The Importance of Correct Norms in Blood Volume Measurement

Blood Volume Analysis and Cardiorenal Syndrome: From Bench to Bedside

BACKGROUND

This review delves into the intricate landscape of cardiorenal syndrome (CRS) and highlights the pivotal role of blood volume analysis (BVA) in improving patient care and outcomes.

SUMMARY

BVA offers a direct and highly accurate quantification of intravascular volume, red blood cell volume, and plasma volume, complete with patient-specific norms. This diagnostic tool enhances the precision of diuretic and red cell therapies, significantly elevating the effectiveness of conventional care.

KEY MESSAGES

Our objectives encompass a comprehensive understanding of how BVA informs the evaluation and treatment of CRS, including its subtypes, pathophysiology, and clinical significance. We delve into BVA principles, techniques, and measurements, elucidating its diagnostic potential and advantages compared to commonly used surrogate measures. We dissect the clinical relevance of BVA in various CRS scenarios, emphasizing its unique contributions to each subtype. By assessing the tangible impact of BVA on patient outcomes through meticulous analysis of relevant clinical studies, we unveil its potential to enhance health outcomes and optimize resource utilization. Acknowledging the challenges and limitations associated with BVA's clinical implementation, we underscore the importance of multidisciplinary collaboration among cardiologists, nephrologists, and other clinicians. Finally, we identify research gaps and propose future directions for BVA and CRS, contributing to ongoing advancements in this field and patients affected by this complicated clinical syndrome.

Role of splanchnic circulation in the pathogenesis of heart failure: State-of-the-art review

A hallmark of heart failure (HF), whether it presents itself during rest or periods of physical exertion, is the excessive elevation of intracardiac filling pressures at rest or with exercise. Many mechanisms contribute to the elevated intracardiac filling pressures, and notably, the concept of volume redistribution has gained attention as a cause of the elevated intracardiac filling pressures in patients with HF, particularly HF with preserved ejection fraction, who often present without symptoms at rest, with shortness of breath and fatigue appearing only during exertion. This phenomenon suggests cardiopulmonary system non-compliance and inappropriate volume distribution between the stressed and unstressed blood volume components. A substantial proportion of the intravascular blood volume is in the splanchnic vascular compartment in the abdomen. Preclinical and clinical investigations support the critical role of the sympathetic nervous system in modulating the capacitance and compliance of the splanchnic vascular bed via modulation of the greater splanchnic nerve (GSN). The GSN activation by stressors such as exercise causes excessive splanchnic vasoconstriction, which may contribute to the decompensation of chronic HF via volume redistribution from the splanchnic vascular bed to the central compartment. Accordingly, for example, GSN ablation for volume management has been proposed as a potential therapeutic intervention to increase unstressed blood volume. Here we provide a comprehensive review of the role of splanchnic circulation in the pathogenesis of HF and potential novel treatment options for redistributing blood volume to improve symptoms and prognosis in patients with HF.

Blood volume phenotypes and patient sex in resistant hypertension

The relationship of blood volume (BV) to systemic blood pressure (BP) is not well defined in resistant hypertension (RH). The goal of this study was to examine the extent to which systemic BP stratified by patient sex would impact BV phenotypes. A retrospective analysis of clinical and quantitative BV data was undertaken in a cohort of ambulatory patients with a history of controlled and uncontrolled RH. We analyzed 253 unique BVs with 54% of patients above goal BP of <150 mmHg. BV phenotypes were highly variable but no correlation of systolic BP to absolute BV or percentage deviation from normal volume was identified in either sex. Males demonstrated overall larger absolute BVs with higher prevalence of large plasma volume (PV) expansion; females were overall more hypovolemic by total BV but with a higher frequency of normal PV than males. Females trended towards more RBC mass deficit (true anemia) (49% vs. 38%. P  = 0.084) while more males demonstrated RBC mass excess (erythrocythemia) (21% vs. 11%, P  = 0.029). Importantly, a significant portion (52%) of patients with true anemia identified by BVA would go undetected by hemoglobin measurement alone. BV phenotypes are highly diverse in patients with RH. However, absolute BV or variability in BV phenotypes even when stratified by patient sex did not demonstrate an association with systemic BP. BV phenotyping provides a key to optimizing clinical management by identifying RBC mass profiles particularly distinguishing true anemia, dilutional anemia, and erythrocythemia and the contribution of PV expansion. Findings support the clinical utility of BV phenotyping in RH.

Insights into the diversity of blood donation practice across Asia: How blood collection agencies adapt donor criteria and processes to their population

BACKGROUND AND OBJECTIVES

Securing an adequate blood supply relies on accurate knowledge of blood donors and donation practices. As published evidence on Asian populations is sparse, this study aims to gather up-to-date information on blood donors and donation practices in Asia to assist planning and strategy development.

MATERIALS AND METHODS

Ten blood collection agencies (BCAs) provided 12 months' data on donors who met eligibility criteria or were deferred, as well as details of their donation practices. Body mass index and blood volumes were calculated and analysed.

RESULTS

Data on 9,599,613 donations and 154,834 deferrals from six national and four regional BCAs revealed varied donation eligibility and collection practices. Seven used haemoglobin (Hb) criteria below the World Health Organization anaemia threshold. Seven accepted donors weighing <50 kg. Data collection on the weight and height of donors and on deferrals was inconsistent, often not routine. Deferred donors appear to weigh less, with corresponding lower estimated blood volume.

CONCLUSION

The diversity in eligibility criteria and donation practices reflects each BCA's strategy for balancing donor health with securing an adequate blood supply. Use of lower Hb criteria substantiate their appropriateness in Asia and indicate the need to define Hb reference intervals relevant to each population. We encourage routine gathering of donor weight and height data to enable blood volume estimation and local optimization of donation volumes. Blood volume estimation formulae specific for the Asian phenotype is needed. Information from this study would be useful for tailoring donation criteria of Asian donors around the world.

Patient Selection and End Point Definitions for Decongestion Studies in Acute Decompensated Heart Failure: Part 2

Congestion is the most common manifestation of acute decompensated heart failure (ADHF). Residual congestion despite initial medical therapy is common and is recognized to be associated with worse outcomes; however, there are currently no standardized definition regarding decongestion end point. In the second part of this 2-part review, we provide a critical appraisal of decongestion definitions previously used in ADHF studies, review alternative metrics to define severity of volume overload, and propose a more granular 4-class congestion grading scheme and decongestion end point definitions that could potentially be included in future ADHF trials and consensus definitions.

