Treatment of Severe Hyponatremia

Active management of hyponatraemia and mortality in older hospitalised patients compared with younger patients: results of a prospective cohort study

INTRODUCTION

Hyponatraemia is associated with increased morbidity and mortality; the aetiology and outcomes of hyponatraemia in older patients have not been defined in prospective studies.

METHODS

A single-centre 9-month prospective observational study in which clinical outcomes in hospitalised patients ≥ 65 years (older patients with hyponatraemia (OP-HN)) and those <65 years (young patients with hyponatraemia (YP-HN)) with hyponatraemia were analysed, and compared with eunatraemic controls (older patients with normonatraemia (OP-NN) and young patients with normonatraemia (YP-NN)).

RESULTS

In total, 1,321 episodes of hyponatraemia in 1,086 patients were included; 437 YP-HN, median age 54 years (IQR 44,60) and 884 OP-HN, median age 77 years (IQR 71,82). A total of 1,120 consecutive eunatraemic control patients were simultaneously recruited; 690 OP-NN, median age 77 years (IQR 71,83) and 430 YP-NN, median age 52 years (IQR 41,58). Euvolaemic hyponatraemia was the commonest cause of hyponatraemia in both age groups (48% in YP-HN and 46% in OP-HN). Sixty-two percent of OP-HN received hyponatraemia-directed treatment within the initial 48 h, compared with 55% of YP-HN, P = 0.01. Despite the greater treatment rates in OP-HN, younger patients were 24% more likely to be discharged with normal plasma sodium concentration (pNa) compared with older patients, relative risk (RR) 1.24 (95% confidence interval (CI) 1.12-1.37), P < 0.001.Using OP-NN as the reference group, the RR of in-hospital death in OP-HN was 2.15 (95% CI 1.3-3.56), P = 0.002. Using YP-NN as the reference group, the RR of in-hospital death in YP-HN was 4.34 (95% CI 1.98-9.56), P < 0.001.

CONCLUSION

Despite greater rates of HN-targeted treatment, the risk of in-hospital death is increased in older hyponatraemic patients compared with older eunatraemic controls. The impact of hyponatraemia on mortality is even greater in younger patients.

Factors affecting prognosis of the patients with severe hyponatremia

INTRODUCTION

Hyponatremia is one of the most common electrolyte abnormalities in clinical practice. Data regarding factors that have impact on mortality of severe hyponatremia and outcomes of its therapeutic management is insufficient. The present study aimed to examine the factors associated with mortality and the outcomes of treatment in patients with severe hyponatremia.

MATERIALS AND METHODS

Patients with serum Na≤115mequiv./L who were admitted to Ordu State Hospital and Ordu University Training and Research Hospital between 2014 and 2018 were included in the study. Demographic and laboratory features, severity of the symptoms, comorbid diseases, medications, and clinical outcome measures of the patients were obtained retrospectively from their medical records. Factors associated with in-hospital mortality, overcorrection and undercorrection were assessed.

RESULTS

A total of 145 patients (median age 69 years and 58.6% female) met inclusion criteria. Diuretic use was the most common etiologic factor for severe hyponatremia that present in 50 (34.5%) patients. Sixty-seven (46.2%) patients had moderately severe while 8 patients (5.5%) had severe symptoms. The median increase in serum Na 24h after admission in the study population was 8.9mequiv./L (-6 to 19). Nonoptimal correction was seen in 92 (63.4%) patients. Hypertonic saline use was associated with overcorrection (OR, 3.07; 95% CI: 1.47-6.39; p=0.002). Avoidance of hypertonic saline (aOR, 2.52; 95% CI: 1.12-5.66; p=0.029) and having neuropsychiatric disorder (aOR, 2.60; 95% CI: 1.10-6.11; p=0.025) were associated with undercorrection. In-hospital mortality rate was 12.4% and having CKD and cancer, undercorrection of sodium and presence of severe symptoms were significantly associated with in-hospital mortality.

