The type of cyanosis seen in PDA is?

HPSSC Staff Nurse - 2021

Child Health Nursing (Pediatrics)

Hard

Appeared in: HPSSC Staff Nurse - 2021

Explanation

Differential cyanosis is the hallmark sign of a Patent Ductus Arteriosus (PDA) with a reversed (right-to-left) shunt.
This condition occurs when severe pulmonary hypertension (Eisenmenger syndrome) develops, causing deoxygenated blood from the pulmonary artery to flow into the descending aorta.
Because the PDA connects to the aorta after the arteries supplying the upper body, deoxygenated blood is selectively delivered to the lower extremities, causing them to be cyanotic, while the upper body remains pink.
This difference in oxygenation and color between the upper and lower body is the defining feature of differential cyanosis.

Option B: Central cyanosis involves uniform bluish discoloration of the entire body, including the skin and mucous membranes. It does not exhibit the upper-body versus lower-body difference characteristic of a reversed PDA shunt.
Option C: Peripheral cyanosis is caused by poor circulation to the extremities, often due to cold, shock, or heart failure. It is related to increased oxygen extraction in the peripheral tissues, not a central cardiac shunt.
Option D: This option is incorrect because differential cyanosis is the specific and characteristic type of cyanosis associated with a PDA with a right-to-left shunt. Central and peripheral cyanosis describe different physiological processes.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology of cyanosis in Patent Ductus Arteriosus (PDA) as background academic context rather than a clinical decision trigger.
Nurses play a crucial role in newborn screening for critical congenital heart disease (CCHD) by performing two-limb pulse oximetry. Measuring oxygen saturation in the right hand (pre-ductal) and a foot (post-ductal) is a non-invasive way to detect shunts like a PDA.
A saturation difference of more than 3% between the pre- and post-ductal sites is considered a positive screen and must be reported for further evaluation, typically an echocardiogram.
What if? If a newborn has a positive CCHD screen with differential cyanosis, the nurse's priority is to ensure hemodynamic stability and prepare for potential administration of Prostaglandin E1 (PGE1). PGE1 keeps the ductus arteriosus open, which can be life-saving in certain complex heart defects, while the team determines the exact anatomy and surgical plan.

How to Approach the Question

First, identify the key terms in the question: 'cyanosis' and 'PDA' (Patent Ductus Arteriosus).
Recall the basic pathophysiology of a PDA. It's a connection between the pulmonary artery and the aorta.
Consider the conditions under which a PDA causes cyanosis. This happens when pulmonary pressure becomes very high, reversing the shunt from left-to-right to right-to-left.
Visualize the anatomy. The PDA usually joins the aorta after the arteries to the arms and head have branched off.
Deduce the consequence: deoxygenated blood enters the descending aorta, affecting only the lower body. This specific pattern is known as 'differential cyanosis'.
Evaluate the options based on this deduction. 'Differential cyanosis' perfectly matches the description, while 'central' and 'peripheral' cyanosis have different mechanisms.

Concept Tested & Keywords

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E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 444-446

E6 Medicine Harrison 22e Part 1 p. 320-322