Lecture 14: Regulating Flow, Coagulation and Peturbation of Flow

Question 1

Define active hyperaemia

Answer 1

Increased BV due to arteriolar dilation and expansion of the perfused capillary bed

Question 2

Define passive hyperaemia/ congestion

Answer 2

Increased blood volume within the vasculature of a tissue due to impairment of venous outflow

Question 3

What is another name for passive hyperaemia

Answer 3

Venous (passive) congestion

Question 4

Give examples for which active hyperaemia occur

Answer 4

Stomach when eating
Muscles when exercising
local inflammation
–> associated with increase tissue metal, O2 consumption

Question 5

Is the early response to injury active or passive hyperaemia??

Answer 5

Active –> facilitated by NO, prostaglandins

Question 6

Why is active hyperaemia localised??

Answer 6

Local mediators

There is insufficient blood vol to permit a generalised effect whilst maintaining systemic blood pressure!

Question 7

Give examples for which passive hyperaemia occurs

Answer 7

Rectal prolapse
Upstream of causal lesion e.g. bloat line
luminal obstruction of vein due to thumbs
intestinal strangulation - volvulus or torsion

Question 8

Can passive hyperaemia be localised?

Answer 8

Yes- e.g. bloat line

Question 9

Can passive hyperaemia be generalised?

Answer 9

Yes e.g. congestive heart failure –> severe generalised oedema

Question 10

where does the blood pool during left sided congestive heart failure

Answer 10

in the lungs

Question 11

what does the lung look like grossly during acute stage of left sided congestive heart failure

Answer 11

diffuse dark red/ purple
wet, rubbery
LUNGS DO NOT COLLAPSE WHEN U OPEN THE THORACIC CAVITY
foam surfactant in bronchioles/bronchi/trachea

Question 12

what does the lung look like grossly during chronic stage of left sided congestive heart failure

Answer 12

diffuse interstitial fibrosis –> palpable stiffness of lung
diffuse tan discolouration
may see some MO with heamosiderin in hits (engulf RBC)

Question 13

where does the blood pool during right sided congestive heart failure, where is it most obvious?

Answer 13

• cranial and caudal vena cave
• splanic viscera
• THE LIVER

Question 14

what does the liver look like grossly during acute stage of right sided congestive heart failure

Answer 14

swollen, dark red/purple
venous blood ooze from cut surface
hilar lymphatics distended

Question 15

what does the liver look like histologically during acute stage of right sided congestive heart failure

Answer 15

central vein and periacinar (zone 3) distended w/ blood

–> hydropic or fatty necrosis

Question 16

what does the liver look like grossly during chronic stage of right sided congestive heart failure

Answer 16

fibrosis
grossly obvious nutmeg liver pattern - zonal pattern
sinusoids dilated with blood

Question 17

what are the other consequences of right sided heart failure

Answer 17

hydrothorax
hydopericardium
congestion of spleen
congestion of kidney 
congestion of intestinal viscera 
ventral/dependent oedema

Question 18

what are the different gross appearances of congestion vs. hyperaemia

Answer 18

congestion - dark red/ purple cf. cyanotic

no associated increase in tissue temp

Question 19

what are the consequences of congestion

Answer 19

–> venous hypertension

local tissue hypoxia –> degeneration atrophy of parenchyma

Question 20

what is oedema

Answer 20

accumulation of excess body fluid

Question 21

what are the x5 major mechanisms of oedema formation

Answer 21

• increase plasma hydrostatic pressure
• decrease plasma colloid pressure
• lymphatic obstruction
• increase vascular permeability
• (sodium retention)

Question 22

what is an increased plasma hydrostatic pressure usually a consequence of?

Answer 22

venous hypertension

Question 23

how does venous hypertension result in increased plasma hydrostatic pressure

Answer 23

plasma hydrostatic pressure is capillary bed usually a reflection of capillary venous pressure
- increase in venous pressure is relayed upstream, negates the net absorptive pressure, fluid filtered out is failed to be reabsorbed

Question 24

why does systemic hypertension not result in oedema?

Answer 24

reflex = vasoconstriction, protect capillary beds

Question 25

what are some localised vs generalised causes of increased plasma hydrostatic pressure?

Answer 25

localised - local obstruction of venous flow ie/ occlusion of vein by thrombosis generalised - conditions of impaired VR to heart

Question 26

what is a decreased plasma colloid pressure usually referable to?

Answer 26

hypoalbuminea

Question 27

how low must serum albumin be before hypoalbuminea?

Answer 27

<10-15g/L

Question 28

what are the most common causes of hypoalbuminea?

Answer 28

- decreased hepatic synthesis; malnutrition/starvation, chronic hepatic insufficiency - loss of protein: severe burns, protein losing enteropathy,

Question 29

is the oedema caused by hypoalbuminmia likely to be localised or generalised and why

Answer 29

GENERALISED --> lose protein from everywhere decrease plasma colloid pressure --> net movement of fluid into interstitum --> decrease effective circulating blood volume --> RAAS activated --> retention of Na, --> exacerbation of oedema

Question 30

is lymphatic obstruction causing oedema normally localised or generalised?

Answer 30

localised

Question 31

name 3 things that can obstruct lymph vessels

Answer 31

- parasite - lymphangitis - trauma

Question 32

is oedema caused by an increase in vascular permeability normally localised or generalised?

Answer 32

localised to the cause of inflammation

Question 33

what is the clinical significance of oedema

Answer 33

- impaired wound healing - secondary bacterial infections - fibroplasia and permanent fibrosis

Question 34

what are two life threatening locations to have oedema?

Answer 34

- cerebral | - pulmonary

Question 35

what are the references for transudate, modified and exudate oedema?

Answer 35

transudate: <25 protein, <1.5x10^9 cells modified: 25-75 protein, 1.0-7.0x10^9 cells exudate: >30 protein, >7.0x10^9 cells