5. Bradycardia

Question 1

What is the definition of

bradycardia?

Answer 1

In an adult a bradycardia is defined
as an HR <60 bpm,

but in reality you should take
into consideration any rate that
is inappropriately slow for that
individual and haemodynamic state.

Question 2

What are the causes of intra-operative bradycardia?

Answer 2

1
> Hypoxia:
This is the most important cause.

2
> Vagal stimulation: 
This can be caused during eye surgery, 
dilation of the anus and cervix, 
mesenteric retraction, 
laparoscopy and airway manipulation.

3
> Drugs:

• Inhalational agents
(enflurane and halothane > isoflurane)

• Opioids (fentanyl, remifentanil and morphine)
• Anticholinesterases (neostigmine)

• Muscle relaxants
(vecuronium, tubocurarine and second dose of suxamethonium)

• Vasopressors
(metaraminol and phenylephrine can cause a reflex
bradycardia)

• β-Blockers that patient may be on pre-operatively

Question 3

Other Causes

4

Answer 3

> Neuroaxial blocks:

High spinal blockade to T1–T4 will compromise the cardiac sympathetic accelerator fibres.

> Metabolic:
Hypothyroidism and hyperkalaemia.

> Disease:
Ischaemic heart disease and
raised intracranial pressure.

> Normal: Athletes.

Question 4

> Drugs causing hypoxia

Answer 4

3
> Drugs:

• Inhalational agents
(enflurane and halothane > isoflurane)

• Opioids (fentanyl, remifentanil and morphine)
• Anticholinesterases (neostigmine)

• Muscle relaxants
(vecuronium, tubocurarine and
second dose of suxamethonium)

• Vasopressors
(metaraminol and phenylephrine
can cause a reflex bradycardia)

• β-Blockers that patient may be on pre-operatively

Question 5

How would you manage an anaesthetised patient who developed bradycardia intra-operatively?

Answer 5

Remember that you need to assess
and resuscitate the patient simultaneously, using an

ABC approach and systematically
work your way from the patient back
towards the anaesthetic machine so as not to
miss anything.

The haemodynamic consequences
of the bradycardia will
determine the urgency of the situation.

> Immediate management:

• State that this is an anaesthetic emergency
and that you would call for
senior anaesthetic assistance.

• Ask the surgeon to stop as this
will eliminate any surgical vagal
stimulation.

• Administer 100% oxygen and
hand-ventilate the patient.

This allows you to assess lung compliance and adequacy of ventilation.

• Reduce or even stop the volatile agent.
Check the MAC and end-tidal
concentration of the volatile agent.

• Administer atropine 0.6 mg
(10 μg/kg) and flush.
Repeat if necessary up to a maximum of 3 mg.

• Check BP and if hypotensive give fluid bolus (10 mL/kg of either crystalloid or colloid).

Repeat if necessary.
Bolus vasopressors agents,
e.g. ephedrine, as required.

• If there is no satisfactory response,
reassess the situation starting at
ABC and treat the probable cause as appropriate.

Question 6

> Management options in persistent bradycardia:

Answer 6

1
• Ask for the crash trolley.

2
• Administer adrenaline
2–10 μg/min of
1:10 000 preparation.

3
• Commence transcutaneous pacing

(this can be done using defibrillator
chest pads with the
defibrillator machine set to pacing mode at a rate
of 50–60 bpm).

Expert help will later be needed to arrange transvenous pacing.

4
• If HR <30 with significant haemodynamic compromise, commence CPR and
follow ALS algorithm for asystole.

5
• Terminate surgery as soon as safely possible.

6
• Arrange transfer to ICU for
further investigation, advanced monitoring
and management.

7
• Document sequence of events in medical notes.

8
• Complete a critical incident form.