Acid Base Balance And AKI Flashcards
How does alkalemia lower free calcium?
- High pH causes a low H+ concentration
- Albumin donates H+ from its carboxyl groups and becomes negatively charged
- Serum Ca2+ binds to albumin, reducing it in free circulation
What are the symptoms of alkalemia that arise due to a drop in free calcium?
Muscle twitches,
Numbness and tingling,
Tetany and paralysis of respiratory muscles.
How does acidosis increase free calcium?
More H+ bound to albumin means that calcium cannot bind or is displaced.
What calcium related signs occur in acidemia?
Arrhythmias,
Denaturing of proteins too, but this isn’t a sign obviously, stupid question lol 😝
What percentage of acid base regulation occurs at the kidney?
How long does this regulation take to occur?
25% (75% lungs)
1-2 days
What mechanism occurs in the proximal convoluted tubule epithelial cells to buffer urine?
Breakdown of glutamine into ammonia which diffuses freely over the membrane into nephron and binds H+ ions, becoming ammonium ions that cannot cross the membrane back.
What titratable buffer is found in the nephron?
Hydrogen phosphate HPO2- (forms H2PO4-)
How do alpha intercalated cells help reduce acidosis?
Bicarbonate ions produced in the cell are exchanged for chloride ions in the blood to increase buffering.
Hydrogen ions are excreted into tubular lumen in exchange for potassium
How do beta intercalated cells help reduce alkalosis?
Produce H+ from H20 and C02 in the cell via carbonic anhydrase enzyme. H+ then selectively reabsorbed into the blood, exchanged for potassium.
What can all cells do to help buffer pH changes?
Exchange potassium for hydrogen, in each direction.
Acidosis is intrinsically linked to which type of potassium imbalance?
Which is alkalosis linked to?
Acidosis - hyperkalaemia
Alkalosis - hypokalaemia
How is respiratory acidosis caused?
What is it associated with?
CO2 retention reacting with water to produce H+,
Alveolar hypoventilation and raised pCO2
How is respiratory alkalosis caused?
Hyperventilation increases excretion of CO2, lowering pCO2
Often caused by excessive artificial ventilation
How is metabolic acidosis caused?
Raise in H+ outside of the respiratory pathways, such that metabolic input exceeds excretion
How can the body compensate for metabolic acidosis?
Respiratory - increased ventilation
Renal - secretion of H+ at DCT and CD, reabsorption of HCO3-
What is the anion gap?
What is the normal range for the anion gap?
Difference between measured (not all) anions and cations.
Normally 10-18mmol/L
How can you tell if there is a renal cause for acidosis?
Anion gap remains unchanged. HCO3- is not produced in great enough quantities but is replaced by Cl-, which is also a measured anion
What causes metabolic alkalosis?
Excessive vomiting - excretion of H+ ions in form of stomach acid. Excessive bicarbonate or antacid ingestion.
What respiratory compensation is there for metabolic alkalosis?
What renal compensation exists?
Hypoventilation (CO2 retention produces more H+ but also HCO3- that must be excreted)
HCO3- not absorbed in proximal tubule
HCO3- secreted at DCT/CD and H+ reabsorbed
What is uraemia?
Build up of nitrogenous waste in the bloodstream (Particularly urea and creatinine). Caused by poor filtration by the kidneys
What is AKI?
deterioration of renal function occurring over hours or days
What features are associated with AKI?
Urea and creatinine raise rapidly,
Oliguria (low urine production),
Often reversible.
What are pre renal causes for AKI?
decreased blood flow: Portal hypertension, Hypovolaemia, Shock, Renal artery stenosis
Which drugs increase incidence of pre renal causes of AKI by impairing renal auto regulatory systems?
NSAIDS and ACEi