CONCLUSION

Severe hyponatremia in hospitalized patients is associated with substantial mortality. The incidence of non-optimal correction of serum Na is high; under-correction, presence of severe symptoms, chronic kidney disease and cancer were the factors that increase mortality rate.

Treatment of symptomatic hyponatremia with hypertonic saline: a real-life observational study

OBJECTIVE

Treatment of symptomatic hyponatremia is not well established. The European guidelines recommend bolus-wise administration of 150 mL of 3% hypertonic saline. This recommendation is, however, based on low level of evidence.

DESIGN

Observational study.

METHODS

Sixty-two consecutive hyponatremic patients admitted to the emergency department or intensive care unit of the University Hospital Wuerzburg were divided in subgroups according to treatment (150 mL bolus of 3% hypertonic saline or conventional treatment) and symptom severity. Treatment target was defined as an increase in serum sodium by 5-10 mEq/L within first 24 h and maximum 8 mEq/L during subsequent 24 h.

RESULTS

Thirty-three out of sixty-two patients (53%) were presented with moderate symptoms and 29/62 (47%) with severe symptoms. Thirty-six were treated with hypertonic saline and 26 conventionally. In the hypertonic saline group, serum sodium increased from 116 ± 7 to 123 ± 6 (24 h) and 127 ± 6 mEq/L (48 h) and from 121 ± 6 to 126 ± 5 and 129 ± 4 mEq/L in the conventional group, respectively. Overcorrection at 24 h occurred more frequent in patients with severe symptoms than with moderate symptoms (38% vs 6%, P < 0.05). Diuresis correlated positively with the degree of sodium overcorrection at 24 h (r = 0.6, P < 0.01). Conventional therapies exposed patients to higher degrees of sodium fluctuations and an increased risk for insufficient sodium correction at 24 h compared to hypertonic saline (RR: 2.8, 95% CI: 1.4-5.5).

CONCLUSION

Sodium increase was more constant with hypertonic saline, but overcorrection rate was high, especially in severely symptomatic patients. Reducing bolus-volume and reevaluation before repeating bolus infusion might prevent overcorrection. Symptoms caused by hypovolemia can be misinterpreted as severely symptomatic hyponatremia and diuresis should be monitored.

Evaluation of Desmopressin in Critically Ill Patients with Hyponatremia Requiring 3% Hypertonic Saline

BACKGROUND

Desmopressin (DDAVP) is often used for hyponatremia management but has been associated with increases in hospital length of stay and duration of hypertonic saline use. The purpose of this study was to evaluate hyponatremia management strategies and their effect on sodium correction in critically ill patients requiring 3% hypertonic saline (3HS).

METHODS

This retrospective, single-center study included critically ill patients with hyponatremia (serum sodium ≤ 125 mEq/L) receiving 3HS from May 31 2015, to May 31 2019. Patients were divided into those who received 3HS for hyponatremia management (HTS) and those who received proactive or reactive DDAVP in addition to 3HS (D-HTS). Patients in either group could receive rescue DDAVP. The primary outcome was the percentage of patients achieving goal sodium correction of 5-10 mEq/L 24 h after 3HS initiation.

RESULTS

Goal sodium correction was achieved in 52.5% of patients in HTS compared to 65.6% of patients in D-HTS (p = 0.21). Patients in HTS had a shorter duration of 3HS infusion (p = 0.0022) with no difference in ICU length of stay, free water intake, urine output, or serum sodium increases 12 and 24 h after receiving 3HS. Overcorrection during any 24- or 48 h period was not statistically different between groups.

CONCLUSION

Patients in HTS and D-HTS had similar rates of achieving goal sodium correction at 24 h. A proactive or reactive DDAVP strategy led to an increase in 3HS duration and total amount with no significant difference in rates of overcorrection. Prospective, randomized studies assessing standardized strategies for hyponatremia management and DDAVP administration are warranted.

