Introduction to Acid-base balance Flashcards
Acid
A substance that can donate H+ (and has a high concentration of H+)
Base
A substance that can accept a H+ (low H+ concentration)
As H+ increases
pH decreases by a log of 10
As H+ decreases
pH increases by a log of 10
What is the normal blood pH
7.35-7.45
Acidemia
Increase in H+ means a low pH (
Alkalemia
Decrease in H+, means a high pH (>7.40)
Acidosis
Process which increases plasma H+
Alkalosis
Process which decrease plasma H+
How does the body regulate (balance) acids and bases
- Chemical buffer system
- Respiratory buffer systems
- Liver oxidation of strong acids
- Renal mechanisms
(Goes in this order)
Chemical buffer system
- phosphate (IC)
- protein (hemoglobin, amino acids, plasma proteins)
- HCO3 (carbonic acid becomes bicarb)
Respiratory buffer system
Retain or blow off CO2 depending on whether it is an acidosis or alkalosis problem
What part of the brain controls the respiratory buffer system
Brainstem (acts within 1-3mins)
What happens to respirations when there is a rise in H+ (metabolic acidosis)
Deep, rapid breathing, expels CO2 which causes H+ to be reduced
What happens to respirations when there is a decrease in H+ (metabolic alkalosis)
Slower, shallow breathing, expels less CO2, which causes H+ to be increased
Kidney role in H+ maintenance
ONLY the kidneys can get rid of non-volatile acids (lactic, uric, phosphoric) via H+, HCO3 excretion or reusing of the H+ (NH4)
What is the ultimate acid-base regulatory organ
Kidney
Most important renal mechanism for regulating HCO3
- Reabsorbs HCO3 and generates new HCO3
2. Excretes HCO3
What does reabsorption of HCO3 defend agains
Acidosis
What does excretion of HCO3 defend against
Alkalosis
ABG
Arterial blood gas. Measures pH, pCO2, pO2 Calculates HCO3
pH=
HCO3/pCO2
What is the usefulness of the ABG
Determining if a patient has metabolic/respiratory acidosis or alkalosis
What is the normal pCO2
38-42
What is the normal HCO3
24 (22-26)
Anion gap
The difference in measured cations (+) and measured anions (-). Can measure in serum, plasma, or urine
Normal AG
12 (+/-2)
Actual AG equation
Na+ - (Cl- + HCO3-)… Cations minus anions
What is the diagnosis if you have a high AG
metabolic acidosis
1st step in acid-base disorders
Consider clinical setting (anticipate the disorder)
2nd step in acid-base disorders
Is the patient academic or alkalemic
3rd step in acid-base disorders
Is the process metabolic or respiratory
4th step in acid-base disorders
If metabolic acidosis, is there an anion gap or not
5th step in acid-base disorders
Is compensation appropriate (use formulas)
6th step in acid-base disorders
Is there more than one disorder present, use the change in formulas
If it is a metabolic problem
The lungs will try and compensate
If it is a respiratory problem
the kidneys will try and compensate
What 2 things do you look for in order to determine if it is metabolic
HCO3 and pCO2 lab values should go in the same direction
Respiratory alkalosis
Hyperventilation, causes decrease in pCO2, which increases pH
Signs of respiratory alkalosis
Dizziness, light headed, confusion (pts on ventilators)
Lab findings of respiratory alkalosis
pH = increase pCO2 = decrease HCO3 = decrease (renal compensation)
Respiratory acidosis
Hypoventilation, causes an increase in pCO2, which decreases pH
Signs/causes of respiratory acidosis
Upper airway obstruction, SOB, headache, blurred vision
Lab finding of respiratory acidosis
pH = decrease
pCO2 = increase
HCO3 = increase
(renal compensation
Metabolic alkalosis
Too much OH-, very little H+
Signs/causes of metabolic alkalosis
Loss of H+, or retention of bicarbonate. Slow, shallow breathing
Lab finding of metabolic alkalosis
pH = increase
pCO2 = increase
HCO3 = increase
(respiratory compensation)
Metabolic acidosis
Too much H+, very little OH-
Signs/causes of metabolic acidosis
Kidney cannot clear the H+ or too much H+ generation. Deep, rapid breathing
Lab finding of metabolic acidosis
pH= decrease pCO2 = decrease HCO3 = decrease
Mixed/compensatory acid/base
More than one acid-base disorder occurring simultaneously. You will see pCO2 and HCO3 in opposite directions
