Various techniques have been employed for the early detection of perioperative cerebral
ischaemia and hypoxia. Cerebral near‐infrared spectroscopy (NIRS) is increasingly
used in this clinical scenario to monitor brain oxygenation. However, it is unknown
whether perioperative cerebral NIRS monitoring and the subsequent treatment strategies
are of benefit to patients. To assess the effects of perioperative cerebral NIRS monitoring
and corresponding treatment strategies in adults and children, compared with blinded
or no cerebral oxygenation monitoring, or cerebral oxygenation monitoring based on
non‐NIRS technologies, on the detection of cerebral oxygen desaturation events (CDEs),
neurological outcomes, non‐neurological outcomes and socioeconomic impact (including
cost of hospitalization and length of hospital stay). We searched the Cochrane Central
Register of Controlled Trials (CENTRAL 2016, Issue 12), Embase (1974 to 20 December
2016) and MEDLINE (PubMed) (1975 to 20 December 2016). We also searched the World
Health Organization (WHO) International Clinical Trials Registry Platform for ongoing
studies on 20 December 2016. We updated this search in November 2017, but these results
have not yet been incorporated in the review. We imposed no language restriction.
We included all relevant randomized controlled trials (RCTs) dealing with the use
of cerebral NIRS in the perioperative setting (during the operation and within 72
hours after the operation), including the operating room, the postanaesthesia care
unit and the intensive care unit. Two authors independently selected studies, assessed
risk of bias and extracted data. For binary outcomes, we calculated the risk ratio
(RR) and its 95% confidence interval (CI). For continuous data, we estimated the mean
difference (MD) between groups and its 95% CI. As we expected clinical and methodological
heterogeneity between studies, we employed a random‐effects model for analyses and
we examined the data for heterogeneity (I 2 statistic). We created a 'Summary of
findings' table using GRADEpro. We included 15 studies in the review, comprising a
total of 1822 adult participants. There are 12 studies awaiting classification, and
eight ongoing studies. None of the 15 included studies considered the paediatric population.
Four studies were conducted in the abdominal and orthopaedic surgery setting (lumbar
spine, or knee and hip replacement), one study in the carotid endarterectomy setting,
and the remaining 10 studies in the aortic or cardiac surgery setting. The main sources
of bias in the included studies related to potential conflict of interest from industry
sponsorship, unclear blinding status or missing participant data. Two studies with
312 participants considered postoperative neurological injury, however no pooled effect
estimate could be calculated due to discordant direction of effect between studies
(low‐quality evidence). One study (N = 126) in participants undergoing major abdominal
surgery reported that 4/66 participants experienced neurological injury with blinded
monitoring versus 0/56 in the active monitoring group. A second study (N = 195) in
participants having coronary artery bypass surgery reported that 1/96 participants
experienced neurological injury in the blinded monitoring group compared with 4/94
participants in the active monitoring group. We are uncertain whether active cerebral
NIRS monitoring has an important effect on the risk of postoperative stroke because
of the low number of events and wide confidence interval (RR 0.25, 95% CI 0.03 to
2.20; 2 studies, 240 participants; low‐quality evidence). We are uncertain whether
active cerebral NIRS monitoring has an important effect on postoperative delirium
because of the wide confidence interval (RR 0.63, 95% CI 0.27 to 1.45; 1 study, 190
participants; low‐quality evidence). Two studies with 126 participants showed that
active cerebral NIRS monitoring may reduce the incidence of mild postoperative cognitive
dysfunction (POCD) as defined by the original studies at one week after surgery (RR
0.53, 95% CI 0.30 to 0.95, I 2 = 49%, low‐quality evidence). Based on six studies
with 962 participants, there was moderate‐quality evidence that active cerebral oxygenation
monitoring probably does not decrease the occurrence of POCD (decline in cognitive
function) at one week after surgery (RR 0.62, 95% CI 0.37 to 1.04, I 2 = 80%). The
different type of monitoring equipment in one study could potentially be the cause
of the heterogeneity. We are uncertain whether active cerebral NIRS monitoring has
an important effect on intraoperative mortality or postoperative mortality because
of the low number of events and wide confidence interval (RR 0.63, 95% CI 0.08 to
5.03, I 2 = 0%; 3 studies, 390 participants; low‐quality evidence). There was no evidence
to determine whether routine use of NIRS‐based cerebral oxygenation monitoring causes
adverse effects. The effects of perioperative active cerebral NIRS monitoring of brain
oxygenation in adults for reducing the occurrence of short‐term, mild POCD are uncertain
