Post-Op Pain

Question 1

What are the consequences of poor pain control?

Answer 1

Inadequate control of post-operative pain results in a slower recovery

• Patients with poorly controlled pain are often reluctant to mobilise, in turn resulting in a slower restoration of function and rehabilitation capacity
• Patients in pain following abdominal surgery will not breathe as deeply as they normally would, resulting in inadequate ventilation and subsequent atelectasis and hospital-acquired pneumonia

Question 2

Briefly describe the WHO Pain Ladder

Answer 2

The World Health Organisation Analgesic Ladder is the best-known method for approaching pain relief. It provides a strategy for titrating analgesia, starting with simple analgesics and working upwards to strong opioids. After implementing a regime, the patient should always be reviewed shortly after to assess adequacy.

Initially starting with simple analgesics (such as paracetamol or NSAIDs), if the pain is not well controlled, move up to the next stage of the ladder and consider prescribing weak opiates, such as codeine or tramadol. Again, assess the response and if this is still inadequate, move to the next step and prescribe morphine or other strong opiates.

Consider alternatives to the oral route, such as topical, intravenous, or subcutaneous. If this fails and sinister causes of pain have been ruled out, consider specialist help and/or a patient-controlled analgesia pump. Any neuropathic pain may respond better to alternative analgesics (see appendix), such as amitriptyline or gabapentin.

As patients recover, it is important to move down the ladder, and wean down the analgesia to a more simple regime. It is always preferable to not send patients home with strong opiates.

Question 3

Briefly describe the steps of WHO Pain Ladder

Answer 3

Question 4

What are the simple analgesics?

Answer 4

Non-opioid analgesia consists of paracetamol and/or NSAIDs (e.g ibuprofen or diclofenac).

Question 5

What is the mechanism of action of NSAIDs?

Answer 5

NSAIDs work by inhibiting the synthesis of prostaglandins, thereby reducing the potential inflammatory response causing the pain. These anti-inflammatory properties mean such analgesics are often used in musculoskeletal conditions. They are also frequently used intra-operatively.

Question 6

What are the side effects of NSAIDs?

Answer 6

The side effects of NSAIDs include (a useful mnemonic is I-GRAB):

• Interactions with other medications (such as Warfarin)
• Gastric ulceration (consider adding a PPI when prescribing NSAIDs long-term)
• Renal impairment (use NSAIDs sparingly in those with poor renal function)
• Asthma sensitivity (triggers 10% of individuals with asthma)
• Bleeding risk (due to their effect on platelet function)

Question 7

What is the mechanism of action of opiates?

Answer 7

Opiates are divided into weak opiates, such as codeine, or strong opiates, such as morphine, oxycodone, or fentanyl. They work by activating opioid receptors (MOP, DOP, and KOP), which are distributed throughout the central nervous system.

Question 8

What are the side effects of opiates?

Answer 8

These medications have a significant side effect profile; most patients will experience a degree of constipation and nausea. Thus, laxatives and anti-emetics should be prescribed concurrently.

Other side effects include sedation or confusion, respiratory depression, pruritus, and tolerance and dependence (both of the latter are relatively rare).

Question 9

Give examples of prescribing tips for analgesia

Answer 9

• If regular opiates are needed, always prescribe concurrent regular paracetamol to reduce their requirement
• Avoid weak and strong opiates in combination, as they competitively inhibit the same receptor to varying degrees
• If PRN (‘as needed’) opiates are frequently called for, assess the 24-hour opiate requirement and consider titration into a regular basal dose of modified-release preparations.
• If opioid analgesia is required in a patient with renal impairment, consider using oxycodone or fentanyl rather than morphine
• If the oral route is contraindicated, consider topical patches and use IV morphine for breakthrough analgesia, as the bioavailability of oral morphine is 30% whereas it is 80% for IV or SC morphine

Question 10

What is Patient Controlled Analgesia?

Answer 10

Post-operatively, many patients require more intense or immediate analgesia and their requirements exceed the capacity of nursing staff to provide. In such situations, patient controlled analgesia (PCA) can be used.

PCA involves the use of intravenous pumps that provide a bolus dose of an analgesic when the patient presses a button. These are started in theatre (based on clinical experience of analgesia requirements of the specific operation by the surgical staff) or on the wards (often when strong opiates are inadequate).

Question 11

What are the advantages of Patient Controlled Analgesia?

Answer 11

• Provides analgesia that is tailored to the patient’s requirements
• Safe, as the risk of overdose is negligible
• Can accurately record how much opioid is being administered, which can be converted to a regular dose if required

Question 12

What are the disadvantages of Patient Controlled Analgesia?

Answer 12

• Can be cumbersome and prevent the patient mobilising
• Not appropriate for those with poor manual dexterity or severe learning difficulties

Question 13

Briefly describe the management of neuropathic pain

Answer 13

The management of neuropathic pain can be split into pharmacological and non-pharmacological methods. In many cases a combination of both approaches offers the best results:

• Non-pharmacological treatment
  
  • Cognitive behaviour therapy
  • Transcutaneous electric nerve stimulation (TENS)
  • Capsaicin cream (typically for localised pain)
• Pharmacological therapies
  
  • Gabapentin
  • Amitriptyline
  • Pregabalin