Fetal monitoring for anesthesiologists
Meyer-Breiting, P.; Leuwer, M.
Der Anaesthesist 41(1): 47-52
1992
ISSN/ISBN: 0003-2417 PMID: 1536440 Document Number: 404902
Several monitoring methods for the fetus are presented, the knowledge of which is appropriate for anesthesiologists active in the field of obstetrics. A distinction is made between external, indirect methods for monitoring when the amniotic sac is intact and internal, direct methods employed when the sac has ruptured. Particular emphasis is placed on cardiotocography (CTG), which is an obligatory method of routine monitoring during the late period of cervical dilatation and expulsion. It registers the reaction of fetal heart rate to parturition and labor, and represents a good indirect measure to both uteroplacental blood flow and fetal cardiac reserve. Criteria of evaluation for cardiotocograms are presented on the basis of guidelines elaborated by the Standard Committee on Cardiotocography (Chairman: Prof. Dr. H. Ruttgers). These enable the status of the fetus to be evaluated with differentiation. An inevitable sign of fetal well-being is a normal baseline with a rate between 120 and 160 beats/min, normal microfluctuation, and oscillations between 5 and 25/min with absent variable or late decelerations. Warning signs are restricted microfluctuation, elevated baseline, variable decelerations, and clinical passage of meconium. Suspicious signs are a baseline between 100-119 and 161-170 beats/min, respectively, decreased oscillation amplitude, and protracted decelerations over as much as 2 min. Unequivocally pathological are a baseline below 100 or above 170 beats/min, loss of microfluctuation, oscillations below 5/min, and variable or late decelerations in combination with one of these criteria or prolonged decelerations. If the CTG is normal, there is no contraindication from the obstetrical point of view to elective epidural anesthesia. If, however, the CTG is suspicious or unequivocally pathological, elective epidural anesthesia usually should not be performed due to the risk of deterioration of uteroplacental perfusion from cardiovascular side effects of the anesthetic. In exceptional cases, however, uteroplacental blood flow may be improved by precisely-dosed epidural anesthesia and close cooperation between an experienced anesthesiologist and the obstetrician. If in the presence of poor fetal status anesthesia for surgical delivery is required, epidural anesthesia should not be considered due to time factors.