12 Henling CE, Carmichael MJ, Keats AS, Cooley DA. Cardiac operation for congenital heart disease in children of Jehovah's Witnesses. J Thorac Cardiovasc Surg 1985 ;89:914-920 ; Spahn DR, Pasch T. Erythrocyte substitution : What is known about the critical hematocrit. Infusiontherapie 1997 ;24:100- 105.