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Ch. 25 Fluid, Electrolyte, and Acid-Base Homeostasis
Amerman- Human Anatomy & Physiology 3e
Amerman3rd EditionHuman Anatomy & PhysiologyISBN: 9780138247201, 9780138247928, 9780138201814Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoAmerman 3rd EditionCh. 25 Fluid, Electrolyte, and Acid-Base HomeostasisProblema L3.3
Capitolo 25, Problema L3.3

Ms. Johanssen is a patient in the hospital. The nurse examines her laboratory reports and notices that she has developed hyperkalemia and acidosis over the past several days. On closer examination of her medical chart, the nurse also sees that her physician recently doubled her dose of spironolactone, an aldosterone-blocking diuretic. How does this explain her laboratory findings?

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Understand the role of aldosterone: Aldosterone is a hormone that promotes sodium reabsorption and potassium excretion in the kidneys. It also helps regulate acid-base balance by promoting hydrogen ion excretion. Spironolactone, as an aldosterone-blocking diuretic, inhibits these processes.
Explain hyperkalemia: By blocking aldosterone, spironolactone reduces potassium excretion in the kidneys. This leads to an accumulation of potassium in the blood, a condition known as hyperkalemia.
Explain acidosis: Aldosterone also promotes the excretion of hydrogen ions in the kidneys. When aldosterone is blocked by spironolactone, hydrogen ions are retained, leading to a decrease in blood pH, which is referred to as acidosis.
Connect the findings to the medication dose: The doubling of the spironolactone dose would amplify its aldosterone-blocking effects, further reducing potassium and hydrogen ion excretion. This explains the worsening hyperkalemia and acidosis observed in Ms. Johanssen's laboratory reports.
Summarize the physiological impact: The combination of hyperkalemia and acidosis is a direct result of the increased spironolactone dose, which disrupts the normal balance of potassium and hydrogen ions regulated by aldosterone in the kidneys.

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Hyperkalemia

Hyperkalemia refers to an elevated level of potassium in the blood, which can lead to serious cardiac and muscular complications. It often occurs when the kidneys are unable to excrete sufficient potassium, or when potassium intake exceeds the body's ability to eliminate it. In the context of diuretics, certain medications, like spironolactone, can cause potassium retention, contributing to hyperkalemia.
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Acidosis

Acidosis is a condition characterized by an excess of acid in the body fluids, leading to a decrease in blood pH. It can result from various factors, including respiratory issues or metabolic disturbances. In patients with hyperkalemia, acidosis can occur as potassium ions shift from the intracellular to the extracellular space, causing hydrogen ions to move into cells, thus increasing acidity in the blood.
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Spironolactone

Spironolactone is a potassium-sparing diuretic that works by blocking the action of aldosterone, a hormone that promotes sodium retention and potassium excretion. By inhibiting aldosterone, spironolactone leads to increased sodium excretion while retaining potassium. This mechanism can explain the patient's hyperkalemia, especially after the recent increase in her medication dosage, which may have exacerbated her potassium levels.
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