Hyponatremia in Cirrhosis: Implications for Liver Transplantation.

Hyponatremia in cirrhosis is defined as a serum sodium level ≤130 mEq/L and occurs in approximately 22% of patients with cirrhosis. The appearance of hyponatremia in patients with cirrhosis portends a poor prognosis before liver transplantation (LT), independent of the Model for End-Stage Liver Disease (MELD) score. With the development of the MELD-sodium score, the management of hyponatremia has become more relevant than ever before. Overcorrection of hyponatremia before LT or perioperatively can lead to the devastating neurologic condition known as osmotic demyelination syndrome, which is often irreversible and fatal. Therefore, the most important tenet of hyponatremia is to avoid correcting the serum sodium by ≥8 mEq/L in a 24-hour period. Treatment of hyponatremia is highly challenging. The vast majority of patients with cirrhosis have chronic hypervolemic hyponatremia. Fluid restriction increases serum sodium levels, but tolerance and compliance are significant barriers. Diuretic withdrawal is helpful but contributes to worsening fluid overload. There are limited data to support use of intravenous concentrated albumin solutions. The use of the arginine vasopressin antagonists ("vaptans") is contentious; however, they may have a limited role. Risk factors for intraoperative overcorrection of serum sodium include increased utilization of packed red blood cell and fresh frozen plasma transfusions, which are often unavoidable. Intraoperative management is evolving, and more data are needed in regard to the use of sodium-reduced continuous venovenous hemofiltration and the use of trishydroxymethylaminomethane (Tris) to avoid excess sodium rebound. A thorough discussion of the current treatment options before and during LT is given in this review.

Hyponatremia in the neurocritical care patient: An approach based on current evidence.

In the neurocritical care setting, hyponatremia is the commonest electrolyte disorder, which is associated with significant morbimortality. Cerebral salt wasting and syndrome of inappropriate antidiuretic hormone have been classically described as the 2 most frequent entities responsible of hyponatremia in neurocritical care patients. Nevertheless, to distinguish between both syndromes is usually difficult and useless as volume status is difficult to be determined, underlying pathophysiological mechanisms are still not fully understood, fluid restriction is usually contraindicated in these patients, and the first option in the therapeutic strategy is always the same: 3% hypertonic saline solution. Therefore, we definitively agree with the current concept of "cerebral salt wasting", which means that whatever is the etiology of hyponatremia, initially in neurocritical care patients the treatment will be the same: hypertonic saline solution.

[Central pontine myelinolysis developed during alcohol withdrawal in a chronic alcoholic with hyperosmolar hyperglycemic state].

We present a 46-year-old man with central pontine myelinolysis (CPM). He had been diagnosed with diabetes mellitus and chronic pancreatitis. He had drunk more than 1.2 l of Japanese sake daily for 20 years and more. He developed slight reduction of consciousness, dysarthria and truncal ataxia 7 days after he stopped drinking. The laboratory data on admission showed hyperosmolar hyperglycemic state, according to the following findings; glucose 1,058 mg/dl, serum osmolality 328 mOsm/l and serum sodium 119 mEq/l. According as administration of acetic Ringer's solution and insulin injection, the laboratory data 14 hours after admission showed glucose 235 mg/dl, serum osmolality 290 mOsm/l and serum sodium 131 mEq/l. The initial diffusion weighted images (DWI) on MRI revealed a small high signal intensity spot in the pons. The second DWI after 14 days revealed a trident-shaped hyperintensity in the pons that was compatible with CPM. His symptoms showed no remarkable changes, but susceptibility weighted images of MRI after 4 months revealed low signal intensity area in the CPM lesion that indicated pontine hemorrhage. We speculate that marked fluctuation of serum osmotic pressure associated with the rapid change of the serum glucose had a significant role in the pathogenesis of the present case. Therefore, we recommend gradual correction of serum glucose and serum osmolality to maintain less than 12 mEq/l/day as correction of chronic hyponatremia in to prevent and ameliorate pathologic condition of CPM.

Sodium-reduced continuous venovenous hemodiafiltration (CVVHDF) for the prevention of central pontine myelinolysis (CPM) in hyponatremic patients scheduled for orthotopic liver transplantation.

Two patients in end-stage hepatic failure presented for orthotopic liver transplantation with longstanding severe hyponatremia (121 and 122 mmol/L). Both patients underwent liver transplantation with the concomitant use of continuous venovenous hemodiafiltration. Replacement and dialysate solutions were prepared individually to contain a sodium level that was individually considered safe with regard to the development of central pontine myelinolysis. The sodium increase in both patients was within the expected and planned limits despite a situation of mass transfusion. Both patients did well postoperatively and neither patient suffered neurological deficits.

