Differences in cerebral and hepatic oxygenation in response to intradialytic blood transfusion in patients undergoing hemodialysis

Differences between Hepatic and Cerebral Regional Tissue Oxygen Saturation at the Onset of Intradialytic Hypotension

BACKGROUND

Intradialytic hypotension (IDH) is a critical pathological condition associated with all-cause mortality in patients undergoing hemodialysis (HD). However, few studies have investigated IDH-related changes in hepatic and cerebral regional tissue oxygen saturation (rSO2). This study investigated IDH-induced changes in hepatic and cerebral rSO2.

METHODS

Hepatic and cerebral rSO2 during HD were measured using an INVOS 5100C oxygen saturation monitor, and their percentage (%) changes during the development of IDH were analyzed. Ninety-one patients undergoing HD were investigated, including twenty with IDH.

RESULTS

In patients with IDH, % changes in hepatic and cerebral rSO2 decreased at the onset of IDH. Additionally, the % change in hepatic rSO2 was significantly larger than that in cerebral rSO2 (p < 0.001). In patients without IDH, no significant differences were found between the % changes in hepatic and cerebral rSO2 at the time of the lowest systolic blood pressure during HD. Multivariable linear regression analysis showed that the difference between the % changes in cerebral and hepatic rSO2 was significantly associated with the development of IDH (p < 0.001) and the ultrafiltration rate (p = 0.010).

CONCLUSIONS

Hepatic and cerebral rSO2 significantly decreased during the development of IDH, and hepatic rSO2 was more significantly decreased than cerebral rSO2 at the onset of IDH.

Effects of percutaneous transluminal angioplasty and associated factors in access hand oxygenation in patients undergoing hemodialysis

In hemodialysis (HD) patients with arteriovenous fistula (AVF), changes in systemic or peripheral tissue circulation occur non-physiologically via the presence of AVF; however, associations between blood flow and tissue oxygenation in the brain and access hand are uncertain. In this study, 85 HD patients with AVF were included and evaluated for changes in flow volume (FV) and regional oxygen saturation (rSO₂) in the brain and hands with AVF before and after percutaneous transluminal angioplasty (PTA). Furthermore, we evaluated the factors that determine access hand rSO₂ without stenosis after PTA. Brachial arterial FV increased after PTA (p < 0.001), and carotid FV decreased (p = 0.008). Access hand rSO₂ significantly decreased after PTA (p < 0.001), but cerebral rSO₂ did not significantly change (p = 0.317). In multivariable linear regression analysis of factors associated with access hand rSO₂, serum creatinine (standardized coefficient: 0.296) and hemoglobin (standardized coefficient: 0.249) were extracted as independent factors for access hand rSO₂. In conclusion, a decrease in access hand oxygenation and maintenance of cerebral oxygenation were observed throughout PTA. To maintain access hand oxygenation, it is important to adequately manage Hb level and maintain muscle mass, in addition to having an AVF with appropriate blood flow.

Cerebral oxygenation and body mass index association with cognitive function in chronic kidney disease patients without dialysis: a longitudinal study

In chronic kidney disease (CKD) patients, the prevalence of cognitive impairment increases with CKD progression; however, longitudinal changes in cognitive performance remain controversial. Few reports have examined the association of cerebral oxygenation with cognitive function in longitudinal studies. In this study, 68 CKD patients were included. Cerebral regional oxygen saturation (rSO₂) was monitored. Cognitive function was evaluated using mini-mental state examination (MMSE) score. Clinical assessments were performed at study initiation and 1 year later. MMSE score was higher at second measurement than at study initiation (p = 0.022). Multivariable linear regression analysis showed that changes in MMSE were independently associated with changes in body mass index (BMI, standardized coefficient: 0.260) and cerebral rSO₂ (standardized coefficient: 0.345). This was based on clinical factors with p < 0.05 (changes in BMI, cerebral rSO₂, and serum albumin level) and the following confounding factors: changes in estimated glomerular filtration rate, hemoglobin level, proteinuria, salt and energy intake, age, presence of diabetes mellitus, history of comorbid cerebrovascular disease, and use of renin–angiotensin system blocker. Further studies with a larger sample size and longer observational period are needed to clarify whether maintaining BMI and cerebral oxygenation improve or prevent the deterioration of cognitive function.

