Samantha Rampal, Hardyal Rampal
(2008)
The effects of pre-induction intra venous
dexmedetomidine on intraoperative sevoflurane requirement.
Masters thesis, Universiti Sains Malaysia.
Abstract
Dexmedetomidine is a highly selective a.2-adrenoreceptor agonist with potent
sedative, anaesthetic-sparing and analgesic effects. Due to these effects, it has currently
become an important adjuvant to current anaesthetic practi9es. The aim of this study is to
evaluate if there is a reduction in the amount of expired fraction of intraoperative sevoflurane
used with dexmedetomidine given as a single intravenous (i.v) dose of lJ.Lg/kg, 10 minutes
before anaesthetic induction.
A prospective, randomized double-blinded clinical trial was conducted on 60 patients
planned for minor orthopaedic procedures less than 3 hours of duration. This was done in a
time frame of twelve (12) months, between August 2006 and August 2007 at the operation
theater of Hospital Universiti Sains Malaysia (HUSM).
Sixty patients were randomized to receive either dexmedetomidine (n=30) or normal
saline (n=30). Sedation score was evaluated using Ramsey sedation scale during and after
drug administration, till patients were induced with fentanyl, sodium thiopentone and
rocuronium. Anaesthesia continuation was maintained with 30%: 70% oxygen: nitrous oxide.
Amount of sevoflurane administered was adjusted to maintain the bispectral index scale
between 40 and 60. The expired fraction of sevoflurane, haemodynamic parameters and analgesia
requirement were recorded at 5 minute intervals throughout the intraoperative period. The
extubation time, which is the duration taken from the cessation of sevoflurane administration
to the time patient is extubated was noted. The postoperative pain score (VAS) was
documented at the recovery.
Results show that there was a 27.8% reduction in the expired fraction of sevoflurane
and a 25% drop ~ the thiopentone requirement in the dexmedetomidine group. The mean
heart rate was also significantly lower in the dexmedetomidine compared to normal saline
group [mean (CI): 69.20 (64.03, 74.37) versus 82.00 (72.12, 91.87) per minute, p = 0.005].
Patients, who received dexmedetomidine, were observed to be more sedated just before
induction when compared to patients who received normal saline. The postoperative pain
score (VAS) was significantly lower in the dexmedetomidine compared to normal saline
group [mean (SD) 1.507 (0.275) versus 2.209(0.403), p= 0.005].There were no significant
differences observed in the demographic characteristics, the mean systolic and diastolic
blood pressure measurements and the extubation time between the two groups.
In conclusio~ preoperative administration of a single dose intravenous
dexmedetomidine decreased the expired fraction of sevoflurane by 27.8% in minor
orthopaedic surgeries and has proven to be a good anaesthetic adjuvant as it not only blunts
the haemodynamic response to intubation but also reduces the postoperative opioid
requirement. Patients were noted to be. more comfortable, alert and complained of less pain
during the postoperative period.
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