Effects of doxapram HCl on laryngeal function of normal dogs and dogs with naturally occurring laryngeal paralysis.
OBJECTIVE
To compare the effects of IV doxapram on glottic size and arytenoid motion in normal dogs and in dogs with laryngeal paralysis.


METHODS
Prospective experimental and clinical trials.


METHODS
Six healthy dogs weighing 24.5 +/- 3.9 kg and six dogs weighing 27.4 +/- 11.5 kg suspected of having laryngeal paralysis.


METHODS
Dogs were pre-medicated with acepromazine and butorphanol, and a light plane of anesthesia was induced with isoflurane by mask. Videoendoscopic examination of laryngeal function was recorded before (baseline) and after IV doxapram administration. Normalized glottal gap area (NGGA) at maximal inspiration and expiration, and percentage change in height, width, area, and NGGA were calculated with measurements from digitized images of the glottal gap.


RESULTS
Active arytenoid motion was present in all normal dogs at baseline. After doxapram administration, depth of respiration appeared greater, but arytenoid motion, as measured by percentage change in NGGA, and in area and width, did not significantly increase in normal dogs. No arytenoid motion was detected in dogs with laryngeal paralysis at baseline; however, rima glottidis NGGA of dogs with laryngeal paralysis was greater at inspiration and expiration than normal dogs. After doxapram administration, dogs with laryngeal paralysis developed paradoxical arytenoid motion and significant, negative percentage change in area (-61%) and NGGA (-145%) because of inward collapse of the arytenoids during inspiration.


CONCLUSIONS
Administration of doxapram during laryngeal examination is useful for differentiating normal dogs from dogs with laryngeal paralysis. Dogs with laryngeal paralysis may suffer extreme glottic constriction with vigorous respirations, and may require intubation during examination.
Tobias
Karen M
KM
Department of Small Animal Clinical Sciences, University of Tennessee, Knoxville, TN 37996-4544, USA. ktobias@utk.edu
Jackson
Aaron M
AM
Harvey
Ralph C
RC
D000818:Animals; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D004283:Dog Diseases / Q000175:diagnosis* / Q000503:physiopathology; D004285:Dogs / Q000502:physiology*; D004315:Doxapram / Q000494:pharmacology*; D005260:Female; D007262:Infusions, Intravenous / Q000662:veterinary; D007828:Laryngoscopy / Q000662:veterinary; D007830:Larynx / Q000187:drug effects* / Q000502:physiology; D008297:Male; D014826:Vocal Cord Paralysis / Q000175:diagnosis / Q000662:veterinary*
D000697:Central Nervous System Stimulants; D004315:Doxapram