Five percent CO₂ is a potent, fast-acting inhalation anticonvulsant.

Abstract

PURPOSE:

CO₂ has been long recognized for its anticonvulsant properties. We aimed to determine whether inhaling 5% CO₂ can be used to suppress seizures in epilepsy patients. The effect of CO₂ on cortical epileptic activity accompanying behavioral seizures was studied in rats and nonhuman primates, and based on these data, preliminary tests were carried out in humans.

METHODS:

  In freely moving rats, cortical afterdischarges paralleled by myoclonic convulsions were evoked by sensorimotor cortex stimulation. Five percent CO₂ was applied for 5 min, 3 min before stimulation. In macaque monkeys, hypercarbia was induced by hypoventilation while seizure activity was electrically or chemically evoked in the sensorimotor cortex. Seven patients with drug-resistant partial epilepsy were examined with video-EEG (electroencephalography) and received 5% CO₂ in medical carbogen shortly after electrographic seizure onset.

RESULTS:

In rats, 5% CO₂ strongly suppressed cortical afterdischarges, by approximately 75%, whereas responses to single-pulse stimulation were reduced by about 15% only. In macaques, increasing pCO₂) from 37 to 44-45 mm Hg (corresponding to inhalation of 5% CO₂ or less) suppressed stimulation-induced cortical afterdischarges by about 70% and single, bicuculline-induced epileptiform spikes by approximately 25%. In a pilot trial carried out in seven patients, a rapid termination of electrographic seizures was seen despite the fact that the application of 5% CO₂ was started after seizure generalization.

CONCLUSIONS:

Five percent CO₂ has a fast and potent anticonvulsant action. The present data suggest that medical carbogen with 5% CO₂ can be used for acute treatment to suppress seizures in epilepsy patients.

• Authors: Else A Tolner, Daryl W Hochman, Pekka Hassinen, Jakub Otáhal, Eija Gaily, Michael M Haglund, Hana Kubová, Sebastian Schuchmann, Sampsa Vanhatalo, Kai Kaila
• Journal: Epilepsia (Epilepsia) Vol. 52 Issue 1 Pg. 104-14 (Jan 2011) ISSN: 1528-1167 [Electronic] United States
• PMID: 20887367 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Wiley Periodicals, Inc. © 2010 International League Against Epilepsy.

Chemical References

• Anticonvulsants
• Carbon Dioxide

Topics

• Administration, Inhalation
• Adolescent
• Adult
• Animals
• Anticonvulsants (administration & dosage, chemistry)
• Carbon Dioxide (administration & dosage, chemistry)
• Electroencephalography (drug effects, methods)
• Female
• Humans
• Macaca nemestrina
• Male
• Middle Aged
• Pilot Projects
• Rats
• Rats, Wistar
• Seizures (drug therapy, physiopathology)
• Time Factors
• Young Adult