Calculated plasma volume status in hemodialysis patients

BACKGROUND

Plasma volume (PV) calculated from hematocrit and body weight has applications in cardiovascular disease. The current study investigated the validity of the calculated PV for predicting volume overload and its prognostic utility in patients undergoing hemodialysis (HD).

PATIENTS AND METHODS

Fifty-four HD patients were prospectively enrolled, and their actual PV (aPV) and relative PV status (PVS) were calculated. Bioelectrical impedance analysis (BIA) with assessment of and total body water (TBW), intracellular water (ICW), extracellular water (ECW), and overhydration (OH) and routine blood examinations were performed before dialysis. A second cohort of 164 HD patients was retrospectively enrolled to evaluate the relationship between the calculated PVS and the outcome, with an endpoint of all-cause mortality.

RESULTS

aPV was significantly associated with TBW, ICW, ECW, OH, and ECW/TBW (all p < 0.001), and most strongly with ECW (r = 0.83). aPV predicted the extent of volume overload with an AUC of 0.770 (p < 0.001), but PVS did not (AUC = 0.617, p = 0.091). Median follow-up time was 53 months, during the course of which 60 (36.58%) patients died. Values for PVS (12.94 ± 10.87% vs. 7.45 ± 5.90%, p = 0.024) and time-averaged PVS (12.83 ± 11.20 vs. 6.78 ± 6.22%, p < 0.001) were significantly increased in patients who died relative to those who survived. A value of time-averaged PVS >8.72% was significantly associated with an increased incidence of all-cause mortality (HR = 2.48, p = 0.0023).

CONCLUSIONS

aPV was most strongly associated with ECW measured using BIA. HD patients with higher time-averaged PVS had a higher rate of all-cause mortality.

Estimated plasma volume status is a simple and quick tool that could help define the severity of patients with infection on arrival at the emergency department

BACKGROUND

Infectious states are subtle and rapidly evolving conditions observed daily in the emergency department (ED), and their prognostic evaluation remains a complex clinical challenge. Recently, estimated plasma volume status (ePVS) has been suggested to have a prognostic role in conditions where volemic alteration is central to the pathophysiology. The aim of this study was to verify whether ePVS recorded at ED admission can provide prognostic indications of 30-day mortality in patients with infection.

METHODS

A prospective observational study was performed between 1 January 2021 and 31 December 2021 at the ED of the Merano Hospital. All patients with infection were enrolled. ePVS values were derived from haemoglobin and haematocrit measured on the immediate arrival of patients in the ED. The predictive power of ePVS for 30-day mortality was assessed using a multivariate model adjusted for severity, comorbidity and urgency. Kaplan-Meier analysis was also performed.

RESULTS

Of the 949 patients with infection enrolled in the study (47.9%, SOFA ≥2), 8.9% (84/949) died at 30 days. The median ePVS value was higher in patients who died at 30 days than in patients who survived (5.83 vs. 4.61, p < 0.001). Multivariate analysis revealed that ePVS in both continuous and categorical form around the median was an independent risk factor for 30-day mortality even after adjusting for severity, comorbidity and urgency. Kaplan-Meier analysis confirmed an increased risk of death in patients with high ePVS values.

CONCLUSIONS

ePVS recorded on ED admission of patients with infection was an independent predictor of risk for 30-day mortality.

Blood-based assessment of oxidative stress, inflammation, endocrine and metabolic adaptations in eventing horses accounting for plasma volume shift after exercise

BACKGROUND

After submaximal exercise, blood values of eventing horses show physiological reactions.

OBJECTIVES

This prospective longitudinal study investigated blood parameters in 20 elite eventing horses before and after two-four-star cross-country rides.

METHODS

Using a mixed model adjusting for plasma volume shift, we assessed exercise-dependent parameters and compared blood values with reference ranges for healthy horses at rest.

RESULTS

Following exercise, cortisol, triiodothyronine (T3) and thyroxine (T4) showed short-term increases, and superoxide-dismutase showed a small short-term increase. Hepatic values showed short-term (haemoglobin [HGB], globulins) or sustained increases (bilirubin, glutamate dehydrogenase, alanine aminotransferase). Digestion-related parameters showed small short-term increases (α-amylase, triglycerides) or decreases (cholesterol, DGGR-lipase), apparent through plasma shift adjustment. Zinc decreased in the short term, and iron showed a delayed decrease. White blood cell count increased persistently after training, whereas serum amyloid A remained unchanged.

CONCLUSIONS

Exercised eventing horses had consistently elevated HGB and cortisol levels 10 and 30 min after submaximal exercise, exceeding the reference ranges for healthy horses at rest. Exercise activates the hypothalamic-pituitary-adrenocortical and hypothalamic-pituitary-thyroid axes. Antioxidant activity was observed. Increased energy requirements led to the mobilization of energy reserves, and a sustained increase in liver enzymes indicated hepatocellular injury. Mild haemolysis suggested increased muscle metabolism, whereas signs of inflammation were subtle. Further research is needed to identify which horses deviate from mean values.

Effects of ingesting beverages containing glycerol and sodium with isomaltulose or sucrose on fluid retention in young adults: a single-blind, randomized crossover trial

We evaluated changes in hyperhydration and beverage hydration index (BHI, a composite measure of fluid balance after consuming a test beverage relative to water) during resting, induced by the consumption of beverages containing glycerol and sodium supplemented with fast-absorbing sucrose or slow-absorbing isomaltulose. In a randomized crossover, single-blinded protocol (clinical trials registry: UMIN000042644), 14 young physically active adults (three women) consumed 1 L of beverage containing either 7% glycerol + 0.5% sodium (Gly + Na), Gly + Na plus 7% sucrose (Gly + Na + Suc), Gly + Na plus 7% isomaltulose (Gly + Na + Iso), or water (CON) over a 40 min period. We assessed the change in plasma volume (ΔPV), BHI (calculated from cumulative urine output following consumption of water relative to that of the beverage), and blood glucose and sodium for 180 min after initiating ingestion. Total urine volume was reduced in all beverages containing glycerol and sodium compared to CON (all P ≤ 0.002). The addition of isomaltulose increased BHI by ∼45% (3.43 ± 1.0 vs. 2.50 ± 0.7 for Gly + Na, P = 0.011) whereas sucrose did not (2.6 ± 0.6, P = 0.826). The PV expansion was earliest for Gly + Na (30 min), slower for Gly + Na + Suc (90 min), and slowest for Gly + Na + Iso (120 min) with a concomitant lag in the increase of blood glucose and sodium concentrations. Supplementation of beverages containing glycerol and sodium with isomaltulose but not sucrose enhances BHI from those of glycerol and sodium only under a resting state, likely due to the slow absorption of isomaltulose-derived monosaccharides (i.e., glucose and fructose).

Predictive value of estimated plasma volume for postoperative hypotension in percutaneous intramyocardial septal radiofrequency ablation treating for hypertrophic obstructive cardiomyopathy

BACKGROUND

Estimated plasma volume status (ePVS) estimated by the Duarte formula is associated with clinical outcomes in patients with heart failure. It remains unclear the predictive value of the ePVS to the postoperative hypotension (POH) in percutaneous intramyocardial septal radiofrequency ablation (PIMSRA) treating hypertrophic obstructive cardiomyopathy (HOCM).

METHODS

Data of HOCM patients who underwent PIMSRA were retrospectively collected. Preoperative ePVS was calculated using the Duarte formulas which derived from hemoglobin and hematocrit ratios. Clinical variables including physical assessment, biological and echocardiographic parameters were recorded. Patients were labeled with or without POH according to the medical record in the hospital. Univariable and multivariable logistic regression were performed to evaluate the association between ePVS and POH. Using different thresholds derived from quartiles and the best cutoff value of the receiver operating characteristic curve, the diagnostic performance of ePVS was quantified.

