Qualitative comparison of carbon dioxide-induced change in cerebral near-infrared spectroscopy versus jugular venous oxygen saturation in adults with acute brain disease

Electrical bioimpedance measurement and near-infrared spectroscopy in pediatric postoperative neurocritical care: a prospective observational study

Background

To investigate the clinical significance of the disturbance coefficient (DC) and regional cerebral oxygen saturation (rSO₂) as obtained through the use of electrical bioimpedance and near-infrared spectroscopy (NIRS) in pediatric neurocritical care.

Participants and methods

We enrolled 45 pediatric patients as the injury group and 70 healthy children as the control group. DC was derived from impedance analysis of 0.1 mA-50 kHz current via temporal electrodes. rSO₂ was the percentage of oxyhemoglobin measured from reflected NIR light on the forehead. DC and rSO₂ were obtained at 6, 12, 24, 48 and 72 h after surgery for the injury group and during the health screening clinic visit for the control group. We compared DC and rSO₂ between the groups, their changes over time within the injury group and their correlation with intracranial pressure (ICP), cerebral perfusion pressure (CPP), Glasgow coma scale (GCS) score, Glasgow outcome scale (GOS) score, and their ability to diagnose postoperative cerebral edema and predict poor prognosis.

Results

DC and rSO₂ were significantly lower in the injury group than in the control group. In the injury group, ICP increased over the monitoring period, while DC, CPP and rSO₂ decreased. DC was negatively correlated with ICP and positively correlated with GCS score and GOS score. Additionally, lower DC values were observed in patients with signs of cerebral edema, with a DC value of 86.5 or below suggesting the presence of brain edema in patients aged 6-16 years. On the other hand, rSO₂ was positively correlated with CPP, GCS score, and GOS score, with a value of 64.4% or below indicating a poor prognosis. Decreased CPP is an independent risk factor for decreased rSO₂.

Conclusion

DC and rSO₂ monitoring based on electrical bioimpedance and near-infrared spectroscopy not only reflect the degree of brain edema and oxygenation, but also reflect the severity of the disease and predict the prognosis of the patients. This approach offers a real-time, bedside, and accurate method for assessing brain function and detecting postoperative cerebral edema and poor prognosis.

The Influence of Extracerebral Tissue on Continuous Wave Near-Infrared Spectroscopy in Adults: A Systematic Review of In Vivo Studies

Near-infrared spectroscopy (NIRS) is a non-invasive technique for measuring regional tissue haemoglobin (Hb) concentrations and oxygen saturation (rSO₂). It may be used to monitor cerebral perfusion and oxygenation in patients at risk of cerebral ischemia or hypoxia, for example, during cardiothoracic or carotid surgery. However, extracerebral tissue (mainly scalp and skull tissue) influences NIRS measurements, and the extent of this influence is not clear. Thus, before more widespread use of NIRS as an intraoperative monitoring modality is warranted, this issue needs to be better understood. We therefore conducted a systematic review of published in vivo studies of the influence of extracerebral tissue on NIRS measurements in the adult population. Studies that used reference techniques for the perfusion of the intra- and extracerebral tissues or that selectively altered the intra- or extracerebral perfusion were included. Thirty-four articles met the inclusion criteria and were of sufficient quality. In 14 articles, Hb concentrations were compared directly with measurements from reference techniques, using correlation coefficients. When the intracerebral perfusion was altered, the correlations between Hb concentrations and intracerebral reference technique measurements ranged between |r| = 0.45-0.88. When the extracerebral perfusion was altered, correlations between Hb concentrations and extracerebral reference technique measurements ranged between |r| = 0.22-0.93. In studies without selective perfusion modification, correlations of Hb with intra- and extracerebral reference technique measurements were generally lower (|r| < 0.52). Five articles studied rSO₂. There were varying correlations of rSO₂ with both intra- and extracerebral reference technique measurements (intracerebral: |r| = 0.18-0.77, extracerebral: |r| = 0.13-0.81). Regarding study quality, details on the domains, participant selection and flow and timing were often unclear. We conclude that extracerebral tissue indeed influences NIRS measurements, although the evidence (i.e., correlation) for this influence varies considerably across the assessed studies. These results are strongly affected by the study protocols and analysis techniques used. Studies employing multiple protocols and reference techniques for both intra- and extracerebral tissues are therefore needed. To quantitatively compare NIRS with intra- and extracerebral reference techniques, we recommend applying a complete regression analysis. The current uncertainty regarding the influence of extracerebral tissue remains a hurdle in the clinical implementation of NIRS for intraoperative monitoring. The protocol was pre-registered in PROSPERO (CRD42020199053).

