Comparison of different near-infrared spectroscopic cerebral oxygenation indices with central venous and jugular venous oxygenation saturation in children

BACKGROUND: We compared two different near-infrared spectrophotometers: cerebral tissue oxygenation index (TOI) measured by NIRO 200 and regional cerebral oxygenation index (rSO(2)) measured by INVOS 5100 with venous oxygen saturation in the jugular bulb (SjO(2)) and central SvO(2) from the superior caval vein (SVC) during elective cardiac catheterization in children. METHODS: A prospective observational clinical study in 31 children with congenital heart defects in a catheterization laboratory was undertaken. TOI was compared with SjO(2) in the left jugular bulb and with SvO(2). rSO(2) was compared with SjO(2) from the right jugular bulb and SvO(2). Linear regression analysis and Pearson's correlation coefficient were calculated and Bland-Altman analyses were performed. RESULTS: Cerebral TOI and SjO(2) were significantly correlated (r = 0.56, P < 0.0001), as well as TOI and SvO(2) with r = 0.74 (P < 0.0001). Bland-Altman plots showed a mean bias of -4.3% with limits of agreement of 15.7% and -24.3% for TOI and SjO(2) and a mean bias of -4.9% with limits of agreement of 10.3% and -20.1% for TOI and SvO(2). Cerebral rSO(2) and SjO(2) showed a significant correlation (r = 0.83, P < 0.0001) and rSO(2) and SvO(2) showed excellent correlation with r = 0.93 (P < 0.0001). Bland-Altman plots showed a mean bias of -5.2% with limits of agreement of between 8.4% and -18.8% for rSO(2) and SjO(2) and a mean bias of 5.6% with limits of agreement of 13.4% and -2.2% for rSO(2) and SvO(2). CONCLUSIONS: Both near-infrared spectroscopy devices demonstrate a significant correlation with SjO(2) and SvO(2) values; nevertheless both devices demonstrate a substantial bias of the measurements to both SjO(2) and SvO(2).     

Tissue oxygenation monitoring during major pediatric surgery using transcutaneous liver near infrared spectroscopy

BACKGROUND: The aim of the study was to compare liver tissue oxygenation determined by near infrared spectroscopy (NIRS) with central venous oxygen saturation (SvO(2)) and intestinal perfusion as measured by gastric intramucosal pH (pHi) in pediatric surgical patients. METHODS: Twenty children undergoing craniofacial surgery with expected major intraoperative blood loss were studied. NIRS tissue oxygenation index (TOI(Liver)) and pHi values were recorded. Arterial blood gas analysis and SvO(2) were assessed from periodically taken blood samples. Data are presented as ranges (median) and were compared using linear regression analysis. Sensitivity and specificity of the intra-individual changes in TOI(Liver) to predict falling SvO(2) or pHi values were calculated. RESULTS: Patients age ranged from 0.79 to 8.27 years (1.92 years). TOI(Liver) ranged from 41.5 to 77.4% (61.5%), gastric pHi from 7.13 to 7.60 (7.37) and SvO(2) from 51 to 86% (74%). Among patients only moderate correlation was found between TOI(Liver) and SvO(2) (r = 0.594, P < 0.0001) and gastric pH(i) (r = 0.502, P < 0.0001). Intra-individual measured TOI(Liver) values, however, demonstrated close correlation with SvO(2) values (r = 0.680 to 0.976) but a varying correlation with gastric pHi values (r = 0.055 to 0.972). Sensitivity/specificity of TOI(Liver) to predict decreasing SvO(2) or gastric pHi values were 76.4/73.4% and 67.4/62.7% respectively. CONCLUSIONS: TOI(Liver) provided a better trend monitor of central venous oxygen saturation than gastric intramucosal pH. Because of its limited sensitivity and specificity to indicate deterioration of SvO(2), liver tissue oxygenation measured by transcutaneous NIRS does not provide additional practical information for clinical management.     

