Oxygen is carried around the body attached to haemoglobin in the blood. By passing light through the skin, pulse oximeters monitor how much oxygen the blood is carrying. Hypoxaemia—when the level of oxygen in the blood falls below optimal levels—is a risk during surgery when patient breathing and ventilation may be affected by anaesthesia or other drugs. Medical staff often monitor patients during and after surgery using pulse oximetry, but it is not clear whether this practise reduces the risk of adverse events after surgery. We reviewed the evidence on the effect of pulse oximeters on outcomes of surgical patients. In this update of the review, the search is current to June 2013. We identified five studies in which a total of 22,992 participants had been allocated at random to be monitored or not monitored with a pulse oximeter. These studies were not similar enough for their results to be combined statistically. Study results showed that although pulse oximetry can detect a deficiency of oxygen in the blood, its use does not affect a person's cognitive function and does not reduce the risk of complications or of dying after anaesthesia. These studies were large enough to show a reduction in complications, and care was taken to ensure that outcomes were assessed in the same way in both groups. The studies were conducted in developed countries, where standards of anaesthesia and nursing care are high. It is possible that pulse oximetry may have a greater impact on outcomes in other geographical areas with less comprehensive provision of health care.
These studies confirmed that pulse oximetry can detect hypoxaemia and related events. However, we found no evidence that pulse oximetry affects the outcome of anaesthesia for patients. The conflicting subjective and objective study results, 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 transfer to the ICU and did not decrease mortality, and it is unclear whether any real benefit was derived from the application of this technology for patients recovering from cardiothoracic surgery in a general care area.
This is an update of a review last published in Issue 9, 2009, of The Cochrane Library. Pulse oximetry is used extensively in the perioperative period and might improve patient outcomes by enabling early diagnosis and, consequently, correction of perioperative events that might cause postoperative complications or even death. Only a few randomized clinical trials of pulse oximetry during anaesthesia and in the recovery room have been performed that describe perioperative hypoxaemic events, postoperative cardiopulmonary complications and cognitive dysfunction.
To study the use of perioperative monitoring with pulse oximetry to clearly identify adverse outcomes that might be prevented or improved by its use.
The following hypotheses were tested.
1. Use of pulse oximetry is associated with improvement in the detection and treatment of hypoxaemia.
2. Early detection and treatment of hypoxaemia reduce morbidity and mortality in the perioperative period.
3. Use of pulse oximetry per se reduces morbidity and mortality in the perioperative period.
4. Use of pulse oximetry reduces unplanned respiratory admissions to the intensive care unit (ICU), decreases the length of ICU readmission or both.
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 5), MEDLINE (1966 to June 2013), EMBASE (1980 to June 2013), CINAHL (1982 to June 2013), ISI Web of Science (1956 to June 2013), LILACS (1982 to June 2013) and databases of ongoing trials; we also checked the reference lists of trials and review articles. The original search was performed in January 2005, and a previous update was performed in May 2009.
We included all controlled trials that randomly assigned participants to pulse oximetry or no pulse oximetry during the perioperative period.
Two review authors independently assessed data in relation to events detectable by pulse oximetry, any serious complications that occurred during anaesthesia or in the postoperative period and intraoperative or postoperative mortality.
The last update of the review identified five eligible studies. The updated search found one study that is awaiting assessment but no additional eligible studies. We considered studies with data from a total of 22,992 participants that were eligible for analysis. These studies gave insufficient detail on the methods used for randomization and allocation concealment. It was impossible for study personnel to be blinded to participant allocation in the study, as they needed to be able to respond to oximetry readings. Appropriate steps were taken to minimize detection bias for hypoxaemia and complication outcomes. Results indicated that hypoxaemia was reduced in the pulse oximetry group, both in the operating theatre and in the recovery room. During observation in the recovery room, the incidence of hypoxaemia in the pulse oximetry group was 1.5 to three times less. Postoperative cognitive function was independent of perioperative monitoring with pulse oximetry. A single study in general surgery showed that postoperative complications occurred in 10% of participants in the oximetry group and in 9.4% of those in the control group. No statistically significant differences in cardiovascular, respiratory, neurological or infectious complications were detected in the two groups. The duration of hospital stay was a median of five days in both groups, and equal numbers of in-hospital deaths were reported in the two groups. Continuous pulse oximetry has the potential to increase vigilance and decrease pulmonary complications after cardiothoracic surgery; however, routine continuous monitoring did not reduce transfer to an ICU and did not decrease overall mortality.