Acid Base Flashcards
What are H+ donors?
Acids
What are H+ acceptors or give up OH- in solution?
Bases
What are examples of acids/bases that are strong (dissociate completely in solution)?
HCl, NaOH
What is an example of a weak acid/base (one that dissociates only partially in solution)?
Carbonic acid (H2CO3)
What is the holy-grail of acid-base?
H+
What is the physiologic pH range?
7.35-7.45
True or false: Small changes in pH can produce major disturbances in physiology.
True
Do most enzymes function within a very narrow or very broad pH range?
narrow
Acidosis is when pH is what?
below 7.35
Alkalosis is when pH is what?
above 7.45
What is the survival range of pH?
6.8-8.0
True or false: The body produces more acids than bases.
True
What two molecules join to form carbonic acid?
carbon dioxide and water
What enzyme is responsible for the creation of carbonic acid?
Carbonic anyhydrase
What are the products of the breakdown of carbonic acid?
Bicarbonate and hydrogen ion
How does the body obtain/create acids?
- taken in with foods
- produced by metabolism of lipids and proteins
- cellular metabolism produces carbon dioxide
What is the volatilie acid of the lung?
CO2
Fixed acids of the kidney are non-volatile and include?
- phosphoric acid
- sulfuric acid
- lactic acid
- keto-acids
Phosphoric acid is produced from?
Membrane lipid breakdown
Sulfuric acid is produced from?
Protein breakdown
Lactic acid is produced from?
Ischemia, hypoxia
Keto-acids are produced from?
Disease (diabetes)
Buffers control what?
Acid production
What are buffers?
A mixture of a weak acid and conjugate base to resist a change in pH
Effective buffers have a pK within?
1.0 pH unit of 7.4
How do buffer systems resist a change in pH?
Take up H+ or release H+ as conditions change
Which buffer system is the first line of defense against pH shift?
Chemical Buffer system
The chemical buffer system has what three components?
- bicarbonate buffer system
- phosphate bufer system
- protein buffer system
Which buffer system is the second line of defense against pH shift?
physiological buffers
What two components make up physiological buffers?
- Respiratory mechanism (CO2 excretion)
- Renal mechanism (H+ excretion)
List the two extracellular buffers.
- Bicarbonate (HCO3-)
- Phosphate (H2PO4-)
List the four intraceullular buffers.
- bicarbonate-carbonic acid
- hemoglobin (inside RBCs)
- proteins (Imidazole of histidine and alpha amino acids)
- organiz phosphates (ATP)
What is the major intracellular buffer?
Phosphate buffer
Body pH can be changed by doing what with breathing?
Changing rate and depth of breathing
Exhalation of carbon dioxide can be used as a respiratory buffering mechanism, but only works with what type of acids?
Volatile acids (does NOT changed fixed acids, like lactic acid)
If the kidneys fail, what also fails?
pH balance
What is the purpose of renal buffering mechanisms?
- eliminate large amounts of acid
- excrete base
- conserve and produce bicarbonate ions
What are the three mechanisms renal buffering mechanisms use for the elimination of acid?
- reabsorption of bicarbonate (HCO3-)
- excretion of fixed acid (non-volatile acid) as titratable acid such as inorganic phosphate
- excretion of fixed acid as ammonium (NH4+)
If pH balance fails due to kidney failure what occurs?
acidemia
What are the normal values of fixed H+ production, excretion of H+ as titrable acid, and excretion of H+ as NH4+?
Fixed production = 50mEq/day
Titratable acid = 20mEq/day
NH4+ = 30mEq/day
If you are given the following values:
Total production of fixed H+ = 500mEq/day
Excretion of H+ as titratable acid = 100mEq/day
Excretion of H+ as NH4+ = 400mEq/day
What condition is this patient experiencing?
Diabetic Ketoacidosis
If you are given the following values:
Total production of fixed H+ = 50mEq/day
Excretion of H+ as titratable acid = 10mEq/day
Excretion of H+ as NH4+ = 5mEq/day
What condition is this patient experiencing?
Chronic Renal Failure
What are the two approaches of interpreting acid-base abnormalities?
- traditional
- stewart
What is analyzed in the traditional method of acid base interpretation?
- base excess
- bicarbonate
- PCO2
What is analyzed in the stewart method of acid base interpretation?
- pH determined by independent variable
- independent variables include PCO2 and cation-anion difference
At what point is compensation for acid-base imbalance complete?
if pH is brought back WNL
Is partial compensation of pH range still outside normal limits?
Yes
If the primary problem is metabolic, what type of compensation is used?
respiratory compensation (hyperventilation or hypoventilation)
If the primary problem is respiratory, what type of compensation is used?
Metabolic compensation (renal mechanisms)
What is the rate of respiratory compensation mechansisms?
severl minutes to hours
What is the rate of metabolic (renal) compensation mechanisms?
several hours to days
What is the compensatory reponse to non-respiratory acidemia?
hyperventilation
(increase bicarbonate reabsorption)
What is the compensatory response to respiratory acidemia?
- chemical buffering if acute
- renal regulation if chronic
(increase bicarbonate reabsorption)
What is the compensatory response to non-repiratory alkalemia?
hypoventilation
(increase bicarbonate excretion)
What is the compensatory response to respiratory alkalemia?
- chemical buffering if acute
- renal regulation if chronic
(decrease bicarbonate reabsorption)
If given decreased bicarbonate as primary disturbance and decreased PCO2 as compensation, what is the acid base disturbance?
Metabolic acidosis
If given increased bicarbonate as primary disturbance and increased PCO2 as compensation, what is the acid base disturbance?
Metabolic alkalosis
If given increased PCO2 as primary disturbance and increased bicarbonate as compensation, what is the acid base disturbance?
Respiratory acidosis
If given decreased PCO2 as primary disturbance and decreased bicarbonate as compensation, what is the acid base disturbance?
Respiratory alkalosis
Diabetic ketoacidosis, lactic acidosis, salicylate poisoning, methanol/formaldehyde poisoning, and ethylene glycol poisoning can cause what?
excessive production or ingestion of fixed H+ which results in metabolic acidosis
Diarrhea and type 2 renal tubular acidosis can cause what?
Loss of bicarbonate which will result in metabolic acidosis
Chronic renal failure, type 1 renal tubular acidosis, and type 4 renal tubular acidosis can cause what?
inability to excrete fixed H+ which will result in metabolic acidosis
What are the five steps to acid base interpretation?
- determine pH
- determine PCO2 and HCO3 values
- determine primary and compensatory shift
- determine respiratory component of pH change
- calculate PaO2/FiO2 ratio
For respiratory component of acid-base change, the pH decreases how many units for every 10 increase in PaCO2 above 40mmHg?
0.05 units
What is the normal PaO2/FiO2 ratio?
> 400
A PaO2/FiO2 ratio less than 200 indicates what?
severe pulmonary disease (respiratory failure)
What is the anion gap (AG) equation?
AG = [Na+] + [K+] - [Cl-]
What is the strong ion difference (SID) equation?
SID = [Na+] + [K+] - [Cl-] - [lactate]
