The effect of chloral hydrate on genioglossus and diaphragmatic activity.

A child presented with obstructive sleep apnea (OSA) and a near-fatal airway obstruction and respiratory arrest shortly after receiving chloral hydrate (CH). We, therefore, hypothesize that CH might selectively depress upper airway maintaining muscles such as the genioglossus and so predispose to airway obstruction. Genioglossus (GG) and diaphragmatic (DIA) integrated electromyograms (I EMGs) were recorded in four cats and four rabbits before and after hypnotic doses of CH ranging from 200-1000 mg/kg. Results were similar in both species. Peak GG I EMG decreased within 10-20 min after CH in seven of eight animals. Average peak GG I EMGs were decreased from 100% before CH to as low as 37.0 +/- 27.2% (SD) after CH (P less than 0.001). Minimum GG I EMGs fell from 47.2 +/- 27.2% of peak values before CH to as low as 16.0 +/- 9.7% after CH (P less than 0.01). Phasic GG I EMGs decreased from 53.8 +/- 25.1% of peak control activity to as low as 20.6 +/- 24.6% after CH (P less than 0.05). By contrast, peak and phasic DIA I EMGs after CH were not significantly different from those before CH administration. We conclude that hypnotic doses of CH may preferentially depress GG activity as compared with DIA activity. Selective depression of airway-maintaining muscular contraction by CH may place susceptible patients at risk for life-threatening airway obstruction and may preclude the use of CH to facilitate sleep for polygraphic evaluations in patients suspected of having OSA.