RESULTS

Among the 405 patients included in this study, 53 (13.1%) patients were observed with symptomatic POH. Median (IQR) of ePVS in overall patients was 3.77 (3.27~4.40) mL/g and in patients with POH were higher than those without POH. The ePVS was associated with POH, with the odds ratio of 1.669 (95% CI 1.299 ~ 2.144) per mL/g. After adjusted by potential confounders, ePVS remained independently associated with POH, with the approximate odds ratio in different models.

CONCLUSION

The preoperative ePVS derived from the Duarte formulas was independently associated with postoperative hypotension in HOCM patients who underwent PIMSRA and showed prognostic value to the risk stratification of postoperative management.

TRIAL REGISTRATION

NCT06003478 (22/08/2023).

Exercise induced plasma volume expansion lowers cardiovascular strain during 15-km cycling time-trial in acute normobaric hypoxia

The purpose of our study was to assess the influence of a single high-intensity interval exercise (HIIE) bout in normoxia on plasma volume (PV) and consequent cycling performance in normobaric hypoxia (0.15 FiO2, simulating ~2,500 m). Eight males (VO2peak: 48.8 ± 3.4 mL/kg/min, 24.0 ± 1.6 years) completed a hypoxic 15 km cycling time trial (TT), followed by a crossover intervention of either HIIE (8x4 min cycling bouts at 85% of VO2peak) or CON (matched kJ production from HIIE at 50% of VO2peak). 48 hours post intervention, an identical TT was performed. Cardiovascular parameters were measured via impedance cardiography during each TT. Changes in PV was measured 24 and 48 hours post HIIE and CON. HIIE increased PV at 24 (4.1 ± 3.9%, P = 0.031) and 48 (6.7 ± 1.7, P = 0.006) hours post, while no difference was observed following the CON (1.3 ± 1.1% and 0.3 ± 2.8%). The higher PV led to an increased stroke volume (P = 0.03) and cardiac output (P = 0.02) during the hypoxic TT, while heart rate was not changed (P = 0.49). We observed no changes in time to completion (-0.63 ± 0.57 min, P = 0.054) and power output (7.37 ± 7.98 W, P = 0.078) between TTs. In the absence of environmental stress, a single bout of HIIE was an effective strategy to increase PV and reduce the cardiovascular strain during a cycling TT at moderate simulated altitude but did not impact hypoxic exercise performance. Trial registration: Clinical Trials ID: NCT05800808.

Evidence of serial connection between the plasma volume and two interstitial fluid compartments

BACKGROUND

Kinetic analysis of fluid volume shifts can identify two interstitial fluid compartments with different turnover rates, but how they are connected to the bloodstream is unknown.

METHODS

Retrospective data were retrieved from 217 experiments where 1.5 L of Ringer's solution (mean) had been administered by intravenous infusion over 30 min to awake and anesthetized humans (mean age 40 years). Urinary excretion and hemoglobin-derived plasma dilution served as input variables in a volume kinetic analysis using mixed models software. Possible modes of connection between the two interstitial fluid compartments and the bloodstream were judged by covariance analysis between kinetic rate constants, physiological variables, and time factors.

RESULTS

The return flow of already distributed fluid to the plasma via a fast-exchange interstitial compartment was inhibited ongoing infusion of fluid (-38 %), which was probably due to increase of the venous pressure during volume loading. Ongoing infusion also greatly retarded the entrance of fluid to the slow-exchange compartment (-85 %), which suggests that infused Ringer's first had to enter the fast-exchange compartment. A high mean arterial pressure markedly increased the urine output and, to a lesser degree, also the rate of entrance of fluid to the fast-exchange compartment. Moreover, a high blood hemoglobin concentration retarded the rate of entrance of fluid to the fast-exchange compartment.

CONCLUSIONS

The fast-exchange but not the slow-exchange interstitial fluid compartment was affected by intravascular events, which suggests that only the fast-exchange compartment is directly connected to the circulating blood.

Estimated plasma volume status in COVID-19 patients and its relation to comorbidities and clinical outcomes

Blood plasma is a large reservoir of circulating mediators of inflammation and its expansion has been associated with unfavorable outcomes in patients with inflammatory and cardiovascular diseases. The aim of this study was to determine clinical and prognostic value of estimated plasma volume status (ePVS) in hospitalized patients with COVID-19. We retrospectively investigated 5871 consecutive COVID-19 patient hospitalized in our tertiary-level institution in period 3/2020-6/2021. ePVS was determined using the Strauss-derived Duarte formula and was correlated with clinical characteristics and unwanted outcomes. Median ePVS was 4.77 dl/g with interquartile range 4.11-5.74. Higher ePVS was significantly associated with older age, female sex, higher comorbidity burden, worse functional status, less severe COVID-19 clinical presentation with lower severity and longer duration of symptoms, but more pronounced inflammatory profile with higher C-reactive protein, interleukin-6 and D-dimer levels (P < 0.05 for all analyses). In the multivariate regression analysis U shaped relationship of ePVS with mortality was revealed, present independently of age, sex, COVID-19 severity and comorbidity burden. In addition, higher ePVS was independently associated with higher tendency for mechanical ventilation, intensive care unit treatment, venous thromboembolism, major bleeding and bacteriemia and lower ePVS was independently associated with tendency for arterial thrombotic events. Higher ePVS, indicative of plasma volume expansion and inflammatory cytokine accumulation, may predispose respiratory deterioration and venous thromboembolism, despite less severe initial clinical presentation. Lower ePVS, indicative of hemoconcentration, may predispose arterial thrombotic events. Both may be associated with higher mortality in hospitalized COVID-19 patients.

Intravascular volumes and the influence on anemia assessed by a carbon monoxide rebreathing method in patients undergoing maintenance hemodialysis

INTRODUCTION

Fluid overload is a major challenge in hemodialysis patients and might cause hypervolemia. We speculated that hemodialysis patients reaching dry weight could have undetected hypervolemia and low hemoglobin (Hb) concentration (g/dL) due to hemodilution.

METHODS

The study included hemodialysis patients (n = 22) and matched healthy controls (n = 22). Blood volume, plasma volume, red blood cell volume, and total Hb mass were determined using a carbon monoxide (CO)-rebreathing method in hemodialysis patients reaching dry weight and controls. Blood volume measurements were also obtained by a dual-isotope labeling technique in a subgroup for validation purposes.

FINDINGS

In the hemodialysis group, the median specific blood volume was 89.3 mL/kg (interquartile range [IQR]: 76.7-95.4 mL/kg) and was higher than in the control group (79.9 mL/kg [IQR: 70.4-88.0 mL/kg]; p < 0.037). The median specific plasma volume was 54.7 mL/kg (IQR: 47.1-61.0 mL/kg) and 44.0 mL/kg (IQR: 38.7-49.5 mL/kg) in the hemodialysis and control groups, respectively (p < 0.001). Hb concentration was lower in hemodialysis patients (p < 0.001), whereas no difference in total Hb mass was observed between groups (p = 0.11). A correlation was found between blood volume measured by the CO-rebreathing test and the dual-isotope labeling technique in the control group (r = 0.83, p = 0.015), but not the hemodialysis group (r = 0.25, p = 0.60).

DISCUSSION

The hemodialysis group had increased specific blood volume at dry weight due to high plasma volume, suggesting a hypervolemic state. However, correlation was not established against the dual-isotope labeling technique underlining that the precision of the CO-rebreathing test should be further validated. The total Hb mass was similar between hemodialysis patients and controls, unlike Hb concentration, which emphasizes that Hb concentration is an inaccurate marker of anemia among hemodialysis patients.

Plasma Volume Oscillations during Fluid Therapy in Humans

INTRODUCTION

Oscillations are frequently observed on plasma dilution curves during intravenous fluid therapy. This study aimed to examine how common these oscillations are and what they represent.

METHODS

Fourier transforms were used to analyze the residuals obtained during fitting of a volume kinetic model to 269 plasma dilution curves. Oscillating patterns were identified in two-thirds of the fluid infusion experiments.

