RESUMEN
This study was designed to determine the significance of changes in mixed venous oxygen saturation (SVO2) associated with aortic surgery. In 12 patients undergoing aortic aneurysm repair, SVO2 was monitored using a fiberoptic pulmonary arterial catheter, and oxygen uptake (VO2) was measured at 2-min intervals by a mass-spectrometer system. Excluding the phase of aortic clamping, VO2, hemoglobin, and arterial oxygen saturation were moderately stable during anesthesia, and changes in SVO2 were correlated with changes in cardiac output (CO). SVO2 remained stable during infrarenal aortic clamping, but increased during supraceliac aortic clamping. During the first three postoperative hours, changes in SVO2 were opposite to changes in VO2 and CO. They were especially marked in the patients whose preoperative left ventricular ejection fraction was less than 50%. We conclude that SVO2 changes are an indicator of same-direction changes in CO during general anesthesia except during periods of aortic clamping. The interpretation of SVO2 changes is more complex during aortic clamping and during the immediate postoperative period, two critical periods during which simultaneous changes in VO2 and CO occur.
Asunto(s)
Aorta Abdominal/cirugía , Consumo de Oxígeno , Oxígeno/sangre , Anciano , Gasto Cardíaco , Humanos , Periodo Intraoperatorio , Persona de Mediana Edad , Periodo Posoperatorio , VenasRESUMEN
Energy expenditure (EE) was measured, during 3 consecutive days, in six patients suffering from acute pancreatitis. Measurements were achieved postoperatively, under mechanical ventilation, using a mass spectrometer system. EE represented 1.49 times (range: 1.08-1.78) the predicted resting energy expenditure (PREE) according to the reevaluated Harris-Benedict equation. There was a weak positive correlation between EE and core temperature and a negative correlation between EE and nitrogen balance. EE/PREE was not different between septic and nonseptic patients (1.58 +/- 0.06 vs. 1.39 +/- 0.07). The calculations of nutrient oxidation rate indicated a high protein catabolic rate, a neoglucogenesis, and a lipolysis.
Asunto(s)
Metabolismo Energético , Pancreatitis/metabolismo , Enfermedad Aguda , Adulto , Anciano , Femenino , Glucosa/metabolismo , Humanos , Metabolismo de los Lípidos , Masculino , Persona de Mediana Edad , Nitrógeno/metabolismo , Proteínas/metabolismoRESUMEN
In seven postoperative patients with normal preoperative pulmonary function tests, we evaluated the oxygen cost of breathing (VO2resp) during continuous positive pressure ventilation (CPAP) and during a 15 cm H2O inspiratory pressure support ventilation (IPSV). For both periods, VO2 resp was estimated as the difference between total oxygen uptake of the period (VO2tot), measured by a mass-spectrometer system, and that during controlled ventilation. During CPAP ventilation, VO2resp was found to be 11.2 +/- 1.4 percent of VO2tot. During IPSV, VO2resp was found insignificant. It is concluded that a 15 cm H2O IPSV takes over the major part of the work of breathing in postoperative patients without preexisting pulmonary disease.