Effect of Respiratory Physiological Changes on Optic Nerve Sheath Diameter and Cerebral Oxygen Saturation in Patients With Acute Traumatic Brain Injury

BACKGROUND

Severe traumatic brain injury (TBI) results in raised intracranial pressure (ICP). Ultrasonographic measurement of the optic nerve sheath diameter (ONSD) is a noninvasive method for the assessment of raised ICP. Manipulation of positive end-expiratory pressure (PEEP) and end-tidal carbon dioxide (ETCO2) are often used to optimize ICP and improve oxygenation in TBI patients. This study evaluated the effects of PEEP and ETCO2 on ONSD and regional cerebral oxygen saturation (rScO2) in patients with acute TBI.

METHODS

A total of 14 patients (11 males) aged older than 18 years with acute severe TBI were included in this study. ONSD and rScO2 were assessed before and after changes in PEEP from 5 to 10 cm H2O and in ETCO2 from 40 to 30 mm Hg on both pathologic and nonpathologic sides.

RESULTS

Increasing PEEP and reducing ETCO2 resulted in changes in ONSD and rScO2 on both pathologic and nonpathologic sides. On the pathologic side, ONSD and rScO2 were highest with a PEEP of 10 cm H2O:ETCO2 40 mm Hg combination and lowest with PEEP of 5 cm H2O:ETCO2 30 mm Hg (ONSD 5.24±0.49 vs. 4.27±0.36 mm, P<0.001; rScO2 70.7±9.91% vs. 66.3±9.75%, P<0.001); both PEEP and ETCO2 had significant effects on ONSD and rScO2 (P<0.001). On the nonpathologic side, ONSD and rScO2 were highest and lowest with PEEP of 10 cm H2O:ETCO2 40 mm Hg and PEEP of 5 cm H2O:ETCO2 30 mm Hg combinations, respectively (ONSD: 4.93±0.46 vs. 4.02±0.40 mm, P<0.001; rScO2: 74.77±8.30% vs. 70.69±8.12%, P<0.001). ETCO2 had a significant effect on rScO2 (P<0.001), but the impact of PEEP on rScO2 was not statistically significant (P=0.05).

CONCLUSION

Increasing PEEP resulted in significant increases in ONSD and rScO2, whereas reducing ETCO2 significantly decreased ONSD and rScO2.

Near-Infrared Spectroscopy (NIRS) in Traumatic Brain Injury (TBI)

Traumatic brain injury (TBI) occurs when a sudden trauma causes damage to the brain. TBI can result when the head suddenly and violently impacts an object or when an object pierces the skull and enters brain tissue. Secondary injuries after traumatic brain injury (TBI) can lead to impairments on cerebral oxygenation and autoregulation. Considering that secondary brain injuries often take place within the first hours after the trauma, noninvasive monitoring might be helpful in providing early information on the brain's condition. Near-infrared spectroscopy (NIRS) is an emerging noninvasive monitoring modality based on chromophore absorption of infrared light with the capability of monitoring perfusion of the brain. This review investigates the main applications of NIRS in TBI monitoring and presents a thorough revision of those applications on oxygenation and autoregulation monitoring. Databases such as PubMed, EMBASE, Web of Science, Scopus, and Cochrane library were utilized in identifying 72 publications spanning between 1977 and 2020 which were directly relevant to this review. The majority of the evidence found used NIRS for diagnosis applications, especially in oxygenation and autoregulation monitoring (59%). It was not surprising that nearly all the patients were male adults with severe trauma who were monitored mostly with continue wave NIRS or spatially resolved spectroscopy NIRS and an invasive monitoring device. In general, a high proportion of the assessed papers have concluded that NIRS could be a potential noninvasive technique for assessing TBI, despite the various methodological and technological limitations of NIRS.

Role of Multimodal Cerebral Oximetry Monitoring in the Anesthetic Management of a Patient With High-Grade Intracranial Arteriovenous Malformation: A Case Report

Near-infrared spectroscopy (NIRS) is a noninvasive monitor of regional brain tissue oxygenation, and jugular venous oximetry (SjvO2) is a monitor of global cerebral oxygenation. We report the role of intraoperative multimodal monitoring of cerebral oxygenation in the anesthetic management of a patient with grade III intracranial arteriovenous malformation (AVM) presenting for surgical excision. Real-time monitoring of cerebral oxygenation is of much relevance in high-grade AVMs where anesthetic management is focused on neuroprotection and prevention of cerebral hypoxia. Besides, it also helps in prediction, early detection, and judicious management of perioperative complications, which are commonly encountered in high-grade AVMs.

