Cerebral oxygenation measured by near-infrared spectroscopy: comparison with jugular bulb oximetry

Correlation between cerebral tissue and central venous oxygen saturation during off-pump coronary bypass graft surgery

We compared simultaneous regional cerebral oxygen saturation and central venous oxygen saturation at different time periods in 20 adult patients (median age, 57.9; range, 35 to 76 years) undergoing off-pump coronary artery bypass (OPCAB) graft surgery (n= 20). Mean arterial pressure (MAP), partial pressure of carbon dioxide (PcvCO(2)), heart rate, haematocrit (Hct), lactate and patient oxygen saturation (SpO(2)) were also recorded as a secondary analysis to determine independent predictors of cerebral desaturation and interactions between predictors. The cross-sectional analysis performed at each time point showed several significant moderate to strong positive correlations between central venous oxygen saturation and both right and left cerebral oxygen saturations; however, right cerebral saturations correlated better with central venous saturations than left cerebral saturation. Partial pressure of carbon dioxide (PcvCO(2)) was identified as a major predictor of cerebral saturation 0.59 (p < 0.001). Central venous saturation can be used as a surrogate measure of cerebral oxygen saturation during OPCAB surgery.

The change in regional cerebral oxygen saturation after stellate ganglion block

BACKGROUND

Stellate ganglion block (SGB) is known to increase blood flow to the innervations area of the stellate ganglion. Near infrared spectroscopy reflects an increased blood volume and allows continuous, non-invasive, and bedside monitoring of regional cerebral oxygen saturation (rSO(2)). We investigated the influence of SGB on bilateral cerebral oxygenation using a near infrared spectroscopy.

METHODS

SGB was performed on 30 patients with 1% lidocaine 10 ml using a paratracheal technique at the C6 level and confirmed by the presence of Horner's syndrome. The blood pressure (BP), heart rate (HR) and rSO(2) were measured before SGB and 5, 10, 15 and 20 minutes after SGB. Tympanic temperature of each ear was measured prior to SGB and 20 minutes after SGB.

RESULTS

The increments of the rSO(2) on the block side from the baseline were statistically significant at 5, 10, 15 and 20 minutes. The rSO(2) on the non-block side compared with the baseline, however, decreased at 15 and 20 minutes. The difference between the block and the non-block sides was significant at 15 and 20 minutes. The BP at 10, 15 and 20 minutes was increased and the HR was increased at 10 and 15 minutes.

CONCLUSIONS

We observed an increment of the rSO(2) on the block side from the baseline; however, the rSO(2) on the non-block side decreased.

Near infrared spectroscopy in children at high risk of low perfusion

PURPOSE OF REVIEW

Tissue oximetry has been suggested as a noninvasive tool to continuously monitor and detect states of low body perfusion. This review summarizes recent developments and available data on the use of near infrared spectroscopy (NIRS) in children at risk for low perfusion.

RECENT FINDINGS

During states of low cardiac output, cerebral blood flow and thus cerebral NIRS may be better preserved than in somatic tissue sites. Consequently, sites other than the frontal cerebral cortex have been investigated for a possible correlation with invasive measures of systemic perfusion and oxygenation (e.g. abdomen, flank, and muscle). The abdominal site seems preferable to the flank site NIRS (kidney region) application. In order to increase the sensitivity, specificity, and positive predictive value of tissue oximetry to detect systemic hypoperfusion, multisite NIRS such as a combination of cerebral and somatic site NIRS has been suggested. NIRS has also been used to assess systemic perfusion in patients undergoing first-stage palliation for hypoplastic left heart syndrome.

SUMMARY

Despite shortcomings in the ability of NIRS technology to accurately reflect validated and directly measured parameters of systemic oxygen delivery and blood flow, NIRS can certainly assist in the detection of low-flow states (low cardiac output). Large, randomized, prospective studies with well defined outcome parameters are still missing and warranted in order to clearly define the role of NIRS in children at risk for low perfusion.

Optimal flow rate for antegrade cerebral perfusion

OBJECTIVE

Antegrade cerebral perfusion is widely used in neonatal heart surgery, yet commonly used flow rates have never been standardized. The objective of this study was to determine the antegrade cerebral perfusion flow rate that most closely matches standard cardiopulmonary bypass conditions.

METHODS

Nine neonatal piglets underwent deep hypothermic cardiopulmonary bypass at a total body flow of 100 mL/kg/min (baseline). Antegrade cerebral perfusion was conducted via innominate artery cannulation at perfusion rates of 10, 30, and 50 mL/kg/min in random order. Cerebral blood flow was measured using fluorescent microspheres. Regional oxygen saturation and cerebral oxygen extraction were monitored.

RESULTS

Cerebral blood flow was as follows: baseline, 60 +/- 17 mL/100 g/min; antegrade cerebral perfusion at 50 mL/kg/min, 56 +/- 17 mL/100 g/min; antegrade cerebral perfusion at 30 mL/kg/min, 36 +/- 9 mL/100 g/min; and antegrade cerebral perfusion at 10 mL/kg/min, 13 +/- 6 mL/100 g/min. At an antegrade cerebral perfusion rate of 50 mL/kg/min, cerebral blood flow matched baseline (P = .87), as did regional oxygen saturation (P = .13). Antegrade cerebral perfusion at 30 mL/kg/min provided approximately 60% of baseline cerebral blood flow (P < .002); however, regional oxygen saturation was equal to baseline (P = .93). Antegrade cerebral perfusion at 10 mL/kg/min provided 20% of baseline cerebral blood flow (P < .001) and a lower regional oxygen saturation than baseline (P = .011). Cerebral oxygen extraction at antegrade cerebral perfusion rates of 30 and 50 mL/kg/min was equal to baseline (P = .53, .48) but greater than baseline (P < .0001) at an antegrade cerebral perfusion rate of 10 mL/kg/min. The distributions of cerebral blood flow and regional oxygen saturation were equal in each brain hemisphere at all antegrade cerebral perfusion rates.

