Pentobarbital dose-dependently increases respiratory genioglossus muscle activity while impairing diaphragmatic function in anesthetized rats.
BACKGROUND
Anesthetics depress both ventilatory and upper airway dilator muscle activity and thus put the upper airway at risk for collapse. However, these effects are agent-dependent and may involve upper airway and diaphragm muscles to varying degrees. The authors assessed the effects of pentobarbital on upper airway dilator and respiratory pump muscle function in rats and compared these results with the effects of normal sleep.


METHODS
Tracheostomized rats were given increasing doses of pentobarbital to produce deep sedation then light and deep anesthesia, and negative pressure airway stimuli were applied (n = 11). To compare the effects of pentobarbital with those of natural sleep, the authors chronically instrumented rats (n = 10) with genioglossus and neck electromyogram and electroencephalogram electrodes and compared genioglossus activity during wakefulness, sleep (rapid eye movement and non-rapid eye movement), and pentobarbital anesthesia.


RESULTS
Pentobarbital caused a dose-dependent decrease in ventilation and in phasic diaphragmatic electromyogram by 11 +/- 0.1%, but it increased phasic genioglossus electromyogram by 23 +/- 0.2%. Natural non-rapid eye movement sleep and pentobarbital anesthesia (10 mg/kg intraperitoneally) decreased respiratory genioglossus electromyogram by 61 +/- 29% and 45 +/- 35%, respectively, and natural rapid eye movement sleep caused the greatest decrease in phasic genioglossus electromyogram (95 +/- 0.3%).


CONCLUSIONS
Pentobarbital in rats impairs respiratory genioglossus activity compared to the awake state, but the decrease is no greater than seen during natural sleep. During anesthesia, in the absence of pharyngeal airflow, phasic genioglossus activity is increased in a dose-dependent fashion.
Department of Anesthesia and Critical Care, Massachusetts General Hospital, and Harvard Medical School, Boston, MA 02114-2696, USA. meikermann@partners.org
Matthias
M
Eikermann
Philipp
P
Fassbender
Sebastian
S
Zaremba
Amy S
AS
Jordan
Carl
C
Rosow
Atul
A
Malhotra
Nancy L
NL
Chamberlin
D000758:Anesthesia; D000818:Animals; D016292:Procedural Sedation; D003964:Diaphragm / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004576:Electromyography; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D008297:Male; D010424:Pentobarbital / Q000494:pharmacology*; D017286:Polysomnography; D051381:Rats; D017207:Rats, Sprague-Dawley; D015656:Respiratory Mechanics; D012132:Respiratory Muscles / Q000187:drug effects*; D012895:Sleep, REM / Q000502:physiology; D014139:Tracheostomy; D014851:Wakefulness / Q000502:physiology
D006993:Hypnotics and Sedatives; D010424:Pentobarbital