Association of intranasal desmopressin therapy with overcorrection of severe hyponatremia: A retrospective, propensity score-based, single-center cohort study

PURPOSE

Severe hyponatremia, defined as serum sodium concentration ([sNa]) ≤ 120 mEq/L, requires aggressive treatment to prevent potentially fatal cerebral edema, seizures, and other sequelae, but overcorrection can also result in life-threatening cerebral hemorrhage and demyelination. We compared the safety and efficacy of nasal desmopressin to conventional management for the prevention of [sNa] overcorrection.

MATERIAL AND METHODS

This retrospective analysis compared 47 patients treated with desmopressin to 17 patients treated conventionally at a university hospital ICU in Japan between 2013 and 2018 using propensity score-based approaches. The primary outcome was safe [sNa] correction, defined as a ≤ 8 mEq/L difference between baseline and follow-up [sNa] at any time within 24h of diagnosis.

RESULTS

The 24-h safe correction rate was significantly greater in the desmopressin group than the conventional treatment group (68% [32/47] vs. 41% [7/17], P = 0.039), and dose-response analysis indicated a positive association between cumulative 24-h desmopressin dose and safe correction at 24 h (P = 0.003). Few overcorrections precluded reliable assessment at 48 h. Exacerbation of hyponatremia was comparable in the two treatment groups.

CONCLUSIONS

Intranasal desmopressin therapy increased the safe correction of severe hyponatremia. Large prospective trials are warranted to confirm this result.

Hyponatremia in childhood urinary tract infection

Acute urinary tract infection (UTI) is the most common bacterial infection in childhood. Although hyponatremia was described in ~ 2/3 of these children, its clinical significance is still unclear. Herein, we evaluated the prevalence and clinical implications of hyponatremia in children hospitalized with a UTI. Medical records of previously healthy children hospitalized between January 2011 and December 2016 with UTI were retrospectively reviewed. Patients (median age 5.5 months) were divided into two groups according to their sodium levels: normonatremia (Na ≥ 135 mEq/L) and hyponatremia (Na < 135 mEq/L). Hyponatremia diagnosed on admission was found in 114/219 children (49%). Hyponatremic patients experienced a more severe disease manifested by a longer hospital stay (3.8 vs 3.4 days, p = 0.003), a higher prevalence of abnormal findings on renal ultrasound (10 vs 2, p = 0.01), higher C-reactive protein (CRP) levels (8.6 vs 3.4 mg/dl, p = <0.001), and a negative correlation between sodium levels and CRP (r = - 0.38, p < 0.001).Conclusion:Hyponatremia occurs frequently in children hospitalized with UTI and is associated with elevated inflammatory markers and a more severe disease course. What is Known: • Hyponatremia, one of the most common electrolyte abnormalities, occurs in approximately 1/3 of hospitalized children and in 2/3 of children with pyelonephritis. • In certain cases of various medical conditions, hyponatremia has been shown to correlate with disease severity. What is New: • Hyponatremia in hospitalized children with UTI correlates with elevated inflammatory markers and a more severe disease course.

A mathematical approach to severe hyponatremia and hypernatremia in renal replacement therapies

Severe dysnatremias are perplexing problems in patients undergoing renal replacement therapy on a chronic or acute basis. The ability to manipulate sodium concentration in the dialysate or replacement solutions is limited. Compounding dialysate or replacement fluids to alter sodium concentration could result in errors. Rapid correction of hyponatremia or hypernatremia due to equilibrium with dialysate or replacement solutions could lead to osmotic demyelination syndrome or cerebral edema respectively. Continuous renal replacement therapy is the preferred dialysis modality in patients with severe dysnatremias. In this article, we present simple formulas to determine the rate of hypotonic or hypertonic solutions needed to mitigate rapid correction of dysnatremias. These formulas can be used readily by the clinician at bedside.

