Conflict of Interest The Problems with the NICHD Categories of FHR - - PowerPoint PPT Presentation

6/8/2018 1

Michael P. Nageotte, MD

The Problems with the NICHD Categories of FHR Nomenclature and Algorithms: Parer Approach versus The World Conflict of Interest

 I have no conflicts of interest regarding this

topic. Learning Objectives

• 1. To summarize the basis of the three Category NICHD FHR

tracing system and review the recommendations for management of these categories.

• 2. To demonstrate the extreme heterogeneity of Category II

patterns in terms of associated fetal hypoxia/acidosis.

• 3. To discuss some of the reasons for this heterogeneity.
• 4. To consider alternative management schemes for Category

II FHR tracings.

The Problems with the NICHD Categories of FHR System Second NIH Consensus Conference 2008

 A three tier system for categorizing FHR patterns

Normal – follow in routine manner with no specific action Abnormal – prompt evaluation/improve pattern or deliver

 Absent variability AND any of the following  Recurrent late decelerations  Recurrent variable decelerations  Bradycardia

Equivocal – require evaluation and continued surveillance

 Bradycardia, tachycardia, minimal or marked variability,

absent variability without decelerations, absence of accelerations after fetal stimulation, recurrent variable decelerations with minimal or moderate variability, prolonged decelerations, recurrent late decelerations with moderate variability, variable decelerations with concerning characteristics with moderate variability

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The intention of EFM should be to avoid serious acidosis rather than to ensure a strong correlation with it.

 The categorization was based on the likelihood of

predicting fetal metabolic acidosis

 The goal of fetal monitoring is to have intervention

before severe fetal acidosis results in cellular damage

 Ideally, in order to determine if a pattern or combination

• f patterns accurately predicts acidosis, one would need

a prospective series of such patterns which were NOT INTERVENED upon.

How were these categories established?

 Primarily they are based on the likelihood that a FHR

pattern within a given category correlates with an increased or decreased risk of fetal metabolic acidosis

 There are two basic concerns with this concept:  Never have abnormal FHR patterns been prospectively

blinded without clinical interventions to assess their true correlation with specific neonatal outcomes

 There is no knowledge of how often or how quickly

different Category II patterns become Category III

 EFM is not a diagnostic test and has very poor specificity

and positive predictive value. It is more like an exercise ECG that identifies abnormal findings which may correlate with bad outcomes allowing for intervention.

The EFM questions we are asking:

 Is the fetus hypoxic?  Is there a metabolic acidosis?  Is there a likelihood that the fetus is having

tissue or organ damage from asphyxia at this point in time?

 If we are unable to correct the suspected

hypoxia and/or acidosis and we do not effect delivery, will the fetus die or become damaged before or subsequent to birth?

Question

Within how many minutes should one be able to establish the category of FHR?

• A. ten
• B. twenty
• C. thirty

t e n t w e n t y t h i r t y

43% 13% 44%

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Threshold for Metabolic Acidosis Associated with Newborn Complications

Low et al:AJOG 1997; 177:1391

 Case-control study (gestational age and birth weight)

• f base deficit in 233 term newborns (58 with BD <8,

58 BD 8-12, 58 BD 12-16, 59 with BD >16 mmol/l)

 Moderate or severe encephalopathy and respiratory

complications only associated with BD >12 mmol/l

 Moderate/severe encephalopathy: 10% with BD 12 –

16; however, 40% with BD >16 (<2% with BD <12)

 Uncommon endpoint as BD 12-16 occurs in only 2%

• f term newborns; BD>16 in only 0.5 % of term

newborns (due to intervention for clinical indications)

Clinical Correlations with Acidosis?

Baseline rate

• Bradycardia not accompanied by absent variability
• Tachycardia

Baseline FHR variability

• Minimal baseline variability
• Absent variability unaccompanied by recurrent decelerations
• Marked baseline variability

Accelerations

• Absence of induced accelerations after fetal stimulation

Periodic or episodic decelerations

• Recurrent variables with minimal/moderate variability
• Prolonged deceleration >2 minutes but <10 minutes
• Recurrent lates with moderate baseline variability
• Variable decelerations with other characteristics such as slow

return to baseline, “overshoots”, nadir >60 bpm below baseline

More than 40 combinations of FHR patterns qualify a tracing as Category II Ignores the issue that there is little likelihood of hypoxia in the absence of decelerations

 Physiologically in labor, hypoxia does not occur in the

absence of decelerations (late, variable or prolonged)

 Loss of variability is not caused by hypoxia alone but by

neurologic depression at the more extreme end – usually with hypoxia and acidosis

