Homeostasis by the kidney- Acid-Base balance

Question 1

What are the 2 mechanism of dealing with the acid load in the body

Answer 1

Buffering

Elimination

Question 2

What is used in mechanisms of buffering when dealing with acid load in the body

Answer 2

Bicarbonate in Extracellular Fluid (ECF)
HPO42- in Intracellular Fluid (ICF)
CO3 2- in Bones

Question 3

How is the acid load in the body dealt with through elimination

Answer 3

Increased respiratory drive to increase CO2 excretion
Acute response
Increased hydrogen ion secretion by kidneys
Chronic sustained response

Question 4

What is the acute response of the body to acid load

Answer 4

increased respiratory drive to increase CO2 excretion

Question 5

What is the chronic sustained response to acid load

Answer 5

increased hydrogen ion secretion by the kidneys.

Question 6

Homeostasis maintains the pH of the ECF between

Answer 6

7.35 - 7.45

Question 7

plasma ph level below 7.35 is _____

Answer 7

acidosis

Question 8

plasma levels rise above 7.45 is __

Answer 8

Alkalosis

Question 9

Alterations outside these normal plasma pH range affects all body systems and result in

Answer 9

coma, cardiac failure and circulatory collapse

Question 10

What does Henderson-Hasselbalch Equation explain in acid base balance?

Answer 10

Inverse relationship between pH and plasma concentration of CO2 i.e. when one goes up the other goes down and vice versa. So when pCO2 increases, e.g. in COPD, pH decreases (acidosis) as CO2 reacts with water to form carbonic a

Question 11

What are the 2 main sources of acid generations in the body

Answer 11

carbolic (volatile) acids

Non-Carbolic (non-volatile) Acids

Question 12

What are the sources of carbolic acids in the body

Answer 12

Generated from metabolism of carbohydrates and fats
Produced as CO2 and converted to H+ and HCO3-
Reconverted back to CO2 and eliminated by the lungs through loss of CO2

Question 13

What the sources of non-carbolic (non-volatile) acids in the body

Answer 13

Generated from metabolism of sulphur containing amino acids

Buffered with HCO3- before eliminated by the kidneys through loss of H

Question 14

What is the normal range of urine PH

Answer 14

4.6 - 8

Question 15

What is the normal range of blood pCO2

Answer 15

4.7 - 6.0

Question 16

What is the normal ranges of blood HCO3-

Answer 16

22 - 26 mmol/L

Question 17

What are main sites of nephron where acid is excreted

Answer 17

proximal convoluted tubule and the intercalated cells of cortical collecting ducts

Question 18

The kidney has limited acid secretions in form of

Answer 18

H+

Question 19

______of filtered bicarbonate is reabsorbed back into systemic circulation

Answer 19

80-90%

Question 20

How does the kidney excrete acid in the proximal convoluted tubule?

Answer 20

secrets H+ through the NaHE

NH3 + H+ –> NH4+ –> Glutamine –> alpha ketoglutarate –> 2HCO3

Question 21

PH of the ultrafilterate falls from about 7.40 to ___ at the end of the proximal convoluted tubules

Answer 21

6.70

Question 22

____ is the most prevalent filtered buffer in the distal nephron where urinary pH< 5.8 (pKa = 6.8)

Answer 22

HPO4-2

Question 23

What is the name of the specialised cell lining the collecting duct

Answer 23

Intercalated cell type A

Question 24

How is acid excreted in the cortical collecting duct?

Answer 24

Ammonium excretion both in the Proximal collecting ducts and direct diffusion of lipid soluble ammonia constitutes a major adaptive response to acid load

Question 25

What is the effect of decrease in extracellular bicarbonate on the PH of the cell?

Answer 25

increases the gradient across basolateral membrane for bicarbonate diffusion out of the cell thereby lowering tubular cellular pH

Question 26

What are the causes of metabolic acidosis

Answer 26

Loss of bicarbonate - Diarrhoea, Diuretic therapy Ingestion of acid -Aspirin, Ethylene glycol, Methanol Endogenous acid production - Lactic acidosis, ketoacidosis Decrease acid excretion - Renal failure Inadequate oxygen delivery resulting in anaerobic metabolism (lactic acid generation)

Question 27

what are some examples of bicarbonate loss that can cause metabolic acidosis?

