IJCS | Volume 33, Nº3, May / June 2020

242 26. SellmanM, Intonti MA, Ivert T. Reoperations for bleeding after coronary artery bypass procedures during 25 years. Eur J Cardiothorac Surg. 1997;11(3):521-7. 27. Frater RW, Oka Y, Hong Y, Tsubo T, Loubser PG, Masone R. Protamine- induced circulatory changes. J Thorac Cardiovasc Surg. 1984;87(5):687-92. 28. Gomes WJ, Leal JC, Braile DM, Guimarães JA, Lopes RD, Lima MA, et al. A Brazilian perspective for the use of bovine heparin in open heart surgery. Int J Cardiol. 2016 Nov 15;223:611-2. 29. Wu R, Glen P, Ramsay T, Martel G. Reporting quality of statistical methods in surgical observational studies: protocol for systematic review. Syst Rev. 2014 Jun;3:70. 30. Demange MK, Fregni F. Limits to clinical trials in surgical areas. Clinics. 2011;66(1):159-61. Lima et al. Unfractionated bovine heparin safety Int J Cardiovasc Sci. 2020; 33(3):235-242 Original Article This is an open-access article distributed under the terms of the Creative Commons Attribution License