 In animal models of hypoxia, (confirmed by pulse oximetry

in humans) decelerations always precede loss of variability

 So, isolated evolving patterns (excepting those that the

patient arrives with where the preceding events are unknown) such as tachycardia and minimal variability without decelerations are unlikely to be associated with acidosis

 Reviewed 48,444 tracings from ten hospitals  Category II patterns were found in 40,758

(84.1%) of tracings, and Category III patterns present in 54 (0.1%) of tracings

Frequency of Fetal Heart Rate Categories and Short-Term Neonatal Outcome

Jackson, M; Holmgren, C.; Esplin, S.; Henry, E; Varner, M. Obstetrics & Gynecology: 2011: 118; 4; 803–808

How can a categorization be useful if 84%

• f patients have equivocal tracings?

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Problems with Category II

 Assumes that the goal of intervention is to wait until there is

correlation with acidosis rather than to avoid serious acidosis. Over 80% of all patients have Category II tracings

 More than 40 combinations of fetal heart rate characteristics qualify

a fetal heart rate pattern as Category II.

 Lumps patterns unlikely to be associated with hypoxia with those

that are very likely to be associated with hypoxia

 Relies heavily on variability  Ignores data from fetal pulse oximetry studies  Ignores the issues of deceleration progression and duration;

combinations of FHR patterns with severity of decelerations

 Ignores the low likelihood of hypoxia without decelerations  Hospitals (nurses, doctors, and policies) are often equating Category

II patterns with not requiring intervention

Management of FHR Tracings Practice Bulletin 116, Nov. 2010

 Acknowledges “diverse spectrum” of category II FHR patterns

Nothing in the algorithm mentions decelerations

The 3 Tiered system relies heavily

• n variability

 To reach Category 3 one must have

absent variability with late, variable or prolonged decelerations/bradycardia

 Even with the proposed management

algorithm one needs to have absent or minimal variability with Category II tracings to warrant intervention Variability Does NOT Reliably Rule In or Rule Out Metabolic Acidosis Minimal or Absent Variability Does Not Rule In Acidosis

 Sleep cycles  Previous neurologic insult  Drugs  Infection  Anomaly  Genetic Disorder  Brain Tumor  Trauma  Toxins

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Metabolic Acidosis and/or Neurologic Damage May Occur Without Absent FHR Variability Abruption case

 Patient presents at term with painful

contractions and about 150 cc of bright red vaginal bleeding which subsides just after admission.

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DELIVERY

 At 1506, NSVD of 2765 gm male  Apgar scores 3/7/7 at one, five and ten  Cord gases: Artery: 6.96/66/22/-14

Vein: 7.06/48/26/-10 Subsequent admission to NICU with neonatal encephalopathy and possible HIE

Question

When did this fetus/newborn suffer acidosis and damaging asphyxia?

• A. before admission to the hospital
• B. during labor
• C. during period of time off monitor

before delivery

• D. unable to determine

b e f

• r

e a d m i s s i

• n

t

• t

h e h

• s

. . . d u r i n g l a b

• r

d u r i n g p e r i

• d
• f

t i m e

• f

f m . . . u n a b l e t

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e t e r m i n e

11% 83% 1% 5%

The 3 Tiered system relies heavily on variability

Two studies evaluated inter-observer interpretation of FHR

 Blackwell et al: 154 tracings, 3 MFM’s reviewed

 Kappa agreement for various FHR parameters poor (0.81 to 0.16)  For the parameter of absent variability, Kappa was the poorest  Moderate 0.69  Minimal 0.51  Absent 0.16

 Chauhan et al: 100 tracings, 5 clinicians reviewed

 Kappa for variability = poor (0.0 – 0.19)  Kappa for tachycardia = good (0.44-0.59)

Hard to base a system on the one variable which is least agreed upon

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Correlation of arterial fetal base deficit and lactate changes with severity of variable heart rate decelerations in the near-term ovine fetus.

Ross MG,et al: Am J Obstet Gynecol. 2013 Apr;208(4):285.e1-6. doi: 10.1016 AJOG 2012.10.883.

