OBJECTIVE: To elaborate constant rate infusion (CRI) protocols for xylazine (X) and xylazine/butorphanol (XB) which will result in constant sedation and steady xylazine plasma concentrations. STUDY DESIGN: Blinded randomized experimental study. ANIMALS: Ten adult research horses. METHODS: Part I: After normal height of head above ground (HHAG = 100%) was determined, a loading dose of xylazine (1 mg kg(-1) ) with butorphanol (XB: 18 μg kg(-1) ) or saline (X: equal volume) was given slowly intravenously (IV). Immediately afterwards, a CRI of butorphanol (XB: 25 μg kg(-1) hour(-1)) or saline (X) was administered for 2 hours. The HHAG was used as a marker of depth of sedation. Sedation was maintained for 2 hours by additional boluses of xylazine (0.3 mg kg(-1)) whenever HHAG >50%. The dose of xylazine (mg kg(-1) hour(-1)) required to maintain sedation was calculated for both groups. Part II: After the initial loading dose, the calculated xylazine infusion rates were administered in parallel to butorphanol (XB) or saline (X) and sedation evaluated. Xylazine plasma concentrations were measured by HPLC-MS-MS at time points 0, 5, 30, 45, 60, 90, and 120 minutes. Data were analyzed using paired t-test, Wilcoxon signed rank test and a 2-way anova for repeated measures (p < 0.05). RESULTS: There was no significant difference in xylazine requirements (X: 0.69, XB: 0.65 mg kg(-1) hour(-1)) between groups. With treatment X, a CRI leading to prolonged sedation was developed. With XB, five horses (part I: two, part II: three) fell down and during part II four horses appeared insufficiently sedated. Xylazine plasma concentrations were constant after 45 minutes in both groups. CONCLUSION: Xylazine bolus, followed by CRI, provided constant sedation. Additional butorphanol was ineffective in reducing xylazine requirements and increased ataxia and apparent early recovery from sedation in unstimulated horses. CLINICAL RELEVANCE: Data were obtained on unstimulated healthy horses and extrapolation to clinical conditions requires caution.
OBJECTIVE: To elaborate constant rate infusion (CRI) protocols for xylazine (X) and xylazine/butorphanol (XB) which will result in constant sedation and steady xylazine plasma concentrations. STUDY DESIGN: Blinded randomized experimental study. ANIMALS: Ten adult research horses. METHODS: Part I: After normal height of head above ground (HHAG = 100%) was determined, a loading dose of xylazine (1 mg kg(-1) ) with butorphanol (XB: 18 μg kg(-1) ) or saline (X: equal volume) was given slowly intravenously (IV). Immediately afterwards, a CRI of butorphanol (XB: 25 μg kg(-1) hour(-1)) or saline (X) was administered for 2 hours. The HHAG was used as a marker of depth of sedation. Sedation was maintained for 2 hours by additional boluses of xylazine (0.3 mg kg(-1)) whenever HHAG >50%. The dose of xylazine (mg kg(-1) hour(-1)) required to maintain sedation was calculated for both groups. Part II: After the initial loading dose, the calculated xylazine infusion rates were administered in parallel to butorphanol (XB) or saline (X) and sedation evaluated. Xylazine plasma concentrations were measured by HPLC-MS-MS at time points 0, 5, 30, 45, 60, 90, and 120 minutes. Data were analyzed using paired t-test, Wilcoxon signed rank test and a 2-way anova for repeated measures (p < 0.05). RESULTS: There was no significant difference in xylazine requirements (X: 0.69, XB: 0.65 mg kg(-1) hour(-1)) between groups. With treatment X, a CRI leading to prolonged sedation was developed. With XB, five horses (part I: two, part II: three) fell down and during part II four horses appeared insufficiently sedated. Xylazine plasma concentrations were constant after 45 minutes in both groups. CONCLUSION:Xylazine bolus, followed by CRI, provided constant sedation. Additional butorphanol was ineffective in reducing xylazine requirements and increased ataxia and apparent early recovery from sedation in unstimulated horses. CLINICAL RELEVANCE: Data were obtained on unstimulated healthy horses and extrapolation to clinical conditions requires caution.
Authors: Alice Rodrigues de Oliveira; Miguel Gozalo-Marcilla; Simone Katja Ringer; Stijn Schauvliege; Mariana Werneck Fonseca; Pedro Henrique Esteves Trindade; José Nicolau Prospero Puoli Filho; Stelio Pacca Loureiro Luna Journal: Front Vet Sci Date: 2021-02-16