Cyanosis pathophysiology

Cyanosis Microchapters
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Chandrakala Yannam, MD [2]

Overview

The exact pathogenesis of [disease name] is not fully understood.

OR

It is thought that [disease name] is the result of / is mediated by / is produced by / is caused by either [hypothesis 1], [hypothesis 2], or [hypothesis 3].

OR

[Pathogen name] is usually transmitted via the [transmission route] route to the human host.

OR

Following transmission/ingestion, the [pathogen] uses the [entry site] to invade the [cell name] cell.

OR

[Disease or malignancy name] arises from [cell name]s, which are [cell type] cells that are normally involved in [function of cells].

OR

The progression to [disease name] usually involves the [molecular pathway].

OR

The pathophysiology of [disease/malignancy] depends on the histological subtype.

Pathophysiology

• Cyanosis is a bluish or purplish discoloration of the skin and mucous membranes.
• Appearance of cyanosis depends on the absolute amount of deoxygenated hemoglobin(Hb) present in the blood rather than the ratio of reduced to oxygenated hemoglobin.
• According to Lundsgaard and Van Slyke (1923), as well as subsequent investigators, cyanosis is evident when the subpapillary capillaries contain from 4 to 6 gm/dl of deoxygenated hemoglobin and oxygenation of hemoglobin or oxygen saturation falls below 85%.
• Cyanosis occurs due to following mechanisms:
  • Systemic arterial oxygen desaturation.
    • Reduced arterial oxygenation can result if the amount of oxygen in the alveoli is lowered or if the gradient between the alveolar oxygen and the arterial oxygen is elevated.
  • Increased oxygen extraction by the tissues
• Central cyanosis:
  • Central cyanosis is caused by reduced arterial oxygen saturation or the presence of abnormal hemoglobin derivatives (methemoglobin or sulfhemoglobin).
  • Central cyanosis is evident when the systemic arterial deoxygenated hemoglobin concentration in the blood exceeds 5 g/dL (oxygen saturation ≤85 percent).
  • The increased amount of deoxygenated hemoglobin is the result of either increased amount of venous admixture or reduced capillary arterial oxygen tension.
• Peripheral cyanosis:
  • In peripheral cyanosis, systemic arterial oxygen saturation is normal.
  • Increased oxygen extraction by tissues causes wide systemic arteriovenous oxygen difference and increased deoxygenated blood on the venous side of the capillary beds.
  • The increased oxygen extraction by tissues results from the sluggish movement of blood through the capillary circulation.
  • Causes for reduced blood flow through capillary circulation include:
    • Vasoconstriction caused by exposure to cold
    • Venous obstruction
    • Elevated venous pressure
    • Hyperviscosity (Polycythemia)
    • Low cardiac output
    • Vasomotor instability

Genetics, Associated Conditions, Gross Pathology, Microscopic Pathology

For the details of the genetics, associated conditions, gross and microscopic pathology of the following causes of cyanosis, click the links below.

• Tetralogy of Fallot
• Tricuspid atresia
• Ebstein's anomaly
• Tricuspid stenosis
• Transposition of great arteries (TGA)
• Pulmonary stenosis
• Truncus arteriosus
• TAPVC
• Coarctation of aorta
• Aortic stenosis
• Eisenmenger's syndrome
• HLHS (Spectrum of hypoplastic left heart syndrome)
• Left-sided heart failure
• Acute chest syndrome
• Pneumothorax
• Foreign body aspiration
• Carbon monoxide poisoning
• Hydrogen cyanide poisoning
• Croup
• Bacterial tracheitis
• Hemothorax
• Pneumonia
• Asthma
• COPD
• Bronchiolitis
• Respiratory distress syndrome (Hyaline membrane disease)
• Empyema
• Pleural effusion
• Cystic fibrosis
• Atelectasis
• Bronchopulmonary dysplasia
• Alveolar capillary dysplasia
• Pulmonary embolism
• Pulmonary hypertension
• High Altitude
• Intracranial hemorrhage
• Seizures
• Choanal atresia
• Micrognathia or retrognathia
• Laryngomalacia
• Congenital diaphragmatic hernia
• Myasthenia gravis
• Apnea of prematurity
• Obstructive sleep apnea
• Pulmonary edema
• Pulmonary hemorrhage
• Pulmonary arteriovenous malformation
• Methemoglobinemia (congenital or acquired)
• Sulfhemoglobinemia
• Polycythemia vera
• Disseminated intravascular coagulation
• Shock
• Sepsis
• Amniotic fluid embolism
• Cold exposure
• Acrocyanosis
• Raynaud's phenomenon
• Raynaud's disease
• Peripheral vascular disease
• Buergers disease
• Deep vein thrombosis
• Superior vena cava syndrome