Acid Base Balance

Question 1

How does alkalaemia effect Ca?

Answer 1

Lowers free Ca by causing Ca ions to come out of solution = increases neuronal excitability = tetany

Question 2

Outline some physiological effects of acidaemia

Answer 2

Increases [K] = effects cardiac muscle excitability = arrhythmia

Increasing [H] = denatures proteins, effects muscle contractility, glycolysis, hepatic function

Question 3

How do the kidneys recover HCO3-?

Answer 3

Recovered in the PCT via Na/H exchanger = expelling H+, reacts with bicarb to form water and CO2, CO2 absorbed into the cell, reacts with H2O to form bicarb, bicarb exported via basolateral membrane to capillaries

Question 4

How does the proximal tubule create HCO3?

Answer 4

AA glutamine broken down to give HCO3- and ammonium (NH4+)

Question 5

Outline the H+ buffering systems in the kidney

Answer 5

Distal tubule = H excreted by H+ATPase, combines hydrogen phosphate

Proximal tubule = H excreted, combines with ammonia to produce ammonium (trapped in lumen)

Question 6

How does pH effect the movement of K in the kidney?

Answer 6

Acidosis = deceased K excretion in distal nephron = hyperkalaemia

Alkalosis = enhanced K excretion in distal nephron = hypokalaemia

Question 7

Outline how the levels of K effect tubular cells in the kidney?

Answer 7

Hypokalaemia = HCO3 recovery = metabolic alkalosis

Hyperkalaemia = HCO3 excretion = metabolic acidosis

Question 8

How does hypoventilation effect acid base balance?

Answer 8

Hypercapnia = fall in plasma pH = resp acidosis

Question 9

How does hyperventilation effect acid base balance?

Answer 9

Hypocapnia = rise in pH = resp alkalosis

Question 10

Outline the characteristics of respiratory acidosis

Answer 10

High pCO2

Normal HCO3

Low pH

Question 11

Outline the characteristics of respiratory alkalosis

Answer 11

Low pCO2

Normal HCO3

Raised pH

Question 12

Outline the characteristics of compensated respiratory acidosis

Answer 12

High pCO2

Raised [HCO3]

Relatively normal pH

Question 13

Outline the characteristics of compensated respiratory alkalosis

Answer 13

Low pCO2

Lowered [HCO3]

Relatively normal pH

Question 14

Outline the characteristics of metabolic acidosis

Answer 14

Low [HCO3]

Low pH

Normal pCO2

Renal cause = normal anion gap (HCO3 replaced by Cl-)

Metabolic cause = increased anion gap (HCO3 replaced by another unmeasured anion)

Question 15

Outline the characteristics of metabolic alkalosis

Answer 15

Raised [HCO3]

Rise in pH

Normal pCO2

Question 16

What is the anion gap?

Answer 16

Diff between measured cations and anions

Question 17

Outline the characteristics of compensated metabolic acidosis

Answer 17

Low HCO3

Lowered pCO2

Nearer normal pH

Peripheral chemoreceptors (carotid bodies) = detect pH drop = ventilation = decreased pCO2

Question 18

What conditions lead to respiratory acidosis?

Answer 18

Type 2 resp failure = alveoli cannot be properly ventilated

E.g. Severe COPD, severe asthma, drug overdose

Question 19

What conditions lead to respiratory alkalosis?

Answer 19

Hyperventilation = anxiety/panic attacks

Type 1 resp failure = hyperventilation in response to long-term hypoxia

Question 20

What conditions lead to metabolic acidosis with an increased anion gap?

Answer 20

Increased anion gap = indicated metabolic prod of an acid

Keto-acidosis

Lactic acidosis

Uraemic acidosis

Question 21

What conditions lead to metabolic acidosis with a normal anion gap?

Answer 21

Normal anion gap = HCO3 is replaced by Cl-

Renal tubular acidosis

Severe persistent diarrhoea, loss of HCO3

Question 22

What conditions lead to metabolic alkalosis?

Answer 22

Severe prolonged vomiting = loss of H+K depletion

Certain diuretics