The Intra-Aortic Balloon Pump

Dr Stephen Shepherd, Consultant Cardiothoracic Anaesthetist at St Bart’s Hospital, and Operations Manager for London’s ACCESS Transfer Service, talks us through transfers with mechanically augmented cardiac support…

Intra-aortic balloon pumps (IABPs) are commonly used devices with a role in the management of cardiogenic shock, refractory angina, and structural cardiac disease such as severe mitral regurgitation/ventricular septal defect. They can also be used as a bridge to more definitive interventions such as coronary artery bypass grafting or heart transplantation.

Components

• 7-8 Fr sheath (usually in the femoral artery)
• 25-50ml aortic balloon
• Sterile sleeve connecting to console
• Pressure transducer or fibreoptic sensor
• ECG leads from the patient
• Controller unit
• Helium or CO₂ tank

Mechanism Of Action

• The balloon is placed in the descending thoracic aorta, distal to the left subclavian artery and above the mesenteric vessels.

The balloon inflates during diastole, augmenting coronary blood flow and displacing blood towards the rest of the body to improve distal perfusion.

It then deflates during systole, creating a suction effect to vent (empty) the left ventricle, reducing filling pressures and hopefully improving myocardial performance by shifting the ventricle down the Starling curve.

• Balloon pumps should inflate after the dicrotic notch and can be triggered from the ECG at the midpoint of the T wave or the arterial pressure waveform measured from the balloon tip.

Monitoring

• Continuous monitoring of haemodynamic parameters such as arterial pressure, cardiac output, and urine output is essential for assessing the effectiveness of IABP support.
• The timing of balloon inflation and deflation is often adjusted based on these parameters to optimise cardiac output and tissue perfusion.
• Anticoagulation, such as intravenous heparin, is required to prevent thrombosis; monitoring this is therefore necessary.

Complications & Adverse Effects

• While IABPs can provide hemodynamic support, they are associated with several potential complications including haemorrhage, vascular injury, limb ischaemia, thrombosis, and balloon malfunction.
• Balloon pumps are contraindicated with significant aortic regurgitation or in the presence of an aortic dissection.

Weaning & Removal

• IABPs are typically considered for removal once the underlying condition improves, and the patient’s haemodynamic status stabilises.
• Weaning protocols involving gradual reduction in balloon augmentation and monitoring markers of perfusion.
• Where patients cannot be weaned, they may require transfer to another centre for definitive therapy, conversion to a semi-durable or durable device or transplant.

One of the St Bart’s perfusionists, Pete, with a balloon pump set in front of a cardiopulmonary bypass machine.

Transferring On IABPs

• Effective communication between the transferring and receiving healthcare teams is paramount to ensure continuity of care. Detailed information regarding the patient’s clinical status, IABP settings, and any ongoing interventions or concerns should be communicated clearly.

IABP moves are likely to be mid to long-range and may be done by air or by road.

In general, a senior nurse and two clinicians are required: one to manage the patient and one to manage the pump; the second clinician may be a doctor, perfusionist or cardiac physiologist.

Most patients will be very very sick, on inotropes, and possibly ventilated for shock or pulmonary oedema.

There are some general questions to ask when moving an IABP:

o What type of IABP is it?

o When did it go in and why?

o Where is the insertion site?

o How does that look?

o What size catheter is it?

o What are the settings?

 - Amount of augmentation
 - Ratio
 - Response

o What are the assisted and unassisted pressures?

o What other support are they receiving? Expect there to be some!

Packaging

• Perform a full A to E assessment.
• The IABP needs a clean ECG signal – clear dressings or additional tape are recommended to secure the separate ECG cables into the pump.
• Assess insertion site and distal pulses on Doppler if necessary – document these.
• Check correct position pre-departure:

   - 2cm distal to left subclavian artery.
   - Tip should be at level of second intercostal space on CXR.
   - Bottom should be ABOVE the renal arteries at L1.
  

• Patients should lie as flat as possible and no more than 30 degrees upright due to the risk of rupture.
• Perform three-point fixation of IABP and consider leg restraint.
• Secure ECG leads and gas drive line together to reduce snag risk.

Pre-departure Checklist

1. Ensure IABP battery fully charged and connect to mains power whenever possible (literature will say up to 3 hours – in practice this varies with dependency and ratio). Ambulance inverters can accommodate most pump power requirements.
2. Check helium tank level and refill if needed – look at the monitor and consider a refill if < 200 PSI.
3. Take a 60ml-syringe and three-way stopcock for rapid manual deflation in event of console failure, due to risk of thrombosis.

Loading

• In ambulance:

o Transfer headfirst, with pump following, holding connections at all times.

o Consider effect of altitude – helium will expand, and most modern pumps will automatically fill the balloon with less helium as atmospheric pressure falls.

o Consider access to other infusions.

o Secure the device:

 - Lock the wheels.
 - Tethers to secure pump where available.

• En route:

o Pre-alert the receiving hospital.

o Monitor for pump dysfunction:

 - IABP failure.
 - Disconnection.
 - Rapid gas loss (suggesting rupture).
 - Blood in drive line (suggesting rupture).
 - Catheter misplacement.
 - Low helium needing refill.
 - Augmentation below set limit due to worsening intrinsic cardiac function.
 - If arrhythmia, switch to pressure mode – most modern pumps have an
 automatic setting and will use ECG or pressure depending upon which is the
 best signal.

…And you do your best, And they still arrest:

• Consider destination and diversion to place of safety.
• Standard ALS.
• Consider bleeding or displacement whilst inflated in your differentials (monitor will have failed with the latter).
• Can safely defibrillate with IABP running.