Antidiuretic hormone excess

Fluid therapy for children: facts, fashions and questions

Fluid therapy restores circulation by expanding extracellular fluid. However, a dispute has arisen regarding the nature of intravenous therapy for acutely ill children following the development of acute hyponatraemia from overuse of hypotonic saline. The foundation on which correct maintenance fluid therapy is built is examined and the difference between maintenance fluid therapy and restoration or replenishment fluid therapy for reduction in extracellular fluid volume is delineated. Changing practices and the basic physiology of extracellular fluid are discussed. Some propose changing the definition of "maintenance therapy" and recommend isotonic saline be used as maintenance and restoration therapy in undefined amounts leading to excess intravenous sodium chloride intake. Intravenous fluid therapy for children with volume depletion should first restore extracellular volume with measured infusions of isotonic saline followed by defined, appropriate maintenance therapy to replace physiological losses according to principles established 50 years ago.

[Hydration and meningitis]

For almost 20 years, fluid restriction has been applied in the management of bacterial meningitis. This recommendation was based upon the findings of elevated plasma levels of arginine vasopressin in children with bacterial meningitis and their interpretation as evidence for inappropriate secretion of antidiuretic hormone. Recent data indicate that this interpretation was erroneous and that elevated levels of arginine vasopressin is the consequence of hypovolemia in the majority of cases of bacterial meningitis. In addition, fluid restriction appears to worsen the prognosis. As a consequence, not only fluid restriction must not be systematically applied in the management of bacterial meningitis, but appropriate fluid and sodium intakes are necessary to compensate hypovolemia and dehydration. Only a small number of cases with evidence of inappropriate secretion of antidiuretic hormone will require fluid restriction.

Syndrome of inappropriate secretion of antidiuretic hormone (SIADH) in malignant disease

The first clinical case of a patient with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) was presented by Schwartz et al. in 1957 (Am J Med 1957; 23: 529-42), describing two patients with lung cancer who developed hyponatraemia associated with continued urinary sodium loss. They postulated that the tumours led to the inappropriate release of antidiuretic hormone (ADH), later discovered to consist of arginine-vasopressin (AVP). This suggestion was later confirmed in several studies. The clinical description of the syndrome has changed little since the original observation, and the cardinal findings of SIADH are as follows: (i) hyponatraemia with corresponding hypo-osmolality of the serum and extracellular fluid, (ii) continued renal excretion of sodium. (iii) absence of clinical evidence of fluid volume depletion, (iv) osmolality of the urine greater than that appropriate for the concomitant osmolality of the plasma, i.e. urine less than maximal diluted, and (v) normal function of kidneys, suprarenal glands and thyroid glands. Measurement of AVP in plasma is not a part of the definition of SIADH. SIADH may be caused by a variety of malignant tumours, but may also be caused by various other conditions, such as disorders involving the central nervous system, intrathoratic disorders such as infections, positive pressure ventilation and conditions with decrease in left atrial pressure. Also, a large number of pharmaceutical agents have been shown to produce SIADH, including a number of cytotoxic drugs such as vincristine, vinblastine, cisplatin, cyclophosphamide, and melphalan. A broad spectrum of malignant tumours has been reported to cause SIADH; however, most of these observations have been in case reports including very few patients. This includes a number of primary brain tumours, haematologic malignancies, intrathoracic non-pulmonary cancers, skin tumours, gastrointestinal cancers, gynaecological cancer, breast-and prostatic cancer, and sarcomas. Larger series of patients have revealed that SIADH occurs in 3% of patients with head and neck cancer (47 cases out of 1696 patients), in 0.7% of patients with non-small-cell lung cancer (three cases out of 427 patients), and in 15% of cases of small-cell lung cancer (214 cases out of 1473 patients). The optimal therapy for SIADH is to treat the underlying malignant disease. If this is not possible, or if the disease has become refractory, other treatment methods are available such as water restriction, demeclocycline therapy, or, in severe cases, infusion of hypertonic saline together with furosemide during careful monitoring.

