Which conditions are associated with Syndrome of Inappropriate Secretion of Antidiuretic Hormone (SIADH)?
- Head injury or CNS Surgery
- Morphine, nonsteroidals, oxytocin
- Hypothyroidism, glucocorticoid deficiency
- Small cell cancer of the lung, pancreatic CA, Thymoma, Hodgkin’s
SIADH should be considered in which patients?
Euvolemic, hyponatremic patients with elevated urine sodium levels and urine osmolality.
ADH secretion is inappropriate when it is not in response to osmotic or volume-related conditions.
Treatment of SIADH?
Restrict free water
Furosemide
Add isotonic or hypertonic fluids if persistent
Demeclocycline and lithium (chronic SIADH)
What is diabetes insipidus (DI)?
A disorder of ADH stimulation, manifested by dilute urine in the case of hypernatremia.
DI is caused by?
Central DI results from a defect in ADH secretion. (Pituitary surgery, closed head injury, anoxic encephalopathy)
Nephrogenic DI results from a defect in end-organ responsiveness to ADH. (Hypokalemia, radiocontrast dye, aminoglycosides, amphotericin B)
How is DI diagnosed?
A paradoxical increase in urine osmolality in response to a period of water deprivation.
Treatment of DI?
Mild: Free water replacement
Severe: Vasopressin 5U SQ q6-8h (monitor electrolytes)
What is cerebral salt wasting, and how is it diagnosed?
A diagnosis of exclusion, occurring in patients with a cerebral lesion and renal wasting of sodium and chloride with no other identifiable cause.
Natriuresis in a patient with a contracted extracellular volume should prompt the possible diagnosis of cerebral salt wasting.
Hyponatremia is frequently observed but is nonspecific; and occurs secondarily, which differentiates it from SIADH.
What is refeeding syndrome?
A potentially lethal condition that can occur with rapid and excessive feeding of patients with severe underlying malnutrition due to starvation, alcoholism, delayed nutritional support, anorexia nervosa, or massive weight loss.
Pathophysiology of refeeding syndrome?
Upon refeeding, a shift in metabolism from fat or carbohydrate substrate stimulates insulin release, which results in the cellular uptake of electrolytes (phosphate, magnesium, calcium, potassium). However, severe hyperglycemia may result from blunted basal insulin secretion.
Symptoms of refeeding syndrome?
Cardiac arrhythmias
Confusion
Respiratory failure
Death
Measures to prevent refeeding syndrome?
- Correct underlying electrolyte abnormalities
- Administer thiamine prior to initiating feeding
- Gradual caloric repletion
- Close monitoring
Cause of hyponatremia in acute renal failure patients?
- Breakdown of proteins, carbs and fats
- Free water administration
Other electrolyte abnormalities associated with acute renal failure?
Hypocalcemia, hypermagnesemia, Hyperphosphatemia
Causes of hyponatremia in cancer patients?
Hypovolemic:
Renal loss of sodium from diuretics
Salt-wasting nephropathy from cisplatin/chemo agents
Cerebral salt-wasting
Normovolemic:
SIADH
Causes of hypernatremia in CA patients?
Poor oral intake or GI volume losses
Central DI
Causes of hypokalemia in CA patients?
GI losses from radiation enteritis or chemotherapy
Causes of hyperkalemia in CA patients?
Tumor lysis syndrome
Causes of hypocalcemia in CA patients?
Removal of parathyroid tumor
Hungry bone syndrome (Calcium rapidly take up by bones)
Increased osteoblastic activity
Hyperphosphatemia
Causes of hypomagnesemia in CA patients?
Ifosfamide and Cisplatin therapy
Causes of hypophosphatemia in CA patients?
Hyperparathyroidism (Decreased phosphorus reabsorption) Oncogenic osteomalacia (increases urinary excretion of phosphorus) Renal tubular dysfunction (i.e. Multiple myeloma, chemotherapy agents) Acute leukemia (rapidly proliferating cells take up phosphorus)
Causes of Hyperphosphatemia in CA patients?
Tumor lysis syndrome
Bisphosphonates in treating hypercalcemia
Most common cause of hypercalcemia in hospitalized patients?
Malignancy (increased bone resorption, or decreased renal excretion)
Treatment of hypercalcemia in malignancy?
- Saline volume expansion, which will decrease renal reabsorption of calcium as the associated volume deficit is corrected.
- Loop diuretic, once with adequate volume.
Tumor lysis syndrome results when?
The release of intracellular metabolites overwhelms the kidneys’ excretory capacity. The rapid release of uric acid, potassium, and phosphorus can result in marked hyperuricemia, hyperkalemia, Hyperphosphatemia, hypocalcemia, and acute renal failure.
(Poorly differentiated lymphomas, leukemias, solid tumor malignancies, during RT and chemotherapy)
Treatment of tumor lysis syndrome?
Volume expansion
Correct underlying electrolyte abnormalities
Do NOT treat hypercalcemia unless symptomatic, to avoid metastatic calcifications
Dialysis
