Ann Thorac Surg 2004;77:1670
© 2004 The Society of Thoracic Surgeons
Invited commentary
Marek Ehrlich, MD
Department of Cardiothoracic Surgery, University of Vienna Wahringer Gurtel 18-20 A-1090 Vienna, Austria
e-mail: marekehrlich{at}hotmail.com
Operations on the aortic arch still remain a great challenge for cardiac surgeons and necessitate a period of cerebral blood flow interruption. The introduction of profound hypothermia and circulatory arrest [1] have been major contributors to the surgical treatment of thoracic aortic diseases. Since then, hypothermia and circulatory arrest has been a valuable adjunct in aortic surgery, responsible for markedly decreased mortality, as well as morbidity rates in these procedures [2].
In recent years, however, a number of surgeons have enthusiastically adopted the use of retrograde cerebral perfusion (RCP) as a means of improving neurological outcome after complex cardiovascular and aortic surgery, even though considerable uncertainty exists regarding both the efficacy and the safety of this technique [3, 4]. The appeal of RCP lies in its possible benefit both in reducing embolic injury and in prolonging the safe duration of hypothermic circulatory arrest [5].
In almost all of the clinical as well as experimental studies was the question addressed whether RCP provides adequate capillary perfusion in the brain. In this issue of the Journal, Ye and colleagues investigated the effect of pH-management in conjunction with RCP. They hypothesized that the use of pH-stat strategy during RCP would increase cerebral blood flow because of increased vasodilatation and reduced vascular resistance. It is well known that pH stat seems to be superior in children, where cooling times may be somewhat short, and adequacy of cooling is not monitored by measuring jugular venous saturation. Since pH stat results in greater vasodilatation, it may result in faster and better cooling—as proven in this paper. Although Ye and colleagues demonstrate for the first time that pH stat during RCP seems to be superior to 
-stat with regard to cerebral blood flow and tissue oxygen saturation, there is one major drawback in this study design—the group did not ligate the azygous as well as hemiazygous vein during RCP. It was shown that even with ligation of the azygous and hemiazygous veins before implementation of RCP, 90% of the superior vena cava inflow during RCP is nevertheless shunted into the inferior vena cava and recirculated and only 0.1% of superior vena cava inflow reaches brain capillaries [6]. Thus, the results accomplished in this paper should be interpreted with caution. Nevertheless, this paper adds more data to the engimatic subject of how to protect the brain optimally during the period of circulatory arrest.
References
- Griepp RB, Stinson EB, Hollingsworth JF, Buhler D. Prosthetic replacement of the aortic arch.
- Ergin MA, O'Connor JV, Guinto R, Griepp RB. Experience with profound hypothermia and circulatory arrest in the treatment of aneurysms of the aortic arch: aortic arch replacement for acute arch dissections. J Thorac Cardiovasc Surg 1982;84:649–55.
- Ueda Y, Miki S, Kusuhara K, Okita Y, Tahata T, Yamanaka K. Surgical treatment of aneurysm or dissection involving the ascending aorta and aortic arch, utilizing circulatory arrest and retrograde cerebral perfusion. J Cardiovasc Surg 1990;31:553–8.
- Usui A, Abe T, Murase M. Early clinical results of retrograde cerebral perfusion for aortic arch operations in Japan. Ann Thorac Surg 1996;62:94–104.
- Usui A, Oohara K, Tong-lin L, Murase M, Tanaka M, Takeuchi E, et al. Comparative experimental study between retrograde cerebral perfusion and circulatory arrest. J Thorac Cardiovasc Surg 1994;107:1228–7.
- Ehrlich MP, Hagl C, McCullough JN, Zhang N, Shiang H, Bodian C, et al. Retrograde cerebral perfusion provides negligible flow through brain capillaries in the pig. J Thorac Cardiovasc Surg 2001;122:331–8.
