Diagnostic strategies in disorders of fluid, electrolyte and acid-base homeostasis

Changes in Serum Creatinine Levels Can Help Distinguish Hypovolemic from Euvolemic Hyponatremia

Background and Objectives: Differentiating between hypovolemic (HH) and euvolemic hyponatremia (EH) is crucial for correct diagnosis and therapy, but can be a challenge. We aim to ascertain whether changes in serum creatinine (SC) can be helpful in distinguishing HH from EH. Materials and Methods: Retrospective analysis of patients followed in a monographic hyponatremia outpatient clinic of a tertiary hospital during 1 January 2014−30 November 2019. SC changes during HH and EH from eunatremia were studied. The diagnostic accuracy of the SC change from eunatremia to hyponatremia (∆SC) was analyzed. Results: A total of 122 hyponatremic patients, median age 79 years (70−85), 46.7% women. In total, 70/122 patients had EH, 52/122 HH. During hyponatremia, median SC levels increased in the HH group: +0.18 mg/dL [0.09−0.39, p < 0.001], but decreased in the EH group: −0.07 mg/dL (−0.15−0.02, p < 0.001), as compared to SC in eunatremia. HH subjects presented a higher rate of a positive ∆SC than EH (90.4% vs. 25.7%, p < 0.001). EH subjects presented a higher rate of a negative/null ∆SC than HH (74.3% vs. 9.6%, p < 0.001). ROC curve analysis found an AUC of 0.908 (95%CI: 0.853 to 0.962, p < 0.001) for ∆SC%. A ∆SC% ≥ 10% had an OR of 29.0 (95%CI: 10.3 to 81.7, p < 0.001) for HH. A ∆SC% ≤ 3% had an OR of 68.3 (95%CI: 13.0 to 262.2, p < 0.001) for EH. Conclusions: The assessment of SC changes from eunatremia to hyponatremia can be useful in distinguishing between HH and EH.

Fundamentals of Arterial Blood Gas Interpretation

Acid-base disturbances in patients with cardiopulmonary or other disorders are common and are often misinterpreted or interpreted incompletely. Treating acid-base disorders in greater detail facilitates pathophysiologic understanding and improved therapeutic planning. Understanding the ratiometric relationship between the lungs, which excrete volatile acid as carbon dioxide, and the kidneys, which contribute to maintenance of plasma bicarbonate, allows precise identification of the dominant acid-base disturbance when more than a simple disorder is present and aids in executing a measured treatment response. Concordantly, mapping paired values of the partial pressure of carbon dioxide (PCO₂) and the bicarbonate concentration ([HCO₃ ^-]) on a Cartesian coordinate system visually defines an acid-base disorder and validates the ratiometric methodology. We review and demonstrate the algebraic and logarithmic methods of arterial blood gas analysis through the example of a complex acid-base disorder, emphasizing examination of the PCO₂-to-[HCO₃ ^-] ratio.

Identification of the Causes for Chronic Hypokalemia: Importance of Urinary Sodium and Chloride Excretion

BACKGROUND

Uncovering the correct diagnosis of chronic hypokalemia with potassium (K⁺) wasting from the kidneys or gut can be fraught with challenges. We identified clinical and laboratory parameters helpful for differentiating the causes of chronic hypokalemia.

METHODS

Normotensive patients referred to our tertiary academic medical center for the evaluation of chronic hypokalemia were prospectively enrolled over 5 years. Clinical features, laboratory examinations-including blood and spot urine electrolytes, acid-base status, biochemistries, and hormones-as well as genetic analysis, were determined.

RESULTS

Ninety-nine patients with chronic normotensive hypokalemia (serum K⁺ 2.8 ± 0.4 mmol/L, duration 4.1 ± 0.9 years) were enrolled. Neuromuscular symptoms were the most common complaints. Although Gitelman syndrome (n = 33), Bartter syndrome (n = 10), and distal renal tubular acidosis (n = 12) were the predominant renal tubular disorders, 44 patients (44%) were diagnosed with anorexia/bulimia nervosa (n = 21), surreptitious use of laxatives (n = 11), or diuretics (n = 12). Patients with gastrointestinal causes and surreptitious diuretics use exhibited a female predominance, lower body mass index, and less K⁺ supplementation. High urine K⁺ excretion (transtubular potassium gradient >3, urine K⁺/Cr >2 mmol/mmol) was universally present in patients with renal tubular disorders, but also found in >50% patients with gastrointestinal causes. Of interest, while urine sodium (Na⁺) and chloride (Cl^-) excretions were high and coupled (urine Na⁺/Cl^- ratio ∼1) in renal tubular disorders and "on" diuretics use, skewed or uncoupled urine Na⁺ and Cl^- excretions were found in anorexia/bulimia nervosa and laxatives abuse (urine Na⁺/Cl^- ratio: 5.0 ± 2.2, 0.4 ± 0.2, respectively) and low urine Na⁺ and Cl^- excretions with fixed Na⁺/Cl^- ratios (0.9 ± 0.2) when "off" diuretics.

CONCLUSION

Besides body mass index, sex, and blood acid-base status, integrated interpretation of the urine Na⁺:Cl^- excretion and their ratio is important to make an accurate diagnosis and treatment plan for patients with chronic normotensive hypokalemia.

Preliminary investigation on ultra high diluted B. vulgaris in experimental urolithiasis

PURPOSE

The study focuses on the anti-urolithiasis potential of ultra-diluted homeopathic potency of Berberis vulgaris (B. vulgaris) root bark, commonly used in homeopathic system to treat renal calculi.

