Dr Katherine Hill, Dr Oluwaseyi Olatimilehin. Edited for PaediatricFOAM by Dr Jennifer Tsang
Imagine this scenario – you are a neonatal ST2 who’s been called to attend a term forceps delivery on labour suite. Once delivered, the baby is pale and floppy so the midwife brings the baby across to the resuscitaire.
You dry and wrap the baby, pop a hat on and listen to the heart rate which is >100bpm, however, the baby is not breathing… You give 5 inflations breaths as per NLS and there’s good chest rise and the heart rate is still above 100bpm.
Baby’s now crying but still looks blue. You pop a sats probe on and at 3 minutes, the saturations are 65% so you titrate the FiO2 up to 30%…
At 6 minutes, the sats now 70% and the baby still looks dusky so you increase the FiO2 up to 40%…
By 15 minutes, the baby’s sats are now 92% in 70% FiO2. However, whenever you try to wean the oxygen, the sats drop and the baby becomes cyanosed again…
You decide to transfer the baby to the neonatal unit for further work-up.
What is cyanosis?
Cyan is the Latin word for “blue”.
Cyanosis occurs when the absolute amount of deoxygenated haemoglobin is greater than 3g/dL – this typically correlates with oxygen saturations of <85%.
Cyanosis is easiest to spot in areas with good superficial blood supply and thin skin such as the lips, nose, earlobes, mouth and the tips of fingers and toes. It’s important to familiarise yourself with the appearance of cyanosis in different skin colours as it has been highlighted that we’re not as adept at recognising cyanosis in darker skin tones.
Since cyanosis is a clinical sign, a proper examination is key to working out the underlying cause.
When describing the pattern of cyanosis, it can be broken down into:
- Central (or generalised) cyanosis of the body and visible mucous membranes
- Peripheral cyanosis of the extremities e.g. fingers and toes
- Differential cyanosis, where there is asymmetry in the upper and lower body
This becomes important when considering differentials and thinking about serious causes you don’t want to miss.
| Back to our case scenario… You arrive on the neonatal unit with the baby. The nurses pop them into an incubator in the same amount of oxygen. What’s next? Remember the basics – start with an ABCDE assessment. In this case, our baby is: A: Crying and maintaining its own airway B: No signs of respiratory distress but ongoing FiO2 requirement up to 40% C: There is a blue tinge to the skin, but baby is well perfused, normal CRT and femoral pulses are palpable D: Blood glucose 3.6, PEARL, normal tone and moving all four limbs E: No rashes/bruises |
Investigations / Management
When considering investigations and management, it’s important to think about what the underlying cause might be.
- Pre- and post-ductal saturations… Could this be PPHN?
- Blood gas… Why? What are we looking for?
- CXR… Could this be TTN/RDS? A pneumothorax or congenital pneumonia?
- Echocardiogram… Looking for signs of PPHN or congenital heart defects, although this might not be readily available….
- Septic screen… infection must always be ruled out!
What are the possible causes of cyanosis in a newborn?
There are lots of possibilities, including cardiac, respiratory, neurological, metabolic and haematological disorders so let’s go back to first principles…
Figure 1. demonstrates how we can use our knowledge of physiology to think about potential problem areas. For example, is this an issue with the lungs oxygenating the blood? Or is there a plumbing issue in/around the heart causing problems with supply to the rest of the body? Or is the problem more central i.e. the brain which is the central control for breathing?
Hypoxia is a common newborn scenario – the most common underlying causes are usually either respiratory or cardiac in origin so should be first in your differential list. Here, we’ll also go through a few other causes too.
Respiratory
Respiratory disease is one of the most common reasons for a term baby to be admitted to the neonatal unit, making up around 25% of all term admissions. Many of these will be due to TTN (Transient Tachypnoea of the Newborn) or RDS (Respiratory Distress Syndrome).
Although, a proportion of patients may have a pneumothorax or congenital pneumonia and an even smaller number may have meconium aspiration syndrome (MAS, if there’s a history of meconium at delivery), PPHN (persistent pulmonary hypertension – often secondary to another cause) or an underlying congenital abnormality in the airway or lungs.
