Haemodynamic disorders

Question 1

Define Oedema.

Answer 1

Abnormal increase in interstitial fluid

Question 2

What three forces determine the movement of fluid between blood vessels and the interstitial space?

Answer 2

Capillary hydrostatic pressure
Plasma hydrostatic pressure
Plasma oncotic pressure

Question 3

What are the four broad causes of oedema?

Answer 3

Increased capillary hydrostatic pressure Decreased plasma oncotic pressure (e.g. nephrotic syndrome) Inflammation Lymphatic Obstruction

Question 4

What is a common cause of pulmonary oedema?

Answer 4

Increased plasma hydrostatic pressure in the pulmonary capillary bed
Left Ventricular Failure – build up of pressure in left atrium leading to back pressure into the capillaries – this pushes water into the tissues
This is cardiogenic pulmonary oedema

Question 5

What is non-cardiogenic pulmonary oedema?

Answer 5

Caused by increased permeability
ARDS – Acute Respiratory Distress Syndrome
Often caused by Sepsis, Shock and Trauma

Question 6

What are the four types of cerebral oedema?

Answer 6

Vasogenic – physical breakdown of the blood-brain barrier – commonly due to trauma or tumours
Interstitial – breakdown of the CSF-brain barrier – commonly due to obstruction of the flow of CSF (Obstructive Hydrocephalus)
Cytotoxic – derangement of the sodium-potassium pumps leads to a build up of intracellular sodium causing intracellular oedema (common with ischaemic strokes)
Osmotic – increase in plasma osmolality – commonly caused by Syndrome of inappropriate ADH secretion (SIADH) that is commonly caused by small cell lung cancer

Question 7

What are the possible serious consequences of cerebral oedema?

Answer 7

Rise in intracranial pressure, which could cause herniation

Question 8

What are two common causes of generalised oedema?

Answer 8

Left Ventricular Failure Nephrotic Syndrome

Question 9

What is a consequence of oedema in a peripheral setting?

Answer 9

Impaired wound healing

Question 10

What are the three main factors affecting thrombus formation?

Answer 10

Hypercoagulability
Vessel Wall Injury
Stasis

Question 11

What is cardiac thrombosis caused by and what is an important complication?

Answer 11

Stasis – e.g. atrial fibrillation

Complication – systemic embolisation

Question 12

What is arterial thrombosis caused by?

Answer 12

Vessel wall injury

Question 13

What is venous thrombosis caused by and what is an important complication?

Answer 13

Stasis and Hypercoagulability Complication – pulmonary embolism

Question 14

What are the four fates of a thrombus?

Answer 14

Propagation– thrombus accumulates fibrin and grows
Embolisation– thrombus dislodges and moves somewhere else
Dissolution– thrombus is dissolved by fibrinolytics
Organisation and Recanalisation– thrombus becomes fibrotic and is remodelled, lumen appears again allowing blood flow

Question 15

Where do most arterial thromboemboli originate?

Answer 15

Carotid arteries

Question 16

Define haematoma

Answer 16

A localised mass of extravasated blood that is relatively or completely confined within an organ or tissue

Question 17

What are the three classes of haemorrhage based on size?

Answer 17

Petechiae = 1-2mm 
Purpura = >3mm 
Ecchymoses = 1-2cm

Question 18

What is shock characterised by?

Answer 18

Hypotension

Question 19

What two equations are used to evaluate the effects of changes in various vascular factors?

Answer 19

MAP = CO x SVR 
CO = HR x SV

Question 20

What are the five types of shock?

Answer 20

Cardiogenic 
Hypovolaemic 
Anaphylactic 
Neurogenic 
Septic

Question 21

Describe each of the five types of shock and its causes and effects

Answer 21

Cardiogenic -impaired cardiac function, Causes include cardiac tamponade, Reduced SV

Hypovolaemic– loss of blood volume,
Causes include: trauma, haemorrhage Low SV leads to Low MAP Body tries to compensate with tachycardia

Anaphylactic– IgE mediated hypersensitivity, Causes vasodilation and increased permeability, Reduced SVR leads to Reducer MAP

Neurogenic– injury to sympathetic pathways, Normally happens after traum,a Widespread vasodilation and reduced SVR
Septic– result of inflammatory response, Causes vasodilation. Reduced SVR leads to Reduced MAP

Question 22

Define infarction.

Answer 22

Tissue necrosis due to unresolved ischaemia

Question 23

What are the two types of infarct and how are they different?

Answer 23

Red – haemorrhagic – affects organs with a dual blood supply
White – anaemic – affects solid organs that have one blood supply

Question 24

How can the rates of development of the occlusion affect the infarction?

Answer 24

If the occlusion develops slowly then there may be enough time for collateral vessels to form

Question 25

What are the two types of myocardial infarction?

Answer 25

Transmural – across the whole wall of the heart

Subendocardial – just the layer under the endocardium

Question 26

Describe the process of atherosclerosis.

Answer 26

1) Endothelial damage
2) Macrophage infiltration and release of cytokines
3) Cytokines recruit LDLs
4) LDLs become oxidised and hence become pro-inflammatory and drive progression of plaque
5) Smooth muscle cells migrate from the tunica media to the lesion and deposit a collagen-rich matrix, which forms a protective fibrous cap

Question 27

What are the two types of atherosclerotic plaque and how are they different?

Answer 27

Stable – thick fibrous cap – less likely to rupture

Unstable – thinner fibrous cap – more likely to rupture