Pseudo-anion gap metabolic acidosis from severe hypertriglyceridemia corrected by plasma exchange
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BACKGROUND: Falsely low or even unmeasurable serum bicarbonate has been described in patients with severe hypertriglyceridemia or paraproteinemia. This phenomenon, known as pseudo-hypobicarbonatemia, is believed to be due to interference by these components when the commonly used enzymatic assay is utilized for serum bicarbonate measurement. The calculated bicarbonate derived from blood gas machines is not affected. This can lead to a misdiagnosis of a severe anion gap metabolic acidosis along with an extensive and expensive work-up. CASE PRESENTATIONS: We review a series of 5 patients with severe hypertriglyceridemia who presented with pseudo-hypobicarbonatemia and an elevated anion gap metabolic acidosis. Membrane-based therapeutic plasma exchange was utilized. RESULTS: Following aggressive lowering of the triglycerides, there was an immediate resolution of the pseudo-hypobicarbonatemia and anion gap metabolic acidosis. CONCLUSION: Recognition of lipemic serum in the setting of an otherwise unexplained anion gap metabolic acidosis should prompt the clinician to obtain a blood gas sample for true determination of the acid-base status. Doing so may avoid an extensive and expensive metabolic work-up.

Risk of percutaneous renal biopsy of native kidneys in the evaluation of acute kidney injury.

BACKGROUND: Percutaneous renal biopsy (PRB) of native kidneys (NKs) to better understand and treat acute kidney injury (AKI) is being advocated, but little is known about the risk of complications. METHODS: We performed a retrospective study of PRB of NKs in 955 adults from 1991 to 2015 at an academic medical center with real-time ultrasound and automated biopsy needles. Patients undergoing PRB for evaluation of AKI (n = 160) were compared with 795 patients biopsied for other reasons (not-AKI) for postbiopsy complications [need for transfusion of packed red blood cells (PRBCs), an interventional radiologic or surgical procedure, readmission or death]. RESULTS: Patients biopsied for AKI were older (58 ± 16 versus 44 ± 16 years; P < 0.0001), with a higher serum creatinine (SCr) (4.5 ± 2.7 versus 1.8 ± 1.6 mg/dL; P < 0.0001) and lower hemoglobin (Hgb) (10.4 ± 1.7 versus 12.1 ± 2.1; P < 0.0001) and a greater proportion had an abnormal bleeding time (12.5% versus 7.4%, P 0.04), partial thromboplastin time (15.2% versus 5.3%, P < 0.0001) and/or prothrombin time (27.0% versus 12.8%; P < 0.0001) compared with not-AKI patients. Complications post-PRB were significantly greater in patients biopsied for AKI {11.3% versus 6.7%; P=0.04; odds ratio [OR] 1.78 [95% confidence interval (CI) 1.01-3.12]} with patients biopsied for AKI requiring more blood transfusions (10.0% versus 5.3%; P 0.02; OR 2.04 (95% CI 1.12-3.74)]. By multivariate analysis, baseline features predictive of a complication were increased SCr and decreased Hgb level, as well as female gender and increased systolic blood pressure. CONCLUSION: Patients biopsied for evaluation of AKI are at greater risk of complications due to increased risk factors.

Membrane-based therapeutic plasma exchange (mTPE): Technical and clinical experience.

Therapeutic plasma exchange (TPE) has long been utilized to manage a variety of immune-mediated diseases. The basic principle relies on removal of circulating pathogenic substances from the bloodstream. Methods of plasma separation include centrifuge (cTPE) and membrane (mTPE). Although mTPE has existed for a few decades, recent advances in developing highly permeable filters that are compatible with currently existing dialysis machines has opened a new frontier. Published data in the area of technical and clinical experience with mTPE is lacking. We report our single center experience of 998 inpatient mTPE treatments performed in 237 patients at a large tertiary care academic center. The most common treatment indication was neurologic. We found a very low incidence of patient-reported complications. Filter clotting without the use of anticoagulation occurred in 7.7% of treatments. Laboratory parameters that significantly changed during the course of therapy included serum potassium, platelet count, and partial thromboplastin time. We found that mTPE can be safely and efficiently performed as an alternative to cTPE, and suggest an individualized approach when prescribing this therapy.

Membrane-based Therapeutic Plasma Exchange: A New Frontier for Nephrologists.

Therapeutic plasma exchange has long been utilized to manage a variety of immune-mediated diseases. The underlying principle is the removal of a circulating pathogenic substance from the plasma and substitution with a replacement fluid. Different methodologies of plasma separation include the use of centrifuge, which relies on the variation in the specific gravity of blood components, and membrane-based separation, which relies on particle size. With advancements in technology and clinical insight into disease pathophysiology, membrane technology has become more biocompatible, safer, and more adaptable to conventional hemodialysis and hemofiltration machines. As such, nephrologists, who are familiar with management of extracorporeal blood purification systems, are increasingly involved with membrane-based plasma separation. This review aims to highlight the technical aspects of membrane-based separation, review the prescription for therapy, and draw comparisons with the centrifuge-based technique when applicable.