Current perspectives in the management of hyponatremia: prevention of CPM.

Central pontine myelinolysis represents a relatively contemporary neurologic entity in which an imbalance of water relative to alterations in the body's electrolyte levels induces characteristic demyelination in the central part of the basis pontis as well as extrapontine sites. The clinical scenario is typically one of chronic hyponatremia followed by a rapid correction to normonatremic or hypernatremic levels. This seemingly innocuous series of events can result in fatal consequences. Better understanding of the pathophysiology of this disorder provides avenues for clinical management, including use of steroids and organic osmoles, such as myoinositol. More recently, the introduction of a newer class of pharmacologic agents - the vasopressin receptor antagonists, known as vaptans, which induce an excretion of increased amounts of water without altered sodium or potassium excretion - is of particular interest. This review addresses classic approaches to the management of this disorder along with a discussion of newer pharmacologic agents that may become important therapeutic interventions in the clinical management of the osmotic myelinolysis syndrome.

[Central pontine and extrapontine myelinolysis (review)].

The paper addresses the etiopathogenetic, clinical and therapeutical peculiarities of central pontine and extrapontine myelinosis. The causes of these disorders are analyzed. A role of the inadequate correction of hyponatremia, especially in alcoholism, in the genesis of myelinosis is emphasized. Neurological disorders in such patients are reviewed with highlighting the clinical and prognostic heterogeneity of central pontine and extrapontine myelinosis. The author suggests the recommendations on patient management and perfect correction of hyponatremia.

[Prevention of central pontine myelinolysis in rats by early treatment with dexamethasone].

OBJECTIVE: To explore the effect and mechanism of dexamethasone (DEX) in the prevention of central pontine myelinolysis (CPM) in rats. METHODS: Hyponatremia was induced in rat by subcutaneous injection of Vasopressin Tannate and intraperitoneal injection of 2.5% dextrose in water for 3 d, the rats of Group A received a bolus of 1 mol/L NaCl (2 ml/kg) and DEX (5 mg/kg) simultaneously at the 4th day; the rats of Group B were treated with DEX after 24 h of the injection of 1 mol/L NaCl; the rats in Group C received a bolus of 1 mol/L NaCl and saline simultaneously; Group D was the control group. The demyelinative lesions were evaluated by myelin staining. The Evans blue (EB) contents of brain were detected to evaluate the blood-brain-barrier permeability after rapid correction of hyponatremia. The expression of inducible nitric oxide synthase (iNOS) in brains was evaluated by Western blotting. RESULT: CPM was induced successfully in rats. The EB contents of Group A, B and C had no significant difference at 0 h after injection of hypertonic saline compared with Group D. The EB contents of Group C began to increase significantly at 6 h after injection of hypertonic saline, peaked at 24 h; the expression of iNOS in brains began to increase after 3 h after the rapid correction of hyponatremia. The rate of morbidity in Group C was 66.7%. The demyelinative lesions were rarely seen in Group A, the EB contents of brain decreased significantly compared with Group C at the same time point (P<0.05), the iNOS expression was also inhibited. DEX could not prevent the attack of CPM at Group B, the rate of morbidity (75%) had no significant difference compared with Group C (P>0.05). CONCLUSION: Early treatment with DEX can protect blood-brain-barrier and inhibit the expression of iNOS to prevent the attack of CPM.

A study of the pathogenesis and prevention of central pontine myelinolysis in a rat model.

The development of central pontine myelinolysis was studied in rats. Severe hyponatraemia was induced using vasopressin tannate and 2.5% dextrose in water and then rapidly corrected with hypertonic saline alone, hypertonic saline and dexamethasone simultaneously, or hypertonic saline plus dexamethasone 24 h later. The permeability of the blood-brain barrier was evaluated using the extravasation of Evans blue dye and the expression of inducible nitric oxide synthase (iNOS) in the brain was examined using Western blot analysis. Histological sections were examined for demyelinating lesions. In rats receiving hypertonic saline alone, Evans blue dye content and expression of iNOS began to increase 6 and 3 h, respectively, after rapid correction of hyponatraemia and demyelinating lesions were seen. When dexamethasone was given simultaneously with hypertonic saline, these increases were inhibited and demyelinating lesions were absent. These effects were lost if dexamethasone injection was delayed. Disruption of the blood-brain barrier and increased iNOS expression may be involved in the pathogenesis of central pontine myelinolysis, and early treatment with dexamethasone may help prevent the development of central pontine myelinolysis.

Mechanisms and therapy of osmotic demyelination.

