HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Takao Watanabe Yasuhisa Shimazaki Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Watanabe, T. Articles by Shimazaki, Y. Search for Related Content PubMed Articles by Watanabe, T. Articles by Shimazaki, Y.

J Thorac Cardiovasc Surg 1996;111:490-492
© 1996 Mosby, Inc.

Letters to the Editor

What is cerebral metabolism during retrograde perfusion?

Second Department of Surgery
Yamagata University School of Medicine
Iida-Nishi, 990-23
Yamagata, Japan^a

To the Editor:

We appreciate the experimental research on the pharmacologic improvement of retrograde cerebral perfusion by Yoshimura and associates. ¹ Brain edema, a topic of investigation because of the broad use of this type of perfusion, was noted in the article to be alleviated by addition of mannitol and an antivasospastic agent, with the reduction of cerebral vascular resistance. The data shown encourage clinical trials of pharmacologic support to reduce the morbidity after aortic arch procedures.

The perfusion method of Yoshimura and associates, ¹ however, is extremely different from clinical or other experimental retrograde brain (cerebral) perfusion methods. Yoshimura and associates ¹ perfused the dogs through the bilateral maxillary veins while draining blood from the right atrium instead of the aorta. It is not clear why they performed this curious veno-venous bypass perfusion as "retrograde cerebral perfusion."

Fig. 1 demonstrates how small the brain is compared with the total area perfused through bilateral maxillary veins. This well-developed venous network would steal the perfused blood from the brain. This shunt flow can be reduced when the pressures in the azygos vein and the superior vena cava are maintained high, as in our previous study. ² Contrarily, drainage from the right atrium should magnify this shunt flow from the brain through the superior vena cava, azygos vein, and other veins. Then the intracranial sinuses should collapse, even if the maxillary vein pressure is maintained as shown in Yoshimura and associates' article. ¹ Their veno-venous bypass perfusion therefore never establishes effective retrograde circulation in the brain. The low and decreasing intracranial pressures shown in the article are evidence of a perfusion failure because the intracranial pressure is known to increase as the perfusion pressure increases during retrograde brain perfusion. ³ Apparently, the brain edema shown in the article is caused by absence of circulation in the brain tissue but not by excess blood flow into the intracranial sinuses.

View larger version (111K): [in this window] [in a new window]   Fig. 1. An angiogram through bilateral internal maxillary veins demonstrates intracranial sinuses and extracranial veins as a dense network. The head and neck veins permit the blood to escape from the brain to the body.

In addition, as Fig. 1 demonstrates, the CBF cannot be isolated when the brain is perfused retrogradely but not antegradely. ⁸ The brain weight was only 0.67% ± 0.09% of the body weight in 31 dogs used in our previous study. ⁶ Granted that the CBF value shown by Yoshimura and associates ¹ was true, the total blood flow in the brain was less than 11 ml/min. It is estimated as 5% of total perfusion flow rate in this experiment. As Fig. 1 and the anatomy of cranial vessels in the dog show, a large amount of the blood should flow into the carotid artery from the skull and from the extracranial part, but surprisingly small amount should flow from the brain. Data in their experiment therefore did not reflect the metabolic rate of the brain at all.

We believe that the brain protection during retrograde brain perfusion should be physiologically examined as follows: (1) Effective retrograde circulation should be established in the brain experimentally beyond the venous valves with blockage of the flow escaping through the well-developed veno-venous shunt pathways. For this purpose, the superior vena cava and the upper part of azygos vein should be simultaneously perfused or at least ligated, and the blood must be drained from the aorta but never from the right atrium nor from the superior vena cava. Pressure should be simultaneously monitored in the superior vena cava, the sagittal sinus, and the aorta to clarify the true driving pressure. Then the true functional blood flow through the brain capillary bed and the CMRO₂ should be examined during retrograde brain perfusion by some precise measurements. Sophisticated knowledge of this fundamental physiology will clarify the optimal condition for retrograde brain perfusion to protect the brain and reduce or eliminate brain edema. Thereafter, pharmacologic interventions should be tested, with correct baseline estimation of the brain protection by the retrograde brain perfusion itself.

References

1. Yoshimura N, Okada M, Ota T, Nohara H. Pharmacologic intervention for ischemic brain edema after retrograde cerebral perfusion. J THORAC CARDIOVASC SURG 1995;109:1173-81.
   
2. Watanabe T, Iijima Y, Abe K, et al. Retrograde brain perfusion beyond the venous valves. Hemodynamics and intracellular pH mapping. J THORAC CARDIOVASC SURG 1995;109:1173-81.
   
3. Usui A, Oohala K, Liu T, et al. Determination of optimum retrograde cerebral perfusion condition. J THORAC CARDIOVASC SURG 1994;107;300-8.
   
4. Fox LS, Blackstone EH, Kirklin JW, Bishop SP, Bergdahl LA, Bradley EL. Relationship of brain blood flow and oxygen consumption to perfusion flow rate during profoundly hypothermic cardiopulmonary bypass. J THORAC CARDIOVASC SURG 1984;87:658-64.[Abstract]
   
5. Miyamoto K, Kawashima Y, Matsuda H, Okuda A, Maeda S, Hirose H. Optimal perfusion flow rate for the brain during deep hypothermic cardiopulmonary bypass at 20º C. J THORAC CARDIOVASC SURG1986;92:1065-70.
   
6. Watanabe T, Washio M. Pulsatile low-flow perfusion for enhanced cerebral protection. Ann Thorac Surg 1993;56:1478-81.[Abstract]
   
7. Usui A, Hotta T, Hiroura M, et al. Retrograde cerebral perfusion through a superior vena caval cannula protects the brain. Ann Thorac Surg 1992;53:47-53.[Abstract]
   
8. Michenfelder JD, Messick JM Jr, Theye RA. Simultaneous cerebral blood flow measured by direct and indirect methods. J Surg Res 1968;8:475-81.[Medline]
   

This article has been cited by other articles:

				N. Oshikiri, T Watanabe, H Saitou, Y Iijima, T Minowa, K Inui, and Y Shimazaki Retrograde cerebral perfusion: experimental approach to brain oedema Perfusion, July 1, 1999; 14(4): 257 - 262. [PDF]

This Article Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Takao Watanabe Yasuhisa Shimazaki Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Watanabe, T. Articles by Shimazaki, Y. Search for Related Content PubMed Articles by Watanabe, T. Articles by Shimazaki, Y.