The effects of maxillary nerve block, ethmoidal nerve block and their combination on cardiopulmonary responses to nasal stimulation in anesthetized Beagle dogs

Abstract

Objective To describe an approach for ethmoidal nerve block (E-BLOCK) and to compare the effects of a maxillary nerve block (M-E-BLOCK), E-BLOCK and their combination (M-E-BLOCK) on heart rate (HR), systolic (SAP), mean (MAP), diastolic (DAP) arterial pressures and respiratory rate (f(R)) during nasal stimulation in dogs. Study design Prospective, blinded, randomized, crossover placebo-controlled study. Animals Beagle dogs (five cadavers, nine live dogs), with a median (interquartile range) weight of 10.5 (10.3-11.0) kg. Methods The accuracy of iohexol injections (each 1 mL) at the maxillary and ethmoidal foramina in cadavers was evaluated using computed tomography. Then, anesthetized dogs were administered four bilateral treatments separated by 1 week, saline or 2% lidocaine 1 mL per injection: injections of saline at the maxillary and ethmoidal foramina (Control), injections of lidocaine at the maxillary foramina and saline at the ethmoidal foramina (M-BLOCK), injections of saline at the maxillary foramina and lidocaine at the ethmoidal foramina (E-BLOCK) and injections of lidocaine at all foramina (M-E-BLOCK). The ventral nasal meatus was bilaterally stimulated using cotton swabs, and HR, SAP, MAP, DAP and f(R) were continuously recorded. Values for each variable were compared before and after stimulation using Wilcoxon signed-rank test. Changes in variables among treatments were analyzed using Mann-Whitney U and Kruskal-Wallis tests (p <= 0.05). Results Computed tomography revealed iohexol distribution around the openings of the target foramina in all cadavers. In living dogs, HR, SAP, MAP, DAP and f(R) significantly increased after stimulation within each treatment (p < 0.03). Physiologic responses were significantly attenuated, but not absent, in the M-E-BLOCK [HR (p = 0.019), SAP, MAP, DAP and f(R) (all p <= 0.001)] compared with those in the Control. Conclusions and clinical relevance Concurrent injections of lidocaine at the maxillary and ethmoidal foramina attenuated HR, arterial pressure and f(R) responses to nasal stimulation in Beagle dogs.