METHODOLOGY

B. vulgaris root bark (200c, 20 μl/100 g body weight/day, p.o, for 28 days) was tested in an animal model of urolithiasis. Urolithiasis was induced in male Wistar rats by adding 0.75% ethylene glycol (EG) to drinking water. Urine and serum samples were analyzed for calcium, magnesium, phosphorus, uric acid and creatinine. Enzymic makers of renal damage (alkaline phosphatase, lactate dehydrogenase, leucine aminopeptidase and γ-glutamyl transpeptidase) were assessed in kidney and urine. Renal tissues were analyzed for oxalate content.

RESULTS

Administration of EG to rats increased the levels of the stone-forming constituents calcium, phosphorus and uric acid, in urine. Levels were normalized by B. vulgaris treatment. The decrease in the urolithiasis inhibitor magnesium in urine was prevented by treatment with B. vulgaris. Serum creatinine levels were largely normalized by B. vulgaris treatment. Hyperoxaluria induced renal damage was evident from the decreased activities of tissue marker enzymes and an apparent escalation in their activity in the urine in control animals; this was prevented by B. vulgaris treatment.

CONCLUSION

Homeopathic B. vulgaris root bark has strong anti-urolithiasis potential at ultra-diluted dose.

[Thyrotoxic periodic paralysis: a case series of four patients and literature review]

PURPOSE

Periodic thyrotoxic hypokalemic paralysis (TPP) is a neuromuscular complication of hyperthyroidism. It is more common in young Asian males than in Caucasian and African patients. We report four new cases and review the literature.

CASE REPORTS

Four consecutive patients were diagnosed with TPP. They were all men with a median age of 34.5 years at presentation. Two patients originated from the Philippines, one was African and one was Caucasian ethnic background. They all presented with a paresis or flaccid paralysis, without respiratory failure. Previous similar episodes in their past medical history, the presence of profound hypokalemia (mean serum potassium level of 2 mmol/L) and the presence of clinical and biological signs of hyperthyroidism led to the diagnosis of TPP. All four patients were diagnosed with Graves' disease. Outcome was favourable in all four patients with the symptomatic treatment of TPP and treatment of Graves' disease.

CONCLUSION

TPP is a severe condition, due to a dysfunction of the Na(+)-K(+) ATPase pump. Initial management relies on β-blocker treatment and careful potassium supplementation. Then, medical or surgical etiological treatment of the thyrotoxicosis is essential to prevent a recurrence. The disease is probably underdiagnosed: it must be suspected when a profound hypokaliema resolves very quickly (<12hours); hyperthyroidism should always be included in the differential diagnosis of a paresis associated with hypokalemia.

Efficacy of a mycotoxin binder against dietary fumonisin, deoxynivalenol, and zearalenone in rats

It was hypothesized that a mycotoxin binder, Grainsure E, would inhibit adverse effects of a mixture of fumonisin B1, deoxynivalenol, and zearalenone in rats. For 14 and 28 days, 8-10 Sprague-Dawley rats were fed control diet, Grainsure E (0.5%), toxins (7 μg fumonisin B1/g, 8 μg of deoxynivalenol/g and 0.2 μg of zearalenone/g), toxins (12 μg of fumonisin B1/g, 9 μg of deoxynivalenol/g, and 0.2 μg of zearalenone/g + Grainsure E), or pair-fed to control for food intake of toxin-fed rats. After 28 days, decreased body weight gain was prevented by Grainsure E in toxin-fed female rats, indicating partial protection against deoxynivalenol and fumonisin B1. Two effects of fumonisin B1 were partly prevented by Grainsure E in toxin-fed rats, increased plasma alanine transaminase (ALT) and urinary sphinganine/sphingosine, but sphinganine/sphingosine increase was not prevented in females at the latter time point. Grainsure E prevented some effects of fumonisin B1 and deoxynivalenol in rats.

Evaluation of the proximal tubular function in individuals with primary renal hypouricemia: an NMR-based metabonomic study

Primary renal hypouricemia (PRH) refers to a rare condition of increased renal urate clearance, caused by an isolated inborn error of membrane transport of urate in the renal proximal tubule. Several cases of exercise-induced acute renal failure and urolithiasis have been reported. This is the first study that assessed tubular function in PRH using NMR-based metabonomic urine analysis. The study groups consisted of 36 unrelated asymptomatic subjects with PRH, defined as serum uric acid levels (sUA) <2.5 mg/dL and fractional excretion of uric acid (FEUA) >10%, after exclusion of diseases and drugs that may affect urate homeostasis, and 39 sex and age-matched healthy individuals with normal sUA levels (>4.0 mmol/L) and FEUA<10%. Individuals with primary hypouricemia presented similar biochemical profiles to the controls without significant differences with regard to FE of electrolytes and renal threshold for phosphate excretion. Individuals with primary hypouricemia were differentiated from healthy individuals in the orthogonal signal correction/partial least-squares-discriminant analysis models of the NMR data with a statistically significant separation. The components that contributed to this separation were the lower levels of hippurate, creatinine, and trimethylaminoxide, and the higher levels of phenylalanine, alanine, glycine, glutamate, acetate, and of an unidentified metabolite (3.3 ppm) observed in hypouricemic subjects compared with controls. Primary hypouricemia, though considered an isolated renal tubular defect, is often associated with a more generalized proximal tubular disorder that mimics a partial Fanconi syndrome.

