ACID-BASED IMBALANCE

ACID-BASED IMBALANCE

Instructor Information

• Course: NUR 113 Spring 2026
• Institution: Bishop State Community College
• Instructor: LashaWndree Brown-Johnson, RN, MSN, CCRN, CNE

Learning Objectives

• Define Acid-Base Balance and understand its physiological importance.
• Explain the concepts of pH, acids, bases, and buffering systems.
• Interpret Arterial Blood Gases (ABGs) with a systematic approach.
• Recognize and manage common acid-base imbalances.
• Describe the effects of asthma, COPD, and emphysema on acid-base balance.
• Apply knowledge to clinical practice through case studies and ABG interpretation.
  • Pay particular attention to how electrolytes influence acid-base balance and how this shows up in patient symptoms and labs.

Introduction to Acid-Base Balance

• What is Acid-Base Balance?

  • Refers to the balance between acids and bases in the body to maintain a stable pH level (7.35–7.45).
  • Enzyme activity, oxygen delivery, and muscle/nerve function all depend on a normal pH.
  • Even small changes in pH can have serious effects on the brain, heart, and lungs.

• pH = potential of hydrogen

  • Measures H⁺ (hydrogen ion) concentration:
  • The more H⁺ → the more acidic
  • The fewer H⁺ → the more basic (alkaline)

• pH Rule of Thumb:

  • ↑ H⁺ = ↓ pH = Acidosis
  • ↓ H⁺ = ↑ pH = Alkalosis

Arterial Blood Gas (ABG) Assessment

What is Arterial Blood?

• Blood obtained from an artery, rich in oxygen (unlike venous blood).
• Used to measure arterial blood gases (ABG) for assessing gas exchange and acid-base status.

Why Use Arterial Blood?

• Provides accurate data on oxygen (PaO₂) and carbon dioxide (PaCO₂) levels.
• Used to assess acid-base balance and detect respiratory/metabolic acidosis or alkalosis.

Allen Test

Purpose of the Allen Test

• Ensures adequate blood flow to the hand before performing an arterial puncture.
• Verifies patency of the ulnar artery (if radial artery is punctured).
• Ensures hand receives blood if radial artery is damaged.

Steps to Perform the Allen Test

1. Patient clenches fist to restrict blood flow.
2. Examiner occludes both the radial and ulnar arteries.
3. Patient opens fist (palm should appear pale).
4. Examiner releases the ulnar artery while compressing the radial artery.
5. If hand flushes pink quickly, the ulnar artery is patent, and ABG can be safely drawn.

Normal Test Outcomes

• Hand flushes pink within 5–10 seconds.

Abnormal Test Outcomes

• Delayed or absent return of color suggests insufficient ulnar blood flow; the radial artery should not be punctured.

Procedure Considerations

• Common puncture sites: radial, brachial, and femoral arteries.
• Avoid drawing from an arm with a dialysis shunt or compromised circulation.

Buffers – First Line of Defense

What are Buffers?

• The first line of defense against pH changes.
• Act as hydrogen ion "sponges" (can release or bind H⁺ depending on pH).
• Always present in body fluids, working quickly to normalize free H⁺ levels.

Types of Buffers

• Bicarbonate (HCO₃⁻) – main extracellular fluid buffer.
• Phosphate – active in intracellular fluid.
• Proteins – include albumin and globulins.
• Hemoglobin – major intracellular fluid protein buffer.

How Buffers Work

• ↑ H⁺ → Buffers bind excess hydrogen ions.
• ↓ H⁺ → Buffers release hydrogen ions.

Three Regulatory Mechanisms

1. Chemical (Buffers) Response
   • Very rapid (immediate) response.
   • Handles small fluctuations but has a limited capacity.
2. Respiratory (Lungs) Response
   • Rapid (seconds to minutes).
   • Controls CO₂ elimination and assists buffers in acute situations.
3. Kidney (Renal) Response
   • Slow (24–48 hours) but is the most powerful regulator.
   • Handles large or chronic imbalances and controls HCO₃⁻ retention/excretion and H⁺ excretion.

Key Point

• Buffers → fast but limited; Kidneys → slow but powerful.

Carbonic Anhydrase Equation

The Key Equation

$CO₂ + H₂O <br /> ightleftharpoons H₂CO₃ <br /> ightleftharpoons H⁺ + HCO₃⁻$

• Carbon dioxide + water ⇌ carbonic acid ⇌ hydrogen ion + bicarbonate.