RESULTS

The wave frequency usually had a dominating frequency of 1 h or multiples thereof. The wave amplitudes varied between 1% and 4% of the plasma volume. The "peak-to-peak" amplitudes were then twice as large, which corresponded to blood volume changes of 60-240 mL. A population kinetic analysis of the distribution of infused fluid between body fluid compartments was then applied to search for clues that could explain the oscillations. This analysis showed that amplitudes >1.5% were associated with doubled turnover of fluid in a fast-exchange interstitial fluid compartment and, together with data on plasma albumin, suggested that oscillations might represent bursts of efferent lymph.

CONCLUSIONS

Oscillations with very low frequency were often observed on plasma dilution-time curves obtained during fluid therapy. They were associated with fast turnover of interstitial fluid and can possibly have resulted from accelerated lymphatic flow.

Association of plasma volume status with outcomes in hospitalized Covid-19 ARDS patients: A retrospective multicenter observational study

PURPOSE

To evaluate the association of estimated plasma volume (ePV) and plasma volume status (PVS) on admission with the outcomes in COVID-19-related acute respiratory distress syndrome (ARDS) patients.

MATERIALS AND METHODS

We performed a retrospective multi-center study on COVID-19-related ARDS patients who were admitted to the Mayo Clinic Enterprise health system. Plasma volume was calculated using the formulae for ePV and PVS, and these variables were analyzed for correlation with patient outcomes.

RESULTS

Our analysis included 1298 patients with sequential organ failure assessment (SOFA) respiratory score ≥ 2 (PaO2/FIO2 ≤300 mmHg) and a mortality rate of 25.96%. A Cox proportional multivariate analysis showed PVS but not ePV as an independent correlation with 90-day mortality after adjusting for the covariates (HR: 1.015, 95% CI: 1.005-1.025, p = 0.002 and HR 1.054, 95% CI 0.958-1.159, p = 0.278 respectively).

CONCLUSION

A lower PVS on admission correlated with a greater chance of survival in COVID-19-related ARDS patients. The role of PVS in guiding fluid management should be investigated in future prospective studies.

Estimated plasma volume is not a robust indicator of the severity of congestion in patients with heart failure

BACKGROUND

Congestion is the main cause of morbidity and a prime determinant of survival in patients with heart failure (HF). However, the assessment of congestion is subjective and estimation of plasma volume (ePV) has been suggested as a more objective measure of congestion. This study aimed to explore the relationships and interactions between ePV, the severity of congestion and survival using a nationwide registry.

METHODS

Of the 1054 patients with HF enrolled in the registry, 769 had sufficient data to calculate ePV (using the Duarte, Kaplan, and Hakim equations) and relative plasma volume status (rPVS), and these patients were subsequently included in the present analysis. The severity of congestion was assessed using a 6-point congestion score (CS). Patients were divided into three groups according to the degree of congestion.

RESULTS

Out of four equations tested, only ePVDuarte and rPVS were statistically higher in patients with severe congestion as compared to patients with no congestion (p<0.001 for both). Both ePVDuarte (r = 0.197, p<0.001) and rPVS (r = 0.153, p<0.001) showed statistically significant correlations with CS and both had a modest accuracy (70.4% for ePVDuarte and 69.4% for rPVS) to predict a CS ≥3. After a median follow up of 496 days, both ePVDuarte (OR:1.14,95%CI:1.03-1.26, p = 0.01) and rPVS (OR:1.02, 95%CI:1.00-1.03, p = 0.03) were associated with all-cause mortality after adjusting for demographic and clinical variables. However, none of the indices were associated with mortality following the introduction of CS to the models (p>0.05 for both).

CONCLUSIONS

Elevated ePVDuarte and rPVS were indicators of congestion but with a limited robustness, and either parameter could be clinically useful when a comprehensive clinical evaluation of congestion is not feasible.

Estimated plasma volume status adds prognostic value to hemodynamic parameters in advanced heart failure

BACKGROUND

Estimated plasma volume status (ePVS) is a marker of intravascular congestion and has prognostic value in patients with heart failure (HF). The elevation of intracardiac filling pressures is defined as hemodynamic congestion and is also associated with poor prognosis. However, the relationship between intravascular congestion and hemodynamic congestion remains unclear. This study sought to explore the correlation between ePVS and hemodynamic parameters and determine the association between ePVS and clinical outcomes in patients with advanced HF.

METHODS

Patients with advanced HF underwent right heart catheterization (RHC) for hemodynamic profiles. The sum of right atrial pressure (RAP) and pulmonary arterial wedge pressure (PAWP) > 30 mmHg was considered to present with hemodynamic congestion. Blood tests were conducted within 24 h of RHC. We calculated ePVS using the Strauss-derived Duarte formula. The primary outcome was all-cause mortality.

RESULTS

A total of 195 patients were divided into two groups based on the cut-off value of ePVS (4.08 dL/g) calculated from receiver operating characteristic analysis. Patients with ePVS > 4.08 dL/g were more likely to present with wet rales (21.2% vs. 9.9%, P = 0.032) and had a higher risk of death (HR 4.748, 95% CI 2.385-9.453), regardless of whether RAP + PAWP was normal or elevated (all P < 0.05). Hemodynamic parameters and ePVS were not correlated (all P > 0.05). High ePVS significantly improved the predictive value beyond the clinical plus hemodynamic prognostic model (area under the curve of 0.844, Delong test, P = 0.024).

CONCLUSION

ePVS could additionally add prognostic value to hemodynamic parameters in advanced heart failure, although not correlated with hemodynamic parameters.

The effects of empagliflozin on measured glomerular filtration rate and estimated extracellular and plasma volumes in patients with type 2 diabetes

AIMS

To investigate the effects of empagliflozin on measured glomerular filtration rate (mGFR), estimated plasma volume (PV) and estimated extracellular volume (ECV) in a cohort of patients with type 2 diabetes (T2D) and high risk of cardiovascular events.

MATERIALS AND METHODS

In this prespecified substudy of the randomized, placebo-controlled SIMPLE trial, patients with T2D at high risk of cardiovascular events were allocated to either empagliflozin 25 mg or placebo once daily for 13 weeks. The prespecified outcome was between-group change in mGFR, measured by the 51 Cr-EDTA method after 13 weeks; changes in estimated PV and estimated ECV were included.

RESULTS

From April 4, 2017 to May 11, 2020, 91 participants were randomized. Of these, 45 patients from the empagliflozin group and 45 patients from the placebo group were included in the intention-to-treat analysis. Treatment with empagliflozin reduced mGFR by -7.9 mL/min (95% confidence interval [CI] -11.1 to -4.7; P < 0.001), estimated ECV by -192.5 mL (95% CI -318.0 to -66.9; P = 0.003) and estimated PV by -128.9 mL (95% CI -218.0 to 39.8; P = 0.005) at Week 13.

CONCLUSIONS

Treatment with empagliflozin for 13 weeks reduced mGFR, estimated ECV and estimated PV in patients with T2D and high risk of cardiovascular events.

Prediction of plasma volume and total hemoglobin mass with machine learning

Hemoglobin concentration ([Hb]) is used for the clinical diagnosis of anemia, and in sports as a marker of blood doping. [Hb] is however subject to significant variations mainly due to shifts in plasma volume (PV). This study proposes a newly developed model able to accurately predict total hemoglobin mass (Hbmass) and PV from a single complete blood count (CBC) and anthropometric variables in healthy subject. Seven hundred and sixty-nine CBC coupled to measures of Hbmass and PV using a CO-rebreathing method were used with a machine learning tool to calculate an estimation model. The predictive model resulted in a root mean square error of 33.2 g and 35.6 g for Hbmass, and 179 mL and 244 mL for PV, in women and men, respectively. Measured and predicted data were significantly correlated (p < 0.001) with a coefficient of determination (R2 ) ranging from 0.76 to 0.90 for Hbmass and PV, in both women and men. The Bland-Altman bias was on average 0.23 for Hbmass and 4.15 for PV. We herewith present a model with a robust prediction potential for Hbmass and PV. Such model would be relevant in providing complementary data in contexts such as the epidemiology of anemia or the individual monitoring of [Hb] in anti-doping.

