Chempath 3: Acid base disorders Flashcards

1
Q

Which acid/base disorder do you get in pyloric stenosis ?

A

Hypokalaemic hypochloraemic Metabolic Alkalosis

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2
Q

What happens to HCO3 in Pyloric stenosis and why ?

A

HCO3 increases because of relative fluid loss in vomiting. Also carbonic acid dissociates and only the H+ ions are lost, HCO3 is retained.

H+ further decreases due to exchange for intracellular K+ to adjust the hypokalaemia.

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3
Q

normal range for [H+]

A

35-45 mol/l in ECF

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4
Q

calculation for pH

A

low 1/[H+]

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5
Q

list the different types of buffering systems in the body

A

bicarbonate - H+ + HCO3- –> H2C03 (ECF, globular filtrate)

haemoglobin - H+ + Hb- –> HHb (RBC)

phosphate - H+ + HPO4 - –> H2PO4 (RTF, IC)

also protein and bone

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6
Q

what is the most important buffering system in the human body

A

Bicarbonate

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7
Q

how are h+ ions excreted

A

H+ + HCO3- –> H2CO3 –> CO2 + H20

as you buffer H+ you use up bicarbonate ions
bicarbonate buffer is only effective in the short term
to maintain homeostasis, kidney needs to excrete H + ions and regenerate bicarb ions
Bicarbonate is regenerated through the production of carbonic acid
H + ions cannot pass through the membrane by itself - Na+/H+ exchange needed

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8
Q

3 causes of metabolic acidosis

A

increased H + with decreased bicarbonate

  • increased H + production eg DKA
  • decreased H + excretion eg RTA
  • bicarbonate loss eg intestinal fistula

if compensated - low CO2

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9
Q

3 causes of respiratory acidosis

A

increased CO2 producing increased H+ and a slightly increased bicarb

  • decreased ventilation
  • poor lung perfusion
  • impaired gas exchange

slower kidney compensation - increased H+ excretion and bicarb generation

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10
Q

3 causes of metabolic alkalosis

A

decreased H+ (increased pH) with increased bicarbonate

  • H+ loss (pyloric stenosis)
  • hypokalaemia
  • ingestion of bicarbonate

rise in C02 to compensate

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11
Q

3 causes of respiratory alkalosis

A

due to hyperventilation

  • voluntary
  • artificial ventilation
  • stimulation of respiratory centre
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