CONCLUSION

Cerebral blood flow increased with antegrade cerebral perfusion rate. At an antegrade cerebral perfusion rate of 50 mL/kg/min, cerebral blood flow was equal to baseline, but regional oxygen saturation and cerebral oxygen extraction trends suggested more oxygenation than baseline. An antegrade cerebral perfusion rate of 30 mL/kg/min provided only 60% of baseline cerebral blood flow, but cerebral oxygen extraction and regional oxygen saturation were equal to baseline. An antegrade cerebral perfusion rate that closely matches standard cardiopulmonary bypass conditions is between 30 and 50 mL/kg/min.

Advances in near-infrared spectroscopy to study the brain of the preterm and term neonate

This article reviews tissue oximetry and imaging to study the preterm and newborn infant brain by near-infrared spectroscopy. These two technologies are now advanced; nearly 100 reports on their use in newborn infants have been published, and commercial instruments are available. The precision of oximetry, however, is a limitation for its clinical use of assessing cerebral oxygenation. Imaging of brain function needs very well defined protocols for sensory stimulation as well as signal analysis to provide meaningful results.

Noninvasive control of adequate cerebral oxygenation during low-flow antegrade selective cerebral perfusion on adults and infants in the aortic arch surgery

Real-time readings of the regional oxygen saturation (rSO(2)) using near-infrared spectroscopy (NIRS) during the aortic arch surgery can provide an early detection of perfusion or oxygenation abnormalities.

BACKGROUND

Aortic arch repair techniques using low-flow antegrade selective cerebral perfusion have been standardized to a certain degree. However, some of the often-stated beneficial effects have never been proven. Especially, the existence of an adequate continuous flow in both cerebral hemispheres during the surgical procedure still remains unclear as the monitoring of an effective perfusion remains a nonstandardized technique.

METHODS

Seventeen patients underwent surgical reconstruction of the aortic arch due to aortic aneurysm surgery (adult group n = 8 patients) or of the hypoplastic aortic arch due to hypoplastic left heart syndrome (HLHS) or aortic coarctation (infant group n = 9 patients) under general anesthesia and mild hypothermia (adult group 28 degrees C; infant group 25 degrees C). Mean weights were 92.75 +/- 14.00 kg and 4.29 +/- 1.32 kg, and mean ages were 58.25 +/- 10.19 years and 55.67 +/- 51.11 days in the adult group and the infant group, respectively. The cerebral O(2) saturation measurement was performed by continuous plotting of the somatic reflectance oximetry of the frontal regional tissue on both cerebral hemispheres (rSO(2), INVOS; Somanetics Corporation, Troy, MI, USA).

RESULTS

During low-flow antegrade perfusion via innominate artery, continuous plots with similar values of O(2) saturation (rSO(2)) in both cerebral hemispheres were observed, whereas a decrease in the rSO(2) values below the desaturation threshold correlated with a displacement or an incorrect positioning of the arterial cannula in the right subclavian artery.

CONCLUSIONS

Continuous monitorization of the cerebral O(2) saturation during aortic arch surgery in adults and infants is a feasible technique to control an adequate cannula positioning and to optimize clinical outcomes avoiding neurological complications related to cerebral malperfusion.

Near Infrared Spectroscopy (NIRS) in Children

Near infrared spectroscopy (NIRS) is a noninvasive method for the in vivo monitoring of tissue oxygenation. Originally used predominantly to assess cerebral oxygenation, NIRS has gained widespread popularity in many clinical settings in all age groups. Changes in regional tissue oxygenation as detected by NIRS may reflect the delicate balance between oxygen delivery and consumption in more than one organ system. However, more studies are required to establish the ability of NIRS monitoring to improve patient outcome. This review provides a comprehensive description of NIRS in children.

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).

The Application of Near-infrared Oximetry to Cerebral Monitoring During Aneurysm Embolization: A Comparison With Intraprocedural Angiography

Near-infrared spectroscopy (NIRS) has been used to monitor regional cerebral oxygen saturation (rSO2) in patients at risk of cerebral desaturation during surgical and neurointerventional procedures. However, the quantitative capabilities of the method have been questioned, as has its validation compared with jugular bulb oximetry. Here, we compare NIRS data acquired during coil embolization procedures with incidence of vasospasm as detected from angiography. Thirty-two subarachnoid hemorrhage patients underwent embolization. Bilateral SomaSensor strips (Invos 4100, Somanetics) were affixed to the forehead at constant anatomic positions, avoiding frontal sinuses and scalp hair. Mean arterial pressure, SaO2, end-tidal pCO2, temperature and Hb were held within a narrow range during the procedure. Ipsilateral angiography was performed every 10 to 15 minutes. An independent neuroradiologist classified any vasospasm in the parent vessel as mild (25% baseline), moderate (50%), severe (75%), or total (100%). Of all, 15/32 (46.9%) patients developed spasm; in 2 it was severe or total. There was no significant association between World Federation of Neurological Surgeons grade and baseline rSO2 signal (either ipsilateral or contralateral to the side of the aneurysm) (P=0.598). There was no significant association between side of aneurysm and baseline rSO2 signal (P=0.243). However, episodes of angiographic spasm were strongly associated with reduction in trend ipsilateral NIRS signal (P<0.001); furthermore, the degree of spasm (especially more than 75% vessel diameter reduction) was associated with a greater reduction in same-side NIRS signal (P<0.001) (2-level random effects regression model, Stata 8.2, Stata Corp, TX). NIRS may have a useful role to play in the detection of cerebral desaturation secondary to vasospasm during neuroendovascular procedures.

Anesthesia for pulmonary endarterectomy

Anesthetic care for patients undergoing pulmonary endarterectomy represents one of the most challenging tasks in cardiac anesthesia. Chronic thromboembolic pulmonary hypertension with its concomitant right ventricular failure may cause hemodynamic instability during anesthetic induction and the precardiopulmonary bypass (CPB) period, and the associated comorbidities (pulmonary, hepatic) may affect the actions and metabolism of anesthetic drugs. During the CPB period, proper perfusion patterns, cerebral oxygenation, and adequate hypothermia for deep hypothermic circulatory arrest must be achieved. During the post-CPB period the anesthesiologist must be prepared to treat residual pulmonary hypertension, pulmonary edema, pulmonary bleeding, right ventricular failure, and various metabolic and cardiovascular sequelae of hypothermic circulatory arrest. This review highlights the main issues the anesthesiologist faces during pulmonary endarterectomy, as well as suggests approaches to their management.