Application of optical methods in the monitoring of traumatic brain injury: A review

We present an overview of the wide range of potential applications of optical methods for monitoring traumatic brain injury. The MEDLINE database was electronically searched with the following search terms: "traumatic brain injury," "head injury," or "head trauma," and "optical methods," "NIRS," "near-infrared spectroscopy," "cerebral oxygenation," or "cerebral oximetry." Original reports concerning human subjects published from January 1980 to June 2015 in English were analyzed. Fifty-four studies met our inclusion criteria. Optical methods have been tested for detection of intracranial lesions, monitoring brain oxygenation, assessment of brain perfusion, and evaluation of cerebral autoregulation or intracellular metabolic processes in the brain. Some studies have also examined the applicability of optical methods during the recovery phase of traumatic brain injury . The limitations of currently available optical methods and promising directions of future development are described in this review. Considering the outstanding technical challenges, the limited number of patients studied, and the mixed results and opinions gathered from other reviews on this subject, we believe that optical methods must remain primarily research tools for the present. More studies are needed to gain confidence in the use of these techniques for neuromonitoring of traumatic brain injury patients.

Clinical application of near-infrared spectroscopy in patients with traumatic brain injury: a review of the progress of the field

Near-infrared spectroscopy (NIRS) is a technique by which the interaction between light in the near-infrared spectrum and matter can be quantitatively measured to provide information about the particular chromophore. Study into the clinical application of NIRS for traumatic brain injury (TBI) began in the 1990s with early reports of the ability to detect intracranial hematomas using NIRS. We highlight the advances in clinical applications of NIRS over the past two decades as they relate to TBI. We discuss recent studies evaluating NIRS techniques for intracranial hematoma detection, followed by the clinical application of NIRS in intracranial pressure and brain oxygenation measurement, and conclude with a summary of potential future uses of NIRS in TBI patient management.

Near-Infrared Spectroscopy in the Monitoring of Adult Traumatic Brain Injury: A Review

Cerebral near-infrared spectroscopy (NIRS) has long represented an exciting prospect for the noninvasive monitoring of cerebral tissue oxygenation and perfusion in the context of traumatic brain injury (TBI), although uncertainty still exists regarding the reliability of this technology specifically within this field. We have undertaken a review of the existing literature relating to the application of NIRS within TBI. We discuss current "state-of-the-art" NIRS monitoring, provide a brief background of the technology, and discuss the evidence regarding the ability of NIRS to substitute for established invasive monitoring in TBI.

Techniques to assess tissue oxygenation in the clinical setting

The microcirculation plays an essential role in health and disease. Microvascular perfusion can be assessed directly using laser Doppler flowmetry and various imaging techniques or indirectly using regional capnometry and measurement of indicators of mismatch between oxygen delivery and oxygen consumption or indices of disturbed cellular oxygen utilization. Assessment of microvascular oxygen availability implies measurement of oxygen pressure or measurement of hemoglobin oxygen saturation. Microvascular function is assessed using other methods, including venous plethysmography. In this paper, I review current knowledge concerning assessment of the microcirculation with special emphasis on methods that could be used at the bedside.

Correlation between pre-operative brain magnetic resonance angiography findings and intra-operative cerebral oxygen saturation during coronary artery bypass graft surgery

Coronary artery bypass graft (CABG) patients often have cerebrovascular disease and pre-operative brain magnetic resonance angiography (MRA) frequently reveals cerebral vasculature stenosis. This study was designed to investigate whether pre-operative MRA findings correlated with regional cerebral oxygen saturation (ScO(2)) in 120 patients undergoing on-pump or off-pump CABG. Following MRA examination, patients were divided into six groups of 20 patients each based on MRA findings (no stenosis, mild stenosis or severe stenosis) and procedure (on-pump or off-pump CABG). Mean ScO(2) values over 3 min were determined at seven periods during surgery. Patients with severe cerebrovascular stenosis showed significantly lower ScO(2) than other groups during off-pump CABG. During on-pump CABG, ScO(2) decreased significantly during cardiopulmonary bypass in all groups and was significantly lower in the severe stenosis group. Pre-operative MRA and intra-operative ScO(2) monitoring may help to identify patients at increased risk of brain damage during or following CABG.

