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

Role of Prognostic Scores in Managing Hypoxic Ischemic Encephalopathy (HIE)

Prognostic assessment after hypoxic ischemic encephalopathy should be performed using a standardized multidimensional approach rather than relying on any single prognostic score alone. 1

Key Prognostic Scores for HIE

Thompson Score

• Useful clinical tool that correlates with early outcomes in HIE patients
• Predicts:
  • Length of hospital stay
  • Need for antiseizure medications at discharge
  • Long-term cognitive and neurological outcomes 2, 3
• Higher scores (particularly after day 3 of life) are significantly associated with adverse outcomes 3
• Sensitivity of 100% and specificity of 67% for predicting abnormal amplitude-integrated EEG at 6 hours 4
• Particularly valuable for early triage decisions regarding therapeutic hypothermia

Sarnat Score

• Classic staging system for HIE severity (Stage 1-3)
• Good electro-clinical correlation in Stage 3 (severe) HIE 5
• Modified Sarnat encephalopathy grade at 3-5 hours has 97% sensitivity and 71% specificity for predicting abnormal aEEG at 6 hours 4

Comprehensive Prognostic Assessment

Current guidelines recommend a multidimensional approach to prognostication that includes:

1. Clinical examination and scoring:

   • Thompson or Sarnat scoring systems
   • Neurological examination findings

2. Electrophysiological studies:

   • Electroencephalogram (EEG) - sensitivity 92%, specificity 83% 6
   • Amplitude-integrated EEG (aEEG) - sensitivity 93%, specificity 90% 6
   • Visual evoked potentials - sensitivity 90%, specificity 92% 6

3. Neuroimaging:

   • Diffusion-weighted MRI - best specificity (89%) 6
   • T1/T2-weighted MRI - best sensitivity (98%) 6
   • CT scan when MRI unavailable

4. Laboratory markers:

   • Neuron-specific enolase 1

Clinical Application Algorithm

1. Initial assessment (0-6 hours):

   • Apply Thompson score or modified Sarnat grade
   • If Thompson score ≥7 or moderate-severe Sarnat grade, consider therapeutic hypothermia
   • Perform aEEG if available

2. Ongoing assessment (24-72 hours):

   • Continue serial Thompson/Sarnat scoring
   • Obtain EEG to evaluate for seizure activity
   • Consider MRI after rewarming if therapeutic hypothermia was initiated

3. Prognostication (72+ hours):

   • Integrate all available data (clinical scores, EEG, imaging)
   • Avoid making definitive prognostic statements based on any single test
   • Delay definitive prognostication until at least the second full day of hospitalization

Important Caveats

• Avoid early limitation of care: Aggressive care early after HIE onset and postponement of DNAR orders until at least the second full day is recommended 1
• Self-fulfilling prophecy risk: Early care limitations can create a self-fulfilling prophecy of poor outcome 1
• Therapeutic hypothermia impact: Traditional prognostic scores were developed before routine therapeutic hypothermia, which may alter their predictive value 3
• Shared decision-making: Use prognostic information as part of shared decision-making with family, not as the sole determinant for care decisions 1

Pitfalls to Avoid

1. Using a single test for prognostication: No single factor/tool should be used as the sole indicator for patient prognosis 1

2. Premature prognostication: Early prognostication may be overly pessimistic and lead to inappropriate limitation of care 1

3. Failure to reassess: Serial assessments provide more accurate prognostic information than single evaluations

4. Overlooking treatable conditions: Always evaluate for treatable conditions like non-convulsive status epilepticus before making prognostic determinations 1

5. Ignoring family preferences: Frequent meetings with family that reflect patient/family preferences are essential 1

In summary, while prognostic scores like Thompson and Sarnat provide valuable information for clinical decision-making in HIE, they should be integrated with other clinical, electrophysiological, and imaging data to guide management decisions and family discussions about prognosis.