Long-term neurologic outcome in psychogenic water drinkers with severe symptomatic hyponatremia: the effect of rapid correction

[Consensus recommendations on the diagnosis and treatment of hyponatremia from the Austrian Society for Nephrology 2024]

Hyponatremia is a disorder of water homeostasis. Water balance is maintained by the collaboration of renal function and cerebral structures, which regulate thirst mechanisms and secretion of the antidiuretic hormone. Measurement of serum-osmolality, urine osmolality and urine-sodium concentration help to diagnose the different reasons for hyponatremia. Hyponatremia induces cerebral edema and might lead to severe neurological symptoms, which need acute therapy. Also, mild forms of hyponatremia should be treated causally, or at least symptomatically. An inadequate fast increase of the serum sodium level should be avoided, because it raises the risk of cerebral osmotic demyelination. Basic pathophysiological knowledge is necessary to identify the different reasons for hyponatremia which need different therapeutic procedures.

Clinical characteristics and outcomes of hyponatraemia associated with oral water intake in adults: a systematic review

INTRODUCTION

Excessive water intake is rarely associated with life-threatening hyponatraemia. The aim of this study was to determine the clinical characteristics and outcomes of hyponatraemia associated with excess water intake.

METHODS

This review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All studies (case reports, observational or interventional studies) reporting excess water intake and hyponatraemia in adults (1946-2019) were included.

RESULTS

A total of 2970 articles were identified and 177 were included (88.7% case reports), consisting of 590 patients. The mean age was 46±16 years (95% CI 44 to 48 years), 47% female, 52% had a chronic psychiatric disorder and 31% had no underlying condition. The median volume of water consumed and serum sodium at presentation was 8 L/day (95% CI 8.9 to 12.2 L/day) and 118 mmol/L (95% CI 116 to 118 mmol/L), respectively. The motivator for increased water consumption was psychogenic polydipsia (55%); iatrogenic (13%); exercise (12%); habitual/dipsogenic polydipsia (7%) and other reasons (13%). The clinical features on presentation were severe in 53% (seizures, coma); moderate in 35% (confusion, vomiting, agitation) and mild in 5% (dizziness, lethargy, cognitive deficit) and not reported in 5% of studies. Treatment was supportive in 41% of studies (fluid restriction, treatment of the underlying cause, emergency care), and isotonic and hypertonic saline was used in 18% and 28% of cases, respectively. Treatment-related complications included osmotic demyelination (3%) and rhabdomyolysis (7%), and death occurred in 13% of cases.

CONCLUSION

Water intoxication is associated with significant morbidity and mortality and requires daily intake to substantially exceed population-based recommendations. The limitations of this analysis are the low quality and high risk of bias of the included studies.

PROSPERO REGISTRATION NUMBER

A pre-existing protocol in the international prospective register of systematic reviews was updated to incorporate any new amendments and reregistered at http://www.crd.york.ac.uk/PROSPERO (registration no. CRD42019129809).

Central pontine myelinolysis secondary to rapid correction of hyponatremia historical perspective with Doctor Robert Laureno

OBJECTIVES

Central pontine myelinolysis (CPM) is a neurological disorder characterized by damage to the myelin and oligodendrocytes in the pons. This review focuses on the history of CPM and the discovery of its association with the treatment of hyponatremia.

METHODS

The author reviewed original publications regarding CPM, hyponatremia, and the treatment of hyponatremia. The author interviewed Dr. Robert Laureno who was a pioneer in CPM research with his animal work in dogs.

RESULTS

Animal models demonstrated the role of the rapid correction of hyponatremia as causative of pontine and extrapontine myelinolytic lesions. Nevertheless, the importance of the speed of correction was widely denied. There were years of debates and only slow changes in expert guidelines.

CONCLUSION

CPM occurs as a consequence of a rapid rise in serum sodium in individuals with chronic hyponatremia. It is recommended to increase plasma sodium concentration by no more than 8 to 10 mmol/L per 24 h in chronic hyponatremia.

