Low Plasma Sodium Concentrations Research Articles

Forecasting individual exercise sweat losses from forecast air temperature and energy expenditure.

Recent success in predicting individual sweat losses from air temperature and energy expenditure measurements suggests a potential for forecasting individual sweat losses for future combinations of environment and exercise. The purpose of this study is to determine the plausibility of accurately forecasting exercise sweat losses from meteorological air temperature forecasts and individual running energy expenditure forecasts. The potential impact on plasma sodium is also estimated when setting drinking rates equal to forecast sweat losses. Individual exercise sweat losses (equated to water needs) and energy expended while running were measured in 33 participants along with air temperature and compared with forecasts of the same. Forecast inputs were used in a web app to forecast exercise sweat losses for comparison with observed values. The bias between forecast and observed exercise sweat losses was used to calculate the potential drinking impact on plasma sodium. The concordance correlation coefficient between forecast and observed values was 0.95, 0.96, and 0.91 for air temperature, energy expenditure, and exercise sweat losses, respectively, indicating excellent agreement and no significant differences observed via t-test. Perfect matching of water intake to sweat losses would lower plasma sodium concentrations from 140 to 138 mmol/L; calculations using the 95% limits of agreement for bias showed that drinking according to forecast exercise sweat losses would alter plasma sodium concentrations from 140 to between 136 and 141 mmol/L. The outcomes support the strong potential for accurately forecasting exercise sweat losses from commonly available meteorological air temperature forecasts and energy expenditure from forecast running distance.

Dysfunction of the endothelium and constriction of the isolated rat's middle cerebral artery in low sodium environment in the presence of vasopressin.

Hyponatraemia, a water-electrolyte disorder diagnosed in patients with subarachnoid haemorrhage (SAH), increases a risk of persistent vasospasm. In majority of cases, hyponatraemia results from inappropriate secretion of vasopressin (AVP). The effect of AVP-associated hyponatraemia on cerebral vasculature is unknown. The present study aimed to elucidate the role of AVP in the response of the middle cerebral artery (MCA) of the rat to hyponatraemia. Isolated, cannulated, and pressurized rat MCAs were perfused/superfused with physiological (Na+ =144mmol/L) buffer or low-sodium (Na+ =121mmol/L) buffer containing either AVP or angiotensin II (ANG II). ANG II was used to check if the effect of low plasma sodium concentration combined with AVP on the MCA tone is unique to vasopressin. At physiological Na+ concentration, vasopressin (1.4×10-11 mol/L) or angiotensin II (10-9 mol/L) resulted in relaxation of the MCA. Substitution of low-sodium for the normal sodium buffer with the same concentration of AVP, resulted in the constriction of the MCA. This effect was absent after removal of the endothelium, administration of vasopressin V1 receptor antagonist or concomitant inhibition of endothelin-1 receptors and synthesis of thromboxane A2. In contrast, no constriction of the MCA in low-sodium buffer was observed when AVP was replaced with ANG II. Our data suggest that presence of vasopressin and low sodium ion concentration results in the change of endothelium phenotype from pro-vasodilatory to pro-vasoconstrictory. This phenomenon may be an overlooked factor contributing to vasospasm in SAH patients with hyponatraemia caused by inappropriate antidiuretic hormone secretion (SIADH).

Management and consequences of postoperative fluctuations in plasma sodium concentration after pediatric brain tumor surgery in the sellar region: a national cohort analysis

PurposeSevere fluctuations in plasma sodium concentration and plasma osmolarity, including central diabetes insipidus (CDI), may have significant influence on postoperative morbidity and mortality after pediatric brain tumor surgery.The aim of this study was to describe the frequency, severity and neurological consequences of these fluctuations in pediatric brain tumor survivors.MethodsA retrospective, multi-institutional chart review was conducted among all children who underwent brain tumor surgery in the sellar or suprasellar region in seven university hospitals in the Netherlands between January 2004 and December 2013.ResultsPostoperative CDI was observed in 67.5% of 120 included children. Fluctuations of plasma sodium concentration ≥ 10 mmol/L/24 h during the first ten postoperative days were seen in 75.3% of patients with CDI, with a maximum delta of 46 mmol/L/24 h. When compared to patients without CDI, altered mental status occurred more frequently in patients with postoperative CDI (5.1 vs. 23.5% respectively, p = 0.009). Low plasma sodium concentration was related to altered mental status and the occurrence of seizures. Frequency and severity of fluctuations in plasma sodium concentration during the first ten postoperative days were significantly higher in patients with permanent CDI at last follow-up than in patients with transient CDI or without CDI (p = 0.007).ConclusionPostoperative CDI is a common complication after pediatric brain tumor surgery in the sellar or suprasellar region. Extreme plasma sodium concentrations and large intra-day fluctuations still occur and seem to influence the postoperative neurological course. These results illustrate the need for intensive monitoring in a highly experienced center.

