Acid base handling and diabetes cases

Question 1

How is H+ removed in the body?

Answer 1

Kidneys (+ bicarbonate reabsorption)

Question 2

How is CO2 removed from the body?

Answer 2

In the lungs

Question 3

Why would a patient with acidosis be unconscious?

Answer 3

Enzymes in brain become denatured at acidic pH

Question 4

What are the 3 buffering systems for H+ in the body?

Answer 4

1. Bicarbonate
   HCO3- (+) H+ -> H2Co3
2. Haemoglobin
   Hb (+) H+ -> HHb
3. Phosphate
   HPO4 (+) H+ -> H2P04

Question 5

How do you calculate osmolality? Why we do measure it like this?

Answer 5

Osmolality = charged molecules + uncharged molecules

= cations + anions + urea + glucose

Therefore

= 2(Na + K) + U + G

(don’t know how much cations there are, but we do know how many cations. Cations = anions in our body, therefore we multiply cations by 2 to include anions)

Question 6

What is the anion gap?

Answer 6

Basically the anions that we can’t measure, the ones apart from chloride and bicarbonate.

Normally 16-20

Question 7

How do you calculate the anion gap?

Answer 7

Na + K - Cl - Bicarb

Question 8

What is a top differential for a patient with metabolic acidosis with a high anion gap?

Answer 8

Type 1 diabates, diabetic ketoacidosis

ketones are increased and therefore increase anion gap

Question 9

Why do you get respiratory alkalosis in a patient with an anxiety attack?

Answer 9

Rapid breathing, removes more CO2 from body.

Blood become less acidic, pH rises.

As pH rises, Ca+ outcompetes with H+ for albumin.

Then you get less biologically active Ca+ = cause symptoms of hypocalcaemia (tetany) and cause more anxiety for patient

Question 10

What is hyperglycaemic hyperosmolar state?

Answer 10

Type 2 diabetic (undiagnosed)

Patient becomes dehydrated and has sugary drink.

Glucose in drink further worsens thirst and urine.

Gets worse and worse until sodium is very high.

Becomes unconscious as a result of severe dehydration

Metabolic acidosis

Question 11

What causes a high anion gap?

Answer 11

Ketones
Methanol
Ethanol
Lactate

Question 12

How can metformin cause increased lactate?

Answer 12

Metformin inhibits the conversion of lactate to glucose in the liver (gluconeogenesis)

Question 13

What is the definition of Type 2 Diabetes

Answer 13

1. Fasting plasma glucose of >7
2. Plasma glucose during Glucose tolerance test > 11.1 at 2 hours

Ether of these count

(GTT value between 7.8 - 11.1. = impaired glucose tolerance)

3. HBA1C >48mmol = diabetes (newer definition)

Question 14

What are normal ranges for:

1. Sodium
2. Potassium
3. Urea
4. Creatinine

Answer 14

1. Na = 133 - 146mmol/L
2. K = 3.5 - 5.3mmol/L
3. Urea = 2.5 - 7.8 mmol/L
4. Creatinine:
   - Male = 59 - 104 umol/L
   - Female = 45 - 84 umol/L

Question 15

What are causes of metabolic acidosis?

Answer 15

Increased H+ Production

• > Diabetic Ketoacidosis
• > Lactic Acidosis
• > Salicylate (Aspirin) OD, ringing noise in ears.

Decreased H+ excretion

• > Renal Tubular Acidosis
• > Renal Failure

Hyperkalaemia

Question 16

What are causes of Respiratory Acidosis?

Answer 16

Lungs retaining CO2

• > Decreased Ventilation
• > Poor lung perfusion
• > Impaired gas exchange

Question 17

What are causes of Metabolic Alkalosis?

Answer 17

H+ Loss
-> Vomiting

Ingestion of bicarbonates
-> OD on Antacids

Hypokalaemia

• > k+ is used in the Na/K ATPase pump to excrete H+
• > Lack of K+, sends the Pump into overdrive, increasing the amount of extracellular Na+ thus excreting extra H+

Question 18

What are causes of Respiratory Alkalosis?

Answer 18

Voluntary - Anxiety
Artificial Ventilation
Stimulation of respiratory centre i.e. some drugs