A comparison of the INVOS 4100 and the NIRO 300 near-infrared spectrophotometers

We determined whether two different devices for measuring near-infrared spectroscopy (NIRS)---the INVOS 4100 and the NIRO 300---produce similar cerebral oxygenation data during the CO(2) challenge test. Nineteen patients anesthetized with sevoflurane, 67% nitrous oxide in oxygen, and fentanyl were studied. A series of measurements of regional cerebral oxygen saturation (rSO(2)), measured by the INVOS 4100, and tissue oxygen index (TOI), measured by the NIRO 300, were performed in the following conditions: 1) normocapnia (PaCO(2), 35--45 mm Hg); 2) hypocapnia (PaCO(2), 25--35 mm Hg); 3) normocapnia; and 4) hypercapnia (PaCO(2), 45--55 mm Hg). Hemodynamic variables, including arterial blood gases and cerebral blood flow velocity, were measured at the same time with transcranial Doppler. The values and percentage changes of rSO(2) and TOI were compared by using regression analysis and Bland and Altman analysis. The rSO(2) showed a significant positive correlation with TOI (r = 0.58, P < 0.01). The percentage change of rSO(2) also showed a significant positive correlation with the percentage change of TOI during the CO(2) challenge (r = 0.85, P < 0.01). Bland and Altman analysis revealed a bias of -0.5% with 2 SD of 15.6% when comparing the rSO(2) value with the TOI value, and it showed a bias of -3.4% with 2 SD of 15.2% when comparing the percentage change of rSO(2) with the percentage change of TOI, indicating unacceptable disagreement of these data. These results indicate that cerebral oxygen saturation and its relative change during the CO(2) challenge may vary depending on the type of NIRS used. Because the measurement technique and algorithm were different in each device, we should carefully consider the clinical application of the values produced by NIRS. IMPLICATIONS: Near-infrared spectroscopy (NIRS) has been proposed as a noninvasive clinical method for assessing cerebral oxygenation. The acceptable reliability and validity of NIRS values have not been established despite their widespread use. The INVOS 4100 and the NIRO 300 can display cerebral oxygen saturation as regional cerebral oxygen saturation and tissue oxygenation index, but they produce differing results.     

Cerebral near-infrared spectroscopy in adult patients after cardiac surgery is not useful for monitoring absolute values but may reflect trends in venous oxygenation under clinical conditions

OBJECTIVE: Cerebral near-infrared spectroscopy (NIRS) was evaluated for use in monitoring global oxygenation in adult patients after cardiac surgery. DESIGN: Prospective, randomized clinical monitoring study. SETTING: Intensive care unit for cardiac surgery; university hospital. PARTICIPANTS: The study included 35 patients scheduled for cardiac surgery with insertion of a pulmonary artery catheter; patients with known cerebral-vascular perfusion disturbances were excluded. INTERVENTIONS: Noninvasive cerebral NIRS oxygen saturation (rSO(2)) and conventional intensive care monitoring parameters were assessed. MEASUREMENTS AND MAIN RESULTS: Simple regression analysis was used to assess the correlation of rSO(2) to hemodynamic parameters. There was fair-to-moderate intersubject correlation to hemoglobin concentration (r = 0.45, p < 0.0001) and mixed venous oxygen saturation (SmvO(2)) (r = 0.33, p < 0.0001). Sensitivity and specificity of rSO(2) to detect substantial (>or=1 standard deviation) changes in mixed venous oxygen saturation were 94% and 81%, respectively. CONCLUSIONS: Cerebral NIRS in adult patients might not be the tool to replace mixed venous oxygen monitoring. Further work has to be done to assess its potential to reflect intraindividual trends.     

A noninvasive estimation of mixed venous oxygen saturation using near-infrared spectroscopy by cerebral oximetry in pediatric cardiac surgery patients

