Acid Base Imbalances

Normal pH

7.35 - 7.45

7.4 = perfect

Acidosis

pH less than 7.35

excess H+

Alkalosis

pH greater than 7.45

decreased H+

Three buffering systems

Maintain blood pH

1.) Chemical buffers

2.) Respiratory system

3.) Renal system

*chemical buffers limit pH change

*lungs + kidney change body’s acid-base balance over time

Chemical Buffer System

immediate action: minimizes changes in pH

3 components:

• Bicarbonate - eliminates CO2

• proteins

• phosphate

Respiratory regulation

Ventilation impacts PaCO2 (amount of CO2 in body), which impacts acid-base balance

Occurs within minutes

• in metabolic disorders, ventilation provides respiratory compensation, but does not restore pH completely

decreased ventilation

• CO2 elimination falls = PaCO2 rises

• more carbonic acid + H = lower pH

respiratory acidosis

increased ventilation

• CO2 elimination rises = PaCO2 falls

• less carbonic acid + H = pH rises

respiratory alkalosis

Renal Buffering System

long-term regulation of acid-base balance

takes hours to days

• kidneys adjust both H and bicarb to control pH

Renal system effects: Low blood pH

Acidosis:

• increase H+ excretion through urine

• conserve more bicarb to help eliminate CO2

Renal system effects: High blood pH

Alkalosis:

• decreased H+ excretion; holds onto urine

• increase bicarb excretion through urine to hold onto CO2 in body

the CO2 and Bicarb Buffer system

CO2 acts like an acid, HCO3 acts like a base

• increased CO2 = high acidity (acidosis)

• increased HCO3 = high buffering (alkalosis)

determines metabolic acidosis/ alkalosis

Respiratory Acidosis

• low pH

• high PaCO2 = impaired CO2 elimination

Causes: COPD, hypoventilation, opioids

Respiratory Alkalosis

• high pH

• low PaCO2 = excess CO2 loss

Causes: anxiety, hyperventilation, pulmonary embolism

Metabolic acidosis

• low pH

• low bicarb = cannot eliminate CO2

Causes: diabetic ketoacidosis (DKA), lactic acidosis, renal failure

S/S:

• Kussmaul respirations, hyperkalemia

Metabolic Alkalosis

• high pH

• high HCO3 = excess loss of CO2

Causes: vomiting, excess antiacids, diuretics

S/S:

• hypokalemia

• dysrhythmias

Uncompensated in Acid-Base Disorder

pH is abnormal

• no or minimal response in PaCO2 or HCO3 yet

Partially Compensated in Acid-Base Disorders

pH is still abnormal, but the opposite system is responding

• change in PaCO2 or HCO3 is present, but pH is still outside normal range

Fully compensated in acid-base disorder

pH is normal but PaCO2 or HCO3 remains abnormal

Normal CO2 levels

35 - 45

Normal HCO3 levels

Early 20s (22-26)