Synthesizing data from several small randomized controlled trials, a new meta-analysis illustrates the importance of noninvasive monitoring of regional cerebral oxygen saturation with near-infrared spectroscopy (NIRS) for patients undergoing high-risk surgical procedures.
The researchers concluded that NIRS can help identify cerebral desaturation events, thereby reducing the incidence of postoperative cognitive dysfunction in these individuals, leading them to recommend goal-directed maintenance of cerebral oxygenation to improve patient care and quality of life.
“As we know, postoperative cognitive deficit—especially when it occurs early—is associated with adverse neurocognitive outcomes and poorer clinical outcomes,” said Vandana Vaishnav, MD, a staff anesthesiologist at St. Catharines General Hospital, in St. Catharines, Ontario. “Over the last two decades, there has been a lot of noise in the literature about near-infrared reflective spectroscopy for monitoring cerebral regional oxygenation. So we decided to amplify those signals and do a systematic review and meta-analysis of the efficacy of the technology.”
Indeed, intraoperative cerebral hypoxia has been linked to several adverse clinical outcomes, including postoperative cognitive deficit, neurologic events and prolonged hospital stay. Although small-scale randomized controlled trials have highlighted the role of early identification and reversal of intraoperative cerebral desaturation events in improving major organ morbidity and mortality (Anesth Analg 2007;104:51-58; Ann Thorac Surg 2009;87:36-44; J Cardiothorac Vasc Anesth 2013;27:1260-1266; Eur J Cardiothoracic Surg 2015;47:447-454; Anesthesiology2016;124:826-836), Dr. Vaishnav said they were underpowered and lacked methodological quality.
To help clarify this information, the investigators searched a variety of databases to identify randomized controlled trials conducted on adult patients undergoing surgery where NIRS monitoring was compared with either blinded NIRS or no NIRS monitoring. The analyzed outcomes included postoperative cognitive dysfunction, intraoperative cerebral desaturation events, postoperative stroke, postoperative ICU stay, acute renal failure requiring dialysis and 30-day mortality.
Large Effect Found
Dr. Vaishnav and her colleagues identified 20 eligible studies from the literature, of which six randomized controlled trials were included in the meta-analysis. They found a large effect estimate for postoperative cognitive dysfunction (odds ratio [OR], 0.61; 95% CI, 0.43-0.86; P=0.004) and cerebral desaturation events (OR, 0.66; 95% CI, 0.47-0.93; P=0.02) in favor of regional oxygen saturation monitoring. “So there was clearly a significant benefit in favor of the monitoring with respect to identifying intraoperative cerebral desaturation events and preventing postoperative cognitive dysfunction,” Dr. Vaishnav reported at the 2017 annual meeting of the Canadian Anesthesiologists’ Society (abstract 284883).
A subgroup analysis was also performed, indicating significant utility of regional oxygen saturation monitoring for cardiac surgery patients compared with major abdominal surgery patients for postoperative cognitive dysfunction (OR, 0.61; 95% CI, 0.43-0.86; P=0.004). “We also found statistical significance with respect to ICU stay,” she added, “with a mean difference of 0.54 days’ benefit in those patients in the monitoring group.”
To the contrary, the evidence was very low and the recommendation weak for other outcomes, such as neurologic events, acute renal failure and 30-day mortality. “We would expect that there might be more neurocognitive events in the group with no monitoring, but somehow we didn’t see any trend here,” Dr. Vaishnav explained.
Given these findings, the investigators concluded that regional oxygen saturation monitoring is a useful physiologic parameter for identifying cerebral desaturation events and reducing incidence of postoperative cognitive dysfunction in high-risk surgical patients. Nevertheless, they also recognized the need for large randomized controlled trials to upgrade the quality of evidence.
“There is clearly a beneficial role for this monitoring,” Dr. Vaishnav said. “We would recommend based on this evidence that there should be a goal-directed maintenance of cerebral oxygen saturation.”
According to Hilary P. Grocott, MD, professor of anesthesia and surgery at the University of Manitoba, in Winnipeg, and editor-in-chief of the Canadian Journal of Anesthesia, there is still more work to be done. “Although there continues to be emerging data reflecting the value of using cerebral oximetry—and the results of this meta-analysis certainly reflect this—there still remain large gaps in our understanding of how best to optimize outcomes, and which outcomes might be expected to be improved by this technology,” Dr. Grocott said. “Accordingly, there is a clear need for even larger randomized controlled trials before we more fully understand where and how to use cerebral oximetry.”