BACKGROUND: Near-infrared spectroscopy (NIRS) is a noninvasive optical monitor of regional cerebral oxygen saturation (rSO2). The aim of this study was to validate the use of NIRS by cerebral oximetry in estimating invasively measured mixed venous oxygen saturation (SvO2) in pediatric postoperative cardiac surgery patients. METHODS: Twenty patients were enrolled following cardiac surgery with intraoperative placement of a pulmonary artery (PA) or superior vena cava (SVC) catheter. Five patients underwent complete biventricular repair--complete atrioventricular canal (n=3) and other (n=2). Fifteen patients with functional single ventricle underwent palliative procedures--bidirectional Glenn (n=11) and Fontan (n=4). Cerebral rSO2 was monitored via NIRS (INVOS 5100) during cardiac surgery and 6 h postoperatively. SvO2 was measured from blood samples obtained via an indwelling PA or SVC catheter and simultaneously correlated with rSO2 by NIRS at five time periods: in the operating room after weaning from cardiopulmonary bypass, after sternal closure, and in the CICU at 2, 4, and 6 h after admission. RESULTS: Each patient had five measurements (total=100 comparisons). SvO2 obtained via an indwelling PA or SVC catheter for all patients correlated with rSO2 obtained via NIRS: Pearson's correlation coefficient of 0.67 (P<0.0001) and linear regression of r2=0.45 (P<0.0001). Separate linear regression of the complete biventricular repairs demonstrated an r=0.71, r2=0.50 (P<0.0001). Bland-Altman analysis showed a bias of +3.3% with a precision of 16.6% for rSO2 as a predictor of SvO2 for all patients. Cerebral rSO2 was a more accurate predictor of SvO2 in the biventricular repair patients (bias -0.3, precision 11.8%), compared with the bidirectional Glenn and Fontan patients. CONCLUSIONS: Regional cerebral oximetry via NIRS correlates with SvO2 obtained via invasive monitoring. However, the wide limits of agreement suggest that it may not be possible to predict absolute values of SvO2 for any given patient based solely on the noninvasive measurement of rSO2. Near-infrared spectroscopy, using the INVOS 5100 cerebral oximeter, could potentially be used to indicate trends in SVO2, but more studies needs to be performed under varying clinical conditions.     

Comparison of two commercially available near-infrared spectroscopy instruments for cerebral oximetry. Technical note

Two near-infrared spectroscopy (NIRS) devices were compared with regard to their responses to changes in cerebral hemoglobin oxygenation induced by hypoxia and hypercapnia in five healthy volunteers. Sensors belonging to each NIRS device were placed on opposite sides of the volunteer's forehead. The INVOS-3100A device, approved by the United States Food and Drug Administration, records the percentage of oxyhemoglobin (HbO2) saturation and the investigational NIRO500 device records absolute changes in HbO2, deoxyhemoglobin, and total hemoglobin in micromolar concentrations referenced to an arbitrary baseline. The volunteers breathed separate mixtures of 7% CO2 in O2 and 10% O2 for 5 minutes in random order. Arterial blood pressure, end-tidal CO2 (ETCO2), arterial O2 saturation, and electrocardiographic data were continuously monitored. Hypercapnia increased (p < 0.01) ETCO2 from 42+/-2 to 56+/-3 mm Hg (mean +/- standard deviation), resulting in a 7.3+/-0.2% increase (p < 0.005) in cerebral HbO2 saturation detected by the INVOS3100A device and an 11.6+/-3 microM increase (p < 0.0008) in HbO2 detected by the NIRO500. Hypoxia decreased (p < 0.01) arterial HbO2 saturation from 98+/-1 to 87+/-3%, causing a 5.1+/-1.2% decrease (p < 0.01) in the percentage of HbO2 saturation detected by the INVOS3100A device and a 9.7+/-6.3 microM decrease in HbO2 detected by the NIRO500. The responses of the NIRO500 and the INVOS3100A instruments to changes in cerebral oxygenation resulting from hypercapnia and hypoxia were generally similar; however, responses tended to be greater when recorded by the NIRO500 device, perhaps because, unlike the INVOS3100A device, the NIRO500 does not correct for skin and bone contamination.     

Transcutaneously measured near-infrared spectroscopic liver tissue oxygenation does not correlate with hepatic venous oxygenation in children

