Cyanosis

Cyanosis 

Bluish coloration of tissue caused by increased quantity of deoxygenated hemoglobin

Synonyms

• Methemoglobinemia
• Sulfhemoglobinemia
• Acrocyanosis
• Pseudocyanosis

Epidemiology & Demographics

Incidence

Unknown

Prevalence

Unknown

Predominant Sex and Age

Unknown

Peak Incidence

Unknown

Risk Factors

Congenital heart disease, environmental exposures, hypercoagulable state, cardiopulmonary disease, cirrhosis, exposure to aniline dyes, lidocaine use

Genetics

None

Physical Findings & Clinical Presentation

• •History: Congenital heart disease; cardiopulmonary disease; infection; shock; peripheral vascular disease; environmental exposures; hemoglobinopathies and blood disorders; medications; street drug use; time of onset and course
• •Physical examination: Bluish discoloration may be present over skin of distal extremities, perioral and nasal tissue, and periauricular areas, as well as mucosal surfaces of mouth and eyes. Central causes often include both extremity and mucosal findings, whereas peripheral causes involve only extremity findings. Tachypnea, retractions, and abnormal lung findings on auscultation are often associated with respiratory causes of cyanosis. Tachycardia frequently accompanies cyanosis in children. Critically, bradycardia and bradypnea in the setting of cyanosis can indicate impending circulatory collapse. Clubbing of the fingers may be present in chronic cardiopulmonary and vascular causes.

What causes Cyanosis?

The etiology of cyanosis may be separated into central and peripheral causes. Central cyanosis is underpinned by a global reduction in hemoglobin oxygenation affecting the entire volume of circulation.

Due to this reduction in oxygenation, central causes of cyanosis manifest findings in both extremities and mucosal tissues.

Peripheral cyanosis is due to a decreased rate of blood flow through tissues resulting in greater oxygen extraction from normally oxygenated hemoglobin in the arterial blood volume.

Therefore, peripheral causes of cyanosis predominately affect the extremities as the vasculature’s hemostatic mechanisms shunt blood centrally during low-flow states.

Differential Diagnosis

Central cyanosis

• •Decreased arterial O₂ saturation
  • 1.Decreased atmospheric oxygenation—high altitude; enclosed environment with low oxygen partial pressure
  • 2.Impaired pulmonary function—hypoventilation, V/Q mismatch, impaired O2 diffusion
• •Anatomic shunts—fistulae (cerebral, pulmonary, hepatic, peripheral), cyanotic congenital heart disease
• •Hemoglobin with low O₂ affinity
• •Hemoglobin abnormalities—methemoglobinemia, sulfhemoglobinemia, carboxyhemoglobinemia (not true cyanosis)

Peripheral cyanosis

• •Low cardiac output states (cardiogenic shock, hypovolemia with or without bleeding, sepsis)
• •Environmental exposures: Air, water
• •Arterial occlusion: Thrombosis, embolism, vasospasm (Raynaud), peripheral vascular disease
• •Venous obstruction
• •Redistribution of blood flow from extremities
• •Cyanide-related nitroprusside toxicity (initially, skin may be “cherry red” due to increased venous hemoglobin levels, progressing to cyanosis that accompanies shock)

How is Cyanosis diagnosed?

• •Examine patient’s airway/breathing/circulation (ABC), full vital signs, and pulse oxygenation, arterial blood gas (ABG). Administer supplemental O₂ for SpO₂ <90%, as this indicates hypoxemia. If concern exists for shock or patient is otherwise unstable, obtain emergency medical services immediately for management of airway and breathing as needed, and for additional evaluation.
• •If improvement with supplemental 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, as well as 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

Please note that the following are not always necessary; order as clinically appropriate:

• •Arterial blood gas analysis to assess oxygenation
• •Deoxygenated hemoglobin in the capillary blood is elevated to ≥5 g/dl suggests cyanosis
• •Complete blood count to evaluate for erythrocytosis, polycythemia, or anemia
• •d-dimer to evaluate for pulmonary embolism if clinically indicated
• •Peripheral smear to evaluate blood cell count, morphology, and fragments
• •Thiocyanate levels if suspected nitroprusside toxicity
• •Methemoglobin level in cases of suspected methemoglobinemia

Imaging Studies

• •Chest x-ray to evaluate for new pulmonary infiltrates, effusions, edema, or consolidations
• •ECG for those with abnormal cardiac examination findings
• •Echocardiography for infants and children with suspected congenital heart disease
• •Compression ultrasonography of lower extremity or chest computed tomography angiography if deep venous thrombosis or PE suspected as cause for cyanosis

How is Cyanosis Treated?

