Background and Objecitve: Preoperative fasting is
recommended to prevent pulmonary aspiration. Fasting
induces hypovolemia. Intravenous fluid infusion is
commonly given during anesthesia to minimize the
risk of hypotension. However, intravenous fluid overload
has been shown to deteriorate patient outcome.
From previous literatures, the effect of preoperative
fasting on intravascular volume is still inconclusive.
There is no previous study that assesses intravascular
volume status before and after fasting using the whole
body impedance cardiography which is a non-invasive,
practical and operator-independent. The reliability of
whole body impedance cardiography is comparable
to pulmonary artery thermodilution which is gold
standard. In this study, we assessed stroke volume
index (SVI) before and after fasting for 8 to 10 hours
using whole body impedance cardiography.
Methods: This is prospective observational study. We
included volunteers with American society of anesthesiologists
(ASA) physical status classification I–II with
age between 18-65 years old. SVI and other hemodynamic
parameters were measured before and after
fasting using whole body impedance cardiography.
The absolute change of hemodynamic parameters
before and after fasting more than 10% indicated
clinical significance. P value < 0.05 indicates statistical
significance.Results: Sixty-two volunteers were enrolled and
completed the study. SVI before and after overnight
fasting were 40.0±8.7 mL/m2 and 37.7±8.2 mL/m2,
respectively. SVI after fasting was decreased 5.5%. The
percentage absolute change of SVI in individual
volunteer was in a range between 3.1% to -17.0%.
Twelve subjects (19.4%) have decreased in SVI. Stroke
volume (SV), cardiac output (CO) and cardiac index
(CI ) were decreased 5. 6%, 6. 6% and 6. 4%,
respectively. All hemodynamic parameters except
heart rate were statistically decreased after fasting
(p< 0.05) but the absolute change less than 10%.
Conclusion: Overnight fasting does not clinically affect
SVI measured by whole body impedance cardiography
in healthy population. Some volunteers have
significantly decreased in SVI after fasting and
appropriate intravenous fluid therapy probably
improves CO.
Keywords
Whole body impedance cardiography; stroke volume index; fasting, hypovolemia