الفهرس 
Spinal Anesthesia
PHYSIOLOGIC EFFECTSOnly 14 pages are availabe for public view
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Abstract
Lower limb orthopedic surgeries performed under
spinal anesthesia has the advantage of having rapid onset,
maintaining spontaneous breathing, relaxing the necessary
muscles for surgery, and cost effectiveness. It also has the
advantage of being free from the risks of intubation and
pulmonary aspiration. Prolonging the duration of spinal
anesthesia would allow longer surgical interventions.
Various additives have been used in order to prolong the
duration of spinal anesthesia e.g ketamine, magnesium and
clonidine. Agents such as opioids and neostigmine have
also been used.
Dexmedetomidine is a centrally acting α2 receptor
agonist that can be titrated to the desired level of sedation
without significant respiratory depression. It has an
analgesic-sparing effect, significantly reducing Opioid
requirements both during and after surgery.
Dexmedetomidine also has a sympatholytic effect that can
attenuate the stress response to surgery mitigating
tachycardia and hypertension. Because of its analgesic
properties, ”cooperative sedation” and lack of respiratory
depression, Dexmedetomidine is increasingly being used as
a sedative and adjuvant in anesthesia.
Dexmedetomidine has been used safely in patients
undergoing surgical procedures under regional anesthesia.
Intravenous and intrathecal dexmedetomidine showed to prolong the duration of spinal analgesia and decrease
postoperative analgesia.
Our study was designed to explore whether
dexmedetomidine by intrathecal or IV route has superior
synergistic effects to bupivacaine spinal anesthesia in
patients undergoing lower limb orthopedic surgeries as
regard patient hemodynamics, spinal block characteristics,
postoperative analgesia, level of sedation and overall
adverse effects. With approval of the Institutional Ethical
Committee of Faculty of medicine, Ain-Shams University,
Egypt, and after patients’ written consent, sixty ASA
physical status I-II aged 20 to 60 years scheduled for lower
limb orthopedic surgeries with expected duration of 90-120
min under spinal anesthesia were enrolled in this
prospective randomized comparative study. Patients were
excluded from the study if there was a patient refusal,
history of cardiac, liver, or kidney disease, history of
allergy to amide local anesthetics or medications included
in the study, presence of any neurological problem, and any
contraindication for regional anesthesia, failed or
unsatisfactory spinal block.
All patients were randomly assigned using computer
generated randomized code into three groups. group I
patients received intrathecally 15 mg in 3.0 ml hyperbaric
Bupivacaine with 5.0 μg in 0.5 ml Dexmedetomidine
followed by infusion of intravenous normal saline bolus
and maintenance volume equivalent to other groups
throughout the whole period of surgery. group II patients received intrathecal hyperbaric Bupivacaine 15 mg in 3.0
ml with normal saline 0.5 ml, followed by intravenous
bolus dose of Dexmedetomidine 0.5 μg /kg over 10 minutes
and intravenous normal saline bolus and maintenance
volume equivalent to other groups. group III patients
received intrathecal hyperbaric Bupivacaine 15 min 3.0 ml
with normal saline 0.5 ml followed by intravenous normal
saline bolus and maintenance volume equivalent to other
groups. After careful sterilization, spinal anesthesia was
carried out by 25 gauge Quincke spinal needle after skin
infiltration with lidocaine local anesthetic in L3-L4 level.
Assessment parameters included: vital signs (Heart rate,
systolic and mean blood pressure, arterial oxygen
saturation).
Assessment of sensory block included recording
Time to reach T6 level, Peak sensory level and its time and
regression time to S1. Assessment of motor block included
recording the time to reach Bromage 3 motor block before
surgery and the regression time to Bromage 0 after surgery.
Assessment of pain intraoperatively and in PACU was
assessed for 12 hours using visual analogue pain scale
(VAS) between 0-10 (0= no pain, 10 = the most severe
pain). Analgesics were given when VAS score >4 with
recording of time for first analgesic request and total
analgesic consumption.
Assessment of sedation intraoperatively and in
PACU was done by using Ramsay sedation scale.
Occurrence of any side effects as nausea, vomiting, headache, itching, shivering, respiratory, or cardiovascular
events, were recorded.
Study results were as following:
The patient groups were comparable as regarding
age, sex, weight, height, type of surgery, and ASA physical
status with no statistical significance. Systolic and mean
blood pressure values were lower in group II than group I
and III during the first 90 minutes of surgery. Similarly,
Heart rate values were statistically significantly lower in
group II than group I and group III during the first 60
minutes of surgery.
Intrathecal dexmedetomidine was superior to the
intravenous route as regard bupivacaine spinal block
characteristics. group I had earlier sensory onset to T6
dermatome, higher peak sensory level, prolonged sensory
regression time to S1 dermatome, lower mean 12 hours
VAS scale, longer time to first analgesic request, less total
analgesic consumption than group II and group III. The
regression time to Bromage 0 was prolonged in the
intrathecal group. However, intravenous dexmedetomidine
was superior in providing better intra-operative sedation
level but this advantage was only limited to the operative
time, and both routes provided comparable sedation level in
the postoperative period. We conclude from our study
results that both intrathecal and intravenous
dexmedetomidine were safe adjuvants to bupivacaine
spinal anesthesia.Intrathecal dexmedetomidine is superior adjuvant to
spinal bupivacaine when compared to intravenous
dexmedetomidine. It provides more stable hemodynamics,
greater augmentation to sensory and motor block, better
quality of perioperative analgesia and lesser overall side
effects. Intravenous dexmedetomidine provides higher level
of sedation during the intra-operative period.