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.

Preparation

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.

Normal results

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.

Risks

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.

Resources

BOOKS

Lehne, Richard A. Pharmacology for Nursing Care, 3rd edition. Philadelphia: W. B. Saunders Company, 1998.

PERIODICALS

Baka, Nour-Eddine. "Colostrum Morphine Concentrations during Postcesarean Intravenous Patient-controlled Analgesia." Journal of the American Medical Association 287, no. 12 (March 27, 2002): 1508.

Ellis, Jacqueline A., Renee Blouin, and Jean Lockett. "Patient-Controlled Analgesia: Optimizing the Experience." Clinical Nursing Research 8, no. 3 (August 1999): 283–294.

"Give a PCA Pump to Patients in Pain." ED Nursing 5, no 2 (December 2001): 27.

"Patient Controlled Analgesia for Children." CareNotes (December 2001).

ORGANIZATIONS

American Association of Nurse Anesthetists/AANA. 222 South Prospect Avenue, Park Ridge, IL 60068-4001. (847) 692-7050; Fax: (847) 692-6968. E-mail: <info@aana.com>. Web site: <http://www.aana.com>.

American Association of Nurse Anesthetists/AANA, Federal Government Affairs Office. 412 1st Street, SE, Suite 12, Washington, DC 20003. (202) 484-8400; Fax: (202) 484-8408. E-mail: <info@aanadc.com>.

American Society of PeriAnesthesia Nurses/ASPAN. 10 Melrose Avenue, Suite 110, Cherry Hill, NJ 08003-3696. (877) 737-9696; Fax: (856) 616-9601. E-mail: <aspan@ aspan.org>. <http://www.aspan.org>.

American Society of Anesthesiologists/ASA. 520 North Northwest Highway, Park Ridge, IL 60068-2573. (847) 825-5586; Fax: (847) 825-1692. E-mail: <mail@asahq.org>.

The National Hospice and Palliative Care Organization/NHPCO. 1700 Diagonal Road, Suite 300, Alexandria, VA 22314. (703) 837-1500. E-mail: <info@nhpco.org>.

Janie F. Franz Jennifer Lee Losey, RN

An analgesic (colloquially known as a painkiller) is any member of the diverse group of drugs used to relieve pain (achieve analgesia). The word analgesic derives from Greek an- ("without") and -algia ("pain"). Analgesic drugs act in various ways on the peripheral and central nervous systems; they include paracetamol (acetaminophen), the non-steroidal anti-inflammatory drugs (NSAIDs) such as the salicylates, narcotic drugs such as morphine, synthetic drugs with narcotic properties such as tramadol, and various others. Some other classes of drugs not normally considered analgesics are used to treat neuropathic pain syndromes; these include tricyclic antidepressants and anticonvulsants.

The major classes

Paracetamol and NSAIDs

The exact mechanism of action of paracetamol/acetaminophen is uncertain, but it appears to be acting centrally. Aspirin and the other NSAIDs inhibit cyclooxygenase, leading to a decrease in prostaglandin production; this reduces pain and also inflammation (in contrast to paracetamol and the opioids).

Paracetamol has few side effects, but dosing is limited by possible hepatotoxicity (potential for liver damage). NSAIDs may predispose to peptic ulcers, renal failure, allergic reactions, and hearing loss. They may also increase the risk of hemorrhage by affecting platelet function. The use of certain NSAIDs in children under 16 suffering from viral illness may contribute to Reye's syndrome.

COX-2 inhibitors

These drugs have been derived from NSAIDs. The cyclooxygenase enzyme inhibited by NSAIDs was discovered to have at least 2 different versions: COX1 and COX2. Research suggested that most of the adverse effects of NSAIDs were mediated by blocking the COX1 (constitutive) enzyme, with the analgesic effects being mediated by the COX2 (inducible) enzyme. The COX2 inhibitors were thus developed to inhibit only the COX2 enzyme (traditional NSAIDs block both versions in general). These drugs (such as rofecoxib and celecoxib) are equally effective analgesics when compared with NSAIDs, but cause less gastrointestinal hemorrhage in particular. However, post-launch data indicated increased risk of cardiac and cerebrovascular events with these drugs due to an increased liklyhood of clotting in the blood due to a decrease in the production of protoglandin around the platelets causing less clotting factor to be released, and rofecoxib was subsequently withdrawn from the market. The role for this class of drug is currently hotly debated.

Opiates and morphinomimetics

Morphine, the archetypal opioid, and various other substances (e.g. codeine, oxycodone, hydrocodone, diamorphine, pethidine) all exert a similar influence on the cerebral opioid receptor system. Tramadol and buprenorphine are thought to be partial agonists of the opioid receptors. Dosing of all opioids may be limited by opioid toxicity (confusion, respiratory depression, myoclonic jerks and pinpoint pupils), but there is no dose ceiling in patients who tolerate this.

