The effect of low-dose ketamine infusion on the remifentanil induced hemodynamic changes during general anesthesia

Remifentanil is known to produce side-effects of hypotension and
bradycardia. In this study, we
examine the effect of low-do
se ketamine infusion on the
heart rate and blood pressure of patie
nts anesthetized with remifentanil.
Methods:
In a randomized clinical trial,
54
patients aged
20-50
years old, with
ASA
physical status
Ι
, were studied in two groups (n=
27
), Ketamine- Remifentanil (
K-R
group)
and Placebo- Remifentanil (
P-R
group). Exclusion criteria were
ASA
physical status
>1
,
gastroesophageal reflux, t
achycardia, bradycardia, sy
stemic diseases, use of
antihypertensive drugs, difficult intubations, risk of aspiration and contraindications of
ketamine. Remifentanil was started at a rate of
0.5
μg. kg
-1
. min
-1
and anesthesia was
induced with thiopental sodium
2
mg.kg
-1
. Maintenance of anesthesia included halothane
and nitrous oxide/oxygen mixture. Remifentanil infusion was continued in both groups at
a rate of
0.5
μg.kg
-1
.min
-1
. In the
K-R
group, ketamine was started with an infusion rate of
10
μg.kg
-1
. min
-1
,
10
minutes after intubation, while in the
P-R
group, normal saline was
started with the same dose of remifentanil. Heart rate, systolic, diastolic and mean arterial
blood pressure were measured and compared at
1
,
3
,
5
,
10
,
15
,
20
,
25
and
30
minutes.
Results:
No significant differences were found be
tween basic patient characteristics of
mean of age, sex, weight, systolic, diastoli
c and mean arterial blood pressure and heart
rate (p
>0.2
) in the two groups. However, the rate of systolic, diastolic and mean arterial
blood pressure changes in the
P-R
group was significantly greater than that of the
K-R
group (p
<0.006
). Heart rate changes were sim
ilar between the two groups (p=
0.6
).
Incident of severe hypotension (a decrease of more than
25%
of the basic value) was less
in the
K-R
group than that of the
P-R
group (
11%
vs.
89%
; p=
0.000
).
Conclusion:
Low-dose ketamine infusion modulates the effect of remifentanil-induced
hypotension and provides better hemodynamic stability during general anesthesia.