Central pontine myelinolysis (CPM) is a rare but serious demyelinative disease that is associated with rapid correction of chronic hyponatremia. Disruption of the blood-brain barrier (BBB) following a rapid increase in serum sodium concentration is considered to play a critical role in the pathogenesis of osmotic demyelination. We investigated the protective effect of dexamethasone (DEX) on osmotic demyelination in rats. After rapid correction of chronic hyponatremia, rats displayed serious neurologic impairments and demyelinative lesions were observed in various brain regions. Conversely, DEX-treated rats exhibited minimal neurologic impairments and demyelinative lesions were rarely seen in the brain. A marked extravasation of endogenous immunoglobulin G and Evans blue dye were observed in the brains of rats that did not receive DEX, indicating disruption of the BBB, but this was not observed in DEX-treated rats. These results indicate that DEX is effective in preventing osmotic demyelination by inhibiting BBB disruption, and suggest that DEX might be useful for the prevention of CPM in clinical practice.

Protective effect of dexamethasone on osmotic-induced demyelination in rats.

Central pontine myelinolysis (CPM) is a serious demyelination disease commonly associated with the rapid correction of hyponatremia. Although its pathogenesis remains unclear, the disruption of the blood-brain barrier (BBB) as a consequence of a rapid increase in serum sodium concentration is considered to play a critical role. Since glucocorticoids are known to influence BBB permeability and prevent its disruption as a result of hypertension or hyperosmolarity, we investigated whether dexamethasone (DEX) could protect against osmotic demyelination in an animal model of CPM. Hyponatremia was induced in rats by liquid diet feeding and dDAVP infusion. Seven days later, the animals' hyponatremia was rapidly corrected by injecting a bolus of hypertonic saline intraperitoneally. Rats subjected to this treatment displayed serious neurological impairment and 77% died within 5 days of rapid correction of their hyponatremia; demyelinative lesions were observed in various brain regions in these animals. On the other hand, rats that were treated with DEX (2 mg/kg, 0 and 6 h after hypertonic saline injection) exhibited minimal neurological impairment and all were alive after 5 days. Demyelinative lesions were rarely seen in the brains of DEX-treated rats. A marked extravasation of endogenous IgG was observed in the demyelinative lesions in the brains of rats that did not receive DEX, indicating disruption of the BBB, but was not observed in DEX-treated rats. Furthermore, Evans blue injection revealed a significant reduction in staining in the brains of DEX-treated rats (P < 0.05). These results indicate that early DEX treatment can prevent the BBB disruption that is caused by the rapid correction of hyponatremia and its associative demyelinative changes, and suggest that DEX might be effective in preventing CPM.

Central pontine myelinolysis.

Central pontine myelinolysis (CPM) is a demyelinating disease of the pons often associated with demyelination of other areas of the central nervous system (CNS). The term 'osmotic demyelinization syndrome' is used for pontine and extrapontine myelinolysis. In this paper, we are concerned with CPM although the extrapontine one is based on the same pathogenesis. Both share the diagnostic methods, and their prevention and therapy are the same. The etiology and pathogenesis of this disorder are unclear and will be discussed. However, almost all cases of CPM are related to severe diseases. Chronic alcoholism is still the most common underlying condition of CPM patients. In the literature, 174 cases of CPM have been reported in alcoholics since 1986, which is equivalent to an incidence of 39.4%. Likewise, 95 cases of CPM following the correction of hyponatremia have been documented since 1986 (21.5%). The role of hyponatremia and its correction will be outlined in the discussion of the pathogenesis of CPM. The third largest group of CPM cases are liver transplant patients (17.4%), with the development of CPM being attributed to the immunosuppressive agent cyclosporine in particular. Depending on the involvement of other CNS structures, the clinical picture can vary considerably. The large-scale introduction of magnetic resonance imaging has increasingly facilitated the antemortem diagnosis of CPM, although the radiological findings lag behind and do not necessarily correlate with the clinical picture. As yet, there is no specific therapy of choice. A number of therapeutic approaches have been tested and although they have not been compared with regard to their rate of success, they have all led to a substantial improvement in the prognosis of CPM.

A review of the causes of central pontine myelinosis: yet another apoptotic illness?

One of the well recognized stimuli for central pontine myelinosis (CPM) is the rapid correction of chronic hyponatraemia. Conventionally this has been perceived to lead to pontine glial cell swelling through osmosis and eventually to cell death. However, although a purely osmotic argument has been central to any patho-physiological understanding of CPM, there are deficiencies in this approach that do not account for why certain individuals develop CPM with relatively mild osmotic insults. Here we review the varying aetiologies of CPM and propose a novel hypothesis for CPM causation by suggesting that individuals predisposed to CPM have inadequate energy provision as well as other factors that result in a pro-apoptotic drive, which renders them susceptible to brain injury from diverse causes. In CPM, the precipitant of brain injury appears to be osmotic stress. Furthermore, this model suggests a number of therapeutic interventions that may prevent or at least mitigate the consequences of CPM.

