Differential Cyanosis
Differential Cyanosis
Differential Cyanosis – Quick 10 MCQ Quiz
Classic vs reverse patterns, neonatal screening, and key associations.
1) Differential cyanosis means:
Explanation
Differential cyanosis refers to selective cyanosis in some parts (e.g., lower limbs) while others remain pink.
2) Classic differential cyanosis (pink upper limbs, blue lower limbs) occurs in:
Explanation
In PDA with Eisenmenger, desaturated blood from the pulmonary artery enters the descending aorta beyond the left subclavian, leading to cyanosis in lower limbs but not upper.
3) Reverse differential cyanosis (blue upper limbs, pink lower limbs) occurs in:
Explanation
In TGA with PDA and suprasystemic PA pressures, desaturated blood preferentially supplies the upper body while oxygenated blood enters the descending aorta.
4) Which site is considered pre-ductal for oxygen saturation measurement?
Explanation
The right hand is supplied by the brachiocephalic artery proximal to the ductus arteriosus and is considered pre-ductal.
5) Which site is considered post-ductal for oxygen saturation measurement?
Explanation
Blood in the descending aorta (e.g., right foot) may be influenced by ductal shunting, thus post-ductal.
6) In Eisenmenger PDA, cyanosis is seen in:
Explanation
Because the PDA enters the descending aorta beyond the left subclavian, lower limbs are cyanosed while upper limbs remain pink.
7) Reverse differential cyanosis is most typical of:
Explanation
Reverse differential cyanosis occurs when desaturated blood preferentially flows to upper body while relatively oxygenated blood goes to descending aorta.
8) Which is a non-cardiac cause of differential cyanosis?
Explanation
Dissection involving arch vessels can lead to differences in perfusion and oxygenation between upper and lower limbs.
9) A newborn has SpOâ‚‚: right hand 95%, right foot 78%. This suggests:
Explanation
Higher pre-ductal (hand) saturation vs lower post-ductal (foot) saturation = classic differential cyanosis.
10) A newborn has SpOâ‚‚: right hand 78%, right foot 95%. This suggests:
Explanation
Lower pre-ductal (hand) vs higher post-ductal (foot) saturation indicates reverse differential cyanosis.
📌 Definition
Differential cyanosis = Presence of cyanosis (bluish discoloration) in some parts of the body but not others, due to selective desaturation of blood in different vascular beds.
🟦 Types of Differential Cyanosis
| Type | Description | Classical Cause(s) |
|---|---|---|
| Classic Differential Cyanosis | Lower limbs are cyanotic, upper limbs are pink | Patent ductus arteriosus (PDA) with Eisenmenger physiology (reversal of shunt → deoxygenated blood enters descending aorta beyond left subclavian) |
| Reverse Differential Cyanosis | Upper limbs cyanotic, lower limbs pink | Transposition of great arteries (TGA) with PDA and pulmonary hypertension (deoxygenated blood enters aortic arch supplying head/upper limbs, while oxygenated blood preferentially flows to descending aorta) |
| Upper vs Lower Body Cyanosis in Adults | Cyanosis confined to lower limbs (esp. toes) but not fingers | Severe aortic pathologies like coarctation with PDA or aortic dissection with branch involvement |
| Peripheral vs Central Cyanosis | Peripheral: cyanosis at extremities only; Central: lips, tongue, mucosa cyanosed | Peripheral: low output, shock, vasoconstriction; Central: hypoxemia, right-to-left shunt |
🟨 Differential Cyanosis – Key Clinical Points
- Classic differential cyanosis: Pink fingers + blue toes = PDA with Eisenmenger.
- Reverse differential cyanosis: Blue fingers + pink toes = TGA with PDA + pulmonary HTN (also seen in suprasystemic PAH with PDA).
- Oxygen saturation measurement (pre-ductal vs post-ductal) is crucial in neonates (right hand vs foot).
- Important in neonatal congenital heart disease screening.