A new method for determining plasma water content: application in pseudohyponatremia

Pseudohyponatremia is a clinical condition characterized by an increased fraction of protein or lipid in plasma, thereby resulting in an artificially low plasma sodium concentration ([Na(+)](p)). Since the automated method of measuring [Na(+)](p) in most laboratories involves the use of an indirect ion-selective electrode (I-ISE), this method does not correct for elevated protein or lipid concentrations. In I-ISE, the plasma sample is diluted before the actual measurement is obtained, and the [Na(+)](p) is determined based on the assumption that plasma is normally composed of 93% plasma water. Therefore, the [Na(+)](p) as determined by I-ISE will be artificially low in clinical conditions when the plasma water content (PWC) is <93%. In contrast, the plasma is not diluted when the [Na(+)](p) is measured using direct ISE (D-ISE). This method directly measures Na(+) activity in plasma water and is therefore unaffected by the proportion of plasma occupied by water. In this study, we report a novel quantitative method for determining the PWC utilizing I-ISE and D-ISE. To validate this new method experimentally, we altered the PWC in vitro by dissolving varying amount of salt-free albumin in human plasma. We then measured PWC gravimetrically in each sample and compared the gravimetrically determined PWC with the ISE-determined PWC. Our findings indicate that the PWC can be accurately determined based on differences in the [Na(+)](p) as measured by I-ISE and D-ISE and that this new quantitative method can be a useful adjunct in the analysis of the dysnatremias.

Association of hyponatremia and hyperglycemia with outcome in dogs with congestive heart failure

AbstractObjective: To evaluate plasma sodium and glucose concentrations in dogs with congestive heart failure (CHF) prior to treatment and evaluate the differences between survivors and non‐survivors.Design: Retrospective study.Animals: Fifty‐nine dogs with CHF prior to receiving cardiac medication.Interventions: None.Measurements and main results: The mean plasma sodium concentration in dogs with CHF was below the reference range (144–156 mmol/L) and significantly lower (P=0.009) in non‐survivors (141±6 mmol/L) compared with survivors (147±4 mmol/L). The mean plasma glucose concentration was above the reference range (76–117 mg/dL) and significantly higher (P=0.004) in non‐survivors (128±52 mg/dL) compared with survivors (100±13 mg/dL). Forty‐four percent of non‐survivors had concurrent low plasma sodium and high plasma glucose concentrations, whereas no survivors had both abnormalities (P&lt;0.0001).Conclusions: Lower plasma sodium and higher plasma glucose are associated with a worse outcome in dogs with CHF.

Acute in-hospital hyponatremia in children: an observational study

To develop hyponatremia (plasma sodium concentration (PNa) < 136 mM), there must be a source of electrolyte free water (EFW) and actions of antidiuretic hormone (ADH) to prevent its excretion. A low PNa is the most common electrolyte disorder in hospitalized children and it makes them more prone to neurological damage.

Biosynthetic response of mouse intermediate pituitary gland to induced drinking and dehydration

There are indications that the intermediate lobe peptide alpha-MSH is involved in the regulation of the hydromineral balance in mice and other mammals. The purpose of our studies was to determine whether manipulation of this balance in the mouse could lead to changes in either the rate of POMC biosynthesis in the pars intermedia or to changes in the direction of the processing of the precursor protein to form bioactive peptides. The results show that excess drinking, induced by substitution of drinking water by a 5% glucose solution, causes a rapid increase in POMC synthesis, whereas dehydration has the opposite effect; no evidence could be found that the above treatments have any effect on the processing of POMC, although strain differences were found in level of N-terminal acetylation of newly synthesized melanotropins and endorphins. The changes in various parameters of the hydromineral balance of the animals are consistent with the concept that peptides of the pars intermedia may be involved in regulating plasma aldosterone levels under severe conditions of low plasma sodium concentration.

Brain dehydration and neurologic deterioration after rapid correction of hyponatremia

We made rats severely hyponatremic, varying the rate of onset and duration of the disturbance, and then compared rapid correction to slow correction. An acute fall in the plasma Na to 106 mEq/liter within seven hours caused seizures and coma, but these findings resolved and survival was 100% after either rapid or slow correction. A more gradual fall in plasma Na to 95 mEq/liter in three days caused neither seizures nor coma. Measurements of brain water and electrolytes showed that adaptive losses of brain Na and K (maximally depleted within seven hours) and slower losses of non-electrolyte solutes progressively reduced brain edema. After three days of hyponatremia, rapid correction to 119 mEq/liter with 1 M NaCl or to 129 mEq/liter by withdrawing DDAVP caused brain dehydration because lost brain K and non-electrolyte solutes were recovered slowly. This treatment was followed by a delayed onset of severe neurologic findings, demyelinating brain lesions and a mortality rate of over 40%. Slow correction (0.3 mEq/liter/hr) avoided these complications and permitted 100% survival. We conclude that the rat adapts quickly to hyponatremia and can survive with extremely low plasma sodium concentrations for prolonged periods. Although rapid correction is well tolerated when hyponatremia is of brief duration, it may cause brain damage in animals that have had time to more fully adapt to the disturbance.

