Monitoring Of Blood Oxygen Saturation Research Articles

Continuous monitoring of blood oxygen saturation of internal jugular vein as a useful indicator for selective cerebral perfusion during aortic arch replacement

We continuously monitored blood oxygen saturation in the internal jugular vein during selective cerebral perfusion for aortic arch operations and evaluated its efficacy as an indicator of cerebral oxygen metabolism. The selective cerebral perfusion method was applied in 11 patients who underwent operations for aortic arch replacement. Blood oxygen saturation in the internal jugular vein was continuously monitored at the bulbus jugularis with a fiberoptic catheter during the operation. Perfusion flow of 500 ml/min was continued for 134.7 +/- 14.9 minutes under moderate hypothermia at 25 degrees C, and bilateral temporal arterial pressure was 40 to 60 mm Hg. Blood gas data were used to estimate oxygen consumption, oxygen extraction ratio, and lactate uptake in the cerebrum. No patients had postoperative cerebral complications. Cerebral oxygen consumption was 2.93 +/- 0.4 ml/min/100 gm under general anesthesia at 36 degrees C. While selective cerebral perfusion at 25 degrees C decreased consumption to 0.92 +/- 0.39 ml/min/100 gm, it fell to about 30% of its former value. Blood oxygen tension in the internal jugular vein showed no significant correlation with rectal temperature. Selective cerebral perfusion did not significantly affect cerebral lactate uptake. In contrast, blood oxygen saturation in the internal jugular vein was significantly affected by temperature and cerebral flow during selective cerebral perfusion, and blood oxygen saturation in the internal jugular vein correlated closely with cerebral oxygen extraction ratio (r = 0.91). Cerebral oxygen metabolism was thus well maintained, and continuous monitoring of blood oxygen saturation in the internal jugular vein was found to serve as a useful indicator under selective cerebral perfusion during operations for aortic arch replacement.

Role of adenosine in pathogenesis of anginal pain.

The intravenous infusion of adenosine provokes anginalike chest pain. To establish its origin, an intracoronary infusion of increasing adenosine concentrations was given in 22 patients with stable angina pectoris. During adenosine infusion, 20 patients had chest pain without electrocardiographic signs of ischemia. They all reported that the chest pain was similar to their usual anginal pain. In 10 of the 22 patients adenosine was also infused into the right atrium, but it never produced symptoms at the doses that had provoked chest pain during intracoronary infusion. In seven other patients, the intracoronary adenosine infusion was repeated after intravenous administration of aminophylline, an antagonist of adenosine P1-receptors. Aminophylline decreased the severity of adenosine-induced chest pain (assessed with a visual analog scale) from 42 +/- 22 to 23 +/- 17 mm (p less than 0.002). In the remaining five of the 22 patients, monitoring of blood oxygen saturation in the coronary sinus during intracoronary adenosine administration showed that maximum coronary vasodilation was achieved at doses lower than those responsible for chest pain. A single-blind, placebo-controlled, randomized trial of the effect of aminophylline on exercise-induced chest pain was also performed in 20 other patients with stable angina. Aminophylline, compared with placebo, decreased the severity of chest pain at peak exercise from 67 +/- 21 to 51 +/- 23 mm (p less than 0.02), despite the achievement of a similar degree of ST-segment depression. Finally, the effect of intravenous adenosine was compared in 10 patients with predominantly painful myocardial ischemia and in 10 patients with predominantly silent ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Sevrage de la ventilation artificielle: intérêt du monitorage continu de la S o2

Weaning from mechanical ventilation is particularly difficult in patients with combined cardiac and respiratory failure. Continuous monitoring of mixed venous blood oxygen saturation (Sv̄ 2) redefines weaning in terms of tissue oxygenation. A stable Sv̄ 2>60% during weaning is a reliable index of weanability. However, further studies are required to establish a tolerance threshold for Sv̄ 2 during weaning. In the limited experience reported here, an immediate and abrupt fall in Sv̄ 2, when the patient started to breathe spontaneously was invariably associated with difficulties in weaning. In some patients, other signs of left ventricular dysfunction rapidly ensued, with a fall in cardiac index. Weaning remained possible if the treatment was capable of increasing cardiac output and normalizing Sv̄ 2. If, during spontaneous breathing, Sv̄ 2 remained stable in the 50–55% range, with no significant decrease in cardiac output, abrupt and unpredictable drops of Sv̄ 2 under 40% range occurred. Such falls always preceded signs of tissue hypoxia, leading to a resumption of controlled mechanical ventilation. However, further studies are required to fully delineate the role of Sv̄ 2 in the fine tuning of inotropic support and ventilatory assistance in the difficult weaning of patients recovering from cardio-respiratory failure.

Value of continuous monitoring of mixed venous blood oxygen saturation in the management of critically ill patients.

Continuous SVO2 measurement using a triple-lumen flow-directed pulmonary artery catheter with fiberoptic filaments has been described. The purpose of this study was to identify whether the availability of SVO2 as a continuously monitored signal could have altered patient management decisions made by the medical staff on the basis of clinical and laboratory data and signals currently used in ICUs. Subjects for this study were 15 critically ill patients requiring arterial cannulation and insertion of a pulmonary artery catheter. The central processor of the device was placed in a specially constructed wooden box in such a way as to conceal the digital display of the signal. The folded paper used for a continuous 72-h recording of the signal was also not available to the personnel managing the patient. In detailed and repeated assessments of the patient's status, the medical team managing the patient entered on a special form all clinical and laboratory data as well as medical decisions made. At the end of each study the SVO2 value recorded at each assessment was entered on the form. The investigators then determined whether knowledge of SVO2 would have changed the clinical decision actually made. The SVO2 signal was continuously recorded for a total of 1065 h and 173 individual assessments. The SVO2 signal as measured by the Oximetrix device was compatible with decisions made on the basis of standard measurements used in the ICU in a majority of cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous Monitoring of Blood Oxygen Saturation During Extracorporeal Circulation

The Bentley “oxysat” oxygen saturation meier is a small, digital, battery-operated, dual wave length, optical device. Two probes, arterial and venous, are mounted into the extra corporeal blood line during openheart surgery. Correlation tests between van Slyke, Lex O2 con, and calculated saturations, have shown accuracy and repeatability of oxygen saturation values during extracorporeal circulation on twenty cardiac patients. The meter proved useful during extracorporeal circulation by providing access to immediate observation of blood saturation and valuable trend data in the course of perfusion, and allowing better control of gas and blood flow during bypass. It also helped prevent excessive pO2s, gaseous microemboli, effort factor during blood sampling, and blood waste.