Diagnosis and management of hyponatraemia in hospitalised patients

Hyponatraemia is a commonly encountered electrolyte abnormality in hospitalised patients and is associated with significant morbidity and mortality. The fact that most cases of hyponatraemia are the result of water imbalance rather than sodium imbalance underscores the role of antidiuretic hormone (ADH) in the pathophysiology. Hyponatraemia can be classified according to the measured plasma osmolality as isotonic, hypertonic or hypotonic. Hyponatraemia with a normal plasma osmolality usually indicates pseudohyponatraemia, while hyponatraemia because of a high plasma osmolality is typically caused by hyperglycaemia. After excluding isotonic and hypertonic causes, hypotonic hyponatraemia is further classified according to the volume status of the patient as hypovolaemic, hypervolaemic or euvolaemic. Hypovolaemic hyponatraemia is accompanied by extracellular fluid (ECF) volume deficit, while hypervolaemic hyponatraemia manifests with ECF volume expansion. The syndrome of inappropriate ADH (SIADH) should be suspected in any patient with euvolaemic hyponatraemia with a urine osmolality above 100 mOsm/kg and urine sodium concentration above 40 mEq/l. In the management of any hyponatraemia regardless of the patient's volume status, it is advised to restrict free water and hypotonic fluid intake. Hypertonic saline and vasopressin antagonists can be used to correct symptomatic hyponatraemia. The rate of correction is dependent upon the duration, degree of hyponatraemia and the presence or absence of symptoms. Symptomatic acute hyponatraemia (< 48 h) is a medical emergency requiring rapid correction to prevent the worsening of brain oedema. In asymptomatic patients with chronic hyponatraemia (> 48 h or unknown duration), fluid restriction and close monitoring alone are sufficient, while a slow correction by 0.5 mEq/l/h may be attempted in symptomatic patients. Excessive rapid correction should be avoided in both acute and chronic hyponatraemia, because it can lead to irreversible neurological complications including central osmotic demyelination.

Metabolic acid-base disorders in the critical care unit

The recognition and management of acid-base disorders is a commonplace activity in the critical care unit, and the role of weak and strong acids in the genesis of metabolic acid-base disorders is reviewed. The clinical approach to patients with metabolic alkalosis and metabolic acidosis is discussed in this article.

[Rhabdomyolysis with major hypokalemia secondary to chronic glycyrrhizic acid ingestion]

Intoxication by glycyrrhizic acid is a well-known cause of the apparent mineralocorticoid excess syndrome. It causes hypokalemia by inhibiting the enzyme 11-beta-hydroxysteroid dehydrogenase. We report a case of hypokalemic rhabdomyolysis secondary to chronic glycyrrhizic acid intoxication.

Absence of SLC22A12 gene mutations in Greek Caucasian patients with primary renal hypouricaemia

OBJECTIVE

Primary renal hypouricaemia is a hereditary clinical disorder characterized by increased renal urate clearance due to isolated renal tubular defect of uric acid transport. There have been only a few studies on primary renal hypouricaemia in Caucasian populations. Defects in the SLC22A12 gene, which encodes the renal urate transporter URAT1, have been reported to be related to the disease pathogenesis. This study was undertaken to elucidate whether SLC22A12 gene mutations are responsible for low serum uric acid levels in Greek people.

MATERIAL AND METHODS

Nine Greek Caucasian subjects with primary renal hypouricaemia were included in the study. All had serum uric acid less than 2.5 mg dL(-1) (0.14 mmol L(-1)), fractional excretion of uric acid more than 10% and no other known causes of hypouricaemia. Mutation analysis of the SLC22A12 gene was performed.

RESULTS

No mutation was found--only the previously reported silent polymorphism 1246T > C (His 42His) in exon 2 of the SLC22A12 gene.

CONCLUSIONS

No previously reported mutation of URAT1 was associated with primary renal hypouricaemia in Greek subjects.

Cellular magnesium acquisition: an anomaly in embryonic cation homeostasis

The intracellular dominance of magnesium ion makes clinical assessment difficult despite the critical role of Mg(++) in many key functions of cells and enzymes. There is general consensus that serum Mg(++) levels are not representative of the growing number of conditions for which magnesium is known to be important. There is no consensus method or sample source for testing for clinical purposes. High intracellular Mg(++) in vertebrate embryos results in part from interactions of cations which influence cell membrane transport systems. These are functionally competent from the earliest stages, at least transiently held over from the unfertilized ovum. Kinetic studies with radiotracer cations, osmolar variations, media lacking one or more of the four biological cations, Na(+), Mg(++), K(+), and Ca(++), and metabolic poison 0.05 mEq/L NaF, demonstrated that: (1) all four cations influence the behavior of the others, and (2) energy is required for uptake and efflux on different time scales, some against gradient. Na(+) uptake is energy dependent against an efflux gradient. The rate of K(+) loss is equal with or without fluoride, suggesting a lack of an energy requirement at these stages. Ca(++) efflux took twice as long in the presence of fluoride, likely due in part to intracellular binding. Mg(++) is anomalous in that early teleost vertebrate embryos have an intracellular content exceeding the surrounding sea water, an isolated unaffected yolk compartment, and a clear requirement for energy for both uptake and efflux. The physiological, pathological, and therapeutic roles of magnesium are poorly understood. This will change: (1) when (28)Mg is once again generally available at a reasonable cost for both basic research and clinical assessment, and (2) when serum or plasma levels are determined simultaneously with intracellular values, preferably as part of complete four cation profiles. Atomic absorption spectrophotometry, energy-dispersive x-ray analysis, and inductively coupled plasma emission spectroscopy on sublingual mucosal and peripheral blood samples are potential methods of value for coordinated assessments.

