Altered Acid-Base Balance

Comprehensive review flashcards covering the pathophysiology, clinical manifestations, contributing mechanisms, and laboratory findings of altered acid-base balance, including metabolic acidosis and metabolic alkalosis.

How are acids defined in the context of acid-base regulation?

Substances that donate hydrogen ions ($H$).

How are bases defined in the context of acid-base regulation?

Substances that accept hydrogen ions ($H$).

What is pH, and what is the normal range for blood pH?

pH is a clinical measurement indicating the acid-to-base ratio in the body on a scale from $0$ to $14$. Normal blood pH is $7.35\text{--}7.45$.

What is the clinical significance of the anion gap?

It is a value used to help identify the cause of metabolic acidosis.

What primary deficit defines metabolic acidosis?

A deficit of bicarbonate ($HCO_3$), which leads to a decrease in blood pH and increased acidity.

How does decreased secretion of acids by the kidneys cause metabolic acidosis?

When the kidneys cannot effectively eliminate hydrogen ions ($H$), acid builds up in the bloodstream, commonly seen in renal failure or tubular disorders.

Why does prolonged diarrhea lead to metabolic acidosis?

Prolonged diarrhea causes excessive loss of bicarbonate ($HCO_3$) from the intestine, reducing the base needed to neutralize acids.

How does an increase in chloride ($Cl$) contribute to metabolic acidosis?

Excess chloride replaces bicarbonate in the blood, creating a dilution effect that decreases buffering capacity (commonly seen in hyperchloremic acidosis).

What causes metabolic acidosis via the increased production of nonvolatile acids?

The excessive production of acids that cannot be exhaled through the lungs, such as lactic acid (in shock or sepsis) or ketones (in diabetic ketoacidosis).

What causes weakness, lethargy, and coma in metabolic acidosis?

Weakness is caused by impaired cellular energy production (especially in muscle cells). Lethargy, confusion, and coma result from low blood pH depressing the brain and central nervous system.

What cardiovascular and dermatological manifestations are seen in metabolic acidosis?

Vasodilation leading to dropped blood pressure and flushed skin, as well as bradycardia (decreased heart rate) due to acid impairing the heart's electrical activity.

What specific arterial blood gas (ABG) findings characterize metabolic acidosis?

$pH < 7.35$, decreased $HCO_3^-$ ($< 24\,mEq/L$ confirming a metabolic origin), and decreased $CO_2$ resulting from respiratory compensation.

What defines metabolic alkalosis?

An increased blood pH caused by a plasma excess of bicarbonate ($HCO_3$).

What are the three contributing mechanisms of metabolic alkalosis?

Decreased $H^+$ ions, increased $HCO_3$ ions, and loss of $Cl^-$ ions.

What are the clinical manifestations of metabolic alkalosis?

Patients may be asymptomatic or exhibit signs related to hypokalemia, such as muscle weakness, fatigue, and cardiac dysrhythmia.

What laboratory values are diagnostic of metabolic alkalosis?

$pH > 7.45$ and $HCO_3 > 31\,mEq/L$.