Thirty patients were included and analysed (Fig. 1). These patients had undergone cardiovascular surgery (n = 29) or thoracic surgery (n = 1) (Table 1). The main indications for fluid expansion were arterial hypotension (n = 17), SV change greater than 10% with PLR (n = 9), skin mottling (n = 4). No significant difference in indications was observed between SV responders and SV non-responders (p = 0.336). Values for EA(ESP), Ees and EA/Ees ratio were not significantly different between men and women, or according to type of surgery or medical characteristics (p value > 0.05), therefore allowing pooled analysis (Table 1). No patients developed complications (arrhythmia, hypoxaemia, left heart failure) during FC.
Table 1
Baseline characteristics of the study participants. Values are expressed as mean ± SD or number (%). CABG: coronary artery bypass graft. P value refers to comparison between ventriculo-arterial uncoupled and ventriculo-arterial coupled patients. Abnormal ventriculo-arterial coupling was defined as a EA/ELV ratio greater than 1.36
Variables | Ventriculo-arterial coupled patients (n = 7) | Ventriculo-arterial uncoupled patients (n = 23) | P value |
Age (mean (SD), years) | 66 (13) | 66 (12) | 0.947 |
Gender (F/M) | 1/6 | 7/16 | 0.638 |
Disease, n (%) Arterial hypertension Aortic stenosis Diabetes mellitus Dyslipidaemia Smoking | 5 (71) 5 (71) 3 (43) 5 (71) 4 (57) | 14 (61) 14 (61) 3 (13) 11 (48) 10 (44) | 1 1 0.120 0.399 0.675 |
Heart surgery, n (%) Valve replacement CABG Mixed Other (atrial myxoma, ascending aorta) Thoracic surgery, n (%) | 5 (71) 1 (14) 0 1 (14) 0 | 12 (52) 5 (22) 4 (17) 1 (4) 1 (4) | 0.589 |
Cardiopulmonary bypass time (min, mean (SD)) (n = 29) | 90 (46) | 99 (44) | 0.617 |
Respiratory parameters Tidal volume (ml kg− 1 of predicted body weight, mean (SD), Total PEEP (cmH2O, mean (SD)) | 7.8 (0.5) 5 (1) | 7.8 (0.7) 5 (1) | 0.957 0.443 |
Effect of FC on haemodynamic parameters in the overall study population
Prior to FC, median EA(ESP) was 2.3 [1.7–2.8] mmHg.ml− 1, median Ees was 1.5 [1-1.7] mmHg.ml− 1, and median EA(ESP)/Ees ratio was 1.8 [1.3–2.3]. Twenty-three (80%) of the 30 patients were classified as “uncoupled” (i.e. EA/Ees>1.36).
After FC, median EA(ESP) was 2.1 [1.5-3], median EA(ESP)/Ees ratio was 1.6 [1.3–2.1], and median Ees was 1.4 [0-1.7]. Twenty-three (80%) of the 30 patients were classified as fluid responders. Most uncoupled patients (21 out of 23 (91%); p = 0.003) were fluid responders.
Effect of FC on haemodynamic parameters depending on SV changes.
At baseline, EA(ESP), EA(ESP)/Ees, were higher and CA, Ci, SVi were lower in fluid responders than in fluid non-responders (Table 2, Figs. 2). In fluid responders, FC was associated with higher values for blood pressure, SVi, CI, SW, PVA, and SW/PVA ratio, and lower values for HR, SVRi, EA(ESP) and EA(ESP)/Ees ratio (Table 2, Fig. 2). In fluid non-responders, FC was associated with higher values for CVP and EA(ESP)/Ees ratio and a lower SW/PVA ratio (Table 2).
Table 2
Comparison of haemodynamic parameters in fluid responders and non-responders. Values are expressed as mean (SD) or median [interquartile range]. CI, indexed cardiac output; CVP, central venous pressure; DAP, diastolic arterial pressure; EDV, end-diastolic volume; ESV, end-systolic volume; FC, fluid challenge; HR, heart rate; LVEF, left ventricular ejection fraction; MAP, mean arterial pressure; PVA, pressure volume area; PP, pulse pressure; SAP, systolic arterial pressure; SVi, indexed stroke volume; SVRi, indexed systemic vascular resistance; SW, stroke work; $: p < 0.05 within groups (pre-/post-FC).