due to the low quality of the evidence. There is uncertainty as to whether active
cerebral NIRS monitoring has an important effect on postoperative stroke, delirium
or death because of the low number of events and wide confidence intervals. The conclusions
of this review may change when the eight ongoing studies are published and the 12
studies awaiting assessment are classified. More RCTs performed in the paediatric
population and high‐risk patients undergoing non‐cardiac surgery (e.g. neurosurgery,
carotid endarterectomy and other surgery) are needed. The review question We assessed
the effects of monitoring the brain with cerebral near‐infrared spectroscopy (NIRS),
and treatments based on it, during and after surgery in adults and children. We aimed
to determine whether NIRS detects reduced oxygen supply to the brain, which would
allow the use of interventions to improve nervous system, mental process (cognition)
and other outcomes that can have an impact on patients' hospital length of stay and
costs. Background The human brain needs a lot of oxygen (has a high oxygen consumption)
and is very sensitive to reduced oxygen supply. Successful treatment for low levels
of oxygen in the brain during or after surgery relies on early diagnosis of a lack
of oxygen. Cerebral NIRS is increasingly used for the early detection of lack of oxygen
to the brain. It uses near‐infrared light (700 to 1000 nanometres) to penetrate through
the superficial layers of the head, including the scalp and the skull, to show the
cerebral tissue. Study characteristics The evidence is current to December 2016. We
updated our search in November 2017, but these results have not yet been incorporated
in the review. We included 15 completed randomized controlled trials involving 1822
participants. There are 8 ongoing studies and 12 waiting further assessment. None
of the completed studies included infants or children. In four studies participants
were undergoing abdominal or orthopaedic surgery, one study included participants
undergoing a procedure to restore proper blood flow to the brain, and in the remaining
10 studies participants were undergoing large blood vessel or heart surgery with or
without heart bypass. The studies all used cerebral NIRS in the operating room, with
only two also using cerebral NIRS in the intensive care unit. The control groups were
monitored using methods such as heart rate and mean arterial blood pressure, electroencephalogram,
transcranial doppler, bispectral index, oxygen saturation in the jugular vein, evoked
potentials or cerebral tissue oxygen partial pressure. Overall, the different studies
varied in their approach to the review question. Key results We did not pool (combine)
the data for the outcome postoperative neurological injury because of variations between
studies. One study with 126 participants having major abdominal surgery reported that
4/66 versus 0/56 participants experienced neurological injury with blinded and active
monitoring, respectively. A second study with 195 participants undergoing coronary
artery bypass surgery reported that 1/96 versus 4/94 participants suffered neurological
injury in the blinded (masked) and active (with active treatments) monitoring groups,
respectively. We are unsure whether active NIRS monitoring has an important effect
on the risk of postoperative stroke and delirium because there was a low number of
events and the result was not precise (2 studies, 240 participants; 1 study, 190 participants,
respectively; low‐quality evidence). Based on two studies with 126 participants, we
found low‐quality evidence that cerebral NIRS monitoring may reduce the number of
participants with mild cognitive impairment at one week after surgery. Based on six
studies with 962 participants, we found moderate‐quality evidence that monitoring
with cerebral NIRS probably leads to little or no decrease in the number of participants
with a decline in cognitive function one week after surgery. We are uncertain whether
active cerebral oxygenation monitoring has a crucial effect on intraoperative or postoperative
deaths because there was a low number of events and the result was not precise (3
studies, 390 participants; low‐quality evidence). We did not find any detrimental
effects of the routine use of NIRS‐based brain oxygenation monitoring. Quality of
the evidence Overall, it is uncertain whether active NIRS monitoring has a crucial
effect on postoperative stroke, delirium or death because of the imprecision of the
results (low‐quality evidence). Therefore, the effects of active cerebral NIRS monitoring
on postoperative nervous system injury, delirium, decline in cognitive function and
death are uncertain. For some outcomes, such as postoperative stroke or other neurological
injury, the evidence was based on few studies with limited numbers of participants.
Reporting of outcomes was often incomplete for all study participants, as was reporting
of the study design, such as blinding. Some studies had potential conflicts of interest
from industry sponsorship.