How Much Cardiac Output is Enough?

Low output syndrome is a common complication in patients undergoing cardiac surgery. Its incidence was reported to be 2 to 6% [1]. Morbidity and mortality of low output syndrome is high and the costs for treating the disease are immense.

The primary objective of this prospective observational study is to define a threshold for a critically reduced cardiac output requiring immediate therapy.

Low output syndrome is a common complication in patients undergoing cardiac surgery. Its incidence was reported to be 2 to 6% [1]. In patients suffering from low output syndrome cardiac output is severely reduced due to myocardial failure. Among other reasons for myocardial failure, ischemia, insufficient myocardial protection during aortic cross-clamping, and severely reduced ventricular function prior surgery are the most common risk factors for low output syndrome. Low output syndrome is treated with positive inotropic drugs and mechanical assist devices [2]. Morbidity and mortality of low output syndrome is high and the costs for treating the disease are immense.

If cardiac output cannot be increased cardiac failure persist and vital organs are hypoperfused. Critical and prolonged hypoperfusion results in single and multi organ failure. Until today a definite threshold for a critically reduced cardiac output or cardiac index requiring immediate therapy is not completely known. Cardiogenic shock is diagnosed by clinical signs and it is not diagnosed by cardiac output or cardiac index. The critical value for a severely reduces cardiac index was reported to be in a range of 1.75 to 2.5L/min/m² [3-5].

The primary objective of this prospective observational study in 600 patients undergoing cardiac surgery is to try to define a threshold for a critically reduced cardiac output or cardiac index requiring immediate therapy.

If cardiac output and cardiac index are not reduced below a critical threshold, morbidity, mortality, and length of stay in the intensive care unit and in the hospital are reduced [6].

600 patients undergoing cardiac surgery

• Hausmann H, Potapov EV, Koster A, Krabatsch T, Stein J, Yeter R, Kukucka M, Sodian R, Kuppe H, Hetzer R. Prognosis after the implantation of an intra-aortic balloon pump in cardiac surgery calculated with a new score. Circulation. 2002 Sep 24;106(12 Suppl 1):I203-6.
• Lehmann A, Boldt J. New pharmacologic approaches for the perioperative treatment of ischemic cardiogenic shock. J Cardiothorac Vasc Anesth. 2005 Feb;19(1):97-108. Review. No abstract available.
• Böhrer H, Schmidt H, Motsch J, Gust R, Bach A, Martin E. Gastric intramucosal pH: a predictor of survival in cardiac surgery patients with low cardiac output? J Cardiothorac Vasc Anesth. 1997 Apr;11(2):184-6.
• Hochman JS, Sleeper LA, Webb JG, Sanborn TA, White HD, Talley JD, Buller CE, Jacobs AK, Slater JN, Col J, McKinlay SM, LeJemtel TH. Early revascularization in acute myocardial infarction complicated by cardiogenic shock. SHOCK Investigators. Should We Emergently Revascularize Occluded Coronaries for Cardiogenic Shock. N Engl J Med. 1999 Aug 26;341(9):625-34.
• Adams HA, Baumann G, Gänsslen A, Janssens U, Knoefel W, Koch T, Marx G, Müller-Werdan U, Pape HC, Prange W, Roesner D, Standl T, Teske W, Werner G, Zander R; I.A.G.-Schock. [Definition of shock types] Anasthesiol Intensivmed Notfallmed Schmerzther. 2001 Nov;36 Suppl 2:S140-3. German.
• Pölönen P, Ruokonen E, Hippeläinen M, Pöyhönen M, Takala J. A prospective, randomized study of goal-oriented hemodynamic therapy in cardiac surgical patients. Anesth Analg. 2000 May;90(5):1052-9.

Inclusion Criteria:

• Patients undergoing cardiac surgery,
• Written informed consent

Exclusion Criteria:

• Missing consent

• Klinikum der Stadt Ludwigshafen, Department of Anesthesiology and Intensive Care Medicine
• Klinikum der Stadt Ludwigshafen, Department of Cardiac Surgery