Metabolic acidosis with a normal anion gap (AG) occurs with:
Metabolic acidosis with a normal anion gap (AG) results from either acid administration (HCl or NH/) 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.
All are possible causes of postoperative hyponatremia EXCEPT:
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.
Which of the following is an early sign of hyperkalemia?
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:
Hypocalcemia may cause which of the following?
Mild hypocalcemia can present with muscle cramping or digital/perioral paresthesias. Severe hypocalcemia leads to decreased cardiac contractility and heart failure. ECG changes of hypocalcemia include prolonged QT interval, T-wave inversion, heart block, and ventricular fibrillation. Hypoparathyroidism and severe pancreatitis are potential causes of hypocalcemia.
The next most appropriate test to order in a patient with a pH of 7.1, Pco2 of 40, sodium of 132, potassium of 4.2, and chloride of 105 is:
Metabolic acidosis results from an increased intake of acids, an increased generation of acids, or an increased loss ofbicarbonate. In evaluating a patient with a low serum bicarbonate level and metabolic acidosis, first measure the AG, an index of unmeasured anions.
AG = [Na] - [Cl + HCO3]
Metabolic acidosis with an increased AG occurs from either exogenous acid ingestion (ethylene glycol, salicylate, or methanol) or endogenous acid production of β-hydroxybutyrate and acetoacetate in ketoacidosis, lactate in lactic acidosis, or organic acids in renal insufficiency.
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