Cerebral oxygenation during hypoxia and resuscitation by using near-infrared spectroscopy in newborn piglets

BACKGROUND

Hypoxic events and cardiac arrest may cause brain damage in critical infants. This study investigated cerebral tissue oxygenation and oxygen extraction in a piglet model of hypoxic events, cardiac arrest and effects of resuscitation.

METHODS

For the hypoxia experiment, anesthetized newborn piglets were randomized to a hypoxia group (n = 8) with decreasing ventilatory rate to 0, and a control group (n = 8) with no hypoxic conditions. Regional cerebral tissue oxygen saturation (rScO2, detected by near-infrared spectroscopy) and oxygen saturation were recorded every 5 minutes for 100 minutes. Fractional cerebral tissue oxygen extraction (FTOE) was calculated as (arterial oxygen saturation [SaO2] - rScO2)/SaO2. For the resuscitation experiment, animals were grouped as hypoxia-no CPR (n = 4), control-no CPR (n = 4), and control-CPR (n = 4) after cardiac arrest. Standard cardiopulmonary resuscitation (CPR) was performed on the control-CPR group and observed for 30 minutes.

RESULTS

Immediate and significant changes in rScO2, and gradual changes in FTOE were observed during the hypoxia experiment. In the resuscitation experiment, no significant differences in rScO2 were found between groups. However, the highest FTOE was observed in the control-CPR group.

CONCLUSION

Noninvasive monitoring of rScO2 and evaluating FTOE changes during hypoxia and resuscitation may help clinicians evaluate brain tissue oxygenation and viability.

Use of tissue oxygenation index and fractional tissue oxygen extraction as non-invasive parameters for cerebral oxygenation. A validation study in piglets

OBJECTIVE

To evaluate the relation between cerebral tissue oxygenation index (TOI), measured with spatially resolved spectroscopy (SRS), and the different oxygenation parameters. To evaluate the relation between a new parameter named fractional tissue oxygen extraction (FTOE) and the cerebral fractional oxygen extraction (FOE).

METHODS

Six newborn piglets were measured at 33, 35, and 37 degrees C and in hypocapnia. Mean arterial blood pressure (MABP), haemoglobin (Hb), peripheral oxygen saturation (S(a)O(2)) and P(a)CO(2) were measured at each step. Cerebral blood flow (CBF) was measured by injection of coloured microspheres into the left atrium. Jugular bulb oxygen saturation (JVS), cerebral arterial and venous oxygen content (C(a)O(2) and C(v)O(2)) and FOE were calculated. TOI of the brain was calculated and FTOE was introduced as (S(a)O(2) - TOI)/S(a)O(2). The correlation was calculated with an ANCOVA test.

RESULTS

There was a positive correlation (R = 0.4 and p = 0.011) between TOI and JVS. No correlation was found with CBF, MABP or Hb. There was a positive correlation between P(a)CO(2) and cerebral TOI (R = 0.24 and p = 0.03). FTOE correlated well with FOE (R = 0.4 and p = 0.016) and there was a negative correlation between FTOE and P(a)CO(2) (R = 0.24, p = 0.03).

CONCLUSION

The measurement of TOI and FTOE by SRS correlated well with the cerebral venous saturation and FOE, respectively.

Acetazolamide Improves Cerebral Oxygenation During Exercise at High Altitude

Vuyk, Jaap, Jan Van Den Bos, Kees Terhell, Rene De Bos, Ad Vletter, Pierre Valk, Martie Van Beuzekom, Jack Van Kleef, and Albert Dahan. Acetazolamide improves cerebral oxygenation during exercise at high altitude. High Alt. Med. Biol. 7:290-301, 2006.--Acute mountain sickness is thought to be triggered by cerebral hypoxemia and be prevented by acetazolamide (Actz). The effect of Actz on cerebral oxygenation at altitude remains unknown. In 16 members of the 2005 Dutch Cho Oyu (8201 m, Tibet) expedition, the influence of Actz and exercise (750 mg PO daily) on heart rate, peripheral and regional cerebral oxygen saturation (Sa(O(2) ) and rS(O(2) )), the Lake Louise score (LLS), and psychomotor function were studied at 0 m 14 days prior to the expedition, after arrival at 3700 m on day 3, after arrival at 5700 m on day 29, and again at 5700 m before the end of the expedition on day 51. After arrival at 3700 m, the LLS of the climbers taking Actz (n = 8) was significantly lower compared to those who did not take Actz (n = 8): 0.75 +/- 1.0 versus 2.9 +/- 2.0, p < 0.05 (ANOVA). High LLSs were associated with low rS(O(2) ) values in rest and exercise (p < 0.01 and p < 0.001). With altitude, resting Sa(O(2) ) and resting rS(O(2) ) decreased significantly (p < 0.001), irrespective of Actz use. Exercise at 3700 m and 5700 m reduced Sa(O(2) ) and rS(O(2) ) even further compared to rest (p < 0.001), although at 3700 m the rS(O(2) ) was preserved better in those who took Actz (55.3 +/- 4.3% versus 47.9 +/- 5.7%, p < 0.05). Irrespective of Actz use, with altitude, the percentage of omissions in the vigilance and tracking test increased while the climbers' scores on vigor decreased (p < 0.05). In conclusion, at altitude, exercise-induced reduction in cerebral oxygenation is less in climbers on Actz compared to climbers not taking Actz. This effect is nullified after several weeks at altitude due to acclimatization in climbers not taking Actz.

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.