Here’s a list of some respiratory causes, their pathophysiology, clinical features and associated risk factors:
| Cause: | Pathophysiology: | Risk Factors: | Clinical Features: |
| TTN | Persistent lung fluid | C-section Maternal diabetes Large baby Male | Tachypnoea Often no oxygen requirement Improves with time CXR: fluid in fissure, vascular markings |
| RDS | Surfactant deficiency Immature lung | Male Maternal diabetes Preterm | Tachypnoea Hypoxia +/- cyanosis Worsens with time CXR: ground glass, atelectasis, air bronchograms |
| MAS | Lung irritation/obstruction from meconium | Post-term Meconium at delivery | Tachypnoea Hypoxia +/- cyanosis Can cause PPHN CXR: hyperinflation, asymmetric patchy pulmonary opacities, pneumothorax, multifocal consolidation |
| Congenital Lung Malformations | Malformation due to abnormalities during embryogenesis | Unknown | Increased respiratory effort, tachypnoea, cyanosis CXR: pneumothorax, multicystic (air-filled) lesion (can also be solid) |
Cardiac
Congenital heart disease occurs in about 8 babies out of every 1,000 (0.8%). Cardiac causes are more likely to be associated with other clinical features such as sweating/breathlessness with feeds and progressively reduced feeding.
Reduced cardiac output in heart failure and shock can lead to peripheral cyanosis – the lack of pressure prevents adequate supply of oxygen-rich blood to the extremities. Hypotension also produces reflex cutaneous vasoconstriction to shunt blood to the internal organs. This redistribution of blood flow from the extremities causes peripheral cyanosis.
For further reading, take a look at this article.
Infection
Acute hypoxic respiratory failure and acute lung injury are common respiratory complications associated with severe sepsis. Destruction of the alveolar capillary membrane can lead to refractory hypoxia. Metabolism and oxygen consumption are increased during sepsis which can also lead to an oxygen requirement.
| Back to our baby on the unit… You’ve turned the oxygen up to 100% as the baby’s saturations are still poor. The nurse hands you the first gas – thoughts? Blood Gas: pH 7.32 pCO2 5.12 pO2 12.6 HCo3 24 Hb 167 MetHb 3% (normal range <1.5%) Glucose 3.6 Lactate 1 |
Haemoglobinopathies
Methaemoglobinaemia and sulfhaemoglobinaemia are both conditions where the oxygen carrying capacity of red cells is reduced due to oxidation of some of the heme iron. Sulfhaemoglobin being caused by sulfur ion and methhaemoglobin caused by either enzymes (acquired) or substitution of a haem amino acid causing methylation.
Both methaemoglobin and sulfhaemoglobin are identifiable on a standard blood gas machine. The presence of met- and sulfhaemoglobin can affect the pulse oximetry reading and cause central cyanosis with an otherwise well-looking baby.
Read more about methaemoglobinaemia here.
Benign
Acrocyanosis describes bluish discoloration around the mouth and extremities whilst the rest of the body is pink. It is a benign finding often seen in healthy babies in the first few days of life due to initial peripheral vasoconstriction. It can also be seen later in infants when they’re crying, vomiting, coughing or holding their breath.
Key points
Blue babies in the immediate newborn period aren’t uncommon but there are a wide range of causes. We need to be able to:
- Recognise cyanosis in newborns, especially non-Caucasian babies
- Understand the physiological basis for cyanosis and hypoxia
- Initiate investigations and management, tailored according to our differentials
A final note…
When you hear hooves, sometimes it really is a zebra, not a horse… Remember to look carefully and interpret the whole blood gas and think again when the baby in front of you doesn’t fit with the investigations, including the sats monitor!
Authors Dr Katherine Hill, ST5 Paediatric Resident; Dr Oluwaseyi Olatimilehin, Consultant Neonatologist both at University Hospital of North Midlands, UK