Tolvaptan in the Management of Acute Euvolemic Hyponatremia After Transsphenoidal Surgery: A Retrospective Single-Center Analysis

INTRODUCTION

Syndrome of inappropriate antidiuresis (SIAD) can be a complication of hypothalamus-pituitary surgery. The use of tolvaptan in this setting is not well established, hence the primary aim of this study was to assess the sodium correction rates attained with tolvaptan compared with standard treatments (fluid restriction and/or hypertonic saline). Furthermore, we compared the length of hospital stay in the two treatment groups and investigated the occurrence of overcorrection and side effects including osmotic demyelination syndrome.

METHODS

We retrospectively reviewed 308 transsphenoidal surgical procedures performed between 2011 and 2019 at our hospital. We selected adult patients who developed post-operative SIAD and recorded sodium monitoring, treatment modalities and outcomes. Correction rates were adjusted based on pre-treatment sodium levels.

RESULTS

Twenty-nine patients (9.4%) developed post-operative SIAD. Tolvaptan was administered to 14 patients (median dose 15 mg). Standard treatments were employed in 14 subjects (fluid restriction n=11, hypertonic saline n=1, fluid restriction and hypertonic saline n=2). Tolvaptan yielded higher adjusted sodium correction rates (12.0 mmolL^-1/24h and 13.4 mmolL^-1/48h) than standard treatments (1.8 mmolL^-1/24h, p<0.001, and 4.5 mmolL^-1/48h, p=0.004, vs. tolvaptan). The correction rate exceeded 10 mmolL^-1/24h or 18 mmolL^-1/48h in 9/14 and 2/14 patients treated with tolvaptan, respectively, and in no patient who received standard treatments. No side effects including osmotic demyelination occurred. Tolvaptan was associated with a shorter hospital stay (11vs.15 days, p=0.01).

CONCLUSIONS

Tolvaptan is more effective than fluid restriction (with or without hypertonic saline) and allows for a shortened hospital stay in patients with SIAD after transsphenoidal surgery. However, its dose and duration should be carefully tailored, and close monitoring is recommended to allow prompt detection of overcorrection.

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 hyponatraemia secondary to primary polydipsia: beware too rapid correction of hyponatraemia

We describe three cases of severe hyponatraemia in the setting of primary polydipsia that were managed in our centre in 2016. Despite receiving different solute loads, large volume diuresis and rapid correction of serum sodium occurred in all cases. Given the potentially catastrophic consequence of osmotic demyelination, we highlight the judicious use of desmopressin and hypotonic fluid infusion to mitigate sodium overcorrection in this setting.

Hyponatremia secondary to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH): therapeutic decision-making in real-life cases

Despite being the most common electrolyte disturbance encountered in clinical practice, the diagnosis and treatment of hyponatremia (defined as a serum sodium concentration <135 mmol/L) remains far from optimal. This is extremely troubling because not only is hyponatremia associated with increased morbidity, length of hospital stay and hospital resource use, but it has also been shown to be associated with increased mortality. The reasons for this poor management may partly lie in the heterogeneous nature of the disorder; hyponatremia presents with a variety of possible etiologies, differing symptomology and fluid volume status, thereby making its diagnosis potentially complex. In addition, a general lack of awareness of the clinical impact of the disorder, a fear of adverse outcomes through overcorrection of sodium levels, and a lack of effective targeted treatments until recent years, may all have contributed to a reticence to actively treat cases of hyponatremia. There is therefore a clear unmet need to further educate physicians on the pathophysiology, diagnosis and management of this important condition. Through the use of a variety of real-world cases of patients with hyponatremia secondary to the syndrome of inappropriate secretion of antidiuretic hormone—a condition that accounts for approximately one-third of all cases of hyponatremia—this supplement aims to provide a comprehensive overview of the challenges faced in diagnosing and managing hyponatremia. These cases will also help to illustrate how some of the limitations of traditional therapies may be overcome with the use of vasopressin receptor antagonists.

Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations

Hyponatremia is a serious, but often overlooked, electrolyte imbalance that has been independently associated with a wide range of deleterious changes involving many different body systems. Untreated acute hyponatremia can cause substantial morbidity and mortality as a result of osmotically induced cerebral edema, and excessively rapid correction of chronic hyponatremia can cause severe neurologic impairment and death as a result of osmotic demyelination. The diverse etiologies and comorbidities associated with hyponatremia pose substantial challenges in managing this disorder. In 2007, a panel of experts in hyponatremia convened to develop the Hyponatremia Treatment Guidelines 2007: Expert Panel Recommendations that defined strategies for clinicians caring for patients with hyponatremia. In the 6 years since the publication of that document, the field has seen several notable developments, including new evidence on morbidities and complications associated with hyponatremia, the importance of treating mild to moderate hyponatremia, and the efficacy and safety of vasopressin receptor antagonist therapy for hyponatremic patients. Therefore, additional guidance was deemed necessary and a panel of hyponatremia experts (which included all of the original panel members) was convened to update the previous recommendations for optimal current management of this disorder. The updated expert panel recommendations in this document represent recommended approaches for multiple etiologies of hyponatremia that are based on both consensus opinions of experts in hyponatremia and the most recent published data in this field.

The assessment and treatment of water imbalance in patients with psychosis

Polydipsia and episodic life-threatening water intoxication remain important clinical problems for a significant portion of persons with schizophrenia. The disorders are associated with increased morbidity and mortality from a number of causes. With a basic understanding of the pathophysiology, one can easily diagnose and assess the clinical conditions. We review here the scope and pathophysiology of disordered water imbalance, including both primary and secondary polydipsia and hyponatremia. Reversible factors and possible interventions are reviewed. Treatment options for preventing water intoxication have expanded from discontinuation of offending agents, targeted fluid restriction, and clozapine therapy to the addition of oral vasopressin antagonists. The latter, however, are extremely potent and must be carefully monitored.

Exercise-associated hyponatremia during winter sports

Exercise-associated hyponatremia (EAH) is hyponatremia that occurs <or= 24 hours after prolonged physical activity. It is a potentially serious complication of marathons, triathlons, and ultradistance events, and can occur in hot and cold environments. Clear evidence indicates that EAH is a dilutional hyponatremia caused by excessive fluid consumption and the inappropriate release of arginine vasopressin. Cerebral and pulmonary edema can cause serious signs and symptoms, including altered mental status, respiratory distress, seizures, coma, and death. Rapid diagnosis and urgent treatment with hypertonic saline is necessary to prevent severe complications or death. Prevention is based on educating athletes to avoid excessive drinking before, during, and after exercise.

Risk factors for rhabdomyolysis in self-induced water intoxication (SIWI) patients

Self-induced water intoxication (SIWI) patients present with various neurological and non-neurological symptoms. However, it is reported that non-neurological manifestations such as rhabdomyolysis are comparatively rare. The mechanism underlying rhabdomyolysis remains controversial. To investigate this further, we evaluated 22 SIWI patients for rhabdomyolysis. We reviewed the records of 22 patients with SIWI and evaluated their clinical characteristics. These patients were divided into the following two groups: Group A with rhabdomyolysis and Group B without it. We compared these groups to study the risk factors underlying the occurrence of rhabdomyolysis. Furthermore, we compared the complications and the duration of hospitalization between the two groups. The maximum serum sodium correction speed per hour, the increase in the serum sodium level in the initial 24 h, and the duration of hospitalization for group A were faster, higher, and longer, respectively, when compared with those in group B. Only group A patients showed complications. The rapid correction of hyponatremia may possibly trigger rhabdomyolysis in SIWI patients.

