Evaluation of volume overload in critical patients by monitoring change of cardiac output under bed head raising combined with passive leg raising

OBJECTIVE:To investigate whether the change of cardiac output (CO) with bed head raising (BHR) combined with passive leg raising (PLR) can be used to assess volume overload in critical patients. METHODS:A prospective observational diagnostic trial was designed. The patients who underwent fluid resuscitation 6 hours or more, and admitted to intensive care unit (ICU) of Meizhou People's Hospital in Guangdong Province from January to December in 2016 were enrolled. Volume overload were identified with the criteria including the increasing of pulmonary rales, the higher levels of N-terminal brain natriuretic peptide (NT-proBNP) and new pulmonary exudates in chest radiograph. CO and heart rate (HR) were monitored with impedance cardiography at supine position and BHR by 30degree angle (BHR30), 60degree angle (BHR60), and PLR in all patients. The changes of CO (ΔCO30, ΔCO60, ΔCOPLR) and HR (ΔHR30, ΔHR60, ΔHRPLR) were calculated at different positions. The receiver operating characteristic curve (ROC) was used to evaluate the predictive values of ΔCO30, ΔCO60 and combination of ΔCO60 and ΔCOPLR on volume overload. RESULTS:A total of 62 patients were enrolled in this study, with 44 males and 18 females, age of (58.9±15.9) years, a body mass index of (22.7±2.4) kg/m2, and an acute physiology and chronic health evaluation II (APACHE II) score of 18.7±4.4. The CO of 32 patients with volume overload was significantly increased at BHR30 or BHR60 compared with supine position [ΔCO30 was (14.5±11.5)%, ΔCO60 was (26.9±17.5)%, both P 0.05). There was no consistent change of CO at BHR30 or BHR60 compared with supine position in 30 patients without volume overload, ΔCO30 was (-3.4±9.1)% (P 0.05), while CO was significantly increased after PLR, ΔCOPLR was (12.4±11.3)% (P < 0.01). There was no significant change of HR after BHR and PLR in patients with volume overload and non volume overload. ROC curve showed that when the cut-off value of ΔCO30≥3.3%, the area under ROC curve (AUC) was 0.903±0.039, the sensitivity was 90.6%, the specificity was 80.0%, and the accuracy was 85.5% for predicting volume overload; when the cut-off value of ΔCO60≥5.6%, the AUC was 0.911±0.036, the sensitivity was 96.9%, the specificity was 73.3%, and the accuracy was 85.5% for predicting volume overload. If volume overload was assessed by the increase of ΔCO60 combining with the decrease of ΔCOPLR, the AUC was 0.928±0.034, the optimal cut-off value for the new combined predictive indicator in predicting volume overload was -0.008, and the sensitivity, specificity, accuracy was 96.9%, 83.3%, 90.3%, respectively, and its evaluation effect is better than the use of ΔCO30 or ΔCO60 alone. CONCLUSIONS:The change of CO with BHR combined with PLR can be used to accurately evaluate volume overload in patient with critically illness.