04 Electrolyte Abnormalities In Specific Surgical Patients

Question 1

Which conditions are associated with Syndrome of Inappropriate Secretion of Antidiuretic Hormone (SIADH)?

Answer 1

• Head injury or CNS Surgery
• Morphine, nonsteroidals, oxytocin
• Hypothyroidism, glucocorticoid deficiency
• Small cell cancer of the lung, pancreatic CA, Thymoma, Hodgkin’s

Question 2

SIADH should be considered in which patients?

Answer 2

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.

Question 3

Treatment of SIADH?

Answer 3

Restrict free water
Furosemide
Add isotonic or hypertonic fluids if persistent
Demeclocycline and lithium (chronic SIADH)

Question 4

What is diabetes insipidus (DI)?

Answer 4

A disorder of ADH stimulation, manifested by dilute urine in the case of hypernatremia.

Question 5

DI is caused by?

Answer 5

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)

Question 6

How is DI diagnosed?

Answer 6

A paradoxical increase in urine osmolality in response to a period of water deprivation.

Question 7

Treatment of DI?

Answer 7

Mild: Free water replacement

Severe: Vasopressin 5U SQ q6-8h (monitor electrolytes)

Question 8

What is cerebral salt wasting, and how is it diagnosed?

Answer 8

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.

Question 9

What is refeeding syndrome?

Answer 9

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.

Question 10

Pathophysiology of refeeding syndrome?

Answer 10

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.

Question 11

Symptoms of refeeding syndrome?

Answer 11

Cardiac arrhythmias
Confusion
Respiratory failure
Death

Question 12

Measures to prevent refeeding syndrome?

Answer 12

• Correct underlying electrolyte abnormalities
• Administer thiamine prior to initiating feeding
• Gradual caloric repletion
• Close monitoring

Question 13

Cause of hyponatremia in acute renal failure patients?

Answer 13

• Breakdown of proteins, carbs and fats

- Free water administration

Question 14

Other electrolyte abnormalities associated with acute renal failure?

Answer 14

Hypocalcemia, hypermagnesemia, Hyperphosphatemia

Question 15

Causes of hyponatremia in cancer patients?

Answer 15

Hypovolemic:
Renal loss of sodium from diuretics
Salt-wasting nephropathy from cisplatin/chemo agents
Cerebral salt-wasting

Normovolemic:
SIADH

Question 16

Causes of hypernatremia in CA patients?

Answer 16

Poor oral intake or GI volume losses

Central DI

Question 17

Causes of hypokalemia in CA patients?

Answer 17

GI losses from radiation enteritis or chemotherapy

Question 18

Causes of hyperkalemia in CA patients?

Answer 18

Tumor lysis syndrome

Question 19

Causes of hypocalcemia in CA patients?

Answer 19

Removal of parathyroid tumor
Hungry bone syndrome (Calcium rapidly take up by bones)
Increased osteoblastic activity
Hyperphosphatemia

Question 20

Causes of hypomagnesemia in CA patients?

Answer 20

Ifosfamide and Cisplatin therapy

Question 21

Causes of hypophosphatemia in CA patients?

Answer 21

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)

Question 22

Causes of Hyperphosphatemia in CA patients?

Answer 22

Tumor lysis syndrome

Bisphosphonates in treating hypercalcemia

Question 23

Most common cause of hypercalcemia in hospitalized patients?

Answer 23

Malignancy (increased bone resorption, or decreased renal excretion)

Question 24

Treatment of hypercalcemia in malignancy?

Answer 24

1. Saline volume expansion, which will decrease renal reabsorption of calcium as the associated volume deficit is corrected.
2. Loop diuretic, once with adequate volume.

Question 25

Tumor lysis syndrome results when?

Answer 25

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)

Question 26

Treatment of tumor lysis syndrome?

Answer 26

Volume expansion
Correct underlying electrolyte abnormalities
Do NOT treat hypercalcemia unless symptomatic, to avoid metastatic calcifications
Dialysis