Correlation of brain tissue oxygen tension with cerebral near-infrared spectroscopy and mixed venous oxygen saturation during extracorporeal membrane oxygenation

Understanding Near-Infrared Spectroscopy: An Update

Near-infrared spectroscopy (NIRS) is a novel technology that uses infrared light to noninvasively and continuously measure regional oxygen extraction in real time at the bedside. Neonatal research using this device supports its use as an adjunct to routine cardiovascular monitoring because NIRS serves as a surrogate marker for end-organ perfusion and can detect minute changes in cerebral, intestinal, and kidney tissue beds. Multiple conditions affecting premature infants are frequently associated with hypoperfusion; therefore, methods to detect early tissue-specific perfusion alterations may substantially improve the clinician's ability to intervene and prevent further deterioration.

Discussion: can upper extremity (deltoid) near infrared spectroscopy be used to assess cerebral tissue bed saturation on femorally cannulated veno-arterial extracorporeal membrane oxygenation patients?

Continuous cerebral tissue saturation monitoring with near infrared spectroscopy may help clinicians identify cerebral desaturation early; however, patients have reported discomfort from near infrared spectroscopy monitoring pads on the forehead. This study aims to compare upper extremity near infrared spectroscopy monitoring to cerebral near infrared spectroscopy monitoring to assess its viability as a surrogate for cerebral saturation. A retrospective analysis of 10 femorally cannulated veno-arterial extracorporeal membrane oxygenation patients was performed comparing left (L) and right (R) upper extremity (deltoid) near infrared spectroscopy monitoring to cerebral near infrared spectroscopy monitoring (n = 20 data sets, 10 left and 10 right) and right radial blood gasses. Deltoid and cerebral near infrared spectroscopy values were recorded every 15 minutes for at least 24 hours when possible, were plotted on scatter grams, and were analyzed using Pearson product-moment coefficient (r). Based on the concept of covariance, a moderate-good relationship r = 0.50-0.75 was noted in 10% (n = 2) of the study group. A fair relationship r = 0.25-0.50 was noted in 50% (n = 10), and little or no relationship was noted in 40% (n = 8). None of the study group displayed a good to excellent relationship (r = 0.75 or above). In addition, coefficient of multiple determination for multiple regression R² was calculated and strong fit of the regression line was not noted. Although cerebral near infrared spectroscopy monitoring has been extremely helpful in identifying low cerebral tissue saturation on veno-arterial extracorporeal membrane oxygenation patients, the use of upper extremity (peripheral deltoid) tissue monitoring does not provide adequate correlation and should not be used as a surrogate to cerebral monitoring.

Perioperative near-infrared spectroscopy cerebral oxygen saturation in symptomatic pediatric hydrocephalus patients at risk for intracranial hypertension

OBJECTIVE

The lack of a continuous, noninvasive modality for monitoring intracranial pressure (ICP) is a major obstacle in the care of pediatric patients with hydrocephalus who are at risk for intracranial hypertension. Intracranial hypertension can lead to cerebral ischemia and brain tissue hypoxia. In this study, the authors evaluated the use of near-infrared spectroscopy (NIRS) to measure regional cerebral oxygen saturation (rSO2) in symptomatic pediatric patients with hydrocephalus concerning for elevated ICP.

METHODS

The authors evaluated the NIRS rSO2 trends in pediatric patients presenting with acute hydrocephalus and clinical symptoms of intracranial hypertension. NIRS rSO2 values were recorded hourly before and after neurosurgical intervention. To test for significance between preoperative and postoperative values, the authors constructed a linear regression model with the rSO2 values as the outcome and pre- and postsurgery cohorts as the independent variable, adjusted for age and sex, and used the generalized estimating equation method to account for within-subject correlation.

RESULTS

Twenty-two pediatric patients underwent NIRS rSO2 monitoring before and after CSF diversion surgery. The mean durations of NIRS rSO2 recording pre- and postoperatively were 13.95 and 26.82 hours, respectively. The mean pre- and postoperative rSO2 values were 73.84% and 80.65%, respectively, and the adjusted mean difference estimated from the regression model was 5.98% (adjusted p < 0.0001), suggestive of improved cerebral oxygenation after definitive neurosurgical CSF diversion treatment. Postoperatively, all patients returned to baseline neurological status with no clinical symptoms of elevated ICP.

