Patient controlled analgesia:
PCA is a unique way of administering pain medications. The medication is administered with the help of a pump. Patient has the freedom to control the amount and dose of the pain medication. The response time is minimal compared to intermittent administration by a nurse. Pain relief is achieved faster and satisfaction rates are higher. Any patient with basic understanding skills can benefit from the use of PCA. It has been used successfully in pediatric as well as geriatric populations. It has been used for hospital inpatients as well as ambulatory and home/ hospice use.
Common indications for PCA:
- Post-operative pain
- Severe acute pain
- Acute exacerbations of chronic pain
- Cancer pain
- Patients unable to take oral medications
- Poor understanding of the PCA
- Poor health care support for PCA
Routes: I.V. PCA and epidural (PCEA). Other routes are intrathecal / transdermal (E-Trans) / surgical incisional (On-Q pumps) / intra-articular (On-Q pumps) etc.
Drugs commonly used:
- Opioids: Morphine, Fentanyl and Hydromorphone
- Local anesthetics: Bupivacaine and Ropivacaine.
- Other drugs: Clonidine, Baclofen etc.
- Various combinations of the above drugs to achieve synergistic effect and to minimize side effects.
- Concentration: The amount of the drug per ml of the solution. For example morphine concentration is 1 or 5 mg/ml.
- Total amount: 30 ml for IV pumps and 250 ml for epidural pumps.
- Loading dose: The dose given in frequent intervals to load the receptors and decrease severe pain. For example ‘morphine 2 mg q 5 minutes to a maximum of 20 mg’. Opioid tolerant patients will obviously need more. Individual titration is essential.
- Patient dose or demand dose: The dose provided by the pump when the patient presses the ‘button’. This obviates the need to call the nurse each time. For example morphine 2 mg. Opioid tolerant patients and patients in severe pain with movement (dynamic pain or incidental pain) may need more.
- Lockout interval: The time interval before the pump can provide the next dose. It is a safety feature. For example ‘morphine 2 mg every 10 minutes’ means that 10 minutes should pass before the pump can provide another dose of morphine. If the pain is not well controlled then the lockout interval may be decreased.
- Basal rate: Basal rate is the amount of drug given as a continuous infusion and is set per hour. For example ‘morphine 2 mg per hour’. Basal rate is useful in opioid tolerant patients, patients with severe rest pain and for nighttime analgesia. Obviously monitoring is essential to detect respiratory depression. Basal rate should NOT be initially used in opiate naïve patients.
- 1 or 4 hour limit: There is 4-hour limit with the IV PCA and 1-hour limit with epidural PCA (PCEA). The limit means that the pump can provide only the amount set within the time frame. The amount includes both the basal rate and the demand doses. The limit may be set lower for patients with multiple co-morbid conditions and set higher for opioid tolerant patients. This is again a safety feature and needs to be titrated on an individual basis and frequent re-assessments.
The PCA is used for as long as it is practical and tolerated. At the time of transition to other routes of use (most commonly oral medications) patients should be re-assessed and needs for analgesics reviewed. The last 12- or 24- hour requirements are noted and equiv.-analgesic conversions made for the alternate drugs and alternate routes. In general oral form of morphine is 3 times higher than the i.v form. 2/3rds of the total dose is given in a sustained release form for basal analgesia and 1/3rds as rescue medication for breakthrough pain. For example if the last 24-hour dose was 15 mg of morphine i.v, then oral morphine requirements would be 45 mg. Morphine ER (extended release) 15 mg po bid and Morphine IR (immediate release) 15 mg po prn q 4 hourly would be appropriate. If the patient needs too frequent rescue doses then the dose of the sustained release form should be increased. Rest pain is better controlled with sustained release forms and incidental pain is better controlled with immediate release forms.
Opioids should be combined with NSAIDs, pain adjuvants and modalities whenever possible. Rapid tapering of the opioids (25% less every day) is essential once the pain condition improves.
Complications and side effects of PCA:
- Side effects of opioids: respiratory depression, sedation, nausea, vomiting, itching, urinary retention and constipation. Most of the side effects improve with time except constipation that needs aggressive bowel program as soon as possible.
- Side effects of local anesthetics: hypotension, motor weakness, numbness and urinary retention.
- Pump issues: pump malfunction, catheter dislodgement, disconnections, kinking and infection.
NOTE: Patients, family, staff should all be informed that only the patient should press the PCA button.
Please refer to pain management guidelines in the clinical protocols of Loyola EMR for further details.