Intrapartum Fetal Heart Rate Monitoring: A Standardized Approach to Management

Transcription

1 CLINICAL OBSTETRICS AND GYNECOLOGY Volume 54, Number 1, r 2011, Lippincott Williams & Wilkins Intrapartum Fetal Heart Rate Monitoring: A Standardized Approach to Management DAVID A. MILLER, MD Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Children s Hospital Los Angeles, California Abstract: Recent advances in standardized fetal monitoring nomenclature and interpretation make it possible to construct a standardized approach to intrapartum fetal heart rate management that is evidence-based and reflects consensus in the literature. Key words: fetal monitoring, definitions, interpretation, metabolic acidemia, fetal heart rate decelerations A Standardized Management Decision Model Recent advances in standardized fetal monitoring nomenclature and interpretation make it possible to construct a Correspondence: David A. Miller, MD, Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Children s Hospital Los Angeles, 1300 North Vermont Avenue, Doctors Tower Suite 301, Los Angeles, CA. dmiller@usc.edu standardized approach to intrapartum fetal heart rate (FHR) management that is evidence-based and reflects consensus in the literature. 1 9 The benefits of standardization are addressed in detail elsewhere in this symposium. A common misconception is that standardized FHR management is a one-size-fits-all approach that removes individual clinical judgment and dictates the timing and method of delivery. On the contrary, standardized intrapartum FHR management is intended to encourage individual clinical judgment and to serve as a systematic reminder of potential sources of preventable error in effort to optimize outcomes and minimize medicolegal risk. The model described in this chapter uses the standardized FHR definitions and categories proposed by the National CLINICAL OBSTETRICS AND GYNECOLOGY / VOLUME 54 / NUMBER 1 / MARCH

2 Intrapartum Fetal Heart Rate Management 23 Institute of Child Health and Human Development (NICHD) in It does not include adjunctive tests of fetal status such as, fetal scalp blood sampling, fetal pulse oximetry, and fetal ST-segment analysis that are currently unavailable for general clinical use in the United States. These techniques are presented in detail elsewhere in this symposium. Standard of Care The standard of care mandates that practitioners provide patient care that is reasonable and prudent. Reasonableness, in turn, is determined by factual accuracy and the ability to articulate a thoughtful plan. Standard definitions and interpretation help to ensure factual accuracy. A standardized approach to management provides a framework for structured, evidence-based planning that can minimize variation, minimize potential error, and very importantly, that can be articulated. Confirm FHR and Uterine Activity Reliable information is vital to the success of intrapartum FHR monitoring. Therefore, the first step is to confirm that the monitor is recording the FHR and uterine activity accurately (Fig. 1). If external monitoring is not adequate for definition and interpretation, a fetal scalp electrode and/or intrauterine pressure catheter might be helpful. It is essential to distinguish between maternal and FHRs. Evaluation of 5 FHR Components Thorough, systematic evaluation of a FHR tracing includes assessment of uterine FIGURE 1. Standardized intrapartum fetal heart rate management model.