Effects of high blood flow and high pre-dilution replacement fluid rates on small solute clearances in hemofiltration.

BACKGROUND/AIMS: In pre-dilution hemofiltration (HF), solute clearance is less than the HF rate. While the amount of this loss is predictable, it has not been validated in high-volume HF associated with high blood flow rates. METHODS: Using isovolemic pre-dilution HF, we studied small solute clearances using combinations of blood flow (Q(B); 150, 250, 350, 450 ml/min) and replacement fluid (RF) flow (Q(RF); 2, 4, 6 l/h) to determine clearance losses we entitled 'measured efficiency' (E(M)). E(M) was compared to predicted efficiency (E(P)) = (Q(B)/Q(B) + Q(RF)). RESULTS: Pre-dilution produced E(M) values of 61-93%. Increases in Q(B) for any Q(RF) and decreases in Q(RF) for any Q(B) increased E(M) over a wide range of Q(B) and Q(RF). E(P) was equivalent to E(M). CONCLUSION: In high-volume pre-dilution HF, E(P) can be used to determine E(M) across a broad range of Q(B) and Q(RF) values. Higher Q(RF) requires higher Q(B) to minimize the attenuating effects of pre-dilution on clearance.

Accelerated venovenous hemofiltration: early technical and clinical experience.

BACKGROUND: Renal replacement therapies other than intermittent hemodialysis are often required in hemodynamically unstable patients. Continuous renal replacement therapies use a slow blood flow rate, necessitating anticoagulation and prolonged treatment times that may create difficulties with staffing and limit patient diagnostic and therapeutic procedures. We developed an alternative strategy based on a higher blood flow rate that allows increased rates of hemofiltration, no anticoagulation, and a shorter ("accelerated") treatment period. We report our technical and clinical experience with accelerated venovenous hemofiltration (AVVH). STUDY DESIGN: Case series. SETTING & PARTICIPANTS: Hemodynamically unstable patients requiring renal replacement therapy in the medical or surgical intensive care unit of an academic medial center. OUTCOMES & MEASUREMENTS: Achieved dose, blood flow rate, mean arterial pressure, serum chemistry test results, patient weight, filter clotting, and patient survival. RESULTS: 100 patients received 457 AVVH treatments (average, 4.1 treatments/patient during 5.6 days). Mean Acute Physiology, Age, and Chronic Health Evaluation II score was 24 +/- 7.1. Treatment consisted of 36 L of predilution hemofiltration during 9 hours. Mean blood flow was 362 mL/min, and net fluid removal was 2.5 L/treatment. Anticoagulation was not used and filter clotting was seen in only 3.3% of treatments. 86% of patients received the prescribed dose. Pre- and post-AVVH chemistry test results showed a significant decrease in blood urea nitrogen (from 69.6 +/- 24.8 to 50.7 +/- 22.0 mg/dL) and serum creatinine levels (from 4.3 +/- 2.0 to 2.9 +/- 1.3 mg/dL). Weight was decreased significantly (from 98.8 +/- 26.4 to 93.4 +/- 23.1 kg). Pre- and post-AVVH mean arterial pressure comparison showed an increase from 72.8 +/- 13.6 to 74.4 +/- 15.2 mm Hg. Patient survival rate was 53%. LIMITATIONS: Retrospective analysis, absence of a comparison group. CONCLUSION: AVVH is an alternate renal replacement therapy for patients in the intensive care unit and appears to provide adequate volume and solute control without the need for anticoagulation. The shorter treatment period offers flexibility for staffing and other patient diagnostic and therapeutic procedures.

The role of calcium antagonists in chronic kidney disease.

PURPOSE OF REVIEW: To review goals of antihypertensive treatment in chronic kidney disease in the context of what role calcium antagonists play toward reducing progression of kidney disease. RECENT FINDINGS: All recently published guidelines recommend a blood pressure goal of less than 130/80 mmHg in patients with chronic kidney disease. Use of calcium antagonists is not recommended as part of the initial armamentarium. Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers, when used in concert with diuretics reduce blood pressure as well as both proteinuria and the rate of decline in the glomerular filtration rate. The evidence for calcium antagonists in this regard is more divergent. Dihydropyridine calcium antagonists, e.g. amlodipine, felodipine, help achieve blood pressure goals and reduce stroke risk. When used with a renin-angiotensin system blocker they do not detract from the benefits of this blockade on slowing progression of kidney disease. Non-dihydropyridine calcium antagonists, e.g. verpamil or diltiazem, decrease proteinuria and in studies with 5 to 6 years follow-up preserve kidney function similarly to angiotensin-converting enzyme inhibitors. The reason for this outcome difference between calcium antagonists is partial preservation of renal autoregulation compared to its obliteration by the dihydropyridine subclass. SUMMARY: Use of calcium antagonists is safe and necessary to achieve blood pressure goals in people with chronic kidney disease. While both subclasses are safe and necessary to achieve blood pressure goals, dihydropyridine calcium antagonists fail to significantly slow the progression of kidney disease among patients with established nephropathy and macroalbuminuria when compared to agents that block the renin-angiotensin system.