The electrolytes in hyponatremia

Safety Assessment of Vanillic Acid: Subacute Oral Toxicity Studies in Wistar Rats

OBJECTIVES

Vanillic acid (VA) is a flavoring agent, a phenolic acid, and an intermediary by-product formed during transformation of ferulic acid to vanillin. It has been investigated for diverse pharmacological actions and used in Chinese medicine for decades. However, there is no information in the literature about its mechanism of toxicity or safety with long-term use. The present study will not only supply information on its pharmacological profile but also encourage evidence-based pharmacotherapeutic use. Hence, we performed a subacute toxicity study.

MATERIALS AND METHODS

According to the Organisation for Economic Co-operation and Development Test Guideline 407 (2008), 3 groups of rats were formed consisting of 12 rats (6 male and 6 female) in each group. For the subacute toxicity, the dose was chosen after a limit test was conducted. VA (1000 mg/kg/day) was orally administered for 2 weeks to the treatment group, whereas the control group received an equivalent volume of the vehicle. To assess reversibility, VA (1000 mg/kg/day, p.o.) was administered to the satellite group for 2 weeks and animals were observed for an additional 2 weeks after treatment. The adverse signs, variation in body weight, and mortality were evaluated throughout the study period. On days 15 and 29, blood was collected to evaluate essential biochemical and hematological parameters. The animals were subsequently weighed and sacrificed. The weights of internal organs were recorded; gross necroscopy and histopathological studies were performed.

RESULTS

The hematological parameters of the satellite group increased and the serum sodium level decreased after the treatment. Satellite groups showed no other major change in biochemical parameters when compared to the control group. In addition, relative organ weights, gross necropsy examinations and histopathological structure of the internal organs showed no major alterations.

CONCLUSION

VA showed no adverse effect on the process of leukopoiesis, erythropoiesis or on internal organs, as verified by hematological and biochemical evaluations, gross necropsy, and histopathological studies. The decrease in serum sodium is not considered as a major toxic effect.

Syndrome of inappropriate antidiuretic hormone in a patient with leptomeningeal carcinomatosis

Background

Leptomeningeal carcinomatosis is a condition in which metastatic cancer cells infiltrate the meninges of the brain and spinal cord, progressing to also involve the cerebrospinal fluid. Incidence of leptomeningeal carcinomatosis arising from an esophageal cancer is particularly rare.

Case presentation

Here, we present a case report of a 76-year-old Caucasian man with a history of esophageal adenocarcinoma status-post chemoradiation followed by resection. He was admitted to our unit for intractable headache, nausea without emesis, anorexia, weakness, gait instability, delirium, syncope, and near syncope. Our diagnostic workup revealed leptomeningeal carcinomatosis and syndrome of inappropriate antidiuretic hormone. Our patient was treated with lumbar puncture for the headache, methotrexate for the leptomeningeal carcinomatosis, and table salt for the syndrome of inappropriate antidiuretic hormone. Despite our best efforts, our patient died 6 weeks posttreatment.

Conclusions

Understanding the molecular pathogenesis of the development of syndrome of inappropriate antidiuretic hormone associated with leptomeningeal carcinomatosis from metastatic esophageal adenocarcinoma would help us to identify patients at risk and treat them accordingly.

Hyponatremia in cancer patients: Time for a new approach

Hyponatremia is a common electrolyte disorder in cancer patients. It may be related to cancer, to anti-cancer therapy or to other concomitant treatments. In this setting hyponatremia is often caused by the syndrome of inappropriate anti-diuretic hormone secretion, which is due to the ectopic production of antidiuretic hormone (vasopressin), to extracellular fluid depletion, to renal toxicity caused by chemotherapy or to other underlying conditions. Recent studies suggested that hyponatremia might be considered a negative prognostic factor for cancer patients therefore its early detection, monitoring and management might improve the patient's outcome. Treatment of hyponatremia depends on patient's symptoms severity, onset timing and extracellular volume status. In this review we summarize the main causes of hyponatremia in cancer patients and its management, including the available treatment options.

Metabolic master regulators: sharing information among multiple systems

Obesity and diabetes are caused by defects in metabolically sensitive tissues. Attention has been paid to insulin resistance as the key relevant pathosis, with a detailed focus on signal transduction pathways in metabolic tissues. Evidence exists to support an important role for each tissue in metabolic homeostasis and a potential causative role in both diabetes and obesity. The redox metabolome, that coordinates tissue responses and reflects shared control and regulation, is our focus. Consideration is given to the possibility that pathosis results from contributions of all relevant tissues, by virtue of a circulating communication system. Validation of this model would support simultaneous regulation of all collaborating metabolic organs through changes in the circulation, regardless of whether change was initiated exogenously or by a single organ.

