We planned a cross-sectional analysis to determine the frequency and severity of metabolic acidosis in patients taking topiramate while awaiting craniotomy.

Eighty patients (18 – 65 years) taking topiramate to control seizures while awaiting elective craniotomy were enrolled. Any signs of metabolic acidosis or topiramate-related side effects were investigated. Blood chemistry levels and arterial blood gases, including lactate, were obtained. The severity of metabolic acidosis was defined according to base excess levels as mild or moderate.

Blood gas analysis showed that 71% (n = 57) of patients had metabolic acidosis. The frequency of moderate metabolic acidosis was 56% (n = 45), while that of mild metabolic acidosis was 15% (n = 12). A high respiratory rate was reported in only 10% of moderately acidotic patients.

In patients receiving topiramate, baseline blood gas analysis should be performed preoperatively to determine the presence and severity of metabolic acidosis.