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1.
The challenges of diagnosis and management of Gitelman syndrome.
Urwin, S, Willows, J, Sayer, JA
Clinical endocrinology. 2020;(1):3-10
Abstract
Gitelman syndrome is an inherited tubulopathy characterized by renal salt wasting from the distal convoluted tubule. Defects in the sodium chloride cotransporter (encoded by SLC12A3) underlie this autosomal recessive condition. This article focuses on the specific challenges of diagnosing and treating Gitelman syndrome, with use of an illustrative case report. Symptoms relate to decreased serum potassium and magnesium levels, which include muscle weakness, tetany, fatigue and palpitations. Sudden cardiac deaths have been reported. Making a diagnosis may be difficult given its rarity but is important. A knowledge of the serum and urine biochemical picture is vital to distinguish it from a broad differential diagnosis, and application of genetic testing can resolve difficult cases. There is a group of Gitelman syndrome heterozygous carriers that experience symptoms and electrolyte disturbance and these patients should be managed in a similar way, though here genetic investigations become key in securing a difficult diagnosis. Potassium and magnesium replacement is the cornerstone of treatment, though practically this can be hard for patients to manage and often does not fully relieve symptoms even when serum levels are normalized. Challenges arise due to the lack of randomized controlled trials focussing on treatment of this rare disease; hence, clinicians endorse strategies in line with correction of the underlying pathophysiology such as sodium loading or pharmacological treatments, which seem to help some patients. Focussed dietary advice and knowing the best tolerated preparations of potassium and magnesium medications are useful tools for the physician, as well as an awareness of the specific burdens that this patient group face in order to signpost appropriate support.
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2.
Dietary potassium restriction attenuates urinary sodium wasting in the generalized form of pseudohypoaldosteronism type 1.
Adachi, M, Tajima, T, Muroya, K
CEN case reports. 2020;(2):133-137
Abstract
Owing to its rarity and severe nature, the treatment for generalized pseudohypoaldosteronism type 1 (PHA1), a genetic disorder in the epithelial sodium channel (ENaC), is exclusively experience-based. In particular, the usefulness of dietary potassium restriction in PHA1 remains unclear with the absence of theoretical background to elucidate its utility. First, we demonstrated the effect of potassium restriction in a 13-month-old patient with ENaC γ-subunit gene mutations via a retrospective chart review; reduction of daily dietary potassium intake from 40 to 20 mEq induced rapid restoration of volume depletion, as evidenced by weight gain, elevation of the serum sodium level from 133 to 141 mEq/L, decreased urinary sodium excretion, and normalized renin activity. The serum potassium level decreased from 5.6 to 4.5 mEq/L. Next, we attempted to elucidate the pathophysiological basis of the usefulness of potassium restriction, leveraged by the increased knowledge regarding the roles of with-no-lysine kinases (WNKs) in the distal nephron. When potassium is restricted, the WNK signal will turn "on" in the distal nephron via reduction in the intracellular chloride level. Consequently, the sodium reabsorption from the Na+Cl- cotransporter (NCC) in the distal convoluted tubule and possibly from pendrin in the β-intercalated cell will increase. Thus, potassium restriction causes NCC and pendrin to compensate for the non-functional ENaC in the collecting duct. In conclusion, dietary potassium restriction is one of the indispensable treatments for generalized PHA1.
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3.
Preeclampsia and low sodium (PALS): A case and systematic review.
Powel, JE, Rosenthal, E, Roman, A, Chasen, ST, Berghella, V
European journal of obstetrics, gynecology, and reproductive biology. 2020;:14-20
Abstract
Normal physiologic changes in pregnancy include mild hyponatremia. In some cases of preeclampsia, more significant hyponatremia has been associated with syndrome of inappropriate antidiuretic hormone secretion and hypervolemic hyponatremia. A 45-year-old gravida 2, para 0010 with a dichorionic twin gestation was diagnosed with preeclampsia at 30 weeks 6 days and noted to have concomitant hyponatremia of 125 mEq/L at our institution. Her hyponatremia was initially managed with furosemide and water restriction. She was delivered at 33 weeks 5 days due to worsening preeclampsia and continued significant hyponatremia despite treatment. Her hyponatremia resolved within 48 h after delivery. Our objectives were to discuss trends, treatment, and outcomes of cases with hyponatremia in preeclampsia. We performed a systematic review of the literature using Ovid Medline (1963-2017), Scopus (1962-2017), and PubMed (1963-2017, including Cochrane database). Relevant articles describing any case report of hyponatremia in preeclampsia were identified from the above databases without any time, language, or study limitations. Studies were deemed eligible for inclusion if they described a case of hyponatremia in the setting of preeclampsia. 18 manuscripts detailing 55 cases were identified. Pertinent demographic data and laboratory values were extracted. Maternal management strategy, diagnosis, delivery, and neonatal outcome data were also collected. Mean, range, standard deviation, and percentage calculations were used as applicable. Advanced maternal age (46 %), nulliparity (79 %), and multifetal gestation (34 %) were noted in patients with preeclampsia and low sodium. Hyponatremia was detected on average at 34 weeks gestation. 64 % were diagnosed with preeclampsia with severe features. When reported, diagnoses related to hyponatremia were syndrome of inappropriate antidiuretic hormone secretion (41 %) or hypervolemic hyponatremia (59 %). Indications for delivery included severe hyponatremia unresponsive to conservative measures in addition to other known obstetric or preeclamptic indications. Hyponatremia resolved within 48 h on average in cases where postpartum resolution was reported. It may be prudent to screen women with preeclampsia for electrolyte disturbances as part of their evaluation, especially in the setting of severe features. Initially, hyponatremia may be treated with medical management. In addition to established obstetric or preeclamptic indications, delivery may be considered if severe hyponatremia no longer responds to conservative measures.