Development and validation of a multiwavelength spatial domain near-infrared oximeter to detect cerebral hypoxia-ischemia

Detection of cerebral hypoxia-ischemia in infants remains problematic, as current monitors in clinical practice are impractical, insensitive, or nonspecific. Our study develops a multiwavelength spatial domain construct for near-infrared spectroscopy (NIRS) to detect cerebral hypoxia-ischemia and evaluates the construct in several models. The NIRS probe contains photodiode detectors 2, 3, and 4 cm from a three-wavelength, light-emitting diode. A construct determines cerebral O(2) saturation based on spatial domain principles. Device performance and construct validity are examined in in-vitro models simulating the brain, and in piglets subjected to hypoxia, hypoxia-ischemia, and hyperoxic conditions using a weighted average of arterial and cerebral venous O(2) saturation measured by CO-oximetry. The results in the brain models verify key equations in the construct and demonstrate reliable performance of the device. In piglets, the device measures cerebral O(2) saturation with bias +/-4% and precision +/-8%. In conclusion, this NIRS device accurately detects cerebral hypoxia-ischemia and is of a design that is practical for clinical application.

MR susceptometry for measuring global brain oxygen extraction

Monitoring of oxygen saturation in jugular venous blood gives an estimate of the balance of global oxygen delivery and cerebral oxygen consumption. We present a noninvasive approach to measure oxygen saturation in vivo in the internal jugular vein using MR susceptometry by exploiting the characteristic susceptibility of deoxyhemoglobin, and demonstrate the feasibility of performing such measurements in a group of subjects. We assessed the sensitivity of the method for detecting small changes in oxygen saturation by monitoring the variations observed during breath-holding and hypoventilation experiments. Unlike alternative methods, the susceptometric technique does not require calibration.

Near-infrared spectroscopy in the fetus and neonate

Near-infrared spectroscopy allows for real-time, noninvasive measurement of cerebral hemodynamics and oxygenation at the bed-side. This article describes animal and clinical research using near-infrared spectroscopy to study cerebral hemodynamic function in the fetus, neonate, and child.

Monitoring the brain before, during, and after cardiac surgery to improve long-term neurodevelopmental outcomes

Innovation in surgical and medical management of cardiac disease has generated a dramatic improvement in operative survival. Along with these favourable results in terms of survival is the heightened awareness of neurologic complications, which often become evident beyond the early postoperative period. A large, multicentre prospective study found serious neurologic injury occurs in about one-twentieth of patients after myocardial revascularization in adults.1More subtle evidence of persistent cognitive decline and functional impairment has been shown to occur in over two-fifths of such patients.2Acute neurologic abnormalities are reported in up to one-fifth of infants and children who undergo cardiac surgery.3–6Lasting impairments in cognitive, motor, and expressive functioning have been reported in up to three-fifths of children who have undergone complex cardiac surgery during infancy.7Specifically, gross and fine motor delays, visual-spatial problems, language deficits and long-term emotional and behavioural problems have been found.8–13

Cerebral oxygenation monitoring: near-infrared spectroscopy

Neurological complications during critical illness remain a frequent cause of morbidity and mortality. To date, monitors of cerebral function including electroencephalography, jugular bulb mixed venous oxygen saturation and transcranial Doppler, either require an invasive procedure and/or are not sensitive enough to effectively identify patients at risk for cerebral hypoxia. Near-infrared spectroscopy is a noninvasive device that uses infrared light, a technique similar to pulse oximetry, to penetrate living tissue and estimate brain tissue oxygenation by measuring the absorption of infrared light by tissue chromophores. The following article reviews the latest technology available to monitor cerebral oxygenation, near-infrared spectroscopy, its advantages and disadvantages, the currently available evidence-based medicine that demonstrates that this technology can identify deficits in cerebral oxygenation, and that monitoring such deficits allows for therapy to reverse cerebral oxygenation issues and thereby prevent long-term neurological sequelae.

Effect of alpha-stat vs. pH-stat strategies on cerebral oximetry during moderate hypothermic cardiopulmonary bypass

BACKGROUND AND OBJECTIVES

This study was undertaken to compare the effect of alpha-stat vs. pH-stat strategies for acid-base management on regional cerebral oxygen saturation (RsO2) in patients undergoing moderate hypothermic haemodilution cardiopulmonary bypass (CPB).

METHODS

In 14 adult patients undergoing elective coronary artery bypass grafting, an awake RsO2 baseline value was monitored using a cerebral oximeter (INVOS 5100). Cerebral oximetry was then monitored continuously following anaesthesia and during the whole period of CPB. Mean +/- SD of RsO2, CO2, mean arterial pressure and haematocrit were determined before bypass and during the moderate hypothermic phase of the CPB using the alpha-stat followed by pH-stat strategies of acid-base management. Alpha-stat was then maintained throughout the whole period of CPB.

RESULTS

The mean baseline RsO2 in the awake patient breathing room air was 59.6 +/- 5.3%. Following anaesthesia and ventilation with 100% oxygen, RsO2 increased up to 75.9 +/- 6.7%. Going on bypass, RsO2 significantly decreased from a pre-bypass value of 75.9 +/- 6.7% to 62.9 +/- 6.3% during the initial phase of alpha-stat strategy. Shifting to pH-stat strategy resulted in a significant increase of RsO2 from 62.9 +/- 6.3% to 72.1 +/- 6.6%. Resuming the alpha-stat strategy resulted in a significant decrease of RsO2 to 62.9 +/- 7.8% which was similar to the RsO2 value during the initial phase of alpha-stat.

CONCLUSION

During moderate hypothermic haemodilutional CPB, the RsO2 was significantly higher during the pH-stat than during the alpha-stat strategy. However, the RsO2 during pH-stat management was significantly higher than the baseline RsO2 value in the awake patient breathing room air, denoting luxury cerebral perfusion. In contrast, the RsO2 during alpha-stat was only slightly higher than the baseline RsO2, suggesting that the alpha-stat strategy avoids luxury perfusion, but can maintain adequate cerebral oxygen supply-demand balance during moderate hypothermic haemodilutional CPB.

