| Type | Definition & Laboratory Values | Pathophysiology | Key Clinical Features |
|---|---|---|---|
| Respiratory Alkalosis |
pH >7.45 PaCO₂ <35 mm Hg HCO₃⁻ normal (uncompensated) HCO₃⁻ <22 mEq/L (compensated) |
• Hyperventilation → ↑ CO₂ excretion • Compensatory ↑ HCO₃⁻ excretion by kidneys • Left shift in oxyhemoglobin curve |
• Dizziness, light-headedness • Paresthesias, tetany • Hyperventilation • Anxiety, confusion |
| Metabolic Alkalosis |
pH >7.45 HCO₃⁻ >26 mEq/L PaCO₂ normal (uncompensated) PaCO₂ >45 mm Hg (compensated) |
• Loss of H⁺ or gain of HCO₃⁻ • Compensatory ↑ CO₂ retention by lungs • Often associated with volume depletion |
• Hypoventilation (compensatory) • Muscle cramps, weakness • Hypokalemia effects • Possible arrhythmias |
Alkalosis: Pathophysiology and Clinical Manifestations
Acidosis: Pathophysiology and Clinical Manifestations
| Type | Definition & Laboratory Values | Pathophysiology | Key Clinical Features |
|---|---|---|---|
| Respiratory Acidosis |
pH <7.35 PaCO₂ >45 mm Hg HCO₃⁻ normal (uncompensated) HCO₃⁻ >26 mEq/L (compensated) |
• Hypoventilation → ↑ CO₂ retention • Compensatory ↑ HCO₃⁻ retention by kidneys • Cerebral vasodilation |
• Altered mental status • Headache, confusion • Warm, flushed skin • Possible papilledema |
| Metabolic Acidosis |
pH <7.35 HCO₃⁻ <22 mEq/L PaCO₂ normal (uncompensated) PaCO₂ <35 mm Hg (compensated) |
• ↑ acid production or ↓ acid excretion • Loss of HCO₃⁻ • Compensatory ↑ CO₂ excretion by lungs |
• Kussmaul respirations • Nausea, vomiting • Weakness, fatigue • Possible shock |
Etiologies and Differential Diagnosis
Alkalosis Causes
Respiratory Alkalosis
- Anxiety, panic disorders
- Pain, fever
- Hypoxia (high altitude, pulmonary disease)
- CNS disorders (stroke, trauma)
- Drugs (salicylates, beta-agonists)
- Mechanical hyperventilation
- Pregnancy
- Hyperthyroidism
Metabolic Alkalosis
- Vomiting, nasogastric suction
- Diuretic therapy
- Hyperaldosteronism
- Hypokalemia
- Milk-alkali syndrome
- Bartter/Gitelman syndrome
- Cushing syndrome
Acidosis Causes
Respiratory Acidosis
- COPD exacerbation
- Severe pneumonia, asthma
- CNS depression (opioids, sedatives)
- Neuromuscular disorders
- Chest wall abnormalities
- Airway obstruction
- Respiratory muscle fatigue
Metabolic Acidosis
- Diabetic ketoacidosis
- Lactic acidosis
- Renal failure (uremia)
- Diarrhea
- Toxins (methanol, ethylene glycol)
- Salicylate poisoning
- Renal tubular acidosis
Clinical Memory Aid: MUDPILES for Anion Gap Metabolic Acidosis
M - Methanol, Metformin
U - Uremia
D - Diabetic ketoacidosis
P - Paraldehyde
I - Iron, Isoniazid
L - Lactic acidosis
E - Ethylene glycol
S - Salicylates
U - Uremia
D - Diabetic ketoacidosis
P - Paraldehyde
I - Iron, Isoniazid
L - Lactic acidosis
E - Ethylene glycol
S - Salicylates
Psychiatric and Psychological Considerations
Anxiety-Related Alkalosis
Panic Disorder
- Hyperventilation syndrome
- Acute respiratory alkalosis
- Paresthesias, tetany
- Dizziness, syncope
Assessment Considerations
- Rule out medical causes first
- Consider chronic hyperventilation
- Evaluate medication effects
- Screen for substance use
Medication-Induced Disorders
Psychotropic Medications
- Salicylate toxicity (alkalosis initially)
- Antipsychotic-induced rigidity
- Lithium nephrotoxicity
- Acetazolamide (metabolic acidosis)
CNS Depressants
- Benzodiazepine overdose
- Opioid-induced hypoventilation
- Barbiturate intoxication
- Alcohol withdrawal effects
Behavioral Factors
Eating Disorders
- Vomiting → metabolic alkalosis
- Laxative abuse → acidosis
- Starvation ketosis → acidosis
- Electrolyte imbalances
Substance Use
- Methanol, ethylene glycol
- Chronic alcohol use
- Toxic ingestions
- Drug interactions
Emergency Assessment and Management Priorities
| Condition | Critical Values | Immediate Actions | Monitoring Parameters |
|---|---|---|---|
| Severe Alkalosis |
pH >7.55 Severe hypokalemia Hypocalcemia |
• Treat underlying cause • Correct electrolytes (K⁺, Mg²⁺) • Control hyperventilation • Consider acetazolamide |
• Cardiac rhythm • Neurological status • Electrolytes q4-6h • Serial ABGs |
| Severe Acidosis |
pH <7.20 HCO₃⁻ <10 mEq/L Hyperkalemia |
• Ensure adequate ventilation • Treat underlying cause • Consider bicarbonate (pH <7.10) • Hemodialysis if indicated |
• Hemodynamic status • Respiratory effort • Potassium levels • Mental status |
Emergency Warning Signs: Severe acid-base disorders (pH <7.20 or >7.55) require immediate intervention. In psychiatric settings, always consider toxic ingestions, medication effects, and metabolic complications of psychiatric conditions. Chronic psychiatric patients may have altered pain perception and atypical presentations.
Clinical Pearl: Acid-base disorders in psychiatric patients often reflect complex interactions between mental health conditions, medications, and behavioral factors. Systematic evaluation prevents misattribution of symptoms to psychiatric causes alone (Sur & Hashmi, 2024).