Evaluation of Two Injection Techniques in Combination with the Local Anesthetics Lidocaine and Mepivacaine for Piglets Undergoing Surgical Castration

Abstract

The present study evaluated the effects of two injection techniques in combination with lidocaine or mepivacaine for piglets undergoing castration. To improve ease of use, a cannula with side holes (one-step fenestrated (F)) was invented to simultaneously deliver a local anesthetic into the testis and scrotum and was compared to a two-step injection technique. The distribution of a lidocaine/contrast agent mixture using the two methods was examined using computed tomography. Piglets were randomly divided into treatment groups: handling, castration without pain relief and castration after lidocaine or mepivacaine injection using the one-step F or two-step method. Acute physiological responses to noxious stimuli were evaluated by measuring the mean arterial blood pressure (MAP), heart rate (HR) and nocifensive movements. Fos protein expression in the spinal dorsal cord was semi-quantitatively analyzed. Both injection techniques achieved similar distribution patterns. The one-step F method was faster and easier. Injection was not associated with significant changes in MAP or HR, but Mepi1 and NaCl elicited significantly increased nocifensive movements. Both techniques significantly reduced MAP and nocifensive movements when the spermatic cords were cut, regardless of the local anesthetic type. Compared to NaCl, only the lidocaine treatments significantly reduced HR during skin incision. Lido2 significantly reduced Fos protein expression.

Efficacy of inguinal buffered lidocaine and intranasal flunixin meglumine on mitigating physiological and behavioral responses to pain in castrated piglets

“…The results from this study agree with numerous studies that have consistently demonstrated lidocaine does not decrease cortisol concentrations in castrated piglets ( 34 – 36 ) and in fact may increase cortisol concentrations when compared to castrated piglets receiving no anesthetic ( 37 , 38 ). However, past work conducted ( 39 , 40 ), and more recent studies in 2022 ( 41 ) have demonstrated lidocaine efficacy in mitigating castration stress. There seems to be no consensus in the literature about the effectiveness of lidocaine in reducing the physiological responses in piglets undergoing castration, however, this can be explained by differences in the interval between treatment administration and castration (0, 3, 5, 10, or 20 min).…”

Behavior of Piglets in an Observation Arena before and after Surgical Castration with Local Anesthesia

“…In part 2, 2 injection techniques were applied with 1 selected local anesthetic on 47 piglets from 10 litters. In part 3, the most effective local anesthetics and injection techniques identified in the first two parts were used [10][11][12]. In addition, local anesthesia in part 3 was combined with systemic analgesia.…”

“…The piglets of the sham group (handling only) were also fixed in the castration stand, and an injection was simulated by pressure exerted with the needle cap while the testicles were fixed with the fingers. The one-step fenestrated injection technique (one-step [F] injection) used for comparison in parts 2 and 3 was carried out with a 25-gauge needle (0.5 × 10 mm) that had four lateral openings in addition to the distal opening, two of them proximally and two distally [12]. Thus, during injection, the local anesthetic was simultaneously administered distally into the testicle and proximally into the subcutis of the scrotum.…”

Nociception-Induced Changes in Electroencephalographic Activity and FOS Protein Expression in Piglets Undergoing Castration under Isoflurane Anaesthesia

“…The expression of c-FOS and FOS in neurons of the spinal cord is an established marker to quantify neural activity in response to noxious stimulation postmortem [ 25 , 26 ]. It was applied in pigs as well, and single studies have evaluated FOS expression to investigate pain or nociception, respectively, following piglet castration [ 27 , 28 , 29 , 30 , 31 ].…”