We studied canine left ventricular contractile performance following 15 min of portal vein occlusion by analyzing the end-systolic pressure diameter relationship (ESPDR) which many investigators have reported as being independent of changes in preload and afterload but sensitive to changes in ventricular contractility. Portal vein occlusion for 15 min decreased the mean arterial pressure, left ventricular peak systolic pressure, and cardiac index, while the release of the occlusion gradually increased these values, although it did not restore them to the control values. The systemic vascular resistance index increased during portal vein occlusion and returned to the control values after release. Left ventricular end diastolic diameter decreased during portal clamping and returned to the control values after release. ESPDR and percent shortening were not significantly changed during or after portal clamping. These results indicate that the decrease in blood pressure during portal vein occlusion was not due to a reduction in myocardial contractility but rather was due to a reduction in preload.

capacity (VC 1810 ml; %VC 65.6%; forced expiratory volume in 1 s (FEV 1.0 ) 1700 ml; FEV 1.0 % 88.1%). Preoperative arterial blood gas analysis revealed posture-dependent hypoxemia and mild alveolar hypoventilation (in the supine position P a o 2 55 mmHg, P a co 2 45 mmHg; in the sitting position P a o 2 68 mmHg, P a co 2 43 mmHg).Because sleep apnea syndrome was highly suspected, we performed a nocturnal sleep study while monitoring polysomnography (Respisomnograph; Non-Invasive Monitoring Systems, Miami Beach, FL, USA), pulse oxymeter (Oxypal; Nihon Kohden, Tokyo, Japan), ECG, direct arterial pressure, central venous pressure and pulmonary arterial pressure. There were 132 apneic episodes during 6 h (11.4% of the observation period), which; according to the criteria for sleep apnea syndrome of five or more apneic episodes per hour of sleep [3], qualified the patient as having sleep apnea syndrome. Oxygen saturation level (S p o 2 ) decreased from 80% to 70%-75% during sleep. Furthermore, there were several episodes of severe desaturation (S p o 2 50%) associated with increases in heart rate, arterial blood pressure, pulmonary arterial pressure and central venous pressure, and a decrease in the ST level. Mean pulmonary arterial pressure ranged between 35 and 40 mmHg during the severe desaturation episodes.Atropine (0.5 mg) was administered intravenously prior to the induction of general anesthesia. After 10 min preoxygenation, 100 µg fentanyl was given intravenously, followed by 150 mg propofol and 15 mg vecuronium to facilitate tracheal intubation. Immediately after placement of a 37 Fr left-sided double-lumen endobronchial tube (DLT), continuous infusion of propofol was started at a rate of 10 mg/kg per h. For the weight of the patient, we used a corrected body weight according to the equation reported by Servin et al. [4]: corrected body weight ϭ ideal body weight ϩ 0.4 ϫ (actual body weight Ϫ ideal body weight)

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