Hyponatremia treatment guidelines 2007: expert panel recommendations

Although hyponatremia is a common, usually mild, and relatively asymptomatic disorder of electrolytes, acute severe hyponatremia can cause substantial morbidity and mortality, particularly in patients with concomitant disease. In addition, overly rapid correction of chronic hyponatremia can cause severe neurologic deficits and death, and optimal treatment strategies for such cases are not established. An expert panel assessed the potential contributions of aquaretic nonpeptide small-molecule arginine vasopressin receptor (AVPR) antagonists to hyponatremia therapies. This review presents their conclusions, including identification of appropriate treatment populations and possible future indications for aquaretic AVPR antagonists.

Hyponatremia after transsphenoidal surgery for hypothalamo-pituitary tumors

Transient diabetes insipidus is a well-known complication after transsphenoidal surgery (TSS). On the other hand, transient hyponatremia has been reported as being a delayed complication of TSS. Transient hyponatremia has been attributed to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), but the details of hyponatremia have not been clarified. In the present study, we retrospectively reviewed 110 consecutive patients (39 males and 71 females, age 9-80 years) operated on transsphenoidally for pituitary and hypothalamic tumors. We investigated the frequency, time of onset, duration of hyponatremia after TSS, and analyzed possible factors associated with it. A postoperative sodium concentration <135 mEq/l was observed in 29 (26%) patients. Five patients were excluded from this study because their hyponatremia could be due to either overdose of desmopressin or SIADH for meningitis. Therefore, we investigated 24 (22%) patients with hyponatremia in this study. The sodium levels in the patients with hyponatremia ranged from 110 to 134, with a mean of 126.2 +/- 5.3 mEq/l. Hyponatremia was observed on average on postoperative day 9.5 +/- 2.4, the serum sodium levels normalized within 3.8 +/- 1.7 days. Hyponatremia occurred in patients with non-functioning pituitary adenoma (26%, 11/42), Rathke's cleft cyst (29%, 5/17), prolactinoma (31%, 4/13) and acromegaly (15%, 4/27). 18 patients (75%, 6/24) who developed hyponatremia had macrotumor (>10 mm), and 6 patients (25%, 6/24) had microtumor. The plasma arginine vasopressin (AVP) levels in the patients with hyponatremia ranged from 0.21 to 2.1, with a mean of 0.79 +/- 0.46 pg/ml, and the levels were inversely correlated with plasma osmolality (r = -0.80, p = 0.002). The urine to plasma osmolality ratios were >1. All the patients received appropriate hormonal replacement, including hydrocortisone. These data showed that postoperative hyponatremia after TSS was not rare, and the hyponatremia was mainly associated with SIADH. As the hyponatremia could be a life-threatening complication, all patients should be screened for serum electrolytes after TSS.

Treatment of electrolyte disorders in adult patients in the intensive care unit

PURPOSE

The treatment of electrolyte disorders in adult patients in the intensive care unit (ICU), including guidelines for correcting specific electrolyte disorders, is reviewed.

SUMMARY

Electrolytes are involved in many metabolic and homeostatic functions. Electrolyte disorders are common in adult patients in the ICU and have been associated with increased morbidity and mortality, as has the improper treatment of electrolyte disorders. A limited number of prospective, randomized, controlled studies have been conducted evaluating the optimal treatment of electrolyte disorders. Recommendations for treatment of electrolyte disorders in adult patients in the ICU are provided based on these studies, as well as case reports, expert opinion, and clinical experience. The etiologies of and treatments for hyponatremia hypotonic and hypernatremia (hypovolemic, isovolemic, and hypervolemic), hypokalemia and hyperkalemia, hypophosphatemia and hyperphosphatemia, hypocalcemia and hypercalcemia, and hypomagnesemia and hypermagnesemia are discussed, and equations for determining the proper dosages for adult patients in the ICU are provided. Treatment is often empirical, based on published literature, expert recommendations, and the patient's response to the initial treatment. Actual electrolyte correction requires individual adjustment based on the patient's clinical condition and response to therapy. Clinicians should be knowledgeable about electrolyte homeostasis and the underlying pathophysiology of electrolyte disorders in order to provide the optimal therapy to patients.

