The Effect of Various Additives to Local
Anesthetics on the Duration of Analgesia of Supraclavicular Brachial Plexus Block
Mohyiedin Hassan*, Kamelia A Abaza, Ekram F Sayouh and Al Shaimaa A Kamel
Department of Anesthesia and Surgical Intensive Care, Zagazig University, Egypt
Submission: June 03, 2019; Published: June 20, 2019
*Corresponding author: Mohyiedin Hassan, Department of Anesthesia and Surgical Intensive Care, Zagazig University, Egypt
How to cite this article: Mohyiedin H, Kamelia A A, Ekram F S, Al Shaimaa A K. The Effect of Various Additives to Local Anesthetics on the Duration of
Analgesia of Supraclavicular Brachial Plexus Block. J Anest & Inten Care Med. 2019; 9(2): 555756. DOI: 10.19080/JAICM.2019.09.555756
Background: We compared the effect of adding Dexmedetomidine, Magnesium Sulphate or Ketamine to local anesthetics in ultrasound guided supraclavicular brachial plexus block. Duration of analgesia provided by the block is the primary outcome.
Patient and Methods: sixty patients posted for upper limb surgeries were enrolled for a comparative randomized prospective controlled clinical study. Patients were divided into four groups, the Dexmedetomidine group (D), the Magnesium group (M), the Ketamine group (K) and the Control group (C). In group D (n=15), that administered 24ml volume of local anesthetics (Lidocaine 2% + Bupivacaine 0.5% 1:1 mixture) +100mcg Dexmedetomidine in 1ml volume.; in group M (n= 15), administered 24ml volume of local anesthetics (Lidocaine 2%+Bupivicaine0.5% 1:1 mixture)+Magnesium Sulphate 100 mg in 1ml volume.; in group K (n=15), administered 24ml volume of local anesthetics (Lidocaine 2% +Bupivicaine0.5% 1:1 mixture)+ Ketamine 50mg in 1ml volume, while the control group (C) (n=15), administered 24ml volume of local anesthetics (Lidocaine 2% +Bupivicaine 0.5% 1:1 mixture)+1ml volume normal saline 0.9% NaCl. The time between the complete sensory block and the first analgesic requested by the patient was assessed.
Results: Demographic data and surgical characteristics were comparable in all groups. The D group showed delay in onset for first call for analgesia (900±60.9min) while M and K groups results were (600±33.4min) and (350±17.4min) respectively, all of the group’s results were statistically significant than the control group result (260±14.3min).
Conclusion: There was statistically significant increase in the duration of analgesia in all groups more than the control. Patients who received dexmedetomidine were the last to require analgesia, then magnesium followed by ketamine.
Local anesthetics alone for supraclavicular brachial plexus block provide good operative conditions but have shorter duration of postoperative analgesia. Hence, various adjuvants were added to local anesthetics in brachial plexus block to achieve quick, dense, and prolonged block .
Magnesium is one of the most plentiful cations in the body. Magnesium is necessary for the presynaptic release of acetylcholine from nerve endings and may produce effects like calcium-entry-blocking drugs. Anti-nociceptive effects of Magnesium are due to regulation of calcium influx into the cell and antagonism of the N-methyl D-aspartate (NMDA) receptors .
Dexmedetomidine is highly selective, specific and potent α2-adrenergic agonist having analgesic, sedative, antihypertensive, and anesthetic sparing effects when used in systemic route.
Adding Dexmedetomidine to local anesthetics during peripheral nerve blockade and regional anesthesia procedures may also prove efficacious for the surgical patients. Dexmedetomidine has also shown to prolong the duration of the block and post-operative analgesia when added to local anesthetic in various regional blocks .
Ketamine is a well-known anesthetic agent with potent local effect on peripheral nerves. This local effect of ketamine is most probably by blocking the voltage operated sodium channels. The effect of ketamine on (NMDA) antagonism abolishes peripheral afferent noxious stimulation .
After the approval of the Zagazig University Institutional Review Board, patients were explained about the drugs and the approach, and only those who gave wellful written informed consent were included in the study. ASA physical status I and II
patients, 18-60 years undergoing unilateral upper limb surgeries
below level of the shoulder under supraclavicular brachial plexus
block were enrolled in a randomized prospective controlled
Exclusion criteria were patients who refused to be included,
with peripheral neuropathy of the upper limb, infection at the
injection site, altered mental status or had history of allergy to
local anesthetics. Also excluded were patients with coagulopathy
or planned for receiving general anesthesia at the same operation
for any cause as (bone graft, skin graft, etc.) or main site of the
surgery is the medial side of the arm at axilla level (T2 distribution).
