CONTINUOUS TOTAL INTRAVENOUS ANESTHESIA, USING PROPOFOL AND FENTANYL IN AN OPEN-THORAX RABBIT MODEL - EVALUATION OF CARDIAC CONTRACTILE FUNCTION AND BIOCHEMICAL ASSESSMENT

Effects are reported of an anesthetic protocol involving use of predet ermined intravenous (i.v.)-administered drug doses during acute experi mental procedures in vagotomized, New Zealand White rabbits with open thorax (n = 20) in a nonsurvival study. After induction of anesthesia by intramuscular (i.m.) administration of ketamine hydrochloride (25 m g/kg of body weight) and xylazine hydrochloride (15 mg/kg), continuous total intravenous anesthesia (TIVA) with propofol (0.6 mg.kg(-1).min( -1)), fentanyl (0.48 mu g.kg(-1).min(-1)) and the neuromuscular agent vecuronium bromide (0.003 mg.kg(-1).min(-1)) was maintained. Oxygenati on conditions, acid-base balance, biochemical and hemodynamic variable s, and cardiac contractile function were assessed. Measurements were m ade and blood analysis was done at the moment of ear vein catheterizat ion (P1); before (P2) cmd after (P3) sternotomy; after complete instru mentation (P4); and at the beginning (TI), in the middle (T2), and at the end (T3) of the experimental protocol, From T1 to T3, heart rate w as kept constant by use of atrial pacing at a rate of 235 +/- 15 beats /min. During surgical preparation and instrumentation, hemoglobin (Hb) concentration decreased from 12.5 +/- 0.9 g/dl (mean +/- SEM) to 7.7 +/- 0.7 g/dl and remained stable thereafter. Blood gas analysis (PO2, PCO2, pH, HCO3, base excess, measured SaO(2)) and measurement of plasm a lactate concentration revealed constant, adequate oxygenation. Plasm a electrolyte values (Na+, Cl, K+, Ca2+) remained within physiologic r anges throughout. Blood glucose concentration increased from 229 +/- 3 0 mg/dl at P1 to 382 +/- 34 mg/dl at P3. At T1, glycemia had returned to normal values and remained stable. Heart rate, blood pressure, vent ricular elastance (Ees), and diastolic stiffness constant (Kc) remaine d stable throughout. Other indices of ventricular function (dP/dt(max) , thickening, ejection duration, and maximal left ventricular pressure ) remained unaltered as well. Left ventricular relaxation (dP/dt(min), tau) did not change. After anesthesia induction by i.m. administratio n of ketamine and xylazine, TIVA with predetermined drug dosages of pr opofol and fentanyl provided stable cardiovascular function for open-t horax long-term experimental observations in a nonsurvival setting.