Variability in usual care fluid resuscitation and risk-adjusted outcomes for mechanically ventilated patients in shock

Abstract

Rationale: There remains significant controversy regarding the optimal approach to fluid resuscitation for patients in shock. The magnitude of care variability in shock resuscitation, the confounding effects of disease severity and comorbidity, and the relative impact on sepsis survival are poorly understood.

Objective: To evaluate usual care variability and determine the differential effect of observed and predicted fluid resuscitation volumes on risk-adjusted hospital mortality for mechanically ventilated patients in shock.

Methods: We performed a retrospective outcome analysis of mechanically ventilated patients admitted to intensive care units using the 2013 Premier Hospital Database (Premier, Inc.). Observed and predicted hospital mortality were evaluated by observed and predicted day 1 fluid administration, using the difference in predicted and observed outcomes to adjust for disease severity between groups. Both predictive models were validated using a second large administrative database (Truven Health Analytics Inc.). Secondary outcomes included duration of mechanical ventilation, hospital and ICU length of stay, and cost.

Results: Among 33,831 patients, observed hospital mortality was incrementally higher than predicted for each additional liter of day 1 fluid beginning at 7 L (40.9% vs. 37.2%, p = 0.008). Compared to patients that received expected (± 1.5 L predicted) day 1 fluid volumes, greater-than-expected fluid resuscitation was associated with increased risk-adjusted hospital mortality (52.3% vs. 45.0%, p < 0.0001) among all patients with shock and among a subgroup of shock patients with comorbid conditions predictive of lower fluid volume administration (47.1% vs. 41.5%, p < 0.0001). However, in patients with shock but without such conditions, both greater-than-expected (57.5% vs. 49.2%, p < 0.0001) and less-than-expected (52.1% vs. 49.2%, p = 0.037) day 1 fluid resuscitation were associated with increased risk-adjusted hospital mortality.

Conclusions: Highly variable day 1 fluid resuscitation was associated with a non-uniform impact on risk-adjusted hospital mortality among distinct subgroups of mechanically ventilated patients with shock. These findings support closer evaluation of fluid resuscitation strategies that include broadly applied fluid volume targets in the early phase of shock resuscitation.

Keywords: Circulatory collapse; Clinical decision-making; Critical care outcomes; Critical care/utilization; Fluid therapy/mortality.

Fig. 1

Patient and hospital selection. The 2013 Premier Hospital Database includes hospital discharges from January 1, 2013, to December 31, 2013. ICU intensive care unit, ED emergency department

Fig. 2

The effect of day 1 fluid resuscitation volume on hospital mortality. Observed vs. predicted hospital mortality by a) day 1 fluids for all patients, b) day 1 fluids for shock patients with or without one or more fluid reductive factors (FRFs), and c) number of FRFs. The difference between observed and predicted mortality is significant when 95% CI bars do not cross the line for predicted mortality

Fig. 3

The effect of greater- or less-than-expected day 1 fluid volume resuscitation on hospital mortality. Risk-adjusted observed vs. predicted hospital mortality for patients with shock. Risk adjustment performed by adding the difference in predicted hospital mortality between expected-resuscitation and less-than-expected or greater-than-expected groups to their respective observed hospital mortality. FRF fluid reductive factor. Asterisk indicates statistically significant difference in observed hospital mortality when compared to the expected-resuscitation group^{. †}Less-than-expected = difference between observed and predicted day 1 fluids is less than − 1.5 L. ^‡Expected = difference between observed and predicted day 1 fluids is between − 1.5 and 1.5 L. ^§Greater-than-expected = difference between observed and predicted day 1 fluids is more than 1.5 L

Fig. 4

Variability in day 1 fluid resuscitation volumes. Modified box-and-whiskers plots (box ends indicate 25th and 75th percentiles, whiskers indicate 10th and 90th percentiles, and middle lines indicate medians) for prescribed day 1 fluids. Differences in medians between w/ FRF and w/o FRF groups, as well as between less-than-expected, expected, and greater-than-expected resuscitation groups, are statistically significant (p < 0.0001). FRF fluid reductive factor. *Less-than-expected = difference between observed and predicted day 1 fluids is less than − 1.5 L. ^†Expected = difference between observed and predicted day 1 fluids is between − 1.5 and 1.5 L. ^‡Greater-than-expected = difference between observed and predicted day 1 fluids is more than 1.5 L