Summary Table: Differential Cyanosis
| Type | Description | Causes |
|---|---|---|
| Classic Differential Cyanosis | Upper limbs pink, lower limbs cyanosed | PDA with Eisenmenger (R→L shunt into descending aorta) |
| Reverse Differential Cyanosis | Upper limbs cyanosed, lower limbs pink | TGA with PDA + severe pulmonary HTN (oxygenated blood preferentially reaches descending aorta) |
| Pre-ductal Saturation | Right hand saturation (before duct insertion) | Represents blood supply from proximal aorta/arch |
| Post-ductal Saturation | Lower limb saturation (after duct insertion) | Represents mixed blood from PDA |
| Other Causes | Cyanosis confined to lower limbs | Coarctation of aorta with PDA, Aortic dissection involving arch vessels |
Differential Cyanosis
Fact Summary: Differential Cyanosis
- Differential cyanosis = difference in oxygen saturation between upper and lower limbs.
- Classic form: upper limbs pink, lower limbs cyanosed.
- Cause of classic type: PDA with Eisenmenger’s physiology (R→L shunt into descending aorta).
- Reverse form: upper limbs cyanosed, lower limbs pink.
- Cause of reverse type: TGA with PDA + severe pulmonary hypertension.
- Right upper limb (pre-ductal) reflects blood before duct insertion.
- Lower limb (post-ductal) reflects blood after duct mixing.
- Pre-ductal vs. post-ductal saturation difference helps diagnose duct-dependent lesions.
- Pulse oximetry on right hand and foot is a standard screening method.
- Classic differential cyanosis is rare but specific for PDA with reversal.
- Reverse differential cyanosis is more often seen in TGA physiology.
- In TGA, oxygenated blood from LV through PDA preferentially enters descending aorta → pink lower limbs.
- Upper limbs cyanosed because desaturated blood enters arch vessels.
- In Eisenmenger PDA, desaturated blood from PA enters descending aorta → cyanosed legs.
- Coarctation of aorta with PDA can mimic differential cyanosis.
- Aortic dissection involving arch vessels may also produce differential cyanosis.
- Differential cyanosis is a key sign in neonates with duct-dependent congenital heart disease.
- Uniform cyanosis (all limbs) suggests central causes (e.g., TOF, pulmonary atresia).
- No cyanosis but differential saturation drop can occur in shock or PPHN.
- Always compare right hand (pre-ductal) vs foot (post-ductal) saturations for screening.
10 Short Q&A on Differential Cyanosis
Q1: What is differential cyanosis?
A: A condition where upper and lower limbs show different degrees of cyanosis.
A: A condition where upper and lower limbs show different degrees of cyanosis.
Q2: What is classic differential cyanosis?
A: Upper limbs are pink, lower limbs are cyanosed.
A: Upper limbs are pink, lower limbs are cyanosed.
Q3: What is the main cause of classic differential cyanosis?
A: PDA with Eisenmenger physiology.
A: PDA with Eisenmenger physiology.
Q4: What is reverse differential cyanosis?
A: Upper limbs cyanosed, lower limbs pink.
A: Upper limbs cyanosed, lower limbs pink.
Q5: What condition causes reverse differential cyanosis?
A: TGA with PDA and severe pulmonary hypertension.
A: TGA with PDA and severe pulmonary hypertension.
Q6: Which limb is used for pre-ductal saturation?
A: Right upper limb (right hand).
A: Right upper limb (right hand).
Q7: Which limb is used for post-ductal saturation?
A: Lower limbs (usually foot).
A: Lower limbs (usually foot).
Q8: Which congenital heart disease often shows uniform cyanosis instead?
A: Tetralogy of Fallot or pulmonary atresia.
A: Tetralogy of Fallot or pulmonary atresia.
Q9: What simple bedside test detects differential cyanosis?
A: Pulse oximetry comparing right hand and foot saturations.
A: Pulse oximetry comparing right hand and foot saturations.
Q10: Name two non-congenital causes of differential cyanosis.
A: Coarctation of aorta with PDA, aortic dissection involving arch vessels.
A: Coarctation of aorta with PDA, aortic dissection involving arch vessels.
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