Noninvasive monitoring of cerebral oxygenation during vasomotor reactivity tests by a new near-infrared spectroscopy device

BACKGROUND

Spatially resolved spectroscopy is a recently developed technique for noninvasive monitoring of cerebral tissue oxygenation using the photon diffusion theory.

METHODS

We studied this technique with a new, commercial near-infrared spectroscopy (NIRS) device during vasomotor reactivity tests in 28 healthy volunteers (mean age 31.0 years; SD 10.6 years) and compared it with values assessed by the modified Beer-Lambert law and indices from simultaneous transcranial Doppler sonography of both middle cerebral arteries. We measured O(2) reactivity as percentage change of cerebral blood flow velocity (CBFV), as absolute change in the concentrations (measured in micromol/l) of oxygenated (HbO(2)), deoxygenated (Hb) and total hemoglobin (HbT), and as change in the tissue oxygenation index (TOI) during inhalation of 100% oxygen. CO(2) reactivity was calculated as percentage change of CBFV (NCR), as absolute change in the concentrations of HbO(2), Hb, and HbT (micromol/l), and as change in TOI (%) per 1% increase in end-tidal CO(2).

RESULTS

One hundred percent oxygen inhalation lead to a decrease in CBFV (mean +/- SD: left -8.0 +/- 7.0%, p = 0.000; right -9.6 +/- 7.6%, p = 0.000), an increase in HbO(2) (0.99 +/- 1.07 micromol/l), Hbdiff (2.23 +/- 1.72 micromol/l), and TOI (3.1 +/- 1.5%), and a decrease in Hb (-1.22 +/- 0.74 micromol/l), significant from baseline values (p = 0.0000). CO(2) reactivity was: NCR left 25.4 +/- 14.7%; NCR right 25.9 +/- 13.4%; HbO(2) 1.99 +/- 0.97 micromol/l; Hb -1.24 +/- 0.81 micromol/l; HbT 0.81 +/- 1.0 micromol/l, and TOI 3.7 +/- 2.2%. O(2) reactivity in TCD did not correlate with NIRS reactivities (Pearson p > 0.05), but NCR did correlate with changes in HbO(2), Hb, and TOI (Pearson p < 0.01). TOI was closely related to indices derived from the Beer-Lambert law (Pearson p < 0.03), but not with mean arterial blood pressure or skin blood flow during vasomotor reactivity tests.

CONCLUSION

Spatially resolved spectroscopy provides an encouraging, noninvasive new tool to study cerebral tissue oxygenation during vasomotor reactivity tests consistent with physiological changes.

Reproducibility of the blood flow index as noninvasive, bedside estimation of cerebral blood flow

OBJECTIVE

To investigate the feasibility and reproducibility of the blood flow index (BFI) method for measuring cerebral blood flow.

DESIGN AND SETTING

Prospective functional study in pediatric intensive care.

PATIENTS AND PARTICIPANTS

14 consecutive patients with median age of 2 months (range 1 days-11 years) requiring artificial ventilation, invasive arterial blood pressure monitoring, and central venous access.

INTERVENTIONS

The first passage of an intravenous indocyanine green (ICG) bolus through the cerebral vasculature was monitored by noninvasive near-infrared spectroscopy. BFI was calculated by dividing maximal ICG absorption change by rise time. Reproducibility was evaluated by six ICG injections at 5-min intervals.

RESULTS

Of all ICG injections 6% were canceled, and 4% were eliminated due to injection failures. Median BFI of 17 reproducibility determinations was 71 (range 12-213) and median coefficient of variation (CV) of BFI was 10% (4.9-18.5). The quantity of ICG bolus did not affect the CV (0.1 vs. 0.3 mg ICG/kg). Eight reproducibility tests in patients after cardiac surgery had smaller CV than the others, and the eight in newborns had higher CV than in older children. Patient parameters such as arterial blood pressure, endtidal CO(2), and percutaneous oxygen saturation were stable and showed CV below 2% during reproducibility determination.

CONCLUSIONS

The BFI method allows rapid and repeated measurements of CBF with good feasibility and reproducibility. As a relative but not absolute measure of CBF, BFI seems to be suited for clinical evaluation of intraindividual CBF changes during determination of cerebrovascular reactivities or during therapeutic interventions.

