Cyanosed Infant Assessment
- Introduction
- Differential Diagnosis of a Cyanosed Infant
- General Approach to the Cyanotic Infant
- Differential Diagnosis
- Cardiac Causes
- Prostaglandin E1 (PG) Infusion
Summary
-
echocardiography is the gold standard for the assessment of congenital heart disease in infancy
-
all infants with central cyanosis should be commenced on parental antibiotics early until further investigation is possible.
Introduction
Central cyanosis affects 3-4% of all newborns and is a marker of significant disease. The causes are varied including
- primary pulmonary disease
- cardiac malformations
- persistant pulmonary hypertension
- sepsis
- anaemia
- asphyxia
- metabolic conditions
- methaemaglobinaemia
Differential Diagnosis of a Cyanosed Infant
|
Breathing Pattern |
Right & Left SaO2 difference |
pCO2 |
Severe Metabolic Acidosis |
Response to 100% O2 |
|
| Primary Pulmonary Disease | Tachypnoea, grunting and recession |
No difference |
|
no |
|
| Cardiac | Tachypnoea, slow/deep breathing |
+/- |
Normal or |
Present |
No significant change |
| PPHN | Tachypnoea, recession and grunting may be present |
>10 - 15% |
Normal or |
+/- |
+/- |
| Sepsis | Respiratory distress may be present |
No difference |
Normal or |
+/- |
Moderate |
|
(PPHN = Persistent Pulmonary Hypertension of the Newborn) |
|||||
History and presentation may allow the cause to be easily identified but often differentiating cause is difficult without echocardiography, especially in infants with relatively little respiratory distress.
Transporting infants with severe cyanosis is difficult whatever the aetiology and stabilisation prior to transport is particularly important. Fortunately with adequate stabilisation, the overall transport-related mortality in infants with suspected cardiac disease is 0.7%.
Echocardiography is the gold standard for the assessment of congenital heart disease in infancy.
General Approach to the Cyanotic Infant
- Confirm central cyanosis with arterial blood gas (ABG) in room air, if possible, a sample from the right arm is the best site
- Assess the history and examination for cause, including four limb BP
- an upper to lower limb systolic difference of > 10mmHg is significant and suggestive of Coarctation of the Aorta
- hypotension in a cyanotic infant is a serious finding
- Correct metabolic acidosis and systemic hypoperfusion if present with fluid boluses and bicarbonate
- Hyperoxia Test (HT)
- 100% FiO2 into headbox for > 10 min
- monitor SaO2
- Repeat ABG
-
PaO2 > 100mmHg or SaO2 increase by 15%: pulmonary disease likely
- PaO2 < 70mmHg, rise by < 30mmHg or SaO2 unchanged: cardiac cause or PPHN likely
- Total Anomalous Pulmonary Venous Drainage (TAPVD) and Hypoplastic Left Heart syndrome may respond
-
Pulmonary disease with a massive intrapulmonary shunt may not respond
-
- Limitations of HT
- HT is not as reliable as an echocardiogram and is not as important as resuscitation and attendance to cardiorespiratory support, especially if acidosis or respiratory distress is present
- HT has many limitations especially when only saturations are measured and not arterial PaO2 and should only be used in conjunction with a thorough clinical assessment
- Assess right and left sided SaO2 for any ductal difference
- CXR and ECG if possible
- Intubation and paralysis if significant distress
- Two IV lines ideally or UVC
- Parental antibiotics (preferably after blood cultures taken)
- Prostaglandin E1 infusion if duct dependent cardiac disease is suspected
- Consider inotrope support to maintain BP/improve cardiac contractility
- Infants should be transferred to a centre with Paediatric Cardiology and Cardiac Surgery facilities readily available
Differential Diagnosis
Sepsis with a low output state may cause
Differentiating the infant in severe septic shock from other causes of cyanosis is very difficult and no safe clinical measures exist. Thus, generally all infants with central cyanosis should be commenced on parental antibiotics early until further investigation is possible.
PPHN results from an altered pulmonary vasoreactivity and raised pulmonary vascular resistance, this causes a right to left ductal shunt. Most infants present with respiratory distress and cyanosis. Usually the infant is tachypnoeic, shows labile oxygenation and has evidence of right ventricular strain (prominent right ventricle impulse and tricuspid regurgitation murmur). There is usually a pre- and post-ductal difference of 10-15% in SaO2 and 10-15mmHg PaO2. Despite this a degree of clinical variability exists depending on the severity, stage of disease and underlying pathology.
If PPHN is suspected hyperventilation for 10 minutes is a useful clinical test when other investigative options are unavailable. Infants with PPHN show improved oxygenation (PaO2 increasing by >30mmHg) when pH is raised to ³ 7.55. Prolonged hyperventilation is not recommended due to the cerebral effects of prolonged hypocapnia.
Differentiating PPHN from ductal dependent pulmonary cardiac lesions can be very difficult; if uncertainty exists a PG infusion is generally the safest option for transport and infants with PPHN may show some improvement on infusions of 50-60 nanog/kg/min.