Why This Matters

• CO₂ and H⁺ are directly related:
  • ↑ CO₂ = ↑ H⁺ = ↓ pH (more acidic)
  • ↓ CO₂ = ↓ H⁺ = ↑ pH (more alkaline)

Clinical Application

• Excess CO₂ retained → equation shifts right → more H⁺ produced → acidosis.
• Excess CO₂ exhaled → equation shifts left → less H⁺ → alkalosis.

Remember

• Lungs control CO₂ = control pH. Exhale CO₂ = "blow off" acid.

Acids, Bases, and pH Control

Acids

• Donate hydrogen ions (H⁺).
• Cause pH to decrease:
  • pH < 7.35 = Acidosis
  • Examples: carbonic acid, lactic acid.
  • Common cause: CO₂ retention.

Bases (Alkaline Substances)

• Accept or bind H⁺ ions.
• Cause pH to increase:
  • pH > 7.45.
  • Example: bicarbonate (HCO₃⁻).
  • Common cause: excess antacids or vomiting.

pH Balance is Controlled By

• Lungs (Respiratory): regulate CO₂ (acid).
• Kidneys (Metabolic): regulate HCO₃⁻ (base).

ABG Components

PaCO₂ – Carbon Dioxide

• Respiratory component.
  • Normal: 35–45 mmHg.
  • ↑ PaCO₂ > 45 mmHg = Respiratory Acidosis (hypoventilation, CO₂ retention).
  • ↓ PaCO₂ < 35 mmHg = Respiratory Alkalosis (hyperventilation, blowing off CO₂).
  • Controlled by the lungs (ventilation).

HCO₃⁻ – Bicarbonate

• Metabolic component.
  • Normal: 21–28 mEq/L.
  • ↓ HCO₃⁻ < 21 mEq/L = Metabolic Acidosis.
  • ↑ HCO₃⁻ > 28 mEq/L = Metabolic Alkalosis.
  • Controlled by the kidneys.

PaO₂ – Partial Pressure of Oxygen

• Normal: 80–100 mmHg.
  • Measures oxygen in arterial blood.
  • ↓ PaO₂ = Hypoxemia (less O₂ binds to HGB).
  • ↑ PaO₂ = often due to excessive oxygen therapy.
  • Does not determine acid-base imbalance but is important for patient assessment.

SaO₂ (Oxygen Saturation)

• >95% = adequate oxygen delivery.
• Tip:
  • PaCO₂ = think lungs;
  • HCO₃⁻ = think kidneys;
  • PaO₂ = think oxygen status, not acid-base directly.

ABG Interpretation Steps

1. Check the pH.
   • Normal Range: 7.35 – 7.45.
   • pH < 7.35 → Acidosis.
   • pH > 7.45 → Alkalosis.
2. Look at PaCO₂ (Respiratory)
   • Normal: 35 – 45 mmHg.
   • PaCO₂ > 45 → Respiratory Acidosis.
   • PaCO₂ < 35 → Respiratory Alkalosis.
3. Look at HCO₃⁻ (Metabolic)
   • Normal: 21 – 28 mEq/L.
   • HCO₃⁻ < 22 → Metabolic Acidosis.
   • HCO₃⁻ > 26 → Metabolic Alkalosis.
4. Check PaO₂
   • Normal: 80 – 100 mmHg.
   • Helps assess oxygenation status.
   • Low PaO₂ = hypoxemia.
   • Not part of acid-base diagnosis, but still clinically important.

ROME Mnemonic

Quick ABG Interpretation Guide

• ROME:
  • Ro: Respiratory
  • Opposite: pH and PaCO₂ move in opposite directions.
  • Me: Metabolic
  • Equal: pH and HCO₃⁻ move in the same direction.

Acidosis:

• pH ↓ , PaCO₂ ↑

Alkalosis:

• pH ↑ , PaCO₂ ↓

Interpretation of pH and HCO₃⁻:

1. Acidosis: pH ↓ , HCO₃⁻ ↓
2. Alkalosis: pH ↑ , HCO₃⁻ ↑

Remember

• When in ROME, check if the values go in Opposite or Equal directions to identify the primary disorder!

