Introduction

Cyanosis refers to a condition marked by bluish discolouration appearing on the skin or mucous membranes.¹ The term "cyanosis" originates from the word "cyan," which refers to a blue-green colour.¹ Cyanosis is not a sickness; rather, it is a pathologic indication.²

The diagnosis of cyanosis could be challenging since there are several underlying conditions that can cause it.¹ A comprehensive physical examination, ancillary investigations, and meticulous history are the mainstays in the diagnosis and treatment of cyanosis.¹

In this article, we will discuss the various diagnostic tools, methods, and diverse treatment modalities available to address cyanosis effectively.

Causes of cyanosis 

Cyanosis typically results when there is an issue with the way oxygen binds to haemoglobin in our blood.¹ This may occur if haemoglobin (which carries oxygen throughout your body) is not receiving enough oxygen, which might be caused by issues in the cardiovascular system, respiratory system, and central nervous system.¹ The main types of cyanosis are 

• Central cyanosis
• Peripheral cyanosis 
• Differential cyanosis²

• Central cyanosis occurs when there is a large amount of deoxygenated haemoglobin (haemoglobin without bounded oxygen) in the arteries, typically with oxygen levels below 85%.¹ This bluish colour can be observed all over the body and even on visible mucous membranes.¹ Typical reasons for central cyanosis are pneumonia-related impaired gas exchange in the lungs, the mismatch between ventilation-perfusion and embolism (blood flow blockage), reduced alveolar diffusion of gas, high altitude, and anatomic shunts.¹
• Peripheral cyanosis is often limited to the lower and upper limbs, where there is slower blood flow.¹ Here, the oxygen levels between the arterial (oxygen-rich blood) and venous blood (oxygen-poor blood) show a noticeable difference because the tissues in these regions pull out more oxygen from the blood vessels. It can be caused by several circumstances, including low cardiac output, venous stasis, and exposure to extremely cold temperatures resulting in vasoconstriction (narrowing of blood vessels).¹
• The uneven blue colouration of the lower and upper limbs is known as differential cyanosis. It typically denotes significant underlying cardiopulmonary conditions.²
• Abnormal haemoglobin could also result in cyanosis, as it significantly reduces the blood's ability to transport oxygen. Tissue hypoxia from this may result in cyanosis as a clinical symptom.¹
• Methemoglobinemia (iron in haemoglobin transforms from the ferrous (Fe²⁺) to the ferric (Fe³⁺) state) and sulfhaemoglobin (sulfur binding to haemoglobin) are other causes of cyanosis.¹

Clinical presentation and symptoms

The most obvious signs of cyanosis are found in areas where the skin is thin and has lots of tiny blood vessels near the surface, such as the lips, nose, earlobes, oral cavity, limbs, as well as fingers and toes tips.² Furthermore, patients may experience dizziness, trouble breathing, rapid and shallow breathing, and a bluish or purple discolouration of the oral mucous membranes. Recognising these symptoms can help facilitate rapid medical examination and treatment.³

Diagnostic evaluation

Medical history and physical examination

First, the physician will perform a comprehensive evaluation of the patient's medical history. The main emphasis of the investigations will be on when the blue discolouration first emerged and whether it got worse over time or suddenly.³ The doctor will also enquire as to whether the bluish colour is uniform throughout the body or whether it just affects particular regions, such as the tongue, lips, and nail beds.³

The medical history will entail enquiries regarding exposure to cold temperatures or abrupt altitude changes, exposure to substances, or recent medication use.³ The doctor will also investigate the existence, severity, and length of any additional symptoms, including breathing difficulties, foot or ankle swelling, coughing, and chest discomfort, as well as any other important symptoms.³ Examination also involves paying attention to the heart and breathing sounds, pulse rate and blood pressure.³ Additional clinical manifestations include clubbing of the fingers, development alt retardation in infants with cyanotic heart disease, fever (in the event of infections), etc.³

