Ch. 26 Fluid, Electrolyte, and Acid-Base Balance

Marieb - Human Anatomy & Physiology 11th Edition

Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Not the one you use?Change textbook

Marieb, Hoehn 11th Edition

Ch. 26 Fluid, Electrolyte, and Acid-Base Balance

Problem 23

Chapter 26, Problem 23

Mrs. Bush, a 70-year-old woman, is admitted to the hospital. Her history states that she has been suffering from diarrhea for three weeks. On admission, she complains of severe fatigue and muscle weakness. A blood chemistry study yields the following information: Na⁺ 142 mEq/L; K⁺ 1.5 mEq/L; Cl⁻ 92 mEq/L; Pco₂ 32 mm Hg.
Which electrolytes are within normal limits? Which are so abnormal that the patient has a medical emergency?
Which of the following represents the greatest danger to Mrs. Bush?
a. A fall due to her muscular weakness
b. Edema
c. Cardiac arrhythmia and cardiac arrest.

Verified step by step guidance

Identify the normal reference ranges for the electrolytes and blood gas values given: typically, Na⁺ (sodium) is 135-145 mEq/L, K⁺ (potassium) is 3.5-5.0 mEq/L, Cl⁻ (chloride) is 98-106 mEq/L, and Pco₂ (partial pressure of carbon dioxide) is 35-45 mm Hg.

Compare Mrs. Bush's values to these normal ranges: Na⁺ is 142 mEq/L (within normal limits), K⁺ is 1.5 mEq/L (significantly low), Cl⁻ is 92 mEq/L (low), and Pco₂ is 32 mm Hg (slightly low).

Recognize that severe hypokalemia (very low potassium) is a medical emergency because potassium is critical for normal muscle and cardiac function, and such a low level can cause life-threatening cardiac arrhythmias.

Understand that while muscle weakness and risk of falls are concerns, the greatest immediate danger is cardiac arrhythmia and cardiac arrest due to the hypokalemia.

Conclude that the normal electrolyte here is sodium, the most abnormal and dangerous electrolyte disturbance is potassium, and the greatest danger to Mrs. Bush is option c: cardiac arrhythmia and cardiac arrest.

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Key Concepts

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

Electrolyte Normal Ranges and Imbalances

Electrolytes like sodium (Na⁺), potassium (K⁺), and chloride (Cl⁻) have established normal blood ranges essential for bodily functions. Deviations can cause symptoms and complications; for example, normal potassium is typically 3.5–5.0 mEq/L, and severe hypokalemia (like 1.5 mEq/L) can be life-threatening. Understanding these ranges helps identify which values are normal or critical.

Clinical Consequences of Hypokalemia

Hypokalemia, or low potassium levels, can cause muscle weakness, fatigue, and most critically, cardiac arrhythmias. Potassium is vital for normal cardiac electrical activity, and severe deficiency increases the risk of dangerous heart rhythms and cardiac arrest, making it a medical emergency requiring prompt treatment.

Interpreting Acid-Base and Electrolyte Disturbances in Diarrhea

Prolonged diarrhea leads to loss of fluids and electrolytes, often causing hypokalemia and metabolic acidosis or respiratory compensation (reflected in Pco₂). Recognizing how diarrhea affects electrolyte balance and acid-base status is crucial for diagnosing the underlying problem and prioritizing treatment to prevent complications.

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Acids and Bases

Related Practice

Textbook Question

Mr. Jessup, a 55-year-old man, is operated on for a cerebral tumor. About a month later, he appears at his physician's office complaining of excessive thirst. He claims to have been drinking about 20 liters of water daily for the past week and says he has been voiding nearly continuously. A urine sample is collected and its specific gravity is reported as 1.001.

What is your diagnosis of Mr. Jessup's problem?

What connection might exist between his previous surgery and his present problem?

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Textbook Question

For each of the following sets of blood values, name the acid-base imbalance (acidosis or alkalosis), determine its cause (metabolic or respiratory), decide whether the condition is being compensated, and cite at least one possible cause of the imbalance. Problem 1: pH 7.63; Pco₂ 19 mm Hg; Hco₃⁻ 19.5 mEq/L Problem 2: pH 7.22; Pco₂ 30 mm Hg; Hco₃⁻ 12.0 mEq/L

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Textbook Question

Explain how emphysema and congestive heart failure can lead to acid-base imbalance.

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Textbook Question

During a routine medical checkup, Shelby, a 26-year-old physiotherapy student, is surprised to hear that her blood pressure is 180/110. She also has a rumbling systolic and diastolic abdominal bruit (murmur) that is loudest at the mid-epigastric area. Her physician suspects renal artery stenosis (narrowing). She orders an abdominal ultrasound and renal artery arteriography, which confirm that Shelby has a small right kidney and the distal part of her right renal artery is narrowed by more than 70%. Her physician prescribes diuretics and calcium channel blockers as temporary measures, and refers Shelby to a cardiovascular surgeon. Explain the connection between Shelby's renal artery stenosis and her hypertension. Why is her right kidney smaller than her left? What would you expect Shelby's blood levels of K⁺, Na⁺, aldosterone, angiotensin II, and renin to be?

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