A comparison of blood pressure reduction after propofol lnduction in elderly between overnight fasting and 2-hour fasting of clear liquids: prospective single-blinded randomized controlled trial

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Saranant Logutarapoom


esthesiologist guidelines have recommended at
least 2 hours of clear fluids abstinence prior to
elective procedures requiring general anesthesia in
adults. Practically, all patients are prescribed to have
nothing per oral after midnight for both solids and
clear fluids. This unpredictably prolonged fasting
time leads to dehydration and exaggerates hypotension
during an induction of general anesthesia especially in
elderly patients. We hypothesized that the reduction
of blood pressure after propofol induction is lower
in patients allowed to drink water until 2 hours prior
to surgery comparing to routinely-fasted patients.
Methods: One hundred ASA II-III patients aged over
65 years were preoperatively randomized to have last
clear fluids before midnight (AMN; control group,
n=50) and at least 2 hours before a scheduled surgery
time (2-hour; study group, n=50). Intravenous fluid was
started at 6.00 am. and infused at a weight-based rate.
Propofol was administered at a rate of 1 mg/kg/min.
The primary outcome was a reduction of blood
pressure after induction. Results: There were no
differences in a blood pressure reduction at any times
after induction (24.20±18.03 vs 24.12±20.36 mmHg,
p-value=0.983). Eight patients in 2-hour group did not
drink anything after midnight. As per-protocol analysis
(AMN; n=58, 2-hour; n=42), the decrease of blood
pressure was not different (p-value=0.811). The
2-hour group had significantly higher percentage of
the patients with no perception of thirst (p-value
=0.003). Moreover, estimating relations between
variables using Quantile regression method, we found
two factors, a higher dose of propofol and a lower total
volume received including orally and intravenously,
associated with a larger reduction of blood pressure
(p-value=0.043, and 0.042, respectively). Conclusions:
Two-hour clear fluids fasting patients had an
insignificant difference in blood pressure reduction
after induction of anesthesia with propofol comparing
to traditional overnight fasting. However, the thirst
perception was less in 2-hour group.

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Original articles


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