Diagnostic tests

Pulse oximetry

 It is a non-invasive and readily available test which is used to measure oxygenation and can be performed if cyanosis is thought to be caused by hypoxemia.² By placing a sensor on your finger, a pulse oximeter determines the level of oxygen in your blood.⁴ However, since the pulse oximeter detects light absorption at just two wavelengths, which are associated with oxyhaemoglobin and deoxyhaemoglobin, cyanosis secondary to methaemoglobinaemia could be misdiagnosed as pulse oximetry does not detect abnormal haemoglobin.¹

Co-oximetry

Co-oximetry is a valuable diagnostic technique for a patient who is suspected of having abnormal haemoglobin and presents with cyanosis.¹ Since co-oximetry analyses light absorption at four separate wavelengths that correspond to oxyhaemoglobin, deoxyhaemoglobin, carboxyheamoglobin, and methaemoglobin, it offers a more precise assessment of oxygen saturation.¹ Co-oximetry is a helpful diagnostic technique for a patient exhibiting cyanosis in whom aberrant haemoglobin is suspected.¹

Arterial blood gas analysis

The arterial blood gas analysis provides both the saturation of haemoglobin and the partial pressure of dissolved oxygen in the blood. The blood sample is collected from an artery and treated with heparin.⁵ If the sample appears dark red and turns bright red when exposed to air, it suggests arterial hypoxemia. However, if the sample is brown and remains unchanged when exposed to air, the plasma is separated. Brown plasma indicates the likely presence of methaemalbumin.⁵ Clear plasma suggests the presence of methaemoglobin or sulfhaemoglobin.⁵

Haemoglobin electrophoresis

Haemoglobin M is one of the abnormal haemoglobin variants that can cause congenital cyanosis.¹ The most reliable method to identify haemoglobin M is routine haemoglobin electrophoresis.¹

Imaging studies

Imaging tests such as X-rays, CT scans, and chest ultrasonography are the most effective ways to assess pulmonary causes of cyanosis, which include pneumonia, pleural effusion, and pulmonary embolism.¹ The kind of abnormality of the heart in congenital heart defects can be detected by using cardiac doppler with echo or ultrasound, which aids in determining the proper flow and volume of blood via the heart and the large vessels.³ CT scans of the chest or heart and MRI scans could also be employed.³

Echocardiography

An ultrasound of the heart that displays its structure and function is called an Echocardiogram. If a congenital heart condition is anticipated, transthoracic and transesophageal echocardiography is performed to assess the cardiovascular system.⁴

Additional tests as indicated by clinical presentation

• A full blood count is performed for the detection of characteristics such as low haemoglobin (anaemia), low red blood cell count (anaemia), high red blood cell count (polycythemia), etc., and increased white blood cell counts (a sign of infection).³
• To identify irregularities in the heart's rhythm and rate, an electrocardiogram, or ECG, is advised.³
• Nuclear imaging examinations and cardiac electrophysiologic studies are used for testing for heart abnormalities.³
• Sputum is examined for microorganisms in cases of lung infections and pneumonia. It may also be necessary to perform blood cultures for infection detection.³
• When a patient has a pulmonary embolism, a ventilation-perfusion scan is advised. A lung angiography aids in identifying the embolism and seeing the blood vessels in the lungs.³
• It is recommended to get a haemoglobin spectroscopy if methaemoglobin or sulfhaemoglobin is detected.³
• It may be necessary to do a digital subtraction angiography to detect arterial blockage. Similar to this, venography or a Duplex Doppler are recommended for cases of acute venous occlusion.³
• Cardiac catheterization provides details on the precise blood pumping mechanism of the heart. This entails inserting a catheter, which is a tiny, flexible tube, into an arm or groyne blood vessel. Up to the heart, the tube is threaded.³ A little blood pressure monitor at the end of the tube allows you to collect readings of your blood pressure in several locations of the heart.³

Treatment approaches

Central cyanosis is a sign of an underlying illness, and the aim is to address the underlying conditions that are producing central cyanosis.¹ Finding and treating the root cause of vasoconstriction and the reduced flow of oxygen-rich blood to the extremities is the aim of treating peripheral cyanosis.

