BACKGROUND: A thoracic epidural combined with general anesthesia may reduce the oxygen demand of the heart by cardiac sympathetic blockade, but it may also reduce the systemic and cardiac oxygen delivery due to hypoperfusion which is critical to patients with significant coronary lesions. This study was done to investigate the effects of thoracic epidural anesthesia on the systemic and cardiac oxygen supply/demand balance during coronary occlusion in dogs. METHODS: In 10 dogs, the left circumflex coronary artery was occluded, and then thoracic epidural anesthesia was given at the T5-6 or T6-7 level with 5 ml of 0.5% bupivacaine to block T1-T12 through the surgically introduced epidural catheter. Hemodynamic parameters and arterial, mixed venous and coronary sinus blood samples were obtained at baseline and 30 minutes after coronary occlusion. The same parameters were also measured at 30, 60, 90, 120 and 150 minutes after the epidural blockade. An epicardial 2D-echocardiogram was done by a cardiologist at baseline, 30 minutes after occlusion and 1 hour after the epidural blockade. RESULTS: Systemic oxygen delivery (O2 flux) was decreased after epidural anesthesia (p < 0.05), but oxygen consumption (VO2) was maintained throughout the experimental periods. Although the systemic oxygen extraction ratio (O2ER) was not changed, cardiac O2ER was increased at 90, 120 and 150 minutes after epidural anesthesia (p < 0.05). The end-diastolic noncontractile area of the left ventricle was increased, pulmonary capillary wedge pressure was increased 90 minutes after epidural anesthesia and cardiac output was decreased 120 minutes after epidural anesthesia (p < 0.05). CONCLSIONS: In the experimental canine model of coronary occlusion, thoracic epidural anesthesia induces diminished systemic oxygen delivery without deteriorating oxygen supply/demand balance. However, as PsO2 and SsO2 diminished and the noncontractile left ventricular area increased after epidural anesthesia in the setting of acute coronary occlusion, perioperative use of thoracic epidural anesthesia in patients of coronary disease should be done carefully in order not to aggravate myocardial ischemia.
Anesthesia, Epidural* ; Anesthesia, General ; Animals ; Bupivacaine ; Cardiac Output ; Catheters ; Coronary Disease ; Coronary Occlusion* ; Coronary Sinus ; Coronary Vessels ; Dogs* ; Heart ; Heart Ventricles ; Hemodynamics ; Humans ; Myocardial Ischemia ; Oxygen Consumption ; Oxygen* ; Pulmonary Wedge Pressure

PURPOSE: To assess the midterm results of the hydroxyapatite hip system with acetabular cups, with particular emphasis upon cup wear and loosening, using a computer assisted-3 dimensional technique. MATERIALS AND METHODS: From March 1992 to December 1996, 52 patients (61 hips) were available for inclusion in this study after an average duration of follow up of 6 years and 4 months. Clinical evaluation was performed using the Harris hip scoring system. Initial postoperative and long term follow up films were digitized, and 2 dimensional linear and 3 dimensional wear was measured by using a computer assisted-3 dimensional technique. Acetabular bone changes are described using previous published methods. RESULTS: An analysis of the clinical results showed a mean Harris hip score of 47.2 points preoperatively and 89.8 points at the final visit. The mean polyethylene 3D-linear wear rate was 0.26 mm/year and mean volumetric wear rate was 105.9 mm3/year. In 16 hips (26.2%) the linear wear rate was more than 0.3 mm/year (0.30-0.74 mm/year). Osteolytic changes of the acetabulum were recorded in 51% around acetabular cups, in which considerable wear of the acetabular polyethylene was evident by the five-year radiographic findings. CONCLUSION: Midterm results of hydroxyapatite coated acetabular cups were disappointing in terms of acetabular cup and liner wear, despite early accelerated bone remodeling by hydroxyapatite and excellent early clinical results.
Acetabulum* ; Arthroplasty, Replacement, Hip ; Bone Remodeling ; Durapatite* ; Follow-Up Studies ; Hip* ; Humans ; Osteolysis* ; Polyethylene