11 + 12 - Acid and Base Flashcards
What is a buffer
solution that can resist pH change upon the addition of an acid or a base. Able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.
What makes up a buffer
Consist of a weak acid and the salt of that acid functioning as a weak base
Where is HCO3- reabsorbed mainly
PCT
What do alpha intercalated cells excrete (DT)
secretes acid, absorbs bicarb
What do beta intercalated cells excrete and absorb
Secrete bicarb
absorb acid
What is the cause of metabolic alkalosis
Increased bicarb production/reduced excretion
Decreased production of H+ or excretion of H
Causes of H+ loss
Low chloride - Diuretics which inhibit chloride resorption
= Volume depletion results in secondary hyperaldosteronism as a result there is increased exchange of sodium for K and H, K depletion further promotes H excretion
Low K+
= Hyperaldosterone
= Liquorice
= Barters, liddles, gitelmans
Causes of alkali intake
Milk/alkali syndrome
Bicarb therapy
Cause of metabolic acidosis
an excess of hydrogen ions, can result either from an excess production of hydrogen ions, a loss of bicarbonate/ failure to regenerate bicarbonate in the kidney.
o ‘metabolic acidosis’.
Normal anion gap
12-16
12 if K+ excluded
Raised anion gap acidosis
o Bicarbonate goes down
o Increase in unmeasured anion
Causes of increased anion gap
o Methanol intoxication o Uremia o Isoniazid or Iron overdose o Salicylate intoxication o Ketoacidosis o Methanol o Aldehyde (paraldehyde) o Lactate
Normal anion gap acidosis
o Chloride increases but bicarb decreases because chloride is swapped for bicarb via an antiport
Renal causes of normal gap acidosis
Renal Tubular Acidosis (cannot excrete H+)
Carbonic anhydrase inhibitors
GI causes of normal anion acidosis
Severe diarrhoea (loss of bicarb)
Uretero-enterostomy or Obstructed ileal conduit
Small bowel fistula
Other causes of normal anion gap acidosi
Losses via NG tube
Villous adenoma
Recovery from DKA
• Ketone anions secreted as potassium/sodium salts
• Chloride ions retained to maintain electrical neutrality
Low gap acidosis
Decrease in Unmeasured anion (e.g. loss of albumin)
• Haemorrhage
• Liver cirrhosis
• Nephrotic syndrome.
In PCT
CA and bicarb ting (draw it out)
- In the lumen, CA converts H+ and bicarbonate into carbonic acid, the pumping out of the hydrogen atoms via Na/H pump pushes the equation to the left producing H2O and CO2.
- Water and carbon dioxide diffuses into the cell where the equation to the right is favoured as the H+ is constantly being pumped out
- The water and carbon dioxide form carbonic acid which then breaks down into bicarb and acid. The bicarb cannot leave through the lumen so it is pumped into the interstitium via the Na+/HCO3¬¬¬-
Normal pH
7.35 to 7.45
- Formation of H+ from cellular metabolism
o Acids produced during the breakdown of foods (esp. proteins)- 60 mmol/d
o CO2 metabolically produced and form carbonic acid with H2O- 15 mol/d,
o Acids resulting from other metabolic activity e.g. lactic acid in exercise- 1.5 mol/d
o In disease state, even more ketoacids
Methanol poisoning forms what acid
formic acid
Ethylene glycol forms what acid
Glycolic acid + oxalic acid
CO poisoning, drugs form what acid
Lactic acid
How does acidaemia lead to hyperkalaemia
tissues release K+ from within the cells
o Potassium swapped and replaced by the H+ and in order to maintain electroneutrality.
H+ taken up by cells to reduce serum H+.
