[Oximetry in veterinary anesthesia: the continuous determination of mixed venous oxygen saturation in dogs and horses].

The continuous fiberoptical measurement of the mixed venous partial oxygen saturation is described. It is an enrichment of the diagnostical possibilities in veterinary medicine. In the horse it is of great interest, because disturbances of the pulmonary gas exchange and the myocardial function are common in the anaesthetised horse, and reliable methods of assessing the cardiac output are rare. Using this monitoring technique in nearly 100 equine high risk patients facilitated insight into the complex changes of the pulmonary, cardiac and circulatory function in the anaesthetised horse. The registered data are the basis of the presented case reports. Values measured "behind the tissue" are influenced by the oxygen supply and the oxygen consumption within the periphery. Changes of the mixed venous oxygen status can be caused by a disturbance of the arterial oxygen status, by a insufficient performance of the cardiovascular system or by a change in metabolic activity. Being a multifactorial influenced parameter the mixed venous oxygen saturation can only be interpreted in connection with other parameters. The mixed venous oxygen status gives global information about the whole organism, but it is not able to inform about the oxygen supply of single organs. From our own personal experience it reflects an aggravation of the patient very early and reliable.