Acid/Base Flashcards
What is the ref range for blood conc?
35-45 nmol/L
What is the Henderson-Hasslebach equation?
pH =pKa + Log ([A-]/[HA])
- the lower the pKa value the stronger the acid
Describe Alkalosis
- condition where the body fluids have the excess base alkali
- decreased CO2 or increased bicarbonate in blood
- examples = respiratory, metabolic, hypokalemic
Describe Acidosis
- when your body fluids contain too much acid
- it occurs when your kidney & lungs can’t balance pH
- types = respiratory & metabolic
What is the first line of defence against a pH shift?
Chemical buffer system
- bicarbonate buffer
- phosphate buffer
- protein buffer
What is the 2nd line of defence against pH shifts?
physiological buffers
- respiratory mechanism (CO2 excretion)
- renal mechanism
(H+ excretion)
Describe Carbonic Anhydrase
- enzyme found in RBCs, gastric mucosa, pancreatic cells & renal tubules
- carbonic acid is converted into CO2 & H2O by this enzyme
What regulates the elimination of CO2 in the lungs ?
the respiration rate
What happens when there is a rise in CO2 levels?
- rise in CO2 = low pH which is detected by chemoreceptors in the medulla oblongata, carotid & aortic body
What can a decreased ventilation efficiency result in?
- CO2 retention in blood
- along with increased in blood conc - acidosis may occur
What the renal control of the acid base balance ?
- filtration
- reabsorption
- secretion
Describe filtration in renal control of acid/base balance
- blood plasma & other dissolved substances get filtered into the glomerular capsule
- glomerulus –> glomerular capsule
Describe reabsorption in renal control of acid/base balance
- water, ions & other substances reabsorbed
- occurs in renal tubule & collecting duct
- goes from the renal tubule lumen –> peritubular capillaries
- ultimately back into the blood
Describe Secretion in the renal control of acid/base balance
- wastes, drugs & excess ions are secreted from the peritubular capillaries into the renal tubule
- these substances eventually make their way to the urine
What is the consequence of bicarbonate entering the lumen of the proximal tubule ?
- its unable to escape
- it can’t be reabsorbed directly
What are the consequences of acidosis ?
- raised CO2
- Raised H+ in plasma
Describe normal lung function
- expels CO2 & push equilibrium to the left
- greater formation of carbonic acid
- pH in plasma raised
- depletes H+ conc.
What are some causes of metabolic acidosis ?
- increased production of H+
- ingestion of drugs metabolised to acids
- impaired excretion of H+ via kidneys
- loss of bicarbonate in urine or GI tract
What are the lab findings for acute metabolic acidosis ?
pH = decreased
pCO2 = normal
[HCO3] = decreased
What are the lab findings for compensated metabolic acidosis ?
pH = normal
pCO2 = decreased
[HCO3] = decreased
What are the causes of metabolic alkalosis ?
- loss of hydrogen ions in vomit
- potassium deficiency
- large doses of an alkali-sodium bicarbonate
What are the lab findings for acute metabolic alkalosis ?
pH = increased
pCO2 = normal
[HCO3] = increased
What are the lab findings of compensated metabolic alkalosis ?
pH = normal
pCO2 = normal/slight increase
[HCO3] = marked increase
Define COPD
Chronic Obstructive Pulmonary Disease
- flow of air into & out of the lungs is impaired
What are the 3 mechanisms of airway obstruction?
- lumen partially occluded by excessive secretions
- causes in the wall of the airway
- outside the airway destruction of the paranchyma may cause loss of elasticity & narrowing
Describe acute cases of respiratory acidosis
- acute within minutes or hours
- non-compensated as it can take 48-72 hours for bicarbonate reabsorption to occur
- hypoventilation = an increase in pCO2 & H+ will rise in the blood
What are the lab findings for acute respiratory acidosis ?
pH = low
pCO2 = increased
[HCO3] = normal/slight increase
What are the lab findings for compensated respiratory acidosis ?
pH = normal
pCO2= increased
[HCO3] = increased
Describe respiratory alkalosis
- less common
- acute no renal compensation
- hysterical over-breathing
-hypoxia - raised intracranial pressure