Longitudinal haematological responses to training load and heat acclimation preceding a male team pursuit cycling world record

This study evaluated relationships between changes in training load, haematological responses, and endurance exercise performance during temperate and heat acclimation (HA) training preceding a male team cycling pursuit world record (WR). Haemoglobin mass (Hbmass) and concentration ([Hb]), plasma volume (PV) and blood volume (BV) were assessed in nine male track endurance cyclists (∼3 occasions per month) training in temperate conditions (247-142 days prior to the WR) to establish responses to differing acute (ATL) and chronic (CTL) training loads. Testing was performed again pre- and post-HA (22-28 days prior to the WR). Endurance performance (V̇O₂max, 4MMP, lactate threshold 1 and 2) was assessed on three occasions (238-231, 189-182 and 133-126 days prior to the WR). In temperate conditions, CTL was associated with Hbmass (B = 0.62, P = 0.02), PV (B = 4.49, P = 0.01) and BV (B = 6.51, P = 0.04) but not [Hb] (B = -0.01, P = 0.17). ATL was associated with PV (B = 2.28, P < 0.01), BV (B = 2.63, P = 0.04) and [Hb] (B = -0.01, P = 0.04) but not Hbmass (B = 0.10, P = 0.41). During HA, PV increased 8.2% (P < 0.01), while Hbmass, CTL and ATL were unchanged. Hbmass and [Hb] were associated with all performance outcomes (P < 0.05), except V̇O2max. PV and BV were not associated with performance outcomes. During temperate training, changes in Hbmass were most strongly associated with changes in CTL. Both CTL and ATL were associated with changes in PV, but HA was associated with increased PV and maintenance of Hbmass without increasing ATL or CTL. In practical terms, maintaining high CTL and high Hbmass might be beneficial for improving endurance performance.HIGHLIGHTSChanges in haemoglobin mass were associated with endurance exercise performance and changes in chronic training load in temperate conditions.Heat acclimation increased plasma volume and maintained haemoglobin mass independently of chronic training load.Chronic training loads and haemoglobin mass should be increased to improve endurance exercise performance.Heat acclimation may optimise haematological adaptations when training load is reduced.

Impact of estimated plasma volume status on clinical outcomes in patients with lower extremity artery disease who underwent endovascular therapy

Lower extremity artery disease (LEAD) is an arterial occlusive disease associated with high morbidity and mortality. Estimated plasma volume status (ePVS), a marker of plasma volume expansion and contraction, is gaining attention in the field of cardiovascular diseases. However, the impact of ePVS on the clinical outcomes of patients with LEAD remains unclear. We calculated ePVS using two different formulas, Kaplan-Hakim (KH-ePVS) and Duarte (D-ePVS), in 288 patients (mean age, 73 years; 77% male) with LEAD who underwent the first endovascular therapy (EVT), and prospectively followed them up between 2014 and 2019. All patients were divided into two groups based on the median ePVS values. The primary endpoints were composite events, including all-cause death and major adverse limb events (death/MALE). The median follow-up duration was 672 days. There were 183, 40 and 65 patients in Fontaine classes II, III, and IV, respectively. The median KH-ePVS and D-ePVS was 5.96 and 5.09, respectively. The ePVS significantly increased with advancing Fontaine classes. Kaplan-Meier analysis demonstrated that the high ePVS group had higher rates of death/MALE than the low ePVS group. Multivariate Cox proportional hazard analysis revealed that each ePVS was an independent predictor for death/MALE after adjusting for confounding risk factors. The prognostic ability for death/MALE was significantly improved by adding ePVS to the basic predictors. ePVS was associated with LEAD severity and clinical outcomes, suggesting that ePVS could be an additional risk factor for death/MALE in patients with LEAD who underwent EVT. We demonstrated that the association between ePVS and the clinical outcomes of patients with LEAD. The prognostic ability for death/MALE was significantly improved by adding ePVS to the basic predictors. LEAD lower extremity artery disease, MALE major adverse limb events, PVS plasma volume status.

Individuals with hypertension have lower plasma volume regardless of weight status

Increased plasma volume is often reported as a cause or symptom of hypertension in individuals with obesity. However, these individuals are often compared to normal weight normotensive individuals. Since higher plasma volumes have been reported in larger individuals, it is possible that plasma volume is actually lower in obese hypertensive individuals compared to normotensive obese individuals. This may be important for better understanding the clinical manifestation of hypertension between weight categories. National Health and Nutritional Examination Survey (cycles 1999-2018) data were used to examine the relationship between plasma (derived from the Straus formula), blood pressure (measured with an automated device) and body mass index. We observed an inverse relationship between estimated plasma volume and systolic (B = -1.68 (95% CI: -2.06, -1.30) mmHg), p < 0.0001), diastolic (B = -3.35 (95% CI: -3.61, -3.08) mmHg) p < 0.0001), and mean arterial pressure (B = -2.79 (95% CI: -3.05, -2.53) mmHg) p < 0.0001). The relationship between estimated plasma volume and diastolic blood pressure (interaction term: B = -0.069 (-0.10, -0.03), p < 0.0001) did depend on BMI. The "normal weight" group had the lowest slope and this slope was significantly different from the "obese" (B = -1.47 (95% CI: -1.88, -1.07)) and "overweight" (B = -1.11 (-1.55, -0.67)) groups. Plasma volume is lower in hypertensive individuals regardless of weight status, but this relationship is more pronounced among obese individuals.

Factors Regulating Fluid Restitution and Plasma Volume Reduction over the Course of Hemodialysis

Over the course of hemodialysis, fluid and protein are restituted from the tissue compartment to the circulation compartment through the endothelia. Our previous model analysis on fluid and protein transport during hemodialysis is expanded to account for changes occurring in the tissue. The measured initial and end plasma protein concentration (PPC, Cp and Cp') for six hemodialysis studies are analyzed by this expanded model. The computation results indicate that the total driving pressure to restitute fluid from the tissue to the circulation ranges from 5.4 to 20.3 mmHg. The analysis identifies that the increase in plasma colloidal osmotic pressure (COP) contributes 78 ± 6% of the total driving pressure, the decrease in microvascular blood pressure 32 ± 4%, the increase in the COP of interstitial fluid -6 ± 3%, and the decrease in interstitial fluid pressure -5 ± 2%. Let this ratio (Cp' - Cp)/Cp' be termed the PPC increment. The six HDs can be divided into three groups which are to have these PPC increments 25.7%, 14.5 ± 2.6(SD)% and 8.3%. It is calculated that their correspondent filtration coefficients are 0.43, 1.29 ± 0.28 and 5.93 mL/min/mmHg and the relative reductions in plasma volume (RRPV) -22.1%, -13.1 ± 6% and -9.4%. The large variations in PPC increments and RRPV show the filtration coefficient is a key factor to regulate the hemodialysis process.

Prognostic Value of Estimated Plasma Volume Status in Patients With Sepsis

BACKGROUND

In patients with sepsis, timely risk stratification is important to improve prognosis. Although several clinical scoring systems are currently being used to predict the outcome of sepsis, but they all have certain limitations. The objective of this study was to evaluate the prognostic value of estimated plasma volume status (ePVS) in patients admitted to the intensive care unit (ICU) with sepsis or septic shock.

METHODS

This single-center, prospective observational study, included 100 patients admitted to the ICU with sepsis or septic shock. Informed consent, blood samples, and co-morbidity data were obtained from the patients on admission, and the severity of sepsis was recorded. The primary outcome was in-hospital mortality and multivariable logistic regression analysis was used to adjust for confounding factors to determine the significant prognostic factor.

