Patient-Controlled Analgesia

Anatomy and Physiology

Modalities for PCA administration include intravenous lines, central lines, epidural catheters, peripheral nerve catheters, or transdermal delivery systems. Any peripheral vein can be used to insert a catheter and begin the administration of PCA. Central lines are placed in the internal jugular, subclavian, or femoral veins.[5] Epidural catheter placement is in the epidural space between the dura and the ligamentum flavum, which lines the anterior portions of the vertebral lamina. Within the epidural space sits spinal nerves, blood vessels, and fat.[6] Indwelling epidural catheter placement is at thoracic and lumbar spinal levels. Peripheral nerve catheters are placed adjacently to the nerve or plexus and intended to block continuously. Depending on the desired target location, these run through the skin and potentially muscle.[2] Transdermal PCA delivery is through a fentanyl iontophoretic transdermal system, which is placed on the epidermis and provides a dose of fentanyl when the patient pushes a button on the patch.[3]

Indications

PCA can be an option for acute, chronic, postoperative, and labor pain, especially in patients who are unable to tolerate oral medications. PCA can be used to reduce the stress on the nursing staff and the patient of having to adhere to a predetermined dosing schedule of as-needed analgesics that may not adequately align with the patient’s fluctuation of pain. PCA can be useful in the acute pain setting where there is inadequate pain control from the initial opioid administration in the emergency department, and continued opioid dosing has been proven to improve patient outcomes. Common examples are vaso-occlusive pain crisis, trauma, pancreatitis, or burns. PCA would be used as an adjunct therapy to treat the pain while the underlying cause gets diagnosed and treated. Patients with chronic illnesses who are suffering from lower levels of constant chronic pain would also be candidates for PCA. The most common examples are metastatic cancer, phantom limb syndrome, and complex regional pain syndrome.[7] Post-surgical patients, especially those with indwelling nerve or epidural catheters, are also ideal candidates for PCA. The ability of a post-surgical patient to titrate and administer their pain medication allows for superior pain control to scheduled nursing dosing. It also increases patient satisfaction and results in fewer PACU and acute pain service staff interventions. ­Patients in labor pain are also well-established candidates for epidural PCA. The pain associated with contractions, especially when exacerbated by induction agents such as oxytocin, can be adequately reduced and controlled by the patient.[8]

Contraindications

Absolute contraindications to PCA include:

• The patient is unable to understand the concept behind PCA
• Systemic infection, or infections at the preferred site of PCA placement
• Allergic reactions to the selected medication
• Burns or trauma in the area of PCA placement
• Preexisting neural deficits in the area of a planned indwelling nerve catheter
• Increased ICP for epidural catheter placement

 Relative contraindications to PCA include:

• Chronic renal failure
• The patient is on antithrombotic therapy
• The patient has a documented bleeding disorder
• Sleep apnea

Equipment

The administration of PCA requires the selection of route, medication, and type of pump to use.

Routes: PCA administration can be through an intravenous catheter, epidural catheter, indwelling nerve catheter, or iontophoretic transdermal system. The equipment and procedure for placing these devices appear in the articles for those specific modalities.

Pumps: There are a variety of PCA pumps on the market, and all contain the essential components of a locking device, medication chamber, programming screen, and patient button. A provider inserts a syringe of medication into the pump and programs the pump to the prescribed initial loading dose, PCA dose, lockout interval, continuous infusion rate, and 1 and 4-hour limits. For intravenous PCA, the medication line connects to a fluid infusion line. It is best to familiarize yourself with your specific institution's pump and protocols for PCA administration.

Medications: Medications commonly used are opioids and local anesthetics. Opioids are either used alone for intravenous PCA or in conjunction with local anesthetics for epidural catheter PCA. 

Opioid medications include pure Mu opioid receptor agonists (morphine, fentanyl, hydromorphone, meperidine, sufentanil, alfentanil, and remifentanil), Mu opioid receptor agonist-antagonists (butorphanol, nalbuphine, pentazocine) and partial Mu opioid receptor agonists (buprenorphine, dezocine). Despite a variety of medication options, morphine remains the gold standard medication for intravenous PCA. 