CONCLUSIONS

Cerebral oxygenation trends measured by NIRS in symptomatic pediatric hydrocephalus patients with intracranial hypertension generally improve after CSF diversion surgery.

Cerebral Oxygenation of Premature Lambs Supported by an Artificial Placenta

An artificial placenta (AP) using venovenous extracorporeal life support (VV-ECLS) could represent a paradigm shift in the treatment of extremely premature infants. However, AP support could potentially alter cerebral oxygen delivery. We assessed cerebral perfusion in fetal lambs on AP support using near-infrared spectroscopy (NIRS) and carotid arterial flow (CAF). Fourteen premature lambs at estimated gestational age (EGA) 130 days (term = 145) underwent cannulation of the right jugular vein and umbilical vein with initiation of VV-ECLS. An ultrasonic flow probe was placed around the right carotid artery (CA), and a NIRS sensor was placed on the scalp. Lambs were not ventilated. CAF, percentage of regional oxygen saturation (rSO2) as measured by NIRS, hemodynamic data, and blood gases were collected at baseline (native placental support) and regularly during AP support. Fetal lambs were maintained on AP support for a mean of 55 ± 27 hours. Baseline rSO2 on native placental support was 40% ± 3%, compared with a mean rSO2 during AP support of 50% ± 11% (p = 0.027). Baseline CAF was 27.4 ± 5.4 ml/kg/min compared with an average CAF of 23.7 ± 7.7 ml/kg/min during AP support. Cerebral fractional tissue oxygen extraction (FTOE) correlated negatively with CAF (r = -0.382; p < 0.001) and mean arterial pressure (r = -0.425; p < 0.001). FTOE weakly correlated with systemic O2 saturation (r = 0.091; p = 0.017). Cerebral oxygenation and blood flow in premature lambs are maintained during support with an AP. Cerebral O2 extraction is inversely related to carotid flow and is weakly correlated with systemic O2 saturation.

Effects of moderate and severe arterial hypotension on intracerebral perfusion and brain tissue oxygenation in piglets

BACKGROUND

Hypotension is common in anaesthetised children, and its impact on cerebral oxygenation is unknown. The goal of the present study was to investigate the effects of moderate systemic arterial hypotension (mHT) and severe hypotension (sHT) on cerebral perfusion and brain tissue oxygenation in piglets.

METHODS

Twenty-seven anaesthetised piglets were randomly allocated to a control group, mHT group, or sHT group. Cerebral monitoring comprised a tissue oxygen partial pressure ( [Formula: see text] ) and laser Doppler (LD) perfusion probe advanced into the brain tissue, and a near-infrared spectroscopy sensor placed over the skin measuring regional oxygen saturation (rSO₂). Arterial hypotension was induced by blood withdrawal and i.v. nitroprusside infusion [target MAP: 35-38 (mHT) and 27-30 (sHT) mm Hg]. Data were analysed at baseline, and every 20 min during and after treatment.

RESULTS

Compared with control, [Formula: see text] decreased equally with mHT and sHT [mean (SD) after 60 min: control: 17.1 (6.4); mHT: 6.4 (3.6); sHT: 7.2 (4.3) mm Hg]. No differences between groups were detected for rSO₂ and LD during treatment. However, in the sHT group, rSO₂ increased after restoring normotension [from 49.3 (9.5) to 58.9 (8.9)% Post60]. sHT was associated with an increase in blood lactate [from 1.5 (0.4) to 2.4 (0.9) mmol L^-1], and a decrease in bicarbonate [28 (2.4) to 25.8 (2.6) mmol L^-1] and base excess [4.7 (1.9) to 2.0 (2.7) mmol L^-1] between baseline and 60 min after the start of the experiment.

CONCLUSIONS

Induction of mHT and sHT by hypovolaemia and nitroprusside infusion caused alterations in brain tissue oxygenation in a piglet model, but without detectable changes in brain tissue perfusion and regional oxygen saturation.

