| Cyanosis | |
|---|---|
 | |
| Cyanosis of the hand in an elderly person withlow oxygen saturation | |
| Specialty | Pulmonology,cardiology |
| Symptoms | Hypothermia, numbness in the area where the cyanosis is, coughing, wheezing, difficulty breathing |
| Types | Circumoral, central, peripheral |
| Causes | Airway problems, lung problems, heart problems, exposure to extreme cold |
| Differential diagnosis | Circumoral cyanosis,peripheral cyanosis,central cyanosis |
| Prevention | Avoid exposure to freezing cold temperatures, limit smoking orcaffeine, avoid touchingcyanide |
| Medication | Antidepressants, anti-hypertension medication, or if caused by other reasons,naloxone hydrochloride |
Cyanosis is the change oftissue color to a bluish-purple hue, as a result of decrease in the amount of oxygen bound to thehemoglobin in thered blood cells of thecapillary bed.[1] Cyanosis is apparent usually in thebody tissues covered with thinskin, including themucous membranes, lips,nail beds, and ear lobes.[1] Some medications may cause discoloration such as medications containingamiodarone orsilver. Furthermore,mongolian spots, large birthmarks, and the consumption of food products with blue or purple dyes can also result in the bluish skin tissue discoloration and may be mistaken for cyanosis.[2][3] Appropriatephysical examination and history taking is a crucial part to diagnose cyanosis. Management of cyanosis involves treating the main cause, as cyanosis is not a disease, but rather asymptom.[1]
Cyanosis is further classified intocentral cyanosis andperipheral cyanosis.
The mechanism behind cyanosis is different depending on whether it is central or peripheral.
Central cyanosis occurs due to decrease inarterial oxygen saturation (SaO2), and begins to show once the concentration ofdeoxyhemoglobin in the blood reaches a concentration of ≥ 5.0 g/dL (≥ 3.1 mmol/L or oxygen saturation of ≤ 85%).[4] This indicates a cardiopulmonary condition.[1]
Causes of central cyanosis are discussedbelow.
Peripheral cyanosis happens when there is increased concentration ofdeoxyhemoglobin on thevenous side of the peripheral circulation. In other words, cyanosis is dependent on the concentration of deoxyhemoglobin. Patients with severeanemia may appear normal despite higher-than-normal concentrations of deoxyhemoglobin. While patients with increased amounts of red blood cells (e.g.,polycythemia vera) can appear cyanotic even with lower concentrations of deoxyhemoglobin.[5][6]
Central cyanosis is often due to a circulatory orventilatory problem that leads to poor bloodoxygenation in thelungs. It develops when arterial oxygen saturation drops below 85% or 75%.[5]
Acute cyanosis can be a result ofasphyxiation orchoking and is one of the definitesigns that ventilation is being blocked.
Central cyanosis may be due to the following causes:
Peripheral cyanosis is the blue tint in fingers or extremities, due to an inadequate or obstructed circulation.[5] 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 ablue color. All factors contributing to central cyanosis can also cause peripheral symptoms to appear, but peripheral cyanosis can be observed in the absence of heart or lung failures.[5] Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.[5]
Peripheral cyanosis may be due to the following causes:[5]
Differential cyanosis is the bluish coloration of the lower but not theupper extremity and the head.[5] This is seen in patients with apatent ductus arteriosus.[5] Patients with a large ductus develop progressivepulmonary vascular disease, andpressure overload of theright ventricle occurs.[8] As soon as pulmonary pressure exceedsaortic pressure, shunt reversal (right-to-left shunt) occurs.[8] The upper extremity remains pink becausedeoxygenated blood flows through the patent duct and directly into thedescending aorta while sparing thebrachiocephalic trunk,left common carotid, andleft subclavian arteries.
A detailed history andphysical examination (particularly focusing on thecardiopulmonary system) can guide further management and help determine the medical tests to be performed.[1] Tests that can be performed includepulse oximetry,arterial blood gas,complete blood count,methemoglobin level,electrocardiogram,echocardiogram,X-Ray,CT scan,cardiac catheterization, andhemoglobin electrophoresis.
Innewborns, peripheral cyanosis typically presents in thedistal extremities, circumoral, and periorbital areas.[9] Of note,mucous membranes remain pink in peripheral cyanosis as compared to central cyanosis where the mucous membranes are cyanotic.[9]
Skin pigmentation andhemoglobin concentration can affect the evaluation of cyanosis. Cyanosis may be more difficult to detect on people with darker skin pigmentation. However, cyanosis can still be diagnosed with careful examination of the typical body areas such as nail beds, tongue, and mucous membranes where the skin is thinner and morevascular.[1] As mentionedabove, patients with severeanemia may appear normal despite higher than normal concentrations of deoxyhemoglobin.[5][6] Signs of severeanemia may include palemucosa (lips, eyelids, and gums),fatigue,lightheadedness, andirregular heartbeats.
Cyanosis is asymptom, not adisease itself, so management should be focused on treating the underlying cause.
If it is an emergency, management should always begin with securing theairway, breathing, and circulation. In patients with significantrespiratory distress,supplemental oxygen (in the form ofnasal canula orcontinuous positive airway pressure depending on severity) should be given immediately.[10][11]
If themethemoglobin levels are positive formethemoglobinemia, first-line treatment is to administermethylene blue.[1]
The namecyanosis literally meansthe blue disease orthe blue condition. It is derived from the colorcyan, which comes fromcyanós (κυανός), the Greek word forblue.[12]
It is postulated by Dr. Christen Lundsgaard that cyanosis was first described in 1749 byJean-Baptiste de Sénac, a French physician who served KingLouis XV.[13] De Sénac concluded from anautopsy that cyanosis was caused by a heart defect that led to the mixture ofarterial andvenous blood circulation. But it was not until 1919, when Dr. Lundsgaard was able to derive the concentration of deoxyhemoglobin (8 volumes per cent) that could cause cyanosis.[13]
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