The nurse is caring for a patient with severe burns who is receiving IV fluid resuscitation with lactated Ringer's solution. The nurse understands that this type of solution is used for this patient because it:

Choice A reason: Sodium. Sodium is not affected by serum phosphate level in chronic kidney disease (CKD) patients. Sodium level is mainly regulated by the renin-angiotensin-aldosterone system and the antidiuretic hormone. Sodium level can be altered by fluid intake, fluid loss, diuretics, or salt restriction, but not by phosphate level.

Choice B reason:

Magnesium. Magnesium is also not affected by serum phosphate level in CKD patients. Magnesium level is mainly influenced by dietary intake, intestinal absorption, renal excretion, and exchange with bone and soft tissues. Magnesium level can be altered by malnutrition, malabsorption, diarrhea, vomiting, diuretics, or alcoholism, but not by phosphate level.

Choice C reason:

Calcium. Calcium is the correct answer because calcium and phosphate have an inverse relationship in the body. When serum phosphate level is elevated, as in CKD patients, serum calcium level tends to decrease. This is because high phosphate level binds to calcium and forms insoluble complexes that are deposited in soft tissues and bones. This reduces the amount of free calcium in the blood and triggers the secretion of parathyroid hormone (PTH), which further lowers the calcium level by increasing its excretion in the urine.

Choice D reason:

Bicarbonate. Bicarbonate is not directly affected by serum phosphate level in CKD patients. Bicarbonate level is mainly determined by the acid-base balance in the body. Bicarbonate level can be altered by metabolic acidosis or alkalosis, respiratory acidosis or alkalosis, renal failure, or diarrhea, but not by phosphate level.

Choice A: Decreased serum pH. This is incorrect because hypokalemia usually causes increased serum pH, not decreased. This is because low potassium levels can lead to metabolic alkalosis, a condition where the blood is too alkaline due to loss of acid from the body. This can happen in cases of vomiting, diuretic use, or mineralocorticoid excess.

Choice B:

Increased serum calcium. This is incorrect because hypokalemia does not directly affect serum calcium levels. However, hypokalemia can cause hypomagnesemia, or low magnesium levels, which can in turn cause hypercalcemia, or high calcium levels. This is because magnesium is needed for the secretion of parathyroid hormone (PTH), which regulates calcium balance in the body. Low magnesium levels can lead to increased PTH secretion and increased calcium reabsorption from the bones and kidneys.

Choice C:

Decreased serum magnesium. This is correct because hypokalemia and hypomagnesemia often occur together, especially in cases of chronic diarrhea, malabsorption, alcoholism, or diuretic use. This is because potassium and magnesium are both lost in the urine or stool when these conditions are present. Hypomagnesemia can also cause hypokalemia by impairing the reabsorption of potassium in the kidneys and increasing the entry of potassium into the cells.

Choice D:

Increased serum bicarbonate. This is incorrect because hypokalemia usually causes decreased serum bicarbonate, not increased. This is because low potassium levels can lead to metabolic acidosis, a condition where the blood is too acidic due to accumulation of acid in the body. This can happen in cases of diabetic ketoacidosis, renal tubular acidosis, or chronic kidney disease.