Patient-Controlled Analgesia Health Article

Definition

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.

Purpose

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.

Description

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.