Incongruous effect of phenylephrine on changes in cerebral blood volume measured by near-infrared spectroscopy (NIRS) indicating extracranial contamination.

We assessed extracranial contamination of the near-infrared spectroscopy (NIRS) signal during administration of phenylephrine. The study was performed with NIRO 200NX which employs both the Modified Beer-Lambert (MBL) method to measure total hemoglobin (tHb, expressed in µM), and Spatially Resolved Spectroscopy (SRS) to measure total hemoglobin content (nTHI, expressed in arbitrary units (a.u.)). SRS tends to not be affected by extracranial blood flow. As vasoconstriction with phenylephrine mainly occurs in the extracranial area, we hypothesized that if NIRS measurements are indeed prone to extracranial contamination, tHb will be more affected by the administration of phenylephrine than nTHI. After ethical committee approval, 20 consenting cardiac surgery patients were included. Phenylephrine was administered whenever clinically indicated and its effect on nTHI and tHb was evaluated. To adjust for the difference in raw scale units, Z-scores were calculated. Data were analyzed with Wilcoxon Signed Ranks Test and the Hodges-Lehmann method. A total of 191 data sets were obtained in 20 patients (10 male, 65 ± 15 years, 77 ± 16 kg, 166 ± 11 cm). The median difference before and after administration of phenylephrine was - 0.006 a.u. [95%CI - 0.010 to - 0.002] (p < 0.001) and - 0.415 µM [95%CI - 0.665 to - 0.205] (p < 0.001) for nTHI and tHb, respectively. The median difference between the Z-scores of nTHI and tHb was - 0.02 [95%CI - 0.04 to - 0.003] (p = 0.03), with a higher variability in the Z-scores of tHb. Phenylephrine induced significant larger changes in MBL values compared to SRS values, indicating that the MBL method might be more prone to extracranial contamination. Trial and clinical registry: Trial registration number: B670201939459, ethical committee number: 2019/0265, date of approval: March 19, 2019.

Population pharmacokinetics of cefazolin before, during and after cardiopulmonary bypass to optimize dosing regimens for children undergoing cardiac surgery.

Objectives: The objective of this study was to characterize cefazolin serum pharmacokinetics in children before, during and after cardiopulmonary bypass (CPB), in order to derive an evidence-based dosing regimen. Patients and methods: This study included children who received cefazolin before surgical incision, before cessation of CPB and after surgery. Blood samples of total and unbound cefazolin concentrations were collected before, during and after CPB. The cefazolin concentration-time profiles were analysed using population pharmacokinetic modelling and predictors for interindividual variability in pharmacokinetic parameters were investigated. Subsequently, optimized dosing regimens were developed using stochastic simulations. Clinicaltrials.gov: NCT02749981. Results: A total of 494 total and unbound cefazolin concentrations obtained from 56 children (aged 6 days to 15 years) were included. A two-compartment model with first-order elimination plus an additional compartment for the effect of CPB best described the data. Clearance (1.56 L/h), central volume (1.93 L) and peripheral volume (2.39 L) were allometrically scaled by body weight. The estimated glomerular filtration rate (eGFR) was identified as a covariate on clearance and the serum albumin concentration was associated with maximum protein binding capacity. Our simulations showed that an additional bolus dose at the start of CPB improves the PTA in typical patients from 59% to >94%. Prolonged surgery and preserved renal function (i.e. drop in eGFR <25%) had a negative impact on PTA. Conclusions: We propose an optimized dosing regimen for cefazolin during cardiac surgery in paediatric patients to avoid treatment failure due to inadequate antibiotic prophylaxis.

Microvascular reactivity monitored with near-infrared spectroscopy is impaired after induction of anaesthesia in cardiac surgery patients: An observational study.