Association between hepatic oxygenation on near-infrared spectroscopy and clinical factors in patients undergoing hemodialysis

The hepato-splanchnic circulation directly influences oxygenation of the abdominal organs and plays an important role in compensating for the blood volume reduction that occurs in the central circulation during hemodialysis (HD) with ultrafiltration. However, the hepato-splanchnic circulation and oxygenation cannot be easily evaluated in the clinical setting of HD therapy. We included 185 HD patients and 15 healthy volunteers as the control group in this study. Before HD, hepatic regional oxygen saturation (rSO2), a marker of hepatic oxygenation reflecting the hepato-splanchnic circulation and oxygenation, was monitored using an INVOS 5100c oxygen saturation monitor. Hepatic rSO2 was significantly lower in patients undergoing HD than in healthy controls (56.4 ± 14.9% vs. 76.2 ± 9.6%, p < 0.001). Multivariable regression analysis showed that hepatic rSO2 was independently associated with body mass index (BMI; standardized coefficient: 0.294), hemoglobin (Hb) level (standardized coefficient: 0.294), a history of cardiovascular disease (standardized coefficient: -0.157), mean blood pressure (BP; standardized coefficient: 0.154), and serum albumin concentration (standardized coefficient: 0.150) in Model 1 via a simple linear regression analysis. In Model 2 using the colloid osmotic pressure (COP) in place of serum albumin concentration, the COP (standardized coefficient: 0.134) was also identified as affecting hepatic rSO2. Basal hepatic oxygenation before HD might be affected by BMI, Hb levels, a history of cardiovascular disease, mean BP, serum albumin concentration, and the COP. Further prospective studies are needed to clarify whether changes in these parameters, including during HD, affect the hepato-splanchnic circulation and oxygenation in HD patients.

Εndothelial and microvascular function in CKD: Evaluation methods and associations with outcomes

BACKGROUND

Cardiovascular disease is the major cause of morbidity and mortality in patients with chronic kidney disease (CKD). Endothelial dysfunction, the hallmark of atherosclerosis, is suggested to be involved pathogenetically in cardiovascular and renal disease progression in these patients.

METHODS

This is a narrative review presenting the techniques and markers used for assessment of microvascular and endothelial function in patients with CKD and discussing findings of the relevant studies on the associations of endothelial dysfunction with co-morbid conditions and outcomes in this population.

RESULTS

Venous Occlusion Plethysmography was the first method to evaluate microvascular function; subsequently, several relevant techniques have been developed and used in patients with CKD, including brachial Flow-Mediated Dilatation, and more recently, Near-Infrared Spectroscopy and Laser Speckle Contrast Analysis. Furthermore, several circulating biomarkers are commonly used in clinical research. Studies assessing endothelial function using the above techniques and biomarkers suggest that endothelial dysfunction occurs early in CKD and contributes to the target organ damage, cardiovascular events, death and progression towards end-stage kidney disease.

CONCLUSIONS

Older and newer functional methods and several biomarkers have assessed endothelial dysfunction in CKD; accumulated evidence supports an association of endothelial dysfunction with outcomes. Future research with new, non-invasive and easily applicable methods could further delineate the role of endothelial dysfunction on cardiovascular and renal disease progression in patients with CKD.

Clinical factors affecting cerebral oxygenation in patients undergoing peritoneal dialysis

BACKGROUND

Although cerebral regional oxygen saturation (rSO₂) is significantly lower in hemodialysis (HD) patients than that in healthy controls, investigations on cerebral oxygenation in peritoneal dialysis (PD) patients are limited. We aimed to confirm the cerebral oxygenation status and identify the factors affecting cerebral rSO₂ in PD patients.