Acute effects of cigarette smoking on cerebral oxygenation and hemodynamics: a combined study with near-infrared spectroscopy and transcranial Doppler sonography

Cigarette smoking has been shown to increase cerebral blood flow velocity (CBFV) and reduce vasomotor reactivity temporarily. The aim of our study was to clarify whether this results from dilation of resistance vessels alone with subsequent increase in regional cerebral blood flow (rCBF), or an additional constriction of basal cerebral arteries. In 24 healthy smokers (mean age+/-S.D., 32.7+/-10.5 years), cerebral oxygenation and hemodynamics were monitored by transcranial Doppler sonography and near-infrared spectroscopy before, during, and after smoking a cigarette (nicotine 0.9 mg). We simultaneously recorded CBFV of both middle cerebral arteries, mean arterial blood pressure, skin blood flow, end-tidal CO(2), changes in concentration of cerebral oxyhemoglobin, deoxyhemoglobin, and total hemoglobin (micromol/l), and a cerebral tissue oxygenation index. Smoking increased CBFV (p<0.01), oxyhemoglobin (p<0.01), and total hemoglobin (p<0.01). After smoking, the increase in CBFV and total hemoglobin persisted (p<0.01), while oxyhemoglobin returned to baseline. Deoxyhemoglobin and cerebral tissue oxygenation index did not change during the whole procedure. During, but not after smoking, CBFV increase was correlated to ipsilateral changes in oxyhemoglobin and total hemoglobin (p<0.05). The increase in oxyhemoglobin only during smoking and the lack of changes in deoxyhemoglobin and cerebral tissue oxygenation index indicate that smoking did not substantially increase rCBF. The smoking-induced elevation in CBFV might therefore be due to an additional constriction of the middle cerebral artery. The combined effects of smoking on basal cerebral arteries and arterioles might contribute to the increased stroke risk in smokers.

Dynamic cerebral autoregulatory response to blood pressure rise measured by near-infrared spectroscopy and intracranial pressure

OBJECTIVES

Noninvasive near-infrared spectroscopy (NIRS) continuously monitors changes in cerebral hemoglobin saturation (Hb(Diff) ) and content (Hb(Total)). It may allow visualization of the dynamic cerebral autoregulatory response to rapid blood pressure increases without relevant contamination of the NIRS signal from extracerebral hemoglobin.

DESIGN

Prospective cohort study.

SETTINGS

Multidisciplinary pediatric intensive care unit.

PATIENTS

Six consecutive children in coma due to severe encephalopathy (head trauma, five patients; mumps encephalitis, one patient) requiring artificial ventilation, invasive arterial blood, and intracranial pressure monitoring.

INTERVENTIONS

Frontotemporal recording of Hb(Diff) and Hb(Total) while rapidly elevating blood pressure by bolus injection of phenylephrine.

MEASUREMENTS AND RESULTS

During an increase of blood pressure of 13 +/- 1 mm Hg with a "rise time" of 16 +/- 1 secs (mean of a total of 31 injections +/- sem), a significant linear correlation was found between Hb(Diff) and intracranial pressure signals (mean coefficient, 0.46 +/- 0.04) but not between Hb(Total) and intracranial pressure. Three response patterns were observed. First, Hb(Diff) and intracranial pressure reduction, corresponding with vasoconstriction and normal dynamic autoregulation (n = 3); second, Hb(Diff) and intracranial pressure increase, corresponding with persistent vasodilation and abolished autoregulation (n = 11); and third, transient Hb(Diff) and intracranial pressure increase followed by a decrease at peak blood pressure elevation, called impaired autoregulation (n = 15). In one patient with fatal brain swelling, phenylephrine testing showed no effect on NIRS signals (n = 2). Furthermore, there were significant correlations between 31 pooled interindividual pairs of Hb(Diff) changes with intracranial pressure changes (values at baseline averaged over 60 secs subtracted from values at peak blood pressure elevation averaged over 5 secs), with a correlation coefficient of .82 (p <.001).

CONCLUSIONS

NIRS represents a new and promising technique for bedside determination of dynamic cerebral autoregulation during acutely induced blood pressure rise. The significant correlations found between NIRS signals and intracranial pressure excluded relevant extracerebral contamination of the NIRS signals. In our patients with severe encephalopathy, dynamic autoregulation was in most instances not fully preserved.

Spatially resolved spectroscopy (NIRO-300) does not agree with jugular bulb oxygen saturation in patients undergoing warm bypass surgery

PURPOSE

Near infrared spectroscopy (NIRS) is a promising non-invasive method for continuous monitoring of cerebral oxygenation during cardiac surgery with cardiopulmonary bypass (CPB). This study was designed to study the agreement between tissue oxygen index (TOI) measured by spatially resolved spectroscopy (NIRO-300) and jugular bulb oxygen saturation (SjO2) in patients undergoing warm coronary bypass surgery.