Water and Electrolyte Metabolism of the Tammar Wallaby Macropus eugenii

Seasonal changes in body condition and water and electrolyte metabolism in two populations of tammar wallabies (Macropus eugenii) are described in this paper. One population lives in a beach environment and has no access to freshwater, whereas the second population lives in the vicinity of a continuously flowing freshwater bore. During normal (mild) summers, the availability of free water has no influence on the condition of the tammars or on their water and electrolyte metabolism. Only during periods of extended summer drought is free water marginally advantageous to the bore population, as indicated by lower circulating antidiuretic hormone levels (ADH), a higher condition index, and lower total body water content. Both populations showed low plasma sodium concentrations after a prolonged drought, indicating that tammars are exceptionally resistant to the effects of hyponatraemia. After the onset of the winter rains, plasma sodium concentrations increase and the water turnover rises dramatically. The high water content of the vegetation at this time appears to prevent the tammars from ingesting enough food to satisfy their nutritional requirements, and their condition continues to decline, reaching its annual minimum in midwinter. It is evident that the breeding season of the tammars on Garden Island, which falls in early summer, is attuned to changes in condition and represents the only period of the year when the animals are neither water deprived nor suffering from nutritional deficiencies.

PATHOPHYSIOLOGICAL CHANGES IN PLASMA AND BODY COMPSITION OF YOUNG POULTS FED A SODIUM-DEFICIENT DIET

Significantly lower feed intake, higher water intake and depressed growth rate were observed in poults under 30 days of age offered ad libitum a low (0.05%) sodium diet and tap water compared to control poults offered the same basal diet containing 0.25% added sodium. Mortality with dehydration occurred mainly between 2 and 3 wk of age in poults fed the low sodium diet. Significant pathophysiological changes in poults fed low sodium diet compared with the control on days 9–30 were: lower plasma sodium, chloride and osmolal concentrations; higher plasma contents of uric acid and total protein; higher packed cell volume; and lower body sodium and water contents. Indications of extracellular dehydration and intracellular hydration and decreased glomerular filtration rate in sodium-deficient poults are discussed. Plasma and body composition of poults fed the low sodium diet returned to normal 1 wk after the poults were offered a normal (0.25%) sodium diet and tap water ad libitum.

RENIN, ANGIOTENSIN, CORTICOSTEROIDS, AND ELECTROLYTE BALANCE IN ADDISON'S DISEASE

Two patients with previously untreated Addison's disease were studied. Both showed defective adrenal responsiveness to infusions of corticotrophin and angiotensin, and both had abnormally low plasma sodium and high plasma renin concentrations. Plasma potassium was elevated in one and normal in the other. Steroid replacement therapy was accompanied by an increase in NaE, correction of plasma electrolyte concentrations, and a reduction of plasma renin concentration to normal. KE was virtually unchanged in the first weeks of treatment in either patient. In Case 1 treatment caused a movement of water and sodium from ICF to ECF, and probably of potassium from ECF to ICF. ECF volume increased more than TBW. Angiotensin infusion caused abdominal pain in this man, suggesting that the elevated plasma renin may contribute to the characteristic abdominal pain of Addison's disease. In Case 2 treatment restored the normal nyothemeral rhythm of urine flow, and caused a slight initial loss of TBW and weight.

Acute symptomatic hyponatremia

Hyponatremia is a laboratory finding which reflects several different physiological adjustments. The diagnosis of symptomatic hyponatremia is based on clinical findings, laboratory data, and the response to appropriate therapy. Laboratory data alone do not distinguish children with low plasma sodium concentrations and symptoms of water intoxication from those with hypotonic dehydration unassociated with central nervous system dysfunction. Data from 17 children with acute symptomatic hyponatremia are presented. These patients had satisfactory clinical and biochemical responses to infusions containing sodium at concentrations of 500 to 1,300 mEq. per liter.

Metabolic changes associated with mitral valvuloplasty.

Patients with chronic congestive heart failure operated upon for the surgical correction of mitral stenosis have been observed repeatedly to have low plasma sodium concentrations and elevated plasma potassium concentrations after operation. This study was primarily directed at an understanding of these abnormalities. The authors have shown that the preoperative patient has a characteristic disorder of body composition noteworthy for a high total body water, a high total body sodium, a low total exchangeable potassium and a low plasma sodium concentration. The effects of surgery on this abnormal body composition, and the therapeutic implications are discussed.