In acid base balance, a pH below 7.35 is indicative of

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2024

Explanation

The normal pH of adult arterial blood is 7.35 to 7.45.
A pH value below 7.35 indicates that the blood is abnormally acidic, a general condition called acidosis.
The term 'Acidosis' is the broadest correct category when only the pH value is given.
To specify whether the acidosis is respiratory or metabolic, additional data like PaCO2 and HCO3− levels are required.

Option A: Respiratory alkalosis is incorrect because alkalosis refers to a state where the blood pH is above 7.45, indicating it is too alkaline, not acidic.
Option B: While metabolic acidosis does present with a pH below 7.35, it is a specific diagnosis. It cannot be confirmed without knowing the bicarbonate (HCO3−) level, which would be low (less than 21 mEq/L). The question does not provide this information.
Option C: Similar to metabolic acidosis, respiratory acidosis is a specific diagnosis that requires more information. It is characterized by a pH below 7.35 and an elevated partial pressure of carbon dioxide (PaCO2 > 45 mm Hg). This data is not provided.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Interpretation of blood pH in acid-base balance as background academic context rather than a clinical decision trigger.
Nurses must be able to quickly recognize that a pH below 7.35 signifies acidosis, which is a critical finding requiring prompt assessment and intervention.
Clinical signs of acidosis a nurse should monitor for include headache, confusion, lethargy, and in severe cases, coma. Compensatory mechanisms like deep, rapid breathing (Kussmaul respirations in metabolic acidosis) may also be present.
What if? If the question also stated the patient was hypoventilating due to an opioid overdose, the answer would shift to 'Respiratory acidosis' because hypoventilation causes CO2 retention, leading to a drop in pH.

How to Approach the Question

First, identify the key value provided in the question: 'a pH below 7.35'.
Recall the normal range for arterial blood pH, which is 7.35 to 7.45.
Determine if the given value is acidic or alkaline. Since it's below 7.35, it is acidic.
Review the options. 'Acidosis' is the general term for an acidic state.
Consider the other options ('Respiratory acidosis', 'Metabolic acidosis'). These are specific types of acidosis. To diagnose them, you need more information (PaCO2 or HCO3− levels).
Since the question only provides the pH, select the most general and accurate term that fits the data, which is 'Acidosis'.

Concept Tested & Keywords

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E6 Nursing Fundamentals Potter Perry 12e Part 5 pp. 55-57, 56-58

E6 Nursing Fundamentals Taylor p. 780-782

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