METHODS

Seventeen patients undergoing warm coronary artery bypass surgery were studied. NIRS was continuously monitored and was averaged before CPB, five, 20, 40, 60 min on CPB, five minutes before end of CPB and ten minutes after CPB to coincide with SjO2 measurements. Bypass temperature was maintained at 34-37 degrees C.

RESULTS

Bland and Altman analysis showed a bias (TOI-SjO2) of -6.7%, and wide limits of agreement (from 16% to -28%) between the two methods. In addition, mean TOI was lower than mean SjO2 during and after CPB. We observed a statistically significant correlation between arterial carbon dioxide and SjO2 measurements (r2=0.33; P=0.0003), but the former did not correlate with TOI values (r2=0.001; P=0.7).

CONCLUSION

Our results demonstrate a lack of agreement between SjO2 and TOI for monitoring cerebral oxygenation during cardiac surgery. We conclude that the two methods are not interchangeable.

Reduced vasomotor reactivity in cerebral microangiopathy : a study with near-infrared spectroscopy and transcranial Doppler sonography

BACKGROUND AND PURPOSE

Reduction of cerebral blood flow and vasomotor reactivity (VMR) are thought to play an important role in the pathogenesis of cerebral microangiopathy. The aim of our study was to determine whether near-infrared spectroscopy (NIRS) can detect a reduced VMR in patients with microangiopathy, whether NIRS reactivities correlate with VMR assessed by transcranial Doppler sonography (TCD), and whether the differing extents of patients' microangiopathy demonstrated on MRI or CT can be distinguished by both noninvasive techniques.

METHODS

We compared the VMR of 46 patients with cerebral microangiopathy with 13 age-matched control subjects. Patients were classified with the Erkinjuntti scale. We monitored cerebral blood flow velocity (CBFV) in both middle cerebral arteries by TCD, changes in concentration of oxyhemoglobin (HbO(2)), deoxyhemoglobin (Hb) and blood volume (HbT) by NIRS, mean arterial blood pressure, and end-tidal CO(2) (EtCO(2)) during normocapnia and hypercapnia. VMRs were calculated as percent change of CBFV (NCR) and as absolute change in concentration of HbO(2), Hb, and HbT per 1% increase in EtCO(2) (CR-HbO(2), CR-Hb, CR-HbT).

RESULTS

NCR and NIRS reactivities were significantly reduced in patients with cerebral microangiopathy. CR-HbO(2) and CR-Hb showed a close correlation with NCR, and NCR and NIRS reactivities were related to the severity of cerebral microangiopathy according to the Erkinjuntti scale. Validity of NCR and NIRS reactivities were similar.

CONCLUSIONS

VMR is reduced in patients with cerebral microangiopathy and can be noninvasively assessed in basal arteries (with TCD) and brain parenchyma (with NIRS). Reduction of CO(2)-induced VMR, as measured by NIRS and TCD, may indicate the severity of microangiopathy.

Effects of hypothermic and normothermic cardiopulmonary bypass on brain oxygenation

BACKGROUND

In this study, we assessed the effects of normothermia and hypothermia during cardiopulmonary bypass (CPB) both on internal jugular venous oxygen saturation (SjvO2) and the regional cerebral oxygenation state (rSO2) estimated by near infrared spectroscopy (NIRS).

METHODS

Thirty patients scheduled for elective coronary artery bypass graft surgery (CABG) were randomly divided into two groups. Group 1 (n = 15) underwent surgery for normothermic (> 35 degrees C) CPB, and group 2 (n = 15) underwent surgery for hypothermic (30 degrees C) CPB, and alpha-stat regulation was applied. A 4.0-French fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to continuously monitor the SjvO2 value. To estimate the rSO2 state, a spectrophotometer probe was attached to the mid-forehead. SjvO2 and rSO2 values were then collected simultaneously using a computer.

RESULTS

Neither the cerebral desaturation time (duration during SjvO2 value below 50%), nor the ratio of the cerebral desaturation time to the total CPB time significantly differed (normothermic group: 18+/-6 min, 15+/-6%; hypothermic group: 17+/-6 min, 13+/-6%, respectively). The rSO2 value in the normothermic group decreased during the CPB period compared with the pre-CPB period. The rSO2 value in the hypothermic group did not change throughout the perioperative period.

