Sandbox: sadaf
Acid Base Disorders
Blood Gas Analysis
Blood gas analysis | Vessel | Range | Interpretation |
---|---|---|---|
Oxygen Partial Pressure (pO2) | Arterial | 80 to 100 mmHg | Normal |
<80 mmHg | Hypoxia | ||
Venous | 35 to 40 mmHg | Normal | |
Oxygen Saturation (SO2) | Arterial | >95% | Normal |
<95% | Hypoxia | ||
Venous | 70 to 75% | Normal | |
pH | Arterial | <7.35 | Acidemia |
7.35 to 7.45 | Normal | ||
>7.45 | Alkalemia | ||
Venous | 7.26 to 7.46 | Normal | |
Carbon Dioxide Partial Pressure (pCO2) | Arterial | <35 mmHg | Low |
35 to 45 mmHg | Normal | ||
>45 mmHg | High | ||
Venous | 40 to 45 mmHg | Normal | |
Bicarbonate (HCO3−) | Arterial | <22 mmol/L | Low |
22 to 26 mmol/L | Normal | ||
>26 mmol/L | High | ||
Venous | 19 to 28 mmol/L | Normal | |
Base Excess (BE) | Arterial | <−3.4 | Acidemia |
−3.4 to +2.3 mmol/L | Normal | ||
>2.3 | Alkalemia | ||
Venous | −2 to −5 mmol/L | Normal | |
Osmolar gap
(Osmolality – Osmolarity) |
>10 | Abnormal | |
Anion gap
[Na+] – {[Cl−]+[HCO3−]} |
<8 | Low | |
8 to 16 | Normal | ||
>16 | High |
Compensation
Primary disorder | pH | PaCO2 | [HCO3-] | Compensation | Compensation formula |
---|---|---|---|---|---|
Metabolic acidosis | ↓ | ↓ | ↓ | Respiratory |
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Metabolic alkalosis | ↑ | ↑ | ↑ | Respiratory |
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Respiratory acidosis | ↓ | ↑ | ↑ | Renal | |
Respiratory alkalosis | ↑ | ↓ | ↓ | Renal |
Approach to acid–base disorders
Check pH on ABG | |||||||||||||||||||||||||||||||||||||||||
pH < 7.35= Acidosis | pH > 7.45= Alkalosis | ||||||||||||||||||||||||||||||||||||||||
Check PaCO2 | |||||||||||||||||||||||||||||||||||||||||
PaCO2 > 45mm Hg = Respiratory acidosis | PaCO2 Normal or < 35mm Hg = Metabolic acidosis | Check PaCO2 | |||||||||||||||||||||||||||||||||||||||
PaCO2 > 45mm Hg = Metabolic alkalosis | PaCO2 < 35mm Hg = Respiratory alkalosis | ||||||||||||||||||||||||||||||||||||||||
[HCO3-] > 29 | Check [HCO3-] | ||||||||||||||||||||||||||||||||||||||||
Normal or slight decrease = Acute respiratory alkalosis | Decreased < 24 = Chronic respiratory alkalosis | ||||||||||||||||||||||||||||||||||||||||
Management of Acidosis
pH < 7.35 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Acidosis | |||||||||||||||||||||||||||||||||||||||||||||||||||
Determine the primary disorder Metabolic or respiratory? | |||||||||||||||||||||||||||||||||||||||||||||||||||
Check [HCO3-] and PaCO2 | |||||||||||||||||||||||||||||||||||||||||||||||||||
Low [HCO3-] and Low to normal PaCO2 | High PaCO2 and High to normal [HCO3-] | ||||||||||||||||||||||||||||||||||||||||||||||||||
Metabolic acidosis | Respiratory acidosis | ||||||||||||||||||||||||||||||||||||||||||||||||||
Check for respiratory compensation Calculate expected PCO2 | Check for renal compensation Calculate expected [HCO3-] | ||||||||||||||||||||||||||||||||||||||||||||||||||
Decrease in PaCO2=1.25 x (24- measured HCO3-)? | Acute acidosis? Increase [HCO3-]=0.1 x (measure PaCO2-40)? | Chronic acidosis? Increase [HCO3-]=0.1 x (measure PaCO2-40)? | |||||||||||||||||||||||||||||||||||||||||||||||||
PaCO2 too low? Mixed metabolic acidosis with respiratory alkalosis | PaCO2 too high? Mixed metabolic acidosis with respiratory acidosis | [HCO3-] too low? Mixed respiratory acidosis with metabolic acidosis | [HCO3-] too high? Mixed respiratory acidosis with metabolic alkalosis | [HCO3-] too low? Mixed respiratory acidosis with metabolic acidosis | E04=[HCO3-] too high? Mixed respiratory acidosis with metabolic alkalosis | ||||||||||||||||||||||||||||||||||||||||||||||
