Effect of increasing heart rate and tidal volume on stroke volume variability in vascular surgery patients

Because heart rate affects ventricular filling, the aim of the present study was to assess the effects of increasing heart rate and tidal volume on stroke volume variability to determine whether this dynamic index is heart-rate dependent.

Prospective, randomized study.

Single university hospital.

Eighteen vascular surgery patients having general anesthesia and endotracheal intubation with an arterial catheter connected to the Vigileo FloTrac system (Edwards Lifesciences, Irvine, CA) and a transesophageal atrial pacemaker (CardioComman Inc, Tampa, FL).

A 2 × 2 factorial study of changes in heart rate (80 bpm and 110 bpm) and tidal volume (6 mL/kg and 10 mL/kg).

With tidal volume at 6 mL/kg, increasing heart rate from 80 mL/kg to 110 bpm caused stroke volume variability to increase from 12.2% ± 5.7% to 13.2% ± 5.3% (p<0.05), and with tidal volume at 10 mL/kg, increasing heart rate from 80 mL/kg to 110 bpm caused stroke volume variability to increase from 19.7% ± 7.9% to 22.0% ± 8.6% (p<0.05). In comparison, increasing tidal volume from 6 mL/kg to 10 mL/kg produced a significantly greater effect on stroke volume variability than increasing heart rate.

Stroke volume variability is sensitive to increases in heart rate in addition to tidal volume. Increasing heart rate caused stroke volume variability to increase significantly, although not to the same magnitude as increasing tidal volume. When using dynamic volume indices, clinicians should be aware of increases in heart rate, although its clinical impact may be relatively minor compared with changes in tidal volume.