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Chapter 68. Intravenous Patient-Controlled Analgesia

Which statement is correct regarding the site of action of opioids?

A. The mechanism of action for opioids is only via the mu-receptors of the central nervous system.

B. Pure agonists are the most useful for acute pain.

C. Agonist-antagonist opioids act as a kappa antagonist and a mu-receptor agonist.

D. Partial agonists have a major role for analgesia.

B is correct. Pure agonists are the most useful for acute pain because of their complete mu binding.

A is incorrect. They also act via receptors in the peripheral nervous system.

C is incorrect. Agonist-antagonist opioids act as a kappa agonist and mu-receptor antagonist.

D is incorrect. Because they only have partial mu-receptor binding, pure agonists have a significant ceiling effect.

Which statement is correct regarding patient-controlled analgesia (PCA) for acute post-operative management?

A. Morphine is the best analgesic for PCA.

B. In at least 0.5% of the cases, PCA gives respiratory depression.

C. The fentanyl patch has a comparable effect to PCA, and therefore is a good choice in acute pain.

D. PCA is cost-effective through savings on nursing costs.

D is correct. It does reduce demand on the nursing staff, who are required for delivery of IV or IM PRN analgesics. This reduced workload of the nursing staff may indeed have a cost benefit. There is no apparent decrease in cost.

A is incorrect. There is no standard opioid. Patient characteristics will influence choice of opioid.

B is incorrect. All side effects together are less than 0.5%.

C is incorrect. Patches have a good indication for chronic cancer pain but none in acute pain.

Which statement is true regarding improving patient-controlled analgesia (PCA) effect?

A. Nonsteroidal anti-inflammatory drugs (NSAIDs), cyclo-oxygenase (COX)-2 inhibitors, and acetaminophen all have an opioid-sparing effect.

B. NSAIDs, COX-2 inhibitors, and acetaminophen reduce opioid-induced side effects.

C. Ketamine infusions should be avoided perioperatively because of the increased risk of hallucinations.

D. Association of lidocaine has an opioid-sparing effect.

A is correct. Several meta analyses suggest that the use of nonsteroidal anti-inflammatory drugs (NSAIDs), cyclo-oxygenase (COX)-2 inhibitors, and acetaminophen all have an opioid-sparing effect.

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