METHODS

Thirty-six PD patients (21 men and 15 women; mean age, 62.8 ± 12.7 years) were recruited. In addition, 27 healthy volunteers (17 men and 10 women; mean age, 43.5 ± 18.8 years) were recruited as a control group. Cerebral rSO₂ was monitored at the forehead using an INVOS 5100c oxygen saturation monitor.

RESULTS

Cerebral rSO₂ was significantly lower in PD patients than that in healthy controls (57.0 ± 7.3% vs 68.9 ± 8.6%, p < 0.001); moreover, cerebral rSO₂ was significantly correlated with natural logarithm (Ln)-PD duration (r = -0.389, p = 0.019) and serum albumin concentration (r = 0.370, p = 0.026) in a simple linear regression analysis. Multivariable linear regression analysis was performed using variables that showed a significant correlation and p < 0.20 (serum creatinine, serum sodium, Ln-C-reactive protein, and dosage of erythropoiesis-stimulating agent) with the cerebral rSO₂. Cerebral rSO₂ was independently associated with Ln-PD duration (standardized coefficient: -0.339) and serum albumin concentration (standardized coefficient: 0.316).

CONCLUSIONS

Cerebral rSO₂ was significantly affected by the PD duration and serum albumin concentration. Further prospective studies are needed to clarify whether preventing a decrease in serum albumin concentration leads to the maintenance of cerebral oxygenation in patients undergoing PD.

Monitoring of near-infrared spectrum values during packed red blood cell transfusion in pediatric intensive care unit

OBJECTIVES

Packed red blood cell (PRBC) transfusion is one of the most common treatment options in pediatric intensive care unit (PICU) which targets a better cerebral oxygenation. This study aimed to show the cerebral near-infrared spectroscopy (cNIRS) changes during PRBC transfusions in PICU.

MATERIAL AND METHODS

In this prospective observational study, changes in regional cerebral tissue oxygen saturation (rSO2) in pediatric patients, who required PRBC transfusion were monitored. All the cNIRS and related values were classified as baseline values. The same values were measured and calculated at the end of transfusion and named as 4th-hour values. Further measurements and calculations were made three hours later and named as 7th-hour values. Changes in cNIRS, cerebral tissue fractional oxygen extraction (CTFOE), cNIRS variability index (cNIRS-VI) were compared using Friedman test.

RESULTS

A total of 53 PRBC transfusions were monitored. Baseline haemoglobin increased from 6.3 (5.9, 6.7) gr/dL to 8.6 (8.4, 9) gr/dL at the 7th-hour. cNIRS values improved during transfusion (P=0.012), with a concomitant decrease in cNIRS-VI and CTFOE values (P<0.001 and P=0.017 consecutively) CONCLUSION: Our study revealed that there is an increase in cNIRS and related values after transfusion compared to baseline values in critically ill children admitted to a PICU. Age of PRBC did not have an effect on delta-cNIRS or post-transfusion hemoglobin values. There is a moderate correlation between the baseline cNIRS values and delta-cNIRS value after the transfusion.

Cerebral oxygen saturation (rSO2) during cardiopulmonary bypass (CPB) measured using the INVOS oximeter closely correlates with baseline rSO2

