The emergency treatment of bradycardia depends upon two important factors: the clinical condition of the patient and the risk of asystole. Give O 2 , insert an IV cannula and follow the 2010 European Resuscitation Council Guidelines shown opposite ( www.resus.org.uk ).
Atropine is the fi rst-line drug. The standard dose is 500mcg IV, which may be repeated to a total of 3mg. Further doses are not effective and may result in toxic effects (eg psychosis, urinary retention).
Adrenaline (epinephrine) can be used as a temporizing measure prior to transvenous pacing if an external pacemaker is not available. Give by controlled infusion at 2–10mcg/min, titrating up according to response (6mg adrenaline in 500mL 0.9 % saline infused at 10–50mL/hr).
External transcutaneous pacing is available on most defi brillators. It allows a pacing current to be passed between 2 adhesive electrodes placed over the front of the chest and the back. Select external demand pacing mode at a rate of 70/min, then gradually i the pacing current from zero until capture is shown on the monitor. Clinically, capture results in a palpable peripheral pulse at the paced rate and clinical improvement in the patient’s condition. Provide small doses of IV opioid ± sedation if the patient fi nds external pacing very uncomfortable.
Transvenous cardiac pacing is the treatment of choice for bradycardic patients who are at risk of asystole. The technique should only be performed by an experienced doctor. The preferred route of access is the internal jugular or subclavian vein. However, if thrombolysis has recently been given or is contemplated, or if the patient is taking anticoagulants, use the right femoral vein instead. Obtain a CXR to exclude complications.
A correctly functioning ventricular pacemaker results in a pacing spike followed by a widened and bizarre QRS (Fig. 3.15 ).
Permanent pacemakers and implantable defi brillators Increasingly sophisticated implantable devices are being used to manage arrhythmias. Occasionally, a patient will present to the ED with a malfunctioning pacemaker. Get urgent specialist advice. External trans-cutaneous pacing will provide temporary support whilst the problem is resolved. A special magnet may be needed to inactivate an implantable defi brillator which fi res repeatedly.
Fig. 3.15 Paced rhythm.
83
TREATMENT OF BRADYARRHYTHMIAS
Algorithm for the management of bradycardia (Fig. 3.16 ) See www.resus.org.uk
Seek expert help Arrange transvenous pacing
*Alternatives include:
•Aminophylline
•Dopamine
•Glucagon (if beta-blocker or calcium channel blocker overdose)
•Glycopyrronium bromide can be used instead of atropine
YES NO
Adverse features?
•Shock
•Syncope
•Myocardial ischaemia
•Heart failure
Atropine 500 mcg IV
YES
NO
NO YES
•Assess using the ABCDE approach
•Give oxygen if appropriate and obtain IV access
•Monitor ECG, BP, SpO2, record 12-lead ECG
•Identify and treat reversible causes (e.g. electrolyte abnormalities)
Observe Satisfactory
response?
!
Interim measures:
•Atropine 500 mcg IV repeat to maximum of 3 mg
•Isoprenaline 5 mcg min–1 IV
•Adrenaline 2–10 mcg min–1 IV
•Alternative drugs*
OR
•Transcutaneous pacing
Risk of asystole?
• Recent asystole
• Mobitz II AV block
• Complete heart block with broad QRS
• Ventricular pause >3s
Fig. 3.16 Algorithm for the management of bradycardia.
CHAPTER 3
Medicine
Tachycardia algorithm–with pulse
Yes/Unstable
•Amiodarone 300 mg IV over 10–20 min
and repeat shock; followed by: No/Stable
Narrow Broad Is QRS narrow (< 0.12s)?
Irregular Narrow QRS
Is rhythm regular?
Regular
Irregular Regular
Adverse features?
•Shock
•Syncope
•Myocardial ischaemia
•Heart failure Synchronised DC Shock
Up to 3 attempts
Broad QRS Is rhythm regular?
•Assess using the ABCDE approach
•Give oxygen if appropriate and obtain IV access
•Monitor ECG, BP, SpO2, record 12-lead ECG
•Identify and treat reversible causes (e.g. electrolyte abnormalities)
•Amiodarone 900 mg over 24 h
85
TACHYCARDIA ALGORITHM Irregular narrow complextachycardia Probable atrial fibrillation Control rate with:
•β-Blocker or diltiazem
•Consider digoxin or amiodarone if evidence of heart failure
Possibilities include:
•AF with bundle branch block treat as for narrow complex
•Pre-excited AF consider amiodarone
•Polymorphic VT (e.g. torsade de pointes give magnesium 2 g over 10 min)
If ventricular tachycardia (or uncertain rhythm):
•Amiodarone 300 mg IV over 20–60 min;
then 900 mg over 24 h If previously confirmed SVT with bundle branch block:
•Give adenosine as for regular narrow complex tachycardia
•Use vagal manoeuvres
•Adenosine 6 mg rapid IV bolus;
if unsuccessful give 12 mg;
if unsuccessful give further 12 mg
•Monitor ECG continuously
Probable re-entry paroxysmal SVT:
•Record 12-lead ECG in sinus rhythm
•If recurs, give adenosine again and consider choice of anti-arrhythmic prophylaxis
Yes
Sinus rhythm restored?
No
Possible atrial flutter
•Control rate (e.g. β-Blocker) Seek expert help
Seek expert help
!
!
Fig. 3.17 Tachycardia algorithm with pulse (www.resus.org.uk).
Tachyarrhythmias
The single Resuscitation Council 2010 tachycardia algorithm (Fig. 3.17 ) (see www.resus.org.uk ) is based on the fact that, irrespective of the exact underlying cardiac rhythm, many of the initial management principles in the peri-arrest setting are the same:
• Rapidly assess ABC.
• Monitor cardiac rhythm and record a 12-lead ECG.
• Provide O 2 .
• Identify and treat reversible causes.
• Assess for evidence of instability (signs of shock, syncope, signs of heart failure, or myocardial ischaemia) — these indicate the need for urgent intervention, initially in the form of synchronized cardioversion.
The unstable patient with tachyarrhythmia Synchronized cardioversion
This requires two doctors — one to perform cardioversion, the other (experienced in anaesthesia) to provide sedation/anaesthesia and manage the airway. The patient will not be fasted and is therefore at particular risk of aspiration. The arrhythmia may d cardiac output and i circulation times, so IV drugs take much longer to work than usual. If the ‘sedation doctor’
does not appreciate this and gives additional doses of anaesthetic drugs, hypotension and prolonged anaesthesia may result.
Electrical cardioversion is synchronized to occur with the R wave to minimize the risk of inducing VF. Synchronized cardioversion is effective in treating patients who exhibit evidence of instability with underlying rhythms of SVT, atrial fl utter, atrial fi brillation, and VT — choose an initial level of energy according to the rhythm:
• For broad complex tachycardia or AF, start with 200J monophasic or 120–150J biphasic. If unsuccessful, i in increments to 360J monophasic or 150J biphasic.
• Start with a lower energy for atrial fl utter and paroxysmal SVT — use 100J monophasic or 70–120J biphasic. If this is unsuccessful, increase in increments to 360J monophasic or 150J biphasic.
Amiodarone
If cardioversion is unsuccessful after 3 synchronized shocks, give amio-darone 300mg IV over 10–20min and repeat shock. Give amioamio-darone by central vein when possible as it causes thrombophlebitis when given peripherally. However, in an emergency, it can be given into a large peripheral vein.