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Ann Thorac Surg 2001;72:979
© 2001 The Society of Thoracic Surgeons

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Correspondence

Fluorescein retinal angiography as a useful method of observing cerebral perfusion during aortic arch surgery: Reply

^a Extracorporeal Circulation Department, Beijing Heart, Lung and Blood Vessel Medical Institution, Beijing Anzhen Hospital, PO Box 100029, Beijing, People's Republic of China

To the Editor

We are very pleased to discuss the letter by Dr Takayuki Ono. First, we congratulate him for the use of fluorescein retinal angiography for clinical patients. We agree that this is a useful method to directly observe cerebral perfusion. Moreover, we believe that it may be used not only for arch surgery but also for patients undergoing cardiopulmonary bypass.

Doctor Ono mentioned different fluorescein appearance times in his letter. In our animal study, we kept the perfusion pressure at 25 mm Hg by adjusting the flow rate, which was higher than we use in the clinic. There are some differences between individual patients in clinical practice. Usui and colleagues [1] and Nojima and colleagues [2] have shown that a pressure between 20 and 25 mm Hg measured in the jugular vein provides optimal benefit during retrograde cerebroplegia (RCP). Our previous studies demonstrated that approximately 20% of perfused blood returns from the opened aortic arch when retrograde perfusion pressure is maintained around 25 mm Hg. Less blood returns if the pressure is lower than 15 to 20 mm Hg. Ffytche and colleagues [3] found that extrapolation of the pressure/velocity graph indicates a theoretical no-flow point of 8 mm Hg. Perfusion pressure was calculated by subtracting intraocular from mean blood pressure (MBP). Therefore, low perfusion pressure may not push sufficient blood to perfuse the brain.

In his letter, Dr Ono proposes that we "need to demonstrate that during the course of angiography, fluorencein was seen in retinal capillaries flowing retrograde to prove that RCP really perfuses porcine brain." Our explanation is that we only made qualitative observations of the fundus during retinal angiography, and did not observe capillaries in our animal studies. As a matter of fact, capillaries could not be observed by our retinal camera. However, we did observe background fluorescein. This may be a good starting point for further research.

Doctor Ono also mentioned that he was using a portable fundus camera (Kowa, Genesis) for taking rapid sequential retinal photographs and recommends this for clinical studies. We are very interested as to whether or not he has made any observations of capillaries.

References

1. Usui A., Oohara K., Liu T., et al. Determination of optimum retrograde cerebral perfusion conditions. J Thorac Cardiovasc Surg 1994;107:300-308.
2. Nojama T., Magara T., Nakajama Y., et al. Optimal perfusion pressure for experimental retrograde cerebral perfusion. J Card Surg 1994;9:548-559.
3. Ffytche T.J., Bulpitt C.J., Kohner E.M., et al. Effect of changes in intraocular pressure on the retinal microcirculation. Br J Ophthal 1974;58:514-522.

This Article Full Text (PDF) 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 Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dong, P. Articles by Wan, C. Search for Related Content PubMed Articles by Dong, P. Articles by Wan, C. Related Collections Cerebral protection Related Article