CONCLUSION

Treatment of electrolyte disorders is often empirical, based on published literature, expert opinion and recommendations, and patient's response to the initial treatment. Clinicians should be knowledgeable about electrolyte homeostasis and the underlying pathophysiology of electrolyte disorders to provide optimal therapy for patients.

Acute psychological stress-induced water intoxication

Excessive water drinking is a recognised feature of schizophrenia. We present here a case of excessive water drinking precipitated by acute psychological stress. A 52-year-old woman, with no previous mental health problems, was found in a state of altered consciousness and was profoundly hyponatraemic. She had consumed excess amount of water due to severe mental stress. She was treated with hypertonic saline followed by fluid restrictions. The water intoxication had caused brain damage which led to behavioural changes and impaired cognition. We describe the pathophysiology of water intoxication.

Evaluation and management of hypo-osmolality in hospitalized patients

Hyponatremia is the most common electrolyte disorder encountered in the clinical setting. Abnormalities of the mechanisms that maintain normal water and sodium metabolism are often present in hospitalized patients, including defects in renal water excretion. All of the current therapeutic approaches in patients with the syndrome of inappropriate antidiuretic hormone secretion and other forms of vasopressin-induced hyponatremia have significant limitations. Studies in animal models and humans have demonstrated that antagonists of the AVP V2 receptor in the kidney are effective in correcting hyponatremia. These new agents have been termed "aquaretics" because of their ability to induce a free water diuresis without the natriuresis or kaliuresis characteristic of diuretic drugs. When approved for clinical use, selective V2, and possibly also combined V1 + V2 receptor antagonists will be helpful in therapy.

Exercise-associated hyponatremia: a review

This paper reviews the extensive literature on hyponatremia, a common and potentially serious complication of ultra-distance exercise. Fluid overload is the likely aetiology. Fluid intakes are typically high in athletes who develop hyponatremia, although hyponatremia can occur with relatively modest fluid intakes. The development of fluid overload and hyponatremia in the presence of a modest fluid intake raises the possibility that athletes with this condition may have an impaired renal capacity to excrete a fluid load. The bulk of evidence favours fluid retention in the extracellular space (dilutional hyponatremia) rather than fluid remaining unabsorbed in the intestine. Female gender is an important risk factor for the development of hyponatremia. Management and prevention of exercise-associated hyponatremia are discussed.

Treatment of Severe Hyponatremia: Conventional and Novel Aspects

Abstract.Hyponatremia is a frequent electrolyte disorder. A hyponatremia is called acute severe (<115 mM) when the duration has been <36 to 48 h. Such patients often have advanced symptoms as a result of brain edema. Acute severe hyponatremia is a medical emergency. It should be corrected rapidly to approximately 130 mM to prevent permanent brain damage. In contrast, in chronic severe hyponatremia (>4 to 6 d), there is no brain edema and symptoms are usually mild. In such patients, a number of authors have recommended a correction rate <0.5 mM/h to approximately 130 mM to minimize the risk of cerebral myelinolysis. Sometimes it is not possible to diagnose whether a severe hyponatremia is acute or chronic. In such cases, an initial imaging procedure is helpful in deciding whether rapid or slow correction should be prescribed. The modalities of treatment of severe hyponatremia have so far consisted of infusions of hypertonic saline plus fluid restriction. In the near future, vasopressin antagonists will become available. Preliminary experience has already demonstrated their efficiency of inducing a sustained water diuresis and a correction of hyponatremia.