PURPOSE: To compare transcutaneous near-infrared spectroscopic (NIRS) measured liver tissue oxygenation with hepatic vein oxygen saturation (SvhO2) in children undergoing cardiac catheterization. METHODS: A NIRS optode (containing an emitter and a receiver of near-infrared light) was placed directly below the right costal arch above the palpable liver in 40 children aged 0.02 to 7.28 yr (median: 1.8 yr). Spatially resolved spectroscopic measured tissue oxygenation index (TOI) was recorded using the NIRO-300. Paired blood samples from the hepatic vein were taken under radiological control for determination of SvhO2 in a co-oxymeter. TOI values were compared with hepatic vein oxygenation, with simultaneously obtained arterial oxygen saturation (SaO2), inferior vena cava SO2 and hemoglobin concentration using simple linear and multi-regression analysis. RESULTS: TOI values ranged from 35% to 73% (58.6 +/- 8.4%); SvhO2 from 32% to 80% (58.4 +/- 14.4%), and arterial SO2 from 54% to 100% (90.0 +/- 11.4%). TOI and hepatic vein oxygen saturation failed to correlate (r = 0.052/P = 0.752). A regression model containing arterial saturation (Delta R2 = 0.177) and the ratio of pulmonary to systemic resistance (Delta R2 = 0.095) explained 27.3% of the observed variance in TOI. In this model, hepatic vein oxygen saturation was no longer significant; explaining only 3.4% of the variance. No other variable retained a significant association. CONCLUSION: Transcutaneously measured NIRS tissue oxygenation with an optode placed over the palpable liver does not correlate with SvhO2. The value is dominated by non-hepatic variables such as arterial saturation and vascular resistances.     

Continuous monitoring of mixed venous oxygen saturation during orthotopic liver transplantation.

Hemodynamic management is an important issue concerning anesthesia for orthotopic liver transplantation (OLT). Mixed venous oxygen saturation (SvO2) is considered a good index of tissue oxygenation, but controversy exists about the usefulness of monitoring this parameter in different types of surgery. Therefore, a prospective study was performed to determine changes in SvO2 during OLT and to study the correlation between SvO2 and hemodynamic measurements. Thirty patients undergoing transplantation for end-stage liver disease were divided into two groups: group 1 (n = 15, aged 42 +/- 11 years [mean +/- SD]) without venovenous bypass (VVB), and group 2 (n = 15, aged 43 +/- 10 years) with VVB. SvO2 was greater than 74% throughout the procedure and remained stable during dissection and the anhepatic phase. There was a significant increase in SvO2 after unclamping the portal vein in group 1, whereas a significant decrease was observed during the first hour following reperfusion in group 2. There was no correlation among SvO2 and oxygen consumption, arterial oxygen saturation, (SaO2), or hemoglobin concentrations. A statistically significant correlation was found between SvO2 and cardiac index in both groups (group 1: r = 0.58, P = 0.01; group 2: r = 0.51, P = 0.01), but the correlation was relatively poor. Continuous monitoring of SvO2 may be useful, but cannot substitute for intermittent determinations of other hemodynamic or oxygenation parameters.     

Near-infrared spectroscopy reflects changes in mesenteric and systemic perfusion during abdominal compartment syndrome

BACKGROUND: Continuous and minimally invasive near-infrared spectroscopy (NIRS)-derived gastric tissue oxygen saturation (GStO(2)) and muscle tissue oxygen saturation (MStO(2)) were evaluated in a clinically relevant porcine model of hemorrhagic shock and abdominal compartment syndrome (ACS). METHODS: Phenobarbital-anesthetized swine underwent pulmonary artery catheter insertion for mixed venous oxygen saturation (SvO(2)) measurement and midline laparotomy to permit placement of a gastric NIRS probe, a jejunal (regional carbon dioxide [PrCO(2)]) tonometer, superior mesenteric artery (SMA) flow probe, and a portal vein oxygen saturation (SpvO(2)) catheter. A muscle NIRS probe was placed on the front limb. After randomization, Group 1 underwent hemorrhage and resuscitation. Group 2 had no hemorrhage or resuscitation. ACS was induced by peritoneal fluid infusion in both groups. A significant decrease in SMA flow, SpvO(2), GStO(2), SvO(2), and MStO(2) was observed after hemorrhage in Group 1 and with abdominal hypertension in both groups. RESULTS: GStO(2) significantly correlated with SMA flow (Group 1: r(2) = 0.90; Group 2: r(2) = 0.83) and mesenteric oxygen delivery (mesenteric oxygen delivery, Group 1: r(2) = 0.73; Group 2: r(2) = 0.89). MStO(2) significantly correlated with SvO(2) (Group 1: r(2) = 0.99; Group 2: r(2) = 0.65) and systemic oxygen delivery (SDO2, Group 1: r(2) = 0.60; Group 2: r(2) = 0.88). Tonometer-derived PrCO(2) values did not change at any time point in either group. CONCLUSIONS: NIRS measurement of GStO(2) and MStO(2) reflected changes in mesenteric and systemic perfusion respectively during hemorrhage and ACS.     

