Pseudohyponatremia in Acute Liver Disease

Hyponatremia in the Context of Liver Disease

Hyponatremia is common in patients with liver disease and is associated with increased mortality, morbidity, and a reduced quality of life. In liver transplantation, the inclusion of hyponatremia in organ allocation scores has reduced waitlist mortality. Portal hypertension and the resulting lowering of the effective arterial blood volume are important pathogenetic factors, but in most patients with liver disease, hyponatremia is multifactorial. Treatment requires a multifaceted approach that tries to reduce electrolyte-free water intake, restore urinary dilution, and increase nonelectrolyte solute excretion. Albumin therapy for hyponatremia is a peculiarity of advanced liver disease. Its use appears to be increasing, while the vaptans are currently only given in selected cases. Osmotic demyelination is a special concern in patients with liver disease. Serial checks of serum sodium concentrations and urine volume monitoring are mandatory.

Use of therapeutic plasma exchange to remove lipoprotein X in a patient with vanishing bile duct syndrome presenting with cholestasis, pseudohyponatremia, and hypercholesterolemia: A case report and review of literature

INTRODUCTION

Lipoprotein X (Lp-X) is an abnormal lipoprotein found in multiple disease conditions, including liver dysfunction and cholestasis. High Lp-X concentrations can interfere with some laboratory testing that may result in spurious results. The detection of Lp-X can be challenging, and there is currently a lack of consensus regarding the management of Lp-X other than treating the underlying disease.

CASE PRESENTATION

A 42-year-old female with Hodgkin's lymphoma treated with dexamethasone, high dose cytarabine and cisplatin and vanishing bile duct syndrome confirmed by liver biopsy presented with cholestasis, pseudohyponatremia (sodium, 113 mmol/L; reference range 136-146 mmL/L; serum osmolality, 303 mOsm/kg), and hypercholesterolemia (> 2800 mg/dL, reference range < 200 mg/dL). Lp-X was confirmed by lipoprotein electrophoresis (EP). Although she did not manifest any specific signs or symptoms, therapeutic plasma exchange (TPE) was initiated based on laboratory findings of extreme hypercholesterolemia, spuriously abnormal serum sodium, and HDL values, and the potential for short- and long-term sequelae such as hyperviscosity syndrome, xanthoma, and neuropathy. During the hospitalization, she was treated with four 1.0 plasma volume TPE over 6 days using 5% albumin for replacement fluid. After the first TPE, total cholesterol (TC) decreased to 383 mg/dL and sodium was measured at 131 mmol/L. The patient was transitioned into outpatient maintenance TPE to eliminate the potential of Lp-X reappearance while the underlying disease was treated. Serial follow-up laboratory testing with lipoprotein EP showed the disappearance of Lp-X after nine TPEs over a 10-week period.

LITERATURE REVIEW

There are seven and four case reports of Lp-X treated with TPE and lipoprotein apheresis (LA), respectively. While all previous case reports showed a reduction in TC levels, none had monitored the disappearance of Lp-X after completing a course of therapeutic apheresis.

CONCLUSION

Clinicians should have a heightened suspicion for the presence of abnormal Lp-X in patients with cholestasis, hypercholesterolemia, and pseudohyponatremia. Once Lp-X is confirmed by lipoprotein EP, TPE should be initiated to reduce TC level and remove abnormal Lp-X. Most LA techniques are not expected to be beneficial since Lp-X lacks apolipoprotein B. Therefore, we suggest that inpatient course of TPE be performed every other day until serum sodium, TC and HDL levels become normalized. Outpatient maintenance TPE may also be considered to keep Lp-X levels low while the underlying disease is treated. Serum sodium, TC, and HDL levels should be monitored while on maintenance TPE.

A High-Throughput NMR Method for Lipoprotein-X Quantification

Lipoprotein X (LP-X) is an abnormal cholesterol-rich lipoprotein particle that accumulates in patients with cholestatic liver disease and familial lecithin-cholesterol acyltransferase deficiency (FLD). Because there are no high-throughput diagnostic tests for its detection, a proton nuclear magnetic resonance (NMR) spectroscopy-based method was developed for use on a clinical NMR analyzer commonly used for the quantification of lipoproteins and other cardiovascular biomarkers. The LP-X assay was linear from 89 to 1615 mg/dL (cholesterol units) and had a functional sensitivity of 44 mg/dL. The intra-assay coefficient of variation (CV) varied between 1.8 and 11.8%, depending on the value of LP-X, whereas the inter-assay CV varied between 1.5 and 15.4%. The assay showed no interference with bilirubin levels up to 317 mg/dL and was also unaffected by hemolysis for hemoglobin values up to 216 mg/dL. Samples were stable when stored for up to 6 days at 4 °C but were not stable when frozen. In a large general population cohort (n = 277,000), LP-X was detected in only 50 subjects. The majority of LP-X positive cases had liver disease (64%), and in seven cases, had genetic FLD (14%). In summary, we describe a new NMR-based assay for LP-X, which can be readily implemented for routine clinical laboratory testing.

