Background

This is designed as a quick guide to the management of this common ITU condition. Click here for the original NICE guidance for AF

New Onset AF (NOAF)

• Usually prequelled with some previous risk factors:
  • Age
  • Poor LV function
  • LA dilatation
  • Thyroid disease
  • Alcohol consumption
  • Hypertension

Atrial fibrillation with fast ventricular rate

• Cardiac
  • Acute LVF
  • ACS
  • Cardiomyopathy
• Non-cardiac
  • Increase in sympathetic drive
  • Increased conductivity of the AV node leading to fast irregular atrial activity. Causes include:
    • Sepsis
    • Head injury
    • PE
    • Acute respiratory failure
    • Metabolic derangement
    • Thyroid disease
    • TIA/CVA
    • Major haemorrhage

Aims of Treatment in ITU

• Rate limit or Cardiovert
• Adequately assess risk of acute stroke
• Decide regarding acute anticoagulation
  • Many critical care patients have potential absolute or relative contra-indications to anticoagulation, such as being post-operative, needing invasive lines or having DIC which should be taken into consideration.

1. Pharmacological Rate Control

• First line therapy (according to NICE) and is the more common method of acute AF control.
  • Reduces stroke risk
  • Often the ongoing longer term management for these patients’ AF
  • Many patients will ‘self cardiovert’ back to sinus rhythm in the background, as the sympathetic process, coupled with AVN transmission inhibition occurs due to rate limitation.
  • The aim is to reduce the heart rate to less than 120  in an attempt to prevent cardiac decompensation and associated sequalae such as Type 2 MI.

Options

Beta Blockade

• Esmolol
  • IV 25-200mcg/kg/min – trial only
  • If rate reduction is achieved with CVS stability then a longer acting BB can be used
  • If BP drops then another class of agent should be tried
• Metoprolol
  • IV bolus, up to 5mg (at 1-2mg/min)
  • Repeated up to 15mg
• Bisoprolol
  • PO/NG 1.25-10mg OD

Digoxin

• Can rate limit or cardiovert
  • Loading dose 500mcg at 6 hour intervals
  • Maximum 1.5mg in 24hours
  • Maintenance with 125-250mcg OD

Amiodarone

• Can act to both rate limit or primarily cardiovert
  • IV 300mg over 1 hour through central line or good sized peripheral cannula, ideally ACF
  • Followed by 900mg over 23 hours via a central line only due to the risk of vessel damage
  • Occasionally, the initial infusion is enough to treat the issue

Rate limiting Ca2+ channel blockade

• Diltiazem
  • PO/NG 60mg TDS
  • Increased to maximum of 360mg OD
• Verapamil
  • PO 40-120mg TDS
  • IV slow injection 5-10mg

2. Electrical Cardioversion

• Reserved as first line for haemodynamically compromised patients
  • Cardiac ischaemia
  • Persistently low BP despite fluid management
• It can also be used in younger patients deemed low stroke risk where the AF is NOAF (i.e. less than 48 hours)
• It can also be used in those where rate-controlled strategies have not been successful

Housekeeping

• Explain to patient and consent if appropriate about procedure
• Assemble team
• Ensure airway competent person is present
• Assess for aspiration risk, if high then intubation should be considered
• Apply cardioversion pads from defibrillator to patients’ chest appropriate positions
• Ensure good IV access and if required, sedate the patient with 1-5mg of Midazolam or low dose Propofol
• Using a manual defib, ‘sync’ the defibrillator to apply a synchronised shock. How much energy is a controversial arena! Here is a nice discussion for you, where different energy levels for shocking AF are discussed. It also depends whether you are using mono or biphasic machines.
  • first shock 200J
  • second 300J
  • third 360J
• Try to record the change in rhythm on the defib printer if possible

3. Chemical Cardioversion

• Amiodarone IV – (See doses above)
• Flecainide
  • IV 2mg/kg over 10-30 minutes (max 150mg)
  • Followed by infusion of 1.5mg/kg/hour for 1 hour, then 100-250mcg/kg/hour for upto 24 hours
  • DO NOT offer Flecainide to patients with evidence of structural heart disease

4. Electrolyte Correction

• K+ >4.5
• Magnesium >1

5. Anticoagulation

Most people with AF pre-admission to ITU should have already been risk assessed by either there GP or specialist.

• Acute anticoagulation is considered for those with a significant stroke risk
  • LV thrombus
  • Previous stroke
  • Those with concurrent advantages of anti-coagulation e.g. PE, MI
• Not needed in those with:
  • CHA2DS2VASC of 0 for men or 1 for women
  • <48hrs NOAF
• Needed if:
  • Stable sinus rhythm is not successfully restored within the same 48-hour period following onset of atrial fibrillation and have an appropriate CHADS 2 AF / Stroke risk score
  • Risk factors indicating a high risk of atrial fibrillation recurrence

Long term

• Anticoagulation risk should be assessed in all AF patients
• Current NICE guidelines (2014) suggest it should be considered in all patients with:
  • Symptomatic or asymptomatic paroxysmal AF
  • Persistent or permanent atrial fibrillation or those with a continuing risk of arrhythmia recurrence after cardioversion back to sinus rhythm.
• The CHA2DS2VASC and HASBLED scoring systems are good for assessing stroke and bleeding risks respectively.
• HASBLED takes into account:
  • Uncontrolled hypertension
  • Significant renal and liver disease
  • Bleeding risk (such as relevant medications and labile INRs)
  • Alcohol consumption
• On discharge from ITU/HDU, obtain appropriate follow up whilst an inpatient for ongoing management and stroke risk.

Drug Choices

Acute treatment dose

• Low Molecular Weight Heparin
  • Clexane 1.5mg/kg or Dalteparin

Long-term treatment dose

• Warfarin
• NOAC
  • Apixaban, Dabigatran, Rivaroxaban
  • Usually used in older patients 65-75, those with prior CVA or TIA, Hypertension, Diabetes or Symptomatic heart failure
  • Do not offer Anti-platelets