Randomized Controlled Trial of Pericardial Blood Processing With a Cell-Saving Device on Neurologic Markers in Elderly Patients Undergoing Coronary Artery Bypass Graft Surgery

BACKGROUND

Processing of pericardial shed blood with a cell-saving device was claimed to prevent lipid microembolization and to protect from neurocognitive dysfunction after cardiopulmonary bypass. The present study tested the hypothesis that processing of pericardial shed blood with a cell-saving device during cardiopulmonary bypass would significantly decrease serum levels of protein S100B, and improve brain oxygen saturation and neurologic outcome, all markers of brain injury in elderly patients.

METHODS

Forty patients, 65 years of age and older, undergoing coronary artery bypass graft with cardiopulmonary bypass, were prospectively randomly assigned to processing of pericardial shed blood with a cell-saving device or to conventional use of a standard closed venous reservoir where cardiotomy blood was collected and reinfused through the arterial circuit (control group). Serum in S100B was measured 30 minutes, 4 hours, 24 hours, and 48 hours after surgery. Near-infrared spectroscopy monitoring was performed during the procedure and the National Institutes of Health stroke scale was measured before surgery and at the time of discharge of the hospital.

RESULTS

Patients in the cell-saving device group averaged 72 +/- 3 years of age and underwent 3.1 +/- 0.7 coronary artery grafts with a mean of 62 +/- 20 minutes of cardiopulmonary bypass time. Patients in the control group averaged 75 +/- 4 years of age (p = 0.03) and underwent 3.3 +/- 0.6 coronary artery grafts (p = 0.49) with a mean of 75 +/- 25 minutes of cardiopulmonary bypass time (p = 0.12). The quantity of blood administered from the cell-saving device averaged 281 +/- 162 mL per patient. Serum protein S100B levels averaged 0.06 +/- 0.03 before surgery and 0.51 +/- 0.23 microg/L 30 minutes after surgery in the cell-saving device patients compared with 0.076 +/- 0.04 before surgery (p = 0.32) and 1.48 +/- 0.66 (p < 0.0001) in the control patients. The near-infrared spectroscopy baseline mean value of left and right cortical region was 58% +/- 12% and 55% +/- 7% in the cell-saving device group versus 59% +/- 7% and 53% +/- 6% in the control group (p = 0.67 and 0.36), and no difference occurred over time in each group. The National Institutes of Health stroke score before and after surgery was similar in the two groups. There was one cerebrovascular complication in the control group (1 of 20, 5%) after surgery.

CONCLUSIONS

The difference between the two groups occurred 30 minutes after surgery, at which time serum levels of protein S100B were significantly higher in the control group compared with cell-saving device patients. Although use of the cell-saving device was not associated with higher brain oxygen saturation nor changes in the National Institutes of Health stroke score, it is associated with lesser release of nonspecific markers of brain injury in elderly patients.

Screening for unilateral intracranial abnormalities using near infrared spectroscopy: a preliminary report

Near infrared spectroscopy (NIRS) is being increasingly used for medical applications, including neurosurgical care. This preliminary report describes the use of a low cost, indigenous, non-invasive system where NIRS is used to identify superficial unilateral intracranial abnormalities. The optical density (OD) over each hemisphere was initially studied in 50 normal volunteers. The specificity, sensitivity, reliability and reproducibility of the NIRS generated from the developed equipment in detecting OD were thus confirmed. The OD over each hemisphere was then measured in 71 other individuals, immediately after a computed tomography (CT) scan of the brain was performed. Data was statistically analysed to find the average OD difference (compared to the opposite side) of the various intracranial compartments. Differences in OD suggested a unilateral intracranial abnormality. All those in whom OD differences were detected with the NIRS system had unilateral abnormalities on the CT scan. None of the 53 patients who had a normal CT scan had significant differences in OD.

Near-infrared spectroscopy to monitor cerebral oxygen saturation in single-ventricle physiology

OBJECTIVES

Near-infrared spectroscopy monitors cerebral oxygen saturation. This parameter parallels jugular venous oxygen saturation and reflects the balance between cerebral oxygen supply and demand. Experience with near-infrared spectroscopy in univentricular physiology is limited. This study explores the relationship between cerebral oxygen saturation, jugular venous oxygen saturation, and other variables of cerebral perfusion in a model of univentricular physiology.

METHODS

Univentricular physiology was created in newborn piglets by means of an aortopulmonary shunt, echocardiography-guided atrial septostomy, tricuspid valve avulsion, and pulmonary artery occlusion. Intra-aortic balloon inflation was used to increase afterload. Cerebral oxygen saturation monitoring (INVOS 5100; Somanetics Corp, Troy, Mich), physiologic recordings, and stable-isotope microsphere determination of cerebral blood flow were performed at baseline and after conversion to univentricular physiology (30 minutes, 120 minutes, and during afterload augmentation).

RESULTS

Univentricular physiology resulted in lower cerebral oxygen saturation, arterial oxygen content, jugular venous oxygen saturation, and cerebral oxygen delivery. Afterload augmentation increased cerebral oxygen saturation, arterial oxygen content, and jugular venous oxygen saturation, whereas cerebral oxygen delivery was unaffected because of lower cerebral blood flow. Cerebral oxygen saturation predicted jugular venous oxygen saturation, arterial oxygen saturation, and arterial oxygen content. No association was found with cerebral oxygen delivery, which decreased in parallel with cerebral oxygen saturation when the single-ventricle physiology model was established but failed to increase during afterload augmentation.

CONCLUSIONS

This study shows that in univentricular physiology cerebral oxygen saturation correlates well with jugular venous oxygen saturation, arterial oxygen saturation, and arterial oxygen content. However, our findings suggest that in singe-ventricle physiology changes in cerebral oxygen saturation need to be interpreted in the context of changes in arterial oxygenation.

Regional cerebral saturation monitoring with near-infrared spectroscopy during selective antegrade cerebral perfusion: Diagnostic performance and relationship to postoperative stroke

OBJECTIVE

To investigate whether regional cerebral tissue oxygen saturation monitoring during hypothermic selective antegrade cerebral perfusion in surgery involving the aortic arch can predict neurologic sequelae and to evaluate the diagnostic performance of near-infrared spectroscopy monitoring in this setting.

