Evolution and evolving resolution of controversy over existence and prevalence of cerebral/renal salt wasting

Chronic Hyponatremia: The Role of Reset Osmostat in Patients with Suspected SIAD

Background: Hyponatremia is common, particularly among the elderly. Reset osmostat (RO) serves as an alternative diagnosis to the syndrome of inappropriate antidiuresis (SIAD). There is limited information available regarding the prevalence of RO in outpatient clinics and hospital wards. The water-diluting test is considered the gold standard for the diagnosis of RO. The recent identification of copeptin provides an additional diagnostic marker alongside the utilization of fractional uric acid excretion. Methods: This single-center, prospective, observational study involved eight patients undergoing a water-diluting test over a study period of 2 years. Results: Reset osmostat was diagnosed in 50% of cases, while SIAD was confirmed in one patient. The tests were inconclusive for the remaining three patients. Conclusions: Our findings suggest that reset osmostat, despite its rarity, is a plausible diagnosis in chronic hyponatremia. The relevance of copeptin could not be confirmed in this study. Moreover, fractional uric acid excretion might be as effective as the water-diluting test in diagnosing reset osmostat.

Updates in hyponatremia and hypernatremia

PURPOSE OF REVIEW

Hyponatremia and hypernatremia are commonly encountered electrolyte abnormalities that require timely and careful intervention, as they can be associated with significant morbidity and mortality.

RECENT FINDINGS

This review article addresses the etiology, presentation, diagnosis, and management of both hyponatremia and hypernatremia, emphasizing the latest advancements and emerging trends in pediatric care.

SUMMARY

A methodical approach is needed to accurately assess and treat hyponatremia and hypernatremia. Both conditions continue to rely on serum and urine testing, however newer tests such as copeptin and stimulated testing may hold promise to further refine testing in the future.

Cerebral Salt Wasting Syndrome in the Setting of Hypovolemic Isotonic Hyponatremia: A Case Report

Cerebral salt wasting syndrome (CSWS) is a condition characterized as the loss of sodium secondarily due to an intracranial process, commonly following the neurosurgical resection of mass lesions. This condition leads to a hypovolemic hypotonic hyponatremia. The identification of this syndrome is often mistaken for syndrome of inappropriate anti-diuretic hormone (SIADH). The treatment for both conditions is vastly different. Given the risk of mortality when balancing sensitivities in hyponatremia and its commonality in clinical scenarios, a distinction is crucial. In this case report, we discuss a patient who presented with CSWS following the surgical resection of a pituitary adenoma. She subsequently developed hypernatremia, treated with DDAVP for the suspicion of diabetes insipidus. Once this was discontinued, she further presented with worsening hyponatremia. This hyponatremia persisted even after the discontinuation of DDAVP, with no significant intervention leading to hypovolemic isotonic hyponatremia, supporting a diagnosis of CSWS. Our findings stress the importance of the proper identification of hyponatremia with guided treatment following neurosurgical intervention and give physicians an insight into the anomalies of hyponatremia that should be further discussed.

Altered Serum Uric Acid Levels in Kidney Disorders

Serum uric acid levels are altered by kidney disorders because the kidneys play a dominant role in uric acid excretion. Here, major kidney disorders which accompany hyperuricemia or hypouricemia, including their pathophysiology, are discussed. Chronic kidney disease (CKD) and hyperuricemia are frequently associated, but recent clinical trials have not supported the pathogenic roles of hyperuricemia in CKD incidence and progression. Diabetes mellitus (DM) is often associated with hyperuricemia, and hyperuricemia may be associated with an increased risk of diabetic kidney disease in patients with type 2 DM. Sodium-glucose cotransporter 2 inhibitors have a uricosuric effect and can relieve hyperuricemia in DM. Autosomal dominant tubulointerstitial kidney disease (ADTKD) is an important hereditary kidney disease, mainly caused by mutations of uromodulin (UMOD) or mucin-1 (MUC-1). Hyperuricemia and gout are the major clinical manifestations of ADTKD-UMOD and ADTKD-MUC1. Renal hypouricemia is caused by URAT1 or GLUT9 loss-of-function mutations and renders patients susceptible to exercise-induced acute kidney injury, probably because of excessive urinary uric acid excretion. Hypouricemia derived from renal uric acid wasting is a component of Fanconi syndrome, which can be hereditary or acquired. During treatment for human immunodeficiency virus, hepatitis B or cytomegalovirus, tenofovir, adefovir, and cidofovir may cause drug-induced renal Fanconi syndrome. In coronavirus disease 2019, hypouricemia due to proximal tubular injury is related to disease severity, including respiratory failure. Finally, serum uric acid and the fractional excretion of uric acid are indicative of plasma volume status; hyperuricemia caused by the enhanced uric acid reabsorption can be induced by volume depletion, and hypouricemia caused by an increased fractional excretion of uric acid is the characteristic finding in syndromes of inappropriate anti-diuresis, cerebral/renal salt wasting, and thiazide-induced hyponatremia. Molecular mechanisms by which uric acid transport is dysregulated in volume or water balance disorders need to be investigated.

