Yuka is dehydrated, so her physician prescribes intravenous fluids. The attending nurse becomes distracted and erroneously gives Yuka a hypertonic glucose solution instead of normal saline. What effect will this mistake have on Yuka’s plasma ADH levels and urine volume?

Verified step by step guidance

Step 1: Understand the difference between isotonic, hypertonic, and hypotonic solutions. A hypertonic glucose solution has a higher solute concentration than normal plasma, which will affect water movement across cell membranes.

Step 2: Recall that plasma ADH (antidiuretic hormone) levels increase when the body senses dehydration or increased plasma osmolality, promoting water reabsorption in the kidneys to conserve water.

Step 3: Consider that administering a hypertonic glucose solution will increase plasma osmolality, causing water to move out of cells into the extracellular fluid, which the body interprets as dehydration.

Step 4: Predict that the increased plasma osmolality will stimulate the hypothalamus to increase ADH secretion, leading to increased water reabsorption in the kidneys and thus a decrease in urine volume.

Step 5: Summarize that the erroneous hypertonic glucose infusion will raise plasma ADH levels and reduce urine volume as the body attempts to conserve water and restore osmotic balance.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Osmolarity and Tonicity of Intravenous Fluids

Osmolarity refers to the concentration of solutes in a solution, affecting water movement across cell membranes. Normal saline is isotonic, matching plasma osmolarity, while a hypertonic glucose solution has higher osmolarity, drawing water out of cells into the bloodstream. Understanding these differences is crucial to predict fluid shifts and their physiological effects.

Role of Antidiuretic Hormone (ADH) in Fluid Balance

ADH regulates water retention by increasing water reabsorption in the kidneys, thus concentrating urine and reducing urine volume. Its secretion is stimulated by increased plasma osmolarity or decreased blood volume. Changes in plasma osmolarity due to fluid administration directly influence ADH levels to maintain homeostasis.

Effects of Hypertonic Solutions on Plasma Osmolarity and Urine Output

Administering a hypertonic solution raises plasma osmolarity, causing cells to lose water and plasma volume to increase osmolality. This triggers ADH release to conserve water, leading to decreased urine volume. Recognizing this mechanism explains how the incorrect fluid affects Yuka’s ADH secretion and urine production.

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