Maintenance fluid therapy and fluid creep impose more significant fluid, sodium, and chloride burdens than resuscitation fluids in critically ill patients: a retrospective study in a tertiary mixed ICU population

Abstract

Purpose: Research on intravenous fluid therapy and its side effects, volume, sodium, and chloride overload, has focused almost exclusively on the resuscitation setting. We aimed to quantify all fluid sources in the ICU and assess fluid creep, the hidden and unintentional volume administered as a vehicle for medication or electrolytes.

Methods: We precisely recorded the volume, sodium, and chloride burdens imposed by every fluid source administered to 14,654 patients during the cumulative 103,098 days they resided in our 45-bed tertiary ICU and simulated the impact of important strategic fluid choices on patients' chloride burdens. In septic patients, we assessed the impact of the different fluid sources on cumulative fluid balance, an established marker of morbidity.

Results: Maintenance and replacement fluids accounted for 24.7% of the mean daily total fluid volume, thereby far exceeding resuscitation fluids (6.5%) and were the most important sources of sodium and chloride. Fluid creep represented a striking 32.6% of the mean daily total fluid volume [median 645 mL (IQR 308-1039 mL)]. Chloride levels can be more effectively reduced by adopting a hypotonic maintenance strategy [a daily difference in chloride burden of 30.8 mmol (95% CI 30.5-31.1)] than a balanced resuscitation strategy [daily difference 3.0 mmol (95% CI 2.9-3.1)]. In septic patients, non-resuscitation fluids had a larger absolute impact on cumulative fluid balance than did resuscitation fluids.

Conclusions: Inadvertent daily volume, sodium, and chloride loading should be avoided when prescribing maintenance fluids in view of the vast amounts of fluid creep. This is especially important when adopting an isotonic maintenance strategy.

Keywords: Chloride; Fluid creep; Fluid overload; Fluid therapy; Hyperchloremia; Maintenance fluids; Sodium.

Fig. 1

Proportion, mean, and median fluid volumes, and mean sodium and chloride burdens of the different fluid types (average of 14,654 patients on their cumulative 103,098 days of ICU stay), including a graphic representation of the distribution of the different mean daily fluid volumes. Mean duration of one ICU day, 20.3 ± 6.7 h. SD standard deviation, IQR interquartile range, N/A data not available. ^aTo ensure optimal electrolyte management in our ICU, only electrolyte-free formulas of parenteral nutrition are prescribed, with separate administration of electrolytes

Fig. 2

Day-per-day proportions of the mean volumes of the different fluid types, administered during the first 5 days of ICU stay. ^aFirst day of admission runs from time of admission until 8:00 AM; day of discharge runs from 8:01 AM until time of discharge

Fig. 3

Light and dark orange (left): actual chloride administration due to balanced resuscitation fluids as retrieved from the dataset, flanked by the simulated amount if these had been unbalanced. Light and dark blue (right): actual chloride administration due to maintenance fluid strategy as retrieved from the dataset, in which hypotonic fluids were prescribed if the clinical situation allowed, flanked by the simulated amount if these fluids had been isotonic. Black bars represent standard error bars

Fig. 4

Impact of non-resuscitation (maintenance, replacement, and creep) and resuscitation fluids on cumulative fluid balance during the first 5 days of ICU stay in the subgroup of medical patients admitted with sepsis (n = 1229). Simulation based on the statistical model, using the mean SAPS-3 score of 63 and the real-life fluid volumes. For details, see text and in Supplemental File 2