Coma and confusional states: emergency diagnosis and management

Coma and confusion signal a failure of brain function with many possible causes. Since many of the potential causes may quickly lead to death or severe disability, it is important to develop a focused and ordered approach to facilitate the rapid diagnosis and early institution of proper therapies. This requires an understanding of the localizing features of the neurologic examination and of the syndromes likely to cause coma and confusion, a predetermined plan for empiric therapies in certain cases of doubt when diagnostic confirmation will be delayed, and a careful consideration of cases when the diagnosis is not revealed by the initial neuroimaging, lumbar puncture, or EEG.

Hypercalcemia and electrolyte disturbances in malignancy

Hypercalcemia and electrolyte abnormalities are common problems in patients with malignancy. In this article we discuss the pathophysiology, clinical features, and management of hypercalcemia, which is the most common metabolic abnormality. We also analyze the electrolyte disturbances that occur in association with malignancy, including hyponatremia, hypokalemia, hypomagnesemia, hypophosphatemia, and hyperkalemia. Recognition and treatment of these disturbances are important parts of the management of patients with malignant disease.

Hyponatremia, convulsions and neuroleptic malignant syndrome in a male with schizoaffective disorder

OBJECTIVE

The aim of the study was to highlight the diagnostic difficulties occurring when hyponatremia presents concurrently with neuroleptic malignant syndrome (NMS). Diagnostic issues in the differentiation between hyponatremia and NMS are discussed.

CLINICAL PICTURE

A case of dilutional hyponatremia (DH) secondary to psychogenic polydipsia (PP) associated with NMS occurring in a male with schizoaffective disorder is described. The clinical picture was complicated by convulsions, perhaps due to clonazepam withdrawal and possible lithium toxicity.

TREATMENT

The patient was treated with supportive medical measures.

OUTCOME

The patient made a full recovery.

CONCLUSIONS

Hyponatremia and NMS have been found to be associated. This association may be due to an undefined common pathogenesis, or may be coincidental. Hyponatremia may also hinder the diagnosis of NMS.

Severe hyponatremia - is rapid correction safe?

In view of the continuous controversy about the treatment of hyponatremia (rapid or slow correction), we retrospectively studied 40 patients with severe hyponatremia (serum level of 120 mmol/L and less). Thirteen cases were acute, the remainder (27) were chronic. The mean rate of correction calculated from the rise of serum sodium over the initial 12 hours in both acute and chronic patients, and over the initial 24 hours in the acute and in the majority of the chronic patients was consistent with the definition of rapid correction (increase of serum sodium of >/=0.5 mmol/L/hr). Six of the acute and three of the chronic patients died during follow-up of six months. All deaths were caused by the underlying diseases or by complications not related to the hyponatremia or its treatment. None of the patients (alive or deceased) developed any clinical features of central pontine and extrapontine myelinolysis (CPM). In some of the studies of rapid correction of hyponatremia, chronic alcoholism was felt to be one of the risk factors in the development of CPM. As our patient population, due to religious reasons, abstained from alcohol intake, our results would suggest that in the absence of chronic alcoholism and its attendant malnutrition, rapid correction of severe hyponatremia is probably safe.

Disordered water homeostasis and cognitive impairment in schizophrenia

To investigate a possible association between disordered water homeostasis and cognitive impairment in schizophrenia, neuropsychological tests were applied to 16 schizophrenic patients with severely deranged water homeostasis and to 16 matched schizophrenic controls. The patients with disordered water homeostasis tended to obtain poorer scores than the controls throughout, the differences being statistically significant for two of the tests (Wechsler Memory Scale Visual Reproduction and Trial Marking Test part A). These results were not ascribable to differences in the duration of the illness, premorbid IQ, medication, or electroconvulsive therapy received, or prominence of any particular symptoms. The results suggest the co-existence of disordered water homeostasis and cognitive impairment in a subset of schizophrenic patients.