Diagnosis and management of hyponatremia in cancer patients

Hyponatremia, a common electrolyte abnormality in oncology practice, may be a negative prognostic factor in cancer patients based on a systematic analysis of published studies. The largest body of evidence comes from small-cell lung cancer (SCLC), for which hyponatremia was identified as an independent risk factor for poor outcome in six of 13 studies. Hyponatremia in the cancer patient is usually caused by the syndrome of inappropriate antidiuretic hormone (SIADH), which develops more frequently with SCLC than with other malignancies. SIADH may be driven by ectopic production of arginine vasopressin (AVP) by tumors or by effects of anticancer and palliative medications on AVP production or action. Other factors may cause hypovolemic hyponatremia, including diarrhea and vomiting caused by cancer therapy. Hyponatremia may be detected on routine laboratory testing before or during cancer treatment or may be suggested by the presence of mostly neurological symptoms. Treatment depends on several factors, including symptom severity, onset timing, and extracellular volume status. Appropriate diagnosis is important because treatment differs by etiology, and choosing the wrong approach can worsen the electrolyte abnormality. When hyponatremia is caused by SIADH, hypertonic saline is indicated for acute, symptomatic cases, whereas fluid restriction is recommended to achieve a slower rate of correction for chronic asymptomatic hyponatremia. Pharmacological therapy may be necessary when fluid restriction is insufficient. The orally active, selective AVP receptor 2 (V(2))-receptor antagonist tolvaptan provides a mechanism-based option for correcting hyponatremia caused by SIADH or other conditions with inappropriate AVP elevations. By blocking AVP effects in the renal collecting duct, tolvaptan promotes aquaresis, leading to a controlled increase in serum sodium levels.

Tumor-related hyponatremia

Hyponatremia is an important and common electrolyte disorder in tumor patients and one that has been reported in association with a number of different primary diagnoses. The correct diagnosis of the pathophysiological basis for each patient is important because it significantly alters the treatment approach. In this article, we review the epidemiology and presentation of patients with hyponatremia, the pathophysiologic groups for the disorder with respect to sodium and water balance and the diagnostic measures for determining the correct pathophysiologic groups. We then present the various treatment options based on the pathophysiologic groups including a mathematical approach to the use of hypertonic saline in management. In cancer patients, hyponatremia is a serious comorbidity that requires particular attention as its treatment varies by pathophysiologic groups, and its consequences can have a deleterious effect on the patient's health.

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.

Whole-body volume regulation and escape from antidiuresis

Both individual cells and organs regulate their volume in response to sustained hypo-osmolality via solute and water losses. Similar processes occur in the whole body to regulate the volumes of extracellular fluid (ECF) and intravascular spaces toward normal levels. Body water losses occur via the phenomena "escape from antidiuresis"; solute losses occur through the secondary natriuresis induced by water retention. As a result of resistance to arginine vasopressin (AVP) signaling, escape from antidiuresis is caused by downregulation of kidney aquaporin-2 expression despite high AVP plasma levels. Recent data have implicated downregulation of vasopressin V2R as a potential mechanism of resistance, and suggest that this may be a result of decreased intrarenal angiotensin II signaling in combination with increased intrarenal nitric oxide and prostaglandin E2 signaling. The natriuresis that results in volume regulation of the ECF and vascular spaces is the result of intrarenal hemodynamic changes produced by volume expansion, but the degree to which these effects are modulated by aldosterone secretion and the activity of distal sodium cotransporters and channels remains to be elucidated. The clinical implication of these volume-regulatory processes is that the chronic hyponatremic state is one of water retention and solute losses from intracellular fluid and ECF compartments. The degree to which solute losses versus water retention contribute to hyponatremia will vary in association with many factors, including the etiology of the hyponatremia, the rapidity of development of the hyponatremia, the chronicity of the hyponatremia, the volume of daily water loading, and individual variability. Understanding these volume-regulatory processes allows a better understanding of many aspects of the conundrum of patients with "clinical euvolemia" and dilutional hyponatremia from AVP-induced water retention.

Clinical relevance of hyponatraemia for the hospital outcome of cirrhotic patients

BACKGROUND

Hyponatraemia frequently develops in cirrhotic patients whose ability to excrete free water is impaired. The role of hyponatraemia in the prognosis of such patients is unclear.