BACKGROUND: Induction of anaesthesia causes significant macrohaemodynamic changes, but little is known about its effects on the microcirculation. However, alterations in microvascular perfusion are known to be associated with impaired tissue oxygenation and organ dysfunction. Microvascular reactivity can be assessed with vascular occlusion testing, which evaluates the response of tissue oxygen saturation to transient ischaemia and reperfusion. OBJECTIVE: The aim of the current study was to evaluate the effects of an opioid-based anaesthesia induction on microvascular reactivity. We hypothesised that despite minimal blood pressure changes, microvascular function would be impaired. DESIGN: Prospective, observational study. SETTING: Single-centre, tertiary university teaching hospital, Belgium. PATIENTS: Thirty-five adult patients scheduled for elective coronary artery bypass grafting surgery. INTERVENTION: Microvascular reactivity was assessed before and 30 min after anaesthesia induction by means of vascular occlusion testing and near-infrared spectroscopy. MAIN OUTCOME MEASURES: Tissue oxygen saturations, desaturation rate, recovery time (time from release of cuff to the maximum value) and rate of recovery were determined. RESULTS: Data are expressed as median (minimum to maximum). Tissue oxygen saturation was higher after induction of anaesthesia [70 (54 to 78) vs. 73 (55 to 94)%, P = 0.015]. Oxygen consumption decreased after induction, appreciable by the higher minimum tissue oxygen saturation [45 (29 to 69) vs. 53 (28 to 81)%, P < 0.001] and the slower desaturation rate [11 (4 to 18) vs. 9 (5 to 16)% min, P < 0.001]. After induction of anaesthesia, recovery times were longer [40 (20 to 120) vs. 48 (24 to 356) s, P = 0.004] and the rate of recovery was lower [114 (12 to 497) vs. 80 (3 to 271)% min, P < 0.001]. CONCLUSION: After induction of anaesthesia, oxygen consumption was decreased. The longer recovery times and slower rates of recovery indicate impaired microvascular reactivity after induction of anaesthesia. TRIAL REGISTRATION: The research project was registered at ClinicalTrials.gov (NCT02034682).

Evaluation of different near-infrared spectroscopy technologies for assessment of tissue oxygen saturation during a vascular occlusion test.

An increasing number of NIRS devices are used to provide measurements of peripheral tissue oxygen saturation (StO2). The aim of the present study is to test the hypothesis that despite technological differences between devices, similar trend values will be obtained during a vascular occlusion test. The devices compared are NIRO-200NX, which measures StO2 and oxyhemoglobin by spatially resolved spectroscopy and the Beer-Lambert law, respectively, and INVOS 5100C and Foresight Elite, which both measure StO2 with the Beer-Lambert law, enhanced with the spatial resolution technique. Forty consenting adults scheduled for CABG surgery were recruited. The respective sensors of the three NIRS devices were applied over the brachioradial muscle. Before induction of anesthesia, 3 min of ischemia were induced by inflating a blood pressure cuff at the upper arm, whereafter cuff pressure was rapidly released. Tissue oxygenation measurements included baseline, minimum and maximum values, desaturation and resaturation slopes, and rise time. Comparisons between devices were performed with the Kruskal-Wallis test with post hoc Mann-Whitney pairwise comparisons. Agreement was evaluated using Bland-Altman plots. Oxyhemoglobin measured with NIRO responded faster than the other NIRS technologies to changes in peripheral tissue oxygenation (20 vs. 27-40 s, p ≤ 0.01). When comparing INVOS with Foresight, oxygenation changes were prompter (upslope 311 [92-523]%/min vs. 114[65-199]%/min, p ≤ 0.01) and more pronounced (minimum value 36 [21-48] vs. 45 [40-51]%, p ≤ 0.01) with INVOS. Significant differences in tissue oxygen saturation measurements were observed, both within the same device as between different devices using the same measurement technology.

Postoperative complications in cardiac patients undergoing noncardiac surgery.

PURPOSE OF REVIEW: In this article we review the current knowledge on the underlying mechanisms of perioperative myocardial injury, the preoperative methods of predicting these complications, the diagnostic tools for detecting perioperative myocardial injuries, and the available protective strategies to prevent or attenuate the extent of myocardial injury. RECENT FINDINGS: The last years' new insights have provided a better understanding of the problem of perioperative myocardial injury and infarction. Specifically, the importance of early diagnosis and prompt treatment are increasingly getting attention. Concomitantly, the results of recent large multicenter studies have challenged classical therapeutic approaches in the perioperative treatment of cardiac patients undergoing noncardiac surgery. SUMMARY: These new insights will help to better tailor individual strategies to prevent or minimize perioperative cardiac complications. Especially, early diagnosis and intensification of treatment will get specific interest in the coming years.

Characterizing cerebral and locomotor muscle oxygenation to incremental ramp exercise in healthy children: relationship with pulmonary gas exchange.

