Cerebral oxygen desaturation monitored by intraoperative near-infrared spectroscopy and incidence of post-operative cognitive dysfunction: a systematic review

Abstract

Background Many advances have been made in the field of anesthesia to properly protect and monitor cerebral function and oxygenation during surgery; yet the incidence of cerebral injury, including postoperative cognitive dysfunction (POCD) remains high. Cerebral oxygen saturation measured by cerebral oximetry has the potential to decrease incidence of POCD and improve patient outcomes. Objectives To synthesize the evidence on whether there is a direct relationship between cerebral oxygen desaturation using intraoperative cerebral oximetry monitoring and the incidence of post-operative cognitive dysfunction. Inclusion criteria Types of participants This review considered all patients over the age of eight years old receiving general anesthesia for any surgical procedure, as patients younger than this age usually have different anesthetic emergence and transfer processes than patients older than eight years of age. Patients with pre-existing neurologic disease including stroke, alcohol abuse, history of psychiatric disorders and emergency cases were excluded, since a baseline neurologic test cannot be performed appropriately. Type of intervention This review considered studies that examine the use of near infrared spectroscopy or cerebral oximetry as a monitor for cerebral oxygen saturation and desaturation in patients receiving general anesthesia. Types of studies This review considered randomized controlled trials, cohort studies and case-control studies. Types of outcomes The review considered studies that include measurements of postoperative neurological deficit, or postoperative cognitive dysfunction related to cerebral oxygen desaturation as outcome measures. Search strategy The search strategy aimed to find both published and unpublished studies and papers. The search was limited to the English language, beginning with the first human reported cerebral oximetry studies using near-infrared spectroscopy in 1985 through 2013. The search was performed across: CINAHL, MEDLINE, [email protected], EMBASE, Elsevier Science Direct, Mednar and ProQuest. Methodological quality Studies were critically appraised by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute. Data collection Data was extracted using the standardized data extraction tools from the Joanna Briggs Institute. Data synthesis Due to the heterogeneity of the data and outcome measurements, a meta-analysis was not possible; results are presented in a narrative summary. Results Ten studies were included in the review: Two randomized controlled trials (RCT) and eight cohort studies. In eight of the studies, monitoring of cerebral oxygen saturation by cerebral oximetry was supported. Two of the studies supporting this intervention were RCTs. Three of the studies conclude that cerebral oxygen desaturation increases length of hospital stay. Conclusions Based on the included literature, maintenance of cerebral oxygen saturation monitored by cerebral oximetry has the potential to reduce incidence of POCD. Avoidance of cerebral oxygen desaturation is also associated with a reduction in postoperative complications, including decreased length of hospital stay and faster recovery. Implications for practice The use of cerebral oximetry as an adjunct monitor during general anesthesia can help the anesthesia provider reduce incidence of postoperative cognitive dysfunction. This impacts practice and patients in that reduction of cognitive decline has the potential to aid patients to recover faster, allowing them to resume activities of daily living quicker and face a potentially shorter hospital stay. Implications for research The literature for this topic consists mainly of prospective observational cohort studies. Further randomized controlled trials are needed to determine if a higher threshold for minimal cerebral oxygen levels may decrease incidence of POCD. There is still some controversy regarding this monitoring device and incidence of cognitive decline, since there is no set safe threshold allowing deviation from baseline values. Further research is also needed to determine if prevention of cerebral oxygen desaturation has any implications in overall hospital costs.