ABG Practice Interpretation

• Example ABG Values:
  1. pH: 7.30, PaCO₂: 52, HCO₃⁻: 24
  2. pH: 7.50, PaCO₂: 30, HCO₃⁻: 24
  3. pH: 7.32, PaCO₂: 40, HCO₃⁻: 18
  4. pH: 7.46, PaCO₂: 40, HCO₃⁻: 28
  5. pH: 7.28, PaCO₂: 50, HCO₃⁻: 24
  6. pH: 7.36, PaCO₂: 40, HCO₃⁻: 24
  7. pH: 7.25, PaCO₂: 38, HCO₃⁻: 16
  8. pH: 7.51, PaCO₂: 38, HCO₃⁻: 29
  9. pH: 7.44, PaCO₂: 30, HCO₃⁻: 24
  10. pH: 7.20, PaCO₂: 65, HCO₃⁻: 24
  11. pH: 7.33, PaCO₂: 38, HCO₃⁻: 15
  12. pH: 7.47, PaCO₂: 34, HCO₃⁻: 24
  13. pH: 7.36, PaCO₂: 38, HCO₃⁻: 24
  14. pH: 7.52, PaCO₂: 40, HCO₃⁻: 28
  15. pH: 7.34, PaCO₂: 55, HCO₃⁻: 24
  16. pH: 7.30, PaCO₂: 50, HCO₃⁻: 24
  17. pH: 7.48, PaCO₂: 36, HCO₃⁻: 28
  18. pH: 7.26, PaCO₂: 33, HCO₃⁻: 18
  19. pH: 7.51, PaCO₂: 28, HCO₃⁻: 23
  20. pH: 7.38, PaCO₂: 41, HCO₃⁻: 24

Compensation Mechanisms – Overview

What is Compensation?

• Body's attempt to restore normal pH.
• Counteracts acid-base imbalances.
• Does not fix the underlying cause, only stabilizes pH.

Critical pH Values

• pH < 6.9 or > 7.8 = usually fatal.

Two Compensating Systems

1. Lungs (Respiratory)
   • Fast response (seconds to minutes)
   • Can be overwhelmed easily.
2. Kidneys (Metabolic)
   • Slow response (24–48 hours)
   • Most powerful regulator.

Key Principle

• Opposite system compensates for the problem.

Respiratory Compensation

When Does it Occur?

• Lungs compensate for metabolic problems.
• Response begins within seconds to minutes.

How It Works

• Lungs regulate CO₂ (an acid).
• Changes rate and depth of breathing.

Limitations

• Can be overwhelmed by severe imbalances.

For Metabolic Acidosis

• ↑ Breathing (hyperventilation) blows off CO₂ → raises pH.
  • Example: Kussmaul breathing in diabetic ketoacidosis (DKA).

For Metabolic Alkalosis

• ↓ Breathing (hypoventilation) retains CO₂ → lowers pH.

Remember

• Fast breathing = ↓ acid (less CO₂);
• Slow breathing = ↑ acid (more CO₂).

Kidney (Metabolic) Compensation

When Does it Occur?

• Kidneys compensate for respiratory problems.
• Response takes 24–48 hours; it is the most powerful regulator.

How It Works

• Kidneys regulate HCO₃⁻ (base).
• Excrete or retain H⁺ ions.

Can Handle Large/Chronic Imbalances:

• For Respiratory Acidosis:
  • Kidneys retain bicarbonate (HCO₃⁻).
  • Excrete hydrogen ions (H⁺) → raises pH.
    Example: COPD patient with ↑ HCO₃⁻
• For Respiratory Alkalosis:
  • Kidneys excrete bicarbonate (HCO₃⁻).
  • Retain hydrogen ions (H⁺) → lowers pH.

Levels of Compensation

Uncompensated

• pH is abnormal; no compensation has started yet; only one value (PaCO₂ or HCO₃⁻) is abnormal.

Partial Compensation

• pH is still abnormal but moving toward normal; both PaCO₂ and HCO₃⁻ are abnormal; body is trying but hasn't succeeded yet.

Full (Complete) Compensation

• pH has returned to normal (7.35–7.45); both PaCO₂ and HCO₃⁻ remain abnormal; body worked hard to normalize pH.
  • Example: pH 7.36, PaCO₂ 55, HCO₃⁻ 30 = fully compensated respiratory acidosis (normal pH, ↑ PaCO₂, ↑ HCO₃⁻).