Electrolyte disturbances in patients with hyponatremia

OBJECT

Electrolyte abnormalities are frequently observed in patients with hyponatremia. The aim of this study was to determine the incidence of various electrolyte abnormalities encountered in hyponatremic patients admitted to an internal medicine clinic, as well as to investigate the possible pathogenetic mechanisms responsible for these abnormalities.

PATIENTS AND METHODS

We prospectively studied 204 adult patients who either on admission to our clinic or during their hospitalization were found to have hyponatremia.

RESULTS

Ninety-two patients (45.5%) had at least one additional electrolyte abnormality. Hypophosphatemia was the most frequent electrolyte disorder observed (35 patients, 17%). Hypokalemia was seen in 32 patients (15.8%), hypomagnesemia in 31 patients (15.2%) and hyperkalemia in 12 patients (5.9%). Moreover, 5 patients (2.5%) had hyperphosphatemia, 4 patients (1.9%) exhibited hypermagnesemia, 3 patients (1.4%) had hypercalcemia, and 6 patients (2.9%) had true hypocalcemia. There were no statistically significant differences regarding the incidence of these electrolyte abnormalities (as a whole) between the main subgroups of hyponatremic patients (diuretic-induced, syndrome of inappropriate antidiuretic hormone, hypovolemia-induced and edematous state-related). However, hypokalemia and hypomagnesemia were more frequently observed in patients with diuretic-induced hyponatremia, while hyperkalemia was more frequently seen in edematous state-related hyponatremia.

CONCLUSIONS

Additional electrolyte abnormalities are frequently encountered in patients with hyponatremia of any origin admitted to an internal medicine clinic.

Phenotypic and molecular genetic aspects of pseudohypoparathyroidism type Ib in a Greek kindred: evidence for enhanced uric acid excretion due to parathyroid hormone resistance

The predominant feature of pseudohypoparathyroidism (PHP) is renal resistance to PTH. Pseudohypoparathyroidism type Ia (PHP-Ia) is caused by maternally inherited heterozygous mutations in the GNAS exons encoding the alpha-subunit of the stimulatory G protein (Gsalpha). Besides PTH resistance, PHP-Ia patients have Albright's hereditary osteodystrophy and often display resistance to additional hormones. Patients with PHP-Ib lack features of Albright's hereditary osteodystrophy, and PTH resistance is associated with loss of methylation at the maternal GNAS exon A/B. Most individuals with the autosomal dominant form of PHP-Ib have a 3-kb microdeletion within STX16 approximately 220 kb upstream of exon A/B. Here we report on the clinical and genetic aspects of a Greek PHP-Ib kindred with four affected members and three obligate carriers, who had the 3-kb deletion within STX16. Symptomatic hypocalcemia was present only in the proband, but PTH was elevated in all members who had inherited the 3-kb deletion maternally. In all affected family members, urinary phosphate excretion was normal, but 1,25-dihydroxyvitamin D levels were diminished. These findings confirm previous data regarding patient to patient variation in disease severity for autosomal dominant PHP-Ib. Furthermore, affected individuals displayed hypouricemia with increased fractional excretion of uric acid, suggesting possible involvement of PTH in the renal handling of this metabolite.

Cardiovascular and renal disease in the adolescent guinea pig after chronic placental insufficiency

OBJECTIVE

The aim of this study was to determine the long-term effects of chronic placental insufficiency on the metabolic state and organ structure in the fetal and adolescent guinea pig.

STUDY DESIGN

The maternal uterine artery was ligated at day 28-30 to reduce placental function and restrict fetal growth. Whole body and tissue weights and plasma metabolites were determined at 60 days of gestation and 8 weeks of age; tissue structure was determined at the latter age in restricted and control offspring.

RESULTS

Fetal growth restriction increased fibrosis in the heart and kidneys (P < .05), increased aortic wall thickening (P < .01), reduced the number of glomeruli in the kidneys (P < .05), and increased the plasma urea and chloride in adolescent offspring.

CONCLUSION

This study demonstrates that diseases in the heart, aorta, and kidneys that result from an adverse prenatal environment are evident at adolescence and may contribute to subsequent adult disease.

A simple and rapid approach to hypokalemic paralysis

Hypokalemia with paralysis (HP) is a potentially reversible medical emergency. It is primarily the result of either hypokalemic periodic paralysis (HPP) caused by an enhanced shift of potassium (K(+)) into cells or non-HPP resulting from excessive K(+) loss. Failure to make a distinction between HPP and non-HPP could lead to improper management. The use of spot urine for K(+) excretion rate and evaluation of blood acid-base status could be clinically beneficial in the diagnosis and management. A very low rate of K(+) excretion coupled with the absence of a metabolic acid-base disorder suggests HPP, whereas a high rate of K(+) excretion accompanied by either metabolic alkalosis or metabolic acidosis favors non-HPP. The therapy of HPP requires only small doses of potassium chloride (KCl) to avoid rebound hyperkalemia. In contrast, higher doses of KCl should be administered to replete the large K(+) deficiency in non-HPP.

Hypouricemia in individuals admitted to an inpatient hospital-based facility

BACKGROUND

Decreased serum uric acid levels resulting from renal urate wasting occasionally are reported in hospitalized patients because of isolated or generalized proximal tubular damage. There are limited recent findings with regard to the incidence and cause of hypouricemia in patients admitted to an internal medicine clinic. The aim of this study is to examine the prevalence of hypouricemia in individuals admitted to our inpatient hospital-based facility and identify underlying causes and pathogenetic mechanisms and any association of hypouricemia and uricosuria with other tubular defects.