METHODS

Data from 46 consecutive patients were analyzed. Selective antegrade cerebral perfusion was established by perfusion of the right subclavian artery (with or without left carotid artery perfusion) or by separate concomitant perfusion of the innominate and the left carotid arteries. The bilateral regional cerebral tissue oxygen saturation index was monitored by using near-infrared spectroscopy equipment (INVOS 4100). Stroke was the primary clinical end point, along with the indices of diagnostic performance.

RESULTS

Six patients died in the hospital, and 6 patients (13%) experienced a perioperative stroke. In patients with stroke, regional cerebral tissue oxygen saturation values were significantly lower during selective antegrade cerebral perfusion, and regional cerebral tissue oxygen saturation tended to be lower in the affected hemisphere. In receiver operating characteristic curve analysis, the area under the curve for relative regional cerebral tissue oxygen saturation values ranged from 0.72 to 0.87. During selective antegrade cerebral perfusion, regional cerebral tissue oxygen saturation between 76% and 86% of baseline had a sensitivity up to 83% and a specificity up to 94% in identifying individuals with stroke. The associated odds ratio for stroke was 5.6 (95% confidence interval, 0.5-144) to 21 (95% confidence interval, 1.8-566).

CONCLUSIONS

Monitoring of regional cerebral tissue oxygen saturation by using near-infrared spectroscopy during selective antegrade cerebral perfusion allows detection of clinically important cerebral desaturation. It can help predict perioperative neurologic sequelae. Its performance as a diagnostic instrument is satisfying and supports its use as a noninvasive trend monitor of cerebral saturation.

Correlation between cerebral and mixed venous oxygen saturation during moderate versus tepid hypothermic hemodiluted cardiopulmonary bypass

OBJECTIVE

This study was undertaken to compare cerebral oxygen saturation (RsO(2)) and mixed venous oxygen saturation (SvO(2)) in patients undergoing moderate and tepid hypothermic hemodiluted cardiopulmonary bypass (CPB).

DESIGN

Prospective study.

SETTINGS

University hospital operating room.

PARTICIPANTS

Fourteen patients undergoing elective coronary artery bypass graft surgery using hypothermic hemodiluted CPB.

INTERVENTIONS

During moderate (28 degrees -30 degrees C) and tepid hypothermic (33 degrees -34 degrees C) hemodiluted CPB, RsO(2) and SvO(2) were continuously monitored with a cerebral oximeter via a surface electrode placed on the patient's forehead and with the mixed venous oximeter integrated in the CPB machine, respectively.

MEASUREMENTS AND MAIN RESULTS

Mean +/- standard deviation of RsO(2), SvO(2), PaCO(2), and hematocrit were determined prebypass and during moderate and tepid hypothermic phases of CPB while maintaining pump flow at 2.4 L/min/m(2) and mean arterial pressure in the 60- to 70-mmHg range. Compared with a prebypass value of 76.0% +/- 9.6%, RsO(2) was significantly decreased during moderate hypothermia to 58.9% +/- 6.4% and increased to 66.4% +/- 6.7% after slow rewarming to tepid hypothermia. In contrast, compared with a prebypass value of 78.6% +/- 3.3%, SvO(2) significantly increased to 84.9% +/- 3.6% during moderate hypothermia and decreased to 74.1% +/- 5.6% during tepid hypothermia. During moderate hypothermia, there was poor agreement between RsO(2) and SvO(2) with a gradient of 26%; however, during tepid hypothermia, there was a strong agreement between RsO(2) and SvO(2) with a gradient of 6%. The temperature-uncorrected PaCO(2) was maintained at the normocapnic level throughout the study, whereas the temperature-corrected PaCO(2) was significantly lower during the moderate hypothermic phase (26.8 +/- 3.1 mmHg) compared with the tepid hypothermic phase (38.9 +/- 3.7 mmHg) of CPB. There was a significant and positive correlation between RsO(2) and temperature-corrected PaCO(2) during hypothermia.

CONCLUSIONS

During moderate hypothermic hemodiluted CPB, there was a significant increase of SvO(2) associated with a paradoxic decrease of RsO(2) that was attributed to the low temperature-corrected PaCO(2) values. During tepid CPB after slow rewarming, regional cerebral oxygen saturation was increased in association with an increase with the temperature-corrected PaCO(2) values. The results show that during hypothermic hemodiluted CPB using the alpha-stat strategy for carbon dioxide homeostasis, cerebral oxygen saturation is significantly higher during tepid than moderate hypothermia.

Congenital Heart Surgery 2005: The brain: It’s the heart of the matter

Operative mortality after repair of even the most complex congenital heart lesions has become rare. As such, the gaze of the surgical team has been diverted beyond that of early survival to focus on decreasing early and late morbidity. Important and concerning information is accumulating delineating the vulnerability of the neonatal brain to injury as the result of congenital heart disease and/or the techniques employed to correct the lesions. For many years the prevention of neurologic injury associated with congenital heart surgery has concentrated on "unraveling" the mysteries of the deleterious effects of intentional brain ischemia (in the form of deep hypothermic circulatory arrest) and developing methods to interrupt the pathway of irreversible injury. In the late 1990s, alternative perfusion techniques were developed to minimize or theoretically avoid the use of deep hypothermic circulatory arrest where it was once thought to be mandatory. Simultaneously, the rather routine use of noninvasive, real-time, neurologic monitoring has provided surgical teams the opportunity to intervene and prevent brain injury , thus eliminating the historic reliance on postoperative surrogate markers to define the presence of brain injury. It is yet undetermined whether these strategies will translate into improved short- and long-term neurologic outcome. Common to all surgical disciplines is a trend that as mortality decreases for a particular disease process, focus is adjusted, and refinements in treatment protocols are designed to minimize morbidity of the disease and its treatment. This natural refining process of a discipline's maturation is increasingly present in the field of congenital heart surgery.

Cerebral oxygenation monitoring using near infrared spectroscopy during controlled hypotension

BACKGROUND

Controlled hypotension (CH) is used to limit intraoperative blood loss and decrease the need for homologous transfusions. Despite the efficacy of the technique, hypotension has the potential to affect cerebral perfusion and oxygen delivery. There are no data providing a direct measurement of cerebral oxygenation during this technique.

