Continuous Oxygen Saturation Monitoring during Cardiac Catheterization in Adults: Discussion
Arterial hypoxemia may be associated with arrhythmias, myocardial ischemia, myocardial infarction, or congestive heart failure in the patient with coronary artery or valvular heart disease. It is difficult to predict, in any particular patient, the oxygen tension necessary to prevent morbidity; however, an arterial oxygen tension (Pa02) less than 60 mm Hg is considered by most authorities to be hypoxemic. A value for Sa02 of 90 percent corresponds approximately to a Pa02 of 60 mm Hg. In addition, Sa02 of 90 percent is at the steep portion of the oxygen-hemoglobin dissociation curve, where a small decrease in Pa02 will cause a large decrease in the amount of oxygen carried by hemoglobin. Therefore, we considered Sa02 less than 90 percent to represent arterial hypoxemia in our population. diabetes medications
Previous studies have examined arterial blood desaturation in cardiac patients after receiving preoperative medication, cardiac patients undergoing preoperative placement of invasive monitoring lines, and patients undergoing arterial and venous angiography. Various reasons have been suggested for the occurrence of arterial hypoxemia. In our study, 11 (38 percent) of 29 patients had episodes of arterial hypoxemia. Minimum Sa02 was likely to be lower with increasing duration of procedure, lower baseline Sa02, and higher end-diastolic volume. No patient experienced angina or arrhythmias during these episodes, and no other clinical signs of morbidity were observed. Despite this lack of clinical signs of morbidity, such episodes of arterial hypoxemia in other monitored settings, such as a coronary care unit, would warrant intervention. Further, supplemental oxygen administered using a nasal cannula has been shown to increase Sa02 in sedated patients undergoing invasive procedures in other settings.
Coronary cineangiography, left ventriculography, or coronary artery percutaneous transluminal balloon inflation rarely caused a decrease in SaOz (Table 3). The tendency for Sa02 to increase following these maneuvers was remarkable. This increase could be due to the ventilatory maneuvers associated with angiography or the effect of the contrast agent on oxygen-hemoglobin dissociation.