ABG Practice: Uncompensated

Uncompensated Conditions

• Signs: pH abnormal; only one value (CO₂ or HCO₃⁻) abnormal.
• Examples:
  • pH: 7.28, PaCO₂: 58, HCO₃⁻: 24
  • pH: 7.52, PaCO₂: 28, HCO₃⁻: 24
  • pH: 7.30, PaCO₂: 40, HCO₃⁻: 16
  • pH: 7.48, PaCO₂: 40, HCO₃⁻: 32
  • pH: 7.22, PaCO₂: 62, HCO₃⁻: 25

ABG Practice: Partially Compensated

Partial Compensation Signs

• pH still abnormal, both PaCO₂ and HCO₃⁻ abnormal; body is trying but hasn't succeeded yet.
• Examples:
  • pH: 7.32, PaCO₂: 55, HCO₃⁻: 29
  • pH: 7.48, PaCO₂: 30, HCO₃⁻: 20
  • pH: 7.30, PaCO₂: 30, HCO₃⁻: 15
  • pH: 7.50, PaCO₂: 50, HCO₃⁻: 38

ABG Practice: Fully Compensated

Full Compensation Signs

• pH normal (7.35–7.45), both PaCO₂ and HCO₃⁻ abnormal; body worked hard to normalize pH.
• Examples:
  • pH: 7.37, PaCO₂: 55, HCO₃⁻: 32
  • pH: 7.43, PaCO₂: 30, HCO₃⁻: 19
  • pH: 7.36, PaCO₂: 30, HCO₃⁻: 17
  • pH: 7.44, PaCO₂: 48, HCO₃⁻: 33

Respiratory Acidosis

Definition

• Caused by alveolar hypoventilation, leading to CO₂ retention, low pH (

Common Causes

• CNS depression (head trauma, anesthesia, spinal cord injury).
• Hypoventilation.
• COPD, asthma, emphysema.
• Pneumothorax, severe pulmonary infection or edema.
• Pulmonary embolism, neuromuscular diseases (myasthenia gravis, MS).

Clinical Manifestations

• Dyspnea, headache, confusion.
• Tachycardia, dysrhythmias.
• Lethargy, drowsiness, decreased responsiveness, respiratory distress.

Treatment Goals

• Correct ventilation and reduce CO₂.
• Support airway, oxygenation, and underlying cause.

Medical Interventions

• Bronchodilators, oxygen.
• Treat infection or hyperkalemia.
• Chest physiotherapy or chest tube.
• Intubation if needed.
• Reverse sedation if applicable.
• Diuretics for pulmonary edema.

Nursing Interventions

• Maintain airway, monitor ABGs and vitals.
• Watch for ↓ LOC, ↑ PaCO₂, or worsening distress.
• Administer oxygen cautiously.
• Supportive care and teaching.
• Monitor potassium (↑ in acidosis).

Nursing Safety Priority – Acidosis

• Critical rescue: Assess cardiovascular system first in any patient at risk for acidosis!
  • Acidosis → hyperkalemia → cardiac arrest.
  • Acidosis causes K⁺ to shift out of cells.
  • Elevated serum K⁺ = dysrhythmias.

Monitor for:

• ECG changes: tall, peaked T waves.
• Widened QRS complex, bradycardia → heart block, hypotension, weak pulses.

Priority Actions

• Report cardiac changes immediately.
• Monitor potassium levels closely.
• Assess airway if respiratory acidosis.

Key Features: Acidosis

Cardiovascular

• Bradycardia to heart block.
• Tall T waves, widened QRS, prolonged PR.
• Hypotension, thready pulses.

Central Nervous System

• Depressed activity (lethargy, confusion, stupor, coma).

Neuromuscular

• Hyporeflexia, skeletal muscle weakness, flaccid paralysis.

Respiratory

• Kussmaul respirations (metabolic acidosis), variable/ineffective respirations (respiratory acidosis).

Integumentary

• Metabolic: warm, flushed, dry skin; Respiratory: pale-to-cyanotic, dry skin.

Memory Tip

• Acidosis = depressed; think: lethargy, hyporeflexia, flaccid, slow HR.

Respiratory Acidosis Symptoms

Respiratory

• Hypoventilation → hypoxia.
• Rapid, shallow respirations; dyspnea.

Cardiovascular

• ↓ BP with vasodilation; dysrhythmias; thready pulses.

Electrolytes

• Hyperkalemia (K⁺) → cardiac risk!

Neurological

• Headache, drowsiness, dizziness, confusion → coma.

Neuromuscular

• Muscle weakness, hyporeflexia, flaccid paralysis.

Common Causes of Respiratory Acidosis

• COPD/emphysema, pneumonia, atelectasis, CNS depression, opioid overdose, anesthesia, chest trauma.

