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Jaw tone dynamics across varying depths of anesthesia in a swine model
McKenna Andelin1, Eduardo Hatschbach1, Simone Scherer1
1Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN, United States.
Objective:
To determine if jaw tone measured objectively can predict a non-surgical depth of anesthesia (DoA) or reliably distinguish between surgical and non-surgical DoA.
Study Design:
Prospective, randomized, crossover experimental trial.
Animals:
Nine, five-month-old, male intact Hanford minipigs.
Methods:
A custom device was developed (n = 2 pigs) and used to obtain objective measurements of jaw tone at surgical and non-surgical DoA (n = 7 pigs), defined according to positive withdrawal to dewclaw clamping during isoflurane anesthesia. Jaw opening force and compliance were analyzed using two-way ANOVA. Areas under curves (AUCs) for jaw opening force and compliance were calculated and compared between DoAs using a two-tailed Wilcoxon matched-pairs signed rank test (p < 0.05).
Results:
Jaw tone did not change in advance of a positive withdrawal to dewclaw clamping in any of the pigs and therefore was not predictive of non-surgical DoA. There was a minimal and non-significant role of DoA in jaw opening force (2%, p = 0.1827) and compliance (0.2%, p = 0.9910). Median AUCs for jaw-opening force differed significantly between DoA (p = 0.0469), whereas AUCs for compliance did not (p = 0.1562).
Conclusion:
Jaw tone was not predictive of non-surgical DoA, and did not reliably distinguish between DoA, despite a statistically significant difference in AUC force.
Clinical Relevance:
Jaw tone is an insufficient predictor of non-surgical DoA and has limited usefulness in distinguishing between surgical from non-surgical DoA.
