Acid-Base Imbalances Fundamentals

A focused set of vocabulary flashcards defining key acid-base concepts, normal ABG parameters, compensation mechanisms, clinical causes, interpretation rules, and procedural steps.

Acid-Base Balance

The homeostatic regulation of body fluid hydrogen ion ($\text{H}^+$) concentration maintained through the coordinated function of the lungs, kidneys, and bicarbonate buffer systems.

Normal ABG Reference Ranges

Standard arterial blood gas baseline values: $\text{pH}$: $7.35-7.45$; $\text{PaCO}_2$: $35-45\,\text{mmHg}$; $\text{HCO}_3^-$: $21-28\,\text{mEq/L}$ ($\text{mmol/L}$); $\text{PaO}_2$: $80-100\,\text{mmHg}$; $\text{SaO}_2$: $>95\%$.

R.O.M.E. Mnemonic

A standard tool for ABG interpretation indicating that Respiratory problems cause $\text{pH}$ and $\text{CO}_2$ to move in Opposite directions, while Metabolic problems cause $\text{pH}$ and $\text{HCO}_3^-$ to move in Equal (same) directions.

ABG Interpretation Algorithm

A systematic decision tree used to categorize acid-base disorders by evaluating whether $\text{pH}$ is low or high, followed by checking $\text{CO}_2$ and $\text{HCO}_3^-$ levels.

Cellular Buffering in Acidosis and Alkalosis

Transcellular exchange of ions: in acidosis, excess extracellular $\text{H}^+$ shifts into cells, forcing $\text{K}^+$ out into blood (hyperkalemia); in alkalosis, low extracellular $\text{H}^+$ pulls $\text{H}^+$ out of cells, shifting $\text{K}^+$ inward (hypokalemia).

Respiratory Acidosis

An acid-base disturbance characterized by low $\text{pH}$ ($<7.35$) and elevated $\text{PaCO}_2$ ($>45\,\text{mmHg}$), resulting from hypoventilation and $\text{CO}_2$ retention (e.g., COPD, opioid overdose).

Respiratory Alkalosis

An acid-base disturbance characterized by elevated $\text{pH}$ ($>7.45$) and decreased $\text{PaCO}_2$ ($<35\,\text{mmHg}$), resulting from hyperventilation and excessive $\text{CO}_2$ elimination (e.g., anxiety, panic attack, hypoxia).

Metabolic Acidosis

An acid-base disturbance characterized by low $\text{pH}$ ($<7.35$) and decreased $\text{HCO}_3^-$ ($<21\,\text{mEq/L}$), caused by excess bicarbonate loss (severe diarrhea) or acid buildup (DKA, shock, sepsis, renal failure).

Metabolic Alkalosis

An acid-base disturbance characterized by elevated $\text{pH}$ ($>7.45$) and elevated $\text{HCO}_3^-$ ($>28\,\text{mEq/L}$), caused by excess bicarbonate retention or gastric acid loss (NG suctioning, severe vomiting, diuretics).

Respiratory Compensation

A rapid regulatory response (working within minutes to hours) where the lungs alter respiratory rate to retain or exhale acidic carbon dioxide ($\text{CO}_2$) to offset metabolic imbalances.

Renal Compensation

A slow regulatory response (working over hours to days) where the kidneys excrete or retain hydrogen ions ($\text{H}^+$) or bicarbonate ($\text{HCO}_3^-$) to compensate for respiratory imbalances.

Kussmaul Respirations

A compensatory deep, rapid breathing pattern executed by the lungs during metabolic acidosis (such as DKA) to blow off excess acidic $\text{CO}_2$.

Uncompensated ABG State

An arterial blood gas finding in which $\text{pH}$ is outside the normal range and only one primary indicator ($\text{PaCO}_2$ or $\text{HCO}_3^-$) is abnormal.

Partially Compensated ABG State

An arterial blood gas finding in which $\text{pH}$ remains abnormal, but both $\text{PaCO}_2$ and $\text{HCO}_3^-$ are abnormal as compensation attempts occur.

Fully Compensated ABG State

An arterial blood gas finding in which $\text{pH}$ has returned to normal range ($7.35-7.45$), but both $\text{PaCO}_2$ and $\text{HCO}_3^-$ remain abnormal.

Allen Test

A physical assessment conducted prior to radial arterial puncture to confirm arterial blood supply to the hand by occluding radial and ulnar arteries until blanching occurs, then releasing the ulnar artery to ensure color returns within $<5\,\text{seconds}$.

Post-Draw Arterial Pressure Care

The clinical intervention of applying firm direct pressure to an arterial puncture site for at least $5\,\text{minutes}$ (or longer for clients on anticoagulants) to prevent hematoma formation.