confusing PCA bolus doses and a basal rate
* loading dose programmed where a basal rate should have been entered
* wrong lockout settings selected
* wrong concentration selected.
Intervening for safety
As nurses, we can be a significant barrier to errors if we follow the recommendations of the ISMP and TJC.
* Learn to use the PCA pumps in your facility and maintain proficiency. To reduce the risk of confusion, the ISMP recommends using the same PCA model throughout the facility.
* Accept only PCA orders written on preprinted order sets.
* Develop a list of patients who are good PCA candidates and those who are not.
* Have your ability to enter a prescription into a PCA pump validated regularly.
* When you're initiating PCA, have another nurse independently check patient ID, drug and concentration, PCA pump settings, and the line and site where the PCA drug will be infusing.10
Use capnography to monitor hypoventilation
Most clinicians agree that PCA is an excellent method of postoperative pain relief and that most patients have no problems using it. However, judging patient response is difficult-especially in opioid-naive patients who are started on PCAs in the postoperative period. Research suggests that the incidence of respiratory depression in these patients may be underreported.12
Although pulse oximetry (Spo2) is commonly used to monitor falling arterial oxygen saturation, capnography is emerging as a more reliable indicator of respiratory depression. A patient receiving high-flow supplemental oxygen could develop severe hypercapnia despite adequate pulse oximetry readings, and some patients maintain oxygenation saturations that appear normal even with shallow respiratory efforts.11,13-15
Capnography, which measures end-tidal carbon dioxide, is easy to use in any practice setting. Readings can be taken from the patient wearing a mask or a nasal cannula with a sampling device. Results appear on a small handheld device similar in size to a personal digital assistant.
Using pulse oximetry and capnography together gives you better information about your patient's respiratory status than either method alone. By using both, you can intervene before oxygen saturation becomes dangerously low (below 85%) or carbon dioxide becomes dangerously high (PaCO2 above 45 mm Hg).
One manufacturer makes a portable device that detects both decreasing oxygen saturation and increasing carbon dioxide. Included as part of a continuous flow system for PCAs, it can be used for patients of all ages, whether intubated or not.13
Stay alert for oversedation
Besides following trends in SpO2 and ETCO2, closely monitor your patient for oversedation using a reliable sedation-rating tool. Make sure all staff members know how-and how often-to assess and document his sedation level. (See Tips for monitoring patients on PCA.)
Using a sedation-rating tool consistently and frequently is the key to preventing oversedation and other potential problems.11 One simple and easy-to-use sedation scale rates patient response as follows:
S- asleep
1- awake and alert, no action needed
2- slightly drowsy, no action needed
3- frequently drowsy, drifts off during conversation; requires action/decrease dose
4- somnolent, minimal or no response to physical stimulation; unacceptable, stop opioid, consider administering naloxone.
Although this scale hasn't been scientifically validated, it's commonly used in practice.16
Keep in mind that even a patient who's experiencing opiate-induced respiratory depression or oversedation may respond to stimulation that increases respiratory rate and level of consciousness. So don't assume that he's all right just because he can be roused and answer questions.3,11
Follow the leaders
The Joint Commission and the ISMP have combined efforts to enhance patient safety with PCA. They recommend these actions to ensure the safety of patients using PCA pumps.4,10
* Use standard order sets and prefilled syringes with standard drug concentrations. Place hydromorphone and morphine in separate areas of the pharmacy to avoid confusion.
* Select patients carefully for PCA use.
* Ensure that PCA pumps are programmed correctly. As nurses, we should know how to program pumps, maintain competency on them, and have our ability to enter a prescription validated.
* Check PCA pump settings at least once every 4 hours.
* Monitor patients carefully. Fully understand the difference between oversedation and other complications, such as pulmonary embolism, stroke, and signs of opioid toxicity or withdrawal from alcohol or another drug. A quick neurologic check, including checking the pupils, can give you fast preliminary assessment information.
* Teach patients and their families about safe PCA use and explain why no one but the patient should ever push the button for medication.
* Place warning signs on all PCA pumps that say "For patient use only."
Following the recommendations from authorities such as TJC and the ISMP can help you keep all patients receiving PCA both comfortable and safe.
Why choose PCA?
When used appropriately, PCA is superior to intermittent I.V. injections of pain medication for several reasons.1,6
* The patient experiences better pain relief. By using PCA, he maintains a steady serum level and avoids the peaks and valleys of I.V. opioids given intermittently. (Intramuscular injections are no longer recommended for pain relief.)
* The patient maintains control over pain relief.
* With his pain under control, he can breathe deeply and ambulate early, aiding his recovery and reducing the risk of complications.
* Using PCA may shorten the length of hospital stay after major surgery.
Tips for monitoring patients on PCA
When you care for a patient on PCA, follow these guidelines to keep him comfortable and safe.
* Establish and consistently use a standard pain-rating scale to track pain levels.
* Develop and follow a standard policy for monitoring for oversedation and other adverse reactions. For example, assess pain level, alertness, and vital signs, including respiratory rate and quality, at least every 4 hours or more often as needed, such as during the first 24 hours of treatment and at night, when nocturnal hypoxia may develop.
* Assess for sedation using minimal spoken and tactile stimulation. Keep in mind that oversedated patients may respond to more vigorous stimulation.
* Identify patient factors that may increase the risks of PCA, such as obesity or low body weight, sleep apnea, or asthma. Monitor these patients more frequently and initiate additional safeguards (such as capnography) as indicated.
Source: Institute for Safe Medication Practices.3
REFERENCES
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6. Principles of Analgesic Use in the Treatment of Acute Pain and Cancer Pain, 5th edition. American Pain Society, 2003. [Context Link]
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