AIMS: To characterize the oxygenation responses at cerebral and locomotor muscle level to incremental exercise in children and to assess the interrelationship with the pulmonary gas exchange responses. METHODS: Eighteen children (9 boys, 9 girls) (mean age 10.9 ± 1.0 years) performed incremental cycle ramp exercise to exhaustion. The concentration of cerebral and muscle oxygenated (O2Hb) and deoxygenated (HHb) hemoglobin (by means of near-infrared spectroscopy) and pulmonary gas exchange was recorded. Cerebral and muscle O2Hb and HHb values were expressed as functions of oxygen uptake (VO2) and breakpoints were detected by means of double linear model analysis. The respiratory compensation point (RCP) was determined. The breakpoints in cerebral and muscle O2Hb and HHb were compared and correlated to RCP. RESULTS: The subjects reached peak power output of 105 ± 18 W and VO2peak of 43.5 ± 7.0 ml min-1 kg-1. Cerebral O2Hb increased to an intensity of 89.4 ± 5.5 %VO2peak, where a breakpoint occurred at which cerebral O2Hb started to decrease. Cerebral HHb increased slightly to 88.1 ± 4.8 %VO2peak, at which the increase was accelerated. Muscle HHb increased to 90.5 ± 4.8 %VO2peak where a leveling-off occurred. RCP occurred at 89.3 ± 4.3 %VO2peak. The breakpoints and RCP did not differ significantly (P = 0.13) and were strongly correlated (r > 0.70, P < 0.05). There were no differences between boys and girls (P = 0.43) and there was no significant correlation with VO2peak (P > 0.05). CONCLUSIONS: It was shown that cerebral and muscle oxygenation responses undergo significant changes as work rate increases and show breakpoints in the ongoing response at high intensity (85-95 %VO2peak). These breakpoints are strongly interrelated and associated with changes in pulmonary gas exchange.

Cerebral near-infrared spectroscopy in the care of patients during cardiological procedures: a summary of the clinical evidence.

Patients undergoing cardiological procedures generally have significant cardiovascular morbidity, and therefore these patients might be at risk for major periprocedural complications. The ability to closely monitor the hemodynamic status would present a major advantage to optimize patient care in this setting. The aim of this review is to assess the available evidence for the use of near-infrared spectroscopy (NIRS) in the care of patients during cardiological procedures. A systematic literature search was conducted using electronic bibliographic databases (MEDLINE, PubMed, EMBASE) from their first available date using the following search strategy: (spectroscopy, near-infrared OR infrared spectroscopy OR NIRS OR cerebral oxygen*) AND (interventional OR electrophysiological OR catheterization OR ablation OR ICD OR defibrillator). Inclusion criteria were limited to human studies, English language and cardiac patients. All manuscripts concerning the use of NIRS in every area of catheterization and electrophysiology were included. The literature search yielded eleven observational studies and five case reports concerning the research question. No randomized trials could be retrieved. Six studies evaluated NIRS during supraventricular and ventricular arrhythmias, one during transcatheter aortic valve implantations, and four studies assessed the use of NIRS in pediatric catheterization procedures. Overall, the studies demonstrated that NIRS provides a very quick representation of cerebral oxygen saturation and that it might identify changes that could not be predicted from standard hemodynamic monitoring. However, the evidence is currently too low to conclude that NIRS can optimize patient care during cardiological procedures.

Assessment of Cerebral Autoregulation Patterns with Near-infrared Spectroscopy during Pharmacological-induced Pressure Changes.

BACKGROUND: Previous work has demonstrated paradoxical increases in cerebral oxygen saturation (ScO2) as blood pressure decreases and paradoxical decreases in ScO2 as blood pressure increases. It has been suggested that these paradoxical responses indicate a functional cerebral autoregulation mechanism. Accordingly, the authors hypothesized that if this suggestion is correct, paradoxical responses will occur exclusively in patients with intact cerebral autoregulation. METHODS: Thirty-four patients undergoing elective cardiac surgery were included. Cerebral autoregulation was assessed with the near-infrared spectroscopy-derived cerebral oximetry index (COx), computed by calculating the Spearman correlation coefficient between mean arterial pressure and ScO2. COx less than 0.30 was previously defined as functional autoregulation. During cardiopulmonary bypass, 20% change in blood pressure was accomplished with the use of nitroprusside for decreasing pressure and phenylephrine for increasing pressure. Effects on COx were assessed. Data were analyzed using two-way ANOVA, Kruskal-Wallis test, and Wilcoxon and Mann-Whitney U test. RESULTS: Sixty-five percent of patients had a baseline COx less than 0.30, indicating functional baseline autoregulation. In 50% of these patients (n = 10), COx became highly negative after vasoactive drug administration (from -0.04 [-0.25 to 0.16] to -0.63 [-0.83 to -0.26] after administration of phenylephrine, and from -0.05 [-0.19 to 0.17] to -0.55 [-0.94 to -0.35] after administration of nitroprusside). A negative COx implies a decrease in ScO2 with increase in pressure and, conversely, an increase in ScO2 with decrease in pressure. CONCLUSIONS: In this study, paradoxical changes in ScO2 after pharmacological-induced pressure changes occurred exclusively in patients with intact cerebral autoregulation, corroborating the hypothesis that these paradoxical responses might be attributable to a functional cerebral autoregulation.

