Acid-Base Balance

Acid–Base Balance

Acid–Base Balance

• Homeostasis: The body keeps internal conditions stable and balanced.

  • Normal human blood pH: 7.35–7.45

  • Extracellular fluid (ECF) pH is maintained through

  • 3 systems:

    1. Buffer system

    2. Respiratory system

    3. Renal system

Acid–Base Defense Systems

Acid–Base Defense Systems

1) Buffer System — Fastest

• Works immediately

• Bicarbonate binds extra H⁺ (acid)

• Temporary fix

• Can become overwhelmed

2) Respiratory System — Second Fastest

• Lungs remove CO₂

• More CO₂ = more acidic

• Faster/deeper breathing → removes more CO₂ → raises blood pH

3) Renal System — Slowest

• Kidneys control H⁺ (acid) and bicarbonate (HCO₃⁻)

• If blood is too acidic:

  • Remove H⁺

  • Keep bicarbonate

• If blood is too alkaline:

  • Remove bicarbonate

  • Keep H⁺

Order: Buffer → Lungs → Kidneys

System Failure

System Failure: If the acid–base systems are interrupted or cannot keep up, acidotic states can result.

• 2 Types: Metabolic Acidosis & Respiratory Acidosis

Respiratory Acidosis

Respiratory Acidosis: Lungs fail to remove enough CO₂, causing CO₂ to build up in the blood.

↑ CO₂ → ↑ acid → ↓ blood pH

Main problem: Poor ventilation or poor CO₂ exchange in the alveoli.

Common Causes

1. Respiratory depression / stopped breathing

   • Anesthesia

   • Drug overdose

   • Increased intracranial pressure

   • Stroke or CNS trauma

   • Inadequate artificial ventilation

   • Severe obesity

2. Airway obstruction

3. COPD

4. Asthma → airway condition

5. Pneumonia → lung infection

6. Pulmonary embolism → blood clot in lungs

Signs & Symptoms

1. Rapid, shallow breathing or hypoventilation

2. Decreased level of consciousness (LOC)

3. Pale skin or cyanosis

4. Increased ETCO₂

5. Hypotension

6. Shortness of breath

7. Wheezing

8. Headache

Metabolic Acidosis

Metabolic Acidosis: Blood becomes too acidic because there is:

• Too little bicarbonate (HCO₃⁻), OR

• Too much metabolic acid

Common Causes

1. Renal failure → kidneys cannot remove enough acid

2. DKA (diabetic ketoacidosis) → ketones build up

3. Diarrhea → loss of bicarbonate

4. Severe dehydration or liver failure

Signs & Symptoms

1. Headache

2. Warm, flushed skin

3. Nausea/vomiting

4. Decreased LOC

5. Poor coordination

6. Kussmaul respirations → deep, rapid breathing

Alkalosis

Alkalosis: When blood is not acidic enough.

• 2 Types: Metabolic Alkalosis & Respiratory Alkalosis

Respiratory Alkalosis

Respiratory Alkalosis: Blowing off too much CO₂ from breathing too fast/deep.

Common Causes

1. Hyperventilation

2. Anxiety/fear

3. Mechanical ventilation

4. Pulmonary embolism

Signs & Symptoms

1. Deep, rapid breathing

2. Numbness/tingling in hands & feet

3. Nausea/vomiting

4. Altered LOC

5. Seizures

6. BP may be normal or low

Metabolic Alkalosis

Metabolic Alkalosis: Too much HCO₃⁻ (bicarbonate) or loss of acid in the body.

Common Causes

1. Repeated vomiting

2. Diuretics

3. NG suction

4. Too much bicarbonate administration

Signs & Symptoms

1. Tachycardia → fast heart rate

2. Slow breathing (hypoventilation)

3. Altered LOC

4. Nausea/vomiting

5. Diarrhea

6. Tremors/muscle cramps

BLS Interventions (Basic Life Support Interventions)

BLS Interventions (Basic Life Support Interventions): Support ABCs, treat life threats, and get ALS/medical help.

Airway

• Keep airway open

• Especially important with altered LOC

Breathing

• Supplemental oxygen if needed

• Assisted ventilation if patient is not breathing adequately

  • IMPORTANT: Kussmaul breathing is compensatory hyperventilation that blows off CO₂. Do not unnecessarily slow or interrupt it.

Circulation

• Check perfusion:

  • Pulse

  • Skin

  • BP

  • Mental status

  • Capillary refill, as appropriate

Assessment & Treatment

Assessment & Treatment

1. Get baseline vitals

2. Perform physical exam & identify signs/symptoms

3. Obtain SAMPLE history or OPQRST

4. Look for causes such as:

   • DKA

   • Vomiting

   • Diarrhea

   • Respiratory problems

   • Kidney problems

   • Overdose

5. Treat the underlying problem/chief complaint

6. Be careful with medical/assisted ventilation

   • Used incorrectly, it can worsen the condition

7. Request ALS/medical assistance if needed