Cyanosis

• Christopher D. Jackson, M.D.
• Robert W. Bradsher III, M.D.

 Basic Information

Definition

Discoloration of the skin with a blue or purple hue due to increased circulating levels of deoxygenated blood

Synonyms

1. Methemoglobinemia

2. Sulfhemoglobinemia

3. Acrocyanosis

4. Pseudocyanosis

ICD-10CM CODES
R23.0	Cyanosis
P28.2	Cyanotic attacks of the newborn
I73.8	Acrocyanosis

Epidemiology & Demographics

Incidence

Unknown

Peak Incidence

Unknown

Prevalence

Unknown

Predominant Sex and Age

Unknown

Genetics

None

Risk Factors

Congenital heart disease, high altitude, hypercoagulable state, cardiopulmonary disease, cirrhosis, exposure to aniline dyes, lidocaine use

Physical Findings & Clinical Presentation

1. •

   History: onset, time of day of symptoms, prior episodes of cyanosis, recent medication use, past medical history (PMHx) of congenital heart disease or cardiopulmonary disease, family history of congenital heart disease

2. •

   Physical examination: bluish discoloration of perioral skin, conjunctivae, and oral mucosa suggests central cyanosis; peripheral cyanosis will result in discoloration of extremities and nail beds

Etiology

Various causes are responsible for this clinical finding (see “Differential Diagnosis”). Investigation for the underlying cause is critical to determining appropriate treatment.

Diagnosis

Differential Diagnosis

1. •

   Cyanosis should be separated into central or peripheral causes to guide the differential diagnosis.

2. •

   Central cyanosis

   1. •

      Decreased arterial O₂ saturation—high altitude, hypoventilation, V/Q mismatch

   2. •

      Anatomic shunts—fistulae (cerebral, pulmonary, hepatic, peripheral), cyanotic congenital heart disease

3. •

   Peripheral cyanosis

   1. •

      Low cardiac output states (cardiogenic shock, hypovolemia with or without bleeding, sepsis)

   2. •

      Environmental exposures: air, water

   3. •

      Arterial occlusion: thrombosis, embolism, vasospasm (Raynaud’s), peripheral vascular disease

   4. •

      Venous obstruction

   5. •

      Redistribution of blood flow from extremities

   6. •

      Cyanide-related nitroprusside toxicity (initially, skin may be “cherry red” due to increased venous hemoglobin levels, progressing to cyanosis that accompanies shock)

Workup

1. •

   Fig. 1 outlines the approach to a patient with central cyanosis. The evaluation of peripheral cyanosis is summarized in Fig. 2.

   

   

2. •

   Examine patient’s circulation/airway/breathing (CAB), arterial blood gas (ABG), administer supplemental O₂; if concern for shock or patient otherwise unstable, obtain emergency medical services immediately.

3. •

   If improvement with O₂, obtain chest x-ray to evaluate cardiac silhouette

   1. •

      Normal cardiac silhouette suggests decreased pulmonary function from infiltrates, effusion, edema, pulmonary embolism (PE), or arteriovenous fistulae.

   2. •

      Enlarged cardiac silhouette may suggest cardiogenic shock; obtain electrocardiogram or echocardiogram to further evaluate.

   3. •

      If no improvement with supplemental O₂ (PaO₂ <100 or SaO₂ <70), obtain chest x-ray and methemoglobin, carbon monoxide, and cyanide levels.

   4. •

      If respiratory distress, evaluate for pneumothorax, upper airway obstruction, or bronchospasm.

   5. •

      If no respiratory distress, evaluate for chronic methemoglobinemia, sulfhemoglobinemia, G6PD deficiency, or cyanotic heart disease.

Laboratory Tests

1. •

   Deoxygenated hemoglobin in the capillary blood is elevated to ≥5 g/dL

2. •

   Complete blood count to evaluate for erythrocytosis, polycythemia, or anemia

3. •

   D-dimer if pulmonary embolism is suspected

4. •

   Peripheral smear to look for red blood cell count morphology and fragments

5. •

   Thiocyanate levels if possibility of nitroprusside toxicity

Imaging Studies

1. •

   Chest x-ray to evaluate for new pulmonary infiltrates, effusions, edema, or consolidations

2. •

   Compression ultrasonography of lower extremity or chest computed tomography angiography if deep venous thrombosis or PE suspected as cause for cyanosis

Treatment

Nonpharmacologic Therapy

Decontamination with soap and water after discontinuing offending agent

Acute General Rx

1. •

   Administer high-flow oxygen first and monitor response in all patients

2. •

   Methylene blue (1-2 mg/kg IV over 5 minutes) if patients have symptomatic hypoxia or methemoglobin level >30% in methemoglobinemia

3. •

   Phlebotomy and crystalloid fluid expansion to achieve hematocrit <45% if polycythemia

4. •

   Elevate head of bed and oxygen for superior vena cava syndrome; radiation/chemotherapy/vascular stenting if caused by malignancy

5. •

   Intravenous fluid resuscitation if hypovolemia is present

6. •

   Provide guideline-directed medical therapy for congestive heart failure, arrhythmias, or poor cardiac output

7. •

   Supportive care and antidotes if toxin-mediated cyanosis is present

Disposition

1. •

   Admit patients with first episode or unexplained cyanosis

2. •

   Discharge patients with peripheral cyanosis from vasoconstriction, methemoglobin <15%, and primary pulmonary disease

Referral

1. •

   Pediatric cardiology if children have first episode of congestive heart failure or newly diagnosed congenital heart disease

2. •

   Congenital vascular surgery evaluation if acute arterial occlusion is suspected or confirmed

3. •

   Suspected intensive care unit and/or cardiology assessment if cyanosis is due to acute cardiovascular or pulmonary collapse from shock

4. •

   Consider rheumatology for Raynaud’s phenomenon to assess for systemic autoimmune disorder

Pearls & Considerations

1. •

   In all patients with cyanosis, evaluate CAB, O₂ saturation, and ABG; provide supplemental O₂ to all patients with cyanosis.

2. •

   An increase in PaO₂ >100 or resolving cyanosis suggests oxygen diffusion defect.

3. •

   All patients with new-onset or unexplained cyanosis require hospitalization.

4. •

   Methylene blue in patients with methemoglobinemia if levels >30% or symptomatic hypoxia.

5. •

   Failure of methemoglobinemia to improve with methylene blue indicates sulfhemoglobinemia.

Prevention

1. •

   Avoid offending agents.

2. •

   Avoid excessive exposure to cold air or water.

Patient/Family Education

1. •

   Avoid excessive exposure to cold air or water if diagnosed with Raynaud’s phenomenon.

2. •

   Return to emergency department if cyanosis is accompanied by dyspnea, altered mentation, or chest pain.