Measured PaCO2 is equal to expected value? Compensated metabolic acidosis | Measured [HCO3-] is equal to expected value? Compensated respiratory acidosis | Measured [HCO3-] is equal to expected value? Compensated respiratory acidosis | |||||||||||||||||||||||||||||||||||||||||||||||||
Click here for the management of metabolic acidosis | Click here for the management of respiratory acidosis | ||||||||||||||||||||||||||||||||||||||||||||||||||
Metabolic Acidosis
Category | Disease | Mechanism | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
↑ acid production |
Loss of bicarbonate |
↓ renal acid excretion |
pH | Serum AG | Urine AG | Serum Cl | Volume depletion | HTN | |||||||
Toxin/Medication | Alcohol
|
+ | ↓ | ↑ | |||||||||||
Paraldehyde | ↓ | ↑ | |||||||||||||
Toluene | + | ↓ | Nl or ↑ | ||||||||||||
Pyroglutamic acid
(5-oxoproline) |
+ | ↓ | ↑ | ||||||||||||
Salicylates | ↓↑ | ↑ | |||||||||||||
Metformin | ↓ | ↑ | |||||||||||||
Isoniazid | ↓ | ↑ | |||||||||||||
Acetazolamide | + | ↓ | Nl | ||||||||||||
Ammonium chloride | ↓ | Nl | |||||||||||||
Amphotericin B | ↓ | Nl | |||||||||||||
Cholestyramine | ↓ | Nl | |||||||||||||
Lactic acidosis | + | ↓ | ↑ | ||||||||||||
Ketoacidosis | Diabetic | + | ↓ | ↑ | |||||||||||
Starvation | + | ↓ | ↑ | ||||||||||||
Alcoholic | + | ↓ | ↑ | ||||||||||||
Systemic | Infection | ↓ | ↑ | ||||||||||||
Ischemia | ↓ | ↑ | |||||||||||||
Renal | Uremia | ↓ | ↑ | ||||||||||||
Ureteral diversion | + | ↓ | Nl | ||||||||||||
Renal failure | + | ↓ | ↑ | ||||||||||||
Renal tubular acidosis | Type I | + | ↓ | Nl | ↑ | ||||||||||
Type II | + | ↓ | Nl | ↓ | |||||||||||
Type IV | + | ↓ | Nl | ↑ | |||||||||||
GI | Diarrhea | + | ↓ | Nl | |||||||||||
Hyperalimentation | ↓ | Nl | |||||||||||||
Endocrine | Addison's disease | ↓ | Nl | ||||||||||||
Post hypocapnea | ↓ | Nl | |||||||||||||
Category | Disease | pH | Serum AG | Urine AG | Volume depletion | HTN |
Metabolic Alkalosis
Category | Disease | pH | Renin | Urine chloride | Volume depletion | HTN | ||||
---|---|---|---|---|---|---|---|---|---|---|
Exogenous HCO3− loads | Acute alkali administration | ↑ | ||||||||
Milk-alkali syndrome | ↑ | |||||||||
Gastrointestinal origin | Vomiting | ↑ | ↓ | + | ||||||
Nasogastric tube suction | ↑ | ↓ | + | |||||||
Gastric aspiration | ||||||||||
Congenital chloridorrhea | ||||||||||
Villous adenoma | ||||||||||
Renal origin | Diuretics | ↑ | ↓ | + | ||||||
Posthypercapnic state | ||||||||||
Hypercalcemia/hypoparathyroidism | ||||||||||
Recovery from lactic acidosis or ketoacidosis | ||||||||||
Nonreabsorbable anions including penicillin, carbenicillin | ||||||||||
Hypomagnesemia | ↑ | Nl | - | |||||||
Hypokalemia | ↑ | Nl | - | |||||||
Bartter's syndrome | ↑ | Nl | - | |||||||
Gitelman’s syndrome | ||||||||||
Renal artery stenosis | ↑ | ↑ | Nl | + | ||||||
Cushing's syndrome | ↑ | ↓ | Nl | + | ||||||
Hyperaldosteronism | ↑ | ↓ | Nl | + | ||||||
Licorice ingestion | ↑ | ↓ | Nl | - | ||||||
Category | Disease | pH | Renin | Urine chloride | Volume depletion | HTN |
Mixed Acid-Base Disorders
Disorder | Key features | Examples |
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Metabolic acidosis & respiratory alkalosis |
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Metabolic acidosis & respiratory acidosis |
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Metabolic alkalosis & respiratory alkalosis |
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Metabolic alkalosis & respiratory acidosis |
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Metabolic acidosis & metabolic alkalosis |
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Metabolic acidosis & metabolic acidosis |
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