Respiratory Alkalosis

Definition

• Hyperventilation leads to excessive CO₂ excretion, resulting in a high pH and low PaCO₂.

Causes of Respiratory Alkalosis

• Anxiety and nervousness, fear and pain, fever, gram-negative septicemia.
• Hyperventilation, lung conditions (pneumonia, PE), thyrotoxicosis, CNS lesions, salicylate overdose, hepatic failure, pregnancy, early pulmonary edema.

Clinical Manifestations

• Hyperventilation, light-headedness, confusion, decreased concentration.
• Paresthesias, tetanic spasms in extremities, cardiac dysrhythmias, palpitations, sweating, dry mouth, blurred vision.

Treatment

• Discontinue/remove causative agent.
• Treat fever with cooling measures or antibiotics.
• Eliminate sepsis source, oxygen therapy for hypoxemia.
• Anxiolytics/sedatives for anxiety.
• Diuretics for pulmonary edema, rebreathing exhaled air using a paper bag or cupped hands.
• For intubated patients: adjust ventilator settings (decrease tidal volume or rate).

Nursing Management

• Assessment & analysis, obtain full history and clinical presentation.
• Monitor vital signs and ABGs (especially pH and PaCO₂).

Nursing Interventions

• Encourage slow, deep breathing.
• Monitor vital signs.
• Provide emotional support and reassurance.
• Assist with ADLs, promote patient education and safety measures.

Complications

• Seizures due to reduced cerebral oxygenation.
• Chest pain from cardiac/noncardiac sources related to hyperventilation.

Nursing Safety Priority – Alkalosis

Key Concerns in Alkalosis

• Alkalosis → hypokalemia, hypocalcemia (ionized); both cause neuromuscular irritability.

Signs to Monitor

• Muscle cramps, tetany, twitching.
• Positive Chvostek & Trousseau signs.
• Cardiac dysrhythmias, increased digoxin toxicity.
• Fall precautions implement for all patients with alkalosis!

Why?

• Hypotension from vasodilation.
• Muscle weakness from hypokalemia.
• Confusion and dizziness.

Priority Nursing Interventions

• Monitor neuro status Q2H.
• Replace K⁺, Ca²⁺, Cl⁻ as ordered.

Respiratory Alkalosis Symptoms

Respiratory

• Hyperventilation, ↑ rate & depth, blowing off CO₂.

Neuromuscular

• Hyperreflexia, muscle cramping & twitching, tetany.

Cardiovascular

• Tachycardia, ↓ or normal BP, palpitations.

Electrolytes

• Hypokalemia (↓ K⁺), hypocalcemia (↓ Ca²⁺).

Neurological

• Anxiety, ↑ irritability, lightheadedness, confusion → seizures.
• ↑ CO₂ loss, paresthesias, numbness & tingling (Chvostek sign, Trousseau sign).

Metabolic Acidosis

Definition

• Caused by an accumulation of metabolic acids or loss of bicarbonate, leading to decreased arterial pH.

Causes of Metabolic Acidosis

• Accumulation of acid: renal failure, diabetic ketoacidosis, anaerobic metabolism (lactic acidosis), starvation, salicylate intoxication.
• Loss of base: severe diarrhea, intestinal fistulas.

Clinical Manifestations

• Headache, confusion, restlessness, lethargy, weakness, stupor/coma.
• Kussmaul respirations (deep, rapid), nausea, vomiting.
• Dysrhythmias, warm/flushed skin, seizures, twitching, peripheral vasodilation.

Treatment

• IV sodium bicarbonate if pH < 7.1.
• IV fluids to maintain volume, insulin for diabetic ketoacidosis.
• Antidiarrheals if bicarbonate loss is due to diarrhea.
• Dialysis for renal failure/toxic causes.
• Mechanical ventilation if needed for respiratory support.

Nursing Interventions

• Monitor BP, HR, respiratory rate, and rhythm.
• Monitor perfusion and cardiac rhythm.
• Administer sodium bicarbonate as ordered.
• Provide emotional support and education.

Complications

• pH < 7.0 can lead to life-threatening dysrhythmias.
• In chronic renal failure, may develop renal bone disease or encephalopathy.

Metabolic Acidosis Symptoms

Neurological

• Headache, confusion, ↓ LOC, drowsiness → coma.

Respiratory (Compensation)

• Kussmaul respirations; deep, rapid breathing; blowing off CO₂.

Cardiovascular

• BP dysrhythmias; weak, thready pulse; ability to excrete acid or conserve base.

