Effects of various anesthetic agents on laryngeal motion during laryngoscopy in normal dogs.
OBJECTIVE
To evaluate the effects of various drugs and drug combinations conventionally used for anesthesia on arytenoid cartilage motion during laryngoscopy in normal dogs.


METHODS
Experimental study.


METHODS
Six large breed healthy dogs with no previous history of respiratory dysfunction.


METHODS
Each dog was randomly assigned to a different injectable anesthetic protocol once weekly for 6 weeks, then in the 7th week all dogs were anesthetized with isoflurane. Videolaryngoscopy was performed and recorded starting immediately after induction until dogs could no longer be safely restrained for endoscopy. Video was digitized and 3 still images of maximal inspiration and expiration from the first 15 seconds (induction) and the last 15 seconds (recovery) were captured and imported into an image analysis software program. The height and area of the laryngeal ostium were measured in pixels. Normalization of the glottal gap area was performed using the formula (normalized glottal gap area (NGGA)=area in pixels/height(2)). ANOVA was performed on the NGGA of images collected at inspiration and expiration during induction and recovery. Fischer's exact test was performed when significance (P<.05) was found.


RESULTS
Within each protocol, laryngeal motion (defined as change in NGGA) at induction was not significantly different from laryngeal motion measured at recovery. Additionally, no significant differences were found in arytenoid motion immediately after induction when anesthetic protocols were compared. Arytenoid motion before recovery was significantly greater with thiopental when compared with propofol (P=.046), ketamine+diazepam (P=.0098), acepromazine+thiopental (P=.0021), and acepromazine+propofol (P=.0065). No significant difference in arytenoid motion was seen immediately after induction or before recovery when acepromazine+butorphanol+ isoflurane and thiopental were compared.


CONCLUSIONS
We concluded that intravenous thiopental given to effect is the best choice for assessing laryngeal function in dogs. Dogs premedicated with acepromazine with or without opioids that require further anesthetic restraint for laryngoscopy should be anesthetized with isoflurane administered by mask.


CONCLUSIONS
Misdiagnosis of laryngeal paralysis during laryngoscopy can be avoided by selecting the anesthetic regimens with the least effect on arytenoid motion.
Jackson
Aaron M
AM
College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA.
Tobias
Karen
K
Long
Cassie
C
Bartges
Joseph
J
Harvey
Ralph
R
D000075:Acepromazine / Q000008:administration & dosage / Q000494:pharmacology; D000768:Anesthesia, General / Q000662:veterinary*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001193:Arytenoid Cartilage / Q000187:drug effects* / Q000502:physiology; D003975:Diazepam / Q000008:administration & dosage / Q000494:pharmacology; D004285:Dogs / Q000502:physiology*; D004338:Drug Combinations; D007262:Infusions, Intravenous / Q000662:veterinary; D007649:Ketamine / Q000008:administration & dosage / Q000494:pharmacology; D007828:Laryngoscopy / Q000662:veterinary*; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology; D013874:Thiopental / Q000008:administration & dosage / Q000494:pharmacology
D018686:Anesthetics, Intravenous; D004338:Drug Combinations; D000075:Acepromazine; D007649:Ketamine; D013874:Thiopental; D003975:Diazepam; D015742:Propofol