Haemodynamic variables | Non-responders (n = 7) | Responders (n = 23) | P value |
HR (bpm) Pre-FC Post-FC | 81 (23) 79 (19) | 84 (22) 77 (18) $ | 0.863 0.861 |
SAP (mmHg) Pre-FC Post-FC | 100 (21) 109 (22) | 103 (16) 125 (22) $ | 0.704 0.085 |
DAP (mmHg) Pre-FC Post-FC | 58 (11) 60 (12) | 58 (11) 66 (13) $ | 0.829 0.265 |
MAP (mmHg) Pre-FC Post-FC | 71 (12) 76 (12) | 73 (12) 86 (14) $ | 0.746 0.110 |
CVP (mmHg) Pre-FC Post-FC | 6 (3) 8 (2) $ | 6 (3) 8 (3) $ | 0.775 0.981 |
LVEF (%) Pre-FC Post-FC | 54 (11) 51 (8) | 48 (11) 50 (10) $ | 0.202 0.917 |
ESV (ml) Pre-FC Post-FC | 52 (21) 58 (23) | 58 (25) 60 (26) | 0.566 0.835 |
EDV (ml) Pre-FC Post-FC | 101 (22) 95 (20) | 86 (33) 112 (42) $ | 0.300 0.331 |
SVi (ml m− 2) Pre-FC Post-FC | 28 (8) 25 (5) | 22 (7) 29 (10) $ | 0.050 0.401 |
CI (ml min− 1 m− 2) Pre-FC Post-FC | 2.3 (0.9) 1.9 (0.8) | 1.7 (0.5) 2.2 (0.6) $ | 0.045 0.487 |
Arterial elastance (EA(ESP)) (mmHg ml− 1) Pre-FC Post-FC | 1.8 [1.4–2.2] 2 [1.6–2.6] | 2.5 [1.8–3.1] 2.2 [1.5–3.2] $ | 0.033 0.774 |
Arterial elastance (EA(MAP)) (mmHg ml− 1) Pre-FC Post-FC | 1.3 (1.1–1.8) 1.5 (1.3–1.8) | 1.9 (1.5–2.4) 1.7 (1.2–2.3) $ | 0.037 0.811 |
Arterial elastance (EA(R/T)) (mmHg ml− 1) Pre-FC Post-FC | 1.9 (1.7–2.7) 2.2. (1.9–2.7) | 3 (2.2–3.5) 2.6 (1.8–3.5)$ | 0.037 0.666 |
Arterial compliance (ml mmHg− 1) Pre-FC Post-FC | 1.6 (0.9) 1.1 (0.5) | 0.94 (0.32) 0.98 (0.37) | 0.014 0.455 |
SVRi (mmHg ml− 1 m− 2) Pre-FC Post-FC | 34 (13) 37 (10) | 47 (14) 38 (11) $ | 0.055 0.672 |
Ventricular elastance (Ees) (mmHg ml− 1) Pre-FC Post-FC | 1.6 (1.1-2) 1.5 (1.1–2.4) | 1.5 (0.9–1.7) 1.5 (0.9–1.7) | 0.564 0.564 |
EA(ESP)/Ees ratio Pre-FC Post-FC | 1.2 (0.9–1.4) 1.4 (0.9–1.8) $ | 1.9 (1.7–2.2) 1.5 (1.3-2) $ | 0.007 0.144 |
SW (joules) Pre-FC Post-FC | 4769 (1513) 4691 (1690) | 3672 (1349) 6032 (2040) $ | 0.077 0.126 |
PVA (joules) Pre-FC Post-FC | 6919 (1705) 7319 (1964) | 6111 (9132) 9164 (2868) $ | 0.329 0.124 |
SW/PVA ratio Pre-FC Post-FC | 0.69 (0.13) 0.64 (0.13) $ | 0.60 (0.14) 0.66 (0.12) $ | 0.136 0.761 |
Changes In Haemodynamic Parameters, E, E, And E/e Parameters
Changes in MAP (5% (-4 to 9) vs 16% (12 to 22), p < 0.05), SAP (6% (1 to 10) vs 18% (12 to 31%), p < 0.005), EA(ESP) (-13% (− 16% to -6) vs 0% (11 to 56), p < 0.05) were significantly different between SV responders and SV non-responders
Predictive value of E A , Ees, EA/Ees ratio and PPV.
At baseline, the EA/Ees ratio had a similar predictive value regardless of the EA formula used (EA(ESP)/Ees: 0.84 [95% confidence interval (95%CI)] (0.66-1), EA(MAP)/Ees: 0.83 (0.62-1), EA(R/T)/Ees: 0.82 (0.62-1), p < 0.05). A EA(ESP)/Ees cut-off of 1.4 gave a sensitivity of 87% [66–97], a specificity of 86% [42–100], a positive likelihood ratio of 6.1, negative likelihood ratio of 0.15, a positive predictive value of 95 and a negative predictive value of 67.
With an AUC [95%CI] of 0.75 [0.58–0.94] (p = 0.001), EA(ESP) was fairly predictive of fluid responsiveness. With an AUC [95%CI] of 0.39 [0.13–0.66] (p = 0.541), Ees did not predict fluid responsiveness.