Maxillary nerve blocks in horses: an experimental comparison of surface landmark and ultrasound-guided techniques

Stephanie Stauffer,Beckie Cordner,Jonathon Dixon,Thomas Witte

doi:10.1016/j.vaa.2016.09.005

Stephanie Stauffer, Beckie Cordner + Show 2 more

Open Access

https://doi.org/10.1016/j.vaa.2016.09.005

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Abstract

ObjectiveThe aim of this preliminary proof-of-concept study was to evaluate and compare the success and complication rate of infiltration of the maxillary nerve of cadaver heads using previously described surface landmarks, standard ultrasound and a novel needle guidance positioning ultrasound system (SonixGPS). Study designProspective, anatomical, method-comparison study. AnimalsThirty-eight equine cadaver heads. MethodsTwenty-six veterinary students performed the three methods consecutively on cadaver heads using an 18 gauge, 8.9 cm spinal needle and 0.5 mL iodinated contrast medium. Computed tomography was used to quantify success (deposition of contrast in contact with the maxillary nerve) and complication rate (contrast identified within surrounding vasculature or periorbital structures) associated with each method. ResultsPerineural injection of the maxillary nerve was attempted 76 times, with an overall success rate of 65.8% (50/76) and complication rate of 53.9% (41/76). Success rates were 50% (13/26) with surface landmark, 65.4% (17/26) with standard ultrasound guidance and 83.3% (20/24) with SonixGPS guidance approaches (Fisher's exact test, p=0.046). No significant difference in complication rate was found between the three methods. ConclusionsUltrasound-guided maxillary nerve blocks were significantly more successful than surface landmark approaches when performed by inexperienced operators, and the highest success rate was achieved with guidance positioning system (GPS) needle guidance. Clinical relevanceLocal anaesthesia of the equine maxillary nerve in the fossa pterygopalatina is frequently used for diagnostic and surgical procedures in the standing sedated horse. Due to vague superficial landmarks with various approaches and the need for experience via ultrasound guidance, this block remains challenging. GPS guidance may improve reliability of maxillary and other nerve blocks, and allow a smaller volume of local anaesthetic solution to be used, thereby improving specificity and reducing the potential for side effects.

Highlights

Many surgical procedures of the equine head can be performed in the standing position with the use of sedation and regional anaesthesia (Young & Taylor 1993; Johnston et al 1995; Mee et al 1998)
Ultrasound guided maxillary nerve blocks were significantly more successful than surface landmark approaches when performed by inexperienced operators, and the highest success rate was achieved with guidance positioning system (GPS) needle guidance
Twenty-six injections were performed using surface landmark guidance, with ultrasound-guidance and, due to technical difficulties relating to software licensing, with needle GPS

Summary

Introduction

Many surgical procedures of the equine head can be performed in the standing position with the use of sedation and regional anaesthesia (Young & Taylor 1993; Johnston et al 1995; Mee et al 1998). More severe complications including collapse, blindness, retrobulbar infection and meningitis have been reported in horses (Staszyk et al.2008; Simhofer 2013), and convulsions, neurological deficits and cardiac arrest have been reported in other species (Rubin 1995; Pearce et al 2003; Staszyk et al 2008;). Some of these reports described complications even when the procedure was performed by experienced clinicians (Bardell et al 2010)

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