Cyanosis
Cyanosis
Q1. Cyanosis becomes clinically apparent when deoxygenated hemoglobin exceeds:
Q2. Which type of cyanosis is seen on tongue and mucous membranes?
Q3. Cyanosis limited to fingers and toes is most consistent with:
Q4. In which condition is “differential cyanosis” seen?
Q5. Reverse differential cyanosis is typically seen in:
Q6. Which of the following is NOT a cause of central cyanosis?
Q7. Which type of cyanosis shows improvement with oxygen therapy?
Q8. Which of the following is a feature of peripheral cyanosis?
Q9. Cherry-red lips without cyanosis is seen in:
Q10. Clubbing is most often associated with:
Q11. Minimum Hb required for cyanosis to be visible:
Q12. Which of the following is a cardiac cause of central cyanosis?
Q13. Peripheral cyanosis is most likely in:
Q14. In methemoglobinemia, cyanosis occurs because:
Q15. Which of the following best differentiates central from peripheral cyanosis?
Q16. High altitude cyanosis is due to:
Q17. Which investigation is most useful in differentiating central vs peripheral cyanosis?
Q18. Peripheral cyanosis with warm extremities suggests:
Q19. Cyanosis does NOT occur in:
Q20. Long-standing cyanosis can lead to:
Cyanosis
| Point | Summary |
|---|---|
| 1 | Definition: Bluish discoloration of skin/mucous membranes due to >5 g/dL deoxygenated Hb. |
| 2 | Detection requires adequate hemoglobin; may not be visible if Hb <5 g/dL (severe anemia). |
| 3 | Types: Central, Peripheral, Differential, Reverse differential. |
| 4 | Central Cyanosis: Due to low arterial O₂ saturation. Seen on tongue, lips, mucosa. |
| 5 | Peripheral Cyanosis: Due to sluggish circulation/vasoconstriction. Seen on extremities. |
| 6 | Differential Cyanosis: Lower limb cyanosis with spared upper limbs (PDA with Eisenmenger physiology). |
| 7 | Reverse Differential Cyanosis: Upper limb cyanosis with spared lower limbs (TGA with PDA + PHT). |
| 8 | Central causes (Respiratory): COPD, ARDS, pneumonia, pulmonary embolism. |
| 9 | Central causes (Cardiac): R→L shunts (TOF, Eisenmenger), severe CHF. |
| 10 | Peripheral causes: Shock, heart failure, cold exposure, peripheral vascular disease. |
| 11 | Blood disorders: Methemoglobinemia, sulfhemoglobinemia cause cyanosis despite normal PaO₂. |
| 12 | Pulse oximetry: Shows ↓ saturation in central cyanosis, may be misleading in methemoglobinemia. |
| 13 | ABG: Low PaO₂ in central cyanosis; normal PaO₂ in peripheral cyanosis. |
| 14 | Clubbing often accompanies chronic central cyanosis (e.g., cyanotic CHD, chronic lung disease). |
| 15 | Polycythemia may develop as compensatory response in chronic hypoxemia. |
| 16 | Effect of oxygen: Central cyanosis improves with O₂ (unless shunt); peripheral cyanosis shows little change. |
| 17 | Temperature of extremities: Cold in peripheral cyanosis; warm in central cyanosis. |
| 18 | Special sign: Cherry-red lips in CO poisoning (not cyanosis despite hypoxia). |
| 19 | High altitude: Can cause central cyanosis due to low inspired O₂ tension. |
| 20 | Clinical importance: Always signifies hypoxemia, circulatory stasis, or abnormal Hb — requires urgent evaluation. |
Cyanosis Short Q&A
Q1. What is the definition of cyanosis?
➡️ Bluish discoloration of skin/mucosa due to >5 g/dL deoxygenated hemoglobin.
Q2. When does cyanosis become clinically apparent?
➡️ When deoxygenated hemoglobin exceeds 5 g/dL.
Q3. Why may cyanosis be absent in severe anemia?
➡️ Total hemoglobin is low, so deoxy-Hb rarely exceeds 5 g/dL.
Q4. What are the main types of cyanosis?
➡️ Central, Peripheral, Differential, and Reverse Differential.
Q5. Which type involves tongue and mucous membranes?
➡️ Central cyanosis.
Q6. Which type is limited to fingers, toes, and extremities?
➡️ Peripheral cyanosis.
Q7. What are the main cardiac causes of central cyanosis?
➡️ Right-to-left shunts (e.g., TOF, Eisenmenger).
Q8. Name two respiratory causes of central cyanosis.
➡️ COPD, severe pneumonia, ARDS, pulmonary embolism.
Q9. What causes differential cyanosis?
➡️ PDA with Eisenmenger physiology (cyanosis in lower limbs, upper spared).
Q10. What causes reverse differential cyanosis?
➡️ TGA with PDA and pulmonary hypertension (upper cyanotic, lower spared).