Hyponatraemia in acute brain disease

Hyponatraemia (HN) can result from a wide range of mechanisms, and therapy must be individualized. Two theories of the origin of HN in acute brain disease have prevailed. The first is the cerebral salt wasting syndrome (CSWS), where excessive natriuresis caused by some unknown cerebral natriuretic factor lowers the total sodium pool of the body and hence the plasma concentration. The second theory is the syndrome of inappropriate secretion of antidiuretic hormone (SIADH), where an increase in total body water is caused by unphysiological secretion of ADH, lowering the concentration of sodium in the plasma. A third possibility is 'sodium shift', i.e. a displacement of sodium from the extracellular to the intracellular space with a simultaneous movement of potassium in the opposite direction. The morbidity and mortality associated with HN only arise in cases where the rate of development of HN was 0.5 mmol h-1 or more. Symptoms respond promptly when the HN is quickly corrected with furosemide and 3% sodium chloride.

Suspected inappropriate secretion of antidiuretic hormone in a male with mental retardation

The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is a disorder in which a sustained release of antidiuretic hormone occurs because of certain diseases, pharmacological agents, or trauma. Fluid volume expands with a resultant hyponatremia which, depending on the degree, may be asymptomatic or result in death. This case report describes a 38-year-old male in whom SIADH was strongly suspected secondary to Tegretol therapy to control a seizure disorder. Medical consultation is imperative for these patients before administering a fluid challenge during general anesthesia.

Excessive secretion of antidiuretic hormone in infections with respiratory syncytial virus

The association between infections with respiratory syncytial virus and plasma concentrations of antidiuretic hormone was assessed in 48 patients who had been admitted to hospital. The mean (SEM) concentration of antidiuretic hormone was significantly raised in patients with bronchiolitis (9.3 (1.4) ng/l) compared with non-pulmonary respiratory syncytial virus infections that cause apnoea or upper respiratory tract symptoms (6.1 (1.7) ng/l). The highest concentrations of antidiuretic hormone were seen in patients receiving mechanical ventilation (18.0 (6.7) ng/l). There were no differences in mean serum sodium concentrations among the subgroups. Hypertranslucency on chest radiograph or an arterial carbon dioxide tension above 6.67 kPa were associated with a significantly higher concentration of antidiuretic hormone. Increased or normal maintenance fluid intake in children with pulmonary respiratory syncytial virus infections may cause the same symptoms of fluid overload as the syndrome of inappropriate secretion of antidiuretic hormone. Patients with pulmonary respiratory syncytial virus infection, hypertranslucency in chest radiograph, hypercapnia, or mechanical ventilation are at risk for raised concentrations of antidiuretic hormone. Restricted fluid intake and careful monitoring of fluid balance and plasma electrolyte concentrations are therefore necessary in these patients.

Effect of a modified fluid therapy on renal function during indomethacin therapy for persistent ductus arteriosus

A rehydration with 7 ml/kg/h for six hours prior to indomethacin administration prevented the adverse effects of this drug on renal function in prematures with persistent ductus arteriosus. During the 36 hour observation period after indomethacin administration, no significant changes in serum creatinine, sodium, and potassium concentrations, or urinary flow, creatinine clearance, or filtered sodium could be detected. The only significant finding was a reduction in fractional sodium excretion. One can assume that this beneficial effect of the fluid load is due to a suppression of some parts of the vasoconstrictor mechanisms, which are responsible for the deterioration of renal function in newborns during indomethacin therapy. Using this modified fluid regimen, no cardiovascular side effects were noticed, a closure of the duct was achieved in 7 of 10 treatment courses.

Initial fluid therapy for children with meningitis with consideration of the syndrome of inappropriate anti-diuretic hormone

A review of 85 children with meningitis admitted to the University Children's Hospital at Hermann Hospital revealed that only six patients (7%) had sufficient clinical and laboratory evidence to be compatible with the diagnosis of inappropriate secretion of antidiuretic hormone (SIADH). This is in contrast with various communications in the pediatric literature that have reported an association between the two conditions of as high as 85%. Hyponatremia (serum sodium 135 mEq/L) was observed in 27 (32%), but neither the initial laboratory data nor the subsequent follow-up data supported the diagnosis of SIADH. Moderate to severe dehydration was documented in 16 patients (19%) and suspected in more than 50% of the cases (serial weight determinations indicating an increase in weight from admission to discharge). Although the incidence of neurologic sequelae in this series was not influenced significantly by the presence or absence of hyponatremia, SIADH, or fluid restriction, the numbers are still small. Based on these data, routine fluid restriction cannot be recommended unless there is confirmatory evidence of SIADH.

