A G2P1 at 38 weeks undergoes elective repeat cesarean section. During surgery, profuse hemorrhage occurs from the placental bed after delivery of a morbidly adherent placenta. Despite oxytocin, misoprostol, carboprost, and uterine compression sutures, bleeding persists. The internal iliac arteries are ligated bilaterally. The mechanism by which bilateral internal iliac artery ligation reduces uterine hemorrhage is:
- A Complete devascularization of the uterus
- B Reduction of pulse pressure in pelvic vessels, converting arterial to venous-pressure flow ✓
- C Reflex vasoconstriction mediated by the sympathetic nervous system
- D Thrombosis of the uterine arteries within 24 hours
Correct answer: B. Reduction of pulse pressure in pelvic vessels, converting arterial to venous-pressure flow
Explanation
Bilateral internal iliac (hypogastric) artery ligation works by reducing the pulse pressure in pelvic arterial vessels by approximately 85%, effectively converting the pulsatile arterial circulation to a venous-pressure system. This facilitates clot formation and haemostasis at the bleeding points. The uterus is not completely devascularized because of extensive collateral anastomoses (ovarian, inferior mesenteric, lateral sacral vessels); hence future fertility is preserved and the uterus survives.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.