Treatment of chronic hyponatremia in rats by intravenous saline: comparison of rate versus magnitude of correction

The role of the rate of correction in the development of demyelinating brain lesions after correction of chronic severe hyponatremia is controversial. It has been recently suggested in rats treated by intravenous (i.v.) hypertonic saline (NaCl) that both the rate and the absolute change in serum sodium represent critical risk factors. However, we previously demonstrated in rats treated by intraperitoneal (i.p.) injections of NaCl that below a threshold of serum sodium rise of 20 mEq/liter/24 hr, only 5% of the brain lesions were recorded, even in rats submitted to a rapid (1 hr) serum sodium increment following the i.p. injection. Working below this threshold (serum sodium rise less than 20 mEq/liter/24 hr) in the present work, allowed us to independently determine the role of the rate in the outcome of the correction. This was done by submitting the rats to a rapid (1 hr) intravenous infusion of NaCl. As a difference between the i.p. and i.v. route in the degree of volume expansion produced by the NaCl administration could also play a role in the pathogenesis of the brain lesions, rats treated with rapid i.v. infusion of NaCl (associated with volume expansion) were compared to a group of rats treated with water restriction (associated to volume contraction) to evaluate the role of volemia on the incidence of neurological damage. Hyponatremia was induced over three days with d-glucose in water and vasopressin. The group 1 was corrected by intravenous (i.v.) infusion of hypertonic saline over one hour.(ABSTRACT TRUNCATED AT 250 WORDS)

Hyponatremic encephalopathy: is central pontine myelinolysis a component?

PURPOSE

Severe hyponatremia is often associated with permanent brain damage. There has been substantial controversy about whether central pontine myelinolysis (CPM), a rare neurologic disorder of uncertain etiology, can complicate either hyponatremia or its therapy. This study was undertaken to determine how often hyponatremic patients with the clinical diagnosis of CPM actually have the disorder as an integral structural component of their encephalopathy.

PATIENTS

Analyses were carried out in 20 patients who had severe symptomatic hyponatremia and a presumptive diagnosis of CPM, based on clinical and/or neuroradiologic findings. All had been referred for neuroradiology consultation. The mean age (+/- SD) was 47 +/- 14 years, the lowest serum sodium level was 104 +/- 8 mM, and 85% of the patients were female. The etiologies were diverse and included postoperative status, thiazide diuretics, polydipsia, infection, acute renal failure, chronic alcoholism with emesis, and beer potomania.

METHODS

The original and subsequent films of 20 patients were reevaluated retrospectively by two neuroradiologists. The clinical course was also reevaluated, and in eight patients, the postmortem brain findings were reviewed. The diagnosis of CPM was made only on the basis of strict criteria relating to either (1) pathologic findings of CPM on postmortem examination; or (2) computed tomographic scan and/or magnetic resonance imaging findings diagnostic of CPM.

RESULTS

No pontine lesions were present in 15 of 20 patients in whom the diagnosis of CPM had initially been made. All 15 had extrapontine demyelinating lesions but the pons was normal. Two others had only lateral pontine lesions, so that only three of 20 patients had definite CPM. All but one of the 20 hyponatremic patients had a definite hypoxic event prior to any therapy with intravenous sodium chloride. The involved brain areas included basal ganglia, thalamus, cortical gray matter, and periventricular white matter, areas often affected by hypoxia. Each of the three patients in whom unequivocal findings of CPM were present had long histories of chronic alcoholism and hepatic cirrhosis.

CONCLUSIONS

These results suggest that: (1) Neither hyponatremic encephalopathy nor its therapy is commonly associated with CPM; (2) Patients with chronic alcoholism who also become hyponatremic can develop pontine demyelinating lesions; (3) Most patients with symptomatic hyponatremia who are diagnosed as having CPM in fact have diffuse cerebral demyelinating lesions with a normal pons; (4) The distribution of cerebral demyelinating lesions in patients with hyponatremic encephalopathy is compatible with hypoxic damage.