Patient Selection and End Point Definitions for Decongestion Studies in Acute Decompensated Heart Failure: Part 1

Despite recent advances in the treatment of patients with chronic heart failure, acute decompensated heart failure remains associated with significant mortality and morbidity because many novel therapies have failed to demonstrate meaningful benefit. Persistent congestion in the setting of escalating diuretic therapy has been repeatedly shown to be a marker of poor prognosis and is currently being targeted by various emerging device-based therapies. Because these therapies inherently carry procedural risk, patient selection is key in the future trial design. However, it remains unclear which patients are at a higher risk of residual congestion or adverse outcomes despite maximally tolerated decongestive therapy. In the first part of this 2-part review, we aimed to outline patient risk factors and summarize current evidence for early recognition of high-risk profile for residual congestion and adverse outcomes. These factors are classified as relating to the following: (1) previous clinical course, (2) severity of congestion, (3) diuretic response, and (4) degree of renal impairment. We also aimed to provide an overview of key inclusion criteria in recent acute decompensated heart failure trials and investigational device studies and propose potential criteria for selection of high-risk patients in future trials.

Serial blood volume measurements in patients with compensated chronic heart failure: How do volume profiles change over time?

Among patients with chronic heart failure (HF) intravascular volume profiles vary significantly despite similar clinical compensation. However, little is known regarding changes in blood volume (BV) profiles over time. The objective of this analysis was to identify the extent and character of changes in volume profiles over time. A prospective analysis was undertaken in patients who were hospitalized and treated for fluid overload. Quantitative BV analyses were obtained in a compensated state at hospital discharge (baseline) and follow-up at 1, 3, and 6 mo. Data were available on 10 patients who remained stable without rehospitalization or medication change over a 6-mo period. Baseline BV profiles were highly variable at hospital discharge with an average deviation of +28% above normal in 6 patients and normal BV in 4 patients. Over the follow-up period, the median change in BV was -201 mL [-3% (-6, +3%)] from baseline with profiles remaining in the same volume category in 9 out of 10 patients. Crossover from normal BV to mild contraction (-13% of normal) occurred in one patient. Red blood cell mass demonstrated the largest change over 6 mo [median -275 (-410, +175) mL] with a deviation from normal of -14 (-20, +8) % (reflecting mild anemia). These findings suggest that BV profiles in clinically compensated patients with HF do not change substantially over a 6-mo period regardless of baseline expanded or normal BV. This lack of change in volume profiles particularly from an expanded BV has implications for long-term volume management, clinical outcomes, and also our understanding of volume homeostasis in HF.NEW & NOTEWORTHY The novel findings of this study demonstrate that blood volume profiles while highly variable in clinically compensated patients with HF on stable medical therapy do not change substantially over a 6-mo period regardless of baseline expanded or normal blood volumes. This lack of change in volume profiles particularly from an expanded blood volume has implications for long-term volume management and also for how we understand the pathophysiology of volume homeostasis in chronic HF.

Measurement of Blood Volume in Patients with Heart Failure: Clinical Relevance, Surrogates, Historical Background and Contemporary Methodology

The development of clinical congestion resulting from volume overload, either by renal fluid retention or redistribution of blood volume from venous reservoirs, is a recurrent scenario in patients with chronic heart failure (HF). As a result, the treatment of congestion, most commonly by initiating aggressive diuretic therapy, is a front-line issue in the management of patients with HF. However, the association of clinical congestion and volume overload with physical signs and symptoms, as well as other surrogates of volume assessment, has limitations in accuracy and, therefore, reliability to direct appropriate interventions. The ability to quantitate intravascular volume and identify the variability in volume profiles among patients with HF can uniquely inform individualized volume management and aid in risk stratification. This tool is provided by contemporary nuclear medicine-based BVA-100 methodology, which uses the well-established indicator-dilution principle and is a requested topic for discussion in this review.

Blood volume and chronic kidney disease in heart failure - Can volume expansion help balance the Cardio-Renal Axis for better clinical outcomes?

Intravascular volume is largely regulated by the kidneys but how differences in intravascular volume profiles interact with chronic kidney disease (CKD) to influence outcomes in chronic heart failure (HF) has not been explored. Our hypothesis was that a greater degree of volume expansion (VE) would moderate the impact of CKD on HF-related clinical outcomes. Quantitative blood volume (BV) data were available in 137 patients at the time of hospital discharge using a nuclear medicine radiolabeled albumin indicator-dilution technique. The study patients were stratified by the cohort median glomerular filtration rate (GFR, 44 ml/min/1.73 m² ). An a priori cut-point of ≥+25% above normal BV was then used to further stratify the two GFR subgroups and prospectively analyzed for 1-year HF-related mortality or 1st re-hospitalization. Persistent BV expansions ≥+25% were present in 51% of the cohort. In the subgroup with GFR above the median (N = 68) greater or lesser BV expansion from +25% did not differentiate outcomes. However, in the subgroup with GFR below the median (N = 69), BV expansion-stratified risk (log-rank p = 0.022) with <+25% VE associated with poorer outcomes, while VE ≥ + 25% was associated with lower risk and comparable to GFR above the median. In patients with chronic HF, significant intravascular VE and CKD are common co-existing conditions. The presence of larger VE, however, appears to be a factor mitigating the impact of declining renal function on clinical outcomes, and as an element of volume pathophysiology warrants further study.

Strategy for Calculating Magnesium Sulfate Dose in Obese Patients: A Randomized Blinded Trial

Background. Magnesium sulfate has analgesic properties during the postoperative period. However, there is a knowledge gap in pharmacology related to the use of the real, ideal, or corrected ideal body weight to calculate its dose in obese patients. This trial compared postoperative analgesia using actual and corrected ideal body weight. Methods. Seventy-five obese patients scheduled to undergo laparoscopic gastroplasty or cholecystectomy under general anesthesia were randomly assigned to three groups. The patients in the control group did not receive magnesium sulfate; the other two groups received magnesium sulfate at 40 mg·kg−1 of actual body weight or corrected ideal body weight. Results. In patients with body mass index >30 mg·kg−2 (mean body mass index ranging from 32.964 kg·m−2 to 33.985 kg·m−2, according to the groups) scheduled for video laparoscopic cholecystectomy, there were no differences in the blood magnesium concentrations in the groups receiving magnesium sulfate throughout the study, regardless of whether the strategy to calculate its dose was based on total or corrected ideal body weight. Patients in the groups receiving magnesium sulfate showed a significant reduction in morphine consumption ( $p\le 0.001$ ) and pain scores ( $p=0.006$ ) in the postoperative period compared to those in the control group. There were no significant differences in morphine consumption ( $p=0.323$ ) or pain scores ( $p=0.082$ ) between the two groups receiving magnesium sulfate. There were no differences in the total duration of neuromuscular block induced by cisatracurium among the three groups ( $p=0.181$ ). Conclusions. Magnesium sulfate decreased postoperative pain and morphine consumption without affecting the recovery time of cisatracurium in obese patients undergoing laparoscopic cholecystectomy. Strategies to calculate the dose based on the actual or corrected ideal body weight had similar outcomes related to analgesia and the resulting blood magnesium concentration. However, as the sample in this trial presented body mass indices ranging from 30.11 kg·m−2 to 47.11 kg/m−2, further studies are needed to confirm these findings in more obese patients, easily found in centers specialized.

