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Effects of dexmedetomidine on pulse pressure variation changes induced by hemorrhage followed by volume replacement in isoflurane‐anesthetized dogs
Author(s) -
Diniz Miriely S.,
TeixeiraNeto Francisco J.,
Cândido Thaísa D.,
Zanuzzo Felipe S.,
Teixeira Lívia R.,
Klein Adriana V.,
do Nascimento Paulo
Publication year - 2014
Publication title -
journal of veterinary emergency and critical care
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.886
H-Index - 47
eISSN - 1476-4431
pISSN - 1479-3261
DOI - 10.1111/vec.12246
Subject(s) - medicine , anesthesia , isoflurane , dexmedetomidine , blood pressure , mean arterial pressure , tidal volume , bolus (digestion) , pulse pressure , hemodynamics , crossover study , stroke volume , heart rate , respiratory system , surgery , sedation , alternative medicine , pathology , placebo
Abstract Objectives To evaluate the effects of dexmedetomidine (DEX) on changes in pulse pressure variation (PPV) induced by hemorrhage followed by volume replacement (VR) during isoflurane (ISO) anesthesia. Design Prospective, randomized, crossover study. Setting Research laboratory at a veterinary teaching hospital. Animals Eight adult dogs. Interventions Anesthesia was maintained with 1.3 times the minimum alveolar concentration (MAC) of ISO alone or ISO with DEX (ISO‐DEX, 1.6 μg/kg [bolus], followed by 2 μg/kg/h). Atropine was administered 30 minutes prior to hemorrhage in the ISO‐DEX treatment. Ventilation was controlled (tidal volume of 12 mL/kg, positive end‐expiratory pressure of 7 cm H 2 O, respiratory rate of 16–20/min) under neuromuscular blockade. After recording baseline data, progressive withdrawal of 10%, 20%, and 30% of blood volume (HV 10 , HV 20 , and HV 30 , respectively [measurements during hemorrhage, indicating x % of blood volume removed]) was followed by VR with autologous blood. Measurements and Main Results In 4 of 8 ISO dogs, hemorrhage decreased mean arterial pressure (MAP) < 60 mm Hg. Based on mean arterial pressure after hemorrhage, dogs were assigned to hypotensive (HG) and normotensive (NG) groups post hoc. During ISO, stroke index and cardiac index decreased with hemorrhage ( P < 0.05), while VR normalized or increased these variables. The PPV (%, mean [range]) was increased by hemorrhage from 7 (5–9) to 20 (12–27) and 27 (17–40) at HV 20 and HV 30 , respectively, only in ISO dogs in the HG; PPV returned to baseline after VR. Dexmedetomidine caused increases in systemic vascular resistance (in dogs in HG and NG), and prevented the increase in PPV with hemorrhage. Conclusions During ISO anesthesia, PPV increases in individuals prone to developing hypotension from hypovolemia. Because DEX prevents the increase in PPV associated with hypovolemia, PPV should not be used to guide VR in dogs that have been given DEX.