ALARMING CYANOSIS

Describe the management of a patient with central cyanosis

Actions 

1. Check the pulse – if absent, treat for cardiac arrest.
2. Check gas flow settings on rotameters.
3. Immediately increase FIO2 and decrease the vaporiser setting.
4. Monitor ECG, SaO2, and ETCO2.

Ventilation

Controlled ventilation

Does the chest move normally?

If not, attempt manual inflation using a reservoir bag and breathing circuit.

• Lungs are easy to inflate – fault in ventilator, gas supply or breathing system.
• Lungs impossible or difficult to inflate:
• (a) Check endotracheal tube (ETT):
• ? misplaced in the oesophagus or pharynx (check ETCO2)
• ? blocked, kinked (inspect with a laryngoscope and pass the stout catheter through the tube to check patency)
• ? herniated cuff (check pharynx dry, then deflate cuff)
• ? bronchial intubation (withdraw tube slightly)
• (b) Check chest: see FAULT IN CHEST.

If the chest moves normally, there is a fault in:

• Chest – see FAULT IN CHEST
• Circulation – see FAULT IN CIRCULATION
• Oxygen source – see FAULT IN OXYGEN SUPPLY.

Spontaneous ventilation

Breathing appears obstructed. Fault may be in:

• Airway – if not intubated, check pharynx and larynx are clear and intubate if necessary; if intubated, check the ET tube
• Chest – see FAULT IN CHEST.

Breathing appears normal. Fault may be in:

• Chest – see FAULT IN CHEST
• Circulation – see FAULT IN CIRCULATION
• Oxygen source – see FAULT IN OXYGEN SUPPLY.

Respiratory minute volume seems inadequate. Intubate and ventilate, if necessary. Treat common causes:

• Excessive volatile agent
• Excessive narcotic agent
• Muscle relaxant is still active.

Fault in chest

• Bronchospasm – listen for wheeze.
• Note that severe bronchospasm may be silent.
• Fluid in alveoli – listen for crackles and wheezing, and check for (pink) frothy sputum.
• Pneumothorax – absent breath sounds over the upper chest with hyper-resonant percussion note (may be bilateral).
• Haemothorax or pleural effusion – absent breath sounds over-dependent part of the lung.

Fault in circulation

There is a weak pulse:

• Venous return reduced
• Severe heart failure
• Massive pulmonary embolism
• Severe adverse drug reaction.

Fault in oxygen supply

• Source exhausted.
• Machine leaking (measure FIO2 with oxygen meter on the inspiratory limb of the breathing system).
• Pipeline cross-connection (check with FIO2 meter, changes to the cylinder supply if in any doubt).
• Breathing system:
• Fresh gas supply inadequate
• Leak
• Incorrect assembly.

Miscellaneous causes (rare)

• Malignant hyperpyrexia.
• Methaemoglobinaemia – consider if patient on sodium nitroprusside, GTN, prilocaine, or sulphonamides. Give methylene blue 1mg/kg. Sometimes the cause is not obvious. If in doubt:
• Change ETT
• Ventilate with expired air as a temporary measure
• Change the anaesthetic machine
• Use gas cylinders.

Remember the common causes of cyanosis:

• Misplaced ETT
• Disconnection
• Obstruction in the breathing circuit
• Oxygen supply failure
• Cardiac arrest.

Capnography and oxygen meters are vital aids in diagnosis.