AIM

To evaluate prevalence, clinical associations and prognostic impact of hyponatraemia in cirrhotic inpatients.

PATIENTS

A series of 156 cirrhotic patients consecutively admitted to our department, for a total of 191 admissions, were studied.

METHODS

Serum sodium levels were determined at admission and repeated at least weekly in all patients. The clinical status and the survival of patients with hyponatraemia (< or = 130 mmol/l) were compared to those of patients with normal sodium levels.

RESULTS

Hyponatraemia was found in 57 out of 191 admissions (29.8%). Bacterial infections, ascites, chronic diuretic therapy, but not gastrointestinal bleeding or renal failure, were more frequent in patients with hyponatraemia than in those with normal sodium levels. In 3 cases, none of these conditions were present and hyponatraemia was defined as "spontaneous". Hospital death rate was increased in patients with hyponatraemia (26.3% versus 8. 9%, chi2=8. 55, p=0.003). By multivariate analysis, the only parameters independently associated with survival were high serum bilirubin (p=0.006) and high serum urea levels (p=0.019). Twenty-five patients developed severe hyponatraemia (<125 mmol/l) during hospital stay. This event was associated with a concomitant bacterial infection in 21 cases. The mortality rate of these patients was very high (48%).

CONCLUSIONS

Hyponatraemia is frequent in cirrhotic inpatients. It is seldom a spontaneous event but rather occurs in association with ascites, chronic use of diuretics or bacterial infections. It is a negative prognostic factor associated with increased short-term mortality.

Thiazide-induced hyponatremia in the postoperative total joint replacement patient

The thiazide diuretic is a common medication in the elderly population for the treatment of hypertension. These same patients are the largest population for surgical intervention for joint arthroplasty. Postoperative management of these patients has shown to be complicated by hyponatremia associated with the use of thiazide diuretics. This study evaluates a consecutive series of 408 patients undergoing elective joint arthroplasty. An association was found with the use of thiazide diuretics in the preoperative period and the development of postoperative hyponatremia. The study is presented, along with a relevant review of the literature and suggestions for the orthopedic staff to limit the risk of hypoantremia and prolonged hospitalization in an otherwise stable postoperative course.

Combined fractional excretion of sodium and urea better predicts response to saline in hyponatremia than do usual clinical and biochemical parameters

BACKGROUND

The treatment of hyponatremic patients requires physicians to make a therapeutic choice between saline infusion and water restriction. Therefore, they need readily available and reliable parameters to facilitate making that choice. This study was designed to determine whether the use of clearance ratios can help clinicians recognize saline-responding hyponatremic patients.

PATIENTS AND METHODS

Thirty-five nonedematous, hospitalized, hyponatremic patients were classified according to their history and saline response into four groups: diuretic-taking patients, polydipsic patients, saline responders, and saline nonresponders. Within these four groups, clinical and biochemical volume-related parameters, including clearance ratios, were prospectively evaluated before infusion of 2 L isotonic saline. Clearance ratios as well as usual clinical and biochemical parameters were tested for their accuracy in predicting saline responsiveness.

RESULTS

Both positive (70%) and negative (54.5%) predictive values for hypovolemia were unsatisfactory; clinical prediction of hypovolemia was also characterized by low sensitivity (41.1%), but acceptable specificity (80%). In the polydipsia and saline-nonresponder groups, plasma urea and uric acid values tended to be lower than in the diuretic and saline-responder groups. However, the usefulness of these parameters was limited by too large an overlap among the different groups. In both polydipsic patients and saline responders, urinary sodium concentration was low. The combined amount of urinary sodium and potassium in relation to plasma sodium did not discriminate among the different groups. Most helpful in distinguishing among the groups was a combination of several clearance ratios (fractional excretions of sodium, potassium, urea, and uric acid), since the predictive use of each parameter on its own was restricted. The best indicator of saline responsiveness was a low fractional excretion of filtered sodium (< 0.5%) combined with a low fractional excretion of urea (< 55%).

CONCLUSION

The accuracy of clinical evaluation for predicting the state of extracellular fluid volume in hyponatremia is low. The combination of low fractional sodium excretion (< 0.5%) and low fractional urea excretion (< 55%) is the best biochemical way to predict saline response, whereas high fractional potassium excretion (> 20%) indicates diuretic intake.