Q11. How do extremities feel in peripheral cyanosis?
➡️ Cold due to vasoconstriction and sluggish blood flow.
Q12. How do extremities feel in central cyanosis?
➡️ Warm, as arterial O₂ is low but circulation intact.
Q13. Which type of cyanosis improves with oxygen therapy?
➡️ Central cyanosis (except intracardiac shunts).
Q14. Why does peripheral cyanosis not improve with oxygen therapy?
➡️ Because the problem is circulatory stasis, not low PaO₂.
Q15. What investigation differentiates central from peripheral cyanosis?
➡️ Arterial blood gas (ABG).
Q16. What does ABG show in central cyanosis?
➡️ Low PaO₂.
Q17. What does ABG show in peripheral cyanosis?
➡️ Normal PaO₂, but increased O₂ extraction in tissues.
Q18. What abnormal hemoglobin states can cause cyanosis?
➡️ Methemoglobinemia, sulfhemoglobinemia.
Q19. What feature is often associated with chronic central cyanosis?
➡️ Clubbing of fingers and toes.
Q20. What hematological adaptation occurs in long-standing cyanosis?
➡️ Polycythemia (secondary erythrocytosis).
| Point | Central Cyanosis | Peripheral Cyanosis | Differential Cyanosis | Reverse Differential Cyanosis |
|---|---|---|---|---|
| 1. Definition | Low arterial O₂ saturation | Increased extraction due to slow flow | Lower limb cyanosis, upper spared | Upper limb cyanosis, lower spared |
| 2. Site | Lips, tongue, mucosa, skin | Fingers, toes, nail beds | Lower extremities | Upper extremities |
| 3. Extremity temperature | Warm | Cold | Lower limbs cyanotic & warm | Upper limbs cyanotic, lower warm |
| 4. Oxygen therapy response | Improves (unless R→L shunt) | Little/no improvement | Partial response | Limited response |
| 5. PaO₂ | Decreased | Normal | Lower body PaO₂ ↓ | Upper body PaO₂ ↓ |
| 6. Cause (cardiac) | R→L shunts (TOF, Eisenmenger) | CHF, shock | PDA with Eisenmenger | TGA with PDA + PHT |
| 7. Cause (respiratory) | COPD, ARDS, pneumonia | Hypoperfusion | — | — |
| 8. Cause (hematologic) | Methemoglobinemia, sulfHb | — | — | — |
| 9. Mucous membrane involvement | Present | Absent | Lower lips spared | Upper lips affected |
| 10. Visibility in anemia | Less visible if Hb low | Less visible if Hb low | Same rule applies | Same rule applies |
| 11. Associated signs | Clubbing, polycythemia | Cold, clammy extremities | Lower limb cyanosis only | Upper limb cyanosis only |
| 12. ABG finding | Low PaO₂ | Normal PaO₂ | Low PaO₂ in legs | Low PaO₂ in arms |
| 13. Pulse oximetry | ↓ saturation | Usually normal | ↓ saturation in legs | ↓ saturation in arms |
| 14. Example systemic cause | High altitude hypoxemia | Severe circulatory shock | PDA + Eisenmenger | TGA + PDA + PHT |
| 15. Duration | Often chronic (CHD, COPD) | Often acute (shock, cold) | Chronic with PDA shunt reversal | Chronic with TGA physiology |
| 16. Color intensity | Generalized, dark blue | Localized, patchy blue | Lower body bluish | Upper body bluish |
| 17. Clubbing | Common in long-standing cases | Absent | May occur in lower limbs only | May occur in upper limbs only |
| 18. Polycythemia | Common | Absent | May occur | May occur |
| 19. Key differentiator | Tongue & mucosa involved | Extremities only | Lower limb cyanosis only | Upper limb cyanosis only |
| 20. Clinical importance | Indicates hypoxemia | Indicates circulatory stasis | Indicates PDA reversal | Indicates TGA with PHT |
Cyanosis,,Central cyanosis,,Peripheral cyanosis,,Differential cyanosis,,Reverse differential cyanosis,,Cyanosis causes,,Cyanosis types,,Cyanosis flowchart,,Cyanosis infographic,, ,Low arterial oxygen saturation,,PaO₂ decrease,,Hypoxemia,,Hypoxia,,Reduced oxygen delivery,,Oxygen therapy response,,Right-to-left shunt,,Pulmonary disease cyanosis,,Congenital heart disease cyanosis,, ,Right-to-left shunt cyanosis,,Patent ductus arteriosus (PDA),,Eisenmenger syndrome,,Transposition of great arteries (TGA),,Cyanotic congenital heart disease,,Cardiac cyanosis,,Cyanosis in newborn,,Differential diagnosis cyanosis,, ,Cyanosis in COPD,,Cyanosis in interstitial lung disease,,Cyanosis in pneumonia,,Methemoglobinemia,,Hemoglobinopathies,,Cold extremities cyanosis,,Shock and cyanosis
