Comparison of Xylazine and Lidocaine Infusion versus Medetomidine Continuous Rate Infusion during General Anesthesia with Isoflurane in Horses Undergoing Emergency Laparotomy.

Simple Summary: General anesthesia has several main goals, including pain management and cardiovascular support. In this retrospective study, we compared two anesthetic protocols for general anesthesia with isoflurane in horses undergoing emergency laparotomy. In the first, xylazine was administered followed by an intraoperative infusion of lidocaine. In the latter, medetomidine was used for preoperative sedation and intraoperative infusion. We reviewed medical records and registered intraoperative variables, recovery time and quality, and short-term outcomes. Horses receiving preanesthetic xylazine sedation followed by intraoperative infusion showed more respiratory depression and a higher heart rate at the beginning of the surgery prior to lidocaine infusion and at the end of the surgery after the discontinuation of lidocaine infusion, which may indicate insufficient analgesia during this time. Arterial pressure was better maintained when medetomidine was used. Recovery quality was similar, with a longer time required for horses receiving medetomidine. We can conclude that both protocols are suitable for general anesthesia with isoflurane in horses undergoing emergency laparotomy. Medetomidine provided more efficient analgesia at the beginning and end of surgery with longer recovery times, more suitable for anxious and young horses to prevent self-injury during this phase. (1) The main goals of general anesthesia include pain management and a safe anesthetic protocol for smooth recovery. In this retrospective study, we compared two anesthetic protocols for general anesthesia with isoflurane during emergency laparotomy: sedation with xylazine and the intraoperative infusion of lidocaine (X group) versus medetomidine as a preoperative sedation and intraoperative infusion (M group). (2) The medical records of horses who underwent emergency laparotomies between 2016 and 2023 were reviewed. According to the anesthetic protocol, patients were allocated to the X or M groups. Data about the horse, signalment, history, and anesthetic variables were analyzed. (3) Group X had a significantly higher heart rate (HR), lower respiratory rate (RR) and mean and diastolic arterial pressure (MAP/DAP). A progressive increase in HR and RR was observed in both groups. Group X underwent a decrease in RR and an increase in DAP. In Group M, a decrease in MAP and DAP was observed. Group M exhibited a longer recovery time with similar recovery scores. Both protocols provided safe anesthesia for emergency laparotomy, with minor cardiovascular and respiratory depression. Minor respiratory depression was detected when xylazine was used, while recovery was longer with medetomidine. [ABSTRACT FROM AUTHOR]