What is the role of prognostic scores, such as Sarnat score or Thompson score, in managing patients with Hypoxic Ischemic Encephalopathy (HIE)?

Prognostic Scores in Hypoxic Ischemic Encephalopathy Management

Prognostic scores such as the Thompson score and Sarnat score are valuable tools for risk stratification, treatment decisions, and communication with families, but should never be used as the sole basis for limiting life-sustaining treatment in patients with Hypoxic Ischemic Encephalopathy (HIE).

Role of Prognostic Scores in HIE Management

Primary Functions

• Risk stratification: Identify patients at high risk for adverse outcomes
• Treatment planning: Guide therapeutic interventions including therapeutic hypothermia
• Communication: Provide framework for discussions with families
• Quality metrics: Benchmark care and outcomes

Key Prognostic Scores

1. Thompson Score

• Evaluates clinical signs of encephalopathy in neonates
• Strong predictive value for:
  • Abnormal amplitude-integrated EEG at 6 hours (sensitivity 100%, specificity 67%) 1
  • Moderate-severe encephalopathy within 72 hours (sensitivity 90%, specificity 92%) 1
  • Long-term cognitive and neurological outcomes in cooled infants 2
• Higher scores correlate with:
  • Longer hospital stays
  • Need for antiseizure medications at discharge
  • More severe metabolic acidosis
  • Greater likelihood of target organ damage 3
• Most valuable when assessed after the third day of life for long-term outcome prediction 2

2. Sarnat Score

• Classifies HIE into three stages based on clinical examination
• Good electro-clinical correlation in stage 3 (severe HIE) 4
• Less predictive in stage 2 (moderate HIE) where neuroimaging provides better prognostic information 4

Multimodal Prognostic Approach

Current guidelines recommend a multimodal approach to prognostication in HIE:

1. Never rely on a single test or score 5

   • "It is not recommended to use any single factor/tool (e.g., brain imaging only) as the sole indicator for patient prognosis"

2. Combine multiple assessment modalities 5:

   • Clinical examination and severity scores
   • Neurophysiological testing (EEG, amplitude-integrated EEG, visual evoked potentials)
   • Neuroimaging (MRI, particularly diffusion-weighted imaging)
   • Laboratory biomarkers (neuron-specific enolase)

3. Consider timing of assessment:

   • Early assessments (first 24-48 hours) have limited prognostic accuracy
   • Serial assessments improve predictive value
   • Most reliable prognostication occurs after 72 hours

Clinical Implementation Algorithm

1. Initial Assessment (0-6 hours):

   • Calculate Thompson or Sarnat score
   • Use score to guide therapeutic hypothermia decisions
   • Thompson score ≥7 strongly predicts abnormal aEEG and need for intervention 1

2. Ongoing Monitoring (24-72 hours):

   • Serial clinical assessments with Thompson/Sarnat scoring
   • EEG monitoring for seizure detection
   • Neuroimaging (MRI when stable)

3. Prognostication (>72 hours):

   • Reassess Thompson/Sarnat score
   • Review multimodal data (clinical, EEG, imaging, biomarkers)
   • Multidisciplinary team discussion

4. Treatment Planning:

   • Antiseizure management based on clinical and EEG findings
   • Rehabilitation needs assessment
   • Follow-up planning

Critical Considerations and Pitfalls

1. Avoid early prognostic certainty:

   • Early limitation of care creates self-fulfilling prophecies of poor outcomes 5
   • Postpone new DNAR orders until at least the second full day 5

2. Beware of confounding factors:

   • Sedative medications
   • Therapeutic hypothermia alters clinical signs
   • Metabolic derangements

3. Recognize limitations of scores:

   • Considerable overlap in Thompson scores between good and poor outcome groups in first 3 days 2
   • Heterogeneity in test performance and cutoff values 6

4. Ensure appropriate communication:

   • Frequent family meetings 5
   • Goals of care discussions reflecting patient/family preferences
   • Avoid overly pessimistic prognostication early in course

Conclusion

Prognostic scores in HIE provide valuable clinical information for risk stratification, treatment decisions, and communication with families. However, they must be used as part of a comprehensive, multimodal assessment approach and never as the sole basis for limiting life-sustaining treatment. The Thompson score appears particularly valuable for predicting both short and long-term outcomes, especially when assessed after the third day of life in infants receiving therapeutic hypothermia.