Definitions

Question 1

What is CT?

Answer 1

Coupled rotational source + detector; tangential beams across body to target specific structures, whereby beam rotates and patient advances through scanner.

Question 2

What is contrast?

Answer 2

Exogenous agents that are radiodense and usually iodine-based. Administered at time convenient to scan to fit perfusion phase of structure

Question 3

What are Hounsfield units?

Answer 3

Quantitative measure of radiodensity to differentiate structures on CT.

Question 4

What units are used to differentiate radiodensity of structures on CT? What are the limits of these?

Answer 4

Hounsfield units
-1000 = air
0 = water
+3000 = bone

Question 5

What unit is the measure for radiation dose?

Answer 5

Gray - mGy.

Question 6

What is the usual ionizing background radiation known as?

Answer 6

Sievert (SV)

Question 7

What is clinical ultrasound?

Answer 7

Oscillating waves of frequency outside range for human hearing

Question 8

What is the frequency of diagnostic ultrasound?

Answer 8

1-18Hz

Question 9

What is the Doppler effect/shift?

Answer 9

Change in frequency of wave for observer moving relative to source

Question 10

What is Addison’s Disease?

Answer 10

Failure of adrenal glands to produce sufficient glucocorticoid hormones (and often also mineralocorticoid) due to immune destruction of adrenal cortex by autoantibodies

Question 11

What is cardiopulmonary exercise testing?

Answer 11

Non-invasive simultaneous measurement of CV and respiratory system during exercise to assess capacity and by proxy fitness for elective surgery

Question 12

What is VO2Max?

Answer 12

Max rate of O2 consumption

Question 13

What is a phaeochromoctyoma?

Answer 13

Catecholamine producing tumour derived from chromaffin cells of adrenal medulla

Question 14

What is pulse oximetry?

Answer 14

Light source LED and photodetector - 2 wavelengths of light emitted which pass through tissue (red visible/infrared) and absorbed by oxy and deoxyHb

Question 15

What is the Hering-Breur reflex?

Answer 15

When lung inflated, stretch receptors in airways send vagal impulses to respiratory neurones in response to tidal volume over 800ml (during exercise) - this shortens inspiratory time and so increases respiratory rate

Question 16

What reflex speeds up respiratory rate in response to increased tidal volume? How does it work?

Answer 16

Hering-Breur reflex - via vagus nerve triggered by stretch receptors in lungs

Question 17

What are inotropes? How do they work generally?

Answer 17

Agents which affect contractility of myocardium via increasing intracellular Ca levels

Question 18

What is transplantation?

Answer 18

Transposition of tissue from one anatomical region to another

Question 19

What is allograft?

Answer 19

Organ or tissue from one non-related individual to another of same species

Question 20

Organ or tissue from one non-related individual to another of same species?

Answer 20

Allograft

Question 21

What is isograft?

Answer 21

Organ or tissue from a genetically identical individual

Question 22

Organ or tissue from a genetically identical individual?

Answer 22

Isograft

Question 23

What is autograft?

Answer 23

Organ or tissue from same individual to different site

Question 24

Organ or tissue from same individual to different site?

Answer 24

Autograft

Question 25

What is xenograft?

Answer 25

Organ or tissue from different species

Question 26

Organ or tissue from different species?

Answer 26

Xenograft

Question 27

What is HLA? What are the main subtypes?

Answer 27

Human leucocyte antigen - protein expressed on all tissue, forming basis of immune system. MHC 1 = A, B and C, MHC2 = DR (also DP and DQ)

Question 28

What is the central role of HLA?

Answer 28

Identifying tissues as ‘self’ by immune system

Question 29

What equation is used to calculate bicarbonate from known parameters on ABG?

Answer 29

Henderson-Hasselbach

Question 30

What is cryoprecipitate? What are the 5 constituents?

Answer 30

Blood product obtained by centrifugation of plasma, containing: fibrinogen, fibronectin, factor 8, factor 13 and vWF

Question 31

What is primary haemorrhage in tonsillectomy?

Answer 31

Haemorrhage as direct result of primary vascular injury or clot dislodgement

Question 32

What is secondary haemorrhage in tonsillectomy?

Answer 32

Delayed 7-14 days post-op, due to infection and sloughing of vascular walls

Question 33

What is an open fracture?

Answer 33

Disruption of bony cortex in association with breach in overlying skin and/or viscera

Question 34

What is neurogenic shock?

Answer 34

Form of distributive shock characterised by hypotension due to loss of systemic vascular resistance due to sympathetic outflow tract damage, usually following spinal cord injury

Question 35

What defines a massive haemothorax?

Answer 35

Draining over 1500ml of blood on insertion of chest drain, or 200ml per hour for at least 4 hours (or one third of patient’s circulating volume)

Question 36

What is a tension pneumothorax? What causes it?

Answer 36

Pneumothorax in association with shock resulting in shift of midline structures (tracheal deviation). Due to positive pressure in pneumothorax throughout respiratory cycle - one way valve into intrapleural space.

Question 37

What is haemoglobin?

Answer 37

Globular protein consisting of one haem moiety (ferrous ion plus protoporphyrin ring) and globin chain (in adults 2 alpha and 2 beta)

Question 38

What is the oxygen dissociation curve?

Answer 38

Describes relationship between percentage of saturated Hb and partial pressure of oxygen in blood

Question 39

What is Courvoisier’s Law?

Answer 39

States that a distended palpable gallbladder in presence of jaundice is unlikely to be gallstones, because chronic inflammation due to gallstones causes wall thickening/fibrosis which precludes distension