Haemodynamics Are Age Dependent and Have Little Impact on the Use of Inotropes and Constrictors

Low cardiac output syndrome (LCOS) is common in patients undergoing cardiac surgery contributing to morbidity and mortality. LCOS increases length hospital stay and costs, making it desirable to diminish its occurrence and attenuate its severity. What is an inadequate cardiac output during and after cardiac surgery is a key question. It has been suggested that LCOS was present if cardiac index (CI) < 2.4 L/min/m2 with simultaneous evidence of organ dysfunction. However, we know from today’s population of cardiac surgery patients that many patients have an uncomplicated course, even with a CI less than 2.0 L/min/m2. CI in otherwise healthy subjects decreases with age, but considerable inter-patient differences and intra-patient variation has been shown. The aim of this study is to describe CI, mixed venous saturation (SvO2) and mean arterial blood pressure (MAP) related to age, thus contributing to establish a definition of LCOS. Observational cohort study of 8,963 patients from our heart registry merged with data from our electronic patient management system. Data were divided primarily on age and gender and associated to perioperative vasoconstrictor and inotropic treatment. Data was retrieved as average pre-bypass and post-bypass data for each patient. Median values of CI correlated with age, ranging from 2.28 (2.03-2.65) in patients younger than 50 to 1.92 (1.68-2.21) in patients older than 80 years. Mixed venous saturations showed the same correlation while mean arterial blood pressure did not correlate the same way. Females have significant lower MAP values. Otherwise no differences were found in gender. Patients treated with inotropes or constrictors were correlated to age, the fraction increasing from 37.9 % (< 50 yrs) to 69.4 % (80+ yrs). Overall the fraction of patients receiving perioperative vasoactive medication was only 2.2% in pre-bypass values above or below median values and 4.0% in post-bypass values. Regarding SvO2 the difference between above and below values was somewhat higher being 10.7 % in pre-bypass values and 14.0% in post bypass values. Low SvO2 seems to have a higher treatment fraction in younger patients while no difference is seen in 80 plus patients. Cardiac index and mixed venous saturations are highly associated with age in cardiac surgery patients. CI is a relatively poor indicator of vasoactive treatment in all age groups while mixed venous saturation seems to influence more, especially in younger patients.