Surgical interventions

Surgery is frequently used to treat central cyanosis brought on by congenital cardiac abnormalities.¹ Cardiology examination and intervention must be sent as soon as possible for newborns and neonates with cyanotic congenital cardiac diseases, such as tetralogy of Fallot, tricuspid atresia, and truncus arteriosus.¹

Oxygenation

The cyanosis due to hypoxia and pulmonary oxygen diffusion impairment can be resolved by giving oxygen assistance. To give sufficient breathing support, a standard nasal cannula, a high-flow nasal cannula and, in certain cases, assisted ventilation may be needed.^1,2

Medications

• Patients with heart failure may be offered medications such as diuretics, ACE inhibitors, and inotropics to lessen the excessive buildup of fluids.^2,6
• Patients with cyanotic heart disease and heart failure also require medications that increase the heart's pumping force. Prescription medications may also be used to treat irregular heart rhythms or beats.⁶
• Antibiotics are used for the treatment of pneumonia as well as to avoid infections.⁶
• For ductal-dependent disorders involving pulmonary blood flow, medications such as prostaglandin E1 infusion are used.^1,2
• Patients with cyanotic cardiac disease are prescribed antibiotic prophylaxis to avoid bacterial endocarditis.²
• Medication can be used to treat patients with patent ductus arteriosus after birth. Ibuprofen or Indomethacin may be provided to them. This aids in the duct's closing. Surgery may be used to seal the opening if medication is ineffective.⁶
• In cases of peripheral cyanosis, medications that relax blood vessels may be administered. These include erectile dysfunction medications, antidepressants, and antihypertensive medicine.²
• Furthermore, medicines that narrow blood vessels, such as beta-blockers, birth control pills, drugs containing pseudoephedrine, and migraine treatments, must be ignored.²

Other treatment approaches

• Warming the fingers and toes gently and massaging them can be used as a symptomatic treatment for peripheral cyanosis caused by exposure to cold or Raynaud's phenomenon.²
• Cyanosis brought on by metheamoglobinemia is treated with methylene blue.¹
• Eliminating the offending chemicals is the best treatment for blue discolouration brought on by exposure to gold and silver salts.¹
• It is possible to treat cyanosis caused by other factors, such as low blood sugar level,which can be treated  by administering and infusing glucose.⁶
• In order to avoid infections, children with congenital heart disease need to have timely vaccinations.⁶
•  Intravenous fluids are necessary for children with cyanosis who are unable to swallow and are experiencing heart failure due to an underlying cyanotic heart condition.⁶

Patient education

It is important to educate patients and their families about the risk factors and preventative steps that could be taken to stop the disease from getting worse. Listed below are a few suggestions: 

• Avoid using cigarettes
• Keeping blood pressure under control 
• Limit the use of nicotine and caffeine
• Management of cholesterol levels 
• Avoid  harsh temperatures 
• Prevent immobility²

FAQs

Is cyanosis an emergency?

Even though it is not usually dangerous, cyanosis can result from a severe medical condition.

If you witness an adult or kid suddenly turning blue, it is critical to get medical help as soon as possible, especially with symptoms like breathing difficulty.⁴ 

What happens if cyanosis is left untreated? 

If left untreated, the disease could worsen, causing additional complications, and serious cases of cyanosis can develop into events that could be life-threatening, such as cardiac arrest or respiratory failure.⁷

Summary

Cyanosis is characterised by a bluish discolouration of the skin or mucous membranes and can result from various underlying conditions affecting oxygenation. The diagnosis of cyanosis involves a thorough medical history, physical examination, and various diagnostic tests, including pulse oximetry, arterial blood gas analysis, and imaging studies. Treatment of cyanosis involves oxygen therapy, medications, and surgical procedures. In order to manage cyanosis, patient education is essential, which emphasises lifestyle changes to reduce risk factors. Moreover, early recognition and prompt intervention are also crucial for improving outcomes as well as preventing complications of cyanosis.