Injectable anesthetic combinations continue to be used in veterinary anesthesia and surgery and are frequently used for specific programs, such as trap-neuter-release programs, working dog programs, and high-volume spay-neuter programs. Approximately 13.5 million surgeries were performed on dogs and cats at small animal veterinary practices in the United States in 2009,a of which 63.4% were elective ovariohysterectomies and castrations. Many of those surgeries were performed with the use of combinations of injectable anesthetics or combinations of injectable anesthetics and inhalation anesthesia.1,2 In dogs, 2 commonly used combinations of injectable anesthetics are DBTZ and DBK.1–4 On the basis of cardiorespiratory responses in dogs following administration of DBTZ or DBK, both combination treatments were determined to be effective and safe.1–4
In studies conducted to evaluate hemodynamic effects, CO and oxygen content are measured in mixed-venous and arterial blood samples. Those measurements can then be used to calculate Do2 and o2 for tissues. When the oxygen demand of tissues is greater than the oxygen supply to tissues, anaerobic metabolism begins, which results in increased blood l-lactate concentrations.5 Comparison of hemodynamic variables and blood l-lactate concentrations achieved over time after administration of various anesthetic agents or anesthetic combinations provides an effective method for the evaluation of the safety of the anesthetic protocol used. Studies6,7 of the hemodynamic effects in dogs after administration of dexmedetomidine alone and tiletamine-zolazepam alone have been performed. A single dose of dexmedetomidine administered to isoflurane-anesthetized dogs reduced CO and substantially increased SVR.6 Administration of tiletamine-zolazepam (6.6, 13.2, or 19.8 mg/kg, IV) resulted in an increased HR at all doses and increased CO at the 2 higher doses.7 Results of another study8 indicated that dexmedetomidine decreased perioperative myocardial l-lactate concentrations in dogs. To our knowledge, studies to evaluate the hemodynamics and blood l-lactate concentration of dogs following administration of the injectable anesthetic combinations DBTZ and DBK have not been conducted. Therefore, the objective of the study reported here was to compare hemodynamic variables, Do2, o2, and blood l-lactate concentration in dogs following IM administration of DBTZ and DBK.
Diastolic arterial blood pressure
Minimum alveolar concentration
Mean arterial blood pressure
Oxygen extraction ratio
Systolic arterial blood pressure
Systemic vascular resistance
Elena B. Dimova, Market Dynamics Inc, Rollings Meadows, Ill: Personal communication, 2009.
Dexdomitor, Pfizer Animal Health, New York, NY.
Torbugesic, Pfizer Animal Health, New York, NY.
Telazol, Pfizer Animal Health, New York, NY.
Ketaset, Pfizer Animal Health, New York, NY.
SevoFlo, Abbott Animal Health, Abbott Park, Ill.
Gaymar TP Professional, Gaymar Industries Inc, Orchard Park, NY.
Gaymar hot air hugger, Gaymar Industries Inc, Orchard Park, NY.
Seruflo Teflon I.V. catheter, 22-gauge, 1-inch, Terumo Medical Corp, Somerset, NJ.
Swan-Ganz, Edwards Lifesciences Corp, Irvine, Calif.
Datascope DPM7, MindRay, Mahwah, NJ.
PX260 pressure monitoring kit with TruWave transducer, Edwards Lifesciences Corp, Irvine, Calif.
COM-1 CO computer, Edwards Lifesciences Corp, Irvine, Calif.
ABL5 analyzer, Radiometer Medical ApS, Brønshøj, Denmark.
Lactate Pro Meter, Arkray, Quesnel, BC, Canada.
SAS, version 9.1, SAS Institute Inc, Cary, NC.
Equations used to calculate various hemodynamic variables in 5 healthy dogs after IM administration of DBTZ (dexmedetomidine [7.5 μg/kg], butorphanol [0.15 mg/kg], and tiletamine-zolazepam [3 mg/kg]) or DBK (dexmedetomidine [15 μg/kg], butorphanol [0.3 mg/kg], and ketamine [3 mg/kg]).
|SVR (dynes•s/cm5)||80 × (MAP–CVP)/CO|
|PVR (dynes•s/cm5)||80 × (MPAP–PAWP)/CO|
|Cao2 (mL/dL)||(1.34 × Sao2 × CHb) + (0.003 × Pao2)|
|Cvo2 (mL/dL)||(1.34 × Svo2 × CHb) + (0.003 × Pvo2)|
|Do2 (mL/min)||10 × Cao2 × CO|
|o2 (mL/min)||CO × (Cao2–Cvo2)|
|OER (%)||(Cao2-Cvo2) × 100/Cao2|
Cao2 = Arterial oxygen content. CHb = Hemoglobin concentration. Cvo2 = Venous oxygen content. CVP = Central venous pressure. MPAP = Mean pulmonary arterial pressure. PAWP = Mean pulmonary arterial wedge pressure. Pvo2 = Venous partial pressure of oxygen. PVR = Pulmonary vascular resistance. Sao2 = Arterial oxygen saturation. Svo2 = Venous oxygen saturation.
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