Cerebral and Limb Tissue Oxygenation During Peripheral Venoarterial Extracorporeal Life Support

Femoral access in extracorporeal life support (ECLS) has been associated with regional variations in arterial oxygen saturation, potentially predisposing the patient to ischemic tissue damage. Current monitoring techniques, however, are limited to intermittent bedside evaluation of capillary refill among other factors. The aim of this study was to assess whether cerebral and limb regional tissue oxygen saturation (rSO₂) values reflect changes in various patient-related parameters during venoarterial ECLS (VA-ECLS). This retrospective observational study included adults assisted by femorofemoral VA-ECLS. Bifrontal cerebral and bilateral limb tissue oximetry was performed for the entire duration of support. Hemodynamic data were analyzed parallel to cerebral and limb rSO₂. A total of 23 patients were included with a median ECLS duration of 5 [1-20] days. Cardiac arrhythmias were observed in 12 patients, which was associated with a decreased mean rSO₂ from 61%±11% to 51%±10% during atrial fibrillation and 67%±9% to 58%±10% during ventricular fibrillation (P<0.001 for both). A presumably sudden increase in cardiac output due to myocardial recovery (n=8) resulted in a significant decrease in mean cerebral rSO₂ from 73%±7% to 54%±6% and from 69%±9% to 53%±8% for the left and right cerebral hemisphere, respectively (P=0.012 for both hemispheres). Also, right radial artery partial gas pressure for oxygen decreased from 15.6±2.8 to 8.3±1.9 kPa (P=0.028). No differences were found in cerebral desaturation episodes between patients with and without neurologic complications. In six patients, limb rSO₂ increased from on average 29.3±2.7 to 64.0±5.1 following insertion of a distal cannula in the femoral artery (P=0.027). Likewise, restoration of flow in a clotted distal cannula inserted in the femoral artery was necessary in four cases and resulted in increased limb rSO₂ from 31.3±0.8 to 79.5±9.0; P=0.068. Non-invasive tissue oximetry adequately reflects events influencing cerebral and limb perfusion and can aid in monitoring tissue perfusion in patients assisted by ECLS.

The SafeBoosC phase II clinical trial: an analysis of the interventions related with the oximeter readings

BACKGROUND

The SafeBoosC phase II randomised clinical trial recently demonstrated the benefits of a combination of cerebral regional tissue oxygen saturation (rStO2) by near-infrared spectroscopy (NIRS) and a treatment guideline to reduce the oxygen imbalance in extremely preterm infants.

AIMS

To analyse rStO2-alarm-related clinical decisions and their heterogeneity in the NIRS experimental group (NIRS monitoring visible) and their impact on rStO2 and SpO2.

METHODS

Continuous data from NIRS devices and the alarms (area under the curve of the rStO2 out of range had accumulated 0.2%h during 10 min), clinical data at discrete time points and interventions prompted by the alarms were recorded.

RESULTS

Sixty-seven infants had data that fulfilled the requirements for this analysis. 1107 alarm episodes were analysed. The alarm triggered a treatment guideline intervention in 25% of the cases; the type of intervention chosen varied among clinical sites. More than 55% of alarms were not followed by an intervention ('No action'); additionally, in 5% of alarms the rStO2 value apparently was considered non-reliable and the sensor was repositioned. The percentage of unresolved alarms at 30 min after 'No action' almost doubled the treatment guideline intervention (p<0.001). Changes in peripheral oxygen saturation (SpO2), were observed only after treatment guideline interventions.

CONCLUSIONS

This study shows that 25% of rStO2 alarms were followed by a clinical intervention determined by the treatment guideline. However, the rStO2 and SpO2 returned to normal ranges after the intervention, supporting the notion that decisions taken by the clinicians were appropriate.

TRIAL REGISTRATION NUMBER

ClinicalTrial.gov NCT01590316.

RBC transfusion in pediatric patients supported with extracorporeal membrane oxygenation: is there an impact on tissue oxygenation?

