Nerve excitability changes in critical illness polyneuropathy

Patients in intensive care units frequently suffer muscle weakness and atrophy due to critical illness polyneuropathy (CIP), an axonal neuropathy associated with systemic inflammatory response syndrome and multiple organ failure. CIP is a frequent and serious complication of intensive care that delays weaning from mechanical ventilation and increases mortality. The pathogenesis of CIP is not well understood and no specific therapy is available. The aim of this project was to use nerve excitability testing to investigate the changes in axonal membrane properties occurring in CIP. Ten patients (aged 37-76 years; 7 males, 3 females) were studied with electrophysiologically proven CIP. The median nerve was stimulated at the wrist and compound action potentials were recorded from abductor pollicis brevis muscle. Strength-duration time constant, threshold electrotonus, current-threshold relationship and recovery cycle (refractoriness, superexcitability and late subexcitability) were recorded using a recently described protocol. In eight patients a follow-up investigation was performed. All patients underwent clinical examination and laboratory investigations. Compared with age-matched normal controls (20 subjects; aged 38-79 years; 7 males, 13 females), CIP patients exhibited reduced superexcitability at 7 ms, from -22.3 +/- 1.6% to -7.6 +/- 3.1% (mean +/- SE, P approximately 0.0001) and increased accommodation to depolarizing (P < 0.01) and hyperpolarizing currents (P < 0.01), indicating membrane depolarization. Superexcitability was reduced both in patients with renal failure and without renal failure. In the former, superexcitability correlated with serum potassium (R = 0.88), and late subexcitability was also reduced (as also occurs owing to hyperkalaemia in patients with chronic renal failure). In patients without renal failure, late subexcitability was normal, and the signs of membrane depolarization correlated with raised serum bicarbonate and base excess, indicating compensated respiratory acidosis. It is inferred that motor axons in these CIP patients are depolarized, in part because of raised extracellular potassium, and in part because of hypoperfusion. The chronic membrane depolarization may contribute to the development of neuropathy.

Late-onset manifestation of antenatal Bartter syndrome as a result of residual function of the mutated renal Na+-K+-2Cl- co-transporter

Genetic defects of the Na+-K+-2Cl- (NKCC2) sodium potassium chloride co-transporter result in severe, prenatal-onset renal salt wasting accompanied by polyhydramnios, prematurity, and life-threatening hypovolemia of the neonate (antenatal Bartter syndrome or hyperprostaglandin E syndrome). Herein are described two brothers who presented with hyperuricemia, mild metabolic alkalosis, low serum potassium levels, and bilateral medullary nephrocalcinosis at the ages of 13 and 15 yr. Impaired function of sodium chloride reabsorption along the thick ascending limb of Henle's loop was deduced from a reduced increase in diuresis and urinary chloride excretion upon application of furosemide. Molecular genetic analysis revealed that the brothers were compound heterozygotes for mutations in the SLC12A1 gene coding for the NKCC2 co-transporter. Functional analysis of the mutated rat NKCC2 protein by tracer-flux assays after heterologous expression in Xenopus oocytes revealed significant residual transport activity of the NKCC2 p.F177Y mutant construct in contrast to no activity of the NKCC2-D918fs frameshift mutant construct. However, coexpression of the two mutants was not significantly different from that of NKCC2-F177Y alone or wild type. Membrane expression of NKCC2-F177Y as determined by luminometric surface quantification was not significantly different from wild-type protein, pointing to an intrinsic partial transport defect caused by the p.F177Y mutation. The partial function of NKCC2-F177Y, which is not negatively affected by NKCC2-D918fs, therefore explains a mild and late-onset phenotype and for the first time establishes a mild phenotype-associated SLC12A1 gene mutation.

Electrolyte disorders and in-hospital mortality during prolonged heat periods: a cross-sectional analysis

BACKGROUND Heat periods during recent years were associated with excess hospitalization and mortality rates, especially in the elderly. We intended to study whether prolonged warmth/heat periods are associated with an increased prevalence of disorders of serum sodium and potassium and an increased hospital mortality. METHODS In this cross-sectional analysis all patients admitted to the Department of Emergency Medicine of a large tertiary care facility between January 2009 and December 2010 with measurements of serum sodium were included. Demographic data along with detailed data on diuretic medication, length of hospital stay and hospital mortality were obtained for all patients. Data on daily temperatures (maximum, mean, minimum) and humidity were retrieved by Meteo Swiss. RESULTS A total of 22.239 patients were included in the study. 5 periods with a temperature exceeding 25 °C for 3 to 5 days were noticed and 2 periods with temperatures exceeding 25 °C for more than 5 days were noted. Additionally, 2 periods with 3 to 5 days with daily temperatures exceeding 30 °C were noted during the study period. We found a significantly increased prevalence of hyponatremia during heat periods. However, in the Cox regression analysis, prolonged heat was not associated with the prevalence of disorders of serum sodium or potassium. Admission during a heat period was an independent predictor for hospital mortality. CONCLUSIONS Although we found an increased prevalence of hyponatremia during heat periods, no convincing connection could be found for hypernatremia or disorders of serum potassium.

