Cyanosis

Overview
Cyanosis is a bluish coloration of the skin due to the presence of deoxygenated hemoglobin in blood vessels near the skin surface. It occurs when the oxygen saturation of arterial blood falls below 85%.

The elementary principle behind cyanosis is that deoxygenated hemoglobin produces the bluish discoloration, and also produces vasoconstriction that makes it more evident. Thus oxygen deficiency - hypoxia - leads to blue discoloration of the lips and other mucus membranes.

Historical Perspective
The name is derived from the color cyan, the greek word for blue.

Classification
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 poorer blood oxygenation in the lungs or greater oxygen extraction due to slowing down of blood circulation in the skin's blood vessels.

Differential Diagnosis of Central Cyanosis

 * Abnormal hemoglobin
 * Acute respiratory distress syndrome
 * Alveolitis
 * Atelectasis
 * Atrial septal defect
 * Bronchiectasis
 * Central or peripheral respiratory paralysis
 * Chronic bronchitis
 * Congenital heart disease
 * Decreased respiration with oversedation
 * Double outlet right ventricle
 * Emphysema
 * Foreign-body aspiration
 * High altitude exposure
 * Hypersensitivity pneumonitis
 * Intoxication
 * Intrapulmonary arteriovenous aneurysms
 * Lung cancer
 * Mediastinitis
 * Patent ductus arteriosus
 * Pickwickian syndrome
 * Pleural Effusions
 * Pneumoconiosis
 * Poliomyelitis
 * Polyneuropathy
 * Primary alveolar hypoventilation
 * Pulmonary arteriovenous fistulas
 * Pulmonary edema
 * Pulmonary embolism
 * Pulmonary fibrosis
 * Pulmonary hypertension
 * Severe chronic obstructive pulmonary disease (COPD) or asthma
 * Severe pneumonia
 * Single ventricle
 * Sleep apnea
 * Tension pneumothorax
 * Tetralogy of Fallot
 * Toxins/poisons
 * Transposition of the great vessels
 * Tuberculosis
 * Ventricular septal defect

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.

Differential Diagnosis of Peripheral Cyanosis

 * Acrocyanosis
 * Arterial embolism
 * Arrhythmia
 * Cardiomyopathy
 * Cold exposure
 * Congenital Heart Disease
 * Congestive Heart Failure
 * Endomyocardial fibrosis
 * Heart tumors
 * Hypertensive heart disease
 * Mitral Stenosis
 * Pericardial effusion
 * Polycythemia vera
 * Raynaud's Phenomenon
 * Shock
 * Superior vena cava obstruction
 * Valvular disease
 * Venous hypertension
 * Venous stasis

Differential Cyanosis
In adults with a large PDA, Eisenmenger's syndrome may develop with presents as cyanosis due to a right-to-left shunt. The inversion of the shunt is produced because of the progressive increase in pulmonary vascular resistance. Severe pulmonary vascular resistance results in reversal of flow through the ductus, and unoxygenated blood is shunted to the descending aorta, and the toes, but not the fingers, become cyanotic and clubbed, a finding termed differential cyanosis.

Heart
Check for murmurs of congenital or acquired valvular heart disease

Lungs
Careful auscultation for lung pathology

Extremities

 * Pulses in all extremities need to be evaluated.
 * Check capillary refill.
 * Clubbing of the toes or fingers may be indicative of chronic pulmonary disease or congenital heart disease.

Laboratory Findings

 * Complete blood count (CBC)
 * Glucose
 * Arterial blood gas
 * Blood urea nitrogen (BUN)/creatinine
 * Pulse oximetry

Electrocardiogram

 * ECG is indicated for diagnostic purposes

Chest X Ray

 * X-ray of chest can determine the size of the heart and lung pathology

MRI and CT

 * Possible CT scan can determine the size of the heart and lung pathology

Echocardiography or Ultrasound

 * To rule out structural abnormalities and to assess ventricular function and valves, an echocardiogram are recommended

Other Imaging Findings

 * Angiogram and pulmonary angiogram

Other Diagnostic Studies

 * Pulmonary function tests
 * Arterial doppler studies
 * Cardiac enzymes
 * Hemoglobin electrophoresis
 * Ventilation and Quantitative (V/Q) scan

Treatment

 * Supplemental oxygen is needed for all patients
 * Mechanical ventilation and intubation for respiratory support may be indicated
 * Underlying etiologies, and patients in shock need to be treated as clinically indicated

Acute Pharmacotherapies

 * Patients in congestive heart failure may need a diuretic or afterload reduction