Acid base Flashcards
What does ph stand for
Potential of hydrogen
What is the ph of gastric juice
2
What is the ph of inside of small intestine
8
State some ways in which acid can be produced in the body
- Breakdown of food esp protein
- CO2 metabolised and forms carbonic acid with water
- Acids resulting from other metabolic activity such as lactic acid in exercise
Name the 3 ways that the body can regulate acid base
- Chemical buffers in blood and interstitial fluid
- Respiratory centre in the brain stem
- Renal mechanism
Define buffer
Solution that can resist pH change upon the addition of an acid or a base
What are the main buffer systems in the body
- Bicarbonate
- Proteins
- Phosphates
What proteins are most commonly used as a buffer system
Haemoglobin in blood
Albumin in plasma
Can chemical buffers eliminate acids or bases from the body
No
Does acidemia lead to hypo/ hyper kalaemia
Hyper
Why does acidemia lead to hyperkalaemia
Cells take in more hydrogen so potassium is displaced
Why do alkalosis lead to hypokalaemia
Because hydrogen goes out of the cell so potassium mvoes in
Does anion gap measure levels in the blood or the plasma
Plasma
What are the cations used in anion gap
Unmeasured cations
K+
Na+
What are the anions used in the anion gap
Unmeasured anions
HCO3-
Cl-
What is meant by the magic 4
way to remember levels of electrolytes in plasma K+=4 Na+=140 HCO30=24 Cl-= 104
Name some of the unmeasured cations
Calcium
Magnesium
Proteins
Name some of the unmeasured anions
Phosphates
Sulfates
Proteins
What is a normal anion gap
8-12mEg/L
How do you calculate anion gap
Na+-(Cl-+HCO3-)
Why does a loss of bicarbonate causing acidosis not lead to a change in anion gap
- Chloride compensates for loss of bicarbonate
- There is an exchange of chloride and bicarbonate
What is it called when there is a surge of chloride leading to acidosis
Hyperchloremic acidosis
What are the causes of normal gap acidosis?
‘gut stuff’ leading to bicarb loss
- Severe diarrhoea
- Laxative abuse
- Villous adenoma
- Others
Name some causes of normal gap acidosis
- Bicarbonate loss
- Reduced kidney H+ excretion
Why does reduced kidney H+ secretion lead to normal gap acidosis
If kidneys are not able to excrete acids efficiently, more HCO3- is needed to buffer them leading to drop in bicarbonate (lost into carbonic acid)
Causes of reduced kidney H+ excreted
Renal failure
How far up can the elevated anion gap go
24mEg/L
What are the causes of elevated gap acidosis
Too much acid or not enough bicarbonate is being produced:
- Ketoacidosis
- Lactic acidosis
- Also severe renal failure
Which unmeasured anion contributes to the majority of the value of anion gap
Albumin
What causes low gap acidosis
Albumin dropped leading to surge in HCO3- and Cl-
- Haemorrhage
- Nephrotic syndrome
- Intestinal obstruction
- Liver cirrhosis
What kind of acids do the lungs deal with
CO2
What organ can prevent metabolic acidosis
Kidney
Which 2 tasks must the kidney complete to control acid base balance
- Reabsorption of all filtered bicarbonate
- Excrete the daily acid load
Where is 70-90% of the bicarbonate reabsorbed
Proximal convuluted tubule
Where is 10-30% of the bicarbonate reabsorbed
Throughout rest of the nephron (after PCT)
Which enzyme breaks HCO3 into CO2 and OH
Carbonic anhydrase
Where in the kidney does active excretion of H+ happen
Various parts of the distal kidneys
What do alpha intercalated cells secrete and reabsorb
Secretes acid
Reabsorbs HCO3-
What pumps does alpha intercated cell use to excrete acid
H+ ATPase pump
H+/K+ exchanger
What do beta intercalated cells excrete/ absorb
Secretes HC03-
Reabsorbs acid
How do renal tubule cells act during acidosis
- Need to get rid of H+ into the lumen using sodium transporter
- Bicarbonate moves into the cell
Which 2 systems are used to allow excretion of acid
HPO42- buffer and ammonium
Which pathways is used by kidneys to produce bicarbonate
Glutimate pathway
How do renal cells act during alkalosis
Tubular cells secrete bicarbonate ions and reclaim hydronium to acidify the body
This uses separate ATPase
K+ traded for H+
What are the stimuli for HCO3- reabsorption in PCT
Low ph
Low K+
Angiotensin II
What does drop in ph or increase in aldosterone do to the collecting duct
- Sodium reabsorption
- Displaced by H+ and K+
What does the Henderson-Hasselbach equation find
- pH of buffer solution
- ratio of conjugate base: acid
pH=
PKa + log (conjugate base)/ (acid)
What does pKa=
-log( equilibrium constant)