Investigations

Question 1

What is the formula for arterial blood gas?

Answer 1

CO2 + H2O H2CO3 H+ + HCO3-

Question 2

Who should have an ABG?

Answer 2

Critically unwell
Unexpected/inappropriate hyperaemia (sats <94%)
Deteriorating sats or inc SOB
Deteriorating pt now needing O2 to maintain sats
Risk of hypercapnic resp failure
SOB & risk of metabolic condition
Poor peripheral circulation sats cannot be obtained
Any other evidence ABG would be useful

Question 3

What are the risks associated with an ABG?

Answer 3

Nerve injury
Digital ischaemia
Infection
Bleeding & haematoma
Pseudoaneurysm
AV fistula
Injury to staff

Question 4

What parameters show respiratory acidosis?

Answer 4

pH: Low
PaCO2: High

Question 5

What parameters show respiratory alkalosis?

Answer 5

pH: High
PaCO2: Low

Question 6

What parameters show metabolic acidosis?

Answer 6

pH: Low

HCO3-: Low

Question 7

What parameters show metabolic alkalosis?

Answer 7

pH: High

HCO3-: High

Question 8

What are the causes of respiratory acidosis?

Answer 8

Hypoventilation
CNS depression (drugs, narcotics, sedatives)
Dec chest wall movement (NM disorders, myasthenia, tension PT, upper airway obstruction)
COPD
Asthma attack

Question 9

What are the causes of respiratory alkalosis?

Answer 9

Stimulated resp drive
Hyper metabolic state (sepsis, pregnancy, thyrotoxicosis)
Hyperventilation
Hyperthermia
Drugs (aspirin, OD, progesterone)
Hypoxaemia (PE, pneumonia, altitude, PO, asthma attack)
Liver failure

Question 10

What are the causes of metabolic acidosis?

Answer 10

Increased anion gap: New acid added (OH-, uraemia, DKA, lactate, iron, salicylate)
Normal anion gap: retaining H+/loosing HCO3-, diarrhoea, Addison’s, RTA
Low anion gap: Li toxicity, hyperCa, hyperMg, HyperK, multiple myeloma

Question 11

What are the causes of metabolic alkalosis?

Answer 11

Acid loss
Chloride responsive (D&V, corticosteroids)
Chloride resistant (hyperaldosteronism, Cushing's, hypoK)

Question 12

How is hydration status assessed?

Answer 12

Hands: Temp, (collapsing) pulse, L&S BP, CRT
Head & neck: Sunken eyes, JVP, mucus membranes, carotid vol & character
Sternum: CRT, skin turgor, apex beat, auscultate heart&lung bases
Abdo: Ascites
Legs: Oedema
Extra: Weight, U&Es, Catheter, ABG&lactate

Question 13

What can the colour of a urine sample mean?

Answer 13

Straw yellow- Normal
Dark- Bile pigments due to dehydration
Red- Haematuria, menstrual blood, food (beetroot & blackberries)
Green/blue- Pseudomonal UTI, triamterene (K sparing diuretic), asparagus
Orange- Dehydration (bile pigments), phenothiazines, carrots

Question 14

What can frothy urine be indication of?

Answer 14

Proteinuria

Question 15

What are the causes of haematuria?

Answer 15

Menstrual bleeding- MOST COMMON
Trauma
Prostate/urological exam
Exercise induced
Dehydration
Glomerular/tubular pathology

Question 16

What are the causes of proteinuria?

Answer 16

Transient: congestive heart failure in elderly
Intermittent: Asymptomatic as a result of prolonged vertical posture, exposure to cold, pregnancy and hypertension.
Persistent: Glomerular underlying disease, DM, myeloma, hypertension, connective tissue disease

Question 17

What are the causes of glycosuria

Answer 17

Diabetes
Cushing’s syndrome
Liver and pancreatic disease
Fanconi’s syndrome

Question 18

What are the causes of ketones in the urine?

Answer 18

Pregnancy
Diabetes
Starvation/rapid weight loss

Question 19

What are the causes of urobilogen/bilirubin in the urine?

Answer 19

No bilirubin in normal urine

Conjugated: Liver disease, BDobstruction

Question 20

What is the diagnosis for someone with:
Urea ++
Creatinine ++
Sodium +
Potassium- Normal

Answer 20

Renal failure

Causes: Chronic renal failure, DM, hyperT, Pyelonephritis / glomerulonephritis

Question 21

What is the diagnosis for someone with:
Sodium +
Potassium -
Creatinine- Normal
Urea- Normal
Associated: Hypertension

Answer 21

Hyperaldosteronism (Conn’s Syndrome)

Aldosterone causes the retention of sodium at the expense of potassium. It acts on the PCT causing the synthesis of more Na+/K+ exchange channels. Thus, in thepresence of excess of aldosterone there will be excess secretion of K+, and retention of Na+. The retention of Na+ will cause a secondary retention of water, resulting in hypertension.

Question 22

What is normal urine output for an adult?

Answer 22

> 0.5mL/Kg/hr

Question 23

What are the indications for a lumbar puncture?

Answer 23

• Infection: Meningeal, encephalitis, TB, Strep, Herpes
• Bleeding into the CSF: Sub-arachnoid
• Inflammation of brain/SC/CSF: Multiple Sclerosis

Question 24

What are the contraindications for a lumbar puncture?

Answer 24

• RAISED INTRACRANIAL PRESSURE
• No consent
• Coagulopathy
• Local infection at needle site

Question 25

Why is an LP not performed with raised ICP? | What is the one exception to this rule?

Answer 25

By removing fluid from the spinal canal, you lower the pressure in this area. The high pressure within the cranium may then cause herniation of the brainstem through the foramen magnum. Benign raised ICP- usually young women without symptoms (headache, impaired consciousness, dec pulse & BP)

Question 26

What are the complications of an LP?

Answer 26

- Headache: Very common - Paraesthesia - Permenant nerve damage: SERIOUS

Question 27

What are the normal LP values?

Answer 27

``` Protein 40g/dl Cell count <4-5 Red cell count – depends on how much blood was lost during the procedure! Pressure <20cm Glucose 2/3 of serum glucose ```

Question 28

How is a potential PE investigated?

Answer 28

Wells Score >2 = LIKELY CTPA Wells Score <2 = UNLIKELY D-dimer D-dimer +ve= CTPA D-dimer -ve= No more investigations

Question 29

What is a normal score on a D-dimer? Is it a good test?

Answer 29

<50 | Sensitive but not specific

Question 30

When should a cardiac troponin be carried out?

Answer 30

6hours after the onset of pain Then 3hourly Check local guidelines

Question 31

What are the 2 types of lactic acidosis?

Answer 31

Type 1: Hypoxic, produce too much lactic acid. DKA, starvation, CV/R depression Type 2: Non-hypoxic, cannot breakdown lactic acid Secondary to Metformin/ poisoning

Question 32

What is cardiac output a function of?

Answer 32

Preload Afterload Contractility

Question 33

What are the parameters in an LP for bacterial, viral and TB meningitis?

Answer 33

B: Cloudy/Turbid, ↑neutrophils, ↑protein, ↓ glucose, ↑ pressure V: Clear, ↑ lymphocytes, normal protein, normal glucose, normal pressure TB: Normal/slightly cloudy, ↑ lymphocytes, ↑↑protein, ↓↓ glucose