AWHONN Advanced Fetal Monitoring Course

AWHONN Advanced Fetal Monitoring CourseDisclosureThe Instructors of this course report either conflicts of interests or relevant financial relationships, or lack thereof.

The nurse planners for this course report no conflicts of interests.DisclosureThe Instructors will be discussing an off-label use of the medication terbutaline but will not be discussing the off-label use of any medical devices.Course ObjectivesDescribe physiologic principles of maternal and fetal oxygen transfer and acid-base balance.Identify physiologic principles underlying fetal heart monitoring.Describe concepts in antenatal testing including analysis and interpretation of biophysical profiles and complex antenatal fetal heart monitoring tracings.Relate physiologic principles to the goals and interventions of antenatal testing.Evaluate interventions for patients undergoing antenatal testing.Course Objectives (cont.)Analyze fetal cardiac arrhythmia patterns and describe outcomes associated with these patternsAnalyze complex fetal heart monitoring patterns utilizing current NICHD/ACOG FHM terminology and categoriesApply perinatal risk management principles, communication techniques and documentation strategies related to complex and challenging patient care scenarios.Fetal OxygenationMaternal circulationUterine circulationPlacental circulationUmbilical circulationFetus

Maternal Transfer of Oxygen to FetusTransport from atmosphere to alveoliDiffusion across alveolar membraneTransport from lungs to placentaDiffusion across the placentaTransport from placenta to fetusDiffusion into fetal tissues

Adapted from Meschia, G. (1979). Supply of oxygen to the fetus. J Reproductive Medicine, 23, 160.Four Components of Oxygen TransportOxygen content

Oxygen affinity

Oxygen delivery

Oxygen consumption

Maternal Oxygen TransportMaternal oxygen content:The total amount of oxygen in the maternal arterial bloodAmount of oxygen dissolved in plasma (PaCo2)Percent of oxygen carried on the hemoglobin (SaO2)Maternal Oxygen Transport (cont.)PaO2 helps bind oxygen molecules to hemoglobin.

Saturated hemoglobin molecule carries four molecules of oxygen.

SaO2 is a more precise measure of oxygen content than PaO2Maternal Oxygen Transport (cont.)Oxygen affinity:Gain and release of oxygen molecules from hemoglobinCan change with variations in pH, CO2 or maternal temperatureReflected on oxyhemoglobin dissociation curveMaternal Oxyhemoglobin Dissociation Curve

Maternal Oxygen Transport (cont.)Oxygen delivery:Amount of oxygen delivered to the tissues each minuteTwo components are:Oxygen contentCardiac outputMaternal Oxygen Transport (cont.)Oxygen consumption:Amount of oxygen consumed by the body and tissues each minuteInterventions to Decrease Maternal Oxygen ConsumptionPromote maternal relaxationCoach with helpful breathing techniquesManage painMaintain acceptable uterine activity (in some cases decreasing uterine activity)Use antipyretics to reduce feverReposition the motherProvide appropriate management of second stage labor Fetal Oxygen TransportIncludes oxygen content, affinity, delivery, and consumptionIs directly dependent on maternal oxygen transportIs affected by:Blood flow to the uterus and placentaIntegrity of the placentaBlood flow through the umbilical cordFetal Oxygen Transport (cont.)Fetal oxygen content:Amount of oxygen dissolved in plasma (PaO2)Amount of oxygen carried on the hemoglobin (SaO2)Fetal PaO2 is approximately 30 mmHgAdult is 100 mmHgFetal Oxygen Transport (cont.)Fetal oxygen tension is bout 25% of an adultsFetal hemoglobin:Has an increased oxygen affinityHas a higher concentration than maternal (approximately 17 gm/dL at term)(Freeman et al., 2003; Harvey & Chez, 1997)Fetal Oxygen Transport (cont.)

Fetal Circulation

Fetal Oxygen Transport (cont.)Fetal oxygen consumption:Amount of oxygen consumed by the tissues each minuteFetal response to decrease oxygen consumption:Alteration in behavioral stateDecreased fetal movementChange in variabilityChange in reactivityFetal Response to Decreased OxygenRedistribution of blood to vital organs

Oxygen consumption decreases:Myocardium uses less oxygenChanges in FHR

Aerobic to anaerobic metabolismAerobic vs. Anaerobic MetabolismTechnology for Analysis of Fetal HypoxiaFetal ECG analysis

ST-segment analysisDefinitions of Key TermsBase deficit: HCO3 concentration lower than normalBase excess: HCO3 concentration higher than normalAcademia: concentration of hydrogen ions in the bloodAcidosis: concentration of hydrogen ions in the tissueDefinitions of Key Terms (cont.)Hypoxemia: oxygen content in blood

Hypoxia: level of oxygen in the tissue

Asphyxia: Hypoxia, acidemia, and metabolic acidosisNeonatal Encephalopathy and Cerebral PalsyNeonatal encephalopathy:A clinically defined syndrome of disturbed neurologic function in the earliest days of life in the term infant, manifested by difficulty with initiating and maintaining respiration, depression of tone and reflexes, subnormal level of consciousness, and often by seizures(ACOG, 2003, p. 84)Neonatal Encephalopathy and Cerebral Palsy (cont.)Four criteria define an acute intrapartum event sufficient to cause cerebral palsy(ACOG, 2003 p. xviii):Evidence of metabolic acidosis in fetal umbilical arterial blood obtained at delivery (ph