Neuromuscular

• Muscle weakness, muscle twitching, hyporeflexia.

Electrolytes

• Hyperkalemia (↑ K⁺) → cardiac risk.

GI Symptoms

• Nausea, vomiting, diarrhea, abdominal pain.

Metabolic Alkalosis

Definition

• Caused by an increased loss of acid or accumulation of base, leading to an elevated arterial pH.

Causes of Metabolic Alkalosis

• Accumulation of base: excess use of bicarbonate, lactate administration during dialysis, excess ingestion of antacids.
• Loss of acids: vomiting, nasogastric suctioning, hypokalemia, hypochloremia, potassium-wasting diuretics, hyperaldosteronism.

Clinical Manifestations

• Muscle twitching, cramps, tetany, dizziness, lethargy, weakness.
• Disorientation, convulsions, coma, nausea, vomiting, depressed respirations.

Treatment

• Discontinue potassium-wasting diuretics or NG suctioning if appropriate.
• Administer antiemetics to control vomiting.
• Use acetazolamide to increase bicarbonate excretion (if patient is not volume depleted or hypokalemic).
• Provide IV fluids and electrolyte replacement as needed.

Nursing Interventions

• Monitor respiratory, cardiac, and neurologic status.
• Monitor LOC and safety if disoriented.
• Administer IV fluids and electrolytes as ordered.
• Provide emotional support and education.

Complications

• If pH exceeds 7.55:
  • Cardiac dysrhythmias, coma, neuromuscular irritability, decreased perfusion.

Mixed Acid-Base Disorders

What Are Mixed Disorders?

• Occur when patients have more than one primary imbalance at the same time.

Definition:

• Two or more primary acid-base disorders occurring simultaneously in the same patient.

Key Point

• This is NOT compensation; these are separate, independent problems!

Clues to Suspect a Mixed Disorder:

1. pH is normal but both CO₂ and HCO₃ are abnormal → indicating two opposite disorders "canceling out."
2. pH is more abnormal than expected → two disorders pushing pH in the same direction.
3. Compensation seems "too much" or "too little."
   • Remember: the body NEVER overcompensates!

Common Examples

• Respiratory Acidosis + Metabolic Acidosis (e.g., cardiac arrest patient):
  • Respiratory: Not breathing = ↑ CO₂;
  • Metabolic: Poor perfusion → Lactic acid.
• Respiratory Alkalosis + Metabolic Alkalosis (e.g., anxious patient with NG suction):
  • Respiratory: Hyperventilating = ↓ CO₂;
  • Metabolic: Losing gastric acid = ↑ HCO₃⁻.

Recognizing Clinical Significance

• Mixed disorders are often more severe than single disorders.
• Require treatment of BOTH underlying causes.
• Common in ICU patients with multiple organ involvement.

ATI/NCLEX Tip

• If pH is normal but CO₂ AND HCO₃ are BOTH abnormal in opposite directions → think mixed disorder, not full compensation!

Electrolytes & Acid-Base Balance

Relation Between Electrolytes and Acid-Base Balance

• IF YOU DROP ACID, YOU GET HIGH (ACIDOSIS); IF ELECTROLYTES LOW, YOU GET ALKALOSIS!

Acidosis (Too Much Acid)

• ↑ Hydrogen ions (H⁺) = ↓ pH.
• Often associated with:
  • Hyperkalemia (↑ K⁺)
  • Hyperchloremia (↑ Cl⁻)
• Why?: In acidosis, H⁺ moves into cells → K⁺ shifts out of cells → ↑ serum K⁺.

Conditions linked with Acidosis

• Seen in: DKA, renal failure, diarrhea (loss of base).

Alkalosis (Too Little Acid / Too Much Base)

• ↓ Hydrogen ions (H⁺) = ↑ pH.
• Often associated with:
  • Hypokalemia (↓ K⁺)
  • Hypochloremia (↓ Cl⁻)
• Why?: Low H⁺ causes K⁺ to shift into cells → ↓ serum K⁺.

Conditions linked with Alkalosis

• Seen in: vomiting, diuretic use, excess antacid ingestion.

Causes of Acidosis

↓ pH < 7.35

• Respiratory Acidosis: Hypoventilation → CO₂ retention → ↓ pH.

  • Causes include drug/opioid overdose, COPD/emphysema, airway obstruction, pneumonia, neuromuscular disease, CNS depression.

