Neonatal cyanosis and collapsed neonate

Overview & Definition

Picture the infant first: a two-day-old term baby, previously feeding well, now dusky and limp in the mother's arms, the tongue and lips a slate blue, breathing fast but not particularly hard. That is the prototypical presentation — central cyanosis, often with surprisingly little respiratory distress, on the second or third day of life. The colour change is not subtle, and the tempo is the clue: a baby who was well hours ago is now blue. The first question is not "what is the diagnosis?" but "is this an emergency?" and the answer is almost always yes. [3]

Cyanosis is the blue discolouration of skin and mucous membranes that appears when the concentration of deoxyhaemoglobin in capillary blood exceeds about 3 g/dL. Two consequences follow that examiners test. First, cyanosis is a late and unreliable sign of hypoxaemia — the infant can be profoundly hypoxic long before looking blue. Second, an anaemic infant may be severely hypoxaemic and never turn blue, because there is not enough haemoglobin to generate the threshold concentration of deoxyhaemoglobin, while a polycythaemic infant looks blue at milder desaturation. The colour, then, is a trigger for action, not a measurement of the oxygen deficit. [2]

The decisive bedside act is to tell central cyanosis from peripheral acrocyanosis. Central cyanosis means the tongue, lips and mucous membranes are blue, signalling arterial desaturation — this is pathological and demands investigation. Peripheral (acro)cyanosis means the hands and feet are blue while the tongue stays pink; it is common and benign in the first 24 hours, caused by slow peripheral flow, and it resolves with warming. The trap is the infant whose tongue the clinician never checks, dismissing the baby as "just a bit cold". Always look at the tongue. [3]

The collapsed neonate is the severe end of the same spectrum — a baby in shock, with tachycardia or bradycardia, weak pulses, a capillary refill over three seconds, cold mottled peripheries, poor tone and a metabolic acidosis. In a term infant, collapse in the first days to weeks is most often a duct-dependent cardiac lesion whose systemic or pulmonary blood flow depended on a now-closing ductus arteriosus; the differential also holds sepsis, hypoxaemia from pulmonary disease, and metabolic collapse. Re-opening the ductus is life-saving, and it cannot wait for the echocardiogram. [2] [3]

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