STUDY OBJECTIVE: To demonstrate the utility of pulse oximetry in detecting clinically unapparent episodes of arterial desaturation in postoperative cardiac surgical patients and to evaluate the effect of pulse oximetry on ordering arterial blood gas analyses. DESIGN: Prospective, randomized, partially blinded comparison. SETTING: Cardiothoracic surgical intensive care unit. PATIENTS: 35 patients following elective cardiac surgical procedures. INTERVENTIONS: All patients were monitored continuously with pulse oximetry throughout their ICU course. In group 1 patients, the SpO2 data were available at the bedside. In group 2 patients, the SpO2 data were masked at the bedside and monitored at a remote location. MEASUREMENTS AND RESULTS: Utilization of pulse oximetry allowed a significant reduction in arterial blood gas utilization in group 1 (group 1: 12.4 +/- 7.5 blood gas analyses per ICU admission vs group 2: 23.1 +/- 8.8; p = 0.0007) without adverse events. Clinically unapparent desaturations were detected in 7 of 15 patients in group 2. CONCLUSIONS: Pulse oximetry improves patient safety through the detection of clinically unapparent episodes of desaturation and can allow a reduction in the number of blood gas analyses utilized without adverse effects to the patient. This may allow a potential cost savings to the patient.