Society of cardiovascular anesthesiologists: the effect of blood pressure regulation during aortic coarctation repair on brain, kidney, and muscle oxygen saturation measured by near-infrared spectroscopy: a randomized, clinical trial.

BACKGROUND: In this study, we compared the effects of 3 frequently used arterial blood pressure-regulating agents on brain (rScO2), renal (SrO2), and muscle (SmO2) oxygen saturation, during aortic coarctation repair in children. Based on the reported adverse effect of sodium nitroprusside (SNP) on left-sided rScO2 during aortic coarctation repair, we tested the hypothesis that the alterations in left rScO2 occurring with SNP would not be present with sevoflurane and nitroglycerin (NTG). Additionally, we explored the effects of blood pressure regulation with SNP, NTG, or sevoflurane on right-sided rScO2, SrO2, and SmO2. METHODS: Children with isolated aortic coarctation undergoing surgical repair through a left thoracotomy without the use of cardiopulmonary bypass were considered eligible for the study. During aortic cross-clamping, control of mean arterial blood pressure (MAP) was conducted according to randomization by the use of SNP, NTG, or sevoflurane to obtain a mean target right brachial blood pressure of 120% to 150% of the MAP value before cross-clamping. Bilateral rScO2, SrO2, and SmO2 were recorded continuously with near-infrared spectroscopy. As a primary end point, the maximal relative change in left-sided rScO2 in response to aortic cross-clamping was compared among treatment groups. RESULTS: Ten patients per group were included. No significant difference among treatment groups was observed in maximal relative change in left-sided rScO2 (SNP versus sevoflurane: mean difference -0.7%, 99% confidence interval [CI] -31% to 29%, P = 1.0; SNP versus NTG: mean difference -1.8%, 99% CI -32% to 28%, P = 1.0; sevoflurane versus NTG: mean difference -1.1%, 99% CI -31% to 29%, P = 1.0). Additional analyses also detected no difference between groups in right rScO2 (P = 0.4). Compared with NTG, treatment with SNP resulted in a significantly larger (-64% ± 17% vs -34% ± 25%, P = 0.01) and faster (-9 ± 4 %·min(-1) vs -4 ± 3 %·min(-1), P = 0.004) decrease in SmO2. Right-sided rScO2 and MAP showed a poor correlation for NTG (r = -0.2, P = 0.93), whereas borderline for sevoflurane (r = 0.44, P = 0.09) and SNP (r = 0.56, P = 0.04). CONCLUSIONS: The mean differences in left-sided rScO2 among the patients treated with SNP, NTG, or sevoflurane for proximal hypertension during aortic cross-clamping were no more than 32%. Additional analysis demonstrated a low MAP-rScO2 dependence with the use of NTG. Because NTG also resulted in a smaller and slower decrease of oxygen saturation in peripheral tissues, our data suggest that its use might be preferable for proximal blood pressure control during surgical procedures involving aortic cross-clamping.

Implementation of a structured information transfer checklist improves postoperative data transfer after congenital cardiac surgery.

