What monitors should be used when anesthetizing the pregnant patient?
In addition to the routine intraoperative monitors, the fetal heart rate and uterine tone should be monitored, if at all possible. Using a Doppler apparatus, fetal heart rate monitoring becomes feasible after the 16th week of pregnancy. An external tocodynamometer can be used if the uterus is at or above the level of the umbilicus. These monitors may be technically difficult or impossible to use during an intra-abdominal procedure or in an obese patient. It is important that someone proficient in fetal monitoring be present throughout the case to interpret the uterine/fetal tracings. Also, there should be a plan as to how to proceed in the event of fetal distress. Prior to 23–24 weeks gestation when the baby is not viable, optimization of the maternal condition, by increasing the blood pressure or increasing the inspired oxygen concentration, may improve the fetal condition. After 23–24 weeks gestation, in addition to attempts at correcting the intrauterine milieu, emergent cesarean section should be part of the plan. Fetal heart rate and uterine tone monitoring should continue into the postoperative period.