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Renal Disease; Fluid and Electrolyte Disorders
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
The normal plasma sodium concentration is 135–145 mmol/L. As sodium is the major extracellular electrolyte, hyponatraemia is usually associated with hypo-osmolality and hypernatraemia is usually associated with hyperosmolality. Both plasma hypo-osmolality and hyperosmolality can have adverse effects on cells, especially neural cells. In each case, the diagnosis and treatment depends on an assessment of body fluid volume.
The endocrine system
Published in C. Simon Herrington, Muir's Textbook of Pathology, 2020
The function of vasopressin is to regulate fluid balance by stimulating water reabsorption in the kidney. Lack of vasopressin, due to conditions damaging the hypothalamus or pituitary gland, can cause a condition called diabetes insipidus where patients fail to reabsorb fluid in the kidneys and therefore suffer from extreme thirst (polydipsia) and production of large amount of dilute urine (polyuria). Inappropriate secretion of vasopressin, classically ectopic secretion from a small cell lung cancer can cause the syndrome of inappropriate antidiuretic hormone secretion (SIADH). This results in retention of fluid, hypo-osmolality and hyponatraemia.
The general principles of surgery
Published in David M. Luesley, Mark D. Kilby, Obstetrics & Gynaecology, 2016
Fluid may be absorbed at the time of hysteroscopy. If excessive, it can result in hyponatraemia and hypo-osmolality, clinically characterised by nausea, vomiting, seizures, coma and even death. The amount of fluid absorbed is dependent on the volume infused and the infusion pressure. Owing to the short duration of a diagnostic procedure, excessive fluid retention is unlikely to be a problem.
The Association between Hemodynamically Significant Patent Ductus Arteriosus and 25-Hydroxyvitamin D Levels in Preterm Infants ≤32 Weeks Gestational Age
Published in Fetal and Pediatric Pathology, 2023
Recent studies have focused on various mechanisms that affect postnatal DA closure. Factors that contribute to ductal closure include decreased prostaglandin (PG) levels and ductal blood pressure and increased arterial O2 pressure [9]. Increased O2 pressure inhibits voltage-gated potassium channels (Kv) and ATP-sensitive potassium channels (KATP). This inhibition causes membrane depolarization, allowing calcium (Ca2+) influx through T-type (CaT) and L-type (CaL) Ca2+ channels and ensures the discharge of Ca2+ stores from the sarcoplasmic reticulum (SR) [9,10]. While CaL is O2 sensitive, CaT is upregulated by oxygenation [11,12]. Activation of the Rho-kinase pathway affects ductal closure by increasing Ca2+ sensitivity [13]. Apart from these O2-dependent mechanisms, hypoosmolality also increases Ca2+influx [14]. Owing to these mechanisms, increased intracellular Ca2+ causes ductal vasoconstriction [9]. Malfunction of these pathways that can occur at any stage can prevent ductal closure and lead to PDA.
Preclinical Development of Artificial Tears Based on an Extract of Artemia Salina Containing Dinucleotides in Rabbits
Published in Current Eye Research, 2021
Carlos Carpena-Torres, Jesús Pintor, Fernando Huete-Toral, Candela Rodriguez-Pomar, Alejandro Martínez-Águila, Gonzalo Carracedo
The increase in tear secretion produced by the 4% concentration Artemia salina extract, around 44%, confirmed its secretagogue effect. Contrary to what might be expected from dinucleotide polyphosphates, dose-response signal of the Artemia salina, whose main active principle is Gp4 G, did not reach a saturation point (see Figure 1).7,8 This fact could be explained considering the physical properties of the eye drops depending on the concentration of Artemia salina (see Table 1). On the one hand, the hyperosmolality of some eye drops could be producing a cytotoxic effect over ocular surface cells,18 affecting tear secretion mediated by purinergic signaling.1,4 On the other hand, the hypoosmolality of others could be producing corneal edema,19 which could block tear secretion. Effect of dinucleotides such as Ap4A and Up4 U on tear secretion has been widely reported in the scientific literature.1 Furthermore, different studies from our research group showed an increase in tear secretion between 33% and 60% after the instillation of these dinucleotides in male New Zeland white rabbits under the same experimental conditions,1,7,13,14 which are aligned with these results.
Approach to and management of abnormalities in plasma sodium
Published in Acta Clinica Belgica, 2019
SIADH represents the most frequent cause of hyponatremia [3]. Initially, hyponatremia results mainly from water retention, but urinary solute loss also plays an important role. Excess natriuresis follows water retention and mainly exceeds the intake if volume expansion is relatively acute. After a few days, the Na balance is re-established and a decline in the hydro-osmotic effect of ADH is observed (vasopressin escape). In SIADH there is no edema as fluid retention rarely exceeds 4 l part of which is localized intracellularly. To diagnose SIADH, the following criteria are needed: hypoosmolality,inappropriately concentrated urine (> 100 mOsm/kg H2O, although usually hypertonic to serum),natriuresis > 30 mEq/l (dependent on sodium intake),reversal of renal sodium wasting and correction of hyponatremia after water restriction, andnormal renal, adrenal and thyroid function and no signs of volume depletion (for example: lack of diuretic intake).