METHODS

A total of 7,250 serum urate measurements were available on patients' admission. Hypouricemia is defined as a serum urate level less than 2.5 mg/dL (149 micromo/L). In all hypouricemic cases, a detailed clinical and laboratory investigation was performed.

RESULTS

Hypouricemia was found in 90 patients (1.24%). In all except one patient, hypouricemia was associated with inappropriate uricosuria (urate fractional excretion [FE] > 10%; range, 10.8% to 94%). There was an inverse correlation between serum uric acid level and its FE (r = -0.73; P < 0.0001). The most common causes of hypouricemia were obstructive jaundice of any cause (n = 18), solid or hematologic neoplasias (n = 17), diabetes mellitus (n = 12), drugs affecting urate homeostasis (n = 10), and intracranial diseases (n = 8). Seventeen patients with hypouricemia showed one or more other manifestations of proximal tubular damage, such as glucosuria, inappropriate phosphaturia leading to hypophosphatemia, and kaliuria resulting in hypokalemia.

CONCLUSION

Hypouricemia caused by inappropriate uricosuria is not rare in patients admitted to an internal medicine clinic, is related to underlying diseases, and may be associated with other abnormalities of proximal tubular function.

Adaptation of an automated assay for determination of beta-hydroxybutyrate in dogs using a random access analyzer

An automated method for measuring beta-hydroxybutyrate was adapted to the Ciba-Corning 550 Express trade mark random access analyzer. The assay was based on a kinetic reaction utilizing hydroxybutyrate-dehydrogenase. Beta-hydroxybutyrate concentration (mmol/L) was calculated ratiometrically using a 1.0 mmol/l standard. Canine serum, plasma, and urine were used without prior deproteinization and only a 30-microliter sample was required. The method demonstrated good linearity between 0 to 2 mmol/l of beta-hydroxybutyrate. Analytical recovery (accuracy) within these concentrations ranged from 85.8 to 113.3%. Both within-run and day-to-day precision were determined, as was specificity of the assay in the presence of a variety of interfering substances. The automated assay was rapid and economical, with reagent stability maintained for at least 2 weeks at 4 degrees C. This assay can readily be applied toward the assessment of ketoacidosis in dogs, and with further validation, other species.

Hypomagnesemia and concurrent acid-base and electrolyte abnormalities in patients with congestive heart failure

BACKGROUND

Patients with severe decompensated congestive heart failure (CHF) commonly exhibit acid-base and electrolyte disturbances mainly due to the activation of several neurohumoral mechanisms as well as to drugs regularly used in this population. Magnesium deficit is not infrequently observed in CHF patients but its pathophysiology remains less well-studied as compared with other electrolyte alterations, such as hypokalemia. However, there is evidence that early detection and correction of magnesium abnormalities could obviate potentially deleterious arrhythmogenic effects.

AIM

To assess the incidence of magnesium level disorders and analyze the underlying pathophysiological mechanisms in patients with CHF.

METHODS

Eighty-six consecutive CHF patients (NYHA class III or IV) admitted to our hospital over a period of 5 years were studied. Patients with diabetes mellitus, liver or renal failure, and chronic obstructive lung disease were excluded. All patients received conventional treatment with digoxin, diuretic agents and an angiotensin converting enzyme inhibitor. On admission, blood and urine electrolytes and renal function parameters were determined. Arterial blood gases and serum anion gap determinations were also performed.

RESULTS

Hypomagnesemia was found in 15 [n=15 (17.4%)] CHF patients. The majority of these patients also exhibited other electrolyte abnormalities, such as hypokalemia, hypocalcemia and hypophosphatemia. Inappropriate magnesiuria (fractional excretion of magnesium >4%) was evident in eight hypomagnesemic patients. A variety of associated conditions, including poor dietary intake, also favored magnesium depletion.

CONCLUSION

Magnesium deficit is a common electrolyte disorder in CHF (NYHA class III/IV) patients and several interrelated mechanisms are implicated in its pathogenesis. Clinicians' awareness of the incidence of hypomagnesemia in this population as well as its related pathophysiology could be useful for the early detection and appropriate treatment to inhibit its arrhythmogenic potential.

A comparison of clinical, histopathological and cell-cycle markers in rats receiving the fungal toxins fumonisin B1 or fumonisin B2 by intraperitoneal injection

Fumonisins B1 and B2 (FB1 and FB2) are fungal secondary metabolites produced by members of the genus Fusarium. Although FB1 is usually detected in greater quantities, FB2 frequently co-occurs in contaminated feeds and foods and contributes to the total toxin load. In the present study, the comparative toxicity of FB1 and FB2 was examined in male Sprague-Dawley rats administered toxin (0.75 mg/kg body weight) or vehicle control intraperitoneally (ip) for 2, 4 or 6 consecutive days. Clinical changes, including elevated serum cholesterol, alanine aminotransferase (ALT), creatinine and protein, were slightly more pronounced in FB1-treated rats. The most consistent hematological change was an increase in vacuolated bone marrow cells, which was more pronounced in FB1-treated rats. Histopathological changes were similar in FB1- and FB2-treated rats and included single cell necrosis in kidneys and liver, cytoplasmic vacuolation in adrenal cortex and lymphocytolysis in thymus. In the liver mRNA expression for the cyclin kinase inhibitor p21 gene was significantly increased in FB1- and FB2-treated rats, compared to controls. Expression of mRNA for the cyclin D1 gene was significantly depressed in FB2-treated rats. Hepatic cyclin E mRNA was elevated in response to FB1 and FB2 compared to controls. In FB2-treated animals this corresponded with decreased liver p27 mRNA expression. Hepatic proliferating cell nuclear antigen (PCNA) transcription was elevated in FB1- but not FB2- treated rats. Changes in liver microsomal protein levels of p27, cyclin E and PCNA were similar to changes in gene expression. In contrast, cyclin D1 protein levels were elevated in rats treated with FB1 and, to a lesser extent, FB2. The data indicate that FB1 and FB2 can alter the expression of genes associated with the cell cycle, and indicate a need for a further understanding of the mechanistic basis of FB1 and FB2 toxicity.

