Fluid management in critically ill patients: the role of extravascular lung water, abdominal hypertension, capillary leak, and fluid balance

Abstract

Introduction: Capillary leak in critically ill patients leads to interstitial edema. Fluid overload is independently associated with poor prognosis. Bedside measurement of intra-abdominal pressure (IAP), extravascular lung water index (EVLWI), fluid balance, and capillary leak index (CLI) may provide a valuable prognostic tool in mechanically ventilated patients.

Methods: We performed an observational study of 123 mechanically ventilated patients with extended hemodynamic monitoring, analyzing process-of-care variables for the first week of ICU admission. The primary outcome parameter was 28-day mortality. ΔmaxEVLWI indicated the maximum difference between EVLWI measurements during ICU stay. Patients with a ΔmaxEVLWI <-2 mL/kg were called 'responders'. CLI was defined as C-reactive protein (milligrams per deciliter) over albumin (grams per liter) ratio and conservative late fluid management (CLFM) as even-to-negative fluid balance on at least two consecutive days.

Results: CLI had a biphasic course. ΔmaxEVLWI was lower if CLFM was achieved and in survivors (-2.4 ± 4.8 vs 1.0 ± 5.5 mL/kg, p = 0.001; -3.3 ± 3.8 vs 2.5 ± 5.3 mL/kg, p = 0.001, respectively). No CLFM achievement was associated with increased CLI and IAPmean on day 3 and higher risk to be nonresponder (odds ratio (OR) 2.76, p = 0.046; OR 1.28, p = 0.011; OR 5.52, p = 0.001, respectively). Responders had more ventilator-free days during the first week (2.5 ± 2.3 vs 1.5 ± 2.3, p = 0.023). Not achieving CLFM and being nonresponder were strong independent predictors of mortality (OR 9.34, p = 0.001 and OR 7.14, p = 0.001, respectively).

Conclusion: There seems to be an important correlation between CLI, EVLWI kinetics, IAP, and fluid balance in mechanically ventilated patients, associated with organ dysfunction and poor prognosis. In this context, we introduce the global increased permeability syndrome.

Keywords: abdominal pressure; capillary leak; extravascular lung water; fluid balance; fluid management; organ failure; prognosis.

Figure 1

Time course of main variables. Mean ± standard error of pertinent variables for the first week after ICU admission. Survivors are depicted by a full line and nonsurvivors by a dotted line. *p < 0.05, day-by-day pairwise compared between survivors and nonsurvivors (one-way ANOVA).

Figure 2

Receiver-operating characteristic (ROC) curve. Sensitivity and specificity of Δ_maxEVLWI with respect to 28-day mortality according to ROC analysis in 123 patients. The Area under the curve (AUC) was 0.822.

Figure 3

Evolution of cumulative fluid balance in (non)responders. Mean ± standard error cumulative fluid balance for the first week after ICU admission. Responders are depicted by a full line and nonresponders by a dotted line. *p < 0.05, day-by-day pairwise compared between responders and nonresponders (one-way ANOVA).

Figure 4

Kaplan-Meier plots. Kaplan-Meier plots for cumulative survival and proportion of patients on MV. We compared CLFM and no CLFM achievement (full lines and dotted lines, respectively) in A (survival) and B (ventilation). In C (survival) and D (ventilation), responders and nonresponders were compared (full lines and dotted lines, respectively).

Figure 5

Proposed time course in shock, introducing a three-hit model and global increased permeability syndrome.