Anticancer Medications and Sodium Dysmetabolism

Therapeutic advances have revolutionised cancer treatment over the last two decades, but despite improved survival and outcomes, adverse effects to anticancer therapy such as dyselectrolytaemias do occur and need to be managed appropriately. This review explores essential aspects of sodium homeostasis in cancer with a focus on alterations arising from anticancer medications. Sodium and water balance are tightly regulated by close interplay of stimuli arising from hypothalamic osmoreceptors, arterial and atrial baroreceptors and the renal juxtaglomerular apparatus. This delicate balance can be disrupted by cancer itself, as well as the medications used to treat it. Some of the conventional chemotherapeutics, such as alkylating agents and platinum-based drugs, can cause hyponatraemia and, on rare occasions, hypernatraemia. Other conventional agents such as vinca alkaloids, as well as newer targeted cancer therapies including small molecule inhibitors and monoclonal antibodies, can cause hyponatraemia, usually as a result of inappropriate antidiuretic hormone secretion. Hyponatraemia can also sometimes occur secondarily to drug-induced hypocortisolism or salt-wasting syndromes. Another atypical but distinct mechanism for hyponatraemia is via pituitary dysfunction induced by immune checkpoint inhibitors. Hypernatraemia is uncommon and occasionally ensues as a result of drug-induced nephrogenic diabetes insipidus. Identification of the aetiology and appropriate management of these conditions, in addition to averting treatment-related problems, can be lifesaving in critical situations.

Sodium Abnormalities in Cardiac Surgery With Cardiopulmonary Bypass in Adults: A Narrative Review

Perioperative sodium abnormalities or dysnatremia is not uncommon in patients presenting for cardiac surgery and is associated with increased morbidity and mortality. Both the disease process of heart failure and its treatment may contribute to abnormalities in serum sodium concentration. Serum sodium is the main determinant of serum osmolality, which in turn affects cell volume. Brain cells are particularly vulnerable to changes in serum osmolality because of the nondistensible cranium. The potentially catastrophic neurologic sequelae of rapidly correcting chronic dysnatremia and the time-sensitive nature of cardiac surgery can make the management of these patients challenging. The use of cardiopulmonary bypass to facilitate surgery adds another layer of complexity in the intraoperative management of sodium and water balance. This narrative review examines the definition and classification of dysnatremia. It also covers the etiology and pathophysiology of dysnatremia, implications during cardiac surgery requiring cardiopulmonary bypass, and the perioperative management of dysnatremia.

[Hyponatremia in older persons (II)-A clear treatment : How to detect tricks and avoid pitfalls]

The aim of this continuing medical education (CME) article (part II) is to describe the particular challenge of the treatment of hyponatremia, which occurs in older patients. This part II follows on from part I concerning the diagnosis in the previous volume. A staged approach is necessary. The best treatment is always when the underlying cause can be eliminated. Hyponatremia in older patients is mainly induced by the syndrome of inappropriate antidiuretic hormone (SIADH) secretion. The authors use a concept for the first, second and third line strategy: (1) changing or discontinuation of drugs, (2) fluid restriction and (3) tolvaptan medication. The algorithm for treatment should be simple. It also contains recommendations for the correction rate. Caution is also needed in order to avoid the occurrence of an osmotic demyelination syndrome (ODS).

Severe Hyponatremia and Continuous Renal Replacement Therapy: Safety and Effectiveness of Low-Sodium Dialysate

RATIONALE & OBJECTIVE

In patients with severe hyponatremia in the setting of acute kidney injury or end-stage kidney disease, continuous renal replacement therapy (CRRT) using standard-sodium (140 mEq/L) fluids may lead to excessively rapid correction of plasma sodium concentration. Use of dialysate and replacement fluids with reduced sodium concentrations can provide a controlled rate of correction of plasma sodium concentration.

STUDY DESIGN

We performed a single-center retrospective analysis of the safety and effectiveness of this approach in patients with plasma sodium concentrations ≤ 126 mEq/L who underwent CRRT for 24 or more hours using low-sodium (119 or 126 mEq/L) dialysate and replacement fluids. Change in plasma sodium level was assessed at 24 and 48 hours after initiation of low-sodium CRRT and at the end of treatment.