Azotemia (48 h) decreases the risk of brain damage in rats after correction of chronic hyponatremia.

Brain myelinolysis complicates excessive correction of chronic hyponatremia in man. Myelinolysis appear in rats for correction levels deltaSNa) > 20 mEq/l/24 h. We previously showed in rats that when chronic hyponatremia was corrected with urea, the incidence and the severity of brain lesions were significantly reduced compared to hypertonic saline. In man, hyponatremia is frequently associated with azotemia and hemo-dialysis usually corrects rapidly the serum sodium (SNa) but only few patients apparently develop demyelination. We hypothesize that uremic state protects brain against myelinolysis. This hypothesis was evaluated in rats developing azotemia by administration of mercuric chloride (HgCl2, 1.5 mg/kg). Severe (SNa < 120 mEq/l) hyponatremia (3 days) was induced by S.C. AVP and i.p. 2.5% D-glucose for 3 days. HgCl2 was injected on day 2. Hyponatremia was corrected on day 4 by i.p. injections of 5% NaCl in order to obtain a correction level largely above the toxic threshold for brain (deltaSNA approximately 30 mEq/l/24 h). Surviving rats were decapitated on day 10 for brain analysis. In the group with renal failure (Group I, n = 15, urea 59 mmol/l) the outcome was remarkably favourable with only three rats (3/15) dying before day 10 and only one of them (1/3) presenting myelinolysis-related neurologic symptoms. The 12 other rats (80%) survived in Group I without symptoms and brain analysis was normal in all of them despite large correction level (deltaSNa: 32 mEq/l/24 h). On the contrary in nine rats in which HgCl, did not produce significant azotemia (control 1, n = 9, urea: 11 mmol/l), all the rats developed severe neurologic symptoms and eight of them died before day 10. Similar catastrophic outcome was observed in the non-azotemic controls (control 2, no HgCl2 administration, n = 15, urea: 5 mmol/l). All of them developed myelinolysis-related neurologic symptoms and only four of them survived with severe brain lesions (survival 12/15 in Group I vs. 5/24 in pooled controls 1 and 2, p < 0.001). In conclusion, we showed for the first time that chronic hyponatremic rats with azotemia (48 h) tolerated large increases in SNa (approximately 30 mEq/l/24 h) without significant brain damage.

Therapeutic relowering of the serum sodium in a patient after excessive correction of hyponatremia.

BACKGROUND: Inappropriate correction of chronic hyponatremia could lead to major neuropathological sequelae. In man, the risk of brain myelinolysis increases strikingly when correction of the serum sodium exceeds 10-15 mEq/l/24 h. No treatment is actually available for this iatrogenic brain injury. However, recent experimental data showed that rapid reinduction of the hyponatremia greatly reduces the incidence of brain damage and death in case of serum sodium overshooting. SUBJECTS AND METHODS: We tested this rescue manoeuver in a 71-year-old woman with nausea, confusion and severe (SNa 106 mEq/l) chronic hyponatremia related to thiazides. It was associated with hypokalemia (SK: 3.2 mEq/l). RESULTS: Treatment with isotonic saline produced inappropriately high SNa correction level of +21 mEq/l after the first 24 h. After initial improvement, the neurological status deteriorated after 72 h. Rapid reinduction of the hyponatremia was then ordered. Administration of hypotonic fluids (by oral and i.v. route) combined with dDAVP induced a prompt decline in the SNa (-16 mEq/l/14 h) with a final gradient of correction of deltaSNa +9 mEq/l. This manoeuver was well tolerated without untoward effects. The natremia then progressively normalized and the patient completely recovered without neurological sequelae. CONCLUSION: Hypotonic fluids may be safely administered to decrease the natremia after excessive correction of hyponatremia for potential prevention of myelinolysis.

Mielinolisis póntica central con síndrome de enclaustramiento

Tha case of a 55 year old man who presented with severe global headache 8 hours after having been drinking heavily, and who over a two hour period developed deep coma and flaccid paralysis of all four extremities is reported. A CT scan of the brain was normal; however, on Magnetic Resonance Imaging (MRI) extensive hyperintense areas in the brain stem, mainly in the pons, were easily identified. Based upon the clinical and MRI findings a diagnosis of Central Pontine Myelinolysis was made. Following several months of supportive therapy the patient partially recovered and was able to leave the hospital.