A lead II electrocardiogram was used to monitor heart rate and rhythm, and an agent-specific, photo-acoustic gas monitor (Type 1304, Bruel and Kjaer, Naerum, Denmark) measured inspired and expired gases, including end-tidal isoflurane and carbon dioxide.
A catheter was inserted percutaneously into a femoral artery for continuous monitoring of systemic arterial blood pressures and for obtaining arterial blood samples. Two catheters were inserted percutaneously into auricular veins, one for administering fluids and the other for infusing fentanyl or saline. The lungs were mechanically ventilated to maintain normocapnia (Pa CO 235-45 mmHg). Atropine (0.04 mg/kg, intramuscular) was administered to decrease secretions and protect against fentanyl-induced bradycardia.
Animals were placed in lateral recumbency. Each pig was orotracheally intubated, and the concentration of isoflurane was reduced to 2-3% in oxygen delivered at 2 l/min. Unpremedicated, 4-5-month-old, female Yorkshire-cross swine (n = 16), weighing 27 plus/minus 2.2 kg (mean plus/minus SD), were anesthetized via mask with 4-5% isoflurane (Aerrane, Anaquest, Madison, WI) in 100% Oxygen 2delivered at 5 l/min. This study was approved by the Cornell University Animal Care and Use Committee. Minimum alveolar concentration was determined using incremental changes in isoflurane concentrations until gross purposeful movement resulted when using a hemostat stimulus applied for 1 min to a rear dewclaw.
Symbol for female pig mac#
After each infusion, the MAC ISOwas redetermined. A fourth group, control animals, received saline infusions. Plasma fentanyl samples were obtained after 30 min of each infusion, and plasma fentanyl and hemodynamic parameters were obtained immediately before stimulating swine for the final isoflurane concentration used in determining minimum alveolar concentration. The infusions were maintained throughout the period of minimum alveolar concentration determination. Each infusion was maintained for 60 min before initiating minimum alveolar concentration determination. A loading dose of fentanyl preceded each infusion. For each group, baseline MAC ISOwas determined, and three groups received two of three fentanyl infusions as follows: 50 micro gram *symbol* kg sup -1 *symbol* h sup -1 intravenously followed by 100 micro gram *symbol* kg sup -1 *symbol* h sup -1, 50 micro gram *symbol* kg sup -1 *symbol* h sup -1 followed by 200 micro gram *symbol* kg sup -1 *symbol* h sup -1, or 100 micro gram *symbol* kg sup -1 *symbol* h sup -1 followed by 200 micro gram *symbol* kg sup -1 *symbol* h sup -1 (n = 8 for each dosage). Methods: Sixteen swine were randomly assigned to four groups. After each infusion, the MACISO was redetermined.
For each group, baseline MACISO was determined, and three groups received two of three fentanyl infusions as follows: 50 -1 intravenously followed by 100 -1, 50 -1 followed by 200 -1, or 100 -1 followed by 200 -1 (n = 8 for each dosage). Sixteen swine were randomly assigned to four groups.
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