METHODS

The current study prospectively evaluated cerebral oxygenation during CH using near infrared spectroscopy. Nineteen patients ranging in age from 6 to 18 years were enrolled in the study. CH was provided using a combination of intravenous opioids and sevoflurane supplemented with labetolol as necessary.

RESULTS

There were a total of 268 readings obtained from the cerebral oximeter. The baseline cerebral oximeter reading was 81+/-8% on the right and 82+/-7% on the left. During CH (mean arterial pressure of 65-69, 60-64, 55-59, and <54 mmHg), the right cerebral oximeter values were 80+/-9, 78+/-8, 78+/-10, and 84+/-9%, respectively while the left cerebral oximeter values were 79+/-7, 80+/-7, 78+/-8, and 78+/-8%, respectively. Of the 268 readings, there were 11 points (4%) at which either the left or right cerebral oximeter was 10-19 less than the baseline value and no points at which the reading was 20 or more from the baseline value.

CONCLUSIONS

Our preliminary data with a measurement of cerebral oxygenation demonstrates the safety of CH within the accepted mean blood pressure recommendations of 55-65 mmHg.

Comparison between cerebral tissue oxygenation index measured by near-infrared spectroscopy and venous jugular bulb saturation in children

OBJECTIVE

To compare the cerebral tissue oxygenation index (TOI) measured by near-infrared spectroscopy (NIRS) with venous oxygen saturation in the jugular bulb (SjO(2)) during elective cardiac catheterization in children.

DESIGN AND SETTING

Prospective observational clinical study in a catheterization laboratory for pediatric cardiology.

PATIENTS

Sixty children with congenital heart defects admitted to the catheterization laboratory.

MEASUREMENTS AND RESULTS

TOI measured noninvasively by NIRS was compared to SjO(2) measured in the jugular bulb during cardiac catheterization. Patients were divided into two groups regarding body weight: below (n=29) and above 10 kg (n=31). Linear regression analysis and Pearson's correlation coefficient were calculated. Bland-Altman analysis, sensitivity, and specificity calculation for spatially resolved near-infrared spectroscopy with a cutoff level of 60% were performed. Simultaneously measured values for SjO(2) (67.3+/-9.8%, 40-84.1%) and TOI (65.7+/-7.2%, 39-80%) showed a significant correlation; the correlation in children weighing under 10 kg was stronger in children weighing over 10 kg. Bland-Altman analysis showed a mean bias of -1.8% with limits of agreement between 11.7% and -15.3% for all children. Sensitivity and specificity of the SRS method were 46% and 91%, respectively, for all children and 53% and 83% respectively in infants weighing under 10 kg.

CONCLUSIONS

The results demonstrate that despite a significant correlation, sensitivity of spatially resolved spectroscopy is poor, and it is questionable whether TOI can be used reliably to detect low SjO(2).

Near-infrared spectroscopy: a tool to monitor cerebral hemodynamic and metabolic changes after cardiac arrest in rats

INTRODUCTION

Cardiac arrest (CA) is associated with poor neurological outcome and is associated with a poor understanding of the cerebral hemodynamic and metabolic changes. The objective of this study was to determine the applicability of near-infrared spectroscopy (NIRS), to observe the changes in cerebral total hemoglobin (T-Hb) reflecting cerebral blood volume, oxygenation state of Hb, oxidized cytochrome oxidase (Cyto-C), and brain water content following CA.

METHODS

Fourteen rats were subjected to normothermic (37.5 degrees C) or hypothermic (34 degrees C) CA induced by 8 min of asphyxiation. Animals were resuscitated with ventilation, cardiopulmonary resuscitation (CPR), and epinephrine (adrenaline). Hypothermia was induced before CA. NIRS was applied to the animal head to measure T-Hb with a wavelength of 808 nm (n = 10) and oxygenated/deoxygenated Hb, Cyto-C, and brain water content with wavelengths of 620-1120 nm (n = 4).

RESULTS

There were no technical difficulties in applying NIRS to the animal, and the signals were strong and consistent. Normothermic CA caused post-resuscitation hyperemia followed by hypoperfusion determined by the level of T-Hb. Hypothermic CA blunted post-resuscitation hyperemia and resulted in more prominent post-resuscitation hypoperfusion. Both, normothermic and hypothermic CA resulted in a sharp decrease in oxygenated Hb and Cyto-C, and the level of oxygenated Hb was higher in hypothermic CA after resuscitation. There was a rapid increase in brain water signals following CA. Hypothermic CA attenuated increased water signals in normothermic CA following resuscitation.

CONCLUSION

NIRS can be applied to monitor cerebral blood volume, oxygenation state of Hb, Cyto-C, and water content following CA in rats.

Brain tissue oxygenation index measured by near infrared spatially resolved spectroscopy agreed with jugular bulb oxygen saturation in normal pediatric brain: a pilot study

OBJECTIVES

This observational, prospective pediatric human study was performed to determine the agreement between brain tissue oxygenation indices (TOI) measured by near infrared spatially resolved spectroscopy and jugular bulb oxygen saturation values (SjO(2)).

METHODS

Five cardiac patients without neurological impairment who were admitted into the critical care unit after open-heart surgery with jugular bulb venous catheters were enrolled. Their mean age was 8.6 months and mean body weight was 6.7 kg. Simultaneous measurements of brain TOI using NIR0-300 (Hamamatsu Photonics, Hamamatsu City, Japan) and SjO(2) values from blood samples were recorded.

RESULTS

The TOI range was 59+/-9% and the SjO(2) range was 58+/-17%. The correlation coefficient R was 0.64 (p=0.11; n=14). Bland-Altman plotting revealed a bias of -3.4%, and precision of 7.2% (n=14). Intra-class correlation reliability analysis showed kappa of 0.55.

CONCLUSION

Statistically, brain TOI was in reasonable agreement with SjO(2) in pediatric patients with normal brain within the measurement range from 50 to 70%.