Local anesthetics, including sodium channel blockers (bupivacaine, levobupivacaine, and ropivacaine), are primarily used for epidural catheters and indwelling nerve catheter PCA. 

Other medications can be added to intravenous PCA in an attempt to reduce side effects and improve pain control. They include ketamine, naloxone, clonidine, magnesium, ketorolac, lidocaine, and droperidol. Experiments with these additional medications have had a variety of efficacy, but the mainstay of PCA remains opioids and local anesthetics.[9][10][11]

Personnel

Multiple staff members are necessary to effectively and safely administer PCA. Individual roles include the physician ordering the route, medication, and dosing, the pharmacist preparing the drug, and the nurse setting up the pump and explaining its use to the patient while periodically monitoring them throughout their device use. Lastly, the patient is personally pressing the administration button.

Preparation

Before the administration of intravenous PCA, the patient needs pre-procedure assessments across a variety of domains, including cognitive, opioid naivety, pain, sedation, and respiratory assessments. A pre-procedure cognitive assessment ensures the patient has the mental capacity to participate in PCA and can understand the concepts of dosing, interval, lockout, and expected pain relief. Whether the patient is opioid naïve determines the initial dosing, titration, and expected pain relief and side effects. Periodic pain assessments using the numerical pain rating scale are necessary to create a baseline before PCA begins and to track its efficacy throughout treatment. A sedation assessment should also occur before the procedure begins and periodically throughout. Finally, a respiration assessment of the rate, depth, effort, and sound of breaths should be performed to establish a patient baseline and monitor the medications' effects during treatment. These assessments allow for adjustments to be made during administration to meet desired outcomes.[12][13]

Before the administration of PCA through a peripheral nerve catheter or an epidural catheter, a neurological exam assessing for pain sensation, light touch sensation, and motor function over the targeted dermatomes and myotomes requires assessment, allowing for the establishment of a baseline function and sensation to be tracked throughout PCA administration.

Technique or Treatment

PCA dosing contains a variety of variables, including the initial loading dose, bolus or demand dose, lockout interval, continuous infusion rate, and 1 and 4-hour limits. A nurse can titrate the initial loading dose to reach the desired medication's minimum effective concentration (MEC). The bolus or demand dose is the dose of medication delivered each time the patient presses the button. A lockout interval is a time after a demand dose in which a dose of medication is not administered even if the patient presses the button; this is done to prevent overdosing. A continuous infusion rate can be used in the background of PCA dosing to maintain the MEC of the medication independent of patient demands. One- and 4-hour limits put a cap on the maximum amount of medication allowed to be administered within those periods, which is usually less than the dose given if the patient were to press the dosing button at every possible interval. This mechanism allows for an added safety benefit. It can notify the nurse and provider that the patient’s pain is not under adequate control with the prescribed medication and dosing parameters.[14]

There is a variety of debate and discussion about different dosing strategies regarding PCA, such as how much of a loading dose to administer, which medications to use, the amount of drug in the demand dose, the duration of lockout interval, whether to add a continuous background infusion and what 1 and 4-hour maximums should be. It is best to review the specific literature on PCA dosing strategies for the pain condition you are attempting to treat with PCA.[15]

Complications

Common side effects and complications of PCA relate to the procedure's inherent mechanism and the medications involved. Complications of PCA pumps include “runaway” pumps, failure to use anti-reflux valves, incorrect syringe placement, PCA by proxy, and machine tampering.

Runaway pumps result from a mechanical error in which a pump malfunctions and delivers doses at incorrect intervals and amounts. This error can lead to a potentially fatal overdose. While this type of mechanical failure is rare, it is still essential to be aware that this type of complication exists, and patients require periodic monitoring for overdose symptoms. 

Anti-reflux valves prevent the opioid medication from flowing up into the intravenous fluid infusion line instead of the intended line that goes toward the patient. Failure to use an anti-reflux valve can result in refluxed medication into the fluid infusion line. This medication could then all be delivered to the patient at once if the intravenous line is flushed, resulting in an overdose. 