SETTING & PARTICIPANTS

Between January 2016 and June 2018, a total of 23 hyponatremic patients underwent continuous venovenous hemodiafiltration using low-sodium dialysate and replacement fluids; 4 patients were excluded from analysis because of CRRT duration less than <24 hours.

RESULTS

The 19 patients included in the study had a mean age of 56 years, 11 (58%) were men, and 15 (79%) were white. The initial mean plasma sodium level was 121 mEq/L and the initial CRRT effluent dose was 27 mL/kg/h. Only 2 (11%) patients had an increase in plasma sodium concentration > 6 mEq/L at 24 hours. Mean changes in plasma sodium levels at 24 and 48 hours and at the time of CRRT discontinuation were 3, 3, and 6 mEq/L, respectively. None of the patients developed osmotic demyelination syndrome.

LIMITATIONS

Key limitations were small sample size and lack of a control group.

CONCLUSIONS

Use of low-sodium dialysate and replacement fluids is a safe strategy for the prevention of overly rapid correction of plasma sodium levels in hyponatremic patients undergoing CRRT.

ENDOCRINOLOGY IN THE TIME OF COVID-19: Management of diabetes insipidus and hyponatraemia

COVID-19 has changed the nature of medical consultations, emphasizing virtual patient counseling, with relevance for patients with diabetes insipidus (DI) or hyponatraemia. The main complication of desmopressin treatment in DI is dilutional hyponatraemia. Since plasma sodium monitoring is not always possible in times of COVID-19, we recommend to delay the desmopressin dose once a week until aquaresis occurs allowing excess retained water to be excreted. Patients should measure their body weight daily. Patients with DI admitted to the hospital with COVID-19 have a high risk for mortality due to volume depletion. Specialists must supervise fluid replacement and dosing of desmopressin. Patients after pituitary surgery should drink to thirst and measure their body weight daily to early recognize the development of the postoperative syndrome of inappropriate antidiuresis (SIAD). They should know hyponatraemia symptoms. The prevalence of hyponatraemia in patients with pneumonia due to COVID-19 is not yet known, but seems to be low. In contrast, hypernatraemia may develop in COVID-19 patients in ICU, from different multifactorial reasons, for example, due to insensible water losses from pyrexia, increased respiration rate and use of diuretics. Hypernatraemic dehydration may contribute to the high risk of acute kidney injury in COVID-19. IV fluid replacement should be administered with caution in severe cases of COVID-19 because of the risk of pulmonary oedema.

Hemodialysis treatment in patients with severe electrolyte disorders: Management of hyperkalemia and hyponatremia

Significant deviations of serum potassium and sodium levels are frequently observed in hospitalized patients and are both associated with increased all‐cause and cardiovascular mortality. The presence of acute or chronic renal failure facilitates the pathogenesis and complicates the clinical management. In the absence of reliable outcome data in the context of dialysis prescription, requirement of renal replacement therapy in patients with severe electrolyte disturbances constitutes a therapeutic challenge. Recommendations for intradialytic management are based on pathophysiologic reasoning and clinical observations only, and as such, heterogeneous and limited to expert opinion level. This article reviews current strategies for the management of severe hyperkalemia and hyponatremia in hemodialysis patients.

Hyponatremia in patients with cancer

PURPOSE OF REVIEW

Hyponatremia is seen commonly in patients with cancer and is associated with increased mortality and morbidity. Understanding the proper diagnosis and therapy of cancer-associated hyponatremia is critical to ensure improved outcomes.

RECENT FINDINGS

The most common cancers associated with hyponatremia are the various forms of lung cancer with incidences approaching 25-45%. The most common causes of hyponatremia in cancer patients are the syndrome of inappropriate antidiuretic hormone secretion [syndrome of inappropriate antidiuretic hormone (ADH)] and volume depletion. Proper diagnosis rests on clinical information supplemented by laboratory studies and is critical to ensure appropriate therapy. In recent years, the development of drugs that specifically antagonize the vasopressin type 2 receptor in the distal tubule have offered targeted and highly effective therapies for syndrome of inappropriate ADH.