Baseline cerebral regional saturation (rSO₂) measured using the INVOS 5100C (Medtronic, MN, USA) varies widely among patients with cardiac and/or renal diseases. To identify significant correlates of baseline rSO₂ and to investigate intraoperative rSO₂ changes, we conducted a retrospective study in 494 patients undergoing on-pump cardiovascular surgery. Correlations between preoperative blood laboratory test variables and baseline rSO₂ before anesthesia were examined. Intraoperative rSO₂ changes were analyzed. Of all the variables examined, log-transformed B-type natriuretic peptide (BNP) most significantly and negatively correlated with baseline rSO₂ (r = - 0.652, p < 0.0001). Intraoperatively, rSO₂ showed the lowest value during cardiopulmonary bypass (CPB) (median rSO₂: 56.2% during CPB vs. 63.9% at baseline, p < 0.0001). Although rSO₂ during CPB correlated positively with hemoglobin concentration and oxygen delivery during CPB (r = 0.192, p < 0.0001; and r = 0.172, p = 0.0001, respectively), it correlated much more closely with baseline rSO₂ (r = - 0.589, p < 0.0001). Thus, patients showing low baseline rSO₂ primarily associated with preoperatively high BNP continued to show low rSO₂ even during CPB independent of hemodynamics artificially controlled by CPB. Our findings suggest that low baseline rSO₂ in patients with high BNP due to cardiac and/or renal diseases is more likely to result from tissue edema causing alterations in optical pathlength and thus in calculated rSO₂ values, not readily modifiable with CPB, rather than actual cerebral hemodynamic alterations readily modifiable with CPB. These may partly explain why the INVOS oximeter is a trend monitor requiring baseline measures.

Association between Cerebral Oxygenation, as Evaluated with Near-Infrared Spectroscopy, and Cognitive Function in Patients Undergoing Hemodialysis

INTRODUCTION

The prevalence of cognitive impairment in patients undergoing hemodialysis (HD) is higher than that in healthy controls. To date, studies on the association between cognitive function and cerebral oxygenation in these patients are limited. Therefore, in this study, we aimed to cross-sectionally investigate the association between cognitive assessment scores and clinical factors, including cerebral oxygenation, in patients undergoing HD.

METHODS

In this observational study, 193 HD patients were included. Cerebral regional oxygen saturation (rSO2) was monitored using an INVOS 5,100c oxygen saturation monitor. Poor cognition was defined as a Mini-Mental State Examination (MMSE) score ≤23. We analyzed the association between MMSE score and clinical factors, including cerebral rSO2.

RESULTS

MMSE score in HD patients included in this study was 26.8 ± 3.3. There were 164 patients (85%) with MMSE score ≥24 and 29 patients (15%) with an MMSE score ≤23. In the patients with MMSE score ≥24, cerebral rSO2 (53.8% ± 8.3%) was significantly higher than that in patients with MMSE score ≤23 (49.5% ± 9.8%; p = 0.013). Multivariable linear regression analysis was performed using the following confounding factors: age, mean blood pressure, cerebral rSO2, HD duration, ultrafiltration rate, hemoglobin, serum Cr, serum calcium, serum phosphate, total cholesterol, high-density lipoprotein cholesterol levels, serum albumin, presence of diabetes mellitus or chronic glomerulonephritis, history of comorbid cardiovascular or cerebrovascular disease, and use of renin-angiotensin-aldosterone system inhibitors or vitamin D analogs. MMSE score was independently and significantly associated with age (standardized coefficient: -0.244) and cerebral rSO2 (standardized coefficient: 0.180).

CONCLUSIONS

MMSE score was independently associated with age (negative effect) and cerebral rSO2 (positive effect) in this cross-sectional study. Further prospective studies are needed to clarify whether maintaining cerebral oxygenation prevents the deterioration of cognitive function in patients undergoing HD.

Assessment of Endothelial and Microvascular Function in CKD: Older and Newer Techniques, Associated Risk Factors, and Relations with Outcomes

BACKGROUND

Endothelium is the inner cellular lining of the vessels that modulates multiple biological processes including vasomotor tone, permeability, inflammatory responses, hemostasis, and angiogenesis. Endothelial dysfunction, the basis of atherosclerosis, is characterized by an imbalance between endothelium-derived relaxing factors and endothelium-derived contracting factors.