RESULTS

The in-hospital mortality was 47%. The ePVS was correlated with the amount of total fluids administered 24 hours before the ICU admission. The mean ePVS in patients who died was higher than in those who survived (7.7 ± 2.1 dL/g vs. 6.6 ± 1.6 dL/g, P = 0.003). To evaluate the utility of ePVS in predicting in-hospital mortality, a receiver operating characteristic curve was produced. Sensitivity and specificity were optimal at a cut-off point of 7.09 dL/g, with an area under the curve of 0.655. In the multivariate analysis, higher ePVS was significantly associated with higher in-hospital mortality (adjusted odds ratio, 1.39; 95% confidence interval, 1.04-1.85, P = 0.028). The Kaplan-Meier curve showed that an ePVS value above 7.09 was associated with an increased risk of in-hospital mortality compared with the rest of the population (P = 0.004).

CONCLUSION

The ePVS was correlated with the amount of intravenous fluid resuscitation and may be used as a simple and novel prognostic factor in patients with sepsis or septic shock who are admitted to the ICU.

Effects of luseogliflozin on estimated plasma volume in patients with heart failure with preserved ejection fraction

AIMS

Sodium glucose co-transporter 2 inhibitors have diuretic effects in both patients with glycosuria and with natriuresis. We sought to assess the effect of luseogliflozin on estimated plasma volume (ePV) in patients with type 2 diabetes and heart failure with preserved ejection fraction (HFpEF).

METHODS AND RESULTS

This study was a post-hoc analysis of the MUSCAT-HF trial (UMIN000018395), a multicentre, prospective, open-label, randomized controlled trial that assessed the effect of 12 weeks of luseogliflozin (2.5 mg, once daily, n = 83) as compared with voglibose (0.2 mg, three times daily, n = 82) on the reduction in brain natriuretic peptide (BNP) in patients with type 2 diabetes and HFpEF. The analysis compared the change in ePV calculated by the Straus formula from baseline to Weeks 4, 12, and 24, using a mixed-effects model for repeated measures. We also estimated the association between changes in ePV and changes in other clinical parameters, including BNP levels. Luseogliflozin significantly reduced ePV as compared to voglibose at Week 4 {adjusted mean group-difference -6.43% [95% confidence interval (CI): -9.11 to -3.74]}, at Week 12 [-8.73% (95%CI: -11.40 to -6.05)], and at Week 24 [-11.02% (95%CI: -13.71 to -8.33)]. The effect of luseogliflozin on these parameters was mostly consistent across various patient clinical characteristics. The change in ePV at Week 12 was significantly associated with log-transformed BNP (r = 0.197, P = 0.015) and left atrial volume index (r = 0.283, P = 0.019).

CONCLUSIONS

Luseogliflozin significantly reduced ePV in patients with type 2 diabetes and HFpEF, as compared with voglibose. The reduction of intravascular volume by luseogliflozin may provide clinical benefits to patients with type 2 diabetes and HFpEF.

Effects of 150- and 450-mL Acute Blood Losses on Maximal Oxygen Uptake and Exercise Capacity

PURPOSE

This study investigated whether maximal oxygen uptake (V˙O2max) and exercise capacity are affected by small acute blood loss (150 mL) and elucidated compensatory mechanisms.

METHODS

Thirteen male subjects (V˙O2max, 63 ± 9 mL·kg-1·min-1; mean ± SD) performed incremental exercise to exhaustion on a cycle ergometer in three experimental conditions: in euvolemia (control; blood volume [BV], 6.0 ± 0.7 L) and immediately after acute BV reductions of 150 mL (BVR150mL) and 450 mL (BVR450mL). Changes in plasma volume (PV) and BV during exercise were calculated from hematocrit, hemoglobin concentration, and hemoglobin mass (carbon monoxide rebreathing).

RESULTS

The reduction in V˙O2max per milliliter of BVR was 2.5-fold larger after BVR450mL compared with BVR150mL (-0.7 ± 0.3 vs -0.3 ± 0.6 mL·min-1·mL-1, P = 0.029). V˙O2max was not significantly changed after BVR150mL (-1% ± 2%, P = 0.124) but reduced by 7% ± 3% after BVR450mL (P < 0.001) compared with control. Peak power output only decreased after BVR450mL (P < 0.001). At maximal exercise, BV was restored after BVR150mL compared with control (-50 ± 185 mL, P = 0.375) attributed to PV restoration, which was, however, insufficient in restoring BV after BVR450mL (-281 ± 184 mL, P < 0.001). The peak heart rate tended to increase (3 ± 5 bpm, P = 0.062), whereas the O2 pulse (-2 ± 1 mL per beat, P < 0.001) and vastus lateralis tissue oxygenation index (-4% ± 8% points, P = 0.080) were reduced after BVR450mL, suggesting decreased stroke volume and increased leg O2 extraction.

CONCLUSION

The deteriorations of V˙O2max and of maximal exercise capacity accelerate with the magnitude of acute blood loss, likely because of a rapid PV restoration sufficient to establish euvolemia after a small but not after a moderate blood loss.

Association of estimated plasma volume and weight loss after long-term administration and subsequent discontinuation of the sodium-glucose cotransporter-2 inhibitor tofogliflozin

Sodium-glucose cotransporter-2 inhibitors (SGLT2) are drugs that have been reported to have several effects through the regulation of plasma volume, for example, antihypertensive effects. This study aimed to clarify the impact of long-term administration and subsequent discontinuation of the SGLT2 inhibitor tofogliflozin on estimated plasma volume (ePV), brain natriuretic peptide (BNP) and the relationship between changes in ePV, BNP and body weight (BW). Data from 157 participants with type 2 diabetes receiving tofogliflozin monotherapy in a phase 3 study were analysed. Changes in variables or correlations among them during a 52-week administration and a 2-week post-treatment period were investigated. Percent change in ePV was calculated using the Strauss formula. Significant decreases in BW, ePV and ln-transformed BNP (ln-BNP) were noted by week 52. %ΔBW was not significantly correlated with %ΔePV and Δln-BNP, while %ΔePV was significantly correlated with Δln-BNP. Two weeks after discontinuation of tofogliflozin, BW, ePV and ln-BNP were significantly increased. %ΔBW was significantly correlated with %ΔePV and Δln-BNP. Furthermore, ePV and BNP were significantly higher than baseline levels.

The Effect of Medium-Term Sauna-Based Heat Acclimation (MPHA) on Thermophysiological and Plasma Volume Responses to Exercise Performed under Temperate Conditions in Elite Cross-Country Skiers

The influence of a series of ten sauna baths (MPHA) on thermophysiological and selected hematological responses in 14 elite cross-country skiers to a submaximal endurance exercise test performed under thermoneutral environmental conditions was studied. Thermal and physiological variables were measured before and after the exercise test, whereas selected hematological indices were studied before, immediately after, and during recovery after a run, before (T1) and after sauna baths (T2). MPHA did not influence the baseline internal, body, and skin temperatures. There was a decrease in the resting heart rate (HR: p = 0.001) and physiological strain (PSI: p = 0.052) after MPHA and a significant effect of MPHA on systolic blood pressure (p = 0.03), hematological indices, and an exercise effect but no combined effect of treatments and exercise on the tested variables. A positive correlation was reported between PSI and total protein (%ΔTP) in T2 and a negative between plasma volume (%ΔPV) and mean red cellular volume (%ΔMCV) in T1 and T2 in response to exercise and a positive one during recovery. This may suggest that MPHA has a weak influence on body temperatures but causes a moderate decrease in PSI and modifications of plasma volume restoration in response to exercise under temperate conditions in elite athletes.

