OSCE 6


This 67-year-old male was admitted to the Intensive Care Unit 6 hours ago following emergency coronary artery bypass grafting.  He has remained hypotensive (mean arterial pressure of 60 mmHg) and oliguric, despite adequate fluid loading to a right atrial pressure of 15 mmHg and an adrenaline infusion at 20 mg/min. A recent transoesophageal echocardiogram demonstrates global severe systolic dysfunction and no evidence of pericardial tamponade.
You have been asked to consider inserting an intra-aortic balloon pump by the attending team.
Consider your approach and preparation for this procedure.

What do you think of the suggestion for inserting a balloon pump in this patient?

Procedure station:   Candidates were expected to provide a systematic approach to the principle of insertion, management and removal of an Intra-Aortic Balloon Pump catheter. Nineteen out of twenty-eight candidates passed this section.

Indications for IABP insertion:

No choice but pump

  • Failure to come off bypass
  • Severe aortic stenosis, mitral regurgitation or ventricular septal defect
    with haemodynamic compromise, while waiting for repair

Probably harmless, but probably not useful

  • High risk CABG patients (pre-op)
  • High-risk PCI patients (pre-op)
  • Cardiogenic shock while waiting for PCI
  • Pulmonary oedema in spite of maximal medical management

Totally experimental

  • Takotsubo cardiomyopathy
  • Neurogenic stress cardiomyopathy of subarachnoid haemorrhage
What is the evidence for the use of IABP?
Describe the major features of this device.

IABP

(Ideally, you'd have an IABP as a prop to hand to the candidate, so they can fiddle with it physically. The picture of my own expired IABP is included here for convenience).

This is an intra-aortic balloon pump catheter.

Its major features are:

  • 40ml polyurethane balloon
  • Inner tube for insertion (the "blood lumen")
  • Outer tube for helium (the "helium lumen")
  • A flexible plastic hub to secure the device to the skin with four sutures
  • A flexible plastic sheath 
  • A hub connector to attach the device to the helium tank
What are the safety features of this device?
  • Tear-resistant helium balloon
  • Inert biocompatible plastic 
  • Radio-opaque markers on either side of the balloon, to assist positioning
  • Kink-resistant thin inner tube
  • Reinforced extracorporial tubing
  • Luer-lock connectors to prevent helium leak
  • Flexible plastic hubs allow the device to be secured at six independent pointas on the skin
  • A mark on the gas tube indicates when all of the balloon has come out of the introducer sheath
  • Volume of the inner tube is clearly documented on the distal hub
How do you size this device? How do you select the appropriate sized balloon?

Generally speaking, the IABPs are sized according to height.

  •  Under 152cm = 25ml balloon
  • 152-162cm = 34ml balloon
  • 162-183cm = 40ml balloon
How would you insert this device?

By Seldinger technique, of course. There is a sheathed and unsheathed version of this procedure

  • Prep/drape etc
  • Introduce an 18g angiography needle into the common femoral artery
  • Introduce the supplied J-tipped 0.6mm wire into the needle
  • Keep the wire and discard the needle
  • Make a small skin incision
  • Dilate the vessel with the supplied sheathed 15cm introducer dilator
  • Remove the dilator, keeing the introducer and guide wire in situ
  • Slide the balloon catheter over the guidewire
  • Advance it to its proper position
  • Remove the guidewire
  • Flush the inner lumen with saline
  • Connect the gas lumen to the pump and start the device
What is the correct position? How would you confirm that it is in the right position?
  • Correct position is 2cm distal to the origin of the left subclavian artery
  • The distal balloon marker has to be above the origins of the renal arteries

Two main ways of checking the position:

  • By measuring: from the level of the 2nd intercostal space in midline, to the umbilicus, to the insertion site in the groin
  • By CXR: IABP position should be just below the level of the aortic knuckle
  • By TOE
  • By fluoroscopy
 What are the contraindications for IABP insertion?

