Maxillary nerve block within the pterygopalatine fossa of the horse with different volumes: practicability, efficacy and side-effects

Abstract

Summary:The maxillary nerve block within the pterygopalatine fossa is a commonly used technique in equine dental surgery. The objective of the present study was to determine the risks of the maxillary nerve block within the pterygopalatine fossa using two different doses of lidocaine and to evaluate methods for testing adequate analgesia of teeth and gingiva. In a preliminary experiment ten horses were trained to tolerate a mouth gag without sedation. A mechanical and thermal stimulation was applied on the palatal gingiva and the occlusal surface. Thermal as well as mechanical stimulation resulted in a reproducible defense reaction in all horses. The main study was designed as a prospective, randomised, blinded, experimental trial. Ten clinically healthy horses were used in a randomised cross-over design. Horses were sedated with 0.02 -0.03 mg/kg detomidine iv. A maxillary nerve block was performed on one side of the head with the previously described "Extraperiorbital-Fat-Body-Insertion" (EFBI) technique using either 2 ml/100 kg BW lidocaine (group low) or 4 ml/100 kg BW lidocaine (group high). A Schirmer tear test was performed before and after nerve block, on both sides of the head (blocked and non-blocked side). Analgesia of the teeth and the surrounding gingiva was assessed by applying mechanical and thermal stimuli on both sides of the head (blocked and non-blocked side) 10 and 25 minutes after lidocaine injection. Heart rate, respiratory rate, sweating, and change of the pupil size were recorded before and in 5 minute intervals after lidocaine injection for 35 minutes. No side effects were observed in 16 out of 20 experiments. Four horses showed blepharospasm, miosis, swollen palpebrae, superficial corneal ulcer, or uveitis. Symptoms disappeared completely after symptomatic treatment. Lacrimation was reduced after nerve block, even though no statistically significant differences were found for lacrimation rate before and after nerve block. Analgesia of teeth and gingiva was not assessable with thermal and mechanical stimuli in the sedated horse. The used dosage of lidocaine did not influence any of the recorded clinical parameters. Although the pterygopalatine fossa houses delicate anatomical structures, the EFBI-technique appears to be a safe method for blocking the maxillary nerve. It is recommended to apply lubricating ointments to keep the cornea moist and therefore avoid negative side effects on the eye.Keywords: local anaesthesia / analgesia / equine dentistry / maxillary nerve block / lacrimation Citation: Rieder C. M., Staszyk C., Hopster K., Feige K., Bienert-Zeit A. (2016) Maxillary nerve block within the pterygopalatine fossa of the horse with different volumes: practicability, efficacy and side-effects. Pferdeheilkunde 32,[132][133][134][135][136][137][138][139][140]

Maxillary nerve block within the pterygopalatine fossa for oral extraction of maxillary cheek teeth in 80 horses

“…Desensitizing the maxillary branch of the trigeminal nerve is useful for surgical procedures involving the upper (cheek) teeth, paranasal sinuses, maxilla and oral cavity (Newton et al 2000) and is achieved by local blocking the maxillary nerve within the pterygopalatine fossa (Bienert et al 2011). Rieder et al (2016) verified that the maxillary nerve block performed with the EFBI-technique is a feasible clinical technique and the present study demonstrated the practicability of the EFBI-technique under clinical conditions. Only four horses required additional nose-twitch to sedation for better performance of the local nerve block.…”

“…Rieder et al (2016) confirmed in an experimental trail that the EFBI-technique is feasible. The results of this study indicated that a dose of 2 ml/100 kg BW lidocaine might be sufficient.…”

“…Regarding this, the behaviour typical for defense reactions in horses and often seen during the examination of the head (headbanging, headshaking, chewing, stepping forward, or stepping back) was used in the present study to interpret pain sensation. Rieder et al (2016) evaluated two methods (mechanical and thermal stimuli) for testing pain sensation of teeth and gingiva in horses. Using this experimental setup in the present study, pain sensation was tested before tooth extraction in some horses of both groups.…”

Fused incisors in case of a compound odontoma in a horse: Diagnosis and treatment

“…Concerning the region of the tooth structure to be removed, an infraorbital nerve block, which is associated with lower risks, was also considered. The choice to perform a maxillary nerve block was made with consideration of the acceptance by the horse and the difficulty of correct placement, and thus effectiveness of the nerve block (Tremaine 2007, Rieder et al 2016.…”

“…Tetanus toxoid (Equip T, Zoetis Deutschland GmbH, Berlin, Germany; > 30 IU im) was administered prophylactically because the horse had received its last tetanus vaccination two years earlier. After positioning the horse in stocks and sedation, a maxillary nerve block within the pterygopalatine fossa was performed according to the instructions of Rieder et al (2016). Additionally, local anaesthesia of the gingiva and the periodontal space surrounding tooth 602 was performed using lidocaine (Lidocainhydrochlorid 2 %, Bela-pharm GmbH & Co. KG, Vechta, Germany).…”