OBJECTIVE

To examine first the RBC transfusion practice in pediatric patients supported with extracorporeal membrane oxygenation and second the relationship between transfusion of RBCs and changes in mixed venous saturation (SvO2) and cerebral regional tissue oxygenation, as measured by near-infrared spectroscopy in patients supported with extracorporeal membrane oxygenation.

DESIGN

Retrospective observational study.

SETTING

Pediatric, cardiovascular, and neonatal ICUs of a tertiary care children's hospital.

PATIENTS

All pediatric patients supported with extracorporeal membrane oxygenation between January 1, 2010, and December 31, 2010.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 45 patients supported with extracorporeal membrane oxygenation. The median (interquartile range) phlebotomy during extracorporeal membrane oxygenation was 75 mL/kg (33, 149 mL/kg). A total of 617 transfusions were administered (median, 9 per patient; range = 1-57). RBC volumes transfused during extracorporeal membrane oxygenation support were 254 mL/kg (136, 557) and 267 mL/kg (187, 393; p = 0.82) for cardiac and noncardiac patients, respectively. Subtracting the volume of RBCs used for extracorporeal membrane oxygenation circuit priming, median RBC transfusion volumes were 131 and 80 mL/kg for cardiac and noncardiac patients, respectively (p = 0.26). The cardiac surgical patients received the most RBCs (529 vs 74 mL/kg for nonsurgical cardiac patients). The median hematocrit maintained during extracorporeal membrane oxygenation support was 37%, with no difference between cardiac and noncardiac patients. Patients supported with extracorporeal membrane oxygenation were exposed to a median of 10.9 (range, 3-43) individual donor RBC units. Most transfusions resulted in no significant change in either SvO2 or cerebral near-infrared spectroscopy. Only 5% of transfusions administered (31/617) resulted in an increase in SvO2 of more than 5%, whereas an increase in cerebral near-infrared spectroscopy of more than 5 was only observed in 9% of transfusions (53/617). Most transfusions (73%) were administered at a time when the pretransfusion SvO2 was more than 70%.

CONCLUSIONS

Patients supported with extracorporeal membrane oxygenation were exposed to large RBC transfusion volumes for treatment of mild anemia resulting from blood loss, particularly phlebotomy. In the majority of events, RBC transfusion did not significantly alter global tissue oxygenation, as assessed by changes in SvO2 and cerebral near-infrared spectroscopy. Most transfusions were administered at a time at which the patient did not appear to be oxygen delivery dependent according to global measures of tissue oxygenation.

Transcranial regional cerebral oxygen desaturation predicts delayed cerebral ischaemia and poor outcomes after subarachnoid haemorrhage: a correlational study

OBJECTIVES

To examine the relationship between regional cerebral oxygen saturation (rSO2), delayed cerebral ischaemia (DCI), and outcomes after aneurysmal subarachnoid haemorrhage (aSAH).

RESEARCH METHODOLOGY

Subjects (n = 163) with aSAH, age 21-75 years, and Fisher grade >1 were included in the study. Continuous rSO2 monitoring was performed for 5-10 days after injury using near-infrared spectroscopy with sensors over the frontal/temporal cortex. rSO2<50 indicated desaturation. DCI was defined as neurological deterioration due to impaired cerebral blood flow. Three- and 12-month functional outcomes were assessed by the modified Rankin scale (MRS) as good (0-3) and poor (4-6).

RESULTS

DCI occurred in 57% of patients; of these 66% had rSO2<50. Overall, 56% had rSO2<50 on either side, 21% and 16% had poor MRS at 3 and 12 months. Subjects with rSO2 <50 were 3.25 times more likely to have DCI compared to those with rSO2 >50 (OR 3.25, 95%CI 1.58-6.69), positive predictive value (PPV) = 70%. Subjects with rSO2 <50 were 2.7 times more likely to have poor 3-month MRS compared to those with rSO2 >50 (OR 2.7, 95%CI 1.1-7.2), PPV = 70%.

CONCLUSIONS

These results suggest that NIRS has the potential for detecting DCI after aSAH. This potential needs to be further explored in a larger prospective study.

