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Cardiovascular Effects After Epidural Injection of Xylazine in Isoflurane‐Anesthetized Dogs
Author(s) -
GREENE STEPHEN A.,
KEEGAN ROBERT D.,
WEIL ANN B.
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.tb01332.x
Subject(s) - medicine , isoflurane , xylazine , anesthesia , cardiac output , arterial blood , central venous pressure , heart rate , saline , blood pressure , mean arterial pressure , vascular resistance , stroke volume , hemodynamics , ketamine
The cardiovascular effects following epidural injection of xylazine or isotonic saline during isoflurane anesthesia were assessed in six healthy dogs. Dogs were anesthetized with isoflurane in O 2 and maintained at 2.0% end‐tidal concentration. Ventilation was controlled to maintain PaCO 2 at 35 to 45 mm Hg. The dorsal pedal artery was cannulated for measurement of arterial blood pressure (AP)(systolic AP, mean AP, diastolic AP) and for blood sample collection. Arterial pH and blood gas tensions (PaO 2 and PaCO 2 ) were determined. Cardiac output was measured by thermodilution. The electrocardiogram (ECG), heart rate (HR), core body temperature, central venous pressure (CVP), mean pulmonary AP, and end‐tidal isoflurane concentration (ETISO) and CO 2 tension (ETCO 2 ) were monitored. Systemic vascular resistance (SVR), arterial HCO 2 concentration, base balance, and cardiac index (CI) were calculated. After baseline measurements were taken, either xylazine (0.2 mg/kg) in 5 mL isotonic saline or 5 mL of isotonic saline was injected into the lumbosacral epidural space. Data were then recorded at 5, 15, 30, 45, 60, 75, 90, 105, and 120 minutes after epidural injection. Data were analyzed by two‐way analysis of variance (ANOVA) for repeated measures. When significant differences were encountered, mean values were compared using Bonferroni's test. The level of significance was set at P <.05. Mean values for diastolic AP decreased at 90 and 120 minutes compared with the mean value at 15 minutes after epidural injection of xylazine. No differences were detected at any time or between treatments for HR, systolic AP, mean AP, CVP, CI, SVR, mean pulmonary AP, temperature, ETCO 2 , ETISO, arterial pH, PaCO 2 , PaO 2 , plasma bicarbonate concentration, or base balance. Results of this study indicate that epidural injection of xylazine (0.2 mg/kg) is associated with minimal cardiovascular side effects during isoflurane anesthesia in mechanically ventilated dogs.