Hemodynamic effects of slower versus faster intravenous fluid bolus rates in critically ill patients: An observational study

Abstract

Purpose: We compared the immediate and sustained effects of 500 mL of crystalloid administered at slow (333 mL/h) versus fast rates (999 mL/h) on mean arterial pressure (MAP) in critically ill patients.

Materials and methods: Hemodynamic variables were collected immediately before and every 30 min up to 60 min after the end of the infusion. The primary outcome was the adjusted difference in MAP.

Results: We included 146 patients (slow rate: 71, fast rate: 75). One hour after the end of the infusion, there was no difference in the overall mean marginal effect on MAP between the groups [1.9 mmHg (95 % CI: -1.5 to 5.3 mmHg), p = 0.27] or on the perfusion parameters. Similarly, no difference was found in the immediate effect after 90 min [overall marginal effect: 1.1 mmHg (95 % CI: -2.3 to 4.6 mmHg); p = 0.52]. In patients with cardiac output (CO) monitoring, there was an increase in CO in the fast rate group (overall mean marginal effect: 1.78 L/min (95 % CI: 0.08 to 3.48 L/min); p = 0.04).

Conclusion: In critically ill patients, crystalloid infusion at both fast and slow rates did not lead to immediate or sustained differences in MAP. However, fast infusion may result in a greater increase in CO.

Keywords: Cardiac output; Fast infusion; Fluid bolus; Mean arterial pressure; Rate of infusion; Slow infusion.