TECHNIQUES OF ASSISTED VENOUS RETURN DURING CARDIOPULMONARY BYPASS Retour Toulouse
A.H. STAMMERS, MSA, CCP
Geisinger Medical Center - Danville, Pennsylvania, USA
OBJECTIVES
1. To discuss the benefits of using augmented venous return during
cardiopulmonary bypass.
2. To contrast kinetic versus vacuum assisted venous return.
Augmented Venous Return - The process of applying a force to
assist in the drainage of fluid from a fixed point.
INTRODUCTION
Few improvements in techniques of cardiopulmonary
bypass (CPB) can compete with augmented venous return (AVR) in succeeding in
expanding the practice of extracorporeal circulation. At the same time, however,
concern has arisen about its application since this process has also been linked
to an increased potential of gas embolism. The following report will review the
techniques of AVR and methods of improving its safe conduct.
In an extracorporeal circuit, the movement of fluid becomes fixed and is related
to a number of factors including:
1. cross-sectional area of the lumen of the
cannulae,
2. the volume of fluid in the cannulated vessel or chamber, and 3. the
hydrostatic pressure head
from the source of fluid to the height of the column of fluid in the receiving
vessel. These
factors have influenced the flow dynamics associated with extracorporeal
circulation
and affect the conduct of perfusion. Since, according to the Fick Principle, the
delivery
of nutrients is primarily a function of flow, limitations in venous return can
adversely
affect how perfusion is conducted. Such limitations are not new to perfusion and
early
investigators examined means of augmenting venous return to improve the flow
through
the extracorporeal circuit.
AUGMENTED VENOUS RETURN
Since the hydrostatic pressure in a circuit is limited by physical constraints, and the volumetric state of the patient varies, methods of improving venous return have focused on increasing the cross-sectional area of the venous, or return, cannula. However, the move towards minimally invasive techniques in cardiac surgery has necessitated the reduction in venous cannula size. Therefore, AVR has gained increased popularity as a means of facilitating extracorporeal flow. There are two methods, which have gained popularity over the past several years: Kinetic assisted venous return (KAVR) and vacuum assisted venous return (VAVR).
KINETIC ASSISTED VENOUS RETURN
KAVR is performed by placing a constrained vortex or centrifugal pump in between the venous cannula and the venous reservoir. This has been popularized as a means of performing port access surgery, which has reduced the incision size necessary to perform corrective surgical maneuvers. The centrifugal pump is a preload sensitive pump that utilizes a non-occlusive mechanism for the movement of blood. Its utility in routine CPB has been well established and it is used in over 50% of all surgical procedures utilizing CPB. It is both preload and afterload dependent which provides an increased level of safety for the conduct of perfusion.
REFERENCES
1. Tevaearai HT, Mueller XM, Jegger D, Augsburger M, Stumpe F, von Segesser LK.
Optimization of the pump driven venous return for minimally invasive open heart
surgery. Int J Artif
Organs 1999;22:684-9.
2. Jegger D, Tevaearai HT, Horisberger J, Mueller XM, Boone Y, Pierrel N,
Seigneul I, von Segesser LK.
Augmented venous return for minimally invasive open heart surgery with selective
caval cannulation. Eur
J Cardiothorac Surg 1999;16:312-6.
3. McCusker K, Hoffman D, Maldarelli W, Toplitz S, Sisto D. High-flow
femoro-femoral bypass utilizing
small cannulae and a centrifugal pump on the venous side. Perfusion
1992;7:295-300.
4. Solomon L, Sutter FP, Goldman SM, Mitchell JM, Casey K.
Augmented femoral venous return. Ann Thorac Surg 1993;55:1262-3.
5. Ojito JW, Hannan RL, Miyaji K, White JA, McConaghey TW, Jacobs JP, Burke RP.
Assisted venous
drainage cardiopulmonary bypass in congenital heart surgery. Ann Thorac Surg
2001;71:1267-71.
6. Toomasian JM, Peters WS, Siegel LC, Stevens JH. Extracorporeal circulation
for port-access cardiac
surgery. Perfusion 1997;12:83-91
7. Toomasian JM, McCarthy JP. Total extrathoracic cardiopulmonary support with
kinetic assisted
venous drainage: experience in 50 patients. Perfusion 1998;13:137-43.
