الفهرس 
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Abstract
Laparoscopy has now become the standard technique for cholecystectomy.
However, the pneumoperitoneum (PNO) required for laparoscopy results in
pathophysiologic changes (Joris et al. 1993). More particularly, changes in
cardiovascular function occur during laparoscopy. These are characterized by an
increase in arterial pressure and systemic and pulmonary vascular resistances
(SVR and PVR) early after the beginning of intra-abdominal insufflation, with
insignificant changes in heart rate (HR). A 10% to 30% decrease in cardiac
output has also been reported in most studies (Joris et al.1993- Sharma et al.
1996).
Today the theraputic objective for administration of α2-adrenoceptor agonists
has shifted from reduction of high blood pressure to various other applications,
including the management of myocardial ischaemia and withdrawal symptoms
in drug addicts. The development of highly specific α2-adrenoceptor agonists
with profound effects on vigilance and haemodynamics has created new interest
for the use of α2-adrenoceptor agonists for use in anaesthesia and intensive care
medicine. α2-Adrenoceptor agonists possess a variety of pharmacological
properties that render them desirable as adjuncts in anaesthesia. Clonidine, an
imidazoline, is the prototypal α2-adrenoceptor agonist. It has a relatively slow
onset (0.5 h) and an elimination half-life of 9-12 h. The highly specific α2-
adrenoceptor-agonist dexmedetomidine was approved in the USA at the end of
1999 for sedation and analgesia in the intensive care unit (ICU). This drug
shows unique characteristics: patients are sedated but remain rousable and able
to cooperate with the hospital staff when stimulated. Moreover, in ICU therapy
with dexmedetomidine, there is no evidence of respiratory depression at clinical
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concentrations, and the heamodynamic changes are both moderate and
predictable (Bhana N et al. 2000).
The aim of this study is to compare the effect of two different infusion rates of
dexmedetomidine on perioperative heamodynamic responses to painful
stimulation, intubation, abdominal insufflation, anaesthetic requirement,
postoperative analgesia and postoperative complication during abdominal
laparoscopic procedure.This study was designed to include eighty patients of
both sexes, aged 20-50 years, ASAI&II physical status, who are scheduled for
elective abdominal laparoscopic cholecystectomy. All surgical procedures were
of an expected duration of 30-75 minutes.
All patients received the following drugs before the induction of anaesthesia:
· 7.5 mg oral midazolam one hour before induction of anaesthesia
· 0.5 mg IM atropine half an hour before induction of anaesthesia
Patients were randomly assigned into one of four groups, as follows:
Group I (control group) (n = 20): Patients in this group received placebo
(normal saline), infused intravenously over 10 minutes. Group II (n = 20):
Patients in this group received fentanyl 2μg/kg as a single dose followed by
saline infusion for 10 minutes. Group III (n = 20): Patients in this group
receive 0.5 μg/kg/h dexmedetomidine infusion 10 min before induction of
anaesthesia and till the end of the operation. Group IV (n = 20): Patients in this
group receive 1 μg/kg/h dexmedetomidine infusion 10 min before induction of
anaesthesia and till the end of the operation.
Ten minutes after administration of the study drug, the patients were given
Tracrium 0.5 mg/kg IV. Anaesthesia was induced with sleeping dose of
thiopental Na, after tracheal intubation with cuffed ETT a gas module for
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measurement of end-expiratory concentration of halothane and end-tidal carbon
dioxide tension was applied.
Data recorded as follow:
· Heart rate ( HR ), blood pressure ( systole, diastole, mean), respiratory
rate (RR), peripheral oxygen saturation ( Spo2) were recorded in the
following times:
- on arrival of the patients to the operating room
- Every 2 minutes after study drug administration for 10 minutes.
- Every 10 min in the recovery room for 2 hours
· Heart rate ( HR ), blood pressure ( systole, diastole, mean),respiratory rate
(RR), End tidal CO2 concentration (ETCO2), peripheral oxygen saturation
( Spo2), End tidal halothane concentration will be recorded at the
following times:
- immediately after intubation
- every 2 min until 10 min after intubation then every 3 min for 15
min
- Every 5 min during the rest of the operation.
· Recovery was assessed by recording the time from extubation to
spontaneous eye opening.
· Post-operative analgesic requirement was assessed by recording the time
to 1st request of post-operative analgesia.
When comparing the four study groups together it was found that group 3 and 4
demonstrated statistically significant decrease in the heart rate, blood pressure
and intraoperative halothane consumption compared with group 1 and 2 from
intubation till the end of the surgery. Respiratory rate, SPO2, ETCO2 were
comparable in all groups through the study period. There were insignificant
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differences between the study groups with respect to time from extubation till
spontaneous eye opening, group 3 and 4 demonstrated statistically significant
lower time to request of postoperative analgesia when compared with group 1
and 2.