SUMMARY

Hyponatremia in cancer patients generally indicates advanced or severe disease but proper therapy that targets the underlying process can improve outcomes.

Pharmacotherapy of sodium disorders in neurocritical care

PURPOSE OF REVIEW

To describe the pathophysiology and pharmacotherapy of dysnatremia in neurocritical care patients.

RECENT FINDINGS

Sodium disorders may affect approximately half of the neurocritical care patients and are associated with worse neurological outcome and increased risk of death. Pharmacotherapy of sodium disorders in neurocritical care patients may be challenging and is guided by a careful investigation of water and sodium balance.

SUMMARY

In case of hyponatremia, because of excessive loss of sodium, fluid challenge with isotonic solution, associated with salt intake is the first-line therapy, completed with mineralocorticoids if needed. In case of hyponatremia because of SIADH, fluid restriction is the first-line therapy followed by urea if necessary. Hypernatremia should always be treated with hypotonic solutions according to the free water deficit, associated in case of DI with desmopressin. The correction speed should take into consideration the symptoms associated with dysnatremia and the rapidity of the onset.

Equivalent Efficacy and Decreased Rate of Overcorrection in Patients With Syndrome of Inappropriate Secretion of Antidiuretic Hormone Given Very Low-Dose Tolvaptan

Rationale & Objective

Euvolemic hyponatremia often occurs due to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Vasopressin 2 receptor antagonists may be used to treat SIADH. Several of the major trials used 15 mg of tolvaptan as the lowest effective dose in euvolemic and hypervolemic hyponatremia. However, a recent observational study suggested an elevated risk for serum sodium level overcorrection with 15 mg of tolvaptan in patients with SIADH.

Study Design

A retrospective chart review study comparing outcomes in patients with SIADH treated with 15 versus 7.5 mg of tolvaptan.

Settings & Participants

Patients with SIADH who were treated with a very low dose of tolvaptan (7.5 mg) at a single center compared with patients using a 15-mg dose from patient-level data from the observational study described previously.

Predictors

Tolvaptan dose of 7.5 versus 15 mg daily.

Outcomes

Appropriate response to tolvaptan, defined as an initial increase in serum sodium level > 3 mEq/L, and overcorrection of serum sodium level (>8 mEq/L per day, and >10 mEq/L per day in sensitivity analyses).

Analytical Approach

Descriptive study with additional outcomes compared using t tests and F-tests (Fischer's Exact χ2 Test).

Results

Among 18 patients receiving 7.5 mg of tolvaptan, the mean rate of correction was 5.6 ± 3.1 mEq/L per day and 2 (11.1%) patients corrected their serum sodium levels by >8 mEq/L per day, with 1 of these increasing by >12 mEq/L per day. Of those receiving tolvaptan 7.5 mg, 14 had efficacy, with increases ≥ 3 mEq/L; similar results were seen with the 15-mg dose (21 of 28). There was a statistically significant higher chance of overcorrection with the use of 15 versus 7.5 mg of tolvaptan (11 of 28 vs 2 of 18; P = 0.05; and 10 of 28 vs 1 of 18; P = 0.03, for >8 mEq/L per day and >10 mEq/L per day, respectively).

Limitations

Small sample size, retrospective, and nonrandomized.

Conclusions

Tolvaptan, 7.5 mg, daily corrects hyponatremia with similar efficacy and less risk for overcorrection in patients with SIADH versus 15 mg of tolvaptan.