Acid-base and electrolyte abnormalities in patients with acute leukemia

Disturbances of acid-base balance and electrolyte abnormalities are commonly seen in patients with acute leukemia. Our study aimed at illuminating the probable pathogenetic mechanisms responsible for these disturbances in patients with acute leukemia admitted to our hospital. We studied 66 patients (24 men and 44 women) aged between 17 and 87 years old on their admission and prior to any therapeutic intervention. Patients with diabetes mellitus, acute or chronic renal failure, hepatic failure, patients receiving drugs that influence acid-base status and electrolyte parameters during the last month, such as corticosteroids, cisplatin, diuretics, antacids, aminoglycosides, amphotericin, penicillin, and K(+), PO(4)(3-), or Mg(2+) supplements were excluded. Forty-one patients had at least one acid-base or electrolyte disturbance. There were no significant differences in the incidence of acid-base balance and electrolyte abnormalities between patients with acute myeloid leukemia (AML) and patients with acute lymphoblastic leukemia (ALL). The most frequent electrolyte abnormality was hypokalemia, observed in 41 patients (63%), namely in 34 patients with AML, and 7 with ALL; the main underlying pathophysiologic mechanism was inappropriate kaliuresis. Furthermore, hypokalemic patients more frequently experienced concurrent electrolyte disturbances (i.e., hyponatremia, hypocalcemia, hypophosphatemia, and hypomagnesemia), as well as various acid-base abnormalities compared to normokalemic patients. Hypokalemia in patients with acute leukemia may serve as an indicator of multiple concurrent, interrelated electrolyte disturbances, especially in patients with AML.

Syndrome of inappropriate antidiuretic hormone associated with vinorelbine therapy

OBJECTIVE

To describe onset of syndrome of inappropriate antidiuretic hormone (SIADH) associated with vinorelbine therapy for advanced breast cancer.

CASE SUMMARY

A 50-year-old white woman with a history of advanced breast cancer refractory to other treatment modalities was receiving vinorelbine. Blood chemistries revealed severely depleted sodium and potassium concentrations from a normal baseline within a 7-day period. A recheck of blood chemistries confirmed hyponatremia. The patient was admitted to the hospital and treated for SIADH. After successful treatment, she was given demeclocycline prophylactically and rechallenged with vinorelbine without recurrence of the syndrome.

DISCUSSION

SIADH has been reported as a complication of treatment with vinca alkaloids. To our knowledge, this is the first report of this syndrome related to vinorelbine therapy.

CONCLUSIONS

Because of its structural similarity to the other vinca alkaloids, vinorelbine is believed to be responsible for SIADH in our patient. Clinicians should be aware of the possibility that vinorelbine may cause SIADH and possibly hypokalemia.

Hyponatremia

The serum sodium concentration reflects the osmolality of the extracellular fluid and provides no direct information about total body sodium content. Patients with hyponatremia may have decreased, normal, or increased total body sodium content. The first step in the approach to the patient with hyponatremia is measurement of plasma osmolality. Hyponatremia with normal plasma osmolality results from hyperlipemia or hyperproteinemia, whereas hyponatremia with increased plasma osmolality results from hyperglycemia or mannitol infusion. Patients with hyponatremia and decreased plasma osmolality may be hypovolemic, hypervolemic, or normovolemic. The volume status of the patient is best determined by history, physical examination, and a few ancillary tests (e.g., total plasma protein concentration, hematocrit, blood pressure, central venous pressure). The clinical signs of hyponatremia are related more to the rapidity of onset than to the severity of the associated plasma hypoosmolality and reflect influx of water into the central nervous system. The main goals of treatment in hyponatremia are to diagnose and manage the underlying disease and, if necessary, to increase serum sodium concentration and plasma osmolality.

Pathogenetic mechanisms of hypomagnesemia in alcoholic patients

The aim of our study was to describe the possible pathophysiologic mechanisms of hypomagnesemia in alcoholic patients. A total of 127 chronic alcoholic patients admitted to our university hospital for causes related to alcohol abuse were studied. Hypomagnesemia was the most common electrolyte disturbance observed in 38 patients (29.9%). In 18 of them inappropriate magnesiuria was evident, possibly due to hypophosphatemia, to metabolic acidosis or to a direct magnesiuric effect of acute alcohol consumption. The causes of hypomagnesemia in the remaining 20 patients were alcohol withdrawal syndrome and diarrhea. Respiratory alkalosis was evident in 10 hypomagnesemic patients and could have played a role in the development of hypomagnesemia. A decreased magnesium intake could also have contributed to the hypomagnesemia, especially in malnourished alcoholic patients. Hypomagnesemic patients more frequently had other acid-base and electrolyte abnormalities, such as hypophosphatemia, hypokalemia, hypocalcemia, and respiratory alkalosis, as compared with the normomagnesemic patients. Moreover, in hypomagnesemic patients serum magnesium levels were correlated with the indices of potassium and phosphorus excretion, suggesting that serum magnesium levels play a central role in the homeostasis of the other electrolytes. In conclusion, hypomagnesemia is the most common electrolyte abnormality observed in alcoholic patients, as a result of various pathophysiologic mechanisms.

