Acid-Base Physiology Flashcards
What is the normal pH range?
7.40 (7.38-7.43)
What are two types of buffers?
Intracellular and extracellular
Name some intracellular buffers.
Organic phosphates and proteins
Hemoglobin- deoxyhemoglobin
Name some extracellular buffers
Phosphate
Bicarbonate
Plasma protein (albumin)
What is the most important buffer? Why?
Bicarbonate.
Because it is present in high concentrations, pKa is closer to arterial pH, and the conjugate CO2 is excreted by lungs and kidneys
What is the Henderson-Hasselbach equation?
pH = pKa + log ([A-] / [HA])
Name two ways in which acid/base can be altered.
- Changes in Pco2- Respiratory disorder
2. Too much or too little acid- Metabolic disorder
True or False: Compensation never completely corrects and acid base disorder
TRUE
What is the main disorder in a respiratory acidosis?
Increased Pco2 that leads to a decreased pH
What are four causes of hypoventilation leading to a respiratory acidosis?
- Obesity
- ALS
- Drugs (acute)
- Muscle fatigue- pneumonia
How do patients compensate for a respiratory acidosis?
Compensation through the preservation of bicarbonate in the kidneys which is slow
What is the main disorder in respiratory alkalosis?
Decreased Pco2 leading to increased pH
What are three causes of chronic hyperventilation in respiratory alkalosis?
Altitude
Neurological disorders
aspirin toxicity
What are two causes of acute hyperventilation in respiratory alkalosis?
Anxiety
Minute volume too high on ventilation
How do patients compensate for respiratory alkalosis?
Kidney increase excretion of bicarbonate (slow)
How do you calculate an anion gap?
Na+ - (Cl- + HCO3-) = 12+/- 2
What are the common causes of metabolic alkalosis?
MUDPILES M- methanol U- uremia D- diabetic P- propylene glycol I- isoniazid L- lactate E- ethylene glycol S- salicylates
What are three causes of an anion gap with normal pH?
GI losses
Renal losses
Too much saline
How does a patient compensate for a metabolic acidosis?
Increased ventilation which is a quick response
How can you determine if a patient is compensating appropriately?
Use Winter’s Formula:
expected Pco2 =
1.5[HCO3-] + 8 +/- 2
If pCO2 is in range then the patient is compensating if not they aren’t
What causes a metabolic alkalosis?
Metabolic alkalosis is either caused by increased bicarbonate or decreased CO2
What are two causes of too much bicarbonate?
too much antacid or hypovolemia (kidneys hanging onto bicarb)
What is a cause of decrease CO2 in metabolic alkalosis?
Vomiting
How does a patient compensate for a metabolic alkalosis?
Decrease in ventilation and increase in Pco2
For acute respiratory disturbances, a change in PaCO2 of 10 Torr yields a pH change of about ______ in pH.
0.08
For chronic respiratory disturbances, a change in PaCO2 of 1 Torr should lead to compensatory change in [HCO3-] of ____ in the same direction.
0.4 meq/L
For metabolic disturbances, a decrease in [HCO3-] of 1meq/L should result in an increase in PaCO2 of _____.
0.7 Torr