Hypotensive extremely low birth weight infants have reduced cerebral blood flow

OBJECTIVES

Whether extremely low birth weight (ELBW) infants are at risk of cerebral hypoperfusion is uncertain because key issues concerning their cerebral blood flow (CBF) and mean arterial pressure (MAP) are unresolved: (1) whether CBF is pressure-passive or autoregulated; (2) the normal level of MAP; and (3) whether inotropic drugs used to increase MAP might inadvertently impair CBF. We addressed these issues in ELBW infants undergoing intensive care.

METHODS

CBF (measured by near-infrared spectroscopy) and MAP were measured in 17 infants aged 1.5 to 40.5 hours.

RESULTS

Five infants remained normotensive (MAP 37 +/- 2 mm Hg, [mean +/- SEM]); twelve became hypotensive (MAP 25 +/- 1 mm Hg) and were treated with dopamine (10-30 mug x kg(-1) per min). CBF of hypotensive infants (14 +/- 1 mL x 100 g(-1) per min) was lower than the CBF of normotensive infants (19 +/- mL x 100 g(-1) per min). After commencement of dopamine in hypotensive infants, MAP increased (29 +/- 1 mm Hg) and CBF also increased (18 +/- 1 mL x 100g(-1) per min). CBF was correlated with MAP in hypotensive infants before (R = 0.62) and during (R = 0.67) dopamine, but not in normotensive infants. A breakpoint was identified in the CBF versus MAP autoregulation curve of untreated infants at MAP = 29 mm Hg; no breakpoint was evident in dopamine-treated infants.

CONCLUSIONS

In ELBW infants (1) cerebral autoregulation is functional in normotensive but not hypotensive infants; (2) a breakpoint exists at approximately 30 mm Hg in the CBF-MAP autoregulation curve; and (3) dopamine improves both MAP and CBF.

Neurological Monitoring for Congenital Heart Surgery

The incidence of neurological complications after pediatric cardiac surgery ranges from 2% to 25%. The causes are multifactorial and include preoperative brain malformations, perioperative hypoxemia and low cardiac output states, sequelae of cardiopulmonary bypass, and deep hypothermic circulatory arrest. Neurological monitoring devices are readily available and the anesthesiologist can now monitor the brain during pediatric cardiac surgery. In this review we discuss near-infrared cerebral oximetry, transcranial Doppler ultrasound, and electroencephalographic monitors for use during congenital heart surgery. After review of the basic principles of each monitoring modality, we discuss their uses during pediatric heart surgery. We present evidence that multimodal neurological monitoring in conjunction with a treatment algorithm may improve neurological outcome for patients undergoing congenital heart surgery and present one such algorithm.

Cerebral oxygen desaturation is associated with early postoperative neuropsychological dysfunction in patients undergoing cardiac surgery

OBJECTIVE

To evaluate the relationship between cerebral oxygen saturation and neuropsychological dysfunction after cardiac surgery.

DESIGN

Prospective and observational study.

SETTING

Operating room and cardiac floor of a university hospital.

PARTICIPANTS

One hundred one patients undergoing elective cardiac surgery with cardiopulmonary bypass

INTERVENTION

Bilateral noninvasive cerebral oxygen saturations were monitored over the forehead. The anesthetic and surgical techniques were performed as usual, and no interventions were attempted based on the monitor. Neuropsychological outcome was assessed by the Mini-Mental State Examination (MMSE) and the antisaccadic eye movement test (ASEM).

MEASUREMENTS AND MAIN RESULTS

Preoperative baseline values of cerebral oxygen saturation (rSO(2)) were 58.6% +/- 10.2%. Patients with the nadir rSO(2) <35% had significantly higher incidences of postoperative ASEM and MMSE impairments than those with rSO(2) always above 35% (44% and 33% v 12% and 9%, respectively). Patients with areas of rSO(2) <40% for more than 10 minutes . % presented with a significantly higher incidence of postoperative ASEM and MMSE impairments than those with areas of rSO(2) <40% for less than 10 minutes . % (42% and 32% v 13% and 10%, respectively). Patients with postoperative ASEM or MMSE impairment had significantly lower nadir rSO(2) and significantly larger areas of rSO(2) <40%, <45%, and <50% than those with normal postoperative neuropsychological outcome. However, multivariate logistic regression analysis showed that areas of rSO(2) <40% were the only predictor for both postoperative ASEM and MMSE impairments.

CONCLUSIONS

Intraoperative cerebral oxygen desaturation is associated with early postoperative neuropsychological dysfunction in patients undergoing cardiac surgery with cardiopulmonary bypass. However, it remains to be determined whether interventions to maintain adequate cerebral oxygenation may improve neuropsychological outcome.

Relation of cerebral tissue oxygenation index to central venous oxygen saturation in children

OBJECTIVE

To evaluate the relationship between the cerebral tissue oxygenation index measured by near-infrared spectroscopy and central venous oxygen saturation (SvO2) after corrective surgery of congenital heart defects in children.

DESIGN

Prospective observational clinical study.

SETTING

A tertiary neonatal and paediatric intensive care unit for paediatric cardiology.

PATIENTS

Neonates and children consecutively admitted to the paediatric cardiology intensive care unit after corrective surgery of non-cyanotic congenital heart defects.

MEASUREMENTS AND RESULTS

Forty-three children were studied. Cerebral tissue oxygenation index, measured non-invasively by near-infrared spectroscopy, was compared to SvO2, measured by a catheter placed in the right atrium, and to haemodynamic and respiratory parameters. Pearson's correlation coefficients and p values were calculated. Simultaneously measured values for SvO2 (62.2+/-9.8%, 39.8-80.4%) and cerebral tissue oxygenation index (56.7+/-8.8%, 35.8-71.2%) showed a significant correlation ( r=0.52, p<0.001).

CONCLUSION

Cerebral tissue oxygenation index and SvO2 are not interchangeable parameters, but cerebral tissue oxygenation index reflects the haemodynamic influence on cerebral oxygenation after cardiovascular surgery. Further work is necessary to confirm the clinical role of continuous non-invasive measurement of cerebral tissue oxygenation index with regard to the variations of global systemic oxygen consumption after cardiac surgery in children.