Intravenous phosphate repletion regimen for critically ill patients with moderate hypophosphatemia

OBJECTIVE

To document the safety and efficacy of an intravenous phosphate repletion regimen that is more aggressive than recommended by previously published guidelines, in intensive care unit (ICU) patients with hypophosphatemia.

DESIGN

Prospective evaluation of rapid, intravenous phosphate repletion in eligible patients.

SETTING

Surgical ICU in a teaching hospital.

PATIENTS

Patients with a serum phosphorus concentration of < 2 mg/dL (< 0.65 mmol/L) while in the ICU.

INTERVENTIONS

Enrolled patients received 15 mmol of sodium phosphate in 100 mL of 0.9% sodium chloride, infused intravenously over a period of 2 hrs. Patients with a serum potassium concentration of < 3.5 mmol/L received potassium phosphate, if no other potassium supplementation was ordered. The same dose could be repeated to a maximum of 45 mmol in a 24-hr period if either the 6-hr or follow-up (18- to 24-hr) postinfusion serum phosphorus remained < 2 mg/dL (< 0.65 mmol). Serum electrolytes, renal function, vital signs, and reflexes were closely monitored.

MEASUREMENTS AND MAIN RESULTS

Eleven patients enrolled had baseline serum phosphorus values of 1.6 to 1.9 mg/dL (0.51 to 0.61 mmol/L). The serum phosphorus value immediately postinfusion was 2.3 to 5.3 mg/dL (0.74 to 1.7 mmol/L). Only one patient had a 6-hr postinfusion serum phosphorus of < 2 mg/dL (< 0.65 mmol/L), requiring two additional doses. Two other patients each required a second dose. Serum phosphorus was corrected in other patients with a single dose. No significant changes were noted in serum calcium, magnesium, or potassium concentrations, urine output, vital signs, or reflexes throughout the repletion period.

CONCLUSIONS

All patients were successfully repleted using the described protocol without any significant adverse effects. This repletion regimen may have widespread applicability in the ICU setting.

Fractional excretion of potassium in normal subjects and in patients with hypokalaemia

The aim of our study was the determination of fractional excretion of potassium (FEK+) in both normal subjects and hypokalaemic patients. Three hundred and twelve normal subjects aged 21-69 years and 84 hypokalaemic patients aged 36-72 years were studied. The mean FEK+ in normal subjects was 8% (range 4-16%). FEK+ was positively correlated with serum potassium (r = 0.74, p < 0.0001) and inversely with serum creatinine (r = -0.51, p < 0.001). The mean FEK+ in patients with hypokalaemia of external origin was 2.8% (range 1.5-6.4%). On the contrary, the mean FEK+ in hypokalaemic patients in whom renal potassium loss was the main aetiologic factor for the pathogenesis of hypokalaemia was 15% (range 9.5-24%).

The effect of thrombocytosis on serum potassium and phosphorus concentrations

Thrombocytosis is a cause of falsely elevated serum potassium concentrations, and phosphorus concentrations may be similarly distorted. Because plasma concentrations are not affected, the difference between the serum and plasma concentrations detects spurious elevations. The authors, in this study, sought to determine the degree of correlation between thrombocytosis and false elevations in serum potassium and phosphorus concentrations. Ninety-one general, medical/surgical patients with elevated platelet counts were identified by laboratory reports. Subjects were stratified into blocks by platelet count. Samples were obtained simultaneously for serum and plasma potassium and phosphorus concentrations and complete blood counts. The serum minus plasma concentrations for potassium (Kdiff) and phosphorus (Pdiff) were calculated and analyzed against each other and the platelet count by linear regression. A control group of 20 subjects with normal platelet counts was used to verify laboratory results with literature values. The Kdiff and Pdiff values in the control group very closely approximated literature values of 0.4 mmol/L and 0.08 mmol/L, respectively. Platelet count was a moderate predictor of Kdiff, r2 = 0.55 (p = 0.00001). Kdiff exceeded the upper limit of control at a platelet count of approximately 600 x 10(9)/L. Platelet count also correlated with Pdiff, r2 = 0.31 (p = 0.00001). Additionally, Kdiff correlated with Pdiff, r2 = 0.39 (p = 0.00001). Thrombocytosis is associated with false elevations in measured serum potassium and phosphorus concentrations. Additionally, the magnitude of elevations in potassium and phosphorus concentrations appear to be related.