Pertussis complicated by the syndrome of inappropriate antidiuretic hormone secretion. Pathophysiology and management

Two cases of pertussis complicated by the syndrome of inappropriate antidiuretic hormone secretion (SIADH) are reported. Both patients experienced seizures associated with hyponatremia. Patients with severe pertussis are at risk for SIADH and should be monitored closely for its development.

Infantile seizures caused by voluntary water intoxication

A case of infantile seizures of unusual etiology and presentation is described. Water intoxication with resultant epilepticus was caused by ingestion of nearly 150 ml/kg of fresh water on the day of presentation. It is unclear why the infant voluntarily consumed so much water, but heat illness is the most probable cause.

Syndrome of inappropriate antidiuretic hormone secretion. A complication of high-dose intravenous melphalan

Melphalan is now being investigated as an intravenous (IV) bolus chemotherapeutic agent in children with resistant tumors involving the bone marrow. Two patients received 2 mg/kg melphalan, IV bolus; 10 patients received 1 mg/kg. Seven of the ten patients receiving 1 mg/kg had noticeable downward trends in the serum sodium concentrations, whereas both patients receiving 2 mg/kg developed hyponatremia (serum sodium concentration [SNa], mEq/l = 124-125) and inappropriate urinary sodium losses. Syndrome of inappropriate antidiuretic hormone (SiADH) is a previously unreported complication of high dose bolus melphalan therapy.

The antidiuretic hormone response to therapy for acute asthma

The plasma antidiuretic hormone concentrations in eight asthmatic children were measured at the onset of an acute severe attack and were repeated 24 h later. Conventional therapy and maintenance fluid intake resulted in a significant fall in antidiuretic hormone concentrations without abnormal changes in other biochemical indicators of dehydration.

Hyponatremia and natriuresis following subarachnoid hemorrhage in a monkey model

A monkey model of subarachnoid hemorrhage (SAH) was used to study both the incidence of hyponatremia and natriuresis and the associated changes in antidiuretic hormone (ADH) secretion and salt and water balance. Following SAH, seven of nine monkeys became natriuretic and hyponatremic. The natriuretic period lasted an average of 4.4 +/- 0.4 days. The mean nadir of serum sodium content was 125.7 +/- 1.6 mEq/liter, and occurred on the average on the 5th day following SAH. The sodium balance after SAH was negative as compared to the preoperative positive sodium balance (p less than 0.001). The plasma vasopressin level was usually elevated for a day following surgery, but there was no significant difference in the levels during the preoperative period and during the period of natriuresis following SAH. The daily urine output and aldosterone levels were not significantly different, and the plasma volume was slightly, but not significantly, decreased after SAH. Four of the animals that had a hyponatremic and natriuretic response following SAH showed a normal regulation of vasopressin in response to both a water challenge and hypertonic saline challenge. The three monkeys that underwent sham procedures did not become hyponatremic and natriuretic postoperatively. The sham-operated monkeys did not show significant differences in their plasma vasopressin levels, urine volume, plasma volume, and aldosterone levels following surgery. These observations are more consistent with primary natriuresis as the cause of hyponatremia rather than the syndrome of inappropriate secretion of ADH. The cause of the renal loss of sodium is not known, but the possibility of a brain natriuretic factor or an alteration in the neural control of the kidney should be considered.

Effect of prolonged indomethacin therapy on renal function and selected vasoactive hormones in very-low-birth-weight infants with symptomatic patent ductus arteriosus

Renal function and changes in the activity of selected vasoactive hormones during prolonged indomethacin therapy (1 week) were studied in 11 very-low-birth-weight infants with symptomatic patent ductus arteriosus. The initiation of indomethacin therapy was associated with a reduction in diuresis, a transient decrease in creatinine clearance, and an increase in body weight (P less than 0.01). Furthermore, there was a transient trend toward hyponatremia and hyperkalemia. This acute renal dysfunction was compatible with a complex picture of renal hypoperfusion associated with a fall of plasma renin activity from high levels prior to indomethacin treatment, with a transient rise in the plasma level of arginine vasopressin and with suppressed renal and systemic prostaglandin synthesis. During treatment, an effective circulatory volume was restored by closing the ductus. In parallel, PRA and AVP plasma concentrations returned to nearly normal values. Subsequently, kidney function was not further impaired despite continued indomethacin therapy. These observations suggest that prolonged indomethacin therapy for prevention of sPDA relapse probably constitutes no further risk to kidney function after successful pharmacologically induced ductal constriction.