Delayed femoral vein ligation reduces operative time and blood loss during hip disarticulation in patients with extremity tumors

This study aimed to evaluate the effects of delayed femoral vein ligation on the clinical outcomes of hip disarticulation. We retrospectively reviewed 20 patients with extremity tumors (10 bone tumors and 10 soft tissue sarcomas [STS]) who underwent hip disarticulation. Patients treated for hip disarticulation with synchronous femoral vein ligation (n = 10, regular surgery group) and hip disarticulation with delayed femoral vein ligation (n = 10, delayed ligation group), respectively, were enrolled in this study. The operative time and blood loss were used to evaluate the clinical outcomes. The delayed ligation group had significantly lower operative times than the regular surgery group (P < 0.05). Total, hidden, and intraoperative blood loss were all significantly lower in the delayed ligation group than in the regular surgery group (P < 0.05). However, there were no significant differences in postoperative blood loss. In conclusion, delayed femoral vein ligation could significantly reduce the operative time, hidden blood loss, and intraoperative blood loss in patients undergoing hip disarticulation.

A novel Vascular Leak Index identifies sepsis patients with a higher risk for in-hospital death and fluid accumulation

PURPOSE

Sepsis is a leading cause of morbidity and mortality worldwide and is characterized by vascular leak. Treatment for sepsis, specifically intravenous fluids, may worsen deterioration in the context of vascular leak. We therefore sought to quantify vascular leak in sepsis patients to guide fluid resuscitation.

METHODS

We performed a retrospective cohort study of sepsis patients in four ICU databases in North America, Europe, and Asia. We developed an intuitive vascular leak index (VLI) and explored the relationship between VLI and in-hospital death and fluid balance using generalized additive models (GAM).

RESULTS

Using a GAM, we found that increased VLI is associated with an increased risk of in-hospital death. Patients with a VLI in the highest quartile (Q4), across the four datasets, had a 1.61-2.31 times increased odds of dying in the hospital compared to patients with a VLI in the lowest quartile (Q1). VLI Q2 and Q3 were also associated with increased odds of dying. The relationship between VLI, treated as a continuous variable, and in-hospital death and fluid balance was statistically significant in the three datasets with large sample sizes. Specifically, we observed that as VLI increased, there was increase in the risk for in-hospital death and 36-84 h fluid balance.

CONCLUSIONS

Our VLI identifies groups of patients who may be at higher risk for in-hospital death or for fluid accumulation. This relationship persisted in models developed to control for severity of illness and chronic comorbidities.

Blood volume expansion, normovolemia, and clinical outcomes in chronic human heart failure: more is better

Expansion in blood volume (BV) is a well-recognized response to arterial underfilling secondary to impaired cardiac output in heart failure (HF). However, the effectiveness of this response in terms of outcomes remains inadequately understood. Prospective analysis was undertaken in 110 patients with HF hospitalized and treated for fluid overload. BVs were measured in a compensated state at the hospital discharge using the indicator-dilution methodology. Data were analyzed for composite 1-year HF-related mortality/first rehospitalization. Despite uniform standard of care, marked heterogeneity in BVs was identified across the cohort. The cohort was stratified by BV expansion greater than or equal to +25% above normal (51% of cohort), mild-moderate expansion (22%), and normal BV (27%). Kaplan-Meier (K-M) survival estimates and regression analyses revealed BV expansion (greater than or equal to +25%) to be associated with better event-free survival relative to normal BV (P = 0.038). Increased red blood cell mass (RBCm; RBC polycythemia) was identified in 43% of the overall cohort and 70% in BV expansion greater than or equal to +25%. K-M analysis demonstrated polycythemia to be associated with better outcomes compared with normal RBCm (P < 0.002). Persistent BV expansion to include RBC polycythemia is common and, importantly, associated with better clinical outcomes compared with normal total BV or normal RBCm in patients with chronic HF. However, compensatory BV expansion is not a uniform physiological response to the insult of HF with marked variability in BV profiles despite uniform standard of care diuretic therapy. Therefore, recognizing the variability in volume regulation pathophysiology has implications not only for impact on clinical outcomes and risk stratification but also potential for informing individualized volume management strategies.NEW & NOTEWORTHY The novel findings of this study demonstrate that intravascular volume profiles among the patients with chronic heart failure (HF) vary substantially even with similar clinical compensation. Importantly, a profile of blood volume (BV) expansion (compared with a normal BV) is associated with lower HF mortality/morbidity. Furthermore, RBC polycythemia is common and independently associated with improved outcomes. These observations support BV expansion with RBC polycythemia as a compensatory mechanism in chronic HF.

Contributions of cardiac dysfunction and volume status to central haemodynamics in chronic heart failure

AIMS

Elevated cardiac filling pressures producing clinical congestion in heart failure (HF) patients may be secondary to intravascular volume expansion or abnormalities in cardiac diastolic properties. The objective of this study was to assess the extent to which measures of myocardial function and intravascular volume correlate with haemodynamic abnormalities in chronic HF.

METHODS AND RESULTS

Subjects underwent invasive haemodynamic assessment, measurement of total blood volume (TBV) using radiolabel indicator-dilution methodology, and echocardiography to evaluate cardiac structure and function. Patients were divided into those with hypervolaemia (defined as TBV > +8% above referenced normal volume) and normal volume ('euvolaemia') (TBV ≤ + 8%). Of 66 patients, 39 (59%) were hypervolaemic and 27 (41%) normal TBV. Central venous pressure (CVP, P = 0.01) and pulmonary capillary wedge pressure (PCWP, P < 0.001) were higher in hypervolaemic compared with euvolaemic patients; however, 15% of hypervolaemic patients displayed normal pressures. Of euvolaemic patients, 70% displayed elevated CVP and 63% elevated PCWP. PCWP was moderately correlated with TBV (r = 0.42), left ventricular diastolic function (e' velocity, r = -0.44), and left atrial strain (r = -0.47). In multivariable regression TBV, left ventricular e', and left atrial strain were independently associated with PCWP (all P < 0.05).

CONCLUSIONS

While hypervolaemic patients displayed elevations in filling pressures, a substantial proportion (15%) had normal pressures, and of all subjects with elevated filling pressures nearly one third had normal TBVs. Importantly, of patients with normal volumes, a majority (>60%) display elevated filling pressures. Combined analysis of volume, pressure, and cardiac function may be helpful to guide comprehensive assessments of HF status.

Diuresis-Related Weight Loss Reflects Interstitial Compartment Decongestion with Minimal Impact on Intravascular Volume Expansion or Outcomes in Post-Acute Heart Failure: Metrics of Decongestion and Volume Status

BACKGROUND

Findings from heart failure (HF) studies linking diuresis-related weight loss to clinical decongestion and outcomes are mixed. Differential responses of interstitial and intravascular volume compartments to diuretic therapy and heterogeneity in volume profiles may confound the clinical interpretation of weight loss in patients with HF.

