The syndrome of inappropriate secretion of antidiuretic hormone (SIADH)--treatment with lithium

Lithium for Carbamazepine-Induced Syndrome of Inappropriate Antidiuretic Hormone

OBJECTIVES

To examine the effectiveness of low-dose lithium carbonate for managing carbamazepine-induced hyponatremia.

METHODS

Single case study in an 88 year old man with bipolar illness and vascular dementia who had failed to respond to other mood stabilizers.

RESULTS

The patient had developed hyponatremia on two separate occasions when treated with carbamazepine. Introduction of low-dose lithium resulted in prompt normalization of serum sodium levels, which was maintained for the subsequent 8 weeks.

CONCLUSIONS

Carbamazepine may sometimes be the best or only viable treatment option for patients with bipolar illness or other conditions. When its use is complicated by syndrome of inappropriate ADH, dose reduction and fluid restriction are the simplest options but, if ineffective, addition of lithium may be a feasible, albeit somewhat complicated, alternative.

Syndrome of Inappropriate Antidiuretic Hormone Secretion in a Mini-Breed Puppy Associated With Aspiration Pneumonia

A 3-month-old intact male Prague ratter was presented to the emergency service for evaluation of progressive lethargy, weakness, coughing and labour breathing after an episode of resistance to oral deworming. The patient exhibited depression, increased respiratory effort and cyanosis at initial presentation. Results of first diagnostic work-up (complete blood cell count, biochemistry panel and thoracic x-rays) were all consistent with aspiration pneumonia. The puppy was initially treated with balanced isotonic crystalloids, broad spectrum antibiotics, nebulization with thoracic coupage and was transferred to an infant incubator with a sustained FiO2 of 40-50%. Twenty-four hours after ICU admission the patient's condition suffered a worsening and the dog was orthopneic, severely depressed with episodes of intermittent dysphoria and seizuring. New thoracic radiographs and several samples of blood and urine were collected to go further in the diagnostic workup revealing severe hyponatremia, severe plasma hypotonicity, high natriuresis and metabolic acidosis with a worsening of the radiological pulmonary pattern. Based on these new clinical findings a diagnosis of SIADH was established. Emergency treatment with hypertonic 3% saline solution and loop diuretics was started like a sodium supplement and to inhibit water resorption in renal tubules, thus reducing the volume overload. The goal of this treatment was to achieve a progressive and controlled increase of plasma sodium concentration and promoting the excretion of positive body water imbalance. The patient's condition improved clinically over the following days, treatment was progressively discontinued and the dog was discharged 7 days after admission. To the author's knowledge this is the first report of a puppy younger than 12 weeks with respiratory distress developing SIADH associated to aspiration pneumonia.

Disturbances of sodium in critically ill adult neurologic patients: a clinical review

Disorders of sodium and water balance are common in critically ill adult neurologic patients. Normal aspects of sodium and water regulation are reviewed. The etiology of possible causes of sodium disturbance is discussed in both the general inpatient and the neurologic populations. Areas of importance are highlighted with regard to the differential diagnosis of sodium disturbance in neurologic patients, and management strategies are discussed. Specific discussions of the etiology, diagnosis, and management of cerebral salt wasting syndrome, the syndrome of inappropriate antidiuretic hormone secretion, and central diabetes insipidus are presented, as well as the problems of overtreatment. The importance of diagnosis at an early stage of these diseases is stressed, with a recommendation for conservative management of milder cases.

Vasopressin Antagonism

Hyponatremia is a common electrolyte disorder frequently associated with central nervous system (CNS) diseases, neurosurgical procedures, and the use of neurotropic drugs. The clinical manifestations of hyponatremia are attributable to an increase in brain water content that occurs in response to a decrease in serum osmolality. Hyponatremia triggers adaptive processes in the brain to limit this cerebral swelling, but a rapid fall in serum [Na(+)] may overwhelm this adaptive mechanism. Patients with hyponatremia for more than 48 hours are at risk for developing osmotic demyelination when overly rapid correction of hyponatremia restores serum osmolality before this adaptive process can be reversed. The infusion of hypertonic saline for the restoration of serum [Na(+)] should therefore be carefully controlled to avoid this potentially devastating complication. Other options currently available for the treatment of hyponatremia, including strict restriction of fluid intake, are limited by their inconsistent response, poor tolerability, and frequent adverse effects. Arginine vasopressin (AVP)-receptor antagonists promote aquaresis (electrolyte-sparing excretion of free water) by blocking the antidiuretic action of the hormone at the level of the collecting ducts. In clinical trials, AVP-receptor antagonists increased serum [Na] in patients with euvolemic or hypervolemic hyponatremia associated with various conditions, including syndrome of inappropriate antidiuretic hormone secretion (SIADH). Patients who have neurologic disease with SIADH-related hyponatremia may be good candidates for treatment with AVP-receptor antagonists. Careful assessment of intravascular volume status before initiation of therapy and strict monitoring of the serum [Na] during treatment are necessary to avoid complications.

Hyponatraemia and the syndrome of inappropriate antidiuretic hormone secretion (SIADH) induced by psychotropic drugs

The use of psychotropic drugs has been associated with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) in a number of case reports. SIADH is characterised by the sustained release of antidiuretic hormone (ADH) from the posterior pituitary. The patients have a reduced ability to excrete diluted urine, ingested fluid is retained, and the extracellular fluid expands and becomes hypo-osmolar. The cardinal signs are hyponatraemia, serum hypoosmolality and a less than maximally diluted urine. Common symptoms include weakness, lethargy, headache, anorexia and weight gain. These symptoms may be followed by confusion, convulsions, coma and death. The early symptoms are vague and nonspecific, and they may even mimic the symptoms of the psychiatric disorder itself. For antidepressants, the risk of SIADH seems to be highest during the first weeks of treatment. For antipsychotics, the risk seems to be more spread out in time. The causative role of the drug may sometimes be difficult to estimate, as even drug-free psychiatric patients, mostly those with schizophrenia, develop SIADH on the basis of psychogenic polydipsia. Smoking is another factor associated with the development of SIADH, and the risk may also increase with age. The acute treatment of SIADH induced by a psychotropic drug includes discontinuation of the drug as well as restriction of fluid intake. In cases with significant clinical symptoms, infusion of sodium chloride is recommended. After the acute management, it is useful to evaluate the causative role of the drug by performing a water loading test and/or drug rechallenge. If continued treatment with an antidepressant or antipsychotic is indicated, a drug with a different pharmacological profile should be chosen, and the serum sodium levels should be monitored closely. If treatment with the drug that caused SIADH must be continued, concomitant treatment with demeclocycline may reduce the tendency of hyponatraemia.

Early inappropriate secretion of antidiuretic hormone after trans-sphenoidal pituitary adenomectomy

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a rare but life-threatening complication of trans-sphenoidal pituitary adenomectomy. It has previously only been described as a late phenomenon. We report an early presentation within the first week. The pathophysiology, clinical features and treatment are discussed.

The syndrome of inappropriate secretion of antidiuretic hormone in the maxillofacial trauma patient

The maxillofacial trauma patient whose neurologic status undergoes a rapid and serious deterioration may have a severe hyponatremia secondary to the inappropriate secretion of antidiuretic hormone (SIADH). Other causes of hyponatremia must be ruled out, especially posttraumatic cerebral salt wasting, which necessitates a different mode of therapy. A case of SIADH is reported, and the work-up and differential diagnosis of posttraumatic hyponatremia are discussed.