Introduction The kidneys play an important role in regulating the body's acid-base status via HCO3− reabsorption this is the major extracellular buffer and is thus why it is important to conserve HCO3− login to view 2 more bullets Na+H+ exchanger secretes H+ into the tubular lumen and combines with filtered HCO3− to form H2CO3 login to view 19 more bullets H+ excretion H+ excretion is accompanied by new HCO3− synthesis and reabsorption there are two mechanisms involved login to view 14 more bullets Acid-Base Disorders Acidosis results in acidemia due to an increased serum H+ (decreased pH) Alkalosis results in alkalemia due to a decreased serum H+ (increased pH) These acid base disorders may be due to primary disturbances in HCO3− (metabolic) or arterial CO2 (PCO2) (respiratory) the Hendersen-Hasselbalch equation shows that changes in HCO3− or PCO2 changes pH pH = pKa + log ([HCO3-]/(0.03 * PCO2) Metabolic acidosis due to a decrease in HCO3− either because of increased H+ or loss of HCO3− Metabolic alkalosis due to an increase in HCO3− Respiratory acidosis due to an increase in CO2 secondary to hypoventilation (which retains CO2) Respiratory alkalosis due to a decrease in CO2 secondary to hyperventilation Winter's formula determines expected respiratory compensation in response to metabolic acidosis PCO2 = 1.5 (HCO3-) + 8 +/- 2 if actual PCO2 is greater than expected PCO2 → also has a primary respiratory acidosis if actual PCO2 is less than expected PCO2 → also has a primary respiratory alkalosis Acid-Base Disorders Acid-Base Disorder pH PCO2 [HCO3-] Compensatory Response Metabolic acidosis ↓ ↓ ↓ (primary disturbance) Hyperventilation Metabolic alkalosis ↑ ↑ ↑ (primary disturbance) Hypoventilation Respiratory acidosis ↓ ↑ (primary disturbance) ↑ ↑ renal HCO3- reabsorption Respiratory alkalosis ↑ ↓ (primary disturbance) ↓ ↓ renal HCO3- reabsorption