True statements regarding intrathecal morphine, fentanyl, or sufentanil in obstetric anesthesia include all EXCEPT which?

True statements regarding intrathecal morphine, fentanyl, or sufentanil in obstetric anesthesia include all EXCEPT which?

• A. The chief site of action is the substantia gelatinosa of the dorsal horn
• B. There is no motor blockade
• C. There is no sympathetic blockade
• D. Pain relief is adequate for the second stage of labor

Answer: (D)

Innate concept: intrathecal opioids provide targeted spinal analgesia by activating mu receptors in the dorsal horn, mainly at the substantia gelatinosa, to dampen nociceptive transmission without affecting motor pathways or causing significant sympathetic blockade at analgesic doses. The chief site of action is the substantia gelatinosa of the dorsal horn, where opioid receptors modulate incoming pain signals from the spinal cord to the brain. This explains why analgesia is achieved without broad disruption of motor function or autonomic tone. There is no motor blockade at typical obstetric analgesic doses because these opioids primarily act on the small-diameter nociceptive pathways in the dorsal horn rather than on the motor pathways that control movement. There is no sympathetic blockade with intrathecal opioids alone, since their effect is confined to spinal nociceptive processing and does not produce the extent of autonomic blockade that a neuraxial local anesthetic would. Pain relief is adequate for the second stage of labor is not generally true; while intrathecal opioids help with visceral pain and can provide substantial analgesia earlier in labor, the intense somatic pain of the second stage (perineal distension and stretching) often requires additional analgesia or adjunctive regional techniques for complete relief. So the statement that is not true is that pain relief is adequate for the second stage.

Innate concept: intrathecal opioids provide targeted spinal analgesia by activating mu receptors in the dorsal horn, mainly at the substantia gelatinosa, to dampen nociceptive transmission without affecting motor pathways or causing significant sympathetic blockade at analgesic doses.

The chief site of action is the substantia gelatinosa of the dorsal horn, where opioid receptors modulate incoming pain signals from the spinal cord to the brain. This explains why analgesia is achieved without broad disruption of motor function or autonomic tone.

There is no motor blockade at typical obstetric analgesic doses because these opioids primarily act on the small-diameter nociceptive pathways in the dorsal horn rather than on the motor pathways that control movement.

There is no sympathetic blockade with intrathecal opioids alone, since their effect is confined to spinal nociceptive processing and does not produce the extent of autonomic blockade that a neuraxial local anesthetic would.

Pain relief is adequate for the second stage of labor is not generally true; while intrathecal opioids help with visceral pain and can provide substantial analgesia earlier in labor, the intense somatic pain of the second stage (perineal distension and stretching) often requires additional analgesia or adjunctive regional techniques for complete relief.

So the statement that is not true is that pain relief is adequate for the second stage.