Usefulness of Cardiac Index to Predict Early and 30-Day Mortality in Non-Cardiac Patients Being Admitted to Intensive Care Units

Cardiac index is a hemodynamic parameter defined as the ratio of the cardiac output, i.e., the volume of blood ejected from the left ventricle in 1 min, to the body surface area. This study aimed to assess the cardiac index to predict early and 30-day outcomes of non-cardiac patients being admitted to intensive care units using a non-invasive approach. Materials and Methods: This prospective cohort study included 31 non-cardiac patients who were consecutively admitted to the intensive care units of Rasoul-e-Akram Hospital, Tehran, Iran, in 2016. On admission, the simplified acute physiology score II to predict mortality and the cardiac output (by two-dimensional echocardiography) of each patient were determined. The cardiac index was calculated by dividing the cardiac output by the body surface area. In-hospital mortality and complications were assessed, and the association between simplified acute physiology score II and cardiac index was determined. The patients were followed-up 30 days after discharge by telephone to determine late death, occurrence of myocardial infarction, readmission, or re-hospitalization. Results: The mean cardiac index was significantly lower among the patients who died in intensive care units than in those who survived (2.86 ± 0.63 versus 3.70 ± 0.49, p = 0.006). A significant inverse association was found between Simplified Acute Physiology Score II and cardiac index (r = −0.539, p = 0.002). The length of hospital and intensive care units stay was not associated with Simplified Acute Physiology Score -II or cardiac index. The receiver operating characteristic curve analysis revealed that the cardiac index was effective in predicting in intensive care units mortality (area under curve = 0.857, p = 0.007). The best cut-off value for the cardiac index to predict in intensive care units mortality was 3.35, yielding a sensitivity of 83.3% and a specificity of 80.0%. Conclusion: Measuring the cardiac index during intensive care units admission using a noninvasive approach even in non-cardiac patients can predict in intensive care units mortality with high sensitivity and specificity . INTRODUCTION Cardiac index (CI) is a hemodynamic parameter defined as the ratio of the cardiac output, i.e., the volume of blood ejected from the left ventricle in 1 min, to the body surface area (BSA). It is a useful indicator of how well the heart is functioning as a pump (4) and is directly related to some cardiac characteristics, such as the power of heart performance, myocardial contractility, and cardiac size; thus, it tends to vary between individuals (1,2). The CI is usually assessed in critically ill patients to determine their cardiac function. Thermo-dilution via pulmonary artery catheter is a gold standard technique to measure the cardiac output (3). The CI is also considered as an important physiological and metabolic indicator of the metabolic status of various organs because the cardiac output is closely associated with the metabolic health of the organs (5,6). The cardiac function as a pump deteriorates due to several factors such as excessive weight and intraventricular conduction disorders in patients with acute coronary syndrome (7, 8). Thus, it can be expected that the CI is considerably reduced in patients with functional impairment of vital organs, such as heart failure patients, critically ill patients, or those with metabolic disturbances. In addition, because many patients do not complete follow-up so refuse to undergo invasive procedures, CI assessment via noninvasive approaches will be valuable for determining the degree of cardiac performance or metabolic dysfunction (9). Hence, the present study aimed to assess the CI to predict early and 30-day outcomes of non-cardiac patients being admitted to intensive care units (ICUs) using a noninvasive approach. MATERIALS AND METHODS This prospective cohort study included 31 non-cardiac patients who were consecutively admitted to the ICUs of Key words: Intensive care unit (ICU), Cardiac Index (CI), Mortality Conflicts of interest: None Funding: None Received 2018-07-12 Accepted: 2 018-08-21 Published: 2019-02-30 V olume: 4 Issue: 1