Stereological Study On Human Placenta In Different Measures For Prevention And Treatment Of Hypotension During Spinal Anesthesia For Cesarean Section

Objectives:To observe the effects of Ephedrine and pre-anesthetic volume expansion with Voluven on the maternal hemodynamics and fetal blood gas undergoing spinal anesthesia for cesarean section, and to evaluate the effects of placental villus by the variety of vascular density, the aim of study was to search for the best way to prevent and cure the hypotension.Methods:Singleton full-term pregnant women undergoing elective cesarean delivery were randomly allocated to two groups(20 in each):groupⅠ(Ephedrine group):Ephedrine was administered 6mg q 2 min(up to 18mg) after spinal anesthesia; groupⅡ(Voluven group):each of them received 10mL/(kg·h) of Voluven within 20 min before spinal anesthesia, and then 5mL/(kg·h) to maintain. With the patients in the left lateral position, spinal anesthesia was performed at the L2-3,0.5% bupivacaine 1.6mL was administered within 30-40s, and then patients were tilted to a 30°left lateral supine position, Oxygen was administered to all patients via nasal prongs at 4 L/min. The changes of blood pressure and heart rate were monitored and recorded, meanwhile comparisons of these umbilical arterial blood gas variables were made between two groups. After that, Apgar scores of the new-borns were recorded.40 samples were collected in this study, the staining intensity and distribution in these placental samples by image analysis technique, and a stereological study on the full-term placental villous capillary were evaluated with anti CD34 as the labeled vascular endothelial cells.Results:The umbilical artery PaCO2, PaO2 and Apgar scores were no significant differences between two groups(P>0.05). The heart rate, hypotension and the lactic acid value in groupⅠwere significantly higher than the groupⅡ(P<0.05). The umbilical artery pH in groupⅠwas significantly lower than the groupⅡ(P<0.05). Almost all villous capillaries of placental villus were stained by CD34, the length density of villous capillaries was insignificantly changed between two group(P＞0.05), while the volume density of villous capillaries in groupⅡwas significantly decreased than the groupⅠ(P＜0.05).Conclusion:Pre-anesthetic volume expansion with Voluven can not only maintain stable hemodynamics during spinal anesthesia but also efficiently improve tissue perfusion of blood, microcirculation and uteroplacental blood flow, simultaneously increase supplement of oxygen to the fetus.