Uterine blood flow is consistently decreased after the administration of which regimen?

Uterine blood flow is consistently decreased after the administration of which regimen?

• A. Thiopental 4 mg/kg bolus and 1 mg/kg succinylcholine followed by intubation.
• B. 0.5-1.5 minimum alveolar concentration (MAC) of desflurane.
• C. Epidural fentanyl, uncomplicated by hypotension.
• D. Clonidine 300 mcg epidurally, uncomplicated by hypotension.

Answer: (A)

Uterine blood flow depends largely on the driving perfusion pressure from the mother’s circulation and the tone of the uterine vessels. Anesthetic regimens that reduce maternal blood pressure or increase uterine vascular resistance tend to decrease uterine blood flow. The induction regimen described—a thiopental bolus with a sux dose followed by intubation—tends to cause a notable drop in systemic blood pressure due to decreased vascular tone and myocardial depression. That fall in perfusion pressure reduces uteroplacental blood flow, so uterine blood flow is consistently decreased with this combination. The act of intubation can add a brief catecholamine surge, but the overall effect during induction is reduced perfusion pressure, which lowers uterine blood flow. In contrast, the desflurane range given can lower blood pressure but its effect on uterine blood flow is more variable and often not as consistently depressing. Epidural fentanyl that does not cause hypotension leaves hemodynamics intact, and clonidine given epidurally without hypotension tends to preserve or even improve uterine perfusion by avoiding a drop in maternal pressure.

Uterine blood flow depends largely on the driving perfusion pressure from the mother’s circulation and the tone of the uterine vessels. Anesthetic regimens that reduce maternal blood pressure or increase uterine vascular resistance tend to decrease uterine blood flow.

The induction regimen described—a thiopental bolus with a sux dose followed by intubation—tends to cause a notable drop in systemic blood pressure due to decreased vascular tone and myocardial depression. That fall in perfusion pressure reduces uteroplacental blood flow, so uterine blood flow is consistently decreased with this combination. The act of intubation can add a brief catecholamine surge, but the overall effect during induction is reduced perfusion pressure, which lowers uterine blood flow.

In contrast, the desflurane range given can lower blood pressure but its effect on uterine blood flow is more variable and often not as consistently depressing. Epidural fentanyl that does not cause hypotension leaves hemodynamics intact, and clonidine given epidurally without hypotension tends to preserve or even improve uterine perfusion by avoiding a drop in maternal pressure.