Hyponatremic emergencies

Hyponatremia is a common clinical problem and can result in severe morbidity and even death. Understanding the pathophysiology of hyponatremic encephalopathy is central to accurate diagnosis and management. This article reviews the controversies surrounding the treatment of hyponatremia with special emphasis on risk to benefit ratio of different therapeutic strategies.

Pentoxifylline improves intracellular electrolytes in sepsis

Sepsis is associated with a generalised membrane dysfunction leading to an increase in intracellular sodium, chloride, and water. The decrease in extracellular water is thought to act as a nonosmotic stimulus to the secretion of antidiuretic hormone. The resultant hyponatraemia is associated with increased surgical morbidity and mortality. Treatment aimed at improving intracellular electrolytes may improve surgical morbidity and mortality. An animal model of peritonitis was used to evaluate the effect of pentoxifylline. Previously, this dimethyl xanthine derivative was shown to stabilise the cell membrane. Administration of pentoxifylline significantly lowered intracellular sodium and chloride, particularly when given after caecal ligation and puncture. This may have clinical implications in the treatment and prevention of hyponatraemia.

Osmotic demyelination syndrome following correction of hyponatremia: association with hypokalemia

The osmotic demyelination syndrome (ODS) is a neurologic complication associated with rapid correction of hyponatremia. A case is described in which the patient was found to have hypokalemia as well as hyponatremia prior to the development of ODS. The literature was reviewed for cases of ODS in which patients had hyponatremia (serum sodium < or = 126 mmol/L) at presentation followed by correction of the hyponatremia. Of the 74 cases in which serum sodium and serum potassium values were reported at the time of presentation, 66 patients (89%) had hypokalemia. In 20 of these cases, serial measurements of sodium and potassium were reported, and in no instance was the potassium level normalized prior to the time of most rapid correction of the serum sodium. Hypokalemia may predispose patients to develop osmotic demyelination following correction of hyponatremia. The etiology of this complication is unclear. In neurologically stable patients with severe hyponatremia, it may be beneficial to correct hypokalemia prior to correction of the serum sodium. This maneuver may further reduce the incidence of ODS.

Renal tubular sodium and water metabolism in brain tumour patients submitted to craniotomy

PURPOSE

To evaluate the effect of Brain Tomour (BT) and Neurosurgery (NS) on the renal handling of H2O and Na, and the clinical importance of SIADH in this setting.

METHODS

Fourteen patients with BT pre-op for NS and 6 controls (C) pre-op for general surgery, were assessed in a controlled prospective trial. All patients were normovolaemic, with normal renal function. They received 400 mg of lithium carbonate (Li) 8 hours before each of two test periods (I and II) and a standard water load only before period II. Clearances studies were performed pre-op (period I) and 24 hours post-op (period II).

RESULTS

Serum Na was normal at all times. Despite normovolaemia, a 1% decrement in serum osmolality and the water load, ADH dramaticaly increased from time I to II mainly in the BT group (36.2 +/- 9.4 vs 7.1 +/- 0.6 pmol/L, p = 0.02). FENa, FELi and FEUricA were significantly more elevated in the BT group pre and post-op (at time II respectively 4.6 +/- 1.6 vs 1.1 +/- 0.3%; 29.3 +/- 4.9 vs 22.6 +/- 5.5; 26.0 +/- 8.1 vs 11.3 +/- 2.2, p = 0.03). Proximal and distal H2O re-absorption and distal fractional Na re-absorption were identical in both groups pre and post-operatively.

CONCLUSIONS

1-BT and NS always induce a SIADH. 2-There was a primary Na loss at the proximal tubule level not explained by ADH increment, that did not significantly changed H2O handling. 3-To prevent hyponatraemia, hypotonic I.V. fluids should be avoided, but more importantly saline must be provided to this potentially salt-wasting condition.

Hyponatremia: pathophysiology and treatment, a pediatric perspective

Hyponatremia is the most commonly observed electrolyte abnormality in hospitalized children. The most serious consequences of hyponatremia and its treatment involve the central nervous system (CNS). Important factors determining the development of clinical symptomatology include: the rate of fall in serum sodium, and the severity and duration of hyponatremia. Acute hyponatremia is associated with increased brain water resulting in varying grades of encephalopathy whereas the osmoregulatory mechanism allows normalization of CNS water content in chronic hyponatremia. It is recommended that the therapy for hyponatremia be initiated on the basis of the presence or absence of symptoms. An increase of 4-6 mmol/l in serum sodium over 10-15 min is recommended in symptomatic patients. Rapid correction of chronic hyponatremia may result in osmotic dehydration syndrome and therefore should be avoided.