Pseudohyponatremia: Mechanism, Diagnosis, Clinical Associations and Management

Pseudohyponatremia remains a problem for clinical laboratories. In this study, we analyzed the mechanisms, diagnosis, clinical consequences, and conditions associated with pseudohyponatremia, and future developments for its elimination. The two methods involved assess the serum sodium concentration ([Na]_S) using sodium ion-specific electrodes: (a) a direct ion-specific electrode (ISE), and (b) an indirect ISE. A direct ISE does not require dilution of a sample prior to its measurement, whereas an indirect ISE needs pre-measurement sample dilution. [Na]_S measurements using an indirect ISE are influenced by abnormal concentrations of serum proteins or lipids. Pseudohyponatremia occurs when the [Na]_S is measured with an indirect ISE and the serum solid content concentrations are elevated, resulting in reciprocal depressions in serum water and [Na]_S values. Pseudonormonatremia or pseudohypernatremia are encountered in hypoproteinemic patients who have a decreased plasma solids content. Three mechanisms are responsible for pseudohyponatremia: (a) a reduction in the [Na]_S due to lower serum water and sodium concentrations, the electrolyte exclusion effect; (b) an increase in the measured sample's water concentration post-dilution to a greater extent when compared to normal serum, lowering the [Na] in this sample; (c) when serum hyperviscosity reduces serum delivery to the device that apportions serum and diluent. Patients with pseudohyponatremia and a normal [Na]_S do not develop water movement across cell membranes and clinical manifestations of hypotonic hyponatremia. Pseudohyponatremia does not require treatment to address the [Na]_S, making any inadvertent correction treatment potentially detrimental.

Pseudohyponatraemia caused by acute pancreatitis-derived hypertriglyceridaemia

We report a case of pseudohyponatraemia due to severe hypertriglyceridaemia-induced acute pancreatitis, stemming from unknown diabetes. A woman in her late 30s was admitted to the local hospital by her general practitioner due to severe hyponatraemia (116 mmol/L) and upper abdominal pain. At admission to the hospital, there was a discrepancy of 19 mmol/L between arterial and venous sodium, along with severe hypertriglyceridaemia and hypercholesterolaemia. Pancreatitis was diagnosed using a CT scan. The patient received plasmapheresis which significantly reduced triglycerides, and venous plasma sodium was normalised indicating pseudohyponatraemia at admission. Finally, a haemoglobin A1c of 83 mmol/mol was found. Diabetes was diagnosed, and insulin was initiated.

Hyponatremia in Patients with Hematologic Diseases

Hyponatremia is the most common electrolyte disorder in clinical practice and is associated with increased morbidity and mortality. It is frequently encountered in hematologic patients with either benign or malignant diseases. Several underlying mechanisms, such as hypovolemia, infections, toxins, renal, endocrine, cardiac, and liver disorders, as well as the use of certain drugs appear to be involved in the development or the persistence of hyponatremia. This review describes the pathophysiology of hyponatremia and discusses thoroughly the contributing factors and mechanisms that may be encountered specifically in patients with hematologic disorders. The involvement of the syndrome of inappropriate antidiuretic hormone (SIADH) secretion and renal salt wasting syndrome (RSWS) in the development of hyponatremia in such patients, as well as their differential diagnosis and management, are also presented. Furthermore, the distinction between true hyponatremia and pseudohyponatremia is explained. Finally, a practical algorithm for the evaluation of hyponatremia in hematologic patients, as well as the principles of hyponatremia management, are included in this review.

Electrolyte and Acid-Base Disturbances in End-Stage Liver Disease: A Physiopathological Approach

Electrolyte and acid-base disturbances are frequent in patients with end-stage liver disease; the underlying physiopathological mechanisms are often complex and represent a diagnostic and therapeutic challenge to the physician. Usually, these disorders do not develop in compensated cirrhotic patients, but with the onset of the classic complications of cirrhosis such as ascites, renal failure, spontaneous bacterial peritonitis and variceal bleeding, multiple electrolyte, and acid-base disturbances emerge. Hyponatremia parallels ascites formation and is a well-known trigger of hepatic encephalopathy; its management in this particular population poses a risky challenge due to the high susceptibility of cirrhotic patients to osmotic demyelination. Hypokalemia is common in the setting of cirrhosis: multiple potassium wasting mechanisms both inherent to the disease and resulting from its management make these patients particularly susceptible to potassium depletion even in the setting of normokalemia. Acid-base disturbances range from classical respiratory alkalosis to high anion gap metabolic acidosis, almost comprising the full acid-base spectrum. Because most electrolyte and acid-base disturbances are managed in terms of their underlying trigger factors, a systematic physiopathological approach to their diagnosis and treatment is required.

