The effect of amniotic fluid on the human omental artery in vitro

OBJECTIVE: The aim of the study was to determine the effect of amniotic flu id on the in vitro contractility of the human omental artery. STUDY DESIGN: Amniotic fluid and a segment of omentum were obtained from ea ch of 5 patients at the time of planned cesarean delivery at normal term ge station for the indication of previous cesarean delivery. The omental arter y was cleaned and cut into 3-mm rings, which were placed in 10-mL organ cha mbers for isometric tension recording. The chambers were filled with Krebs- Henseleit solution bubbled with 5% carbon dioxide in air and maintained at 37 degrees C, pH 7.4. The rings were then equilibrated at 1 g passive tensi on for 90 minutes. The amniotic fluid was centrifuged for 10 minutes at 300 0 rpm to remove all debris. Increasing volumes of supernatant (10-2000 mu L ) were added to the omental artery rings at baseline tone or after contract ion with U46619 (10(-7) mol/L) or potassium chloride (60 mmol/L) to detect contractile and relaxant effects, respectively. Time-solvent control prepar ations were also run in parallel. RESULTS: Amniotic fluid had no effect on the basal tone of omental artery r ings. Amniotic fluid had no effect on the tension in rings previously contr acted with either U46619 or potassium chloride. CONCLUSIONS: Amniotic fluid has no direct effect on isolated human omental artery. The catastrophic hemodynamic changes associated with the syndrome o f amniotic fluid embolism are not due to a direct effect of circulating amn iotic fluid on vascular tone but rather may be due to secondary responses.