3. Raynaud's phenomenon
Discussion:
Cyanosis is divided into two main types:
Central (around the core and lips)
Peripheral (only the extremities are affected).
Cyanosis can occur in the fingers, including underneath the fingernails, as well as other extremities (called peripheral cyanosis), or in the lips and tongue (central cyanosis).
Central cyanosis
Central cyanosis is often due to a circulatory or ventilatory problem that leads to poor blood oxygenation in the lungs. It develops when arterial saturation of blood with oxygen is ≤85%. Cyanosis may not be detected until saturation is 75% in dark-skinned individuals.
Acute cyanosis can be a result of asphyxiation or choking, and is one of the surest signs that respiration is being blocked.
Causes
1. Central Nervous System:- Intracranial hemorrhage
- Cerebral anoxia
- Drug overdose (e.g. Heroin)
- Bronchiolitis
- Bronchospasm (e.g. Asthma)
- Lung disease
- Pulmonary embolism
- Hypoventilation
- COPD (emphysema and chronic bronchitis)
- Congenital heart disease (e.g. Tetralogy of Fallot, Right to left shunts in heart or great vessels)
- Heart failure
- Heart valve disease
- Myocardial infarction
5.Others:
- High altitude
- Hypothermia
- Congenital cyanosis (HbM Boston) arises from a mutation in the α-codon which results in a change of primary sequence, H --> Y. Tyrosine stabilises the Fe(III) form (oxyhaemoglobin) creating a permanent T-state of Hb.
- Obstructive sleep apnea
Peripheral cyanosis
Peripheral cyanosis is the blue tint in fingers or extremities, due to inadequate circulation. The blood reaching the extremities is not oxygen rich and when viewed through the skin a combination of factors can lead to the appearance of a blue color. All factors contributing to central cyanosis can also cause peripheral symptoms to appear, however peripheral cyanosis can be observed without there being heart or lung failures. Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.
Causes
- All common causes of central cyanosis
- Arterial obstruction
- Cold exposure (due to vasoconstriction)
- Raynaud's phenomenon (vasoconstriction)
- Reduced cardiac output (e.g. heart failure, hypovolaemia)
- Vasoconstriction
- Venous obstruction (e.g. deep vein thrombosis)
Pearls:
On Physical Exam cyanosis is best (most reliably) observed by looking at the tongue
Pulse-Oximetry cannot differentiate Methemoglobinemia
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Interesting Story:
The Fugates, a family that lived in the hills of Kentucky, are the most famous example of this hereditary genetic condition. Known as the Blue Fugates, Martin Fugate, settled near Hazard, Kentucky, circa 1800. His wife was a carrier of the recessive methemoglobinemia (met-H) gene, as was a nearby clan with whom the Fugates intermarried. As a result, many descendants of the Fugates were born with met-H.[7][8]
The 'blue men of Lurgan' were a pair of Lurgan men suffering from what was described as 'familial idiopathic methaemoglobinaemia' who were treated by Dr. James Deeny in 1942. Deeny, who would later become the Chief Medical Officer of the Republic of Ireland, prescribed a course of ascorbic acid and sodium bicarbonate. In case one, by the eighth day of treatment there was a marked change in appearance and by the twelfth day of treatment the patient's complexion was normal. In case two, the patient's complexion reached normality over a month-long duration of treatment.[9]
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