49. Cyanosis / hypoxia Flashcards
Cyanosis.
a) Define
b) Relationship between Hb level and cyanosis
c) Patients who are centrally cyanosed probably have an oxygen saturation (SpO2) of less than…?
a) Blue discolouration of the skin/ mucous membranes due to high levels of deoxygenated Hb
b) - Anaemia - develop cyanosis at lower oxygen saturations (SpO2 %) than average
- Polycythaemia - develop cyanosis at higher oxygen saturations than average
c) SpO2 < 85%
Peripheral vs. central cyanosis
a) Causes
b) Presentation
a) - Central - cyanotic cardiac or respiratory disease, causing failure to oxygenate blood effectively
(note: will also usually be peripherally cyanosed as well)
- Peripheral - could be due to more local causes (eg. local vasoconstriction or reduced systemic perfusion - due to: CCF, shock, peripheral circulation disorders, cold temperature)
b) - Central - affects lips and tongue (likely also affects peripheries)
- Peripheral - affects hands/ feet or local affected area (usually most intense in nail beds)
Central cyanosis in neonates: differentials
- cardiac
- respiratory
- other
Cyanotic congential heart disease: right-to-left shunting
- Truncus arteriosis
- TGA
- Tricuspid atresia
- Tetralogy of Fallot
- TAPVR
Respiratory causes:
- Respiratory distress syndrome.
- Birth asphyxia, birth injury or haemorrhage.
- Transient tachypnoea of the newborn.
- Pneumothorax.
- Meconium aspiration.
- Pulmonary oedema.
- Congenital diaphragmatic hernia.
- Tracheo-oesophageal fistula.
- Pleural effusion.
- Obstruction of the upper respiratory tract - for example, in Pierre Robin sequence or choanal atresia.
Other.
- Sepsis
- Metabolic
- Seizures
Differential diagnosis in adults.
a) Central
b) Peripheral*
*any cause of central cyanosis may also cause peripheral cyanosis
a) Respiratory disease:
- Pulmonary oedema
- Pulmonary embolism
- Decreased FiO2 (eg, high altitude)
- Pneumonia
- COPD/ acute severe asthma
- ARDS
Right-to-left cardiac shunt:
- Cyanotic congenital heart disease,
- Eisenmenger’s syndrome
Haemoglobin abnormalities:
- polycythaemia
- abnormal haemoglobins (eg. sulfhaemoglobinaemia due to use of sulfonamides)
b) Reduced CO:
- CCF
- Shock
Peripheral arterial disease:
- Chronic - atheromatous
- Acute - thrombo-embolism
Local vasoconstriction:
- Raynaud’s
- Cold exposure
- Beta blockers
Venous obstruction
- DVT
- SVC/IVC obstruction
Cyanosis: history
a) HPC
b) Ass sx
c) PMHx
d) DHx
e) FHx
f) SHx
a) - Site - central or peripheral
- Onset - sudden or gradual
- Timing - duration? progressive or gradual?
- E/R factors - cold, drugs, other
b) - Resp symptoms - cough, SOB, wheeze, haemoptysis, recent DVT/PE
- Cardiac - pain, leg swelling, etc.
- Other
c) - Hx of cyanosis
- Chronic respiratory disease
- Hx of DVT/PE
- Congenital heart disease
- Blood disorder
d) - Beta-blockers
e) - FHx heart/resp disease
- FHx of cyanosis
f) - Smoking, alcohol
- Carers, mobility, etc.
Cyanosis: examination
a) Peripheral signs that may indicate diagnosis
b) Signs in the eyes, mouth, neck
c) Chest
a) - Clubbing - ?IPF, cyanotic heart, etc.
- Tar staining
- Poor peripheral pulses - ?PVD
b) - Anaemia
- Central cyanosis
- JVP
c) - Heart sounds - ?murmurs
- Resp - ?consolidation, ?fibrosis, ?oedema, etc.
Investigating cyanosis/hypoxia.
a) Bedside
b) Bloods
c) Imaging
d) Special tests
a) - A-E assessment
- ECG - ACS, PE, etc.
- Sputum culture/ viral PCR/ ?COVID-19 test
- ?Doppler US leg
b) - ABG!! (do this on B of A-E assessment)
- FBC + CRP: anaemia/polycythaemia, infection
- Blood cultures
- Other routine bloods
c) - CXR: pneumonia, pulmonary infarction, cardiac failure.
- CTPA or V/Q scan
- ECHO
d) - ?Angiography: acute arterial occlusion.
- ?Haemoglobin spectroscopy: methaemoglobinaemia, sulfhaemoglobinaemia.
Managing cyanosis/hypoxia.
a) First
b) If oxygen does not increase >95% on high-flow…?
c) Then
a) Oxygen therapy for patients who are hypoxic
b) - Escalate
- May have a R-L shunt or severe V/Q mismatch
c) Treatment of the underlying cause