If the syringe containing the medication is damaged or incorrectly placed into the PCA machine, gravity could empty it, and the entire syringe of medication could be delivered to the patient immediately. To prevent this, lines should be cross-clamped when changing the syringe, and machines should be kept level to or below the intravenous catheter in the patient. Some devices are even equipped with anti-siphon valves to prevent this complication. 

PCA by proxy is when someone besides the patient is pressing the button to administer a dose because they believe the patient is in pain and needs it. This phenomenon has been documented to lead to respiratory depression. Patients, family members, visitors, and healthcare providers must understand the dangers of someone else pressing the button before PCA treatment modalities can commence.[16] 

To prevent tampering with PCA pumps, access to the medication and programming portion of the pump should only be permitted by a healthcare provider with a key or code to the pump. Therefore, any tampering with the machine or medication is evident. Devices should be routinely checked to ensure that their locking mechanisms have not been compromised.

Complications of epidural and indwelling nerve catheter PCA include infection, catheter dislodgement, medication leakage, skin irritation, allergic reaction, and short—and long-term nerve damage.[17][18] They can also include complications resulting from incorrect catheter placement, such as intravascular, intrapleural, intraneural, and intrathecal placement. Side effects of PCA administration can be related to the medications or the delivery device used and include nausea and vomiting, constipation, urinary retention, pruritus, respiratory depression, and local anesthetic toxicity.[19][20]

Clinical Significance

PCA has been proven to be more effective at pain control than non-patient-controlled opioid injections and results in higher patient satisfaction. PCA has also been found to be preferred by nurses because it allows for a reduction in their workload. PCA enables patients to have more control over their pain and helps them shift toward a more internal locus of control over their care.

PCA is less cost-effective than traditional dosing and does not affect the average length of hospital stay. When comparing PCA to traditional dosing, it was documented to result in higher opioid consumption. Still, those same studies also found no significant difference between opioid-related side effects, potentially indicating that the amount of opioid consumption is irrelevant.[21][22]

Enhancing Healthcare Team Outcomes

PCA can be an effective way to control acute, chronic, postoperative, and labor pain. However, it requires a competent interprofessional healthcare team consisting of a physician, pharmacist, nurse, and patient. Educating healthcare team members about the variety of routes, medications, dosing regimens, complications, pre-procedure and post-procedure assessments, side effects, and expected outcomes involved is essential. The pharmacist should double-check the dose and ensure the delivery rate is safe. The nurses should double-check the order and ensure the correct drug amount is delivered. The team can inspect the device's records and see if dosing has been optimal for patient pain control. While PCA can reduce the direct involvement of a physician and nurse in pain control, a supervisory role is still necessary to monitor the proper function and effectiveness of the PCA treatment and avoid undesired outcomes. The interprofessional team must communicate to achieve optimal pain control results and avoid poor outcomes.

Nursing, Allied Health, and Interprofessional Team Interventions

The nurses should monitor the patient carefully and frequently to assess pain and sedation levels every 1 to 2 hours for the first 24-48 hours because the patient is at the highest risk of hypoventilation and nocturnal hypoxemia during this time. Other routine opioid medications ordered for the patient should be avoided when the patient is using an opioid PCA. Nurses should assess for comfort using standard numeric or behavior scales and evaluate the number of patient demands for medication. Based on the patient's requirements, the dose of the PCA can be adjusted.

Nursing, Allied Health, and Interprofessional Team Monitoring

Nurses are responsible for placing peripheral intravenous lines, setting up PCA pumps, inserting medication into the pumps, and monitoring the patient’s pain, sedation, and respiration. They ensure that the pump is functioning correctly and that the medications are achieving their intended purpose while avoiding complications and reducing side effects.

While PCA can reduce the need to round and respond to patient calls to administer analgesics, it does not diminish their workload because of the time and effort needed to educate the patient, set up the machine, and monitor its effectiveness and side effects. However, it has been shown to be a preferred method because nurses and patients have more control over their work and pain.