22. Venous air embolism (VAE)

Question 1

Intro

Answer 1

Venous air embolism (VAE) is a potential complication of many surgical procedures.

The clinical features range from

sub-clinical to life-threatening
cardiovascular collapse
depending upon the rate and
volume of gas that is entrained into the circulation.

Examiners will expect an understanding of the types of procedures that are associated with an increased risk of VAE, and also the ability to diagnose and manage the problem.

Question 2

What procedures are associated

with a high risk of VAE?

Answer 2

1
> Neurosurgery, particularly
surgery in the sitting position and surgery
involving the cranium and dura.

2
> Laparoscopic surgery with
risk of direct intravascular gas insufflation.

3
> Head and neck surgery with
large areas of tissue exposed, often with
vessels at subatmospheric pressure.

4
> Orthopaedic surgery,
e.g. polytrauma, cementing and
reaming in long bone surgery

5
> Insertion of intravascular devices,
e.g. central venous cannulation.

Question 3

How can you diagnose VAE?

Answer 3

Symptoms and signs are
primarily those of cardiovascular collapse

(hypotension, tachycardia,
arrhythmias and arterial desaturation)

caused by the air embolus
acting as an intracardiac air lock.

In the correct clinical setting,
suspicion for VAE must always remain high.

In certain high-risk procedures 
(e.g. neurosurgery in the sitting position)
monitoring should be used electively 
to aid early VAE detection and 
may include the following:

> Listen for audible hissing
as gas enters the circulation.

> ECG:

VAE is associated with an increase in pulmonary vascular resistance and the development of right ventricular dysfunction causing arrhythmias and possibly a right ventricular strain pattern.

> Capnography: fall in end-tidal CO2.

> CVP increases.

> Precordial stethoscope: classic
‘millwheel murmur’.
This is insensitive and
a late sign.

> Pulmonary artery pressure increases.

> Oesophageal Doppler is
extremely useful in early detection of VAE.

> Transoesophageal echocardiography (TOE):

Possibly the gold standard.

Allows localisation of air to a specific cardiac chamber while enabling assessment of cardiac function.

Question 4

What is the management of a suspected VAE?

Answer 4

State that this is an anaesthetic emergency,
and that you would call for
senior anaesthetic assistance
 and make a rapid 
but thorough assessment of the patient.

1
> Inform the surgeon who may be able to

prevent further embolisation by compression
of the surgical site

or

flooding the surgical site with saline.

2
> Administer 100% oxygen and
discontinue nitrous oxide,

which will increase bubble size
due to its high solubility.

3
> Increase CVP by tilting the patient
slightly head-down,
administer fluid and increase PEEP.

4
> Position patient in

left lateral head-down
position if feasible,

this may prevent embolisation

into the pulmonary artery.

In this position consider attempting
to aspirate the air via a CVP line.

5
> Cardiovascular support with fluid 
and inotropic support may be required.
CPR may also become 
necessary if the situation deteriorates.

6
> Terminate surgery as soon as safely possible.

7
> Arrange appropriate post-operative care (ITU or HDU).

8
> Document events and complete a critical incident form.

9
> Explain the event to the patient when possible.