Patient-controlled analgesia (PCA) is a means for the patient to self-administer analgesics (pain medications) intravenously by using a computerized pump, which introduces specific doses into an intravenous line.
The purpose of PCA is improved pain control. The patient receives immediate delivery of pain medication without the need for a nurse to administer it. The patient controls when the medication is given. More importantly, PCA uses more frequent but smaller doses of medication, and thus provides more even levels of medication within the patient's body. Syringe-injected pain management by a nurse requires larger doses of medication given less frequently. Larger doses peak shortly after administration, often causing undesirable side effects such as nausea and difficulty in breathing. Their pain-suppressing effects also often wear off before the next dose is scheduled.
PCA uses a computerized pump, which is controlled by the patient through a hand-held button that is connected to the machine. The pump usually delivers medications in small regular doses, and it can be programmed to issue a large initial dose and then a steady, even flow. The PCA pump can deliver medicine into a vein (intravenously, the most common method), under the skin (subcutaneously), or between the dura mater and the skull (epidurally).
When the patient feels the need for medication, the patient presses a button similar to a nurse call button. When this button is pressed, some sound (usually a beep) is heard, indicating that the pump is working properly and that the button was pressed correctly. The pump delivers the medication through an intravenous line, a plastic tube connected to a needle inserted into a vein. Glucose and other medications can also be administered through intravenous lines, along with analgesics.
The medications most commonly used in PCA pumps are synthetic, opium-like pain-relievers (opioids), usually morphine and meperidine (Demerol).
The pump may be set to deliver a larger initial dose of the prescribed drug. The health-care provider sets the pump to deliver a specified dose, determined by the physician, on demand with a lockout time (for example, 1 mg of morphine on demand, but not more frequently than one dose every six minutes). If the patient presses the button before six minutes have elapsed, the pump will not dispense the medication. The pump also generates a record that the health personnel can access. An around-the-clock, even dose may also be set. The practitioner sets a total limit for an hour (or any other period) that takes into account the initial dose, the demand doses, and the around-the-clock doses. The pump's internal computer calculates all these amounts, makes a record of the requests it received and those it refused, and also keeps inventory of the medication being administered, which warns the staff when the supply is getting low.
An example of how a nurse might program the pump might be for a patient who has a prescription for a maximum of 11 mg of morphine an hour. The nurse sets the machine to deliver 1 mg at the beginning of the hour, and 1 mg on demand with a six-minute lockout. There are 10 six-minute periods in an hour, so the patient can request and receive 10 mg over that hour.
Using a PCA pump requires that the patient understand how the system works and has the physical strength to press the button. Therefore, PCA should not be offered to patients who are confused, unresponsive, or paralyzed. Patients with neurologic disease or head injuries in whom narcotics would mask neurologic changes are not eligible for PCA. Patients with poor kidney or lung function are usually not good candidates for PCA, unless they are monitored very closely.
PCA may be used by children as young as seven years old. It has proven safe and successful in such children in the control of postoperative pain, sickle-cell pain, and pain associated with bone-marrow transplantation. In all cases, the child should manage the PCA pump himself or herself. As morphine can slow breathing in young patients, the blood oxygen levels of children must be closely monitored.
In addition, PCA has been found safe for nursing mothers after a cesarean section . Very small amounts of morphine do pass into the milk of breastfeeding mothers, but it has not proved harmful to infants.
When preparing for PCA, the nurse must assess the patient to determine whether PCA is appropriate and then must set the total dose and the timing of the doses as prescribed by the physician. Since there is only a small amount of drug administered (3,000 doses at 10 mg each weigh less than 1 oz total), it is not sufficient fluid to keep the tubing and the needle from clogging and the contents from coagulating. Therefore, the drug must be put in a solution (flush solution) that will flow through the tube and needle easily, and permit rapid administration. The flush solution also keeps the line open for administration of other medications or in case the patient has a reaction to the pain medications. For example, a patient may have a reaction to morphine and would need counteractive medication immediately. The flush solution can also keep the patient from becoming dehydrated. In addition, many painkillers that are prescribed (such as morphine sulfate) are solid crystals at room temperature and need to be dissolved in some fluid to be absorbed by the body.
When entering the settings into the PCA system, the nurse must pay close attention to the physician's orders to ensure that the correct medication is used, that the concentration of the drug in the flushing solution is correct, that the dose of the drug itself is correct, that the lockout time is appropriate, and that the total hourly limit is properly entered into the pump's computerized controls. To eliminate the risk of incorrect programming, many institutions have adopted policies that require verification by a registered nurse (RN) to witness for all programming. That is, everything must be checked by two nurses, and both must sign the written record.
Another important aspect of PCA is patient education. The settings on the PCA pump must be explained to patients so that they understand how and when medications will be available. The nurse should observe patients as they first start using the button, should ensure that the equipment is functioning properly, and be clear that the patients understand their role in the process and are carrying it out correctly.
Whenever opium-like painkillers are administered to the elderly patient, it must be remembered that older adults may be more susceptible to the side effects of narcotics because the heart, liver, and kidneys of the elderly function less efficiently than those of younger patients. The elderly may also clear the narcotic out of their system at a slower pace. If the pump's timing device is calibrated for a younger person's rate of elimination, the elderly patient could accidentally receive an overdose. Doses for such elderly patients should be calculated more conservatively.
The goal of patient-controlled analgesia is managed pain control, enhanced by a stable and constant level of the pain medication in the body. The patient is able to rest better and breathe more deeply. Since the patient is comfortable, he or she is more able to participate in activities that would enhance recovery. PCA also gives the patient in the hospital some control in an unfamiliar and uncomfortable situation. When administered properly, and with watchful assessment by health care providers, PCA can be a safe alternative to traditional methods of relieving pain.
Interestingly enough, studies have shown that when patients control their pain medication, most use less medication overall than patients who have nurse-administered painkillers.
Problems that may occur with PCA include allergic reactions to the medications and adverse side effects such as nausea, a dangerous drop in the rate and effectiveness of breathing, and excessive sedation. The PCA device must be monitored frequently to prevent tampering. Even sophisticated devices that monitor themselves and sound an alarm should be checked often, since no machine is perfect. Ineffective pain control must be assessed to determine whether the problem stems from inadequate dosage or from inability, or unwillingness, of the patient to carry out his or her own pain management.
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