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Will a Critical Level of Hyperventilation‐Induced Hypocapnia Always Induce an Absence Seizure?
Author(s) -
Wirrell Elaine C.,
Camfield Peter R.,
Gordon Kevin E.,
Camfield Carol S.,
Dooley Joseph M.,
Hanna Brian D.
Publication year - 1996
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1157.1996.tb00592.x
Subject(s) - hypocapnia , hyperventilation , anesthesia , epilepsy , medicine , acidosis , hypercapnia , psychiatry
Summary: We wished to determine if the degree of hypocapnia correlates with increased frequency of absence seizures and if there is a critical pCO 2 at which absence seizures are reliably provoked. Twelve untreated children with newly diagnosed absence epilepsy were continuously monitored by EEG and end‐expiratory CO 2 recording during quiet respiration and hyperventilation (to absence seizure or exhaustion) while breathing four gas mixtures: (a) room air, (b) 100% O 2 , (c) 4% CO 2 in room air, or (d) 4% CO 2 + 96% O 2 . In quiet respiration, a reduction in number of spike and wave bursts and total seconds of spike and wave was noted in children breathing supplemental CO 2 (gases c and d vs. gases a and b), p < 0.05. Supplemental O 2 had no effect. Eight subjects had absence seizures elicited with each trial of hyperventilation. All subjects had their own critical pCO 2 , ranging from 19 to 28 mmHg. Three children had no seizures, two despite hypocapnia to pCO 2 of 19 and 21 and 1 who achieved a pCO 2 of only 25. In 1, absence seizures were provoked in only six of nine hyperventilation trials to pCO 2 of 17–23. In 67% of subjects, absence seizures were reliably provoked by hypocapnia. Critical pCO 2 varied among children with absence. Determination of whether variation in sensitivity to hypocapnia may be helpful in determining response to antiepileptic drugs (AEDs) or remission of seizures will require further study.