BACKGROUND: During one hospital stay, a patient can be cared for by five different units. With patient transfer from one unit to another, it is of prime importance to convey a complete picture of the patient's situation to minimise the risk of medical errors and to provide optimal patient care. OBJECTIVE(S): This study was designed to test the hypothesis that the implementation of a standardised checklist used during verbal patient handover could improve postoperative data transfer after congenital cardiac surgery. DESIGN: Prospective, pre/postinterventional clinical study. SETTING: Cardiac centre of a university hospital. PATIENTS: Forty-eight patients younger than 16 years undergoing heart surgery. INTERVENTIONS: A standardised checklist was developed containing all data that, according to the investigators, should be communicated during the handover of a paediatric cardiac surgery patient from the operating room to the ICU. MAIN OUTCOME MEASURES: Data transfer during the postoperative handover before and after implementation of the checklist was evaluated. Duration of handover, number of interruptions, number of irrelevant data and number of confusing pieces of information were noted. Assessment of the handover process by ICU medical and nursing staff was quantified. RESULTS: After implementation of the information transfer checklist, the overall data transfer increased from 48 to 73% (P < 0.001). The duration of data transfer decreased from a median (range) of 6 (2 to 16) to 4 min (2 to 19) (P = 0.04). The overall handover assessment by the intensive care nursing staff improved significantly after implementation of the checklist. CONCLUSION: Implementation of an information transfer checklist in postoperative paediatric cardiac surgery patients resulted in a more complete transfer of information, with a decrease in the handover duration.

Cerebral oxygen desaturation during beach chair position.

CONTEXT: Cases of ischaemic brain damage have been reported in relatively healthy patients undergoing shoulder surgery in the beach chair position. Unrecognised cerebral hypoperfusion may have contributed to these catastrophic events, indicating that routine anaesthesia monitoring may not suffice. Near-infrared spectroscopy (NIRS) provides a non-invasive, continuous method to measure regional cerebral oxygen saturation (rScO2). OBJECTIVES: The aim of this clinical investigation was to evaluate the prevalence of regional cerebral oxygen desaturation in patients undergoing shoulder surgery in the upright position during routine anaesthesia management. We also aimed to identify some causal factors for cerebral desaturation. DESIGN: Prospective, observational, blinded study. SETTING: University hospital. Observation period from 19 05 2008 to 26 08 2008. PATIENTS: Twenty consecutive adult patients presenting for elective shoulder surgery under general anaesthesia in the beach chair position were enrolled. Patients with clinically apparent neurological or cognitive dysfunction were excluded. INTERVENTIONS: Routine anaesthesia management and standard monitoring were used. The responsible anaesthesiologist was blinded to the rScO2 data and was not informed about the purpose of the study. MAIN OUTCOME MEASURES: The prevalence of cerebral oxygen desaturation was measured. RESULTS: With beach chair positioning, rScO2 decreased significantly from 79± to 57±9% on the left side and from 77±10 to 59±10% on the right side (P<0.001). A relative decrease in rScO2 of more than 20% occurred in 80% of patients when the beach chair position was adopted. Postural decreases in cerebral oxygenation were related to blood pressure (r=0.60, P=0.007) and end-tidal carbon dioxide concentration (r=0.47, P=0.035). CONCLUSION: The high prevalence of significant cerebral oxygen desaturation during shoulder surgery in the upright position underlines the need for close monitoring. NIRS might constitute a valuable technique to detect cerebral hypoperfusion in this high-risk group of patients.

Near-infrared spectroscopy for monitoring spinal cord ischemia during hybrid thoracoabdominal aortic aneurysm repair.

PURPOSE: To describe a simple, noninvasive technique to detect changes in oxygen saturation at the level of the spinal cord and to suggest its suitability for individualized blood pressure management during and after thoracoabdominal aneurysm repair. CASE REPORT: A 53-year-old man with a history of multiple arch and thoracic aortic procedures underwent staged hybrid treatment of a large TAAA due to chronic dissection from the distal aortic arch into the iliac arteries. During the procedures, near-infrared spectroscopy (NIRS) sensors were applied over the 10th thoracic vertebra for continuous monitoring of tissue oxygen saturation (S(s)O(2)) during endovascular repair. After stent-graft deployment, mean S(s)O(2) decreased significantly. Moreover, the relationship between S(s)O(2) and arterial blood pressure became linear, reflecting pressure dependency of spinal cord perfusion after stent deployment. CONCLUSION: These data show that NIRS monitors post-endograft changes in S(s)O(2) that were strongly related to arterial blood pressure. Regional NIRS monitoring at the vertebral level may function as a valuable noninvasive guide to the management of blood pressure during thoracoabdominal aneurysm repair, both intra- and postoperatively.

Manual versus target-controlled infusion remifentanil administration in spontaneously breathing patients.