Answer 27

Diarrhoea, Diuretic therapy

Question 28

what are some example of acid ingestion that can cause metabolic acidosis?

Answer 28

Aspirin, Ethylene glycol, Methanol

Question 29

what are some example of endogenous acid production that can cause metabolic acidosis?

Answer 29

Lactic acidosis, Ketoacidosis

Question 30

what is an example of decrease acid excretion that can cause metabolic acidosis?

Answer 30

renal failure

Question 31

What is the main causes of metabolic alkalosis (increased HCO3 – concentration)?

Answer 31

Loss of acid | Loss of stomach acid (vomiting)

Question 32

What is the main cause of respiratory acidosis

Answer 32

Chronic lung diseases- COPD, Pulmonary fibrosis

Question 33

Causes Respiratory alkalosis (reduced CO2 concentration)

Answer 33

Hyperventilation- anxiety, pneumonia | Acute bronchial asthma

Question 34

Case 1: A 28 year old diabetic lady is admitted with high blood sugars following a viral illness. Arterial blood gas on admission: PH 7.0 (7.35-7.45), PCO2 3.5 Kpa (4.7-6.0), Bicarbonate 18 mmol/L (22-26). what is the diagnosis

Answer 34

metabolic acidosis

Question 35

Case 2: A 72 year old female is admitted with exacerbation of COPD. Arterial blood gas on admission PH 7.0 (7.35-7.45), PCO2 8.5 Kpa (4.7-6.0), Bicarbonate 32 mmol/L (22-26) What is the diagnosis?

Answer 35

respiratory acidosis with compensation

Question 36

Case 3: A 28 year with profuse vomiting for 2 days following a kebab meal. Arterial blood gas on admission PH 7.90 (7.35-7.45), PCO2 6.5 Kpa (4.7-6.0), Bicarbonate 32 mmol/L (22-26) What is the likely diagnosis?

Answer 36

Metabolic alkalosis with compensation

Question 37

Case 4: A 18 year anxious medical student is admitted with palpitations and light headedness a day before their final examination. He was tachypnoeic on admission with respiratory rate of 28/min. Arterial blood gas on admission PH 7.90 (7.35-7.45), PCO2 3.2 Kpa (4.7-6.0), Bicarbonate 20 mmol/L (22 -26). What is the diagnosis

Answer 37

respiratory alkalosis with compensation

Question 38

rise in plasma acid concentration results in the metabolic acidosis, what are the main compensatory mechanisms?

Answer 38

Hyperventilation Renal hydrogen excretion Buffering of acid in extracellular fluid, cells and bones

Question 39

Rise in plasma bicarbonate concentration causes metabolic alkalosis, what are the main compensatory response to this?

Answer 39

hypoventilation | reduced bicarbonate reabsorption

Question 40

elevated CO2 causes respiratory acidosis, what are the main compensatory response to this?

Answer 40

Increased renal hydrogen ion excretion Increased buffering of carbon dioxide within haemoglobin Loss of bicarbonate in urine

Question 41

reduced CO2 causes respiratory alkalosis, what is the main compensatory response to this?

Answer 41

Increased renal bicarbonate excretion

Question 42

In relation to cation shift during acid base imbalance, Metabolic acidosis is frequently associated with ______ and alkalosis is associated with

Answer 42

hyperkalaemia (high K+) | hypokalaemia (Low K+)

Question 43

Treatment of acid-base imbalance

Answer 43

IV sodium bicarbonate 2.7% (especially useful if patient is volume deplete) IV furosemide (especially useful if patient is passing urine and is volume replete) Dialysis - if renal failure

Question 44

what is the treatment of metabolic alkalosis

Answer 44

IV sodium/potassium chloride

Question 45

What is the treatment of respiratory acidosis

Answer 45

Ventilation

Question 46

What is the treatment of respiratory alkalosis?

Answer 46

Breathing into a paper bag (hyperventilating patients)