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4.
Where Do the Salt and Water Go? A Case of Profound Hyponatremia.
Portales-Castillo, I, Sterns, RH, Bress, J, Proano, RA
American journal of kidney diseases : the official journal of the National Kidney Foundation. 2018;(6):885-889
Abstract
Treatment of profound hyponatremia is challenging. Severe symptoms mandate correction by 4 to 6 mEq/L within hours, but with risk factors for osmotic demyelination, daily correction should be <8 mEq/L. With a therapeutic window this narrow, clinicians would like to know how serum sodium (SNa) concentration will respond to their therapy. Based on isotopic measurements, Edelman showed SNa level to be a function of exchangeable sodium and potassium divided by total-body water. Edelman defined this relationship with linear regression yielding an equation of the form y = mx + b, where y is SNa level, x is exchangeable sodium and potassium divided by total-body water, m is the slope, and b is the intercept. Edelman said that the intercept of his regression "probably is a measure of the quantity of osmotically inactive exchangeable sodium and potassium per unit of body water." Predictive formulas are derived from Edelman's original linear regression, some including and some omitting the regression's intercept. We illustrate the performance and limitations of these formulas using comprehensive data for electrolyte and fluid balance obtained during the treatment of a critically patient who presented with an SNa concentration of 101 mEq/L.
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5.
Elevated Postmortem Vitreous Sodium and Chloride Level in a Salt Water Drowning Death During Self-Contained Underwater Breathing Apparatus Diving With Diving Mask in Place: Case Report.
Tse, R, Garland, J, Kesha, K, Morrow, P, Elstub, H, Cala, A, Spark, A, Stables, S, Sage, M
The American journal of forensic medicine and pathology. 2018;(3):247-249
Abstract
Elevation of postmortem vitreous sodium and chloride (PMVSC) levels in salt water drowning (SWD) is hypothesized to result from electrolyte changes in blood from salt water inhalation/ingestion during drowning. After approximately 1 hour after death, electrolytes may diffuse into the vitreous humor via the eye coverings. This hypothesis was based on a study where bovine eyeballs were immersed in salt water. There is no human study that could confirm that SWD would result in an initial elevation of PMVSC with no effects from immersion. We present an SWD during self-contained underwater breathing apparatus diving in which the face mask remained in its correct position while the deceased was underwater. The face mask would have prevented the orbits from being in direct contact with salt water and therefore stopped any effects of immersion on PMVSC. The PMVSC was 294 mmol/L, above control levels, and the reported cut-off of 259 mmol/L for a diagnosis SWD. The elevated PMVSC would unlikely be owing to immersion but SWD. This case report supports the observation that during SWD PMVSC would initially increase from salt water inhalation and ingestion and not from immersion.
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6.
Ultrafiltration Failure and Impaired Sodium Sieving During Long-Term Peritoneal Dialysis: More Than Aquaporin Dysfunction?
Morelle, J, Sow, A, Hautem, N, Devuyst, O, Goffin, E
Peritoneal dialysis international : journal of the International Society for Peritoneal Dialysis. 2016;(2):227-31
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Abstract
Fifteen years ago, our group reported the case of a 67-year-old man on peritoneal dialysis for 11 years, in whom ultrafiltration failure and impaired sodium sieving were associated with an apparently normal expression of aquaporin-1 (AQP1) water channels in peritoneal capillaries. At that time, AQP1 dysfunction was suggested as the cause of impaired free-water transport. However, recent data from computer simulations, and structural and functional analysis of the peritoneal membrane of patients with encapsulating peritoneal sclerosis, demonstrated that changes in the peritoneal interstitium directly alter osmotic water transport. In light of these insights, we challenge the initial hypothesis and provide several lines of evidence supporting the diagnosis of encapsulating peritoneal sclerosis in this patient and suggesting that severe peritoneal fibrosis accounted for the loss of osmotic conductance developed during the course of peritoneal dialysis.
