Ketamine's effect on uterine tone is:

Ketamine's effect on uterine tone is:

• A. Dose-dependent decrease in tone
• B. Dose-dependent increase in tone during the second trimester but not at term
• C. No effect on tone
• D. Always decreases tone

Answer: (B)

The key idea is that how ketamine affects uterine tone depends on where you are in pregnancy, because the uterine muscle’s responsiveness changes with hormonal milieu and receptor availability as gestation progresses. Ketamine elevates sympathetic activity and circulating catecholamines, which can stimulate uterine contractions. In the second trimester, the myometrium is more responsive to such stimulatory input, so increasing the ketamine dose tends to raise uterine tone in a dose-dependent way. By term, the hormonal environment (estrogen, progesterone, oxytocin, prostaglandins) and receptor patterns that drive labor dominate, so ketamine’s additional sympathetic stimulation no longer produces a noticeable increase in tone. That’s why the best answer describes a dose-dependent increase in uterine tone during the second trimester but not at term.

The key idea is that how ketamine affects uterine tone depends on where you are in pregnancy, because the uterine muscle’s responsiveness changes with hormonal milieu and receptor availability as gestation progresses. Ketamine elevates sympathetic activity and circulating catecholamines, which can stimulate uterine contractions. In the second trimester, the myometrium is more responsive to such stimulatory input, so increasing the ketamine dose tends to raise uterine tone in a dose-dependent way. By term, the hormonal environment (estrogen, progesterone, oxytocin, prostaglandins) and receptor patterns that drive labor dominate, so ketamine’s additional sympathetic stimulation no longer produces a noticeable increase in tone. That’s why the best answer describes a dose-dependent increase in uterine tone during the second trimester but not at term.