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Ann Thorac Surg 2006;82:1952-1953
© 2006 The Society of Thoracic Surgeons

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Correspondence

Preventing the Loss of Safety Margins With Miniaturized Cardiopulmonary Bypass

London Perfusion Science and Department of Cardiac Surgery, Cardiac Theatres 3 and 4, 2nd Floor, A Block, Hammersmith Hospital, Du Cane Rd, London, W12 0NN United Kingdom

(Email: john{at}londonperfusionscience.com).

To the Editor:

We read with interest the article written by Nollert and colleagues [1] regarding their experience with miniaturized cardiopulmonary bypass (MCPB). The Hammersmith Hospital in London has been interested in MCPB since its inception, but has proceeded with caution for all the reasons outlined in Nollert and colleagues' [1] article. By January 2005, we felt our reservations concerning management and safety had been addressed. Since then, over 100 nonselected coronary artery bypass operations have been performed using the Extra Corporeal Circulation Optimised MCPB system (Sorin Group Italia, Mirandola, Italy) and we feel we are able to address some of the points the article raised.

(1) Removal of venous air: Effective removal of venous air pre-oxygenator is essential. The system we use is shown in Fig 1. Venous air (including micro-air and air introduced from the cardiopulmonary bypass [CPB] sample port) is detected using a bubble detector. This triggers a roller pump that draws the air off the top of a "side entry" 170µ filter.
The pump is set at 300 mL/minutes and runs for 5 seconds post-detection. In our experience with this system, the device has coped with air in a number of situations including emergency return to bypass. We have found that the removal window for major venous air can be prolonged by reducing the arterial flow and thereby increasing the time air spends in the venous filter. We intend to incorporate this device into our conventional circuit.

(2) Venting: The venting system removes blood from the heart to a soft shell reservoir (SSR) that runs in parallel to the systemic circulation. Tubing clamps isolate the SSR from the systemic circulation except during volume management. The vent can be left on continuously and the volume returned to the systemic system with the removal of one clamp. The surgeons feel this system provides better venting than conventional bypass, because the perfusionist meticulously controls the vent to avoid the entrainment of air due to negative pressure.

(3) Volume management: There is no doubt that volume management during MCPB involves a learning curve for the perfusionist and good communication with the rest of the cardiac team. The system we use accelerates this learning process for the following reasons:

• The SSR allows rapid and safe options for adding/removing volume from the systemic circulation.

• The SSR facilitates simple, rapid return of vented blood to the systemic circulation.

• If required, a low-pressure sucker is available to transport "pools of blood" (air free if possible) from the chest cavity to the SSR and subsequently the systemic circulation. This provides a faster alternative to the cell saver when volume is required urgently.

View larger version (66K): [in this window] [in a new window]   Fig 1. Schematic of venous air removal system.

Coagulation and use of blood products: In contrast to Nollert and colleagues [1], we have found that our current MCPB patient transfusion rate (see figures from our hospitals standard 6 monthly blood product usage audit) is 0.7 units per patient compared with the 1.4 units per person reported with their system. This is 56% lower than our conventional CPB transfusion rate.

In conclusion, our experience at the Hammersmith demonstrates that setting up a MCPB program requires good teamwork, good communication, and a willingness to adapt. The whole process can be simplified by learning from other hospitals' experiences and by selecting the MCPB system that best suits the safety and CPB management protocols of the individual hospital.

	References

Top References

 

1. Nollert G, Schwabenland I, Maktav D, et al. Miniaturized cardiopulmonary bypass in coronary artery bypass surgery: marginal impact on inflammation and coagulation but loss of safety margins Ann Thorac Surg 2005;80:2326-2332.[Abstract/Free Full Text]

This article has been cited by other articles:

				I Dimarakis, D Stefanou, G Yarham, J Mulholland, and J Anderson Total miniaturized cardiopulmonary bypass: the next step in minimally invasive aortic valve replacement Perfusion, September 1, 2008; 23(5): 275 - 278. [Abstract] [PDF]

				R. W. Issitt, J. W. Mulholland, M. D. Oliver, G. J. Yarham, P. J. Borra, P. Morrison, I. Dimarakis, and J. R. Anderson Aortic Surgery Using Total Miniaturized Cardiopulmonary Bypass Ann. Thorac. Surg., August 1, 2008; 86(2): 627 - 631. [Abstract] [Full Text] [PDF]

				J.W. Mulholland, J.R. Anderson, G.J. Yarham, S. Tuladhur, I. Saed, and M.D. Oliver Miniature cardiopulmonary bypass the Hammersmith experience Perfusion, May 1, 2007; 22(3): 161 - 166. [Abstract] [PDF]

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