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concept_blood_gas_analysis [2025/05/13 06:22] – [What is the Bicarbonate (HCO₃⁻)?] jkohtsconcept_blood_gas_analysis [2025/05/13 06:36] (current) – [1.4 Is there any compensation?] jkohts
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-==== Is there any compensation? ====+==== - Is there any compensation? ====
 Both the lungs and kidneys adapt to compensate for acid-base disturbances in an attempt to bring the pH closer to normal. The adequacy of this compensation should be assessed. Both the lungs and kidneys adapt to compensate for acid-base disturbances in an attempt to bring the pH closer to normal. The adequacy of this compensation should be assessed.
  
-**Respiratory compensation**\\ +=== Respiratory Compensation === 
-A quick rule is that the pCO2 should roughly equal the last two digits of the pH value. This only works within a pH range of 7.1-7.6.+A quick rule is that the PCO₂ should roughly equal the last two digits of the pH value. This only works within a pH range of 7.1-7.6.
  
 A better rule is that: A better rule is that:
 +  * In metabolic acidosis, expected PCO₂ = 1.5 [HCO₃⁻] + 8
 +  * In metabolic alkalosis, expected PCO₂ = 0.7 [HCO₃⁻] + 20
  
-  * in metabolic acidosis, pCO2 = 1.5 [HCO3] + 8 
-  * in metabolic alkalosis, pCO2 = 0.7 [HCO3] + 20 
  
-**Metabolic compensation**\\ +=== Metabolic Compensation === 
-Renal metabolic compensation occurs quickly via intracellular buffering, and more slowly via the kidney, where under normal conditions, HCO3 is absorbed and H+ is secreted in varying amounts.+Renal metabolic compensation occurs quickly via intracellular buffering, and more slowly via the kidney, where under normal conditions, HCO₃⁻ is absorbed and H⁺ is secreted in varying amounts.
  
 The following rules can determine the adequacy of metabolic derangement: The following rules can determine the adequacy of metabolic derangement:
  
-In respiratory acidosis+In respiratory acidosis: 
 +  * Acutely, for every rise in 10 mmHg of PCO₂ the HCO₃⁻ rises by 1 mmol/L 
 +  * Chronically, for every rise in 10 mmHg of PCO₂ the HCO₃⁻ rises by 4 mmol/L
  
-  * Acutely, for every rise in 10mmHg of pCO2 the HCO3 rises by 1mmol/L +In respiratory alkalosis: 
-  * Chronically, for every rise in 10mmHg of CO2 the HCO3 rises by 4mmol/L +  * Acutely, for every fall in 10 mmHg of PCO₂ the HCO₃⁻ falls by 2 mmol/L 
- +  * Chronically, for every fall in 10mmHg of PCO₂ the HCO₃⁻ falls by 5 mmol/L
-In respiratory alkalosis +
- +
-  * Acutely, for every fall in 10 mmHg of CO2 the HCO3 falls by 2 mmol/L +
-  * Chronically, for every fall in 10mmHg of CO2 the HCO3 falls by 5 mmol/L+
  
  
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 ===== - Other Useful Information on a Blood Gas ===== ===== - Other Useful Information on a Blood Gas =====
  
-  * pO2 denotes oxygenation of the blood, a pO2 < 60mmHg is concerning for hypoxia.+  * PO₂ denotes oxygenation of the blood, a PO₂ < 60mmHg is concerning for hypoxia.
   * Lactate is often quantified, with normal concentrations < 2mmol/L.   * Lactate is often quantified, with normal concentrations < 2mmol/L.
-  * Electrolytes such as sodium (Na+), potassium (K+) and chloride (Cl-) are usually reported on a blood gas+  * Electrolytes such as sodium (Na⁺), potassium (K⁺) and chloride (Cl⁻) are usually reported on a blood gas
   * COHb quantifies the percentage of circulating carboxyhaemoglobin. Smoking can be associated with levels up to 10%.   * COHb quantifies the percentage of circulating carboxyhaemoglobin. Smoking can be associated with levels up to 10%.
   * MetHb quantifies the percentage of circulating methaemoglobin.   * MetHb quantifies the percentage of circulating methaemoglobin.