Changes in tissue oxygenation of the porcine liver measured by near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) is a novel method for the measurement of tissue oxygenation and may have a role in monitoring liver oxygenation and viability. The aim of this study is to validate the application of NIRS for monitoring hepatic tissue oxygenation. Large Landrace pigs (n = 12) underwent laparotomy and liver exposure. Total hepatic blood flow (THBF) was measured by the Transonic Medical Flowmeter system. NIRS probes were placed on the liver surface to continuously record changes in hepatic tissue oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), and the reduction-oxidation state of cytochrome oxidase (Cyt Ox). Reduction of hepatic tissue oxygenation was achieved by hepatic vascular inflow occlusion (n = 6) or reduction of inspired oxygen (FIO2; n = 6). The THBF changes correlated significantly with hepatic HbO2 (r = 0.84; P <.001) and Cyt Ox (r = 0.88; P <.001). With reduction of FIO2, a significant correlation was found between arterial oxygen saturation and hepatic HbO2 and Hb (r = 0.99 and r = -0.99, respectively; P <.0001). NIRS measurement of liver parenchymal oxygenation correlates well with changes in liver blood flow and arterial oxygenation.     

Assessment of cerebral oxygen balance during deep hypothermic circulatory arrest by continuous jugular bulb venous saturation and near-infrared spectroscopy

OBJECTIVE: The purpose of this study was to compare jugular venous bulb saturation (SjvO(2)) and regional cerebral oximetry (rSO(2)) by near-infrared spectroscopy (NIRS) during procedures with deep hypothermic circulatory arrest (DHCA). DESIGN: Prospective observational study. SETTING: Academic hospital. PARTICIPANTS: Patients undergoing aortic reconstructive surgery with DHCA from July 2001 to January 2005. INTERVENTION: The authors examined cerebral oxygenation by continuous NIRS monitoring and by blood gas analysis of intermittently sampled jugular bulb blood (SjvO(2)). Data were obtained during various stages of the procedure in 29 patients. NIRS measurements were compared with SjvO(2). MEASUREMENTS AND MAIN RESULTS: NIRS and SjvO(2) trends were similar. Overall, cerebral venous oxygen saturation obtained from NIRS was lower compared with SjvO(2) (p < 0.05), especially during periods of low temperature. The mean correlation between NIRS and SjvO(2) was 0.363, and the individual correlations varied from -0.11 to 0.91. The low mean correlation was because of a high degree of variability in the NIRS data between patients. CONCLUSION: It was concluded that NIRS does not closely correlate with SjvO(2) in this patient population. Cerebral oximetry measured by NIRS could not replace jugular bulb saturation as an intraoperative marker of adequate metabolic suppression.     

Noninvasive muscle oxygenation to guide fluid resuscitation after traumatic shock

BACKGROUND: Three different protocols tested the hypothesis that hind limb muscle tissue O(2) saturation (StO(2)), measured noninvasively with near-infrared spectroscopy (NIRS), is as reliable as invasive systemic oxygenation indices to guide fluid resuscitation. METHODS: In series 1, swine (n=30) were hemorrhaged, then received either no fluid, a fixed volume of colloid (15 mL/kg), or shed blood plus lactated Ringer's (LR) titrated to MAP >60 mm Hg. In series 2, swine (n=16) received a penetrating femur injury, a 47% to 55% hemorrhage to determine a median lethal dose (LD(50)) then shed blood plus LR titrated to MAP >60 mm Hg. In series 3, swine (n=5) received the femur injury plus LD(50) hemorrhage, and were resuscitated with LR titrated to StO(2) >50%. RESULTS: In series 1, StO(2) tracked mixed venous O(2) saturation (SvO(2)), but discriminated between 3 survivor groups better than SvO(2), arterial lactate, or arterial base excess. In series 2, StO(2) tracked SvO(2) but discriminated between 2 survivor groups better than SvO(2), arterial lactate, or arterial base excess. In series 3, animals survived to extubation when resuscitated to an StO(2) target. CONCLUSIONS: Noninvasive muscle StO(2) determined by NIRS was more reliable than invasive oxygenation variables as an index of shock. Because muscle StO(2) can be easily monitored in emergency situations, it may represent an improved method to gauge the severity of shock or the adequacy of fluid resuscitation after trauma.     