METHODS AND RESULTS

Data were prospectively collected in hospitalized patients requiring diuresis. Plasma volume (PV) was measured using I-131-labelled albumin indicator-dilution methodology. The cohort was stratified by tertiles of weight loss and analyzed for interstitial fluid loss relative to changes in PV and HF-related morality or first rehospitalization. Among 92 patients, the admission PV was expanded +42% (4.7 ± 1.2 L) above normal with significant variability (14% normal PV, 18% mild-moderate expansion, and 68% with large PV expansion [>+25% above normal]). With diuresis there were proportional decreases in interstitial volume (-6.5 ± 4.4%) and PV (-7.5 ± 11%); however, absolute decreases in the PV (-254 mL, interquartile range -11 to -583 mL) were less than 10% of interstitial volume loss (-5040 mL, interquartile range -2800 to -7989 mL); greater interstitial fluid loss did not translate into better outcomes (log-rank P = .430).

CONCLUSIONS

Diuresis-related decreases in weight reflect fluid loss from the interstitial compartment with only minor changes in the PV and without an impact on outcomes. Further, the degree of PV expansion at hospital admission does not drive the magnitude of the diuresis response, even with a wide spectrum of body weights; interstitial fluid overload is preferentially targeted and PV relatively preserved. Therefore, greater interstitial fluid loss reflects clinical decongestion, but not better outcomes, and a limited association with intravascular volume profiles potentially confounding weight loss as a prognostic metric in HF.

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.

Impact of Obesity on Volume Status in Patients With Ambulatory Chronic Heart Failure

BACKGROUND

Fluid overload is common in heart failure (HF) and obesity; however, the relationship between the extent of intravascular volume expansion and indices such as body mass index (BMI) in obese and non-obese patients with HF has not been defined to address the issue of a HF obesity phenotype.

METHODS

Total blood volume (TBV) was measured clinically using a radiolabeled albumin indicator-dilution technique in patients with predominately class III ambulatory chronic HF (N=66). Obesity was defined by BMI ≥30 kg/m².

RESULTS

Markedly increased intravascular volume expansion (defined by TBV expansion >+25% above normal) was highly prevalent in the obese (53%) compared to non-obese patients with HF (29%, P = .04) driven by plasma volume expansion. TBV was correlated with excess body weight and BMI (both P < .01). Also, cardiac index was higher, systemic vascular resistance lower, and left ventricular filling pressures comparable in obese compared with non-obese patients.

CONCLUSIONS

Quantitative assessment of intravascular volume demonstrates for the first time that severe (not mild or moderate) volume expansion is highly common in obese patients with ambulatory chronic HF. This supports an evolving concept of an obesity-specific HF phenotype. Further study is needed to understand the mechanisms controlling volume regulation and the potential compensatory or detrimental impact on outcomes in obesity and HF.

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.

An efficient method for measuring plasma volume using indocyanine green dye

Plasma volume (PV) can be an important marker of health status and may affect the interpretation of plasma biomarkers, but is rarely measured due to the complexity and time required. Indocyanine green (ICG) is a water-soluble tricarbocyanine dye with a circulatory half-life of 2–3 min, allowing for quick clearance and repeated use. It is used extensively in medical diagnostic tests including ophthalmologic imaging, liver function, and cardiac output, particularly in critical care. ICG has been validated for measuring PV in humans, however previous work has provided minimal published details or has focused on a single aspect of the method. We aimed to develop a detailed, optimal protocol for the use of ICG to measure PV in women of reproductive age. We combined best practices from other studies and optimized the protocol for efficiency.

•

This method reduces the time from blood collection to PV determination to ˜2 h and the amount of plasma required to estimate PV to 2.5 mL (1.5 mL before ICG injection and 1.0 mL post-injection).

•

Participant inconvenience is reduced by inserting an intravenous (IV) catheter in only one arm, not both arms.

•

Five post-injection plasma samples (2–5 min after ICG bolus) are enough to accurately develop the decay curve for plasma ICG concentration and estimate PV by extrapolation.

A Novel Fluorescent Clinical Method to Rapidly Quantify Plasma Volume

OBJECTIVES

To determine the performance of a rapid fluorescent indicator technique for measuring plasma volume (PV).

METHODS

This was an open-label, observational evaluation of a two-component intravenous visible fluorescent dye technique to rapidly measure PV in 16 healthy subjects and 16 subjects with chronic kidney disease (8 stage 3 and 8 stage 4 CKD), at 2 clinical research sites. The method consisted of a single intravenous injection of 12 mg of a large 150-kDa carboxy-methyl dextran conjugated to a fluorescent rhodamine-derived dye as the PV marker (PVM), and 35 mg of a small 5-kDa carboxy-methyl dextran conjugated to fluorescein, the renal clearance marker. Dye concentrations were quantified 15 min after the injections for initial PV measurements using the indicator-dilution principle. Additional samples were taken over 8 h to evaluate the stability of the PVM as a determinant of PV. Blood volumes (BV) were calculated based on PV and the subject's hematocrit. Pharmacokinetic parameters were calculated from the plasma concentration data taken over several days using noncompartmental methods (Phoenix WinNonlin®). Linear correlation and Bland-Altman plots were used to compare visible fluorescent injectate-measured PV compared to Nadler's formula for estimating PV. Finally, 8 healthy subjects received 350 mL infusion of a 5% albumin solution in normal saline over 30 min and a repeat PV determination was then carried out.

RESULTS

PV and BV varied according to weight and body surface area, with PV ranging from 2,115 to 6,234 mL and 28.6 to 41.9 mL/kg when weight adjusted. Both parameters were stable for > 6 h with repeated plasma measurements of the PVM. There was no difference between healthy subjects and CKD subjects. Overall, there was general agreement with Nadler's estimation formula for the mean PV in subjects. A 24-h repeat dose measurement in 8 healthy subjects showed PV variability of 98 ± 121 mL (mean = 3.8%). Additionally, following an intravenous bolus of 350 mL of a 5% albumin solution in normal saline in 8 healthy subjects, the mean (SD) measured increase in PV was 356 (±50.0) mL post-infusion. There were no serious adverse events reported during the study.

CONCLUSIONS

This minimally invasive fluorescent dye approach safely allowed for rapid, accurate, and reproducible determination of PV, BV, and dynamic monitoring of changes following fluid administration.

Blood volume analysis as a guide for dry weight determination in chronic hemodialysis patients: a crossover study

BACKGROUND

Volume overload and depletion both lead to high morbidity and mortality. Achieving euvolemia is a challenge in patients with end stage kidney disease on hemodialysis (HD). Blood volume analysis (BVA) uses radiolabeled albumin to determine intravascular blood volume (BV). The measured BV is compared to an ideal BV (validated in healthy controls). We hypothesized that BVA could be used in HD to evaluate the adequacy of the current clinically prescribed "estimated dry weight" (EDW) and to titrate EDW in order to improve overall volume status. We were also interested in the reproducibility of BVA results in end stage kidney disease.

METHODS

Twelve adults on chronic HD were recruited; 10 completed the study. BVA (Daxor, New York, NY, USA) was used to measure BV at baseline. EDW was kept the same if the patient was deemed to be euvolemic by BVA otherwise, the prescribed EDW was changed with the aim that measured BV would match ideal BV. A second BVA measurement was done 1-3 months later in order to measure BV again.

RESULTS

Based on BVA, 6/10 patients were euvolemic at baseline and 5/10 were euvolemic at the second measurement. When comparing patients who had their prescribed EDW changed after the initial BVA to those who did not, both groups had similar differences between measured and ideal BV (P = 0.75). BV values were unchanged at the second measurement (P = 0.34) and there was no linear correlation between BV change and weight change (r² = 0.08).

CONCLUSIONS

This pilot study is the first longitudinal measurement of BVA in HD patients. It revealed that changing weight did not proportionally change intravascular BV. BV remained stable for 1-3 months. BVA may not be helpful in clinically stable HD patients but studies on patients with hemodynamic instability and uncertain volume status are needed.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02717533), first registered February 4, 2015.

MRI gadolinium dosing on basis of blood volume

PURPOSE

Gadolinium-based contrast agents (GBCAs) for MRI are generally administrated in direct relationship to body weight. Instead, we propose a model for GBCA dosing on the basis of blood volume. The new method was tested by exploring the associations between MRI T1 mapping indices and weight in the MESA (Multi-Ethnic Study of Atherosclerosis.

METHODS

Empirically derived methods based on sex and body habitus were used to calculate blood volumes. GBCA dose (in mL) in blood (in L) was calculated as the injected volume divided by the blood volume (i.e., DBV). Of the 1219 participants with cardiac MRI T1 mapping, 845 studies had standard dose of 0.15 mmol/kg (cohort 1) and 166 studies had 30 mL of GBCA regardless of weight (cohort 2). We also created a specific cohort with similar DBV (N = 357; cohort 3).

RESULTS

Postcontrast blood relaxation rate R1blood and DBV were significantly correlated (R = 0.641; P < 0.001). R1blood was significantly associated with weight in cohort 1 and 2, but the correlation coefficient was positive for cohort 1 and negative for cohort 2, indicating GBCA overdosing in cohort 1 and underdosing in cohort 2 in heavy relative to lean subjects. R1blood was not associated with weight in cohort 3. Simulated results demonstrated that less contrast should be administrated for heavy subjects compared to the conventional weight-based dose.

CONCLUSION

GBCA dosing on the basis of blood volume could improve the efficacy and safety of contrast-enhanced MRI studies. This method could be implemented to standardize dose and augment precision in study comparisons.

Reducing Blood Loss in Revision Total Hip and Knee Arthroplasty: Tranexamic Acid Is Effective in Aseptic Revisions and in Second-Stage Reimplantations for Periprosthetic Infection

Introduction

The aim of the study was to determine the usefulness of tranexamic acid (TXA) in revision total hip arthroplasty (rTHA) and revision total knee arthroplasty (rTKA). We analyzed the perioperative blood loss with and without TXA in aseptic rTHA and rTKA as well as in second-stage reimplantation for hip and knee periprosthetic infection.

Materials and Methods

In this prospective cohort study, 147 patients receiving TXA (96 rTHA, 51 rTKA) were compared to a retrospective cohort of 155 patients without TXA (103 rTHA, 52 rTKA). The TXA regimen consisted of a preoperative bolus of 10 mg/kg bodyweight (BW) TXA plus 1 mg/kgBW/h perioperatively. Given blood products were documented and the perioperative blood loss was calculated. Thromboembolic events were registered until three months postoperatively. In subgroups, the effects of TXA were separately analyzed in 215 aseptic revisions as well as in 87 reimplantations in two-stage revisions for periprosthetic infection.

Results

Both TXA groups showed a significantly reduced mean blood loss compared to the respective control groups. The TXA group of rTHA patients had a mean blood loss of 2916 ml ± 1226 ml versus 3611 ml ± 1474 ml in the control group (p<.001). For the TXA group of rTKA patients, mean calculated blood loss was 2756 ml ± 975 ml compared to 3441 ml ± 1100 ml in the control group (p=.0012). A significantly reduced blood loss was also found in the TXA subgroups for aseptic and septic revision procedures. No thromboembolic events were recorded among the TXA groups.

Conclusions

There is a significant reduction of perioperative blood loss under TXA influence without an increased incidence of adverse events. The standard use of TXA can be recommended in aseptic hip and knee revision arthroplasties as well as in second-stage reimplantations for periprosthetic infection.

Duration of Retinol Isotope Dilution Studies with Compartmental Modeling Affects Model Complexity, Kinetic Parameters, and Calculated Vitamin A Stores in US Women

Background

Retinol isotope dilution (RID) indirectly estimates vitamin A (VA) status. Multicompartment modeling of RID data is used to refine study designs and equations to calculate VA stores. Previous studies suggest that VA in slowly turning over pools is not traced if follow-up is not long enough; however, shorter RID studies are being investigated. Few long-term models have been published.

Objective

We determined the effect of time on mathematical models of VA kinetics, model parameters, and outcomes.

Methods

In this longitudinal study, women (mean ± SD age: 22 ± 3 y; n = 7) were given 2.0 µmol [14,15]-13C2-retinyl acetate. Blood samples were staggered from 4 h to 152 d; the fraction of dose in serum was modeled with compartmental models. Four model-time categories were created: full models that used all data (median: 137 d; range 97-152 d) and truncated shorter studies of 14, 27, and 52 d (range: 42-62 d). Outcomes included number of compartments to adequately model serum data, kinetic parameters, total traced VA mass, and time-to-dose equilibration. To gain insight into longer follow-up, an additional participant was given 17.5 µmol 13C4-VA, and data were modeled as long as enrichment was above baseline (5 y).

Results

Longer follow-up times affected kinetic parameters and outcomes. Compared with the 14-d models, long-term full models required an additional compartment for adequate fit (14.3% compared with 100%; P = 0.0056) and had longer [median (quartile 1, quartile 3)] whole-body half-life [15.0 d (10.5, 72.6 d) compared with 135 d (115, 199 d); P = 0.0006], time-to-dose equilibration [3.40 d (3.14, 6.75 d) compared with 18.9 d (11.2, 25.7 d); P < 0.0001], and total traced mass [166 µmol VA (162, 252 µmol VA) compared with 476 µmol VA (290, 752 µmol VA); P = 0.0031].

Conclusions

Extended RID sampling alters numerous mathematically modeled, time-dependent outcomes in women. Length of study should be considered when using mathematical models for calculating total-body VA stores or kinetic parameters related to VA turnover. This study is registered at www.clinicaltrials.gov as NCT03248700.

Blood Volume Status in ME/CFS Correlates With the Presence or Absence of Orthostatic Symptoms: Preliminary Results

Introduction: Conflicting data have been published on the reduction of circulating blood volume in adults with Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The aim of the present study was to compare blood volumes based on the presence or absence of orthostatic symptoms. Methods and results: Twenty consecutive adults with ME/CFS participated in the study. All underwent dual isotope blood volume measurement and were evaluated for a clinical suspicion of orthostatic intolerance (OI). The mean age was 34 (10) years, and median duration of disease was 7.5 (6-10) years. The mean (SD) absolute blood volume was 59 (8) ml/kg, a value -11 (7) ml/kg below the reference blood volume. Of the 12 patients, 4 had no OI and 8 had a clinical suspicion of OI. In 8 patients with OI, absolute blood volumes were significantly lower than for the 4 without OI (56 [2] vs. 66 [5]; p < 0.05) as were the differences between the measured and the reference blood volume (-14 [2]; vs. -4 [3]; p < 0.02). Conclusions: Adults with ME/CFS had a significantly lower blood volume if they had a clinical suspicion of OI compared to those without a clinical suspicion of OI, as well as a significantly lower blood volume compared to the expected value. The data suggest that accounting for symptoms of OI could enhance the detection of the subset with reduced blood volume.

CORP: The assessment of total hemoglobin mass by carbon monoxide rebreathing

In this Cores of Reproducibility in Physiology (CORP) article, we present the theory and practical aspects of the carbon monoxide (CO) rebreathing method for the determination of total hemoglobin mass in humans. With CO rebreathing, a small quantity of CO is diluted in O2and rebreathed for a specified time period, during which most of the CO is absorbed and bound to circulating hemoglobin. The dilution principle then allows calculation of the total number of circulating hemoglobin molecules based on the number of absorbed CO molecules and the resulting changes in the fraction of carboxyhemoglobin in blood. Total hemoglobin mass is derived by multiplication with the molar weight of hemoglobin. CO rebreathing has been used for >100 yr and has undergone steady improvement so that today excellent values in terms of accuracy and precision can be achieved if the methodological precautions are carefully followed.

The distribution of blood concentrations of lead (Pb), cadmium (Cd), chromium (Cr) and manganese (Mn) in residents of the German Ruhr area and its potential association with occupational exposure in metal industry and/or other risk factors

OBJECTIVE

This study investigated the metal distribution in blood samples from the general population and the risk of having high metal concentration for metal workers.

METHODS

Metal concentrations were determined in archived blood samples from 1411 men and 1410 women (median age 59 and 57 years, respectively) collected at baseline (2000-2003) of the prospective Heinz Nixdorf Recall Study. Retrospective information on working in metal industry was obtained from previous follow-up survey (2011-2014). Odds ratios (ORs) with 95% confidence intervals (CI) of having a metal concentration >90th percentile (P90) for working in metal industry were calculated using logistic regression with adjustment for covariates.

RESULTS

More men than women worked in metal industry (57 vs. 3 at baseline). Male metal workers had increased blood lead (Pb) (OR: 2.86; 95% CI: 1.38-5.91) and manganese (Mn) (OR: 2.92; 95% CI: 1.46-5.81). Smoking (≥30 cigarettes/day) strongly influenced cadmium (Cd) in blood (OR: 168; 95% CI: 55-510). Women had higher Mn (8.92μg/L) and Cd (0.36μg/L) concentrations than men (Mn: 8.11μg/L; Cd: 0.29μg/L). Blood Pb in women (29.2μg/L) was lower than in men (33.2μg/L). None of the studied risk factors was significantly associated with chromium and nickel concentrations above their 90th percentiles.

CONCLUSIONS

In this population-based cohort we found evidence that working in metal industry was predictive for having elevated blood Pb and Mn concentrations. However, the 95th percentiles of all investigated metals were not significantly influenced by metal-related occupations. The present study is supportive for gender-specific reference values to limit occupational exposure to Mn and Pb. The strong influence of smoking on blood Cd hinders establishing reference values.

True Anemia―Red Blood Cell Volume Deficit―in Heart Failure

Background—

Anemia in heart failure (HF) is commonly diagnosed according to hemoglobin concentration [Hb], hence may be the result of hemodilution or true red blood cell volume (RBCV) deficit. Whether true (nonhemodilutional) anemia in HF can or cannot be generally inferred by [Hb] measurements and clinical correlates remains unclear. The purpose of this study was to systematically review the literature and investigate the status and correlates of RBCV in patients with HF.

Methods and Results—

MEDLINE, Scopus, and Web of Science were searched since their inceptions until April 2016 for articles directly reporting or allowing the calculation of intravascular volumes (RBCV, plasma volume) in patients with HF according to the International Council for Standardization in Hematology. Eighteen studies were included after systematic review, comprising a total of 368 patients with HF (limits for mean age=49–80 years, sex=0%–92% females, left ventricular ejection fraction=26%–61%). Mean RBCV was reduced (limits=67%–88% of normal) in all studies including HF patients with anemia (low [Hb]) (7 studies, n=127), whereas only 2 of 10 studies in nonanemic patients with HF presented lower than normal mean RBCV (90% and 96%). In metaregression analyses, RBCV was positively associated with [Hb] ( B =6.10, SE=1.44) and negatively associated with age ( B =−1.14, SE=0.23), % females ( B =−0.38, SE=0.04), left ventricular ejection fraction ( B =−0.81, SE=0.20), and body mass index ( B =−3.55, SE=0.46; P <0.001).

Conclusions—

Presence or absence of true anemia in patients with HF as determined by RBCV status mainly concurs with diagnosis based on [Hb] and presents negative relationships with age, female sex, left ventricular ejection fraction, and body mass index.

Assessment of circulating blood volume with fluid administration targeting euvolemia or hypervolemia

BACKGROUND

The occurrence of hypovolemia in the setting of cerebral vasospasm reportedly increases the risk for delayed ischemic neurologic deficits. Few studies have objectively assessed blood volume (BV) in response to fluid administration targeting normovolemia (NV) or hypervolemia (HV) and none have done so with crystalloids alone. The primary purpose was to evaluate the BV of patients with SAH receiving crystalloid fluid administration targeting NV or HV.

METHODS

The University of Washington IRB approved the study. Prospectively collected data was obtained from patients enrolled in a clinical trial and a concurrent group of patients who received IV fluids during the ICU stay. We defined a normovolemia (NV) and hypervolemia (HV) group based on the cumulative amount of IV fluid administered in mL/kg from ICU admission to day 5; ≥30-60 mL/kg/day (NV) and ≥60 mL/kg/day (HV), respectively. In a subgroup of patients, BV was measured on day 5 post ictus using iodinated (131)I-labeled albumin injection and the BVA-100 (Daxor Corp, New York, NY). Differences between the NV and HV groups were compared using Student's t-test with assumption for unequal variance.

RESULTS

Twenty patients in the NV and 19 in the HV groups were included. The HV group received more fluid and had a higher fluid balance than the NV group. The subgroup of patients in whom BV was measured on day 5 (n = 19) was not different from the remainder of the cohort with respect to the total amount of administered fluid and net cumulative fluid balance by day 5. BV was not different between the two groups and varied widely.

CONCLUSIONS

Routinely targeting prophylactic HV using crystalloids does not result in a higher circulating BV compared to targeting NV, but the possibility of clinically unrecognized hypovolemia remains.

A Theoretical Mathematical Model to Estimate Blood Volume in Clinical Practice

Perioperative intravenous (IV) fluid management is controversial. Fluid therapy is guided by inaccurate algorithms and changes in the patient's vital signs that are nonspecific for changes to the patient's blood volume (BV). Anesthetic agents, patient comorbidities, and surgical techniques interact and further confound clinical assessment of volume status. Through adaptation of existing acute normovolemic hemodilution algorithms, it may be possible to predict patient's BV by measuring hematocrit (HcT) before and after hemodilution. Our proposed mathematical model requires the following four data points to estimate a patient's total BV: ideal BV, baseline HcT, a known fluid bolus (FB), and a second HcT following the FB. To test our method, we obtained 10 ideal and 10 actual subject BV data measures from 9 unique subjects derived from a commercially used Food and Drug Administration-approved, semi-automated, BV analyzer. With these data, we calculated the theoretical BV change following a FB. Using the four required data points, we predicted BVs (BVp) and compared our predictions with the actual BV (BVa) measures provided by the data set. The BVp calculated using our model highly correlated with the BVa provided by the BV analyzer data set (df = 8, r = .99). Our calculations suggest that, with accurate HcT measurement, this method shows promise for the identification of abnormal BV states such as hyper- and hypovolemia and may prove to be a reliable method for titrating IV fluid.

Brain-type natriuretic peptide and right ventricular end-diastolic volume index measurements are imprecise estimates of circulating blood volume in critically ill subjects

BACKGROUND

Surrogate indicators have often been used to estimate intravascular volume to guide fluid management. Brain-type natriuretic peptide (BNP) has been used as a noninvasive adjunct in the diagnosis of fluid overload and as a marker of response to therapy, especially in individuals with congestive heart failure. Similarly, right ventricular end-diastolic volume index (RVEDVI) measurements represent another parameter used to guide fluid resuscitation. The aim of this study was to evaluate whether BNP and RVEDVI are clinically valuable parameters that can distinguish among hypovolemia, euvolemia, and hypervolemia, as measured by blood volume (BV) analysis in critically ill surgical subjects.

METHODS

This observational study was part of a prospective, randomized controlled trial. Subjects with pulmonary artery catheters for the treatment of traumatic injuries, severe sepsis/septic shock, cardiovascular collapse, adult respiratory distress syndrome, and postsurgical care were studied. Circulating BV was measured by a radioisotope dilution technique using the BVA-100 Analyzer (Daxor Corporation, New York, NY) within the first 24 hours of acute resuscitation. BV results were reported as percent deviation from the patient's ideal BV based on height and percent deviation from optimum weight. Hypovolemia was defined as less than 0%, euvolemia was defined as 0% to +16%, and hypervolemia was defined as greater than +16% deviation from ideal BV. RVEDVI was measured by continuous cardiac output pulmonary artery catheters (Edwards Lifesciences, Irvine, CA). BNP and RVEDVI measurements obtained with BV analysis were evaluated with Fisher's exact test and regression analysis.

RESULTS

In 81 subjects, there was no difference in BV status between those with BNP of 500 pg/mL or greater and BNP of less than 500 pg/mL (p = 0.82) or in those with RVEDVI of 140 mL/m or greater and RVEDVI of less than 140 mL/m (p = 0.43). No linear relationship existed between BV and these parameters.

CONCLUSION

In critically ill surgical patients, BNP and RVEDVI were not associated with intravascular volume status, although they may be useful as indices that reflect increased cardiac preload.

LEVEL OF EVIDENCE

Diagnostic study, level III.

Blood volume determination, a nuclear medicine test in evolution

The method for determining blood volume has evolved substantially since first attempts were made in the latter part of the nineteenth century with the exsanguination of animals. The now accepted methods are based on indicator dilution methodologies. First attempts utilized inert dyes such as Evans Blue and Cardiogreen. These were found to be impractical due, primarily, to their rapid clearance from the blood. For many years, the most accepted method for blood volume determination was the dual isotope technique. This procedure utilizes chromium 51 or 99mTc to label autologous red cells and radioiodine 125 or 131 to label human serum albumin (HSA). Plasma and red cell volumes are measured separately and the results "combined". The procedure requires on-site labeling of autologous red cells and HSA, and meticulous preparation of standards and doses. The complexity of this method leads to performance times of 6 to 8 hours. An FDA-approved single isotope method is now employed in over 60 major institutions. HSA is labeled with radioiodine 131 at an FDA radiopharmaceutical facility, and test doses and standards are provided to laboratories in kit form. The red cell volume is derived by a calculation utilizing the measured plasma volume and the value for the average whole-body hematocrit. All calculations are carried out by a dedicated microprocessor, and a final report is generated and printed. The results are compared with predicted normal values for male and female patients based on percentage deviation from normal weight. Preliminary results are available in 30 minutes and complete calculations in 90 minutes.

Performance changes during a weeklong high-altitude alpine ski-racing training camp in lowlander young athletes

Thousands of youth athletes travel to high altitude to participate in lift-access alpine sports. The purpose of this study was to examine the impact of acute high-altitude exposure on balance, choice reaction time, power, quickness, flexibility, strength endurance, and V[Combining Dot Above]O2max in youth lowlander athletes during a weeklong preseason training camp in Summit County, CO, USA. Eleven youth ski racers (4 boys and 7 girls; age, 13.7 ± 0.5 years; height, 157.2 ± 12.6 cm; weight, 52.4 ± 6.8 kg) with 7.7 ± 2.2 skiing years of experience participated in baseline testing at 160 m one week before the camp and a set of daily tests in the morning and afternoon at 2,828 m and skied between 3,328 and 3,802 m during a 6-day camp. Balance and choice reaction time tests were stagnant or improved slightly during the first 3 days and then improved on days 4 and 6. Vertical jump, flexibility, T-agility test, and push-ups in 1 minute improved on day 6. The number of sit-ups in 1 minute did not improve, and scores on the multistage fitness test decreased 20.34%. There was no effect of Lake Louise acute mountain sickness (AMS) questionnaire scores on performance variables measured. Athletes sojourning to high altitude for ski camps can train on immediate ascent but should slowly increase training volume over the first 3 days. Athletes should expect improvements in balance and reaction time 3-6 days into acclimatization. Coaches and athletes should expect about 20% of youth lowlander athletes to have signs and symptoms of AMS during the first 3 days of altitude exposure for alpine lift access sports at altitudes of up to 3,800 m.

Treating anemia in older adults with heart failure with a preserved ejection fraction with epoetin alfa: single-blind randomized clinical trial of safety and efficacy

BACKGROUND

Anemia is a common comorbidity in older adults with heart failure and a preserved ejection fraction and is associated with worse outcomes. We hypothesized that treating anemia with subcutaneous epoetin alfa would be associated with reverse ventricular remodeling and improved exercise capacity and health status compared with placebo.