Effect of exercise training in rats exposed to chronic hypoxia: Application for Monge's disease

Physical exercise may improve hematological conditions in high altitude dwellers suffering from Chronic Mountain Sickness (CMS), in reducing hemoglobin concentration. Therefore, the present study aimed to characterize the effects of 1-month exercise training session in a model of rats exposed to chronic hypoxia. Four groups of male rats were studied: normoxic sedentary (NS, n = 8), normoxic training (NT, n = 8), hypoxic sedentary (HS, n = 8), and hypoxic training group (HT, n = 8). Hypoxic groups were exposed to hypobaric hypoxia for one month (PB =433 Torr). Training intensity was progressively increased from a running speed of 10.4 to 17.8 m/min. Chronic hypoxia led to an increase in hematocrit (HCT) associated with a decrease in plasma volume despite an increase in water intake. Training led to a reduction in HCT (p < 0.01), with a non-significant increase in plasma volume and weight gain. Hypoxia and training had inhibitory effects on haptoglobin (NS group: 379 ± 92; HT: 239 ± 34 µg/ml, p < 0.01). Chronic hypoxia and exercise training increased SpO2 measured after acute hypoxic exposure. Training blunted the decrease in V ˙ O2 peak, time of exhaustion, and maximum speed associated with chronic exposure to hypoxia. Chronic hypoxia led to a right ventricular hypertrophy, which was not corrected by 1-month exercise training. Altogether, by decreasing hematocrit, reducing body weight, and limiting performance decrease, training in hypoxia may have a beneficial effect on excessive erythropoiesis in chronic hypoxia. Therefore, regular exercise training might be beneficial to avoid worsening of CMS symptoms in high altitude dwellers and to improve their quality of life.

Quantification of steroid hormones in low volume plasma and tissue homogenates of fish using LC-MS/MS

Quantification of steroid hormones in fish is an important step for toxicology and endocrinology studies. Among the hormone analysis techniques, liquid chromatography tandem mass spectrometry (LC-MS/MS) has widely been used for measuring hormones in various biological samples. Despite all improvements in the technique, detection of several hormones in a low volume of serum or plasma is still challenging. We developed a robust method for simultaneous quantification of 14 steroid hormones including corticosterone, cortisol, 11-ketotestosterone, progesterone, testosterone, 17OH-progesterone, aldosterone, dihydrotestosterone, estrone, 17β-estradiol, estriol, ethinylestradiol, levonorgestrel and equilin from volumes as low as 10 µL serum or plasma in a short run by LC-MS/MS. The lowest limit of detection in 10 µL serum was 0.012 ng/mL measured for cortisol, progesterone, testosterone, 17OH-progesterone and estrone. Use of high (25 times more) serum volume improved detection limit of hormones by 2-40 times. The method was compared with the radioimmunoassay technique in which testosterone and 17β-estradiol were highly correlated with R² of 0.95 and 0.96, respectively. We validated the method by measuring four selected hormones, in low and high plasma volumes of largemouth bass (Micropterus salmoides). In addition, we developed a method to quantify hormones in whole body fish homogenates of small fish and compared the values to plasma concentrations, using fathead minnow (Pimephales promelas). Calculated concentrations of the hormones in plasma were consistent with those in the homogenate and 11-ketotestosterone and 17β-estradiol were significantly different in males and females. The ability to measure hormones from whole body homogenates was further evaluated in two model small fish species, zebrafish (Danio rerio) and juvenile silverside (Menidia beryllina). These results suggest that whole tissue homogenate is a reliable alternative for hormone quantification when sufficient plasma is not available.

Plasma volume, cell volume, total blood volume and F factor in the tree shrew

In this study, the physiological values of volumes of plasma, cells, total blood and the F blood factors were identified in 24 adult tree shrews (Tupaia belangeri; 12 male and 12 female; average BW of 123.9±19.19 g). The two-compartment model method of Evans Blue dye was used to obtain the plasma volume and the venous hematocrit was measured by microhematocrit method. To establish the relationship between body weight (BW) and blood volume of tree shrews, We performed linear fitting for these two datasets. Results were analyzed according to gender and weight (<120g vs.>120g). Statistical significance was assessed using the unpaired student t test and one-way ANOVA. The average volumes per 100g body weight of plasma, red blood cell (RBC) and total blood were 5.42±0.543, 3.24±0.445, and 8.66±0.680ml respectively. The mean body hematocrit, cardiac hematocrit, jugular vein hematocrit, femoral vein hematocrit, and tail vein hematocrit was 37.43±4.096, 39.72±3.219, 43.04±4.717, 40.84±3.041, and 38.71±3.442% respectively. The F cardiac was 0.94±0.072, F jugular vein 0.88±0.118, F femoral vein 0.92±0.111, and the F tail vein 0.97±0.117. Blood volume (ml) was 85.89103×BW (kg). This is the first study to provide the parameters of plasma volume, cell volume, total blood volume and F factor and a baseline for future research on blood physiology of tree shrews.

Plasma volume variation across the menstrual cycle among healthy women of reproductive age: A prospective cohort study

Increases in reproductive hormones like estrogen, play an important role in the remarkable increases in plasma volume observed in pregnancy. Accurate estimates of plasma volume expansion during pregnancy depend on correctly timing and measuring plasma volume in nonpregnant women. However, to date, there is no consensus on the pattern of plasma volume across the menstrual cycle. We prospectively measured plasma volume in 45 women across a single menstrual cycle. A urine-based fertility monitor was used to time three clinic visits to distinct points in the menstrual cycle: the early follicular phase (~day 2), periovulation (~day 12), and the mid-point of the luteal phase (~day 21)-based on a 28-day cycle length. Healthy women aged 18-41 years with regular menstrual cycles and a healthy body weight were enrolled in the study. At each visit, blood samples were collected before and after injection of 0.25 mg/kg body weight of indocyanine green dye (ICG). Pre- and post-ICG injection plasma samples were used to measure plasma volume. Preinjection samples were used to measure ovarian hormones and plasma osmolality. Mean plasma volume was highest during the early follicular phase (2,276 ± 478 ml); it declined to 2,232 ± 509 ml by the late follicular phase and to 2,228 ± 502 ml by the midluteal phase. This study found that overall variations in plasma volume are small across the menstrual cycle. Therefore, in clinical practice and research, the menstrual cycle phase may not be an important consideration when evaluating plasma volume among women of reproductive age.

Can Variable Plasma Volume Alterations Affect the Efficiency of the First Trimester Screening Test?

BACKGROUND

The aim of this study was to assess the effect of plasma volume alteration determined by hematocrit on biochemical parameters of the first trimester screening test.

METHODS

Enrolled in this study were 1,424 pregnant women in their first trimester who underwent a first trimester screening test. Fetal Nuchal Trancluciency measurement was obtained by ultrasonographic evaluation. Blood samples were taken for complete blood count, serum free β-HCG, and PAPP-A between 11 and 14 weeks of gestation. The effect of plasma volume alteration on the screening test was evaluated. Mean corpuscular volume was used to rule out possible iron deficiency anemia.

RESULTS

There were 59 women with combined risk > 1/270. Of these 59 women, there were 21 false positive results (1.5%). Serum Htc significantly predicted the false positive cases (AUC: 0.839, p < 0.001). The optimal cutoff value was obtained at a value of 30.2% with 85% sensitivity and 75% specificity.

CONCLUSIONS

Our study suggests that the degree of plasma alterations may affect the serum levels of the biochemical components of the first trimester screening test for aneuploidy, thereby leading to false positive test results.

Fetal Physiologically Based Pharmacokinetic Models: Systems Information on Fetal Blood Components and Binding Proteins

BACKGROUND

Fetal blood and plasma volume and binding components are critical parameters in a fetal physiologically based pharmacokinetic model. To date, a comprehensive review of their changes during fetal development has not been reported.

OBJECTIVE

The objective of this work was to collate and analyze physiological information on fetal blood and plasma volume and binding component data during development and to provide a mathematical description of these parameters that can be integrated within a fetal physiologically based pharmacokinetic model.

METHODS

A comprehensive literature search was conducted on fetal blood and plasma volume and binding component parameters and their changes during growth from apparently healthy fetuses from uncomplicated pregnancies. Collated data were assessed, integrated, and analyzed to establish continuous mathematical functions describing their growth trends with fetal age and weight.

RESULTS

Data were available from 14 studies for blood, ten studies for hematocrit, 12 studies for albumin, and four studies for alpha-1-acid glycoprotein, while plasma and red blood cell volumes were described based on blood and hematocrit data. Fetal physiologically based pharmacokinetic parameters, including blood, plasma and red blood cell volumes, hematocrit, serum albumin, and acid glycoprotein were quantified as a function of fetal age and weight. Variability around the mean parameters at different fetal ages was also investigated. The growth of each of these parameters was different (with respect to direction and monotonicity).