CONCLUSIONS

These findings suggest that near infrared spectroscopy might be sensitive enough to detect subtle changes in regional cerebral oxygenation.

A comparison of near-infrared spectroscopy and jugular bulb oximetry in comatose patients resuscitated from a cardiac arrest

One cause of cerebral damage in comatose patients resuscitated from a cardiac arrest is cerebral ischaemia occurring during the postresuscitation period. Near-infrared spectroscopy has been advocated as a useful monitor of brain oxygenation, but data on clinical use in comatose postarrest patients are not available. Therefore, we compared regional oxygen saturation measured with the INVOS 3100 with global oxygen saturation measured using jugular bulb oximetry in 10 comatose patients successfully resuscitated from an out-of-hospital cardiac arrest. Our data show that, in most patients, there is a significant difference between the two methods. The INVOS 3100 over-read at low jugular bulb saturations (< 60%) and under-read at high jugular bulb saturations (> or = 60%). During hypoventilation we found a significant increase in regional oxygen saturation. This increase was significantly correlated with the rise in cerebral blood flow and cardiac index, indicating that regional oxygen saturation is influenced by both cerebral and extracerebral components. We conclude that regional cerebral oxygen saturation measured with the INVOS 3100 cannot be compared with global cerebral oxygen saturation measured with jugular bulb oximetry in comatose patients resuscitated from a cardiac arrest. This may be due to characteristics of the INVOS 3100 or to the distribution of cerebral blood flow after cardiac arrest.

The differential effects of prostaglandin E1 and nitroglycerin on regional cerebral oxygenation in anesthetized patients

We evaluated the effects of prostaglandin E1 (PGE1) and nitroglycerin (NTG) on regional tissue oxygenation and use in the brain using near infrared spectroscopy (NIRS). Twenty-four patients who underwent elective cardiac surgery were randomly divided into two groups. The study was performed after the induction of anesthesia and before the start of the surgical procedure. After measuring arterial and jugular venous blood gases, cardiovascular hemodynamics, and relative cerebral oxyhemoglobin (HbO2), deoxyhemoglobin, and cytochrome aa3 at the baseline, PGE1 (n = 12) or NTG (n = 12) was infused intravenously at a rate of 0.3 g/kg or 5 g/kg, respectively. Thirty minutes after the start of drug infusion, administration of the drugs was stopped. Both PGE1 and NTG reduced mean arterial pressure to approximately 70% of the baseline value 10, 20, and 30 min after start of drug infusion (P < 0.05). Internal jugular venous pressure increased significantly during NTG but not during PGE1 infusion (P < 0.05). PGE1 increased HbO2 concentration, which was sustained for 30 min after discontinuing the drug. NTG increased HbO2 concentration, but this gradually returned to the baseline level after discontinuation of the drug. Baseline value of jugular oxygen saturation was 64.5% +/- 2.1%, and there was no significant changes during the infusion of PGE1 or NTG. These results demonstrate that both NTG and PGE1 increased cerebral oxygen saturation as measured by NIRS. This may be explained by local cerebral hyperemia without major alteration in flow/metabolism coupling of brain. The onset of this increase was slower and the duration of this effect after discontinuation of the drug was more prolonged with PGE1. These phenomena occurred despite the relatively similar time course of the effect of these two drugs on systemic hemodynamic values.

IMPLICATIONS

The cerebrovascular effects of vasodilators used for induced hypotension are not fully understood. In this study, we used near infrared spectrometry and jugular oxygen saturation measurement to assess the effects of prostaglandin E1 and nitroglycerin on cerebral perfusion. We found that nitroglycerin and prostaglandin E1 increase cerebral oxygen saturation as measured by near infrared spectrometry, but with different time courses. This information will hopefully help anesthesiologists to better maintain adequate regional cerebral oxygenation.

Evaluation of brain oxygenation during selective cerebral perfusion by near-infrared spectroscopy

BACKGROUND

Although selective cerebral perfusion (SCP) has been used for cerebral protection in aortic arch operations, the appropriate perfusion conditions of SCP are unclear.

METHODS

We used near-infrared spectroscopy, which evaluates brain ischemia noninvasively and continuously, to determine whether perfusion with SCP (core temperature, 20 degrees C; flow rate, 10 mL.kg-1.min-1) was acceptable in terms of oxyhemoglobin and deoxyhemoglobin in patients having SCP for aortic arch operations (SCP group, n = 6) versus patients having cardiopulmonary bypass (CPB) for coronary artery bypass grafting (CPB group, n = 6).