Osmotic Pressure in Clinical Medicine with an Emphasis on Dialysis

Since the beginning of life of the first multicellular organisms, the preservation of a physiologic milieu for every cell in the organism has been a critical requirement. A particular range of osmolality of the body fluids is essential for the maintenance of cell volume. In humans the stability of electrolyte concentrations and their resulting osmolality in the body fluids is the consequence of complex interactions between cell membrane functions, hormonal control, thirst, and controlled kidney excretion of fluid and solutes. Knowledge of these mechanisms, of the biochemical principles of osmolality, and of the relevant situations occurring in disease is of importance to every physician. This comprehensive review summarizes the major facts on osmolality, its relation to electrolytes and other solutes, and its relevance in physiology and in disease states with a focus on dialysis-related considerations.

Approach to the Patient With a Negative Anion Gap

When anion gap calculation generates a very small or negative number, an explanation must be sought. Sporadic (nonreproducible) measurement errors and systematic (reproducible) laboratory errors must be considered. If an error is ruled out, 2 general possibilities exist. A true anion gap reduction can be generated by either reduced concentrations of unmeasured anions such as albumin or increased concentrations of unmeasured cations such as magnesium, calcium, or lithium. This teaching case describes a patient with aspirin (salicylate) poisoning whose anion gap was markedly reduced (-47 mEq/L). The discussion systematically reviews the possibilities and provides the explanation for this unusual laboratory result.

Predictors of hepatorenal syndrome in alcoholic liver cirrhosis

BACKGROUND

Alcoholic liver disease is a major cause of liver cirrhosis and the hepatorenal syndrome is a serious complication. Risk factors for hepatorenal syndrome (HRS) in alcoholic liver cirrhosis are not entirely explored.

AIM

To assess the risk factors for hepatorenal syndrome in alcoholic liver cirrhosis.

PATIENTS AND METHODS

Consecutive patients with alcoholic liver disease were followed for two months, development of renal failure, classified either as HRS or renal failure not fulfilling criteria of HRS, was the main outcome.

RESULTS

Of 171 patients, 14 (8.2%) developed HRS and 13 (7.6%), renal failure not fulfilling the HRS criteria. A significant difference was found between patients with and without HRS in serum sodium (131.1±3.8 vs. 135.7±5.2; P = 0.003), creatinine, (94.1±26.8 vs. 80.3±20.2; P < 0.001), albumin (23.5±4.9 vs. 29.9±5.8; P < 0.001), INR (1.76±0.45 vs. 1.44±0.41; P < 0.001), bilirubin (252.3±179.4 vs. 91.2±101.0; P < 0.001), MELD (23±6 vs 15±5; P < 0.001) and MELD-Na score (27±5 vs. 18±6; P < 0.001). Multivariate analysis adjusted for sex and age showed that sodium together with creatinine are the strongest HRS predictors, followed by bilirubin with respective odds´ ratios (95% CI) of 1.041 (1.012-1.072) for creatinine, 0.870 (0.766-0.988) for serum sodium and 1.005 (1.001-1.010) for serum bilirubin.

CONCLUSION

Serum levels of sodium, creatinine and bilirubin are important predictors of the hepatorenal syndrome.

Extreme hypercholesterolemia presenting with pseudohyponatremia - a case report and review of the literature

Pseudohyponatremia has been reported in association with severe hypertriglyceridemia and hyperparaproteinemia, but its association with severe hypercholesterolemia is not well-known. We report a 43-year-old woman with refractory primary biliary cirrhosis who presented with asymptomatic hyponatremia (121 mmol/L; normal range: 135-145 mmol/L). She was ultimately found to have a total serum cholesterol level of 2415 mg/dL (normal range: 120-199 mg/dL) - secondary to accumulation of lipoprotein-X-causing pseudohyponatremia. The diagnosis was confirmed by measurement of serum osmolality (296 mOsm/kg H2O; normal range: 270-300 mOsm/kg H2O) and serum sodium by direct potentiometry (141 mmol/L). Furthermore, following 16 sessions of plasmapheresis over a 4-month period, there was marked lowering of serum cholesterol to 200 mg/dL and normalization of serum sodium (139 mmol/L) as measured by indirect potentiometry. This case shows that extreme hypercholesterolemia from elevation of lipoprotein-X particles in cholestasis can be a rare cause of pseudohyponatremia. It highlights the need to measure serum sodium with direct potentiometry in the setting of extreme hypercholesterolemia and consider this possibility before initiating treatment of hyponatremia.