Sun21November0452PM 15

A 24-year old man is admitted to the high dependency unit following an external fixation of a pelvic fracture sustained in a road traffic accident earlier in the day. He also has stable L2/L4 vertebral fractures but no other injuries.

He is known to be an intravenous drug abuser currently on 120 mg heroin per day. He has been admitted for postoperative observations and pain control. He has regular paracetamol and NSAIDs prescribed.

Which of the following is the most appropriate postoperative pain regimen?

(Please select 1 option)

Epidural with 20 mL 0.5% bupivacaine and 2 mcg/mL fentanyl and PCA morphine Incorrect answer selected

PCA morphine alone

Epidural with 20 mL 0.5% bupivacaine and 2 mcg/mL fentanyl

PCA morphine alone with background infusion This is the correct answer

Oral methadone titrated to effect

Explanation

This patient is probably dependent on and tolerant to opioids and is also likely to experience significant pain from his injuries. The issue is to provide adequate pain relief from a pure opioid agonist in combination with regular paracetamol and NSAIDs but at the same time avoid the chance of an acute withdrawal syndrome.

Opioid withdrawal can be avoided by administering a baseline dose of opioid that corresponds to the patient's usual opioid use in addition to opioids required to address the level of pain experienced. This is best managed by empowering the patient to use patient controlled analgesia (PCA). The infusion rate, bolus dose and lock-out time can be adjusted accordingly. Patients may have high and unpredictable opioid requirements. Using PCA also helps to avoid staff/patient confrontations about dose and dose interval.

For every 2.5 mg heroin the equivalent for morphine is 3.3 mg. The patient is normally on 120 mg of heroin per 24 hours. The equivalent dose of morphine is 48 × 3.3 =158 mg per 24 hours (6 mg/hour).

When patients are in remission then epidural or spinal opioids might be the best choice providing a systemic dose of opioids are maintained to avoid withdrawal. This patient has lumbar vertebral fractures, which would relatively contraindicate this route of analgesia.

Oral methadone titrated to response would not be the best choice for acute pain. Its long half life makes titration difficult and absorption of this drug by the gastrointestinal tract variable.

Answer Statistics

1

20%

2

6%

3

18%

4

42%

5

17%

Times answered: 267