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7.
Body fluid composition.
Jain, A
Pediatrics in review. 2015;(4):141-50; quiz 151-2
Abstract
UNLABELLED Body fluid composition is maintained in a normal physiologic range by regulatory mechanisms that control sodium and water metabolism. A detailed knowledge of the homeostatic mechanisms will help in understanding the pathogenesis and management of disorders of sodium and water balance. OBJECTIVES After completing this article, readers should be able to: 1. Understand the distribution of fluid and solute in different body compartments. 2. Demonstrate the homeostatic mechanisms involved in maintaining sodium and water metabolism. 3. Calculate osmolality and recognize the clinical importance of maintaining osmotic equilibrium. 4. Recognize common disorders of hypernatremia or hyperosmolality and evaluate and understand the role of calculating free water deficit in the treatment of these disorders. 5. Recognize common disorders of hyponatremia or hypo-osmolality, appreciate the role of urine sodium and urine osmolality in evaluation,and understand the importance of slow correction of these disorders.
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8.
Hyponatremia: a problem-solving approach to clinical cases.
Assadi, F
Journal of nephrology. 2012;(4):473-80
Abstract
Hyponatremia, defined as a serum sodium concentration of <135 mmol/L, often develops as a consequence of elevated levels of arginine vasopressin (AVP) hormone. AVP elevation can occur in a number of common clinical conditions, including syndrome of inappropriate secretion of AVP, volume depletion, postoperative states, heart failure, cirrhosis, neuroendocrine disorders and trauma. A history of concurrent illness and medication use, assessment of extracellular fluid volume as well as measurement of serum and urine osmolality and urine sodium concentration will help to establish the primary underlying causes. Presence or absence of significant neurologic signs and symptoms must guide treatment. Symptomatic hyponatremia must be treated promptly with 3% hypertonic saline to increase the serum sodium by 1-2 mmol/L per hour until symptoms abate, or a total magnitude of correction of 12 mmol/L in 24 hours or 18 mmol/L in 48 hours is achieved. Initial infusion rate (ml/kg per hour) can be estimated by body weight (kg) x desired rate of increase in sodium (mmol/L per hour). An overly rapid increase in sodium (>12 mmol/L per 24 hours) may result in serious neurologic injury. Fluid restriction and loop diuretic are frequently employed to treat volume overload. Vasopressin receptor antagonists provide prompt and effective water diuresis and increase in serum sodium concentration in both euvolemic and hypervolemic hyponatremia. In this review article, the author introduces a problem-solving approach to dissect the different clinical cases with hyponatremia and presents simple algorithms for the evaluation and management of hyponatremia that are useful at the bedside to improve quality, safety and cost-effectiveness of the patient's care.
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9.
Type 2 pseudohypoaldosteronism: new insights into renal potassium, sodium, and chloride handling.
Proctor, G, Linas, S
American journal of kidney diseases : the official journal of the National Kidney Foundation. 2006;(4):674-93
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10.
Renal sodium handling study in an atypical case of Bartter's syndrome associated with mitochondriopathy and sensorineural blindness.
Menegon, LF, Amaral, TN, Gontijo, JA
Renal failure. 2004;(2):195-7
Abstract
Bartter's syndrome is a disorder that has been linked to mutations in one of three ion transporter proteins: NKCC2 (type I), ROMK (type II) and CCLNKB (type III), which affects a final common pathway that participates in ion transport by thick ascending limb cells. We present an atypical case of mitochondriopathy combined with tubule functional disturbances compatible with Bartter's syndrome and definitive sensorineural blindness. Our patient had a peculiar clinical presentation with signs of salt and volume depletion, low blood pressure and secondary hyperaldosteronism, associated with hypokalemic metabolic alkalosis, hypocalcemia and severe hypomagnesemia, uncommon in genetic forms of Bartter's syndrome. The enhanced absolute and fractional sodium excretion in our patient compared to volunteers was accompanied by increased post-proximal sodium rejection, suggesting a striking ion transport dysfunction in these nephron segments. These findings lead to the Bartter's syndrome diagnosis, accompanied by a suppose mitochondrial tick ascending loop of Henle epithelium dysfunction that may reflect the high energy supplied by mitochondria electron transport chain, required for this nephron segment to maintain normal ion transport.