Effect of Sedation on the Neurological Examination of the Patellar and Withdrawal Reflexes in Healthy Dogs

Abstract

Introduction: Pain, temperament, fear, and anxiety can prevent safe and accurate evaluation of common neurologic reflexes in dogs. When sedation is used it is unknown how the neurological examination, and specifically patellar and withdrawal reflexes are affected, and, if present, how long any effect might last. The purpose of this study is to investigate the effect of sedation on the evaluation of select common limb spinal reflexes in healthy dogs.Material and Methods: Fourteen healthy dogs with normal neurologic exams were included. After placing joint landmarks, patellar reflex and pelvic and thoracic limb withdrawal reflexes were tested. Joint angles were measured, obtaining reflex angle endpoints, change in angle, and change in time to reflex completion. These measurements were recorded at different time points: prior to sedation (awake timepoint), 15 and 30 min following administration of standardized sedation protocol of dexmedetomidine and butorphanol, and 15 and 30 min following administration of a standardized reversal agent, atipamazole.Results: For patellar reflex, the stifle end angle increased from 91.5 to 108.55 degrees (p < 0.0001) 15 min following sedation, and remained increased at 104.5 degrees (p < 0.0001) 30 min following sedation. Stifle change in angle increased from 9.6 to 24.4 degrees (p < 0.0001) 15 min following sedation, and remained increased at 20.85 degrees (p < 0.0001) and 11 degrees (p = 0.012) at 30 min sedation and 15 min reversal. Tarsal joint in pelvic withdrawal and elbow in thoracic withdrawal reflexes did not differ in at any timepoint of sedation or reversal when compared with the awake timepoint, for end angle or change in angle. The increases in end angle and change in angle for patellar reflex generated a change in time for patellar reflex from 0.12 s (awake) to 0.129 s (15 min sedation) which was statistically significant (p = 0.041). Change in time did not differ for pelvic withdrawal or thoracic withdrawal.Discussion/Conclusions: Reflexes were elicited in all dogs under sedation. Sedation does not affect the evaluation of the withdrawal reflex on any limb but improves the visualization of the patellar reflex in this group of neurologically normal dogs.

Does preappointment gabapentin affect neurological examination findings? A prospective, randomized and blinded study in healthy cats

“…Other sedative drugs did not alter the assessment of patellar and withdrawal reflex in dogs. 27 We not only looked for negative interferences of gabapentin in the neurological examination; we also sought to identify whether the use of gabapentin brought any benefits, such as increasing the speed of the neurological examination, reducing the number of breaks or increasing cats' compliance with hands-on tests. There was no consistent difference in examination duration or the number of breaks.…”

Effect of medetomidine, midazolam, ketamine, propofol and isoflurane on spinal reflexes in healthy dogs

“…This may be because the drug prevents muscle contraction that may be caused by severe stress in the animal (Murrell & Hellebrekers, 2005 ). As a result, the dogs relax enough and the muscles involved in the reflex relax, while without relaxation, they tighten themselves so much that the stifle joint cannot be opened with a hammer blow (Horsley et al., 2021 ). This condition was clearly observed in the present study during the examination of animals; however, after anaesthesia with isoflurane and dexmedetomidine (the active isomer of medetomidine), it reduces pain‐dependent withdrawal reflexes (Lervik et al., 2012 ).…”

“…In a number of studies, the effects of premedication and anaesthetic drugs on some spinal reflexes in small animals have been studied (Horsley et al., 2021 ; Truchetti et al., 2020 ; Tudury et al., 2017 ). In some of these studies, the effect of some sedatives on the angles of reflexes has been investigated which is very valuable, but in the neurological examination of animals, the angle of the reflexes is not routinely measured, rather, reflexes are examined visually.…”

“…In some of these studies, the effect of some sedatives on the angles of reflexes has been investigated which is very valuable, but in the neurological examination of animals, the angle of the reflexes is not routinely measured, rather, reflexes are examined visually. In these studies, only the effects of dexmedetomidine and butorphanol on the patellar and limb withdrawal reflexes (Horsley et al., 2021 ), and the effect of nerve block on the extensor carpi radialis and cranial tibial reflexes (Tudury et al., 2017 ), have been investigated. On the other hand, there is still no specific protocol according to which a specific drug can be used for chemical restrain of fearful or aggressive dogs.…”