Lactic Acid Measurement During Seizures
Routine measurement of lactic acid or lactic dehydrogenase levels during seizures is not necessary, as post-ictal lactic acidosis is typically self-limiting and resolves spontaneously without specific intervention. 1, 2
Understanding Post-Ictal Lactic Acidosis
- Seizures commonly cause transient lactic acidosis due to increased muscle activity and local hypoxia during convulsions 2
- Immediately after a seizure, venous lactate concentrations can be significantly elevated (mean 12.7 ± 1.0 meq/L), with corresponding decreases in arterial pH (mean 7.14 ± 0.06) 3
- This metabolic disturbance is typically self-limiting, with lactate levels and pH normalizing within 1-2 hours post-seizure without specific treatment 1, 3
Clinical Implications
- Obtaining arterial blood samples for lactate measurement in the emergency setting has limited value for most seizure patients 1
- Severe lactic acidosis following seizures does not typically require specific treatment as it resolves spontaneously 2
- The spontaneous resolution occurs primarily through metabolism of lactate and concomitant removal of hydrogen ions 3
When to Consider Lactate Measurement
- Persistent hyperlactatemia (beyond 1-2 hours post-seizure) may indicate serious underlying pathology requiring further investigation 1
- If lactate levels are measured immediately post-seizure and found to be elevated, a repeat measurement should be obtained 1-2 hours later to confirm normalization 1
Physiological Mechanism
- During seizures, glycolysis increases to meet heightened energy demands 4
- Lactic acid initially provides energy in the early stages of seizures 4
- As seizures progress, accumulated lactic acid reduces tissue pH, inducing metabolic acidosis that may contribute to seizure termination 4
- Elevated cerebrospinal fluid lactate may persist longer than arterial lactate elevations (3-6 hours vs. 1-2 hours) 5
Recommended Laboratory Tests for New-Onset Seizures
According to clinical guidelines, the following tests are recommended for patients with new-onset seizures who have returned to baseline:
- Serum glucose and sodium levels 6
- Pregnancy test for women of childbearing age 6
- Lumbar puncture (after head CT) for immunocompromised patients 6
Common Pitfalls
- Misinterpreting post-ictal lactic acidosis as indicating a more serious condition requiring aggressive intervention 2
- Failing to repeat lactate measurements when initial levels are concerning 1
- Unnecessary treatment of self-limiting post-ictal lactic acidosis 2
In conclusion, while seizures commonly cause transient lactic acidosis, routine measurement of lactate levels during or immediately after seizures adds little clinical value and is not necessary for most patients.