Assuming that mean + SD of duration of sensory block in
both Dexmedetomidine and Ketamine groups is (413.97+238.5
Vs 227+135 respectively) . So, sample size was calculated by
open Epi to be 60 cases in 4 groups (15 cases in each group) with
confidence level 95% and power of test is 80%. A computergenerated
randomization table divided patient into 4 equal
groups randomly allocated patients into four groups.
Dexmedetomidine group(D) (n=15) received 24ml volume of
local anesthetics (Lidocaine 2% + Bupivacaine 0.5% 1:1 mixture)
+100mcg Dexmedetomidine in 1ml volume.; Magnesium group M
(n=15), administer 24ml volume of local anesthetics (Lidocaine
2% +Bupivicaine 0.5% 1:1 mixture)+Magnesium Sulphate 100mg
in 1ml volume.; in group K (n=15), administered 24ml volume of
local anesthetics (Lidocaine 2% +Bupivicaine 0.5% 1:1 mixture)+
Ketamine 50mg in 1ml volume, while the control group (C)
(n=15), administered 24ml volume of local anesthetics (Lidocaine
2% +Bupivicaine 0.5% 1:1 mixture)+1 ml volume normal saline
0.9% NaCl. were given for supraclavicular brachial plexus block
using the ultrasound guidance.
In the operating room, an intravenous line was secured and
standard monitoring (Electrocardiography, Pulse Oximetry and
non-invasive blood pressure) were applied to all the patients.
The patients were administered brachial plexus block by
supraclavicular route with the patient in the proper position
(supine with the head tilted to the opposite site) (Figure 1),
the skin was disinfected and the US machine transducer was
positioned in the transverse plane immediately superior to
the clavicle at approximately its midpoint. The transducer was
manipulated to obtain a cross-sectional view of the subclavian
artery. The brachial plexus is seen as a collection of hypoechoic
oval structures lateral and superficial to the artery. The spread of
injected drug was observed in real time to achieve a satisfactory
spread of the drug around the brachial plexus (Figure 2).
Duration of analgesia (DOA): the time between the complete
sensory block and the first analgesic request by the patient
(complete sensory block was considered when there was complete
loss of sensation to pin prick at the dermatomes corresponding
to median nerve, radial nerve, ulnar nerve and muscle-cutaneous
nerve). Pain was assessed using the Visual Analogue Scale (VAS
score) after explaining it to the patient as an instrument used to
quantify a subjective experience, such as the intensity of pain. A
commonly used visual analog scale is a 10-cm line labelled with
“worst pain imaginable” on the right border and “no pain” on the
left border (Figure 2). The patient was instructed to make a mark
along the line to represent the intensity of pain currently being
experienced. AS score was assessed every hour in the first 4 hours
after the end of the operation then every 4 hours for 24 hour
and injection of 25mcg Fentanyl (rescue analgesic) was given
bolus (IV) when VAS ≥ 3. The data was compiled and subjected
to statistical analysis using Statistical Package for Social Sciences
(SPSS), version15.Demographic and hemodynamic data were subjected to
Student’s t-test and for statistical analysis of the duration of the
analgesia unpaired t-test was applied and reconfirmed with
the Wilcoxon W and Mann-Whitney U tests. P-value < 0.05 was
considered as statistically significant and P<0.001 as highly
The demographic data and ASA characteristics were
comparable in both groups (Table 1). Our results revealed that
there were highly statistically significant differences between
the studied groups as regarding timing of first requirement for
analgesia. The D group showed statistically significant delay in
onset for first call for analgesia (900±60.9min) than other groups.
M group also showed statistically significant delay in onset for
first call for analgesia (600±33.4min) than K group and C group.
K group showed statistically significant delay in onset for first call
for analgesia (350±17.4min) and then C group (260±14.3min)
T test: Independent sample t test,
NS: Non-significant difference (p>0.05),
Data is expressed as Mean±SD, Number (percentage).
**: Highly significant difference (P<0.001).
Data are expressed as mean + standard deviation.