Hyponatremia: endocrinologic causes and consequences of therapy

Hyponatremia is a relatively common medical disorder frequently of endocrinologic origin. Although the neurologic signs and symptoms associated with hyponatremia are well known, recent clinical and experimental studies have shown that rapid correction of hyponatremia can in some cases cause a brain-demyelinating disease that can lead to consequences just as severe as those of hyponatremia itself. Understanding the physiologic mechanisms by which the brain adapts to hypoosmolar conditions has led to a better appreciation of the pathogenesis of neurologic dysfunction during both hyponatremia and its therapy, and this in turn has allowed the establishment of rational guidelines for safe therapy of hyponatremic patients. In cases such as this, however, in which a spontaneous rapid water diuresis occurs following a change in hormonal therapy, the rate and magnitude of the increase in serum [Na+J may exceed these guidelines unless active intervention is undertaken to interrupt the induced diuresis.

Cell volume regulation: a review of cerebral adaptive mechanisms and implications for clinical treatment of osmolal disturbances: II

Cerebral cell volume regulatory mechanisms are activated by sustained disturbances in plasma osmolality. Acute hypernatremia causes a predictable shrinkage of brain cells due to the sudden imposition of a plasma-to-cell osmolal gradient. However, during chronic hypernatremia cerebral cell volume is maintained close to the normal range as a result of the accumulation of electrolytes and organic osmolytes including myo-inositol, taurine, glutamine, glycerophosphorylcholine, and betaine. The increased cytosolic level of these molecules is generally accomplished via increased activity of sodium (Na+)-dependent cotransport systems. The slow dissipation of these additional osmotically active solutes from the cell during treatment of hypernatremia necessitates gradual correction of this electrolyte abnormality. Acute hyponatremia leads to cerebral cell swelling and severe neurological dysfunction. However, prolonged hyponatremia is associated with significant reductions in brain cell electrolyte and organic osmolyte content so that cerebral cell volume is restored to normal. While acute hyponatremia can be treated with the administration of moderate doses of hypertonic saline in order to control seizure activity, chronic hyponatremia should be corrected slowly in order to prevent subsequent neurological deterioration. If the rate of correction exceeds 0.5 mmol/l per hour, or if the total increment in serum [Na+] exceeds 25 mmol/l in the first 48 h of therapy, then there is an increased risk of the development of cerebral demyelinating lesions. Chronic hyperglycemia activates the brain cell volume regulatory adaptations in the same manner as hypernatremia. Therefore, during the treatment of diabetic ketoacidosis, it is imperative to restore normoglycemia gradually in order to prevent the occurrence of cerebral edema.(ABSTRACT TRUNCATED AT 250 WORDS)

A review of disorders of water homeostasis in psychiatric patients

Disorders of water homeostasis are common in psychiatric patients and include compulsive water drinking, the syndrome of inappropriate antidiuretic hormone secretion (SIADH), and the syndrome of self-induced water intoxication (SIWI). Although water intoxication was recognized nearly 70 years ago, the physiological basis of these disorders of water metabolism still remains elusive. This review will provide a historical overview, critique current studies on compulsive water drinking and SIWI, discuss possible etiologies, and present current approaches to treatment of these disorders. Because of the complexity of the subject, a review of normal water homeostasis and the SIADH will be included.

Hyponatremia in spinal cord injury

Hypoosmolar hyponatremia (serum Na+ less than 130 mmol/L) has proven a common and incompletely explained phenomenon in the spinal cord injured patient. When present, it has generally been preceded by excessive fluid intake and environmental/dietary factors which reversibly restrict free water excretion. We have attempted to more fully characterize the determinants of SCI-associated hyponatremia by retrospectively analyzing its features and treatment response in a series of 14 hyponatremic SCI patients. In most instances, hyponatremia could be attributed to uncontrolled fluid intake in the presence of an acute or semiacute illness and thus stimuli for non-osmotic releases of arginine vasopressin. Treatment measures generally included administration of 3% saline, with all patients recovering uneventfully from their episode of hyponatremia.