Nonpharmacologic Therapy

Decontamination with soap and water after discontinuing offending agent

Acute General Treatment

• •Administer high-flow oxygen first and monitor response in all patients
• •Methylene blue (1-2 mg/kg IV over 5 min) if patients have symptomatic hypoxia or methemoglobin level >30%
• •Phlebotomy and crystalloid fluid expansion to achieve hematocrit <45% if polycythemia
• •Elevate head of bed and oxygen for superior vena cava syndrome; radiation/chemotherapy/vascular stenting if caused by malignancy
• •Intravenous fluid resuscitation if hypovolemia is present; early consideration for packed red blood cells, as crystalloid fluids do not intrinsically increase oxygen-carrying capacity of existing hemoglobin.
• •Cyanotic patients with altered mental status often have decreased oxygen saturation due to disordered breathing or neuromuscular weakness causing respiratory depression. Such patients typically cannot maintain their airway and will require advanced airway support unless their underlying cause ofcoma can be treated rapidly (dextrose for hypoglycemia, naloxone for opioid overdose, benzodiazepine for seizures).
• •Transient central cyanosis is a common feature of breath-holding spells and seizures and requires no specific therapy once patient is alert
• •Provide guideline-directed medical therapy for congestive heart failure, arrhythmias, or poor cardiac output
• •Supportive care and antidotes if toxin-mediated cyanosis is present

Disposition

• •Admit patients with first episode cyanosis, unexplained cause of symptoms, or are unstable.
• •Discharge stable patients with peripheral cyanosis from vasoconstriction, methemoglobin <15%, and primary pulmonary disease if improved clinically and able to maintain oxygen saturations without additional supplemental O₂.

Referral

• •Pediatric cardiology if children have first episode of congestive heart failure or newly diagnosed congenital heart disease as suggested by abnormal ECG and/or chest radiograph findings
• •Vascular surgery evaluation if acute arterial occlusion is suspected or confirmed
• •Suspected intensive care unit and/or cardiology assessment if cyanosis is due to acute cardiovascular or pulmonary collapse from shock
• •Consider rheumatology for Raynaud phenomenon to assess for systemic autoimmune disorder

Pearls

• •In all patients with cyanosis, evaluate ABCs, O₂ saturation, and ABG; provide supplemental O₂ to all patients with cyanosis.
• •An increase in PaO₂ >100 or resolving cyanosis suggests oxygen diffusion defect.
• •All patients with new-onset or unexplained cyanosis require hospitalization.
• •Administer methylene blue in patients with methemoglobinemia if levels >30% or symptomatic hypoxia.
• •Failure of methemoglobinemia to improve with methylene blue indicates sulfhemoglobinemia.
• •In infants with or suspicion for a ductal-dependent congenital heart defect, prostaglandin E1 (alprostadil) should be administered until a definitive diagnosis or treatment is established.

Prevention

• •Avoid offending agents.
• •Avoid excessive exposure to cold air or water.
• •Treat underlying medical comorbidities

Patient & Family Education

• •Avoid excessive exposure to cold air or water if diagnosed with Raynaud phenomenon.
• •Return to the emergency department if cyanosis is accompanied by dyspnea, altered mentation, or chest pain.

Seek Additional Information

• Fernández-Frackelton M.: Cyanosis. In Walls RM, et al. (eds): Rosen’s emergency medicine: concepts and clinical practice., ed 9 2018. Elsevier Health Sciences, Philadelphia pp. 108-114.
• Miller A., Nagler J.: Devices for assessing oxygenation and ventilation. In Roberts J, et al. (eds): Roberts and Hedges’ clinical procedures in emergency medicine and acute care., ed 7 2019. Elsevier Health Sciences, Philadelphia pp. 23-37.