Age-related variety in electrolyte levels and prevalence of dysnatremias and dyskalemias in patients presenting to the emergency department.

BACKGROUND It was found that age and female gender are predisposing factors for hyponatremia in patients taking thiazides. OBJECTIVE To investigate whether a relationship exists between age and gender and serum sodium and potassium as well as the prevalence rates in a large population of patients presenting to the emergency department of a university hospital. METHODS In this retrospective analysis we gathered data on age, gender and current diuretic medication of all patients admitted to the emergency department of a large university hospital with measurement of serum sodium and potassium between January 1, 2009 and December 31, 2010. Prevalence rates of and risk factors for electrolyte disorders were calculated on the basis of these data. RESULTS A total of 20,667 patients were included in the analysis. Serum sodium levels declined significantly with increasing age while serum potassium rose, independent of diuretic medication at presentation. The prevalence rates of hyponatremia and hyperkalemia increased from 2.3% for hyponatremia in patients aged 16-21 years to 16.9% in patients aged >80 years and from 0.8% for hyperkalemia to 10.4%. In the regression analysis, age >60 years was a predictor for the presence of hyponatremia and hyperkalemia as was current use of diuretic medication. Male gender was associated with a decreased prevalence of hyponatremia and hypokalemia, while it was a predictor of hyperkalemia. CONCLUSIONS Sodium levels were lower with increasing age, independent of diuretic intake, while potassium levels were higher. We found dramatically increasing prevalences of hyponatremia and hyperkalemia with increasing age, while no such effect could be found for hypernatremia and hypokalemia.

Seizure and Profound Hypokalemia: Unusual Presentation of Primary Hyperparathyroidism

A 68-year-old man was admitted because of tonic–clonic convulsion. He had been receiving 200 mg itraconazole for 10 days. He had hypokalaemia (2.2 mEq/l), hypercalcaemia (Cacorr 11.0 mg/dl) and elevated serum parathyroid hormone (PTH, 95 pg/ml). Ultrasound examination of the neck revealed a low echoic tumour. Cessation of itraconazole and fluid supplementation eradicated clinical symptoms and profound hypokalaemia, but serum potassium remained low normal (3.4 mEq/l) and the mild hypercalcaemia and elevated PTH were unchanged. To conclude, a small amount of itraconazole (200 mg) precipitated profound hypokalaemia and seizure in a patient with mild hyperparathyroidism and low normal serum potassium.

Initiating sacubitril/valsartan (LCZ696) in heart failure: results of TITRATION, a double-blind, randomized comparison of two uptitration regimens

The aim is tassess the tolerability of initiating/uptitrating sacubitril/valsartan (LCZ696) from 50 to 200 mg twice daily (target dose) over 3 and 6 weeks in heart failure (HF) patients (ejection fraction ≤35%). A 5-day open-label run-in (sacubitril/valsartan 50 mg twice daily) preceded an 11-week, double-blind, randomization period [100 mg twice daily for 2 weeks followed by 200 mg twice daily (‘condensed’ regimen) vs. 50 mg twice daily for 2 weeks, 100 mg twice daily for 3 weeks, followed by 200 mg twice daily (‘conservative’ regimen)]. Patients were stratified by pre-study dose of angiotensin-converting enzyme inhibitor/angiotensin-receptor blocker (ACEI/ARB; low-dose stratum included ACEI/ARB-naïve patients). Of 540 patients entering run-in, 498 (92%) were randomized and 429 (86.1% of randomized) completed the study. Pre-defined tolerability criteria were hypotension, renal dysfunction and hyperkalaemia; and adjudicated angioedema, which occurred in (‘condensed’ vs. ‘conservative’) 9.7% vs. 8.4% (P = 0.570), 7.3% vs. 7.6% (P = 0.990), 7.7% vs. 4.4% (P = 0.114), and 0.0% vs. 0.8% of patients, respectively. Corresponding proportions for pre-defined systolic blood pressure <95 mmHg, serum potassium >5.5 mmol/L, and serum creatinine >3.0 mg/dL were 8.9% vs. 5.2% (P = 0.102), 7.3% vs. 4.0% (P = 0.097), and 0.4% vs. 0%, respectively. In total, 378 (76%) patients achieved and maintained sacubitril/valsartan 200 mg twice daily without dose interruption/down-titration over 12 weeks (77.8% vs. 84.3% for ‘condensed’ vs. ‘conservative’; P = 0.078). Rates by ACEI/ARB pre-study dose stratification were 82.6% vs. 83.8% (P = 0.783) for high-dose/‘condensed’ vs. high-dose/‘conservative’ and 84.9% vs. 73.6% (P = 0.030) for low-dose/‘conservative’ vs. low-dose/‘condensed’. Initiation/uptitration of sacubitril/valsartan from 50 to 200 mg twice daily over 3 or 6 weeks had a tolerability profile in line with other HF treatments. More gradual initiation/uptitration maximized attainment of target dose in the low-dose ACEI/ARB group.