BACKGROUND: The combination of propofol-remifentanil for procedural deep sedation in spontaneously breathing patients is characterized by the frequent incidence of side effects, especially respiratory depression. These side effects may be due to either the drug combination or the drug delivery technique. Target-controlled infusion (TCI) might optimize drug delivery. In this prospective, randomized, double-blind study in patients undergoing elective colonoscopy, we thus tried to answer two questions: first, if adding remifentanil to propofol surpasses the disadvantages of the combination of these two products, and second, if administration of remifentanil via TCI decreases the incidence of side effects, compared to manually controlled administration. METHODS: Patients undergoing elective colonoscopy were randomly assigned to receive remifentanil via manually controlled continuous infusion (MCI) (0.125 microg x kg(-1) x min(-1) for 2 min followed by a continuous infusion of 0.05 microg x kg(-1) x min(-1)), TCI remifentanil (1 ng/mL), or placebo (normal saline either as TCI or manual infusion of equivalent rate). All patients received TCI propofol, adjusted to a target concentration level that provided deep sedation in which patients were not responsive to verbal commands, but maintained spontaneous ventilation without assistance. RESULTS: Significantly more patients in the placebo group showed movement, cough and hiccup, which transiently interfered with the examination. There were no clinically significant differences in hemodynamic or recovery variables among all groups. Remifentanil administered via TCI resulted in a decrease in propofol requirements. The incidence of hypopnea and apnea was less frequent when remifentanil was administered via TCI compared to MCI (TCI n = 7, MCI n = 16, P < 0.05). CONCLUSION: The combination of remifentanil and propofol for deep sedation in spontaneously breathing patients, offered better conditions for colonoscopy than propofol used as a single drug. Remifentanil administered via TCI resulted in a decrease in propofol dosing and in a lower incidence in apnea and respiratory depression (TCI n = 7, MCI n = 16, P < 0.05), compared to manually controlled administration of remifentanil.

Why and how to assess cerebral autoregulation?

Around the turn of the century, a better understanding of the complex physiology of cerebral blood flow (CBF) regulation has emerged. It is now acknowledged that cerebral autoregulation is much more complicated than we previously thought it was, with the shape of the autoregulation curve and limits of autoregulation that may vary enormously and unpredictably, both within and between patients. The consequence is that to safeguard the cerebral circulation, the dogma that an empirically chosen blood pressure guarantees adequate CBF in any individual patient has to be abandoned. Integration of cerebral autoregulation monitoring in daily perioperative patient care offers the opportunity to guide blood pressure management to the individual patient's need. The most common approach tests the effect of changes in blood pressure on an estimate of CBF. However, a "gold standard" to assess cerebral autoregulation is not yet available, and the literature shows considerable disparity of methods and criteria.

Aerobic Interval Training Impacts Muscle and Brain Oxygenation Responses to Incremental Exercise.

The purpose of the present study was to assess the effects of aerobic interval training on muscle and brain oxygenation to incremental ramp exercise. Eleven physically active subjects performed a 6-week interval training period, proceeded and followed by an incremental ramp exercise to exhaustion (25 W min-1). Throughout the tests pulmonary gas exchange and muscle (Vastus Lateralis) and brain (prefrontal cortex) oxygenation [concentration of deoxygenated and oxygenated hemoglobin, HHb and O2Hb, and tissue oxygenation index (TOI)] were continuously recorded. Following the training intervention V . ⁢ O 2 peak had increased with 7.8 ± 5.0% (P < 0.001). The slope of the decrease in muscle TOI had decreased (P = 0.017) 16.6 ± 6.4% and the amplitude of muscle HHb and totHb had increased (P < 0.001) 40.4 ± 15.8 and 125.3 ± 43.1%, respectively. The amplitude of brain O2Hb and totHb had increased (P < 0.05) 40.1 ± 18.7 and 26.8 ± 13.6%, respectively. The training intervention shifted breakpoints in muscle HHb, totHb and TOI, and brain O2Hb, HHb, totHb and TOI to a higher absolute work rate and V . ⁢ O 2 (P < 0.05). The relative (in %) change in V . ⁢ O 2 peak was significantly correlated to relative (in %) change slope of muscle TOI (r = 0.69, P = 0.011) and amplitude of muscle HHb (r = 0.72, P = 0.003) and totHb (r = 0.52, P = 0.021), but not to changes in brain oxygenation. These results indicate that interval training affects both muscle and brain oxygenation, coinciding with an increase in aerobic fitness (i.e., V . ⁢ O 2 peak). The relation between the change in V . ⁢ O 2 peak and muscle but not brain oxygenation suggests that brain oxygenation per se is not a primary factor limiting exercise tolerance during incremental exercise.

