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Difficulty: HardPhysiological Adaptation

During interdisciplinary rounds, the healthcare team evaluates a client with a mechanical small bowel obstruction who has been receiving continuous nasogastric decompression for the past 48 hours. The client reports new-onset perioral numbness and tingling in the fingers. Simultaneously, the telemetry monitor displays frequent premature ventricular contractions. Based on these findings, which physiological interpretation correctly identifies the underlying derangement and its consequences?

  1. Loss of gastric acid has caused metabolic alkalosis, leading to a decrease in ionized calcium and an intracellular shift of potassium.Answer
  2. B
    Removal of lower intestinal secretions has induced metabolic acidosis, resulting in hyperkalemia and generalized central nervous system depression.
  3. C
    Third-spacing of fluids has initiated early hypovolemic shock, causing peripheral vasoconstriction that manifests as numbness and cardiac irritability.
  4. D
    Diaphragmatic splinting has led to acute respiratory acidosis, making the establishment of a patent airway the most critical immediate priority.

Answer

The client is experiencing metabolic alkalosis due to gastric acid loss, which subsequently causes hypocalcemia (leading to numbness and tingling) and hypokalemia (leading to premature ventricular contractions).
Continuous nasogastric suctioning aggressively removes hydrochloric acid, precipitating metabolic alkalosis. In an alkalotic state, two critical physiological adaptations occur. First, hydrogen ions shift into the extracellular fluid to compensate, forcing potassium into the intracellular space and causing severe hypokalemia, which triggers the premature ventricular contractions. Second, the alkalosis increases the binding affinity of calcium to serum proteins, significantly reducing ionized calcium levels. This resulting hypocalcemia causes profound neuromuscular excitability, classically presenting as perioral numbness and tingling (paresthesia).

Step-by-Step Solution

1
Analyze the systemic impact of continuous nasogastric decompression.
The continuous removal of stomach contents depletes hydrochloric acid, leading to a systemic increase in blood pH, known as metabolic alkalosis.
Gastric secretions are highly acidic; their sustained removal without replacement creates an acid-base imbalance.
2
Evaluate the effect of metabolic alkalosis on serum calcium levels.
The elevated blood pH enhances the binding of calcium to serum albumin, which lowers the level of physiologically active (ionized) calcium in the blood.
Hypocalcemia increases neuromuscular excitability, which is directly responsible for the client's perioral numbness and tingling in the fingers (paresthesia).
3
Evaluate the effect of metabolic alkalosis on serum potassium levels.
To compensate for the alkalosis, hydrogen ions exit the cells to buffer the blood, forcing potassium ions to shift into the intracellular space, resulting in hypokalemia.
Hypokalemia significantly increases myocardial irritability and delays ventricular repolarization, manifesting on the telemetry monitor as premature ventricular contractions (PVCs).

Key Concept

The physiological consequences of metabolic alkalosis, specifically the resultant shifts in calcium and potassium that produce distinct neuromuscular and cardiac manifestations.
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Topics

Physiological Adaptation

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