INTRODUCTION
In
our institution, most of the surgeries on upper limb ( hand, fore-arm and elbow)
are performed under brachial plexus blocks usually through supra-clavicular
approach using a mixture of 0.5% bupivacaine and 2 % lidocaine.
Bupivacaine is a racemic mixture of two
stereoenantiomers dextrobupivacaine and levobupivacaine and
provides long duration of action but its main disadvantage
is because of its central nervous system and cardiotoxic effects
In view of the above facts there is
a trend to switch over to safer alternative anaesthetic agents like
levo-bupivacaine and ropivacaine.
Levobupivacaine, an S-enantiomer of
bupivacaine has been reported to have a
longer duration of analgesic effect compared with ropivacaine when used for
spinal and epidural anesthesia] and has favorable clinical profile and lesser
cardiotoxicity when compared with racemic bupivacaine
Several
adjuvants such as dexmedetomidine (DMT),clonidine,
fentanyl, etc are used in combination with local anaesthetic agents to enhance their blocking potential, thereby decreasing the
time of onset of the block and increasing
the duration of the motor and sensory block. In this context, Alpha-2-adrenergic receptor (α2-AR) agonist, DMT is
emerging as the most popular adjuvant.
DMT is being safely
used as an adjuvant for subarachnoid blocks in urological surgeries,
orthopaedic procedures of lower limb and lower abdominal surgical procedures,[27]
We hypothesized that addition of DMT as
adjuvant to ropivacaine and levo-bupivacaine
can enhance the block characteristics by extending the duration of
analgesia into the post operative period. Accordingly we undertook the present
study to evaluate and compare the block characteristics of 0.5% bupivacaine,
0.5% levo-bupivacaine, 0.75% ropivacaine with dexmedetomidine added as adjuvant
versus 0.5% bupivacaine alone i.e.
without DMT added an adjuvant. In our study we added DMT in a dose of 0.5 µg/kg body weight to the local
anaesthetic agents used in the brachial plexus blocks performed through
supraclavicular approach.
METHOD
Institutional Ethical Committee approval was
obtained vide RC. No:GVPIHCMT/IEC/20201208/02 dated 08-12-2020 of Dean,
GVPIHCMT, Visakhapatnam Eighty adult patients of age 18 and 80 yrs of either sex with weight
betweeen 50 and 80kg and who were of
American Society of Anaesthesiologists (ASA) grade I and II, attending our
medical college hospital for surgeries of upper limb were enrolled in this
study, to be undertaken between the period 01-1-2021 and 31-08-2021. Written
Informed consent was obtained from all the participants after explaining in
detail about the study protocol and all consequent risks and benefits in their
mother tongue in the presence of two witnesses. Exclusion criteria adapted for
our study were patients with known allergy to study drugs, patient refusal of
local anaesthetic block, patients suffering from neurological disorders,
psychiatric disorders, mental retardation, uncontrolled hypertension and
diabetes mellitus, coagulation or bleeding abnormalities,pregnant women and
lactating mothers, patients on adrenergic agonist/antagonist medications and infection
at the site of the block.
Patients were
randomly allocated to four groups of 20 each (n=20) by utilizing
computer generated random grouping software: group B, group L, group R and group
C and a
sequentially numbered sealed opaque envelope method was utilized for allocating the individual patient to the respective study
group. The anaesthetic drug mixture for the brachial plexus block was prepared as per given schedule below by an
anaesthesiologist who was further excluded from participating in patient
assessment.
Patients of
group B (n=20) were given 30 ml of 0.5% bupivacaine plus 0.5 µg/Kg body weight of DMT; Patients of group L
(n=20) were given 30 ml of 0.5% levo-bupivacaine plus 0.5 µg/Kg body weight of DMT; patients of group R
(n=20) were given 30 ml of 0.75% ropivacaine plus 0.5 µg/Kg body weight of DMT and patients of group C (n=20, ) were
given 30 ml of 0.5% bupivacaine alone
and this group served as control arm for our study.
The primary outcome variables
studied were the differences in the duration of the analgesia and the duration
of motor and sensory block. The secondary outcome variables studied was
were the differences in the duration of onset of the motor and sensory block, fluctuations in haemodynamic variables like heart rate (HR), mean arterial pressure
(MAP),respiratory rate( RR) and arterial oxygen saturation (SaO2), total dose of rescue analgesics administered
during the 1st 24 hours of post operative period, Ramsay sedation score, surgeon assessment score and patient satisfaction score and any
adverse events and drug-related side effects.
Brachial plexus block was performed through supraclavicular approach by an experienced anaesthesiologist
different from the one assessing the patient intra‑ and post‑operatively
and collecting the data for analysis.
Sensory and motor block blockade was
assessed every 2 min intervals for the initial 30 min. Sensory block was tested by a pinprick sensation using a 23‑G needle in
entire dermatomes innervated by median , radial , ulnar and musculo cutaneous nerves. Onset of sensory
block was considered when there was a dull sensation to pin prick along the
distribution of any of these nerves. Complete sensory block was considered when
there was a complete loss of sensation to pin prick. Degree of sensory block was
graded as[29] Grade: 0 when
sharp sensation of pin prick is felt,
Grade: 1, if analgesia and dull sensation is felt and Grade: 2 when fully anaesthetised and no sensation is felt.
The duration of sensory block was defined as the time interval between the onset
of sensory anaesthesia and the complete resolution of anaesthesia on all
the nerve territories. The duration of
motor block was defined as the time interval between the onset of motor block
and the recovery of complete motor function of the hand and forearm.
Postoperatively,
the patients were transferred to the recovery room for further monitoring. Pain
was assessed by VNRS at every 30 min for 6 h, and then at every 1 hour till
the patients complain of pain (VNRS >3). Patients were
enquired regarding their satisfaction level about the anaesthetic experience on
a 3 point patient assessment score.[32] (score 1= extremely
dissatisfied -had severe pain and or other adverse events; score 2 = satisfied-
had minimal pain only; score = 3 extremely satisfied, no pain or adverse events
and comfortable during block and surgery).
Power analysis and
sample size calculation were based on a
population standard deviation of one with respect to the duration of the
sensory block derived from the
results of previous studies. With 80% power and 5% alpha error to detect
a difference in duration of the sensory block of one hour between groups, a
sample size of 15 patients per group was required. We included 20 patients in
each group for better validation of results and to compensate for any dropouts
in the middle of the study due to incomplete blocks. At
the end of the study, all the data were compiled using Microsoft excel
programme and the quantitative variables (parametric data) were presented as mean ± SD and ordinal /
nominal/categorical data (non parametric data) were presented as number and
percentage. The
differences between the groups were analysed using ANOVA, Variance ratio
test and an appropriate Post Hoc test for comparison between the
groups whenever required. Chi square test was used for non parametric data. Statistical
analysis was carried out using Microsoft
Windows Excel 2007 and SPSS version 20.0 IBM and a P value of ≤ 0.05 was considered as statistically significant. |