VACUUM ASSISTED VENOUS RETURN
VAVR is performed by utilizing a closed system of venous return that employs a sealed reservoir to which a vacuum (negative pressure) is applied. The use of vacuum creates a suction, which aids the normal siphon drainage created by the hydrostatic pressure head from the patient to venous reservoir. The force applied to the fluid increases venous return by enhancing the movement of blood from cannula to reservoir. The amount of vacuum applied generally is between 50 and 80 mmHg of negative pressure.
BENEFITS OF AUGMENTED VENOUS RETURN
The benefits of AVR have been well demonstrated in the literature and include:
improvement in venous return during CPB
reduction in venous cannula size
reduced volume necessary to prime the extracorporeal circuit leading to less
hemodilution
reduced hemodilution during CPB with lowered dependency on crystalloid and
colloidal solutions
reduced dependency of autogeneic blood products, especially in pediatric
patients
decreased size of incisions necessary for surgical repair
improved markers of hemostatic function on the first postoperative day
reduced cluttering of the operative filed due to decreased cannula size
improved ventricular decompression.
REFERENCES
1. Tevaearai HT, Mueller XM, Jegger D, Ruchat P, von Segesser LK. Venous
drainage with a single
peripheral bicaval cannula for less invasive atrial septal defect repair. Ann
Thorac Surg 2001;72:1772-3.
2. Nakanishi K, Shichijo T, Shinkawa Y, Takeuchi S, Nakai M, Kato G, Oba O.
Usefulness of vacuumassisted
cardiopulmonary bypass circuit for pediatric open-heart surgery in reducing
homologous blood
transfusion. Eur J Cardiothorac Surg 2001;20:233-8.
3. Munster K, Andersen U, Mikkelsen J, Pettersson G. Vacuum assisted venous
drainage (VAVD).
Perfusion 1999;14:419-23.
4. Kitamura M, Uwabe K, Hirota J, Kawai A, Endo M, Koyanagi H. Minimally
invasive cardiac surgery
in the adult: surgical instruments, equipment, and techniques. Artif Organs
1998;22:765-8.
5. Berryessa R, Wiencek R, Jacobson J, Hollingshead D, Farmer K, Cahill G.
Vacuum-assisted venous
return in pediatric cardiopulmonary bypass. Perfusion 2000;15:63-7.
6. Berthod J, Tevaearai HT, Mueller XM, Mabillard E, Von Segesser LK, Stumpe F.
Closure of an atrial
septal defect by a mini-thoracotomy with the help of extra-corporal circulation.
Rev Med Suisse Romande
2000;120:569-72.
7. Tevaearai HT, Mueller XM, Jegger D, Augsburger M, Stumpe F, von Segesser LK.
Optimization of the pump driven venous return for minimally invasive open heart
surgery. Int J Artif
Organs 1999;22:684-9.
8. Darling E, Kaemmer D, Lawson S, Smigla G, Collins K, Shearer I, Jaggers J.
Experimental use of an ultra-low prime neonatal cardiopulmonary bypass circuit
utilizing vacuumassisted
venous drainage. J Extra Corp Tech 1998;30:184-9.
9. Bevilacqua S, Matteucci S, Ferrarini M, Kacila M, Ripoli A, Baroni A,
Mercogliano D, Glauber M,
Ferrazzi P. Biochemical evaluation of vacuum-assisted venous drainage: a
randomized, prospective study.
Perfusion 2002;17:57-61.
10. Shin H, Yozu R, Maehara T, Matayoshi T, Morita M, Kawai Y, Yamada T, Kawada
S. Vacuum
assisted cardiopulmonary bypass in minimally invasive cardiac surgery: its
feasibility and effects on
hemolysis. Artif Organs 2000;24:450-3.
11. Hayashi Y, Kagisaki K, Yamaguchi T, Sakaguchi T, Naka Y, Sawa Y, Ohtake S,
Matsuda H. Clinical
application of vacuum-assisted cardiopulmonary bypass with a pressure relief
valve. Eur J Cardiothorac
Surg 2001;20:621-6.
CONCLUSION
Techniques of augmented venous return have facilitated the conduct of minimally invasive surgery where extracorporeal circulation is required. When properly applied this methodology safely expands mechanisms of perfusion in promoting patient care.