Cyanosis

Question 1

Define cyanosis

Answer 1

bluish discoloration of the skin and mucous membranes.

Question 2

why does cyanosis occur

Answer 2

Due to increased amount of deoxygenated HB in RBCs

Question 3

Define central cyanosis

Answer 3

desaturation of arterial blood or the presence of a Hb derivative.

Question 4

Define peripheral cyanosis

Answer 4

desaturation of blood due to a regional reduction in blood flow

Question 5

At what % of oxygen saturation of Hb does cyanosis become visible

Answer 5

80% or less

Question 6

Define arterial hypoaemia

Answer 6

PAO2 is below normal (85-100mmHg)

Question 7

If you have a cyanotic animal what is the first thing you should do

Answer 7

provide oxygen

Question 8

what is the main cause of cyanosis

Answer 8

Resp tract disease:
1. URT disease
2. Lung disease
3. Pleural space disease

Question 9

List 5 causes of central cyanosis

Answer 9

no oxygen available
oxygen can’t get to the lungs
oxygen can’t get to the blood
reduced systemic oxygen
oxygen can’t bind to the Hb

Question 10

List 2 things that can cause no O2 to be avaliable

Answer 10

altitude
O2 source failure

Question 11

List 4 things that can cause O2 to be unable to get into the lungs

Answer 11

chest damage
muscle damage
URT obstruction
pleural space disease

Question 12

List 3 things that can cause O2 to be unable to get into the blood

Answer 12

interstitial lung disease
diffuse alveolar disease
ventilation-perfusion mismatch

Question 13

what can cause a reduced systemic oxygen

Answer 13

R to L shunting - intracardiac or extracardiac

Question 14

what can cause oxygen to be unable to bind to Hb

Answer 14

haemoglobinopathy

Question 15

List 3 intracardiac causes of R to L shunting

Answer 15

tetralogy of fallot
ASD/VSD with concurrent pulmonic stenosis
pulmonary hypertension

Question 16

List 3 extracardiac causes of R to L shunting

Answer 16

reversed patent ductus arteriosus
pulmonary arteriovenous fistulas
lung lobe consolidation

Question 17

List 6 causes of peripheral cyanosis

Answer 17

central cyanosis
decreased arterial supply
peripheral vasoconstriction
arterial thromboembolism
low cardiac output
obstruction of venous drainage

Question 18

Describe how to diagnose the cause of cyanosis

Answer 18

clinical history
observe respiration and mucous membranes
palpate extremities
chest wall and apex beat
auscultate heart and lungs
neurological exam

Question 19

Describe how to manage a cyanotic patient

Answer 19

provide immediate O2 and then treat the cause

Question 20

What is the tetralogy of fallot

Answer 20

complex congenital heart disease composed of 4 specific features
In these cases blood shunts from right to left, the proportion of which is determined by the severity of the defects, and hence the severity of the clinical signs.

Question 21

List the 4 features in tetralogy of fallot

Answer 21

1. Pulmonic stenosis
2. Ventricular septal defect
3. Over-riding aorta
4. Right ventricular hypertrophy and dilation

Question 22

Define polycythaemia

Answer 22

presence of an abnormally large number of erythrocytes in the blood

Question 23

Describe how to control polycythaemia

Answer 23

regular blood letting - via phlebotomy or leeches,
chemotherapy