What is the management of seizures after heart surgery, particularly regarding antiepileptic medication such as Keppra (levetiracetam) and Dilantin (phenytoin)?

Management of Seizures After Heart Surgery

Treat clinical seizures aggressively with levetiracetam (Keppra) or sodium valproate as first-line agents, while phenytoin should be avoided due to inferior efficacy and higher risk of adverse effects in the post-cardiac surgery setting. 1

Immediate Diagnostic Approach

• Obtain EEG monitoring promptly to distinguish epileptic from non-epileptic seizures, as clinical examination alone is unreliable—many seizures are subclinical and only detectable by EEG. 1
• Perform intermittent EEG for patients with clinical seizure manifestations; consider continuous EEG monitoring if status epilepticus is diagnosed or suspected. 1
• Order head CT imaging in 80-85% of cases to identify treatable pathology—ischemic strokes occur in approximately 53% of post-cardiac surgery seizure patients, with embolic patterns in 34%. 2
• Exclude precipitating causes before initiating maintenance therapy: intracranial hemorrhage, electrolyte imbalances (particularly hyponatremia, hypocalcemia), and hypoglycemia. 1

First-Line Pharmacologic Treatment

Levetiracetam (Keppra) is the preferred initial agent based on superior efficacy and safety profile compared to phenytoin:

• Levetiracetam demonstrates 70.9% efficacy versus phenytoin's 58.1% in controlling seizures without additional medication. 3
• Particularly effective for myoclonic seizures, which occur in 18-25% of post-cardiac arrest patients. 1, 4
• Minimal cardiovascular side effects—critical advantage in cardiac surgery patients with hemodynamic instability. 3
• No significant drug interactions or need for therapeutic monitoring. 3

Sodium valproate is an equally acceptable first-line alternative, especially for myoclonic manifestations. 1, 4

Why Phenytoin (Dilantin) Should Be Avoided

• Phenytoin is frequently ineffective for post-anoxic myoclonus, the most common seizure type after cardiac surgery. 1, 4
• Carries 23.3% risk of adverse reactions versus 1.4% with levetiracetam, predominantly hypotension—particularly dangerous in post-cardiac surgery patients. 3
• Associated with anaphylaxis risk and requires slower infusion rates. 3
• Inferior seizure control rates (57.7% vs 77.6% for levetiracetam in convulsive status epilepticus). 3

Refractory Seizures and Status Epilepticus

If first-line agents fail:

• Propofol is highly effective for suppressing both clinical seizures and electrographic seizure activity, particularly for post-anoxic myoclonus. 1, 4
• Consider clonazepam as an antimyoclonic agent for refractory cases. 1, 4
• Benzodiazepines or barbiturates for status epilepticus following standard protocols. 1
• Be aware that post-cardiac arrest seizures are often refractory to multiple medications—62% develop status epilepticus. 1, 5

Seizure Prophylaxis: Not Recommended

• Do not use prophylactic anticonvulsants after cardiac surgery or cardiac arrest—no evidence of benefit and significant risk of adverse effects. 1
• Routine prophylaxis is explicitly not recommended by international resuscitation guidelines. 1

Risk Stratification and Monitoring Duration

High-risk features requiring heightened vigilance:

• Deep hypothermic circulatory arrest (strongest predictor). 2
• Aortic calcification or atheroma. 2
• Open chamber surgery. 6
• Cardiopulmonary bypass time >150 minutes. 6
• Critical preoperative state. 2
• Tranexamic acid exposure increases seizure risk 7.4-fold—consider dose modification as a modifiable risk factor. 6

Median seizure onset is 20 hours post-surgery (range 2.4-15.1 hours), with 85% being subclinical (EEG-only). 6, 5

Critical Pitfalls to Avoid

• Do not rely on clinical examination alone—85% of post-cardiac surgery seizures have no clinical correlate and require EEG for detection. 5
• Avoid excessive sedation and high-dose anticonvulsants that may mask clinical examination and lead to overly pessimistic prognostication. 4
• Do not assume all myoclonus is epileptic—the majority of post-anoxic myoclonus is non-epileptic and may not require aggressive treatment. 1, 4
• Recognize Lance-Adams syndrome (generalized myoclonus with epileptiform discharges) which paradoxically carries good prognosis and may not warrant aggressive treatment. 4

Prognostic Implications

• Seizure occurrence increases operative mortality nearly fivefold (29% vs 6%). 2
• ICU mortality rises from 1.4% to 9.7% in seizure patients. 6
• Despite poor overall prognosis, 41-48% of patients are discharged without neurologic deficit and can discontinue anticonvulsants before discharge. 6, 2
• Prolonged observation is necessary after seizure treatment before prognostication. 1

Maintenance Therapy

• Initiate maintenance anticonvulsant therapy after the first seizure once reversible causes are excluded. 1
• Continue monitoring as 58% of seizures recur during hospitalization. 6
• Reassess need for long-term anticonvulsants at discharge—nearly half of patients can safely discontinue therapy. 6