3 24 Miller TABLE 1. Three-tier FHR Classification System Category I FHR tracings include all of the following: Baseline rate: bpm Baseline FHR variability: moderate Accelerations: present or absent Late or variable decelerations absent Early decelerations present or absent Category II Includes all FHR tracings not categorized as category I or category III Category III FHR tracings include Absent baseline FHR variability and Recurrent late decelerations Recurrent variable decelerations Bradycardia Sinusoidal pattern Adapted with permission from Obstet Gynecol. 2008;112: bpm indicates beats per minute; FHR, fetal heart rate. contractions along with the 5 FHR components defined by the NICHD: baseline rate, variability, accelerations, decelerations, and changes or trends in the tracing over time. The 2008 NICHD consensus report defined 3 categories of FHR tracings (Table 1). 8 If all FHR components are normal (category I), the FHR tracing reliably predicts the absence of fetal metabolic acidemia and ongoing hypoxic injury. In low-risk patients, American College of Obstetricians and Gynecologists (ACOG) Practice Bulletin 106 and ACOG-American Academy of Pediatrics Guidelines for Perinatal Care recommend that the FHR tracing should be reviewed at least every 30 minutes during the active phase of the first stage of labor and at least every 15 minutes during the second stage. 9,10 In high-risk patients, the FHR tracing should be reviewed at least every 15 minutes during the first stage of labor and at least every 5 minutes during the second stage. Nursing documentation should comply with hospital policies and procedures. ACOG Practice Bulletin Number 106 Guidelines recommend that provider documentation should be performed periodically. The ABCD Approach to FHR Management If assessment of all 5 FHR components indicates that the tracing is not category I, further evaluation is warranted. A practical, systematic ABCD approach to management is summarized in Table 2. (A) Assess the oxygen pathway and consider other causes of FHR changes: Rapid, systematic assessment of the pathway of oxygen transfer from the environment to the fetus can identify potential sources of interrupted oxygenation (Table 2). In addition, a number of factors can influence the appearance of the FHR tracing by mechanisms other than interruption of fetal oxygenation. If the FHR changes are thought to be due to any cause not directly related to fetal oxygenation (Table 3), individualized management is directed at the specific cause. (B) Begin corrective measures as indicated: At each point along the oxygen pathway, conservative corrective measures are initiated, if indicated, to optimize oxygen delivery (Table 2). Initiation of corrective measures should be guided by individual clinical judgment. For example, amnioinfusion may be appropriate in the setting of variable decelerations, but would not be expected to result in resolution of late decelerations. A systematic approach does not mandate that all of these measures are used. It simply helps to ensure that important conservative corrective measures are considered and decisions are made in a timely manner. Reevaluate the FHR Tracing If, on reevaluation, the FHR tracing returns to category I, continued surveillance is appropriate. If the FHR tracing progresses to category III, delivery usually is

4 Intrapartum Fetal Heart Rate Management 25 TABLE 2. ABCD Fetal Heart Rate Management A B C D Lungs Heart Assess Oxygen Pathway Airway Breathing Heart rate and rhythm Cardiac output Vasculature Blood pressure Volume status Uterus Placenta Cord Contraction strength Contraction frequency Baseline uterine tone Uterine relaxation time Exclude uterine rupture Placental separation Vasa previa Vaginal exam Exclude cord prolapsed Begin Corrective Measures if Indicated* Supplemental oxygen IV fluid bolus Maternal position changes Correct hypotension Stop or reduce stimulant uterine relaxant amniofusion Clear Obstacles to Rapid Delivery Determine Decision to Delivery Time Facility OR availability Response time Equipment Staff notifying staff Obstetrician Availability Surgical Training assistant Experience Anesthesiologist Neonatologist Pediatrician Nursing staff Mother Informed consent Surgical considerations IV access (prior abdominal of Anesthesia uterine surgery) options Medical Laboratory tests considerations Blood products (obesity, Urinary catheter hypertension, Fetus Labor Confirm Estimated fetal weight Gestational age Presentation Position Confirm Accurate monitoring Adequate uterine activity diabetes) Estimated fetal weight Gestational age Presentation Position Arrest disorder Protracted labor Remote from delivery Poor expulsive efforts Examples of clinical factors to be considered in a systematic manner. Institutions may modify according to individual circumstances. * Conservative corrective measures should be guided by clinical circumstances. For example, amnioinfusion may be appropriate in the setting of variable decelerations but would not be expected to result in resolution of late decelerations. IV indicates intravenous; OR, operating room. expedited. Tracings that remain in category II warrant additional evaluation. If a category II FHR tracing shows moderate variability and/or accelerations without clinically significant decelerations, continued surveillance is reasonable (Fig. 1).

