tailieunhanh - Critical Care Obstetrics part 22

Critical Care Obstetrics part 22 provides expert clinical guidance throughout on how you can maximize the chances of your patient and her baby surviving trauma. In this stimulating text, internationally recognized experts guide you through the most challenging situations you as an obstetrician are likely to face, enabling you to skillfully:Recognize conditions early-on which might prove life threatening, Implement immediate life-saving treatments in emergency situations, Maximize the survival prospects of both the mother and her fetus | Cardiopulmonary Bypass Fetal Heart Rate Figure Fetal heart rate as related to maternal hemodynamics during cardiopulmonary bypass. 1 induction of anesthesia 2 ventilatory rate adjustment 3 median sternotomy 4 pericardotomy 5 heparin administration 6 aortic cannulation and manipulation of the heart 7 scopolamine and pancuronium administration 8 start of cardiopulmonary bypass 9 fall in maternal blood pressure and FHR with start of non-pulsatile flow 10 cardiopulmonary bypass discontinued. Reproduced by permission from Levy DL Warriner RA Burgess GE. Fetal response to cardiopiulmonary bypass. Obstet Gynecol 1980 56 112-115. 60 40 20 0 . Maternal Systolic Blood Pressure ---- Maternal Diastolic Blood Pressure .-k Mean Perfusion Pressure 200-1 180160 - 140 120100 10 12 3 4 56 7 89 23 TIME HRS 200 180 160 140 120 100 80 60 40 20 0 hypothermia resulting in fetal bradycardia fetal hypoxia from hemodilution acutely decreasing the maternal oxygen content and uterine contractility at the onset of CPB increasing the uterine vascular resistance and decreasing placental sufficiency 45 . Whatever the cause of the initial fetal bradycardia seen with initiation of CPB many reports indicate that FHR directly correlates with perfusion throughout CPB such that when flow rate is increased the FHR is restored 19 38 46-50 . Thus when the fetus is beyond about 25 weeks gestational age most anesthesiologists monitor fetal heart rate throughout CPB and attempt to establish adequate flow to maintain a normal FHR 110-160bpm . Temperature manipulation during hypothermic CPB has also been thought responsible for the FHR changes 45 . It has been known for some time that maternal temperature change results in fetal heart rate changes with hyperthermia causing fetal tachycardia and hypothermia causing fetal bradycardia as shown in Figure 51 . However multiple cases of normothermic CPB demonstrate the characteristic initial bradycardia and post-CPB tachycardia sustaining the theory that .