Final answer:
Cyanosis in a newborn with a high heart rate is a critical sign of insufficient oxygenation and may be caused by heart defects. It requires prompt medical attention and is part of the newborn's Apgar score assessment.
Step-by-step explanation:
Cyanosis in a newborn baby, even with a heart rate (HR) greater than 100 beats per minute, is a significant medical sign. During the Apgar test, which assesses a newborn's health immediately after birth, five criteria are evaluated: skin color, heart rate, reflex, muscle tone, and respiration. Cyanosis refers to a blue or purple coloration of the skin that indicates an insufficient supply of oxygenated blood to the body's tissues. Heart rate and respiration are two of the most critical measurements in the Apgar score. A newborn with cyanosis might still have a heart rate above 100, but this can be associated with severe conditions like tetralogy of Fallot or patent foramen ovale. Prompt medical attention is vital for infants with cyanosis, regardless of a high heart rate.