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Hemodynamic Responses of Horses to Anesthesia and Surgery, Before and After Administration of a Low Dose of Endotoxin
Author(s) -
WAGNER ANN E.,
DUNLOP COLIN I.,
WERTZ ETTA M.,
CHAPMAN PHILLIP L.,
BAXTER GARY M.,
KLOPP LISA S.
Publication year - 1995
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.1995.tb01300.x
Subject(s) - medicine , anesthesia , xylazine , ketamine , hemodynamics , halothane , heart rate , blood pressure , vascular resistance , surgery
Seven horses, which were part of an investigation of the effect of endotoxin administration on vascular reactivity, were anesthetized on two separate occasions for surgical excision of 4‐cm sections of palmar digital artery and vein. On the first occasion, the horses were given an infusion of 1 L 0.9% NaCl solution intravenously (IV) just before induction of anesthesia (control); on the second occasion, the horses received an infusion of 1 L 0.9% NaCl containing Escherichia coli endotoxin, 0.1 μg/kg (endotoxin). On both occasions, anesthesia was induced with xylazine, guaifenesin, and ketamine, and maintained with halothane in oxygen. Hemodynamic measurements were made with the horses under anesthesia immediately before beginning surgery (period 1), during skin incision (period 2), during dissection and excision of the vessels (period 3), during skin suturing (period 4), and after completion of surgery during bandaging (period 5). Hemoglobin concentration and mixed venous oxygen content were greater at all periods in horses that received endotoxin. Otherwise, there were no significant differences in hemodynamic parameters between control horses and horses administered endotoxin before beginning surgery (period 1). During surgery and bandaging, horses administered endotoxin had significantly higher heart rate (periods 3, 4, and 5), cardiac index (periods 3, 4, and 5), and oxygen delivery (periods 2, 3, 4, and 5) than did control horses, and mean arterial blood pressure (period 2) and systemic vascular resistance (periods 2, 3, 4, and 5) were less than in control horses. Compared with period 1, surgical stimulation in control horses was associated with increased mean arterial blood pressure and systemic vascular resistance (periods 2, 3, 4, and 5), but cardiac index and oxygen delivery were decreased (periods 3, 4, and 5). In contrast, horses administered endotoxin responded to surgical stimulation with increased mean arterial blood pressure (periods 2, 3, 4, and 5) and vascular resistance (periods 4 and 5), as well as a heart rate‐induced increase in cardiac index (periods 2, 3, 4, and 5) compared with period 1; oxygen delivery also increased (periods 2, 3, 4, and 5) during surgery in the endotoxin group. This study documents some of the differences in the response to anesthesia and surgery between normal horses and those that have received endotoxin.