Local Anesthetic for Castration: Maintaining a Balance

Balanced anesthesia (ie, combining different drug classes and regional anesthesia techniques) may reduce hypotension and hypercarbia from excessive anesthetic drugs and provide additional perioperative analgesia. Forty-two dogs were divided into 2 groups: group L received intratesticular lidocaine injections 5 minutes before surgical castration, and group S received an equal volume of saline. There were no significant differences in baseline heart rate (HR), mean arterial pressure (MAP), or respiratory rate (RR). Dogs in group L had lower maximum values for HR and MAP compared with dogs in group S and smaller increases in HR during exteriorization of the first testis. Differences in MAP existed during all surgical events and time points, with less change in MAP for group L during skin excision, exteriorization of the first testis, and clamping of both spermatic cords. Although there was no significant difference in magnitude of increase of intraoperative RR, group S reached its highest RR earlier than group L. There were no significant differences in requiring additional propofol or rescue analgesia. Lidocaine effects likely wore off before completing surgery, explaining why there were no significant differences in HR and RR during second testis removal or in the magnitude of intraoperative RR or requirement for rescue analgesia. However, intratesticular lidocaine did provide decreased response to noxious stimuli based on HR, RR, and MAP.

Commentary

Unfortunately, locoregional anesthetic techniques are slow to gain popularity in small animal practice. Intratesticular infusion of local anesthetics before castration, routine in large animal medicine, is gaining interest in small animal practice. Although this study lacked sufficient numbers, it does support anecdotal evidence that intratesticular local anesthetic infusion before surgical castration in dogs provides intraoperative analgesia. This technique can be a simple, inexpensive, and quick analgesic option in canine surgical castration.—Andrew Claude, DVM, DACVAA

Source

Intratesticular lidocaine reduces the response to surgical castration in dogs. Huuskonen V, Hughes JM, Bañon EE, West E. VET ANAESTH ANALG 40:74-82, 2013.