RESULTS

There were no significant differences in age (65 +/- 10 versus 63 +/- 12 years), CPB time (199 +/- 67 versus 199 +/- 52 minutes), changes in hematocrit (-12.9% +/- 3.7% versus -12.5% +/- 6.0%), lowest blood pressure (43 +/- 7 versus 45 +/- 10 mm Hg), or highest central venous pressure (8 +/- 2 versus 9 +/- 4 mm Hg) between the SCP and CPB groups. In the SCP group, the maximum decrease in oxyhemoglobin level and the maximum increase in deoxyhemoglobin level were -5.0 to -11.4 mumol/L and -0.1 to 3.9 mumol/L, respectively; in the CPB group, the respective changes were -3.2 to -14.2 mumol/L and -0.4 to 3.6 mumol/L. Changes of oxyhemoglobin and deoxyhemoglobin levels in the SCP group were almost within the range of those in the CPB group. There were no brain complications in either group.

CONCLUSIONS

As described here, SCP is acceptable and safe for brain protection in aortic arch procedures.

Evidence for early supply independent mitochondrial dysfunction in patients developing multiple organ failure after trauma

OBJECTIVE

To determine whether early supply independent mitochondrial oxidative dysfunction occurs in trauma patients who develop multiple organ failure (MOF).

DESIGN

Prospective focused observational trial.

METHODS

High-risk patients were aggressively resuscitated while being continuously monitored by near infrared spectroscopy. Near infrared spectroscopy monitoring strips allow for a direct comparison of changes in tissue oxyhemoglobin levels (HbO2), which reflect local oxygen supply, and cytochrome a,a3 redox, which reflects mitochondrial oxygen consumption. Under normal conditions, HbO2 and a,a3 redox are tightly coupled. On the other hand, decoupled HbO2 and a,a3 redox is a sign of mitochondrial oxidative dysfunction. Outcomes included MOF, oxygen delivery, oxygen consumption, lactate, and the presence of decoupled HbO2 and a,a3 redox.

RESULTS

Twenty-four high-risk patients were studied; nine (38%) developed MOF. At 12 hours of resuscitation, MOF and non-MOF patients did not have statistically different oxygen delivery and oxygen consumption, but lactate levels were significantly higher in MOF patients. Additionally, HBO2 and a,a3 redox were decoupled in eight (89%) MOF patients compared with two (13%) non-MOF patients (p < 0.05).

CONCLUSION

Severely injured trauma patients who develop MOF preferentially display evidence of mitochondrial oxidative dysfunction early in the course of their resuscitation despite early goal-oriented maximization of oxygen delivery.

Cerebral oxygenation monitoring by near-infrared spectroscopy is not clinically useful in patients with severe closed-head injury: a comparison with jugular venous bulb oximetry

OBJECTIVE

To compare continuous jugular venous bulb oximetry and cerebral near-infrared spectroscopy in patients with severe closed head injury.

DESIGN

A prospective observational study.

SETTING

Intensive care unit of a major teaching hospital.

PATIENTS

Adults (n = 10) with severe closed-head injury (Glasgow Coma Scale score of < or = 8).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Jugular venous bulb oximetry, cerebral near-infrared spectroscopy, and cerebral perfusion pressure were measured continuously. A total of 3,691 paired measurements of near-infrared spectroscopy and jugular venous bulb oximetry were analyzed. Poor correlation (r2 = .04) between paired measurements and wide limits of agreement (-13% to +21%) were demonstrated. The mean difference between measurements was +/- 4% and the standard deviation of the mean difference was +/- 8.69%. The data were subsequently grouped according to three clinically significant subgroups of jugular venous bulb oxygen saturation reflecting low ( < 55%), normal (55% to 75%) and high ( > 75%) saturation values. Poor correlation and wide limits of agreement between the two methods of measurement were observed in all groups. Values recorded by near-infrared spectroscopy did not significantly change between the groups, and 14 clinically significant episodes of jugular venous bulb desaturation were not detected by near-infrared spectroscopy.

CONCLUSIONS

Tissue oxygen saturation determined by near-infrared spectroscopy does not reflect significant changes in cerebral oxygenation detected by the global measurement of jugular venous bulb oximetry. This finding may be explained by inadequate signal detection and inaccuracies in the algorithm used to filter out extracranial components. Until these technical difficulties are addressed, near-infrared spectroscopy, as measured by the machine assessed in this study, cannot be routinely recommended for assessment of cerebral oxygenation in patients with acute head injury.