Patient Controlled Analgesia

• Simple regular analgesia - paracetamol
• NSAIDs where not contraindicated - we don’t use these enough
• Weak opioids - codeine
• Strong opioids - oral, IM, IV, PCA
• Adjuncts - gabapentin, amitriptyline
• Miscellaneous - lidocaine, ketamine, clonidine
• Regional analgesia
• Neuraxial analgesia

• Nausea
• Vomiting
• Hallucination or confusion
• Respiratory depression
• Pruritus
• Constipation

Make sure you also prescribe a laxative, chlorphenamine and naloxone PRN.

• Rapid strong analgesia on demand
• Gives the patient control and they don’t have to wait for the nurse to be free
• Reduced work load for nursing staff
• No painful IM or SC injections

Do not underestimate just how powerful a sense of control can be for improving a patient's pain. Simply knowing that they can press it whenever they need often has a placebo effect all by itself.

• Confirm patient identity and indication
• Rule out allergies and contraindications - renal failure and morphine etc
• Explain it to the patient, ideally with written information as well
• Check the patient is capable of understanding and using the button
• Ensure dedicated IV access
• Prescribe PRN oxygen, naloxone, chlorphenamine, laxatives
• Choose a PCA drug (morphine, fentanyl, ketamine, oxycodone)
• Select the dosing regime needed
• Sign the relevant documentation to ensure correctly set up, and watch patient administer first dose
• Monitor for adverse reactions

This is weirdly high yield in the exam, they really want to check that you understand the detailed set up protocol, because this is what makes it safe and effective.

• The idea is simple negative feedback - when the patient is in pain, they press for more analgesia, and when they’re comfortable, they don’t
• This naturally prevents over and under dosing and ensures a safe therapeutic level is maintained
• Different patients need different amounts, and a PCA pump allows the individual to titrate to their own requirements
• It is a computerised, battery powered and programmable pump that stores user data using a microprocessor
• When the pump is pressed, a predetermined dose of drug is administered through a dedicated intravenous line
• A time then locks the pump for a set duration, to prevent the patient from overdosing by administering too frequently

There are two options:

• Bolus only, with lockout in between
• Background infusion with boluses for breakthrough pain

The duration of the lockout should approximate the time to peak drug effect to prevent dose stacking.

Background infusions of intravenous opioids are usually reserved for the hallowed grounds of HDU and ICU.

• The drug bag should be a dedicated PCA mixture at a set concentration designed only for PCA use
• The pre-programmed infusion regimes are double checked by the user prior to starting
• The pump will not give more than 85-90% of the volume of the bag, to prevent venous air embolism
• One way valves to prevent venous back flow
• Dedicated cannula
• Pumps have alarms for occlusion, air bubbles or empty bag
• The pump case should be lockable to prevent others tampering with the drug

• Bolus dose
• Lockout interval
• Dose limits
• Infusion rates

Usually these are pre-programmed into a given protocol that you select for whatever bag of drug you're plumbing into the pump.

• Elderly patients
• Obstructive sleep apnoea
• Concurrent sedatives/opioids
• Hypovolaemia
• Renal failure - use fentanyl rather than morphine

• There should be a specific PCA monitoring proforma to adhere to
• Sedation scoring and respiratory rate monitoring to monitor for opioid overdose
• Patient may need O2 therapy while on PCA
• Call the pain team or anaesthetist on call if any issues

Sedation precedes respiratory depression and is a better indicator of opioid toxicity than respiratory rate.

• Morphine 0.5 - 2mg with 5 - 10 minute lockout
• Fentanyl 10 - 50 mcg with 5 - 10 minute lockout
• Oxycodone 0.5 - 1 mg with 5 - 10 minute lockout
• Pethidine 5 - 20 mg with 5 - 15 minute lockout

You could also mention remifentanil which is increasingly available on labour ward as a 20 - 40 mcg bolus every 2 minutes. This is such short-acting analgesia that it's only really helpful for contraction pain so it isn't used anywhere else in the hospital.

• Patients with dementia or delirium who lack capacity to use it properly
• Very young patients (unless supervised appropriately)
• Patients at risk of abuse where others may press the button for them

• Epidural
• Peripheral nerve catheter
• Subcutaneous
• Transdermal

These are specifically the 'push button to get a dose of drug' PCAs. You could also mention the examples we mentioned at the beginning where the patient determines how much pain relief they receive.