CONCLUSIONS

Despite the limitations identified in the availability of some values, the collected data presented in this article provide a useful resource for fetal physiologically based pharmacokinetic modeling. Potential applications include predicting xenobiotic exposure and risk assessment in the fetus following maternally administered drugs or unintended exposure to environmental toxicants.

Correlation of Quantitated Intravascular Volume with Blood Pressure in Patients with Systemic Hypertension

Volume management is an essential component of anti-hypertensive therapy. Different volume phenotypes have been proposed. We sought to study the total blood volume (TBV), plasma volume (PV), and red blood cell volume (RBV) in hypertensive patients. We included patients followed in an outpatient cardiology clinic from 1998 to 2003. Blood volume (BV) parameters were measured using radioisotope iodine-131-labeled albumin dilution technique. Values were expressed as percentage (%) deviation from ideal volumes. A total of 95 patients were included. The intravascular volume distribution as percent deviation from normal volume ranged from - 23 to + 28% for TBV, - 22 to + 36% for PV and - 29 to + 37% for RBV. There was no significant correlation between systolic BP and any of the BV parameters (TBV and SBP, r = - 0.03; PV and SBP, r = - 0.12; RBV and SBP, r = - 0.08). Patients with hypertension have a wide variation in BV parameters. BV does not correlate with SBP.

Physiological Responses to Heat Acclimation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The aim of this meta-analysis was to evaluate the effectiveness of heat acclimatization (HA) on time trial (TT) performance, maximum oxygen uptake (VO_2max), exercise heart rate (HR_E), time trials heart rate (HR_TT), maximal heart rate (HR_M), core temperature (T_C), mean skin temperature (T_S), thermal comfort (T_Comf), plasma volume (PV), blood lactate concentration and rate of perceived exertion (RPE). Cochrane-CENTRAL, EMBASE, CINAHL and PubMed databases and reference lists of included studies were searched for randomized controlled trials that investigated the efficacy of HA in athletes. Data were then extracted from the entered studies for analyses. A total of 11 randomised controlled trials (215 participants; mean age, 26.09 years; 91% men) were included after screening of 508 titles and abstracts and 19 full-text articles. The pooled standard mean difference (SMD) between the HA and non-HA groups were 0.50 (95% CI: 0.03 to 0.97, p = 0.04) for TT performance and 1 (95% CI: 1 to 2, p = 0.007) for HR_TT. The pooled mean difference (MD) between the HA and non-HA groups were -7 (95% CI: -13 to -1, p = 0.03) for HR_M. The changes in T_Comf and RPE were too small to be meaningful. There were no significant differences between the HA and non-HA groups for VO_2max, HR_E, T_C, T_S, PV and blood lactate concentration (all p > 0.05). This meta-analysis implies that HA may improve tolerance to discomfort during heat exposure, but may not necessarily improve the associated physiological markers of improved performance.

Racial differences in hemoglobin and plasma volume variation: implications for muscle performance and recovery

Objective: To examine the effect of race differences on sprint performance, Hemoglobin (Hb), Hematocrit (Ht) and plasma volume (PV) variation in response to repeated sprint exercise. Design: Thirty-six healthy, moderately trained men and women (20.8 ± 0.2 year-old) volunteered to participate in this study. They were allocated to one of the four groups according to their gender and race: Black men's group (BM, n = 9), White men's group (WM, n = 9), Black women's group (BW, n = 9) and White women's group (WW, n = 9). All participants performed the running-based anaerobic sprint test (RAST), which consists of six 35-m sprints with 10 s of recovery in-between. Six venous blood samples were collected to determine Hb, Ht and PV levels at rest, after warm-up, immediately post- and at 5, 15 and 30 min post-RAST. Blood lactate is also sampled during the 3rd minutes of recovery. Results: The best running time was significantly shorter (P = .002) in BW compared to WW. We have observed significantly higher Hb (P = .010) and Ht (P = .004) levels in BW compared to WW during the 5th minute of recovery. During RAST, the PV decreased significantly (P = .007) in WM only. Black groups had lower (P < .05) lactate levels compared to the white subjects. During recovery, PV increase was significantly (P = .003) higher in WW compared to BW during the 5th minute of recovery. Conclusion: This study demonstrated that sprint and repeated sprint performances were different between white and black women. Differences in anaerobic performance between the groups were associated with racial differences in lactate levels and blood count among women's group during recovery time. Hence, it is important to take into account this race-related difference in hematological parameters in responses to intense efforts.

Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements

This experiment aimed to investigate the efficacy of twice-daily, nonconsecutive heat acclimation (TDHA) in comparison to once-daily heat acclimation (ODHA) and work matched once- or twice-daily temperate exercise (ODTEMP, TDTEMP) for inducing heat adaptations, improved exercise tolerance, and cytokine (immune) responses. Forty males, matched biophysically and for aerobic capacity, were assigned to ODHA, TDHA, ODTEMP, or TDTEMP. Participants completed a cycling-graded exercise test, heat acclimation state test, and a time to task failure (TTTF) at 80% peak power output in temperate (TTTFTEMP : 22°C/40% RH) and hot conditions (TTTFHOT : 38°C/20% RH), before and after 10-sessions (60 min of cycling at ~2 W·kg-1 ) in 45°C/20% RH (ODHA and TDHA) or 22°C/40% RH (ODTEMP or TDTEMP). Plasma IL-6, TNF-α, and cortisol were measured pre- and postsessions 1, 5, and 10. ODHA and TDHA induced equivalent heat adaptations (P < 0.05) (resting rectal temperature [-0.28 ± 0.22, -0.28 ± 0.19°C], heart rate [-10 ± 3, -10 ± 4 b·min-1 ], and plasma volume expansion [+10.1 ± 5.6, +8.5 ± 3.1%]) and improved heat acclimation state (sweat set point [-0.22 ± 0.18, -0.22 ± 0.14°C] and gain [+0.14 ± 0.10, +0.15 ± 0.07 g·sec-1 ·°C-1 ]). TTTFHOT increased (P < 0.001) following ODHA (+25 ± 4%) and TDHA (+24 ± 10%), but not ODTEMP (+5 ± 14%) or TDTEMP (+5 ± 17%). TTTFTEMP did not improve (P > 0.05) following ODHA (+14 ± 4%), TDHA (14 ± 8%), ODTEMP (9 ± 10%) or TDTEMP (8 ± 13%). Acute (P < 0.05) but no chronic (P > 0.05) increases were observed in IL-6, TNF-α, or cortisol during ODHA and TDHA, or ODTEMP and TDTEMP. Once- and twice-daily heat acclimation conferred similar magnitudes of heat adaptation and exercise tolerance improvements, without differentially altering immune function, thus nonconsecutive TDHA provides an effective, logistically flexible method of HA, benefitting individuals preparing for exercise-heat stress.

Usefulness of Estimated Plasma Volume at Postdischarge Follow-Up to Predict Recurrent Events in Patients With Heart Failure

Hospital readmission for patients admitted with heart failure is a persistent problem. Better identification of patients at high risk of readmission for volume overload could have clinical implications. We evaluated estimated plasma volume (ePV), a marker of congestion, to predict readmission for patients seen early after discharge for heart failure. We identified patients hospitalized with a primary heart failure diagnosis and were then seen in a postdischarge clinic. We assessed clinical factors, ePV (derived from hemoglobin and hematocrit), and B-type natriuretic peptide (BNP). The primary outcome was death or readmission for heart failure within 90 days of discharge. We identified 218 patients, of whom 23% experienced the primary outcome. No clinical variables at time of admission were different between those who did and did not experience the primary outcome, nor were BNP (1,581 vs 1,267 pg/ml, p = 0.33) or ePV (6.00 vs 5.80, p = 0.36). At clinic follow-up, both BNP (1,164 vs 636, p = 0.002) and ePV (6.18 vs 5.58, p = 0.02) were higher in those with subsequent events. Kaplan-Meier survival analysis showed that the lowest tertile of ePV had significantly lower incidence of the primary outcome than the other 2 tertiles (12% vs 29% and 27%, p = 0.02). Estimated plasma volume remained independently predictive of outcomes after controlling for BNP (p <0.05). In conclusion, EPV may be predictive of death or hospital readmission in heart failure patients seen soon after discharge, independent of BNP. Its potential warrants future prospective research evaluating its utility in larger heart failure cohorts.