Sodium and potassium balance depends on αENaC expression in connecting tubule.

Mutations in α, β, or γ subunits of the epithelial sodium channel (ENaC) can downregulate ENaC activity and cause a severe salt-losing syndrome with hyperkalemia and metabolic acidosis, designated pseudohypoaldosteronism type 1 in humans. In contrast, mice with selective inactivation of αENaC in the collecting duct (CD) maintain sodium and potassium balance, suggesting that the late distal convoluted tubule (DCT2) and/or the connecting tubule (CNT) participates in sodium homeostasis. To investigate the relative importance of ENaC-mediated sodium absorption in the CNT, we used Cre-lox technology to generate mice lacking αENaC in the aquaporin 2-expressing CNT and CD. Western blot analysis of microdissected cortical CD (CCD) and CNT revealed absence of αENaC in the CCD and weak αENaC expression in the CNT. These mice exhibited a significantly higher urinary sodium excretion, a lower urine osmolality, and an increased urine volume compared with control mice. Furthermore, serum sodium was lower and potassium levels were higher in the genetically modified mice. With dietary sodium restriction, these mice experienced significant weight loss, increased urinary sodium excretion, and hyperkalemia. Plasma aldosterone levels were significantly elevated under both standard and sodium-restricted diets. In summary, αENaC expression within the CNT/CD is crucial for sodium and potassium homeostasis and causes signs and symptoms of pseudohypoaldosteronism type 1 if missing.

Passive immunity transfer and serum constituents of crossbred calves

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Blood serum components and serum protein test of Hybro-PG broilers of different ages

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Serum electrolyte and total protein alterations in Pantaneiro horse during long distance exercise

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effect of sex and seasons of the year on hematologic and serum biochemical variables of captive brown brocket deer (Mazama gouazoubira)

The Brown brocket deer (Mazama gouazoubira) is the most common free-living and captive deer in South America, especially in Brazil, and has great ecological and scientific significance. However, data on hematological and biochemical parameters in brown brocket deer are scarce. The goal of this study was to establish reference ranges for hematological and biochemical parameters of Mazama gouazoubira, comparing differences during the seasons of the year and between sex. Blood samples from ten adult healthy brown brocket deer (6 female and 4 male) were collected during daytime, monthly, during 12 months. The animals were maintained in individual stable, protected from noise and fed ad libitum with commercial ration and green fodder. For blood collection, animals were submitted to physical restrain for no longer than 2 minutes. The following parameters were determined: red blood cell count (RBC), haemoglobin concentration, packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), white blood cell count (WBC), platelet count, enzyme activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) and serum levels of alkaline phosphatase (ALP), creatine kinase (CK), total protein (TP), albumin, cholesterol, total calcium, ionic calcium, sodium, potassium, magnesium, triglycerides, creatinine and urea. Values were compared according to season and sex. RBC count, WBC count and MCV suggested seasonal influence. Haemoglobin concentration, PCV and MCV were influenced by sex. Serum concentration of total calcium, ionic calcium, sodium, potassium and magnesium were influenced by season. Serum magnesium was also influenced by sex. The blood parameters herein reported may be useful as reference values for diagnostic and prognostic purposes in captive brown-brocket deer.