Absolute contraindications

  • Aortic regurgitation
  • Aortic aneurysm
  • Aortic dissection
  • Severe sepsis
  • Uncontrolled coagulopathy

Relative contraindications

  • Atherosclerosis and arterial tortuosity
  • Left ventricular outflow tract obstruction
  • Contraindications to anticoagulation
Do you need to anticoagulate the patient? If so, then how would you do it?
  • Heparin is an appropriate choice
  • A pump on 1:1 may not require any anticoagulation, but this is controversial
  • A retrospective audit of about 18,000 patients Chin et al (2010):
  • anticoagulation in fact did not increase the risk of bleeding complications,
    but the absence of anticoagulation did increase the risk of thrombotic complications. The anticoagulated group also had reduced mortality.
  • In summary (own practice) - any well-reasoned answer is appropriate
What are the complications of IABP insertion?

Common complications

  • Mild limb ischaemia - 2.9%
  • Balloon leak - 1.0%
  • Major limb ischaemia - 0.9%
  • Haemorrhage - 0.8%
  • Leg amputation due to ischaemia - 0.1%

Rare complications

  • Atheromatous cholesterol emboli
  • Aortic or arterial dissection
  • Cerebrovascular accident
  • Thrombocytopenia
  • Haemolysis
  • Helium embolism
What are the different methods of triggering the counterpulsation?
  • ECG
    • Inflation of the balloon is triggered by the the beginning of diastole, which correlates with the middle of the T-wave.
    • The balloon is timed to deflate at the very end of diastole. This correlates with the R-wave
  • Pressure
  • Pacing spikes
  • Asynchronous mode (for patients who are asystolic)
The patient undergoes a safe insertion of the IABP, and 1:1 counterpulsation is commenced.  How will you determine that augmentation is effective?

IABP waveform

  • Turn the pump to 1:2 
  • The assisted end-diastolic pressure should be lower than the assisted
  • The assisted systolic pressure should be lower than the unassisted systolic
  • The balloon inflation should occur at the same time as the aortic valve closes (i.e. at the dicrotic notch
You are called to interpret this waveform while the IBP has been put into 1:2 augmentation mode.
What do you make of the augmentation? Is there a problem here? Explain your answer

There is early balloon inflation and early balloon deflation.

  • The assisted systolic pressure is no different to the unassisted
  • The assisted diastolic pressure returns to its unassisted level before the next systeole
What are the consequences of this for the effectiveness of the aortic counterpulsation?

Early balloon inflation results in

  • Increased LV oxygen demand, due to increased afterload
  • Decreased LV oxygen supply, due to decreased diastolic perfusion
  • Decreased cardiac output, due to decreased stroke volume

Early balloon deflation results in

  • Unimproved left ventricular afterload
  • Thus no decrease in LV oxygen demand
Over days, the cardiac output improves gradually. How would you wean the patient off the IABP?

Two main schools of thought:

  • gradually decrease balloon volume
  • trial 1:2 augmentation, and if well tolerated - remove

Disclaimer: the viva stem above may be an original CICM stem, acquired from their publicly available past papers. Or, perhaps it is a slightly altered version of the original CICM stem. Or, it is a completely original viva stem, concocted by the monstrously amoral author of Deranged Physiology for nothing more than his own personal amusement. In either case, because the college do not make the main viva text or marking criteria available, almost everything here has been confabulated. It might sound like a plausible viva and it could be used for the purpose of practice, but all should be aware that it does not represent the "true" canonical CICM viva station. 

References

Insertion of the IABP: a manual by MAQUET

Ranucci, Marco, et al. "A Randomized Controlled Trial of Preoperative Intra-Aortic Balloon Pump in Coronary Patients With Poor Left Ventricular Function Undergoing Coronary Artery Bypass Surgery." Critical care medicine (2013). 2013 Nov;41(11):2476-83.

Theologou, Thomas, et al. "Preoperative intra aortic balloon pumps in patients undergoing coronary artery bypass grafting." Cochrane Database Syst Rev 1 (2011).