Acute asthma and antidiuretic hormone secretion

Plasma antidiuretic hormone concentrations were measured in a group of children with acute asthma and in a control group. Very high levels of antidiuretic hormone were found in the asthmatic group. There were no changes in other biochemical indices. If overproduction of antidiuretic hormone is sustained then fluid administration to children with severe acute asthma is potentially dangerous.

Hyponatremia in intracranial disease: perhaps not the syndrome of inappropriate secretion of antidiuretic hormone (SIADH)

Patients with intracranial disorders are prone to develop hyponatremia with inability to prevent the loss of sodium in their urine. This was originally referred to as "cerebral salt wasting," but more recently is thought to be secondary to the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Blood volume determinations were made in 12 unselected neurosurgical patients with intracranial disease who fulfilled the laboratory criteria for SIADH. Ten of the 12 patients had significant decreases in their red blood cell mass, plasma volume, and total blood volume. The finding of a decreased blood volume in patients who fulfill the laboratory criteria for SIADH is better explained by the original concepts of cerebral salt wasting than by SIADH. The primary defect may be the inability of the kidney to conserve sodium.

Inappropriate secretion of antidiuretic hormone in infants with respiratory infections

Four infants in whom excessive secretion of antidiuretic hormone was associated with pulmonary infections are reported. Severe hyponatraemia was noted in 3 of them; in the fourth, fluid restriction may have prevented this complication.

Elevations in plasma ADH levels during PEEP ventilation in the dog: mechanisms involved

In an attempt to define more precisely the various mechanisms involved in antidiuretic hormone (ADH) release during positive end-expiratory pressure ventilation (PEEP), experiments were performed on seven groups of dogs. PEEP-10 and PEEP-15 cmH2O caused significant elevations of plasma ADH from basal values of 24.9 +/- 5.2 pg/ml (mean +/- SE) to 64.6 +/- 14.2 and 106.0 +/- 20.6, respectively (P < 0.02, P < 0.005). The ADH levels returned to basal values after cessation of PEEP. This rise in ADH levels was prevented by an infusion of dextran prior to PEEP. The fall in blood pressure and cardiac output that occurred during PEEP was also prevented by the dextran infusion. Changes in ADH levels were unrelated to lung volume, left transmural pressure, and serum osmolality. Bilateral vagotomy and carotid sinus denervation was followed by an attenuated rise in ADH levels in terms of the percent rise above base line, but it did not significantly alter the absolute rise in ADH during PEEP. ADH levels were, however, reduced significantly by decreasing intracranial pressure by the removal of cerebrospinal fluid during PEEP. Propranolol administration prior to PEEP completely blocked plasma renin activity. Although the peak ADH levels were unaffected by propranolol, the rise was delayed. The results obtained indicate that a number of physiological factors may affect plasma ADH levels during PEEP. These include the carotid body and aortic arch baroreceptors as wells as sensors of intracranial pressure.

Common fluid and electrolyte problems in the pediatric intensive care unit

Administration of intravenous fluid to infants and children requires an understanding of the normal expenditure of water and electrolytes by the healthy child and the effects of specific illnesses on water and electrolyte turnover.

Fluid management in Haemophilus influenzae meningitis

The fluid management of 50 children with Haemohpilus influenzae type B meningitis was reviewed. Clinical hydration status on admission, serum sodium values, and overall fluid balance was assessed to determine the contribution of empiric fluid restriction in preventing the development of syndrome of inappropriate antidiuretic hormone (SIADH). Thirty-three of 50 patients were well hydrated on admission. Sixteen of 50 patients (32%) initially had signs of dehydration and five out of 16 were in shock. Only two patients had evidence of SIADH. Twenty patients were empirically fluid restricted, including one who proceeded to develop SIADH; thirteen were not fluid restricted, and sixteen who were dehydrated received replacement fluids in addition to the usual maintenance fluids. None of these patients developed SIADH. As fluid depletion was more common than excessive fluid retention in our patients, empiric fluid restrictions could not be justified. Careful, individualized monitoring of the clinical state of hydration, electrolytes and osmolaities is suggested to guide the fluid management in these patients.