Opioids, while very effective analgesics, may have some unpleasant side-effects. Up to 1 in 3 patients starting morphine may experience nausea and vomiting (generally relieved by a short course of antiemetics). Pruritus (itching) may require switching to a different opioid. Constipation occurs in almost all patients on opioids, and laxatives (lactulose, macrogol-containing or co-danthramer) are typically co-prescribed.

When used appropriately, opioids and similar narcotic analgesics are otherwise safe and effective, however risks such as addiction and the body becoming used to the drug can occur. Due to the body getting used to the drug often the dose must be increased if it is for a chronic disease this is where the no ceiling limit of the drug comes into play. However what must be remembered is although there is no upper limit there is a still a toxic dose even if the body has become used to lower doses.

Specific agents

In patients with chronic or neuropathic pain, various other substances may have analgesic properties. Tricyclic antidepressants, especially amitriptyline, have been shown to improve pain in what appears to be a central manner. The exact mechanism of carbamazepine, gabapentin and pregabalin is similarly unclear, but these anticonvulsants are used to treat neuropathic pain with modest success.

Specific forms and uses

Combinations

Analgesics are frequently used in combination, such as the paracetamol and codeine preparations found in many non-prescription pain relievers. They can also be found in combination with vasoconstrictor drugs such as pseudoephedrine for sinus-related preparations, or with antihistamine drugs for allergy sufferers.

The use of paracetamol, as well as aspirin, ibuprofen, naproxen, and other NSAIDS concurrently with weak to mid-range opiates (up to about the hydrocodone level) has been shown to have beneficial synergistic effects by combating pain at multiple sites of action—NSAIDs reduce inflammation which, in some cases, is the cause of the pain itself while opiates dull the perception of pain—thus, in cases of mild to moderate pain caused in part by inflammation, it is generally recommended that the two be prescribed together.

Topical or systemic

Topical analgesia is generally recommended to avoid systemic side-effects. Painful joints, for example, may be treated with an ibuprofen- or diclofenac-containing gel; capsaicin also is used topically. Lidocaine, an anesthetic, and steroids may be injected into painful joints for longer-term pain relief. Lidocaine is also used for painful mouth sores and to numb areas for dental work and minor medical procedures.

Psychotropic agents

Tetrahydrocannabinol (THC) and some other cannabinoids, either from the Cannabis sativa plant or synthetic, have analgesic properties, although the use of cannabis derivatives is illegal in many countries. Other psychotropic analgesic agents include ketamine (an NMDA receptor antagonist), clonidine and other α₂-adrenoreceptor agonists, and mexiletine and other local anaesthetic analogues.

Atypical and/or adjuvant analgesics

Orphenadrine, cyclobenzaprine, scopolamine, atropine, gabapentin, first-generation antidepressants and other drugs possessing anticholinergic and/or antispasmodic properties are used in many cases along with analgesics to potentiate centrally acting analgesics such as opioids when used against pain especially of neuropathic origin and to modulate the effects of many other types of analgesics by action in the parasympathetic nervous system. Dextromethorphan has been noted to slow the development of tolerance to opioids and exert additional analgesia by acting upon the NMDA receptors; some analgesics such as methadone and ketobemidone and perhaps piritramide have intrinsic NMDA action.

The use of adjuvant analgesics is an important and growing part of the pain-control field and new discoveries are made practically every year. Many of these drugs combat the side effects of opioid analgesics, an added bonus. For example, antihistamines including orphenadrine combat the release of histamine caused by many opioids, methylphenidate, caffeine, ephedrine, dextroamphetamine, and cocaine work against heavy sedation and may elevate mood in distressed patients as do the antidepressants. A well-accepted benefit of THC to chronic pain patients on opioids is its superior anti-nauseant action. However, it would make more sense to use the Marinol capsule, or oral, rectal, or vapour administration of hash oil, rather than smoking cannabis, for the same reasons most doctors advise against smoking tobacco.

Addiction

In the United States in recent years, there has been a wave of new addictions to prescription narcotics such as oxycodone (such as OxyContin, or with acetaminophen, as Percocet) and hydrocodone (commonly prescribed with acetaminophen, as in Vicodin, Lortab etc.) when available in pure formulations as opposed to combined with other medications (as in Percocet which contains both oxycodone and acetaminophen/paracetamol). Hydrocodone is only available in pure form in some European countries as the original hydrocodone pharmaceutical, Dicodid tablets. Far from reducing addiction liability, the paracetamol content of many codeine, dihydrocodeine, hydrocodone, and oxycodone pharmaceuticals in the United States only saddles users with the high risk of severe liver damage, and extraction of the opioids with cold water or solvents reduces this problem for the sophisticated abuser, self-medicator, and legitimate prescription holder alike

See also

• Pain management
• Patient-controlled analgesia
• Co-proxamol

References

• Cancer pain relief and palliative care. Report of a WHO expert committee [World Health Organization Technical Report Series, 804] . Geneva, Switzerland: World Health Organization; 1990. pp. 1–75. ISBN 92-4-120804-X.
• Bandolier pain site (Oxford pain group)

External links

• FDA proposes new pain reliever warnings