Balloon pump-induced pulsatile perfusion during cardiopulmonary bypass does not improve brain oxygenation.

BACKGROUND: Whether pulsatile flow offers substantial advantages for brain protection during cardiopulmonary bypass is controversial. The purpose of this study is to determine whether differences exist between pulsatile and nonpulsatile bypass concerning the effects on internal jugular venous saturation and on the state of regional cerebral oxygenation during normothermia. METHODS: Twenty-two patients undergoing elective coronary artery bypass grafting were randomly divided into 2 groups: group 1 (n = 11) received nonpulsatile perfusion during cardiopulmonary bypass and group 2 (n = 11) received pulsatile perfusion during bypass. We used an intra-aortic balloon pump to generate pulsatility. A spectrophotometric probe (INVOS 3100R, Somanetics, Troy, Mich) was used to assess the state of regional cerebral oxygenation. A 4F fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to monitor jugular venous oxygen saturation. Hemodynamic variables, arterial and jugular venous blood gases, and regional cerebral oxygenation were measured at 7 times points. RESULTS: In both groups, jugular venous oxygen saturation decreased at the early stage of the cardiopulmonary bypass (P =.03). Five patients in group 1 and 6 in group 2 had a jugular venous oxygen saturation of less than 50%. In both groups, the regional cerebral oxygenation value decreased during cardiopulmonary bypass (P =.04). CONCLUSIONS: The present results showed that pulsatility generated through the use of intra-aortic balloon pumping did not produce any beneficial effects on jugular venous oxygen saturation and regional cerebral oxygenation at normothermia.     

Venous saturation and the anaerobic threshold in neonates after the Norwood procedure for hypoplastic left heart syndrome

BACKGROUND: Reduction in oxygen delivery can lead to organ dysfunction and death by cellular hypoxia, detectable by progressive (mixed) venous oxyhemoglobin desaturation until extraction is limited at the anaerobic threshold. We sought to determine the critical level of venous oxygen saturation to maintain aerobic metabolism in neonates after the Norwood procedure (NP) for the hypoplastic left heart syndrome (HLHS). METHODS: A prospective perioperative database was maintained for demographic, hemodynamic, and laboratory data. Invasive arterial and atrial pressures, arterial saturation, oximetric superior vena cava (SVC) saturation, and end-tidal CO2 were continuously recorded and logged hourly for the first 48 postoperative hours. Arterial and venous blood gases and cooximetry were obtained at clinically appropriate intervals. SVC saturation was used as an approximation of mixed venous saturation (SvO2). A standard base excess (BE) less than -4 mEq/L (BElo), or a change exceeding -2 mEq/L/h (deltaBElo), were used as indicators of anaerobic metabolism. The relationship between SvO2 and BE was tested by analysis of variance and covariance for repeated measures; the binomial risk of BElo or deltaBElo at SvO2 strata was tested by the likelihood ratio test and logistic regression, with cutoff at p < 0.05. RESULTS: Complete data were available in 48 of 51 consecutive patients undergoing NP yielding 2,074 valid separate determinations. BE was strongly related to SvO2 (model R2 = 0.40, p < 0.0001) with minimal change after adjustment for physiologic covariates. The risk of anaerobic metabolism was 4.8% overall, but rose to 29% when SvO2 was 30% or below (p < 0.0001). Survival was 100% at 1 week and 94% at hospital discharge. CONCLUSIONS: Analysis of acid-base changes revealed an apparent anaerobic threshold when SvO2 fell below 30%. Clinical management to maintain SvO2 above this threshold yielded low mortality.     

