ABGs

Question 1

Which of the two systems is the most powerful compensator of metabolic inbalances?

Answer 1

Metabolic

Question 2

What is the normal pH range?

Answer 2

7.35-7.45

Question 3

At what level does the optimal level of acid/base dissociation occur?

Answer 3

K

Question 4

Why is the bicarbonate the main buffer system in the body?

Answer 4

There is dual control via volatile gas (CO2) and renal control of bicarb and H+

Question 5

Name 5 other buffers in the body

NB - 3 main categories

Answer 5

BBS, Hb, intracellular protein, plasma proteins, phosphate,

Question 6

What is the Henderson-Hasselback equation?

Answer 6

pH = pKa (6.37) + logHCO3-/0.03xpCO2

Question 7

How do you work out HCO3 levels?

Answer 7

Derive from HH equation, you can’t get it from the ABG directly.

Question 8

What is the base excess?

Answer 8

amount of moles os stron acid required to back titrate 1 litre of blood to correct pH….finish…

Question 9

Normal pCO2 levels?

Answer 9

4.5 - 5.8kPa

Question 10

Normal pO2 levels?

Answer 10

11-13 kPa

Question 11

Normaly HCO3- levels

Answer 11

22-28

Question 12

Normal base excess?

Answer 12

-2 to +2 mmol/L

Question 13

Normal anion gap?

Answer 13

10-14

Question 14

Normal chloride levels?

Answer 14

98-107

Question 15

Name 2 potential causes of a primary respiratory alkalosis?

Answer 15

PE, pneumonia

Question 16

What are normal Na+ levels?

Answer 16

135-145

Question 17

What is main cause of primary metabolic alkalosis?

Answer 17

Loss of acid in vomiting

Question 18

What is the anion gap? And which anions are the cause of it?

Answer 18

The unmeasured anion gap
(because blood tests measure most cations but only a few anions)
Na+ - (Cl- + HCO3-)
The unmeasured anions are intracellular (and??)

Question 19

How do you correct the anion gap for albumin?

Answer 19

Corrected AG = AG + [0.25 x (40 - [alb])]

Question 20

CAUSES of high AG metabolic acidosis

Answer 20

…

Question 21

Normal causes normal AG metabolic acidosis

Answer 21

….

Question 22

When would you look at the anion gap?

Answer 22

If the patient is acidotic but CO2 seems to be normal ?

Question 23

Why does someone who is bicarb wasting have a normal anion gap?

Answer 23

Bicarb wasting

Question 24

How long does respiratory compensation take?

Answer 24

Begin in minutes, complete in 12-24 hours

Question 25

What are the two components of metabolic acidosis?

Answer 25

Cellular and renal

Question 26

How long does cellular compensation take?

Answer 26

Minutes to hours

Question 27

How long does renal compensate take?

Answer 27

3-5 days

Question 28

What is the alveolar-arterial gradient?

Answer 28

The difference between the calculated pO2 and the measured arterial pO2.

Question 29

What is arterial pO2?

Answer 29

Function of ventilation and fractional inspired concentration of O2 (FiO2)

Question 30

What is the A-a gradient affected by? (3)

Answer 30

Altitude Inspired oxygen percentage Rate of respiration

Question 31

What are the causes of hypoxia with a normal A-a gradient?

Answer 31

Hypoventilation | Subnormal PiO2

Question 32

What are the causes of hypoxia with a raised A-a gradient?

Answer 32

V/Q mismatch Shunt Dead space Low cardiac output states

Question 33

Why can't a shunt be corrected with 100% oxygen?

Answer 33

The alveoli units are STILL not being perfused. The same fraction of deoxygenated blood continues to circulate the system.

Question 34

What is carpo-pedal spasm? | 2 signs?

Answer 34

....?? | Acutely hypocalcaemic signs due to increasingly negative charge due to hypocapnia

Question 35

Why is breathing into a paper bag helpful for those hyperventilating?

Answer 35

They rebreathe their own CO2, reduces their hypocapnia

Question 36

When should you be considering A-a gradient?

Answer 36

Hypoxia

Question 37

What is the most common ECG finding for a PE?

Answer 37

Sinus tachycardia

Question 38

What are normal potassium levels?

Answer 38

3.5-5 mmol/L

Question 39

Normal creatinine levels?

Answer 39

70 - 150 micromol/L

Question 40

Normal urea levels?

Answer 40

2.5 - 6.7 mmol/L

Question 41

Normal eGFR?

Answer 41

> 90

Question 42

What are the biggest risks when plasma electrolytes are dangerously abnormal? (2 main categories)

Answer 42

``` Cardiac arrhythmias CNS events (eg seizures) ```

Question 43

When should you be REALLY worried about Na+ levels?

Answer 43

155 mmol/L

Question 44

When should you be REALLY worried about K+ levels?

Answer 44

6.5 mmol/L

Question 45

When should you be REALLY worried about Ca+ levels? (corrected)

Answer 45

3.5 mmol/L

Question 46

When should you be REALLY worried about glucose levels?

Answer 46

20 mmol/L

Question 47

When is hypoxia severe?

Answer 47

<8.0kPa

Question 48

When is pH dangerously acidotic?

Answer 48

<7.1

Question 49

When are haemoglobin levels dangerously low?

Answer 49

<70g/l

Question 50

When are platelets dangerously low?

Answer 50

< 40x10^9/L

Question 51

What concentration of neutrophils would you expect in meningitis?

Answer 51

>1 neutrophil/ mm^3

Question 52

What biochemical features would you find in dehydration? (3) | And two other features of patient?

Answer 52

``` Incr urea (moreso than creatinine) Incr albumin Incr haemocrit Decr urine volume Decr skin turgor ```

Question 53

What are the two major biochemical pictures of abnormal kidney function?

Answer 53

Low GFR | Tubular dysfunction

Question 54

How does low GFR appear biochemically?

Answer 54

``` Incr urea Incr creatine Incr K+ Incr H+ Incr urate Incr phosphate Incr anion gap ``` Mem aid CHUK A PU (up) Decr Bicarbonate, urine output (oligouria)

Question 55

What are the causes of low GFR?

Answer 55

Early acute oliguric renal failure | Chronic kidney disease

Question 56

If low GFR is caused by chronic kidney disease, what else is found biochemically?

Answer 56

Decr Hb Incr PTH Renal bone disease