Replicating measurements of total hemoglobin mass (tHb-mass) within a single day: precision of measurement; feasibility and safety of using oxygen to expedite carbon monoxide clearance

Hemoglobin concentration ([Hb]) is a function of total hemoglobin mass (tHb-mass) and plasma volume. [Hb] may fall by dilution due to plasma volume expansion and changes in the perioperative period may therefore correlate poorly with blood loss. A simple, reliable, repeatable way to measure plasma volume and tHb-mass would have substantial clinical utility. The "optimized carbon monoxide re-breathing method" (oCOR) meets these criteria. However, it is recommended that a minimum of 12 h (when breathing room air) is left between repeat measurements. Twenty-four subjects underwent 3 days of testing. Two oCOR tests were performed (T1 and T2), 3 h apart, with a different CO clearance method employed between tests aiming to keep the carboxyhemoglobin level below 10%. The primary aim was to ascertain whether tHb-mass testing could be safely repeated within 3 h if carboxyhemoglobin levels were actively reduced by breathing supplemental oxygen (PROCA ). Secondary aims were to compare two other clearance methods; moderate exercise (PROCB ), or a combination of the two (PROCC ). Finally, the reliability of the oCOR method was assessed. Mean (SD) tHb-mass was 807.9 ± (189.7 g) (for T1 on day 1). PROCA lowered the carboxyhemoglobin level from the end of T1 (mean 6.64%) to the start of T2 (mean 2.95%) by a mean absolute value of 3.69%. For PROCB and PROCC the mean absolute decreases in carboxyhemoglobin were 4.00% and 4.31%, respectively. The fall in carboxyhemoglobin between T1 and T2 was greatest in PROCC ; this was statistically significantly lower than that of PROCA (P = 0.0039) and PROCB (P = 0.0289). The test-retest reliability for the measurement of total hemoglobin mass was good with a mean typical error (TE) of 2.0%. The oCOR method is safe and can be repeated within 3 h when carbon monoxide is suitably cleared between tests. Using oxygen therapy alone adequately achieves this.

Changes in Total Protein Concentration Due to Fluid Removal During and Shortly after Hemodialysis

BACKGROUND

Changes in plasma volume during hemodialysis are complex and have been shown to depend on the rate of fluid removal and the degree of fluid overload. We examined changes in total protein concentration during and shortly after a dialysis treatment in archived data from the HEMO study.

METHODS

During follow-up months 4 and 36 of the HEMO study, additional blood samples were obtained during a typical dialysis session at 30 and 60 min after dialysis. In 315 studies from 282 patients where complete data were available, we calculated the concentration change in total protein and compared it to the modeled change in both total body water and extracellular fluid space as derived from 2-pool urea kinetic modeling.

RESULTS

The mean postdialysis modeled urea volume (V) was 31.1 ± 6.18 L. Mean fluid removal was 2.76 ± 1.27 kg, over a session length of 207 ± 28 min. The ratio of predialysis V to postdialysis V averaged 1.090 ± 0.040. The mean TP ratios (post/pre) at 0, 30, and 60 min postdialysis averaged 1.121 ± 0.070 (SD), 1.091 ± 0.090, and 1.091 ± 0.086. The dialysate to serum sodium gradient, studied in a different group of treatments where this information was available, had no impact on these findings, nor did the length of the interdialytic interval.

CONCLUSIONS

On average, after equilibration, the change in plasma volume due to fluid removal is similar to the modeled change in total body water (urea space), irrespective of dialysate to serum sodium gradient. This supports previous observations that during dialysis with ultrafiltration, plasma volume contracts to a lesser degree than the interstitial volume and that some fluid may be removed from spaces other than the extracellular fluid.

An extended reference region model for DCE-MRI that accounts for plasma volume

The reference region model (RRM) for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) provides pharmacokinetic parameters without requiring the arterial input function. A limitation of the RRM is that it assumes that the blood plasma volume in the tissue of interest is zero, but this is often not true in highly vascularized tissues, such as some tumours. This study proposes an extended reference region model (ERRM) to account for tissue plasma volume. Furthermore, ERRM was combined with a two-fit approach to reduce the number of fitting parameters, and this was named the constrained ERRM (CERRM). The accuracy and precision of RRM, ERRM and CERRM were evaluated in simulations covering a range of parameters, noise and temporal resolutions. These models were also compared with the extended Tofts model (ETM) on in vivo glioblastoma multiforme data. In simulations, RRM overestimated K^trans by over 10% at v_p  = 0.01 under noiseless conditions. In comparison, ERRM and CERRM were both accurate, with CERRM showing better precision when noise was included. On in vivo data, CERRM provided maps that had the highest agreement with ETM, whilst also being robust at temporal resolutions as poor as 30 s. ERRM can provide pharmacokinetic parameters without an arterial input function in tissues with non-negligible v_p where RRM provides inaccurate estimates. The two-fit approach, named CERRM, further improves on the accuracy and precision of ERRM.

Corrected whole blood biomarkers - the equation of Dill and Costill revisited

An exercise bout or a dehydration often causes a reduction in plasma volume, which should be acknowledged when considering the change in biomarkers before and after the plasma changing event. The classic equation from Dill and Costill (1974, J. Appl. Physiol., 37, 247-248) for plasma volume shift is usually utilized in such a case. Although this works well with plasma and serum biomarkers, we argue in this note that this traditional approach gives misleading results in the context of whole blood biomarkers, such as lactate, white cells, and thrombocytes. In this study, we demonstrate that to calculate the change in the total amount of circulating whole blood biomarker, one should utilize a formula [Formula: see text] Here Hb and BM are, respectively, the concentrations for the hemoglobin and for the inspected whole blood biomarker before (pre) and after (post) the plasma changing incident.

Evaluation of Subclinical Fluid Overload Using Lung Ultrasound and Estimated Plasma Volume in the Postoperative Period Following Kidney Transplantation

AIM

B-lines count measured with lung ultrasound (LUS) quantifies extravascular lung water and is validated in the setting of acute cardiac failure or chronic dialysis. Patients are often kept in moderately overhydrated states during the early postoperative period following kidney transplantation (KT). We described congestion changes during the early postoperative period following KT and the feasibility of LUS in this setting.

METHODS

LUS (28 scanning-points method) and inferior vena cava (IVC) measurements were routinely performed in 36 patients after KT. Estimated plasma volume (ePV) was calculated from hemoglobin and hematocrit levels.

RESULTS

No patient had >15 B-lines during the hospital stay. B-lines slightly increased until Day 4 after KT (Day 1, 1.7 ± 1.7; Day 4, 2.5 ± 2.5) and decreased up to Day 10 (1.4 ± 2.2; P vs Day 4 <.05). More B-lines were observed in patients aged older than 60 (P = .01 at Day 4) whereas IVC diameter and ePV were similar. In patients older than 60, B-lines had weak correlation with body weight variation (r = 0.64; P < .05), IVC diameters (r = 0.59 at Day 4 and r = 0.58 at Day 10; P < .05) but a strong correlation with ePV (r = 0.93 at Day 14; P < .05). B-line changes from Day 1 to Day 10 correlated with IVC diameter changes (r = 0.62; P < .05).

CONCLUSION

LUS identifies subtle congestion changes during the early postoperative period following KT. The hyperhydration strategy usually followed during this period does not result in overt pulmonary congestion as assessed by LUS, even in older recipients.