On line monitoring of mixed venous oxygen saturation after cardiothoracic surgery

Abstract

On line monitoring of MVO2 sat. in vivo by means of fibreoptic reflectometry was studied in 19 patients as to its predictive value during the postoperative course after thoracotomy for periods up to 60 hours. In all but one of the 10 patients with MVO2 sat. less than 65% for at least one hour complications occurred. A fall of MVO2 sat. of more than 5% or a value below 60% predicted a period of hypotension in six patients. In two of them this coincided with a period of ventricular arrhythmias. In those with MVO2 sat. greater than 65% no postoperative complications such as arrhythmias, shock, respiratory dysfunction or oliguria took place. Since MVO2 sat. and cardiac index were shown to deviate in parallel (r=0.78; n=28) the former may be used as an indicator of the latter. Respiratory dysfunction could also immediately be detected by decreases in MVO2 sat. Turning a patient to his side at times caused a fall of MVO2 sat. of more than 10%. Furthermore, MVO2 sat. reflected immediately beneficial or detrimental effects of blood transfusion or inotropic agents. It is concluded that continually measured MVO2 sat. is a helpful adjunct in postoperative management. In fact it may be the best early warning indicator of the patient's course after cardiothoracic surgery, although extensive clinical experience needs to be collected before its definitive value will be known.