Detection of cerebral arterial gas embolism using regional cerebral oxygen saturation, quantitative electroencephalography, and brain oxygen tension in the swine

BACKGROUND

Cerebral air emboli occur as a complication of invasive medical procedures. The sensitivity of cerebral monitoring methods for the detection of air emboli is not known. This study investigates the utility of electroencephalography and non-invasively measured cerebral oxygen saturation in the detection of intracerebrovascular air.

NEW METHOD

In 12 pigs oxygen saturation was continuously measured using transcranial near-infrared spectroscopy and oxygen tension was continuously measured using intraparenchymal probes. Additionally, quantitative electroencephalography and microdialysis were performed. Doses of 0.2, 0.4, 0.8, and 1.6 ml of air were injected into the cerebral arterial vasculature through a catheter.

RESULTS

Oxygen saturation and electroencephalography both reacted almost instantaneously on the air emboli, but were less sensitive than the intraparenchymal oxygen tension. There was reasonable correlation (ρ ranging from 0.417 to 0.898) between oxygen saturation, oxygen tension, electroencephalography and microdialysis values.

COMPARISON WITH EXISTING METHODS

Our study is the first to demonstrate the effects of cerebral air emboli using multimodal monitoring, specifically on oxygen saturation as measured using near-infrared spectroscopy.

CONCLUSIONS

Our results show that non-invasively measured oxygen saturation and quantitative electroencephalography can detect the local effects of air emboli on cerebral oxygenation, but with reduced sensitivity as compared to intraparenchymal oxygen tension. Prospective human studies using multimodal monitoring incorporating electroencephalography and oxygen saturation should be performed.

Additive effects of non-invasive ventilation to hyperoxia on cerebral oxygenation in COPD patients with exercise-related O2 desaturation

BACKGROUND

It is currently unknown whether potential haemodynamic improvements induced by non-invasive ventilation (NIV) would positively impact upon cerebral oxygenation (COx) in patients with moderate-to-severe chronic obstructive pulmonary disease (COPD).

OBJECTIVE

To investigate the effects of NIV on exercise COx in COPD patients presenting with exercise-related O(2) desaturation.

METHODS

On a double-blind trial, 13 males (FEV1 = 48·8 ± 15·1% predicted) were randomly assigned to NIV (16 cmH(2)O IPS and 5 cmH(2)O PEEP) plus HOx (FiO(2) = 0·4) or sham NIV (7 cmH(2)O IPS and 5 cmH(2)O PEEP to overcome breathing circuit resistance) plus HOx during ramp-incremental exercise performed on different days. Near-infrared spectroscopy and impedance cardiography assessed changes (Δ) in COx and cardiac output (Q(T)), respectively.

RESULTS

There were no significant between-intervention differences in peak work rate, ventilation and reported symptoms (P>0·05). Peripheral oxyhaemoglobin saturation remained above 98% throughout the tests. NIV + HOx was associated with larger increases in Δ COx, Δ Q(T) and Δ stroke volume at maximal and submaximal exercise (P<0·05). Increases in the area under the curve (to an iso-work rate) of Δ COx under NIV + HOx were significantly (P<0·01) correlated with improvements in Δ Q(T) (r = 0·82) and Δ stroke volume (r = 0·87). There was, however, no significant correlation between enhancement in these physiological responses with changes in peak work rate with NIV + HOx (P>0·05).

CONCLUSIONS

NIV added benefit to HOx in improving central haemodynamics and COx in O(2) 'desaturators' with COPD. The clinical relevance of such beneficial effects on exercise tolerance, however, remains to be demonstrated.

Effects of oxygen supplementation on cerebral oxygenation during exercise in chronic obstructive pulmonary disease patients not entitled to long-term oxygen therapy

BACKGROUND

The rate of change (Δ) in cerebral oxygenation (COx) during exercise is influenced by blood flow and arterial O(2) content (CaO(2)). It is currently unclear whether ΔCOx would (i) be impaired during exercise in patients with chronic obstructive pulmonary disease (COPD) who do not fulfil the current criteria for long-term O(2) therapy but present with exercise-induced hypoxaemia and (ii) improve with hyperoxia (FIO(2) = 0·4) in this specific sub-population.