5 26 Miller TABLE 3. Examples of Causes of Fetal Heart Rate Changes Not Directly Related to Fetal Oxygenation Maternal Fever Infection Medication Hyperthyroidism Fetal Sleep cycle Infection Anemia Arrhythmia Heart block Congenital anomaly Preexisting neurologic injury Extreme prematurity Category II tracings that do not meet these criteria require further measures. If there is any question regarding the presence of moderate variability, accelerations or the clinical significance of any decelerations, the most reasonable approach is to take the next step in the ABCD management model. (C) Clear obstacles to rapid delivery: If conservative corrective measures do not result in moderate variability (and/or accelerations) and resolution of clinically significant decelerations, it is prudent to plan ahead for the possible need for rapid delivery. This does not constitute a commitment to a particular time or method of delivery. Instead, it provides a systematic reminder of factors involved in the decision process. A practical approach includes review of the individual characteristics (from large to small) of the facility, staff, mother, fetus, and labor (Table 2). Standardized intrapartum FHR management does not mandate that each of these measures are carried out. It simply provides a systematic checklist of factors to consider in order to minimizing potential errors and to encourage timely decision making. (D) Decision-to-delivery time: After appropriate conservative measures have been implemented, it is sensible to take a moment to estimate the time needed to accomplish delivery in the event of a sudden deterioration of the FHR tracing. This can be facilitated by systematically considering individual characteristics of the facility, staff, mother, fetus, and labor (Table 2). The anticipated decision-to-delivery time must be taken into consideration when weighing the risks and benefits of continued expectant management versus expeditious delivery. Transition Management steps A, B, C, and D are largely uncontroversial, are readily amenable to standardization, and represent the overwhelming majority of decisions that must be made during labor. However, once they are exhausted, standardized intrapartum FHR management must transition exclusively to individual clinical judgment. Delivery If conservative measures are unsuccessful, the clinician must decide whether to await spontaneous vaginal delivery or to expedite delivery by other means. This decision demands individual clinical judgment, weighing the estimated time until vaginal delivery against the estimated time until the onset of metabolic acidemia and potential injury. Information in the literature is limited regarding the rate of progression of metabolic acidemia. The topic is reviewed in detail elsewhere in this symposium. Retrospective data suggest that, in the setting of minimal-absent variability and recurrent decelerations, metabolic acidemia can evolve over a period of approximately 60 minutes, assuming that the preceding tracing was normal. 11 This process can occur much more rapidly, more slowly, or not at all, depending on many factors, including the frequency and duration of decelerations. Despite the paucity of data, a clinical decision must be made using the best

6 Intrapartum Fetal Heart Rate Management 27 information available. The ultimate decision may differ from case to case. However, a standardized, systematic approach can help ensure that management decisions are made in a timely manner and are based, to the extent possible, on scientific evidence and consensus in the literature. The most important part of this step in FHR management is to use discipline and individual clinical judgment to make and document a plan. Conclusions Recent progress toward consensus in FHR monitoring makes it possible to construct a practical, standardized approach to FHR interpretation and management. The intrapartum FHR management model described in this article is not intended to dictate actions that must be taken in response to specific FHR patterns. Instead, it is intended to serve as a reminder of common sources of preventable error and a reminder of actions that should be considered to ensure that management decisions are made in a timely manner. References 1. Electronic fetal heart rate monitoring: research guidelines for interpretation. National Institute of Child Health and Human Development Research Planning Workshop. Am J Obstet Gynecol. 1997; 177: American College of Obstetricians and Gynecologists. Neonatal Encephalopathy and Cerebral Palsy: Defining the Pathogenesis and Pathophysiology. Washington, DC: American College of Obstetricians and Gynecologists; MacLennan A. A template for defining a causal relation between acute intrapartum events and cerebral palsy: international consensus statement. BMJ. 1999;319: American College of Obstetricians and Gynecologists. ACOG practice bulletin. Clinical management guidelines for obstetricians-gynecologists, number 70, December 2005 (replaces practice bulletin number 62, May 2005). Intrapartum fetal heart rate monitoring. Obstet Gynecol. 2005;106: Association of Women s Health, Obstetric and Neonatal Nurses. Fetal Heart Monitoring: Principles and Practices. 3rd ed. Washington, DC: Association of Women s Health, Obstetric and Neonatal Nurses; Association of Women s Health, Obstetric and Neonatal Nurses. Fetal Heart Monitoring: Principles and Practices. 4th ed. Washington, DC: Association of Women s Health, Obstetric and Neonatal Nurses; American College of Nurse-Midwives. Position Statement: Standardized Nomenclature for Electronic Fetal Monitoring. Silver Spring MD: American College of Nurse-Midwives; Macones GA, Hankins GD, Spong CY, et al. The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines. Obstet Gynecol. 2008;112: American College of Obstetricians and Gynecologists. ACOG Practice Bulletin number 106: intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles. Obstet Gynecol. 2009;114: American Academy of Pediatrics. American College of Obstetricians and Gynecologists: Guidelines for Perinatal Care. 6th ed. Washington, DC: American Academy of Pediatrics; Parer JT, King T, Flanders S, et al. Fetal acidemia and electronic fetal heart rate patterns: is there evidence of an association? J Matern Fetal Neonatal Med. 2006; 19: