Blood volume measured by ultrasound and radioisotope dilution in critically ill subjects

Active Circulating Blood Volume During Hemodialysis: A Bench Model

Intradialytic hypotension due to excessive fluid removal is a common complication of hemodialysis. A bench model was constructed to evaluate quantification of active circulating blood volume (ACBV). The model included a central pump representing the heart and compartments to represent the central and peripheral circulation. A blood oxygenator was used to simulate lung volume and two containers represented fast and slow circulation compartments. A separate dialysis circuit with a blood pump and two ultrasound flow-dilution probes was incorporated. Vascular access was simulated with both a shunt (fistula or graft) and a central venous catheter. Hypertonic saline (5%) was circulated in the system. A bolus of isotonic saline was introduced in the dialysis circuit, which dispersed through the physiologic model. ACBV was measured by comparing the baseline dilution curve to the curve as it returned to the probes. To evaluate the sensitivity of this technique, we investigated changing cardiac output, central venous volume, shunt flow, vascular access type, and HD pump flow. Overall percentage error (mean ± SD) across all tests (n = 15 conditions, each in triplicate) was 2.6% ± 7.4%. This study demonstrates the ability to accurately measure ACBV on the bench.

Rapid nuclear medicine blood volume analysis for emergency assessment

Assessment of fluid status can play a critical role in the diagnosis and management of emergent conditions such as trauma, shock, decompensated heart failure, syncope, and hypertension. Unfortunately, common methods are all qualitative and/or indirect, and often inaccurate. With the recent introduction of a modernized method of nuclear medicine blood volume analysis (NM-BVA), offering results in 90 min or less as well as improved precision and ease of performance, this decade-old technique is for the first time a viable tool in the emergent setting. In this review, we discuss the history of NM-BVA, the modern method, and our institution’s experience implementing this method.

Heart Failure Outcomes With Volume-Guided Management

OBJECTIVES

This study performed a retrospective outcome analyses of a large cohort of mixed ejection fraction patients admitted for acute heart failure (HF), whose inpatient care was guided by individual quantitative blood volume analysis (BVA) results.

BACKGROUND

Decongestion strategies in patients hospitalized for HF are based on clinical assessment of volume and have not integrated a quantitative intravascular volume metric.

METHODS

Propensity score control matching analysis was performed in 245 consecutive HF admissions to a community hospital (September 2007 to April 2014; 78 ± 10 years of age; 50% with HF with reduced ejection fraction [HFrEF]; and 30% with Stage 4 chronic kidney disease). Total blood volume (TBV), red blood cell volume (RBCV), and plasma volume (PV) were measured at admission by using iodine-131-labeled albumin indicator-dilution technique. Decongestion strategy targeted a TBV threshold of 6% to 8% above patient-specific normative values. Anemia was treated based on cause. Hematocrit (Hct) measurements were monitored to assess effectiveness of interventions. Control subjects derived from Centers for Medicare and Medicaid Services data were matched 10:1 for demographics, comorbidity, and year of treatment.

RESULTS

Although 66% of subjects had PV expansion, only 37% were hypervolemic (TBV >10% excess). True anemia (RBCV ≥10% deficit) was present in 62% of subjects. Treatment of true anemia without hypervolemia resulted in a rise in peripheral Hct of 2.7 ± 2.9% (p < 0.001), and diuretic treatment of hypervolemia in cases without anemia caused a 4.5 ± 3.9% (p < 0.001) increase in peripheral Hct at 11.3 ± 7.5 days after admission. Subjects had lower 30-day rates of readmission (12.2% vs. 27.7%, respectively; p < 0.001), of 30-day mortality (2.0% vs. 11.1%, respectively; p < 0.001), and of 365-day mortality (4.9% vs. 35.5%, respectively; p < 0.001) but longer lengths of stay (7.3 vs. 5.6 days, respectively; p < 0.001) than control subjects.

CONCLUSIONS

Retrospective outcomes using volume-guided HF therapy versus propensity-matched controls support the benefit of BVA in guiding volume management and reducing death and rehospitalization due to HF.