METHODS

A total of 20 non-hypercapnic men (FEV(1) = 47·2 ± 11·5% pred) underwent incremental cycle ergometer exercise tests under normoxia and hyperoxia with ΔCOx (fold-changes from unloaded exercise in O(2)Hb) being determined by near-infrared spectroscopy. Pulse oximetry assessed oxyhaemoglobin saturation (SpO(2)), and impedance cardiography estimated changes in cardiac output (ΔQT).

RESULTS

Peak work rate and ΔCOx in normoxia were lower in eight O(2) 'desaturators' compared with 12 'non-desaturators' (P < 0·05). Area under ΔCOx during sub-maximal exercise was closely related to SpO(2) decrements in 'desaturators' (r = 0·92, P < 0·01). These patients showed the largest improvement in peak exercise capacity with hyperoxia (P < 0·05). Despite a trend to lower sub-maximal ΔQT and mean arterial pressure with active intervention, ΔCOx was significantly improved only in this group (0·57 ± 0·20 versus 2·09 ± 0·42 for 'non-desaturators' and 'desaturators', respectively; P < 0·05).

CONCLUSIONS

ΔCOx was impaired in non-hypoxaemic patients with COPD who desaturated during exercise. Hyperoxic breathing was able to correct for these abnormalities, an effect related to enhanced CaO(2) rather than improved central haemodynamics. This indicates that O(2) supplementation ameliorates exercise COx in patients with COPD who are not currently entitled to ambulatory O(2) therapy.

Near-infrared spectroscopy: a methodology-focused review

Near infrared spectroscopy (NIRS) is a light-based technology used to monitor tissue oxygen status. Refinements to the method since it was first described have extended its applicability to different research and clinical settings due to its non-invasiveness, instrument portability and ease of use. Classic NIRS recordings, based in the Beer-Lambert law, can be used for the trend monitoring of changes in tissue perfusion-oxygenation parting from an arbitrary zero point. However, in order to derive intermittently quantitative values in absolute terms, certain manoeuvres must be performed. More recently, the evolution of the technique has led to the development of instruments that provide an absolute value of regional hemoglobin saturation in a continuous manner. This review will focus on the physical principles of tissue spectroscopy including a brief description of the different operating principles that are currently in use or under development. The theoretical details, experimental procedures and data analysis involved in the measurements of physiological variables using NIRS will be described. The future beyond the scope of NIRS and potential lines of research will also be discussed.

Cerebral NIRS as a marker of superior vena cava oxygen saturation in neonates with congenital heart disease

OBJECTIVES

To investigate the correlation between cerebral near-infrared spectroscopy (NIRS) (rSO2c) and superior vena cava venous oxygen saturation (ScvO2) in newborn patients with congenital heart disease (CHD).

BACKGROUND

NIRS is a noninvasive method to monitor hemoglobin oxygen saturation using nonpulsatile oximetry.

METHODS

We retrospectively analyzed perioperative data from 100 newborn patients who underwent cardiac surgery for CHD. rSO2c, ScvO2 from 24 h before to 72 h after surgery were recorded.

RESULTS

rSO2c had a fair correlation with ScvO2 (r 0.37; P <0.001). The relationship between rSO2c and ScvO2 did not change when analyzed between patients with cyanotic or acyanotic CHD. During the preoperative period, rSO2c levels overestimated ScvO2; in the first 18 postoperative hours, rSO2c underestimated ScvO2; after that period, they showed very close trends. Hypocapnia caused rSO2c to underestimate ScvO2; in normocapnic patients, rSO2c-ScvO2 average differences were close to zero; in hypercapnic neonates, rSO2c tended to overestimate ScvO2. The best performance of rSO2c as a surrogate of ScvO2 was found in the venous saturation ranges from 40% to 60% (r 0.3, P: 0.03).

CONCLUSIONS

rSO2c in newborn patients with cyanotic and acyanotic CHD provides a continuous noninvasive information with a fair correlation with ScvO2%: some predictable variables (i.e., time from surgery, carbon dioxide, and venous saturation levels), should guide the operators to adjust rSO2c values in terms of ScvO2. Serial measures of ScvO2 seem recommended to tailor rSO2c information on actual venous saturation percentage.