 Method

 Graded umbilical cord compression in sheep  Resulting in mild (30 bpm), moderate (60 bpm) and

severe (>70 bpm) variable decelerations

 Result (in worsening base deficit)

 Mild Decelerations - .21/min  Moderate Decelerations - .27/min  Severe Decelerations - .54/min

Williams and Galarneau AJOG 2003

BD > 12 Outcome Outcome poor good 36 452 Variability Decreased 15 Variability Normal 21 Incidence of poor outcome 36/488 7% % of poor outcome with normal variability 21/36 58% % of poor outcome with decreased variability 15/36 42%

Cahill et al

Association and Prediction of Neonatal Acidemia AJOG 2012

pH<7.1 Outcome Outcome poor good 57 5331 Variablity absent or minimal 5 Variability moderate 52

Incidence of poor outcome

57/5388 1%

% of poor outcome with normal variability

52/57 91%

% of poor outcome with decreased variability

5/57 9% Last 30 minutes

Lumps patterns which are very unlikely to be associated with hypoxia and those that are very likely in the same group

 Examples

 Mild variable decelerations with moderate variability  Recurrent late decelerations with minimal variability  Recurrent prolonged decelerations/bradycardia with

minimal or moderate variability

 Absent FHR accelerations and minimal variability

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Recurrent Prolonged Decelerations

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Questions

Do all these represent Category II tracings?

• A. Yes
• B. No

Y e s N

• 12%

88%

Questions

Do all these tracings rule out the presence of fetal metabolic acidosis?

• A. Yes
• B. No

Y e s N

• 100%

0%

The proposed management does not consider severity, combinations of patterns, duration, stage of labor, nor progression of patterns

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ALTERNATIVE METHODS FOR EFM ASSESSMENT (App: Fetal Heart Rate 5-tier)

Parer JT, Ikeda T. A framework for standardized management

• f intrapartum fetal heart rate patterns.

Am J Obstet Gynecol. 2007 Jul;197(1):26.e1-6.

Graded classification of fetal heart rate tracings: association with neonatal metabolic acidosis and neurologic morbidity

• C. Elliott, MEng; P.A. Warrick, MEng; E. Graham, MD; E. F. Hamilton, MD

AJOG 2010;202:258.e1-8

OBJECTIVE: The objective of the study was to measure the performance of a 5-tier, color-coded graded classification of electronic fetal monitoring (EFM). STUDY DESIGN: We used specialized software to analyze and categorize 7416 hours of EFM from term pregnancies. We measured how often and for how long each of the color-coded levels appeared in 3 groups of babies: (A) 60 babies with neonatal encephalopathy (NE) and umbilical artery base deficit (BD) levels greater than 12 mmol/L; (I) 280 babies without NE but with BD greater than 12 mmol/L; and (N) 2132 babies without NE and with normal gases. RESULTS: The frequency and duration of EFM abnormalities considered more severe in the classification method highest in group A and lowest in group N. CONCLUSION: Both degree and duration of tracing abnormality are related to outcome.

Coletta J, Murphy E, Rubeo Z, Gyamfi-Bannerman C AJOG 2012 Mar;206(3):

 Case control 24 cases UA pH <7.0 vs. 24 >7.2  20/24 pH < 7.0 and 19/24 pH >7.2 were classified as

Category II at some point

 79% of pH <7.0 were Orange or Red vs. only 12% of

<7.0 were ever Category III (p<.001)

 The 5-tier system of assessing fetal heart rate tracings

is superior to the 3-tier system in identifying fetal metabolic acidemia

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• Variable decelerations lasting longer than 60 seconds and reaching a nadir less than 60 bpm regardless
• f the baseline.
• Any late decelerations of any depth.
• Any prolonged deceleration, as defined by the NICHD. Due to the broad heterogeneity inherent in this

definition, identification of a prolonged deceleration should prompt discontinuation of the algorithm until the deceleration is resolved.

Details of this Algorithm

 Adds in to the equation

 Presence of significant decelerations  Stage of labor  Progress of labor  Presence of accelerations

 Combines minimal with absent variability to

avoid issues with variation in interpretation

 Acknowledges with a number of caveats that

certain clinical situations should be managed with a lower threshold for intervention

 Abruption or prolonged decelerations  TOLAC

Key Takeaways

 The NICHD System of nomenclature is an important advance

in consistently describing FHR patterns

 The 3 tiered category system acknowledges the poor

specificity of the vast majority of FHR patterns in labor

 Using any uniform management scheme for Category II

patterns is not consistent with the understanding of the likelihood of hypoxia across this diverse group

 The management scheme recommended by ACOG for

Category II does not take into account the severity or significance of various types of decelerations, their persistence and duration, the stage of labor or other clinical parameters

 An alternative management scheme incorporating these

limitations would be a better approach to management

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Recommendations

 The NICHD Classification system is a great boon to

consistency in recognizing and describing FHR patterns

 Category I and III are important but limited approaches

.

 Consider using the Parer five tier system for management  Consider using the algorithm proposed for management of

Category II patterns

THANK YOU