METHODS AND RESULTS

Prospective, randomized, single-blind, 24-week study with blinded end point assessment among anemic (average hemoglobin of 10.4±1 g/dL) older adult patients (n=56; 77±11 years; 68% women) with heart failure and a preserved ejection fraction (ejection fraction=63±15%; B-type natriuretic peptide=431±366 pg/mL) was conducted. Treatment with epoetin alfa resulted in significant increases in hemoglobin (P<0.0001). Changes in end-diastolic volume (-6±14 versus -4±16 mL; P=0.67) at 6 months did not differ between epoetin alfa and placebo, but declines in stroke volume (-5±8 versus 2±10 mL; P=0.09) without significant changes in left ventricular mass were observed. Changes in 6-minute walk distance (16±11 versus 5±12 m; P=0.52) did not differ. Although quality of life improved by the Kansas City Cardiomyopathy Questionnaire and the Minnesota Living with Heart Failure Questionnaire in both cohorts, there were no significant differences between groups.

CONCLUSIONS

Administration of epoetin alfa to older adult patients with heart failure and a preserved ejection fraction compared with placebo did not change left ventricular end-diastolic volume and left ventricular mass nor did it improve submaximal exercise capacity or quality of life.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. UNIQUE IDENTIFIER: NCT00286182.

A dosing algorithm for erythropoietin alpha in older adults with heart failure and a preserved ejection fraction

AIMS

Erythropoietin stimulating agents (ESAs) is an active area of clinical investigation in heart failure (HF) but can cause hypertension and higher hemoglobin concentrations (Hb) that have been associated with adverse outcomes. We evaluated a dosing algorithm and potential confounders' effect on Hb and blood pressure (BP) in a clinical trial.

METHODS

In an ongoing randomized, placebo controlled, single blind clinical trial of ESA (epoetin alfa) in anemic patients with HF and a preserved ejection fraction (HFPEF), Hb was measured weekly as was BP, weight and concomitant medical therapy. A repeated measure mixed model evaluated determinants of weekly changes in Hb and BP.

RESULTS

Among 45 subjects (78 ± 11 years, 67% women, EF = 57 ± 9%) with a total of 780 repeated weekly Hb measures, Hb significantly increased over time in those assigned to ESA (β = 0.933, P < 0.0001), compared to placebo. Dose (β = -0.108, P < 0.0001), patient weight (β = -0.016, P = 0.0037), diuretic use (β = -0.124, P = 0.0389), and time (β = 0.003, P = 0.0331), were all significantly associated with Hb change. Increased diuretic dose and weight change were significantly inversely associated with changes in Hb. ESA administration and dose were not significant determinants of absolute BP or changes in BP from baseline.

DISCUSSION

In addition to ESA dose and duration of therapy, factors indicative of volume status including weight and diuretic use are determinants of hemoglobin levels in HF subjects.

CONCLUSION

The currently employed dosing algorithm, which adjusts the administration of ESA based on the absolute hemoglobin and weekly change in hemoglobin increases Hb with relatively a low weekly dose of ESA without significant effects on BP.

Red blood cell transfusion following burn

A severe burn will significantly alter haematologic parameters, and manifest as anaemia, which is commonly found in patients with greater than 10% total body surface area (TBSA) involvement. Maintaining haemoglobin and haematocrit levels with blood transfusion has been the gold standard for the treatment of anaemia for many years. While there is no consensus on when to transfuse, an increasing number of authors have expressed that less blood products should be transfused. Current transfusion protocols use a specific level of haemoglobin or haematocrit, which dictates when to transfuse packed red blood cells (PRBCs). This level is known as the trigger. There is no one 'common trigger' as values range from 6 g dl(-1) to 8 g dl(-1) of haemoglobin. The aim of this study was to analyse the current status of red blood cell (RBC) transfusions in the treatment of burn patients, and address new information regarding burn and blood transfusion management. Analysis of existing transfusion literature confirms that individual burn centres transfuse at a lower trigger than in previous years. The quest for a universal transfusion trigger should be abandoned. All RBC transfusions should be tailored to the patient's blood volume status, acuity of blood loss and ongoing perfusion requirements. We also focus on the prevention of unnecessary transfusion as well as techniques to minimise blood loss, optimise red cell production and determine when transfusion is appropriate.

The effect of erythropoietin on exercise capacity, left ventricular remodeling, pressure-volume relationships, and quality of life in older patients with anemia and heart failure with preserved ejection fraction

A prospective, open-label, 3-month study was conducted to evaluate the feasibility and short-term clinical effect of subcutaneous erythropoietin injections in patients with anemia and heart failure with preserved ejection fraction (ejection fraction, 55%+/-2%). Using a dose-adjusted algorithm to effect a rate of rise in hemoglobin not to exceed 0.4 g/dL /wk, hemoglobin (10.8+/-0.3 to 12.2+/-0.3 g/dL) and red blood cell volume (1187+/-55 to 1333+/-38 mL) increased with an average weekly dose of 3926 units. Functional measures increased from baseline (6-minute walk test [289+/-24 to 331+/-22 m], exercise time [432+/-62 to 571+/-51 s], and peak oxygen consumption [8.2+/-0.7 to 9.4+/-0.9 mL/kg/min], all P<.05). End-diastolic volume declined significantly (8% volumetric decrease, 108+/-3 to 100+/-3 mL, P =.03), but there were no significant changes in left ventricular mass or estimated left ventricular end-diastolic pressure. Pressure-volume analysis demonstrated a reduction in ventricular capacitance at an end-diastolic pressure of 30 mm Hg without significant changes in contractile state.

Total haemoglobin mass but not cardiac volume adapts to long-term endurance exercise in highly trained spinal cord injured athletes

The oxygen transport system is an important component in the limitation of endurance performance in able-bodied and paraplegic athletes. The aim of the present study was to investigate the total haemoglobin mass (tHb, carbon monoxide rebreathing method) and cardiac volume (HV, echocardiography) in 25 highly endurance trained male spinal cord injured (mainly paraplegic) athletes (SCI-TRAINED) and to compare the results with those of 10 untrained spinal cord injured controls (SCI-UNTRAINED) and in 25 able-bodied elite endurance athletes (TRAINED). tHb and tHb/kg were higher in SCI-TRAINED than in SCI-UNTRAINED (748 +/- 110 vs. 629 +/- 209 g (464 +/- 68 vs. 390 +/- 130 mmol) (mean +/- SD), P = 0.02 and 10.3 +/- 1.3 vs. 7.9 +/- 2.0 g/kg (6.4 +/- 0.8 vs. 4.9 +/- 1.2 mmol/kg), P < 0.0001), while HV and HV/kg showed no significant differences between the two groups (765 +/- 93 vs. 793 +/- 164 ml and 10.6 +/- 1.4 vs. 10.3 +/- 2.5 ml/kg). No difference between SCI-TRAINED and TRAINED was found for septal diameter (9.5 +/- 1.0 mm vs. 9.7 +/- 0.7 mm). However, tHb and tHb/kg in SCI-TRAINED was lower than in TRAINED [896 +/- 123 g (556 +/- 76 mmol), P = 0.0003 and 12.6 +/- 1.3 g/kg (7.8 +/- 0.8 mmol), P < 0.0001]. In spinal cord injured athletes, tHb but not HV adapts moderately to chronic endurance exercise, although tHb in spinal cord injured athletes does not reach the level of able-bodied-trained persons.