Cyanosis

Question 1

Definition of central cyanosis?

Answer 1

Due to reduction of o2 saturation in blood (centrally blue)
- Requires >5g/dL deoxygenated Hb for cyanosis to be visible to the eye
- Fingernails blue + mouth blue
- Features of chronic hypoxemia: clubbing, polycythemia
- Cyanosis does not improve on warming of peripheries

Question 2

Definition of peripheral cyanosis

Answer 2

Due to peripheral vasoconstriction
-> leads to sluggish blood flow
-> slower blood flow allows more time for tissues to extract o2 from Hb
-> fingernails blue BUT NORMAL O2 saturation (centrally PINK)
- Cyanosis improves on warming of peripheries
- Absence of chronic hypoxemia

Question 3

Conditions that can alter presentation of cyanosis

Answer 3

Anemia
Polycythemia

Question 4

Signs of chronic hypoxemia

Answer 4

Clubbing
Polycythemia

Question 5

Causes of central cyanosis

Answer 5

1. Cardiac (5Ts)
   - Tetralogy of fallot (most common)
   - Transposition of great vessels
   - Truncus arteriosus
   - Tricuspid atresia
   - Total anomalous pulmonary venous return
2. Respiratory
   - Lobar pneumonia
   - Bronchiectasis
   - ILD

Question 6

Pathophysiology of hypercyanotic spell

Answer 6

Crying increases intrathoracic pressure
-> increases pulmonary pressure (pulmonary circulation is located within thoracic cavity)
-> increase pulmonary pressure in addition to RVOTO (PS)
-> decrease in pulmonary blood flow + increase deoxygenated blood will shunt through VSD into aorta
-> worsening hypoxia
-> hypoxemia will increase anaerobic respiration
-> lactate produced as by-product
-> lactic acidosis
-> increase in pulmonary vascular resistance

Question 7

Management of hypercyanotic spells

Answer 7

1. Calm
2. Squat/knees to chest position
   - kinks femoral arteries to increase systemic vascular resistance
   - promote blood flow into pulmonary circulation instead of aorta
3. Oxygen
   - increase pulmonary vasodilation (decrease PVR)
4. IV morphine
   - sedation
5. IV beta blockers
   - slows heart rate for longer diastolic filling time for more volume to be ejected into pulmonary artery

Question 8

What is transposition of great arteries?

Answer 8

Normally:
RV -> Pulmonary trunk
LV -> Aorta

In TGA:
RV -> Aorta
LV -> Pulmonary trunk

Question 9

Management of TGA

Answer 9

Aim: Enable oxygenated blood from left heart to enter right heart (be it at the atrial or ventricular level)

• IV prostaglandin to maintain patency of DA
• Balloon atrial septostomy (if foramen ovale is too small)
  -> creates ‘ASD’ to help shunt oxygenated blood into systemic circulation