• Metabolic Acidosis: HCO₃ or acid → ↓ pH.

  • Causes include diabetic ketoacidosis, renal failure, shock/lactic acidosis, severe diarrhea, starvation, salicylate overdose.

Causes of Alkalosis

↑ pH > 7.45

• Respiratory Alkalosis: Hyperventilation → CO₂ loss → ↑ pH.

  • Causes include anxiety/panic attack, pain/fear, fever, pulmonary embolism, high altitude, pregnancy, hypoxia, over-ventilation.

• Metabolic Alkalosis: Excess HCO₃ or acid loss → ↑ pH.

  • Causes include vomiting/NG suctioning, excess NaHCO₃, hypokalemia, antacid overuse, diuretics (K+ wasting), hyperaldosteronism.

Acid–Base Balance Questions

Example Questions

1. A patient presents with pH 7.30, PaCO₂ 52 mmHg, and HCO₃⁻ 24 mEq/L. What is the correct acid-base imbalance?
   A. Metabolic Alkalosis
   B. Respiratory Acidosis
   C. Metabolic Acidosis
   D. Respiratory Alkalosis

2. A nurse is caring for a client with excessive vomiting and nasogastric suctioning. Which acid-base imbalance is most likely?
   A. Metabolic Acidosis
   B. Metabolic Alkalosis
   C. Respiratory Acidosis
   D. Respiratory Alkalosis

3. ABG values: pH 7.48, PaCO₂ 30 mmHg, HCO₃⁻ 22 mEq/L. What is the interpretation?
   A. Respiratory Alkalosis
   B. Metabolic Alkalosis
   C. Respiratory Acidosis
   D. Metabolic Acidosis

4. A patient is having Kussmaul respirations, dry mucous membranes, and a fruity breath odor. What acid-base imbalance is most likely?
   A. Respiratory Alkalosis
   B. Respiratory Acidosis
   C. Metabolic Alkalosis
   D. Metabolic Acidosis

5. Which patient is at highest risk for developing respiratory alkalosis?
   A. COPD patient retaining CO₂
   B. Post-operative patient using PCA pump
   C. Teenager having a panic attack
   D. Elderly patient with heart failure

6. ABG results: pH 7.33, PaCO₂ 38 mmHg, HCO₃⁻ 18 mEq/L. What condition is indicated?
   A. Metabolic Acidosis
   B. Respiratory Acidosis
   C. Metabolic Alkalosis
   D. Respiratory Alkalosis

7. Which of the following symptoms is most consistent with metabolic alkalosis?
   A. Warm, flushed skin
   B. Tetany and muscle cramps
   C. Kussmaul respirations
   D. Confusion and stupor

8. A nurse receives an ABG report showing: pH 7.50, PaCO₂ 45 mmHg, HCO₃⁻ 30 mEq/L. What is the interpretation?
   A. Metabolic Alkalosis
   B. Respiratory Acidosis
   C. Respiratory Alkalosis
   D. Metabolic Acidosis

9. Which of the following lab findings would be expected in metabolic acidosis?
   A. PaCO₂ 50 mmHg
   B. HCO₃⁻ 18 mEq/L
   C. pH 7.50
   D. HCO₃⁻ 30 mEq/L

10. What clinical manifestation is associated with respiratory acidosis?
    A. Deep, rapid breathing
    B. Light-headedness
    C. Hypoventilation
    D. Tetany

11. ABG report: pH 7.28, PaCO₂ 49 mmHg, HCO₃⁻ 25 mEq/L. What is the acid-base disorder?
    A. Respiratory Alkalosis
    B. Metabolic Acidosis
    C. Respiratory Acidosis
    D. Metabolic Alkalosis

12. Which condition most likely leads to metabolic acidosis?
    A. Prolonged vomiting
    B. Diuretic overuse
    C. Starvation and lactic acidosis
    D. Hyperventilation due to anxiety

13. Which electrolyte disturbance is commonly seen with metabolic alkalosis?
    A. Hyperkalemia
    B. Hypermagnesemia
    C. Hypokalemia
    D. Hypercalcemia

14. What is the appropriate treatment for a patient with metabolic alkalosis due to excessive diuretic use?
    A. Administer IV sodium bicarbonate
    B. Provide potassium replacement
    C. Begin hyperventilation techniques
    D. Administer insulin

15. A patient presents with the following ABGs: pH 7.45, PaCO₂ 33 mmHg, HCO₃⁻ 22 mEq/L. What is the correct interpretation?
    A. Normal acid-base status
    B. Metabolic Alkalosis
    C. Respiratory Alkalosis
    D. Compensated Metabolic Acidosis

