Randomized evaluation of pulse oximetry in 20,802 patients: II. Perioperative events and postoperative complications. Perioperative monitoring with pulse oximetry and late postoperative cognitive dysfunction. Pulse oximetry in the postoperative care of cardiac surgical patients. A randomized controlled trail. Hypoxaemia is reduced by pulse oximetry monitoring in the operating theatre and in the recovery room. The impact of continuous pulse oximetry monitoring on intensive care unit admissions from a postsurgical care floor.
The authors describe the effect of pulse oximetry monitoring on the frequency of unanticipated perioperative events, changes in patient care, and the rate of postoperative complications in a prospective randomized study.
                The study included 20,802 surgical patients in Denmark randomly assigned to be monitored or not with pulse oximetry in the operating room (OR) and postanesthesia care unit (PACU).
                During anesthesia and in the PACU, significantly more patients in the oximetry group had at least one respiratory event than did the control patients. This was the result of a 19-fold increase in the incidence of diagnosed hypoxemia in the oximetry group than in the control group in both the OR and PACU (P < 0.00001). In the OR, cardiovascular events were observed in a similar number of patients in both groups, except myocardial ischemia (as defined by angina or ST-segment depression), which was detected in 12 patients in the oximetry group and in 26 patients in the control group (P < 0.03). Several changes in PACU care were observed in association with the use of pulse oximetry. These included higher flow rate of supplemental oxygen (P < 0.00001), increased use of supplemental oxygen at discharge (P < 0.00001), and increased use of naloxone (P < 0.02). The rate of changes in patient care as a consequence of the oximetry monitoring increased as the American Society of Anesthesiologists physical status worsened (P < 0.00001). One or more postoperative complications occurred in 10% of the patients in the oximetry group and in 9.4% in the control group (difference not significant). The two groups did not differ significantly in cardiovascular, respiratory, neurologic, or infectious complications. The duration of hospital stay was a median of 5 days in both groups (difference not significant). An equal number of inhospital deaths were registered in the two groups. Questionnaires, completed by the anesthesiologists at the five participating departments, revealed that 18% of the anesthesiologists had experienced a situation in which a pulse oximeter helped to avoid a serious event or complication and that 80% of the anesthesiologists felt more secure when they used a pulse oximeter.
                This study demonstrated that pulse oximetry can improve the anesthesiologist's ability to detect hypoxemia and related events in the OR and PACU and that the use of the oximeter was associated with a significant decrease in the rate of myocardial ischemia. Although monitoring with pulse oximetry prompted a number of changes in patient care, a reduction in the overall rate of postoperative complications was not observed. In a randomized, blinded clinical study, we have used objective and subjective measures to determine if perioperative monitoring with pulse oximetry--by virtue of its potential to lessen hypoxaemia--would decrease late postoperative cognitive dysfunction. We investigated 736 adult patients undergoing elective procedures (other than cardiac, neurosurgical or for cancer) under regional or general anaesthesia, allocated randomly to undergo (group I) or not to undergo (group II) pulse oximetry monitoring in the operating theatre and recovery room. Cognitive function was evaluated using the Wechsler memory scale (WMS) and continuous reaction time (RT) test the day before surgery, and on the 7th day after operation or at discharge if that occurred before postoperative day 7. A questionnaire sent 6 weeks after surgery elicited patients' subjective perceptions regarding cognitive abilities. There were no significant differences between the two groups in either the total WMS score, the score for each WMS subtests or RT test. The questionnaire revealed that 7% in group I and 11% in group II believed cognitive abilities had decreased (ns). For the 40 patients whose WMS scores were 10 points less after than before operation, a follow-up study was undertaken 3 months after surgery. At that time, the median WMS score had returned to the preoperative value. We conclude that, for these 736 patients, subjective and objective measures did not indicate less postoperative cognitive impairment after perioperative monitoring with pulse oximetry. 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.
                Prospective, randomized, partially blinded comparison.
                Cardiothoracic surgical intensive care unit.
                35 patients following elective cardiac surgical procedures.
                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.
                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.
                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. To determine the impact of pulse oximeter monitoring on the incidence, severity and duration of hypoxaemia in the operating theatre (OT) and in the recovery room (RR), we investigated 200 patients in a randomized study. The extent of hypoxaemia in the OT was compared with that in the RR. Adult inpatients were allocated randomly to two groups: group I, pulse oximeter data and alarms "available"; group II, these data "unavailable" to the anaesthesia team and RR staff. Hypoxaemia was graded into four values of oxyhaemoglobin saturation (SpO2). The incidence of hypoxaemia was reduced significantly in group I in both OT and RR. In the OT, five patients in group II suffered SpO2 less than 76% compared with none in group I (P less than 0.02). In group II in the RR, seven patients suffered SpO2 less than 81%; three of these had SpO2 less than 76%. No patients in group I exhibited such small values of saturation. The smallest recorded SpO2 in the OT and the RR was significantly greater in group I. The cumulative duration of hypoxaemia was significantly less in group I in the RR, but not in the OT. The incidence and severity of hypoxaemia in the OT and in the RR were comparable, whereas the cumulative duration of hypoxaemia was significantly greater in the RR than in the OT. The occurrence of hypoxaemia in an individual patient in the OT significantly increased this patient's risk of suffering hypoxaemia in the RR. We conclude that the extent of hypoxaemia, especially in the RR, may be reduced significantly by pulse oximeter monitoring, but even with the information provided, some patients still develop hypoxaemia. Continuous pulse oximetry (CPOX) has the potential to increase vigilance and decrease pulmonary complications and thus decrease intensive care unit (ICU) admissions. In a randomized nonblinded study of 1219 subjects we compared the effects of CPOX and standard monitoring on the rate of transfer to an ICU from a 33-bed postcardiothoracic surgery care floor. There was no difference in the rate of ICU readmission between the CPOX and standard monitor groups. Despite older age and comorbidity, estimated cost to time of censoring (enrollment to completion of the study) was less in the monitored patients who required ICU transfer than in the unmonitored patients who required ICU transfer (mean estimated cost difference of 28,195 dollars; P = 0.04). Use of CPOX altered the reasons that patients were transferred to an ICU but did not affect the rate of transfer. The duration, and thus estimated cost, of ICU stay was significantly less in the CPOX-monitored group. The potential for CPOX to allow for early intervention, or perhaps prevention of pulmonary complications, needs to be explored. Routine CPOX monitoring did not reduce transfer to ICU, mortality, or overall estimated cost of hospitalization, and it is unclear if there is any real benefit from the application of this technology in patients on a general care floor who are recovering from cardiothoracic surgery.
The studies confirmed that pulse oximetry can detect hypoxaemia and related events. However, we have found no evidence that pulse oximetry affects the outcome of anaesthesia for patients. The conflicting subjective and objective results of the studies, despite an intense methodical collection of data from a relatively large general surgery population, indicate that the value of perioperative monitoring with pulse oximetry is questionable in relation to improved reliable outcomes, effectiveness, and efficiency. Routine continuous pulse oximetry monitoring did not reduce either transfer to ICU or mortality, and it is unclear if there is any real benefit from the application of this technology in patients who are recovering from cardiothoracic surgery in a general care area.