SUMMARY

Starting from the semi-invasive venous occlusion plethysmography, several functional techniques have been developed to evaluate microvascular function and subsequently used in patients with CKD. Flow-mediated dilatation of the forearm is considered to be the "gold standard," while in the last years, novel, noninvasive methods such as laser speckle contrast imaging and near-infrared spectroscopy are scarcely used. Moreover, several circulating biomarkers of endothelial function have been used in studies in CKD patients. This review summarizes available functional methods and biochemical markers for the assessment of endothelial and microvascular function in CKD and discusses existing evidence on their associations with comorbid conditions and outcomes in this population. Key Messages: Accumulated evidence suggests that endothelial dysfunction occurs early in CKD and is associated with target organ damage, progression of renal injury, cardiovascular events, and mortality. Novel methods evaluating microvascular function can offer a detailed, real-time assessment of underlying phenomena and should be increasingly used to shed more light on the role of endothelial dysfunction on cardiovascular and renal disease progression in CKD.

Associations of cerebral oxygenation with hemoglobin levels evaluated by near-infrared spectroscopy in hemodialysis patients

Hemoglobin (Hb) is associated with cerebral oxygenation status owing to its important role of carrying oxygen to systemic tissues. However, data concerning the associations between Hb levels and cerebral regional oxygen saturation (rSO₂) of hemodialysis (HD) patients is limited. We aimed to identify these associations to consider a target Hb level for renal anemia management. This study included 375 HD patients. Cerebral rSO₂ before HD was monitored using the INVOS 5100c oxygen saturation monitor. Multivariable linear regression analysis showed that cerebral rSO₂ was independently associated with natural logarithm (Ln)-HD duration (standardized coefficient: -0.36), mean blood pressure (standardized coefficient: 0.13), pH (standardized coefficient: -0.10), serum albumin (standardized coefficient: 0.14), presence of diabetes mellitus (standardized coefficient: -0.20), and Hb level (standardized coefficient: 0.29). Furthermore, a generalized linear model with restricted cubic spline function was used to investigate the non-linear association between cerebral rSO₂ and Hb levels. In the multivariable analysis for the adjustment with Ln-HD duration, mean blood pressure, pH, serum albumin, and presence of diabetes mellitus, a linear relationship was demonstrated between the two variables (p for linearity = 0.79). Hb levels revealed the positive and significant association with cerebral rSO₂ in this study. Moreover, the relationship between cerebral rSO₂ and Hb level was proven to be linear. Therefore, the target Hb level in renal anemia management would be considered to be the upper limits for the appropriate management of renal anemia by previous guidelines and position statement from the viewpoint of maintaining cerebral oxygenation in HD patients.

Continuous monitoring of changes in cerebral oxygenation during hemodialysis in a patient with acute congestive heart failure

A 71-year-old man undergoing hemodialysis (HD) was admitted to our hospital with congestive heart failure (CHF) and pneumonia. After admission, ultrafiltration with HD was urgently performed because of a lack of respiratory improvement despite the use of noninvasive positive pressure ventilation. During HD, cerebral regional saturation of oxygen (rSO₂) was monitored by INVOS 5100c oxygen saturation monitor (Covidien Japan, Japan) to evaluate changes in tissue oxygenation. At HD initiation, cerebral rSO₂ was very low at 34% under the fraction of inspiratory oxygen (FiO₂) of 0.4. Ultrafiltration was performed at the rate of 0.5 L/h thereafter, cerebral rSO₂ gradually improved even as inhaling oxygen concentration decreased. At the end of HD, cerebral rSO₂ improved at 40% under a FiO₂ of 0.28 as excess body fluid was removed. After pneumonia and CHF improved, he was discharged. Reports of the association between cerebral oxygenation and acute CHF status in patients undergoing HD are limited; therefore, in our experience with this case, cerebral oxygenation deteriorated with the CHF status but was improved by adequate body-fluid management during HD.