Differences in cerebral and muscle oxygenation patterns during exercise in children with univentricular heart after Fontan operation compared to healthy peers.

BACKGROUND: We assess whether the lower exercise tolerance in children with univentricular heart (UVH) after Fontan operation is associated with altered peripheral muscular and cerebral tissue oxygenation. METHODS: 18 children with UVH and 20 healthy subjects performed an incremental ramp exercise test. Changes in the cerebral and muscular pattern of oxygenated (O2Hb) and deoxygenated hemoglobin (HHb) and local tissue oxygenation (TOI) were analyzed by means of Near Infrared Spectroscopy (NIRS). Correlations between arterial saturation during exercise and tissue oxygenation were evaluated. RESULTS: In UVH, maximal oxygen consumption (VO2peak/kg, 28.9 ±â€¯7.9 vs. 46.3 ±â€¯11.9 ml/min/kg, P < 0.001), heart rate (HRpeak, 168 ±â€¯13 vs. 193 ±â€¯12 bpm, P < 0.001) and load (Ppeak, 73 ±â€¯19 vs. 133 ±â€¯68 W, P < 0.001) were lower, VE/VCO2 slope was higher (34.5 ±â€¯5.9 vs. 27.1 ±â€¯3.9, P < 0.001). A faster and steeper course up to the same level of HHb and absent increase in O2Hb was seen at cerebral level in UVH; tissue oxygenation index (TOI) demonstrated a steady decrease from the start of exercise. At the muscular level, HHb curve has a similar pattern compared to controls, with an early cessation. O2Hb has a similar pattern, but with early discontinuation at a higher O2Hb-level. Muscular TOI has the same course throughout exercise, starting from a lower level. Lower arterial saturation and higher age correlated with lower VO2peak; higher amplitude of muscular TOI and lower amplitude cerebral TOI correlated with higher VO2peak. CONCLUSION: Children after Fontan procedure have different oxygenation mechanisms at muscular and cerebral level. This reflects a different balance between O2 supply to O2 demand which might contribute to the reduced exercise tolerance in this patient population.

Different Patterns of Cerebral and Muscular Tissue Oxygenation 10 Years After Coarctation Repair.

The purpose of this study was to assess whether the lower exercise tolerance in children after coarctation repair is associated with alterations in peripheral tissue oxygenation during exercise. A total of 16 children after coarctation repair and 20 healthy control subjects performed an incremental ramp exercise test to exhaustion. Cerebral and locomotor muscle oxygenation were measured by means of near infrared spectroscopy. The responses of cerebral and muscle tissue oxygenation index (cTOI, mTOI), oxygenated (O2Hb), and deoxygenated hemoglobin (HHb) as a function of work rate were compared. Correlations between residual continuous wave Doppler gradients at rest, arm-leg blood pressure difference and local oxygenation responses were evaluated. Age, length, and weight was similar in both groups. Patients with aortic coarctation had lower peak power output (Ppeak) (72.3 ± 20.2% vs. 106 ± 18.7%, P < 0.001), VO2peak/kg (37.3 ± 9.1 vs. 44.2 ± 7.6 ml/kg, P = 0.019) and %VO2peak/kg (85.7 ± 21.9% vs. 112.1 ± 15.5%, P < 0.001). Cerebral O2Hb and HHb had a lower increase in patients vs. controls during exercise, with significant differences from 60 to 90% Ppeak (O2Hb) and 70% to 100% Ppeak (HHb). Muscle TOI was significantly lower in patients from 10 to 70% Ppeak and muscle HHb was significantly higher in patients vs. controls from 20 to 80% Ppeak. Muscle O2Hb was not different between both groups. There was a significant correlation between residual resting blood pressure gradient and Δmuscle HHb/ΔP at 10-20W and 20-30W (r = 0.40, P = 0.039 and r = 0.43, P = 0.034). Children after coarctation repair have different oxygenation responses at muscular and cerebral level. This reflects a different balance between O2 supply to O2 demand which might contribute to the reduced exercise tolerance in this patient population.