Ohman, E. Magnus, et al. "Use of aortic counterpulsation to improve sustained coronary artery patency during acute myocardial infarction. Results of a randomized trial. The Randomized IABP Study Group." Circulation 90.2 (1994): 792-799.

Moulopoulos, Spyridon D., Stephen Topaz, and Willem J. Kolff. "Diastolic balloon pumping (with carbon dioxide) in the aorta—a mechanical assistance to the failing circulation." American heart journal 63.5 (1962): 669-675.

SOROFF, HARRY S., et al. "Assisted circulation II. Effects of counterpulsation on left ventricular oxygen consumption and hemodynamics." Circulation 27.4 (1963): 722-731.

Chen-yang, Jiang, et al. "Anticoagulation therapy in intra-aortic balloon counterpulsation: Does IABP really need anti-coagulation?." Journal of Zhejiang University SCIENCE A 4.5 (2003): 607-611.

Cooper, Howard A., Elissa Thompson, and Julio A. Panza. "The role of heparin anticoagulation during intra-aortic balloon counterpulsation in the coronary care unit." Acute Cardiac Care 10.4 (2008): 214-220.

Chin, Chee Tang, et al. "The impact of anticoagulation during intra-aortic balloon counterpulsation pump placement on in-hospital outcomes in 18,875 patients undergoing cardiac revascularization." Circulation. Vol. 122. No. 21. 530 WALNUT ST, PHILADELPHIA, PA 19106-3621 USA: LIPPINCOTT WILLIAMS & WILKINS, 2010.

Yutani, Chikao, et al. "CEREBRO‐SPINAL INFARCTION CAUSED BY ATHEROMATOUS EMBOLI." Pathology International 35.4 (1985): 789-801.

Ho, A. C., et al. "Stroke after intraaortic balloon counterpulsation associated with mobile atheroma in thoracic aorta diagnosed using transesophageal echocardiography." Chang Gung medical journal 25.9 (2002): 612-616.

Kvilekval, Kara HV, et al. "Complications of percutaneous intra-aortic balloon pump use in patients with peripheral vascular disease." Archives of Surgery 126.5 (1991): 621.

Rius, Jordi Bañeras, et al. "Resolution of Shock-Induced Aortic Regurgitation With an Intraaortic Balloon Pump." Circulation 124.4 (2011): e131-e131.

Ferguson, James J., et al. "The current practice of intra-aortic balloon counterpulsation: results from the Benchmark Registry." Journal of the American College of Cardiology 38.5 (2001): 1456-1462.

Alderman, James D., et al. "Incidence and management of limb ischemia with percutaneous wire-guided intraaortic balloon catheters." Journal of the American college of Cardiology 9.3 (1987): 524-530.

Pennington, D. Glenn, et al. "Intraaortic balloon pumping in cardiac surgical patients: a nine-year experience." The Annals of thoracic surgery 36.2 (1983): 125-131.

Cruz-Flores, Salvador, Alan L. Diamond, and Enrique C. Leira. "Cerebral air embolism secondary to intra-aortic balloon pump rupture." Neurocritical Care 2.1 (2005): 49-50.

HIROOKA, KAZUNOBU, et al. "Helium Gas Embolism caused by a Ruptured Intraaortic Balloon." Japanese Journal of Intensive Care Medicine 27.9 (2003): 867-871.

Mitchell, Simon J., et al. "Cerebral arterial gas embolism by helium: an unusual case successfully treated with hyperbaric oxygen and lidocaine." Annals of emergency medicine 35.3 (2000): 300-303.

Chockalingam, Anand, et al. "Dynamic left ventricular outflow tract obstruction in acute myocardial infarction with shock cause, effect, and coincidence." Circulation116.5 (2007): e110-e113.

Bavin, Terry K., and Marjorie A. Self. "Weaning from intra-aortic balloon pump support." AJN The American Journal of Nursing 91.10 (1991): 54-59.