21. Tachyarrhythmias Flashcards
What are the causes of intra-operative tachyarrythmias?
> Patient factors:
> Patient factors:
All patients undergoing anaesthesia
and surgery are
at risk of intra-operative arrhythmias.
However, certain patients are at increased risk:
1
• Pre-existing cardiac disease,
e.g. ischaemic heart disease or
valvular heart disease
2
• Pre-existing arrhythmia,
e.g. atrial fibrillation or
Wolff–Parkinson–White syndrome
3
• Pre-existing electrolyte disturbances,
e.g.
diuretic-induced hypokalaemia and hypomagnesaemia
4
• Endocrine disease,
e.g. thyrotoxicosis.
What are the causes of intra-operative tachyarrythmias?
> Anaesthetic factors:
> Anaesthetic factors:
General and regional anaesthetic techniques can
have significant effects on cardiac function:
1
• Drug-induced alteration in
cardiac preload, contractility and afterload
2
• Effects on coronary perfusion pressure
3
• Effects on myocardial irritability
4
• Effects on autonomic nervous system
5
• Effects of hypoxia and hypercapnia
6
• Electrolyte disturbances
(either pre-existing or iatrogenic
from fluid therapy)
7
• Effects of intravascular devices
(e.g. central venous lines) advanced
too far and entering the right atrium
What are the causes of intra-operative tachyarrythmias?
> Surgical factors:
1
• Effects of pneumoperitoneum
related to laparoscopic surgery,
e.g. vagal response,
reduced venous return,
fall in cardiac index or rise in SVR
2
• Effects of hypercapnia related
to laparoscopic surgery, e.g.
arrhythmias
3
• Effects of rapid fluid shifts
4
• Systemic inflammatory
response syndrome (SIRS) induced
by tissue trauma
Describe your management of an intra-operative tachyarrhythmia.
Management of intra-operative
tachyarrhythmia follows general principles
applicable to all tachyarrhythmias and specific treatments for certain types of tachyarrhythmias.
General management principles:
1
> Consider calling for assistance
depending on the haemodynamic
consequences of the arrhythmia.
2
> Diagnose the arrhythmia and
establish the haemodynamic consequences –
check blood pressure and end-tidal CO2.
3
> Attempt to identify and treat
the cause of the arrhythmia,
e.g. adjust CVP line tip position or correct electrolyte disturbances.
4
> Attempt to maximise myocardial oxygen delivery
by maintaining arterial oxygen content
and coronary perfusion pressure.
5
> Check and correct electrolyte disturbances (potassium and magnesium):
arterial blood gas analysis is the
fastest method of obtaining potassium
concentration
(if hypokalaemia is present,
in the majority of cases
hypomagnesaemia will also be present).
6
> Attempt to correct any identified acid–base abnormalities detected on arterial blood gas
> Broad complex tachycardia
(VF/VT/SVT with aberrant conduction)
Specific management:
• If there is no pulse, follow ALS protocol.
• If there is a pulse assess
the haemodynamic consequences:
• Systolic <90 mmHg/heart rate >150:
Synchronised DC cardioversion (up to three shocks).
If refractory consider amiodarone
150 mg over 10 minutes
followed by 300 mg over 1 hour
and repeat shock if necessary.
Consider lignocaine and overdrive pacing.
• Systolic >90 mmHg/heart rate <150:
Correct K+ (>4.0 mmol/L)
and Mg2+ (>1.0 mmol/L).
Administer amiodarone 150 mg IV over
10 minutes or
lignocaine 50 mg over 2 minutes repeated every 5 minutes up to a total dose of 200 mg.
> Narrow complex tachycardia (SVT/atrial flutter)
• If there is no pulse, follow the ALS protocol.
• If the rhythm is atrial fibrillation (AF),
follow AF algorithm.
• If there is a pulse and
atrial fibrillation is excluded,
assess the haemodynamic consequences:
• Systolic <90 mmHg/
ventricular rate >200:
Synchronised DC cardioversion (up to three shocks).
Consider amiodarone 150 mg over 10 minutes
followed by 300 mg over 1 hour and
repeat shock if necessary.
• Systolic >90 mmHg/ventricular rate <200:
Attempt vagal manoeuvre (e.g. carotid sinus massage).
Consider adenosine boluses
6 mg, followed by up to three 12 mg doses.
If resistant, consider use of
esmolol, amiodarone, digoxin or verapamil.
> Atrial fibrillation
Critical
Management depends on the time of onset
(i.e. acute/chronic AF and subsequent risk of systemic embolisation if sinus rhythm is restored),
ventricular rate and the haemodynamic consequences
Critical AF,
ventricular rate >150,
hypotension and impaired perfusion
> Heparinise if feasible
(note risk of intra-operative bleeding)
> Administer synchronised DC cardioversion
> Administer amiodarone 300 mg IV over 1 hour followed by 900 mg over the following 23 hours
Intermediate AF,
ventricular rate 100–150
If associated with haemodynamic compromise:
> Onset <24 hours:
Heparinise and
administer synchronised DC cardioversion.
Consider amiodarone IV 300 mg over 1 hour.
> Onset >24 hours:
Control rate initially with amiodarone IV 300 mg over
1 hour.
Heparinise and later perform synchronised DC cardioversion.
If associated with normal haemodynamics:
> Onset <24 hours:
Heparinise and administer amiodarone IV 300 mg
over 1 hour.
Consider flecainide.
Synchronised DC cardioversion may be
required.
> Onset >24 hours:
Control rate initially with digoxin, verapamil or
β-blockers.
Heparinise and later perform synchronised DC cardioversion.
Low-risk AF, ventricular Rate <100 with good perfusion
Low-risk AF, ventricular Rate <100 with good perfusion
> Onset <24 hours:
Heparinise and administer
amiodarone IV 300 mg over 1 hour.
Consider flecainide.
> Onset >24 hours:
Heparinise and then later perform synchronised DC
cardioversion.
Post-operative:
Post-operative:
All patients who have suffered
significant intra-operative arrhythmias
should have cardiac monitoring in the initial post-operative period
(including 12-lead ECG)
and relevant cardiac follow-up if indicated.
ALS protocols have not been covered here but are likely to be examined in the OSCE.