Treatment of severe symptomatic hyponatremia

Hyponatremia is the most common electrolyte abnormality seen in the hospital. Severe symptomatic hyponatremia is associated with grave consequences including cerebral edema, brain herniation, seizures, obtundation, coma, and respiratory arrest. However, rapid correction of chronic severe hyponatremia may lead to osmotic demyelination syndrome (ODS) and even death. Given the serious consequences of severe hyponatremia or its inadvertent overcorrection, it is of paramount importance for the clinician to be aware of the various scenarios in which hyponatremic patients can present and tailor the management strategies accordingly. We present here a case of severe hyponatremia of unknown duration with the presenting plasma sodium level of 95 mmol/L and use it to illustrate the various treatment strategies - proactive, reactive, or rescue therapy - along with the physiological basis to support these approaches.

Managing hyponatremia

Despite the high incidence of hyponatremia, the correct approach to management, particularly in patients with severe hyponatremia (serum sodium of 120 mEq/L or less), is controversial. This article reviews two major consensus guidelines and recent studies that can help clinicians make evidence-based treatment decisions and reduce patient risk for iatrogenic osmotic demyelination from overly aggressive treatment.

Continuous Versus Bolus Infusion of Hypertonic Saline in the Treatment of Symptomatic Hyponatremia Caused by SIAD

BACKGROUND

Acute hyponatremia is a medical emergency that confers high mortality, attributed primarily to cerebral edema. Expert guidelines advocate the use of intravenous boluses of hypertonic saline rather than traditional continuous infusion to achieve a faster initial rise in plasma sodium (pNa) concentration. However, there is a limited evidence base for this recommended policy change.

METHODS

We prospectively assessed the clinical and biochemical outcomes in patients treated for symptomatic hyponatremia caused by syndrome of inappropriate antidiuresis in response to intravenous bolus treatment with 3% saline (100 mL, repeated up to two more times) and compared the outcomes to retrospective data from patients treated with continuous intravenous infusion of low-dose (20 mL/h) 3% saline.

RESULTS

Twenty-two patients were treated with bolus infusion and 28 with continuous infusion. Three percent saline bolus caused more rapid elevation of pNa at 6 hours [median (range) 6 (2 to11) vs 3 (1 to 4) mmol/L, P < 0.0001], with a concomitant improvement in Glasgow Coma Scale (GCS) [median (range) 3 (1 to 6) vs 1 (-2 to 2), P < 0.0001] at 6 hours. Median pNa concentration was similar at 24 hours in the two treatment groups. The administration of a third saline bolus was associated with greater need for dextrose/dDAVP to prevent overcorrection (OR 24; P = 0.006). There were no cases of osmotic demyelination in either group.

CONCLUSION

Three percent saline bolus produces faster initial elevation of pNa than continuous infusion with quicker restoration of GCS, and without osmotic demyelination. Frequent electrolyte monitoring, and judicious intervention with dDAVP is required to prevent overcorrection with bolus therapy.

Diabetes insipidus

Diabetes insipidus (DI) is a disorder characterized by excretion of large amounts of hypotonic urine. Central DI results from a deficiency of the hormone arginine vasopressin (AVP) in the pituitary gland or the hypothalamus, whereas nephrogenic DI results from resistance to AVP in the kidneys. Central and nephrogenic DI are usually acquired, but genetic causes must be evaluated, especially if symptoms occur in early childhood. Central or nephrogenic DI must be differentiated from primary polydipsia, which involves excessive intake of large amounts of water despite normal AVP secretion and action. Primary polydipsia is most common in psychiatric patients and health enthusiasts but the polydipsia in a small subgroup of patients seems to be due to an abnormally low thirst threshold, a condition termed dipsogenic DI. Distinguishing between the different types of DI can be challenging and is done either by a water deprivation test or by hypertonic saline stimulation together with copeptin (or AVP) measurement. Furthermore, a detailed medical history, physical examination and imaging studies are needed to ensure an accurate DI diagnosis. Treatment of DI or primary polydipsia depends on the underlying aetiology and differs in central DI, nephrogenic DI and primary polydipsia.

