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Chapter 3: Fluid and Electrolyte Management of the Surgical Patient

Metabolic acidosis with a normal anion gap (AG) occurs with

A. Diabetic acidosis

B. Renal failure

C. Severe diarrhea

D. Starvation

Answer: C

Metabolic acidosis with a normal anion gap (AG) results from either acid administration (HCl or NH4+) or a loss of bicarbonate from gastrointestinal (GI) losses, such as diarrhea, fistulas (enteric, pancreatic, or biliary), ureterosigmoidostomy, or from renal loss. The bicarbonate loss is accompanied by a gain of chloride, thus the AG remains unchanged. (See Schwartz 10th ed., p. 74.)

All are possible causes of postoperative hyponatremia EXCEPT

A. Excess infusion of normal saline intraoperatively.

B. Administration of antipsychotic medication.

C. Transient decrease in antidiuretic hormone (ADH) secretion.

D. Excess oral water intake.

Answer: C

Hyponatremia is caused by excess free water (dilution) or decreased sodium (depletion). Thus, excessive intake of free water (oral or IV) can lead to hyponatremia. Also, medications can cause water retention and subsequent hyponatremia, especially in older patients. Primary renal disease, diuretic use, and secretion of antidiuretic hormone (ADH) are common causes of sodium depletion. ADH can be released transiently postoperatively, or less frequently, in syndrome of inappropriate ADH secretion. Lastly, pseudohyponatremia can be seen on laboratory testing when high serum glucose, lipid, or protein levels compromise sodium measurements. (See Schwartz 10th ed., p. 69.)

Which of the following is an early sign of hyperkalemia?

A. Peaked T waves

B. Peaked P waves

C. Peaked (shortened) QRS complex

D. Peaked U waves

Answer: A

Symptoms of hyperkalemia are primarily GI, neuromuscular, and cardiovascular. GI symptoms include nausea, vomiting, intestinal colic, and diarrhea; neuromuscular symptoms range from weakness to ascending paralysis to respiratory failure; while cardiovascular manifestations range from electrocardiogram (ECG) changes to cardiac arrhythmias and arrest. ECG changes that may be seen with hyperkalemia include

  • Peaked T waves (early change)

  • Flattened P wave

  • Prolonged PR interval (first-degree block)

  • Widened QRS complex

  • Sine wave formation

  • Ventricular fibrillation

(See Schwartz 10th ed., p. 71.)

Hypocalcemia may cause which of the following?

A. Congestive heart failure


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