Cardiac Causes
Generally an infant with cyanosis and a murmur has a high probability of a cardiac cause, absence of pulses further raises the probability.
Infants presenting with cyanosis due to a cardiac cause have a high probability of a ductal dependent lesion involving either:
- Ductal Dependent Pulmonary Circulation presenting with
- cyanosis
- tachypnoea without respiratory distress
- adequate perfusion initially
- such as
- critical pulmonary stenosis
- transposition of the great vessels
- Ductal Dependent Systemic Circulation (critically obstructed systemic circulation) presenting as
- cardiac failure with systemic hypoperfusionhypoperfusion
- poor or absent peripheral pulses
- increasing metabolic acidosis
- cyanosis may not develop until the latter stages of the clinical course
- Such as
- coarctation of the aorta
- hypoplastic left heart syndrome
- critical aortic stenosis
-
Management
Aim to maintain adequate tissue perfusion and ductal patency rather than correcting the cyanosis.-
minimise pulmonary blood flow
-
moderate PEEP (4-6 cm H20)
-
ventilate in air if possible
-
aim for a CO2 of 37 - 45 mmHg
-
SaO2 75 - 85%
-
-
maximise tissue perfusion
-
fluid resuscitation (saline 10ml/kg boluses)
-
low dose inotropes (dopamine/dobutamine) - further details in section on management of shock
-
sodium bicarbonate if BE > -10 (dose (mmol) = BE *wt/4)
-
-
consider paralysis if infant distressed
-
- achieve ductal patency with Prostaglandin E1
-
Prostaglandin E1 (PG) Infusion
- When to give?
In a cyanotic infant in whom cardiac disease is suspected a low threshold for starting PG is needed. Even in a stable infant the risk of withholding PG is usually greater than the risks associated with PG due to the risk of rapid clinical deterioration when the duct closes, especially in a transport environment.
There is evidence that infants with suspected duct dependent cardiac lesions transported with prostaglandin have better outcomes than those in which prostaglandin is withheld and the overall risk to the infant is low. There are no true contraindications to PG but infants with TAVPD may worsen on PG.
If the diagnosis is uncertain a trial of PG for 30 to 60 minutes with repeat abg may be warranted and will usually outweigh the risks of delaying treatment.
- Dose
When the duct is still open the priority is to prevent further loss of patency, usually a starting dose of 10 ncg/kg/min infusion in 5% dextrose or Normal Saline is adequate. If no improvement in SaO2 then increase dose by 10 nanogram/kg/min increments up to 50 nanogram/kg/min until SaO2 improves. Prostaglandin can be given via a peripheral line, UVC or UAC.
Infants in extremis will usually have a closed duct and a higher starting dose of 100 ncg/kg/min will be required to reopen the duct, when saturations improve then dose can be decreased to a dose to maintain ductal patency.
- Side Effects
Most frequent side effects include
- fever 12%
- apnoea 12%
- flushing 10%
- hypotension
Apnoea will rarely occur at 10 ncg/kg/min and apnoea is not an indication to decrease the dose if the infant is responding clinically, rather respiratory support is warranted. The likelihood of apnoea is very high at a dose of 100 ncg/kg/min and most infants on this dose should have ventilatory support.
Close observation is mandatory following commencement of PG infusion, and assisted ventilation and volume expansion or inotrope infusion are frquently required.
- Who to intubate?
The threshold to intubate an infant on a PG infusion will be lower in a transport or remote setting. Factors to consider include
- presence of apnoea
- the distance to the receiving hospital
- gestation of the infant
- clinical state of the infant (metabolic acidosis, shock, severe distress and tachypnoea)
- high PG dose required to achieve ductal patency
Thus in a stable infant with a PG responsive ductal lesion transport without intubation maybe appropriate. Conversely, it would generally be appropriate to electively intubate an infant requiring high dose PG (although these infants usually require respiratory support for other reasons).
References
Penny DJ, Shekerdemian LS. Management of the neonate with symptomatic congenital heart disease. Arch Dis Child Fetal Neonatal Ed 2001; 84: F141 - F145.
Hellstr?m-Westas L et al. Long-distance transports of newborn infants with congenital heart disease. Pediatr Cardiol 2001; 22: 380-384
Buck ML. Prostaglandin E1 treatment of congenital heart disease: use prior to neonatal transport. DICP Ann Pharmacother 1991; 25: 408 - 9
Barry PW, Ralston C. Adverse events occurring during interhospital transfer of the critically ill. Arch Dis Child 1994; 71: 8-11
Jaimovich DG, Vidyasagar D (Ed). Handbook of pediatric and neonatal transport medicine. Ch 8. 2nd Ed. 2002. Hanley & Belfus. Pp 93 - 125
Myung K Park. Pediatric cardiology for practitioners. 3rd Ed. 1996. Mosby-Year Book (St Louis)
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