Posterior pituitary dysfunction following traumatic brain injury: review

Neurohypophysial dysfunction is common in the first days following traumatic brain injury (TBI), manifesting as dysnatremia in approximately 1 in 4 patients. Both hyponatremia and hypernatremia can impair recovery from TBI and in the case of hypernatremia, there is a significant association with excess mortality. Hyponatremia secondary to syndrome of inappropriate antidiuretic hormone secretion (SIAD) is the commonest electrolyte disturbance following TBI. Acute adrenocorticotropic hormone (ACTH)/cortisol deficiency occurs in 10-15% of TBI patients and can present with a biochemical picture identical to SIAD. For this reason, exclusion of glucocorticoid deficiency is of particular importance in post-TBI SIAD. Cerebral salt wasting is a rare cause of hyponatremia following TBI. Hyponatremia predisposes to seizures, reduced consciousness, and prolonged hospital stay. Diabetes insipidus (DI) occurs in 20% of cases following TBI; where diminished consciousness is present, appropriate fluid replacement of renal water losses is occasionally inadequate, leading to hypernatremia. Hypernatremia is strongly predictive of mortality following TBI. Most cases of DI are transient, but persistent DI is also predictive of mortality, irrespective of plasma sodium concentration. Persistent DI may herald rising intracranial pressure due to coning. True adipsic DI is rare following TBI, but patients are vulnerable to severe hypernatremic dehydration, exacerbation of neurologic deficits and hypothalamic complications, therefore clinicians should be aware of this possible variant of DI.

Allostasis and the Clinical Manifestations of Mild to Moderate Chronic Hyponatremia: No Good Adaptation Goes Unpunished

When homeostatic regulatory systems are unable to maintain a normal serum sodium concentration, the organism must adapt to demands of a disordered internal environment, a process known as "allostasis." Human cells respond to osmotic stress created by an abnormal serum sodium level with the same adaptations used by invertebrate organisms that do not regulate body fluid osmolality. To avoid intolerable changes in their volume, cells export organic osmolytes when exposed to a low serum sodium concentration and accumulate these intracellular solutes when serum sodium concentration increases. The brain's adaptation to severe hyponatremia (serum sodium < 120 mEq/L) has been studied extensively. However, adaptive responses occur with less severe hyponatremia and other tissues are affected; the consequences of these adaptations are incompletely understood. Recent epidemiologic studies have shown that mild (sodium, 130-135 mEq/L) and moderate (sodium, 121-129 mEq/L) chronic hyponatremia, long thought to be inconsequential, is associated with adverse outcomes. Adaptations of the heart, bone, brain, and (possibly) immune system to sustained mild to moderate hyponatremia may adversely affect their function and potentially the organism's survival. This review explores what is known about the consequences of mild to moderate chronic hyponatremia and the potential benefits of treating this condition.

Severe Symptomatic Hyponatremia Secondary to Escitalopram-Induced SIADH: A Case Report with Literature Review

Hyponatremia is a well-known medication related side effect of selective serotonin reuptake inhibitors; despite its association with escitalopram, the newest SSRI is very rare. We did a review of literature and came across only 14 reported case of this rare association of SIADH with escitalopram. We hereby report a case of a 93-year-old female who presented with generalized tonic-clonic seizure and was diagnosed with severe hyponatremia due to escitalopram-induced syndrome of inappropriate antidiuretic hormone secretion (SIADH). With this article, we want to emphasize clinicians about this rare side effect of escitalopram use and look for the risk factors leading to SIADH.

Hypokalemia: a clinical update

Hypokalemia is a common electrolyte disturbance, especially in hospitalized patients. It can have various causes, including endocrine ones. Sometimes, hypokalemia requires urgent medical attention. The aim of this review is to present updated information regarding: (1) the definition and prevalence of hypokalemia, (2) the physiology of potassium homeostasis, (3) the various causes leading to hypokalemia, (4) the diagnostic steps for the assessment of hypokalemia and (5) the appropriate treatment of hypokalemia depending on the cause. Practical algorithms for the optimal diagnostic, treatment and follow-up strategy are presented, while an individualized approach is emphasized.