Central and Peripheral Cyanosis

Excerpt

Cyan means blue, and the abnormal bluish skin and mucous membrane discoloration is called “cyanosis.” It is a pathologic sign and not a disease by itself. Underlying diseases that increase the deoxygenated hemoglobin to 5.0 g/dl or more leads to cyanosis. Cyanosis can be best appreciated in areas with rich superficial vasculature and thin overlying dermis. These include lips, nose, earlobes, oral cavity, extremities, and tips of fingers and toes. Cyanosis usually becomes evident in hypoxemia, that is, abnormally low oxygenation concentration (<80-85%) in arterial blood. However, it is not sensitive or a specific indicator of hypoxemia. Since cyanosis is a clinical sign, a proper evaluation is important to determine the etiology of cyanosis.

Cyanosis is further classified as central, peripheral, and differential.

1. Central cyanosis is a generalized bluish discoloration of the body and visible mucous membranes. It occurs due to inadequate oxygenation secondary to conditions that increase deoxygenated hemoglobin or abnormal hemoglobin.

2. Peripheral cyanosis is the bluish discoloration of the distal extremities (hands, fingertips, toes). It can sometimes involve circumoral and periorbital areas, but mucous membranes are generally not involved. Peripheral cyanosis is rarely a life-threatening medical emergency. However, it is essential to determine the underlying cause and manage it promptly to prevent potential complications.

3. Differential cyanosis is the asymmetrical bluish discoloration between the upper and lower extremities. It usually indicates serious underlying cardiopulmonary conditions.

Despite adequate oxygenation, bluish discoloration is sometimes seen after ingesting drugs, toxins, or metals. This is called pseudocyanosis.