This study was done to compare the effect of administration
additives (namely Dexmedetomidine , Magnesium sulphate and
ketamine) individually to local anesthetics mixture in US guided
supraclavicular brachial plexus block, it found that adding these
additives provide more longer duration of analgesia to the
patient in comparison to the control group .The superior effect
was to Dexmedetomidine then Magnesium Sulphate followed by
Besides its central-mediated analgesia , the mechanism
by which Dexmedetomidine enhances the quality of regional
anesthesia when used as an adjuvant to LAs can be explained by
two peripheral mechanisms [7-9]. The first is the vasoconstrictor
effect around the site of injection which leads to delay of the
absorption of the LAs and prolong the duration of the LAs effect.
The second mechanism is the direct action of Dexmedetomidine
on the activity of PN. Dexmedetomidine may inhibit the compound
action potentials that results in direct inhibition of the on-nerve
Previous studies had been investigated the use of Magnesium
sulfate as an adjuvant to LA solutions for PNB [10-12]. Analgesic
effects of Magnesium sulfate on the Peripheral Nerve (PN) may
be explained by the NMDA receptors antagonist effect that
causes prevention of central sensitization from peripheral
nociceptive stimulation, as well as Magnesium reduced release of
acetylcholine through the competitive block of the calcium entry
in presynaptic endings . Another possible mechanism for the
action of Magnesium sulfate on the PN is the surface charge theory
. The modulation of the external Magnesium concentration
bathing a nerve bundle can enhance the PNB caused by LAs, as
well as the high concentration of Magnesium attracted by the
negative charges of the outer membrane surface affected Na+
channel gating and could cause hyperpolarization which results
in inhibition of nerve conduction.
The effect of analgesia by ketamine is prolonged when
administered with the local anesthetic agents due to the higher
concentration of ketamine in the pre-neural fat than in the
systemic circulation. It exerts the effect on neuronal transmission
by blocking the Na+- K+ ion gates at the peripheral nerves .
The superiority of dex over Magnesium in our study is in
accordance with Elyazed & Mogahed  in their comparative
study between Magnesium Sulfate and Dexmedetomidine as an
Adjuvant to 0.5% Ropivacaine in Infraclavicular Brachial Plexus
Block . Also, our study`s results goes with Mohamed & Genidyin
 their study Magnesium sulphate versus Dexmedetomidine as
an adjuvant to local anesthetic mixture in peribulbar anesthesia
Consistent with the current study results also, Kassem et al.
 showed in a comparative study between Dexmedetomidine
and Magnesium addition to LA s, but for peribulbar block their
result also coincided with the superiority of Dexmedetomidine
over Magnesium. The onset of block was more rapid in the
dexmedetomidine group than the magnesium sulphate group .
Overall, these findings of dexmedetomidine are in accordance
with findings reported by Ammar & Mahmoud , Esmaoglu et
al.  & Gandhi et al. .
While our results for magnesium group concided with Reddy
et al.  & Mathur A & Singh LP  who attributed the prolonged
duration of analgesia either to reducing post synaptic activity
of slow conducting unmyelinated C‑fibers [20,21]. Regarding
ketamine the results come with Lashgarinia et al.  who in line
with the ideas of Tverskoy et al.  who showed found the longlasting
analgesic effect of ketamine on postoperative pain could
be explained by the effect of ketamine on the inhibition of central
There was statistically significant increase in the duration of
analgesia when adding additive to LAs mixture for supraclavicular
brachial plexus block in all groups more than the control. Patients
who received dexmedetomidine were the last to require analgesia,
then magnesium followed by ketamine.
Mohamed AZE, Genidy MM (2017) Magnesium sulphate versus Dexmedetomidine as an adjuvant to local anasthetic mixture in peribulbar anesthesia. Egyptian Journal of Anaesthesia 33(4): 375-380.
Kassem OAH, ELgarhy AMM, Salim MG (2018) Magnesium sulphate versus Dexmedetomidine as adjuvants for local anesthetics in peribulbar block for eye surgeries: Clinical comparative study. The Egyptian Journal of Hospital Medicine 72(4): 4308-4312.
Mathur A, Singh LP (2018) A comparative study to evaluate the effect of magnesium sulphate and normal saline as an adjuvant to 0.5% ropivacaine on sensory, motor and postoperative analgesia in supraclavicular brachial plexus blockade. Global Journal for Research Analysis 7(4): 57-59.