, Acid-Base
pH
➔ Normal = 7.35-7.45
➔ <6.9 or >7.8 is fatal blood gas
➔ Measures the acidity or alkalinity of a solution
➔ Large # of H ions = decreased pH (acidosis) <7.35
➔ Small # of H ions = increased pH (alkalosis) >7.45
➔ Acid = compound that allows hydrogen ions to break free (decrease pH)
➔ Base = compound that binds w/ hydrogen ions (increase pH)
Body cells will produce hydrogen ions and distribute them into ECF (interstitial & intravascular), then turn into acids. A base needs to bond with the acids
(buffer them) or blow out CO2 / pee it out
➔ Chemical Buffer Systems keep pH relatively constant
➔ Carbonic Acid - Bicarbonate Buffer System
➔ Phosphate Buffer System
➔ Protein Buffer System
Regulation → Carbonic Acid - Bicarbonate Buffer System
★ System that we monitor clinically
★ Whatever system is damaged, the opposite system has to compensate ❗️
○ Ex. COPD means too much CO2 trapped, so renal system has to compensate for that by reabsorbing bicarb to bind w/ that acid (H
ions) in order to keep pH normal… kidneys could also excrete excess H ions via urine.
★ Goals: control amt of hydrogen ions we have, to have buffers to either hold onto the hydrogen ions or let go to keep pH normal
★ Carbonic acid (acid) = H2CO3 (CO2 & H2O)
○ We don’t look at carbonic acid because we don’t need to measure the water content. We only need to measure CO2.
○ Direct reflection of CO2 → the more CO2 builds up, the more carbonic acid that is created
○ Trapped CO2 is COPD → makes blood acidotic (pH drops)
○ It is a respiratory acidosis/alkalosis
★ Bicarbonate (common base) = HCO3
○ Goal is to bind to those H ions, keeping those H ions from floating freely and making us acidotic
★ Respiratory control (CO2 changes) happens in seconds to minutes
○ pH acidic (<7.35) = RR & depth increases (hyperventilation blows off CO2 in blood)
○ pH alkaline (>7.45) = RR & depth decreases (hypoventilation tries to hold onto CO2 to balance out the bicarb)
★ Renal regulation (Metabolic HCO3 changes) makes changes in several hours to days
○ pH acidic (<7.35) = H+ ions excreted in urine
○ pH alkaline (>7.45) = HCO3 excreted in urine
○ Kidneys make, reabsorb, or excrete base (bicarb) & acids as well
If you’re looking at an ABG & have identified that a pt has respiratory acidosis, you can tell whether it was an acute or chronic condition based on how
the kidneys responded. If bicarb is still a normal number, the kidneys haven’t done anything yet meaning its a new condition (acute). In COPD, kidneys
have had time to respond so the bicarb is abnormal.
Acid-Base Disturbances
★ Mixed acid base imbalance can happen at the same time
○ You can’t have respiratory acidosis and respiratory alkalosis because they are compensating each other.
○ Most common is mixed respiratory & metabolic acidosis, usually caused from cardiac arrest
○ Ex. if respiratory arrest occurs, CO2 builds (causes respiratory acidosis) + the patient is also not receiving O2, so cells start w/
anaerobic metabolism → lactic acid builds (causing a metabolic acidosis)
★ Acidosis = abnormal increase in hydrogen ion concentration
○ Accumulation of excess acid or loss of bicarbonate
○ First thing that happens is the acidosis, then the hyperkalemia (even if it is a chronic condition)
★ Alkalosis = abnormal decrease in hydrogen ions concentration
○ Accumulation of excess bicarbonate or loss of acid
○ First thing that happens is the alkalosis, then the hypokalemia (even if it is a chronic condition)
pH
➔ Normal = 7.35-7.45
➔ <6.9 or >7.8 is fatal blood gas
➔ Measures the acidity or alkalinity of a solution
➔ Large # of H ions = decreased pH (acidosis) <7.35
➔ Small # of H ions = increased pH (alkalosis) >7.45
➔ Acid = compound that allows hydrogen ions to break free (decrease pH)
➔ Base = compound that binds w/ hydrogen ions (increase pH)
Body cells will produce hydrogen ions and distribute them into ECF (interstitial & intravascular), then turn into acids. A base needs to bond with the acids
(buffer them) or blow out CO2 / pee it out
➔ Chemical Buffer Systems keep pH relatively constant
➔ Carbonic Acid - Bicarbonate Buffer System
➔ Phosphate Buffer System
➔ Protein Buffer System
Regulation → Carbonic Acid - Bicarbonate Buffer System
★ System that we monitor clinically
★ Whatever system is damaged, the opposite system has to compensate ❗️
○ Ex. COPD means too much CO2 trapped, so renal system has to compensate for that by reabsorbing bicarb to bind w/ that acid (H
ions) in order to keep pH normal… kidneys could also excrete excess H ions via urine.
★ Goals: control amt of hydrogen ions we have, to have buffers to either hold onto the hydrogen ions or let go to keep pH normal
★ Carbonic acid (acid) = H2CO3 (CO2 & H2O)
○ We don’t look at carbonic acid because we don’t need to measure the water content. We only need to measure CO2.
○ Direct reflection of CO2 → the more CO2 builds up, the more carbonic acid that is created
○ Trapped CO2 is COPD → makes blood acidotic (pH drops)
○ It is a respiratory acidosis/alkalosis
★ Bicarbonate (common base) = HCO3
○ Goal is to bind to those H ions, keeping those H ions from floating freely and making us acidotic
★ Respiratory control (CO2 changes) happens in seconds to minutes
○ pH acidic (<7.35) = RR & depth increases (hyperventilation blows off CO2 in blood)
○ pH alkaline (>7.45) = RR & depth decreases (hypoventilation tries to hold onto CO2 to balance out the bicarb)
★ Renal regulation (Metabolic HCO3 changes) makes changes in several hours to days
○ pH acidic (<7.35) = H+ ions excreted in urine
○ pH alkaline (>7.45) = HCO3 excreted in urine
○ Kidneys make, reabsorb, or excrete base (bicarb) & acids as well
If you’re looking at an ABG & have identified that a pt has respiratory acidosis, you can tell whether it was an acute or chronic condition based on how
the kidneys responded. If bicarb is still a normal number, the kidneys haven’t done anything yet meaning its a new condition (acute). In COPD, kidneys
have had time to respond so the bicarb is abnormal.
Acid-Base Disturbances
★ Mixed acid base imbalance can happen at the same time
○ You can’t have respiratory acidosis and respiratory alkalosis because they are compensating each other.
○ Most common is mixed respiratory & metabolic acidosis, usually caused from cardiac arrest
○ Ex. if respiratory arrest occurs, CO2 builds (causes respiratory acidosis) + the patient is also not receiving O2, so cells start w/
anaerobic metabolism → lactic acid builds (causing a metabolic acidosis)
★ Acidosis = abnormal increase in hydrogen ion concentration
○ Accumulation of excess acid or loss of bicarbonate
○ First thing that happens is the acidosis, then the hyperkalemia (even if it is a chronic condition)
★ Alkalosis = abnormal decrease in hydrogen ions concentration
○ Accumulation of excess bicarbonate or loss of acid
○ First thing that happens is the alkalosis, then the hypokalemia (even if it is a chronic condition)