Hyperlactatemia and other perioperative metabolic disturbances in neuroanesthesia

PURPOSE OF REVIEW

The concept of 'brain-body cross-talking' has gained growing interest in the last years. The understanding of the metabolic disturbances (e.g., hypernatraemia/hyponatraemia and hyperlactatemia) in neurosurgical patients has improved during the last years.

RECENT FINDINGS

The impact of elevated lactate without acidosis in neurosurgical patients remains controversial. The pathophysiology of inappropriate secretion of antidiuretic hormone (SIADH) has become clearer, whereas the diagnosis of cerebral salt wasting should be used more carefully.

SUMMARY

These findings will contribute to a better understanding of the pathophysiology involved and enable better prevention and therapy where possible in clinical practice.

Use of Urine Electrolytes and Urine Osmolality in the Clinical Diagnosis of Fluid, Electrolytes, and Acid-Base Disorders

We discuss the use of urine electrolytes and urine osmolality in the clinical diagnosis of patients with fluid, electrolytes, and acid-base disorders, emphasizing their physiological basis, their utility, and the caveats and limitations in their use. While our focus is on information obtained from measurements in the urine, clinical diagnosis in these patients must integrate information obtained from the history, the physical examination, and other laboratory data.

Challenges of Diagnosing Hyponatremic Syndromes in Pulmonary and Extra Pulmonary Tuberculosis

Introduction Pulmonary tuberculosis (PTB) is one of the rare pulmonary infections causing hyponatremia (serum sodium ˂135 mmol/L) and severe hyponatremia (serum sodium ˂125 mmol/L). Although the major cause of hyponatremia in TB patients is syndrome of inappropriate antidiuretic hormone (SIADH) secretion, cerebral salt wasting syndrome (CSWS) can occur and requires evidence of inappropriate urinary salt losses and reduced arterial blood volume. Adrenal insufficiency (AI) is rare in TB with scanty literature describing it. The two reported cases highlight three possible causes of severe symptomatic hyponatremia in TB pleural effusion and disseminated TB, their treatment modalities, and the need to increase the index of suspicion to diagnose TB hyponatremia in children.

Case Report Case 1: a 10-year-old girl with TB pleural effusion who developed recurrent hyponatremia in the first few weeks of anti-TB treatment which was responsive to sodium correction. Case 2: an 8-year-old girl presenting to our facility with presumptive TB. She deteriorated over several months and progressed to disseminated TB with AI.

Discussion Early diagnosis and prompt and correct treatment of TB hyponatremia cannot be overemphasized, as AI, SIADH secretion, and CSWS, each require different therapeutic regimens, most especially AI on its own poses a huge clinical challenge.

Conclusion A high index of suspicion, with intensified case finding at all levels of care, is necessary to identify and manage children with TB hyponatremia because early diagnosis and prompt treatment is lifesaving.

Salt wasting syndrome in brain trauma patients: a pathophysiologic approach using sodium balance and urinary biochemical analysis

BACKGROUND

To explore the underlying mechanisms leading to the occurrence of hyponatremia and enhanced urinary sodium excretion in brain trauma patients using sodium balance and urinary biochemical analysis.

METHODS

We conducted a retrospective analysis of a local database prospectively collected in 60 brain trauma patients without chronic renal dysfunction. Metabolic and hemodynamic parameters were averaged over three consecutive periods over the first seven days after admission. The main outcome investigated in this study was the occurrence of at least one episode of hyponatremia.

RESULTS

Over the study period, there was a prompt decrease in sodium balance (163 ± 193 vs. -12 ± 154 mmol/day, p < 0.0001) and free water clearance (- 0.7 ± 0.7 vs. -1.8 ± 2.3 ml/min, p < 0.0001). The area under the ROC curves for sodium balance in predicting the occurrence of hyponatremia during the next period was 0.81 [95% CI: 0.64-0.97]. Variables associated with averaged urinary sodium excretion were sodium intake (R² = 0.26, p < 0.0001) and fractional excretion of urate (R² = 0.15, p = 0.009). Urinary sodium excretion was also higher in patients with sustained augmented renal clearance over the study period (318 ± 106 vs. 255 ± 135 mmol/day, p = 0.034).

CONCLUSION

The decreased vascular volume resulting from a negative sodium balance is a major precipitating factor of hyponatremia in brain trauma patients. Predisposing factors for enhanced urinary sodium excretion were high sodium intake, high fractional excretion of urate and augmented renal clearance over the first seven days after ICU admission.