Acid - Base, LFTs, Porphyrias

Question 1

Normal Ranges - pH

Answer 1

7.35-7.45

Question 2

Normal Ranges - Co2

Answer 2

4.7-6 kPa

Question 3

Normal Ranges - Bicarbonate

Answer 3

22-30 mmol/l

Question 4

Normal Ranges - O2

Answer 4

10 -13 kPa

Question 5

Steps to solve simple problems - Look at the case in this step by step way to determine the cause

Answer 5

1) pH - acidic or alkali?
2) CO2 - does it fit with the pH?
3) Bicarbonate - does it fit with the pH?
4) Compensation - is there any? Partial or Complete?

Question 6

Metabolic Acidosis

• pH?
• Bicarbonate?
• CO2?
• Causes?

Answer 6

• pH - low
• Bicarbonate - low
• CO2 - normal or low (if compensated)
• Causes - Lactate build up, DKA, Renal tubular

Question 7

Metabolic Alkalosis

• pH?
• Bicarbonate?
• CO2?
• Causes?

Answer 7

• pH - High
• Bicarbonate - High
• CO2 -normal/ High (If compensated)
• Causes - Pyloric Stenosis, Hypokalamia

Question 8

Respiratory Acidosis

• pH?
• Bicarbonate?
• CO2?
• Causes?

Answer 8

• pH - Low
• Bicarbonate - Normal/High (if compensated)
• CO2 - High
• Causes - Lung Injury - pneumonia, COPD, Decreased Ventilation

Question 9

Respiratory Alkalosis

• pH?
• Bicarbonate?
• CO2?
• Causes?

Answer 9

• pH - High
• Bicarbonate - Normal/ Low (if compensated)
• CO2 - Low
• Causes - Mechanical Ventilation, Anxiety/Panic attack

Question 10

what is compensation?

Answer 10

Return of pH towards normal at the expense of other values

Question 11

What is the Anion Gap?

Answer 11

(Na + K) - (Cl + HCO3)

Difference between total concentration of principal cations and principal anions = Concentration of unmeasured anions in the plasma

Question 12

What is the biggest contributor to the Anion Gap?

Answer 12

Almost entirely contributed by Albumin (beware in hypoalbuminaemia)

Question 13

Normal Range for the Anion Gap?

Answer 13

14-18 mmol/l

Question 14

Mnemonic for elevated anion gap metabolic acidosis?

KULT

Answer 14

K etoacidosis (DKA, alcoholic, starvation)
U raemia (renal failure)
L actic Acidosis
T oxins (ethylene glycol, methanol, paraldehyde, salicylate)

Question 15

Osmolar Gap- what is a normal osmolar gap?

Answer 15

Osmolality (measured) - Osmolarity (calculated)

Normal osmolar gap = less than 10

Question 16

What does an elevated osmolar gap suggest?

What does it differentiate?

Answer 16

An elevated osmolar gap provides indirect evidence for the presence of an abnormal solute.
it is increased by extra solutes in the plasma ( e.g. ethylene glycol, ethanol, methanol, mannitol)

Helpful in differentiating the cause of an elevated anion in metabolic acidosis

Question 17

Liver Function Tests - Markers of Liver Cell Damage

Answer 17

ALT
AST
ALK phos
GGT
Bilirubin

Question 18

Liver Function Tests - Markers of Synthetic Function

Answer 18

Clotting (INR)
Albumin
Glucose

Question 19

Aminotransferases - AST/ALT

• normal range?
• causes of high levels?
• ratio in Alcoholic liver disease?
• ratio in Viral liver disease?

Answer 19

• less than 40
• raised when hepatocytes die
• Alcoholic liver disease - 2:1
• Viral liver disease 1:1

Question 20

Alkaline Phosphatase (ALP)

• normal range?
• raised when?

Answer 20

• 30-150 iu/L

- Raised with cholestasis (either intrahepatic or extra hepatic) and bone disease, High in pregnancy

Question 21

Gamma GT (GGT)

• Normal range?
• When is it Elevated?

Answer 21

• 30-150 iu/L
• Elevated in chronic alcohol use
• Also bile duct disease and metastases. Used to confirm hepatic source of increased ALP

Question 22

What is Porphyrias?

Answer 22

7 Disorders caused by deficiency in enzymes, involved in haem biosynthesis, leading to build up of toxic haem precursors

Question 23

Acute Intermittent Porphyria (AIP)

• inheritance?
• deficiency?

Answer 23

Autosomal dominant inheritance

HMB (Hydroxymethybilane) synthase deficiency

Question 24

Acute Intermittent Porphyria (AIP)

- Symptoms?

Answer 24

Neuro-visceral only
- abdo pain, seizures, psych disturbances, nausea and vomiting, tachycardia, hypertension, sensory loss, muscle weakness, constipation, urinary incontinence,

NO cutaneous manifestations due to absence of porphyrinogens

Question 25

Acute Intermittent Porphyria (AIP) | - Diagnosis?

Answer 25

ALA + PBG in urine (Port wine urine)

Question 26

Acute Intermittent Porphyria (AIP) | - Precipitating Factors?

Answer 26

ALA synthase inducers (steroids, ethanol, barbiturates) Stress (infection, surgery) Reduced caloric intake and endocrine factors (eg premenstrual)

Question 27

Acute Intermittent Porphyria (AIP) | - Treatment?

Answer 27

Avoid precipitating factors, analgesia, IV carbohydrate/ haem arginate

Question 28

Acute porphyrias with skin lesions - 2 types? - inheritance? - Symptoms and clinical signs?

Answer 28

-Hereditary coproporphyria (HCP) and Variegate porphyria (VP) (these are 2 subtypes of porphyrias, have googled them and they both have the same sort of symptoms and signs, both have no treatment, although liver transplantation has been suggested) - Autosomal dominant - Neurovisceral + skin lesions - Raised porhyrins in faeces or urine

Question 29

Non-Acute porphyrias

Answer 29

Skin lesions ONLY - Congenital Erythopoietic porphyria (CEP) - Erythropoietic protoporphyria (EPP) - -Photosensitivity, burning, itching, oedema following sun exposure - Porphyria Cutanea Tarda (PCT)

Question 30

Porphyria Cutanea Tarda - inheritance? - deficiency? - symptoms? - diagnosis? - treatment?

Answer 30

- inherited/ acquired - Uroporphyrinogen decarboxylase deficiency - Cutaneous symptoms - Vesicles (crusitng, pigmented, superficial scarring) on sun exposed sites - Diagnosis - increased urinary uroporphyrins + coproporphyrins + increased ferritin - Treatment - avoid precipitants (alcohol, hepatic compromise), phlebotomy