[Losing consciousness: role of the venous lactate levels in the diagnosis of convulsive crises].

OBJECTIVES

This prospective study was conducted to evaluate the usefulness of venous lactate assay in the diagnosis of generalized seizures.

PATIENTS AND METHODS

Over a three month period, 78 consecutive adults admitted to the emergency unit for unconsciousness were included in the study. Three study groups were defined: patients with generalized seizures (n = 22), unconscious patients without seizure (n = 34) and known epileptic patients with unexplained malaises (n = 22). Patients with a disease susceptible of increasing lactate levels were excluded. Peripheral venous blood was drawn to determine lactates, bicarbonates and pH on a blood gas analyzer. All determinations were performed within 5 minutes of blood withdrawal. CPK level was also determined with an enzymatic method.

RESULTS

In patients who had seizures, venous lactate levels were higher than those in patients who had no seizures: 4.3 +/- 0.5 mmol/l in generalized seizure patients versus 1.64 +/- 0.1 and 2.2 +/- 1.39 in unconscious patients without seizure and known epileptic patients with unexplained malaise respectively. The threshold lactate level of 2.5 mmol/l given by ROC curves gave a 0.97 specificity and a 0.73 sensitivity.

DISCUSSION

The acidosis observed in patients with generalized seizures results from the combined effects of respiratory and metabolic acidosis. High lactate level would be a consequence of hypoxemia, per seizure rise in catecholamines, and aerobic and anaerobic metabolism in muscles during the tonic-clonic phase. In patients presenting in an unconscious state, increased lactate levels, even when determined up to 2 hours after venous blood withdrawal, could be a useful parameter for the diagnosis of epileptic seizure.