Cerebral ischemia caused by obstructed superior vena cava cannula is detected by near-infrared spectroscopy

OBJECTIVE: Bicaval venous cannulation is being used with increasing frequency in neonates and infants to avoid circulatory arrest. However, superior vena cava (SVC) cannula obstruction may result in cerebral ischemia with no change in blood pressure or mixed venous O2 saturation. The authors hypothesized that near-infrared spectroscopy (NIRS) would allow noninvasive detection of SVC cannula obstruction. METHODS: Fifteen Yorkshire piglets (9.07 +/- 0.20 kg) underwent total cardiopulmonary bypass (CPB) (100 mL/kg/min, pH-stat strategy, hematocrit of 20%) with ascending aortic and bicaval cannulations. Femoral arterial and SVC pressure were monitored as well as mixed venous O2 saturation. NIRS monitoring of tissue oxygenation index (TOI) as well as oxyhemoglobin and deoxyhemoglobin (HHb) was undertaken. Animals were cooled to an esophageal temperature of 25 degrees C over 20 minutes. CPB flow was reduced to 50 mL/kg/min for 20 minutes. Animals then underwent a 60-minute study period of continuous CPB at 50 mL/kg/min with manipulation of the SVC cannula: group 1, open; group 2, partial occlusion; and group 3, complete occlusion. Animals were rewarmed to 37 degrees C at full flow with the SVC cannula open. Cerebral blood flow was assessed at onset of CPB, at end of cooling, at end of low flow, at end of SVC manipulation period, and at end of rewarming using radioactive microspheres. RESULTS: CBF decreased to 27.9 +/- 1.5 mL/min/100 g with complete occlusion (p < 0.01 v group 1: 39.7 +/- 1.9, group 2, 38.3 +/- 2.0 mL/min/100 g) with no change in arterial pressure or mixed venous saturation. There were also significant differences in cerebral oxygen delivery between group 3 and other groups (p < 0.01). SVC pressure increased to 19.5 +/- 4.5 and 32.5 +/- 3.1mmHg with partial and complete occlusion. NIRS indicated significant cerebral ischemia with a decrease in TOI (p < 0.05; group 3 v group 1 and 2) and an increase in HHb (p < 0.05; group 3 v group 1). At the end of the study, significant acidosis was found in group 3 compared with group 1 (p < 0.05). CONCLUSION: SVC cannula obstruction causes cerebral ischemia with no change in blood pressure or venous oxygen saturation. In view of the difficulties and risks of CVP monitoring in babies, it is recommended to use other monitoring modalities such as NIRS to assess adequacy of cerebral perfusion if bicaval cannulation is used in neonates and infants.     

Splanchnic perfusion evaluation during hemorrhage and resuscitation with gastric near-infrared spectroscopy

OBJECTIVE: The purpose of this study was to use a prototype side-illuminating near-infrared spectroscopy (NIRS) nasogastric probe to continuously measure changes in gastric tissue oxygen saturation (Sto2) in a pig hemorrhage model. METHODS: Swine (n = 12; 6 per group) underwent laparotomy and placement of a gastric NIRS probe, jejunal tonometer, superior mesenteric artery (SMA) flow probe, and a portal vein catheter. Animals underwent hemorrhage (28 mL/kg) t = 0 to 20 minutes (where t = time). Pigs in group I were resuscitated (t = 20-40 minutes) with lactated Ringer's solution (84 mL/kg), whereas group II had no resuscitation. RESULTS: A significant decrease in mean arterial pressure and SMA flow was observed after hemorrhage. SMA flow significantly correlated in group I with both NIRS Sto2 (r = 0.58, p = 0.0001) and regional CO2 (r = -0.54, p = 0.0001). In group II, superior mesenteric flow correlated with NIRS Sto2 (r = 0.30, p = 0.03), but not regional CO2 (r = -0.23, p = 0.09). CONCLUSION: Direct measurement of tissue oxygen saturation with a prototype side-illuminating near-infrared spectroscopy gastric probe appeared to rapidly reflect changes in splanchnic perfusion.     