Continuous or repeated prolonged cisplatin infusions in children: a prospective study on ototoxicity, platinum concentrations, and standard serum parameters

BACKGROUND: To overcome the ototoxicity of cisplatin, single bolus infusions were replaced by repeated prolonged infusions of lower doses or by continuous infusions at still lower infusion rates. However, considering ototoxicity little is, in fact, known about the tolerance of repeated prolonged or continuous infusion in children. PROCEDURE: Auditory function was monitored along with plasma concentrations of free and total platinum (Pt), and with standard serum parameters (sodium, potassium, calcium, magnesium, phosphate, chloride, and creatinine) in 24 children receiving cisplatin by continuous infusion for the treatment of neuroblastoma and osteosarcoma or by repeated 1 or 6 hr infusions for the treatment of germ cell tumors. RESULTS: Hearing deteriorated in 10/15 osteosarcoma patients, 2/3 neuroblastoma patients, and 1/6 patients with germ cell tumors. Ototoxicity occurred after cumulative doses between 120 and 360 mg/m(2) cisplatin. In osteosarcoma patients, ototoxicity was associated with a comparatively higher mean plasma concentration of free Pt. However, Pt plasma concentrations did not discriminate between patients with or without ototoxicity. In patients experiencing ototoxicity serum creatinine increased by 45% compared to pre-treatment levels (mean). Serum creatinine increased by 26% in patients without ototoxicity (P < 0.05, Mann-Whitney Rank sum test). Despite standardized hydration, discrete but significant changes of potassium, sodium, magnesium, and phosphate were observed during and/or after cisplatin infusion, which, however, did not discriminate between patients with and without ototoxicity. CONCLUSIONS: While continuous cisplatin infusions are less nephrotoxic than repeated prolonged infusions, we observed considerable ototoxicity in patients treated with continuous cisplatin infusions, which necessitates further evaluations on the tolerance of continuous cisplatin infusions in children.

Serum lipoproteins during treatment with the antihypertensive agent indapamide

Considering the documented, potentially undesirable influence of various thiazide-type or loop diuretics on serum lipoproteins, we prospectively investigated in 69 men (mean age +/- SEM, 32 +/- 1 years) the metabolic effects of the new diuretic-antihypertensive compound indapamide. Compared to placebo, indapamide (2.5 mg/day) given for 6 to 8 weeks lowered (p less than 0.02 to less than 0.001) blood pressure (supine values from 148/98 +/- 3/2 to 137/93 +/- 3/2) in 29 men with mild to moderate essential hypertension, but not in 40 healthy men. In both groups, significant (p less than 0.05 to less than 0.001) decreases in body weight (-0.8 kg) and plasma potassium (-0.6 mmol/L), and increases in plasma uric acid (+20%), renin activity (+200%), and aldosterone documented good compliance. There were no significant changes in total cholesterol (in all subjects, from 208 +/- 6 to 213 +/- 6 mg/dl), low- or very low-density lipoprotein (VLDL) cholesterol (127 +/- 6 to 129 +/- 6 and 21 +/- 1 to 21 +/- 2 respectively), high-density lipoprotein cholesterol (50 +/- 1 to 51 +/- 1 mg/dl), total triglycerides (Tg) (108 +/- 5 to 112 +/- 6 mg/dl), VLDL-Tg, apoproteins A1 and A2, plasma glucose, epinephrine, norepinephrine, sodium, calcium, magnesium, and creatinine; apoprotein B (84 +/- 2 to 88 +/- 3 mg/dl) and plasma insulin after glucose loading dose tended to be increased minimally. The absence of distinct lipoprotein alterations after short-term indapamide treatment may be of clinical and epidemiological interest.

A phosphoinositide 3-kinase (PI3K)-serum- and glucocorticoid-inducible kinase 1 (SGK1) pathway promotes Kv7.1 channel surface expression by inhibiting Nedd4-2 protein

Epithelial cell polarization involves several kinase signaling cascades that eventually divide the surface membrane into an apical and a basolateral part. One kinase, which is activated during the polarization process, is phosphoinositide 3-kinase (PI3K). In MDCK cells, the basolateral potassium channel Kv7.1 requires PI3K activity for surface-expression during the polarization process. Here, we demonstrate that Kv7.1 surface expression requires tonic PI3K activity as PI3K inhibition triggers endocytosis of these channels in polarized MDCK. Pharmacological inhibition of SGK1 gave similar results as PI3K inhibition, whereas overexpression of constitutively active SGK1 overruled it, suggesting that SGK1 is the primary downstream target of PI3K in this process. Furthermore, knockdown of the ubiquitin ligase Nedd4-2 overruled PI3K inhibition, whereas a Nedd4-2 interaction-deficient Kv7.1 mutant was resistant to both PI3K and SGK1 inhibition. Altogether, these data suggest that a PI3K-SGK1 pathway stabilizes Kv7.1 surface expression by inhibiting Nedd4-2-dependent endocytosis and thereby demonstrates that Nedd4-2 is a key regulator of Kv7.1 localization and turnover in epithelial cells.