Management of neurosurgical patients with hyponatremia and natriuresis

The main objective of our study was to evolve a practical management protocol for neurosurgical patients with hyponatremia and natriuresis, based on their blood volume status and hematocrit. Twenty-one patients with hyponatremia and natriuresis and 3 control patients were studied. Patients with hyponatremia were categorized on the basis of their hematocrit, central venous pressure, and total blood volume. Group A consisted of patients with hypovolemia and anemia (16 patients); Group B patients had hypovolemia but no anemia (5 patients); Group C included those with hypervolemia (0 patients). Patients in Groups A and B received isotonic saline (> 50 ml/kg/d) and oral salt (12 g/d). Additionally, those in Group A were transfused with 500 ml of whole blood. The end points in the study were 72 hours after entry or two consecutive serum sodium values of > 130 mEq/L, whichever was earlier. Hyponatremia was corrected in all the patients within 72 hours (1 patient, < 24 h; 13 patients, < 48 h; and 7 patients, < 72 h). We conclude that most neurosurgical patients with hyponatremia and natriuresis have hypovolemia, with or without anemia. Fluid and salt replacement and a blood transfusion rather than fluid restriction often results in the correction of the hyponatremia. Our findings offer indirect evidence to support the hypothesis that in most of these patients, hyponatremia is caused by cerebral salt wasting syndrome, rather than the syndrome of inappropriate secretion of antidiuretic hormone.

Complications associated with the absorption of hysteroscopic fluid media

OBJECTIVES

To review the literature concerning complications resulting from absorption of hysteroscopic fluid distension media and to describe methods to treat and prevent these complications.

DESIGN

All pertinent literature on fluid distension media used for endoscopy, as well as relevant reports concerning the management of fluid and electrolyte imbalance, was reviewed.

RESULTS

The absorption of large volumes of electrolyte-free, low-viscosity fluid may result in volume overload with water intoxication. Volume overload may cause pulmonary edema, and water intoxication may lead to hyponatremia, hypo-osmolarity, and cerebral edema. In contrast, the absorption of dextran-70 may cause volume overload secondary to the oncotic effect of intravascular dextran. Dextran-70 has been associated with anaphylaxis and coagulation disorders.

TREATMENT

The use of diuretics is advocated. Urine output must be closely monitored. Judicious correction of electrolyte imbalance will prevent morbidity.

PREVENTION

Meticulous attention to intraoperative fluid balance is imperative. A multichannel hysteroscope is necessary to keep intrauterine pressure low. Extensive surgical procedures may need to be performed in stages.

CONCLUSIONS

Severe volume overload and electrolyte imbalance may result from fluid absorption during operative hysteroscopy. Most complications may be avoided by closely monitoring fluid balance intraoperatively.

Syndrome of inappropriate secretion of antidiuretic hormone secondary to fluoxetine

OBJECTIVE

To report a case of possible fluoxetine-induced syndrome of inappropriate antidiuretic hormone secretion (SIADH).

CASE SUMMARY

A 92-year-old patient was prescribed oral fluoxetine 20 mg daily for depression. After 13 days of therapy, she developed severe weakness and was found to have hyponatremia. Fluoxetine was discontinued. Treatment included fluid restriction and sodium chloride and potassium supplementation. Eight days after admission, the hyponatremia resolved and the patient was discharged without any pharmacologic treatment for depression.

DISCUSSION

Case reports on fluoxetine-induced SIADH were reviewed. Fluoxetine-associated SIADH appears to occur most commonly after short-term therapy in elderly patients. Resolution of hyponatremia occurs six days to two weeks after discontinuation of fluoxetine.

CONCLUSIONS

Geriatric patients receiving fluoxetine should be monitored regularly to detect abnormal electrolyte values.

Changing pattern of treatment policies invalidates the use of C-reactive protein level and hyponatremia as indicators of sepsis in children with malignancies

We evaluated serum C-reactive protein (CRP) level and serum sodium concentration as early indicators of bacteremia in neutropenic children in two different series in 1983-1984 (49 bacteremias) and 1989-1990 (29 bacteremias). During the earlier period, the goal was to avoid unnecessary antimicrobial therapy. Currently a neutropenic patient is placed on antimicrobial therapy at the first sign of fever. In 1983-1984 the serum CRP concentration was elevated in every case, whereas in 1989-1990 it was normal in 34% cases (P = .0001). Hyponatremia was detected on admission in 84% and 52% cases (P = .0001). The urinary sodium concentration was elevated in most cases. The mortality in bacteremia was 22% in 1983-1984 compared to 3% (P = .025) in 1989-1990. Prompt initiation of empirical antimicrobial therapy in children with fever and neutropenia invalidates the use of hyponatremia and an elevated CRP level as early indicators of sepsis.

A randomized controlled trial of quinidine in the treatment of cirrhotic patients with muscle cramps

In an attempt to evaluate the effect of quinidine in the treatment of patients with cirrhosis and muscle cramps, 31 cirrhotic patients with muscle cramps were randomly divided into two groups and given orally 400 mg of quinidine sulfate per day or placebo, respectively. Baseline clinical and laboratory data for these two groups were similar. Four weeks after oral administration of quinidine, the number of cramps significantly decreased from 14.4 +/- 1.7 (mean +/- S.E.) to 4.4 +/- 1.1 episodes (p less than 0.0001), but it remained unchanged in the placebo group (from 11.8 +/- 1.0 to 11.5 +/- 1.5 episodes, p greater than 0.05). In addition, 88% of the 16 patients on quinidine and 13% of the 15 patients on a placebo showed a greater than 50% reduction in the number of cramps during a 4-week treatment period (p less than 0.0001). The peak and trough serum levels of quinidine in patients having received quinidine for 2 weeks were 1.3 +/- 0.1 and 0.7 +/- 0.1 mg/l, respectively. There was a significant relationship between serum quinidine concentrations and attenuation of cramps. No significant adverse effect was observed during the study, except for five (31%) patients who developed mild diarrhea after quinidine therapy. Diarrhea subsided spontaneously or was controlled by medications without the interruption of quinidine therapy. It was concluded that quinidine is a safe and effective drug for the treatment of cirrhotic patients with muscle cramps.