A comparison of the Invos 3100 and the Critikon 2020 near-infrared spectrophotometers as monitors of cerebral oxygenation

Assessment of cerebral oxygenation using near-infrared spectroscopy in intensive care is increasing. We compared the ability of the Invos 3100 and the Critikon 2020 monitors to produce stable and consistent readings of regional cerebral oxygen saturation in resting volunteers. Failure to obtain any stable reading with the Critikon occurred in eight out of 18 subjects (44.4%) and with the Invos in three out of 15 subjects (20%). The Critikon showed a significantly higher failure rate in male subjects (p = 0.0011). Differences in recorded values of cerebral oxygen saturation (Critikon − Invos) ranged from −4.7% to 12.6% and were significantly related to the average saturation level (p < 0.0001). The within-monitor variability was significantly higher for the Invos (p = 0.0124). Neither monitor is able to give stable and consistent readings over time, particularly in male subjects. The unacceptably high failure rate of the recently introduced Critikon 2020 will limit or prevent its clinical use.     

A comparison of cerebral oxygenation as measured by the NIRO 300 and the INVOS 5100 Near-Infrared Spectrophotometers

In this study cerebral oxygenation was measured using the NIRO 300 and the INVOS 5100 spectrophotometers in 10 healthy adult volunteers, exposed to varying degrees of hyperoxia and hypoxia. The results showed similar baseline values for tissue oxygenation index and regional cerebral oxygen saturation with mean (SD) values being 64.9% (5.1) and 62.3% (6.0), respectively. The overall bias was -2.1%, with the INVOS 5100 under-reading cerebral oxygenation compared to the NIRO 300, with limits of agreement of +/-14.7%. Both monitors demonstrated similar changes in response to hyperoxia and hypocapnia (coefficient of variance for FIo2 0.45 = 10.0%, FIo2 1.0 = 10.1%, hypocapnia = 14.5%). The reasons for the bias and variability may relate to differences in the methodological approaches of the two monitors. The correlation between the monitors in response to changes in cerebral oxygenation implies that they may be useful as trend monitors in clinical practice.     

Arterial and Venous Contributions to Near-infrared Cerebral Oximetry

Background: Cerebral oximetry is a noninvasive bedside technology using near-infrared light to monitor cerebral oxygen saturation (Sco2) in an uncertain mixture of arteries, capillaries, and veins. The present study used frequency domain near-infrared spectroscopy to determine the ratio of arterial and venous blood monitored by cerebral oximetry during normoxia, hypoxia, and hypocapnia.

Methods: Twenty anesthetized children aged < 8 yr with congenital heart disease of varying arterial oxygen saturation (Sao2) were studied during cardiac catheterization. Sco2, Sao2, and jugular bulb oxygen saturation (Sjo2) were measured by frequency domain near-infrared spectroscopy and blood oximetry at normocapnia room air, normocapnia 100% inspired O2, and hypocapnia room air.

Results: Among subject conditions, Sao2 ranged from 68% to 100%, Sjo2 from 27% to 96%, and Sco2 from 29% to 92%. Sco2 was significantly related to Sao2 (y = 0.85 x -17, r = 0.47), Sjo2 (y = 0.77 x +13, r = 0.70), and the combination (Sco2 = 0.46 Sao2 + 0.56 Sjo2 - 17, R = 0.71). The arterial and venous contribution to cerebral oximetry was 16 +/- 21% and 84 +/- 21%, respectively (where Sco2 = [alpha] Sao2 + [beta] Sjo2 with [alpha] and [beta] being arterial and venous contributions). The contribution was similar among conditions but differed significantly among subjects (range, [almost equal to] 40:60 to [almost equal to] 0:100, arterial:venous).     

Real-time cerebral monitoring using multichannel near-infrared spectroscopy in total arch replacement

Multichannel near-infrared spectroscopy (NIRS) could detect change in the regional cerebral oxygenation by following animated pictures of oxy-hemoglobin (OxyHb), deoxy-hemoglobin (DeoxyHb) and total hemoglobin in operations for three surgical cases of thoracic aortic aneurysm with selective cerebral perfusion (SCP). Simultaneously measured jugular venous oxygen saturation (SjO₂) showed no change in parallel to OxyHb or DeoxyHb of NIRS. It was concluded that SjO₂ represented the entire rather than the local findings of the cerebral oxidative metabolism. Assessment of the intra cranial oxidative metabolism using a multichannel NIRS provided real-time information about the efficacy of SCP, while SjO₂ had a comprehensive limited value. The animation enabled the detection of regional hypoperfusion visually and instantly during SCP. This multichannel NIRS was a new real-time monitoring method and was useful to prevent cerebral neurological complication due to hypoperfusion during SCP.