16. A patient with chronic renal failure has ABG results: pH 7.35, PaCO₂ 30 mmHg, HCO₃⁻ 16 mEq/L. The nurse interprets this as:
    A. Uncompensated metabolic acidosis
    B. Partially compensated metabolic acidosis
    C. Fully compensated metabolic acidosis
    D. Uncompensated respiratory alkalosis

17. Which patient would the nurse expect to develop respiratory compensation first?
    A. A patient who just started on a thiazide diuretic
    B. A patient with acute diabetic ketoacidosis
    C. A patient with a 3-day history of vomiting
    D. A patient with chronic kidney disease

18. A patient's ABG shows: pH 7.50, PaCO₂ 48 mmHg, HCO₃⁻ 36 mEq/L. Which statement by the student nurse indicates correct understanding?
    A. "This is uncompensated metabolic alkalosis."
    B. "The lungs are retaining CO₂ to lower the pH."
    C. "The kidneys have not yet begun to compensate."
    D. "This patient needs to breathe faster."

19. The nurse is reviewing ABGs for a patient on a mechanical ventilator. Which finding suggests the patient is being over-ventilated?
    A. pH 7.32, PaCO₂ 52, HCO₃⁻ 26
    B. pH 7.48, PaCO₂ 28, HCO₃⁻ 22
    C. pH 7.38, PaCO₂ 42, HCO₃⁻ 24
    D. pH 7.40, PaCO₂ 40, HCO₃⁻ 24

20. A patient admitted 3 days ago with pneumonia now has ABGs: pH 7.36, PaCO₂ 58 mmHg, HCO₃⁻ 32 mEq/L. What does this indicate?
    A. The patient is getting worse.
    B. The kidneys have compensated for the respiratory acidosis.
    C. The patient has developed metabolic alkalosis.
    D. No compensation has occurred.

21. Why can't the lungs fully compensate for severe metabolic acidosis?
    A. The lungs respond too slowly
    B. The lungs can be overwhelmed and have limited capacity
    C. The lungs can only excrete bicarbonate
    D. The lungs are not involved in acid-base balance

22. A patient has pH 7.30, PaCO₂ 25 mmHg, HCO₃⁻ 12 mEq/L. The primary problem is:
    A. Respiratory acidosis
    B. Respiratory alkalosis
    C. Metabolic acidosis
    D. Metabolic alkalosis

23. Which clinical scenario represents appropriate renal compensation?
    A. COPD patient with HCO₃⁻ of 32 mEq/L
    B. Anxiety patient with HCO₃⁻ of 30 mEq/L
    C. DKA patient with PaCO₂ of 20 mmHg
    D. Vomiting patient with PaCO₂ of 48 mmHg

24. A nurse is teaching about compensation. Which statement is correct?
    A. "Full compensation means all ABG values return to normal."
    B. "The body never overcompensates beyond normal pH."
    C. "Respiratory compensation is more powerful than renal."
    D. "Compensation occurs only in chronic conditions."

25. ABG results show: pH 7.42, PaCO₂ 32 mmHg, HCO₃⁻ 20 mEq/L. The nurse identifies this as fully compensated respiratory alkalosis. How can the nurse determine the primary disorder?
    A. The pH is closer to alkalotic (above 7.40)
    B. The PaCO₂ is more abnormal than HCO₃⁻
    C. Respiratory problems always come first
    D. The HCO₃⁻ is within normal limits

NCLEX & ATI Key Takeaways

• ABG Interpretation Steps:
  1. Check pH first: acidosis or alkalosis?
  2. Match the abnormal value to the pH.
  3. Check for compensation (both values off?).
• Compensation Rules:
  • Lungs = fast (seconds-minutes), limited capacity.
  • Kidneys = slow (24-48 hours), powerful.
  • Opposite system always compensates. The body never overcompensates past normal pH.

Critical Nursing Priorities

• Acidosis: Assess cardiovascular system first. Hyperkalemia = cardiac arrest risk.
• Alkalosis: Implement fall precautions. Hypokalemia = muscle weakness.

High-Yield Test Points

• pH below 6.9 or above 7.8 = usually fatal.
• Normal pH = 7.35 to 7.45.
• Kussmaul breathing = DKA.
• Compensation in COPD = chronic elevated CO₂ with elevated HCO₃⁻.