Adjuvants, Anesthesia Clinical Trial
Official title:
Efficacy of Neostigmine Versus Dexamethasone as Adjuvants to Lidocaine During Intravenous Local Anesthesia for Forearm Orthopedic Surgeries
Intravenous regional anesthesia (IVRA) is described firstly in 1908 by August Bier. It is
simple, safe, reliable, less cost, efficient method in forearm surgery. The advantage of this
method has fast return of motor and sensory function which enables patients for earlier
discharge. However, this method has disadvantages such as tourniquet pain, insufficient
muscle relaxation and postoperative analgesia.
Lidocaine inhibits action potential propagation within neuronal tissue by binding to
receptors in Na+ channels located on the nerve cell membrane. Lidocaine IVRA is safe and
effective and is associated with a rapid onset (4.5 minutes) of anesthesia after injection
and termination of analgesia (5.8 ± 0.5 minutes) once the tourniquet is deflated.
Neostigmine is a typical cholinesterase inhibitor. It increases the level of acetylcholine
(Ach) and indirectly stimulates both nicotinic and muscarinic receptors. In anesthesia,
neostigmine is a drug that has been used for reversal of residual neuromuscular block.
Administration of neostigmine by intrathecal and epidural routes has been found to cause
analgesia by inhibition of the breakdown of Ach in the spinal cord.
Dexamethasone is commonly used in anesthesia to prevent postoperative nausea and vomiting
(PONV). Two recent meta-analyses have documented that dexamethasone also reduced
postoperative pain and opioid requirement. Intravenous dexamethasone has also been shown to
improve postoperative pain control in patients receiving spinal or epidural morphine.
Hong et al reported that intravenous dexamethasone in combination with a caudal block with
ropivacaine prolonged the duration of postoperative analgesia without adverse effects in
children undergoing orchidopexy. So the investigators expect that addition of dexamethasone
or neostigmine will affect duration and postoperative analgesia in bier block.
This study will be a prospective clinical randomized controlled double-blind study using a
computer-generated randomization. Neither the doctor "investigator" nor the participant
"patient" will be aware of the group allocation or the drug used. The study drugs will be
prepared by one of the supervisor anesthesiologists (not included in the procedure,
observation or data collection).
The study will be carried out in Assiut University Hospital after approval from our local
ethical committee.
Patients
The patients will be classified in two groups:
According to sample size calculator. Group D: will include 30 patients and will receive
intravenous 3mg/kg lidocaine 2 % (diluted with normal saline to 40 ml) + 8 mg dexamethasone
for bier block.
Group N: will include 30 patients and will receive intravenous 3mg/kg lidocaine 2 % (diluted
with normal saline to 40 ml) + 0.5 mg neostigmine for bier block.
Methods
Before the procedure, the patient should be:
- Starved for 6-8 hours.
- Monitored closely (standard monitoring applied: HR, NIBP, SaO2 and RR)
- Adequately informed about the procedure and have consented to it.
The equipments required for IVRA include:
- Pneumatic tourniquet (checked for leaks before the procedure) and a pressure gauge.
- Esmarch bandage or Rhys-Davis exsanguination.
- Local anesthetic solution and the adjuvants.
- Resuscitation equipments and drugs.
Technique:
IVRA of the arm: a 22 G cannula is placed intravenously as distal as possible in the arm to
be anesthetized. Venous access is established in the opposite arm to allow administration of
fluids or other drugs if necessary. The double tourniquet (two tourniquets each 6 cm wide) or
a single one (14 cm wide) is applied on the operated arm with generous layers of padding,
ensuring that no wrinkles are formed and the tourniquet edges do not touch the skin.
The arm is exsanguinated either by using the Esmarch bandage or a Rhys-Davis exsanguinator.
If this is impossible, exsanguination can be achieved by elevating the arm for 2-3 minutes
while compressing the axillary artery. The distal tourniquet is inflated to at least 100 mm
Hg higher than the patient's systolic blood pressure (250 - 300 mmHg). The proximal
tourniquet is inflated to the same pressure.
After ensuring inflation, the distal cuff is deflated. Before injecting local anesthetic, it
must be confirmed that no radial pulse is palpable. The local anesthetic is then injected
slowly. A standard volume for injection into the upper limb is 40 ml, which can be increased
to 50 ml in a fit, large adult.
If the injection is too rapid, the venous pressure may exceed the tourniquet pressure and the
local anesthetic solution may escape into the systemic circulation. Surgical anesthesia is
usually achieved within 15 minutes. The distal tourniquet, which overlies part of the
anesthetized arm, can then be inflated and the proximal one deflated to relieve tourniquet
pain. The cuff should not be deflated until 20 minutes after local anesthetic injection
because systemic toxic doses of local anesthetic may occur.
Cuff deflation should be performed in cycles with deflation/inflation times of less than 10
seconds until the patient no longer exhibits signs of systemic toxicity (e.g. tingling of the
lips, tinnitus or drowsiness). Therefore, the patient should be monitored closely for 30
minutes following tourniquet release. So, the investigators expect that addition of
dexamethasone or neostigmine will affect duration and postoperative analgesia.
Data collection:
1. Patient's data: include patient's gender, age, weight, height, BMI and ASA
classification.
2. Preoperative data:
1. Basic Monitoring: heart rate (HR), non-invasive blood pressure (NIBP), arterial
oxygen saturation (SaO2), respiratory rate (RR) will be recorded.
2. Preoperative investigations: prothrombin time, prothrombin concentration and INR to
avoid any risk of internal bleeding.
3. Basal assessment of motor power and sensation of the limb:
1. Motor power: Motor block was evaluated by thumb abduction (radial nerve), thumb
adduction (ulnar nerve), thumb opposition (median nerve), and flexion at the elbow
(musculocutaneous nerve) on a 3-point scale for motor function (0: normal motor
function, 1: reduced motor strength but able to move fingers, 2: complete motor block).
2. Sensation: Sensory block (4 nerves) was assessed by ice packs using a 3-point scale: 0:
normal sensation, 1: loss of sensation of cold (analgesia), 2: loss of sensation of
touch (anesthesia).
d- The standard value of visual analogue scale will be set as the score during passive
exercise before the surgery.
3. Introperative data:
a- Basic Monitoring: heart rate (HR), non-invasive blood pressure (NIBP), arterial
oxygen saturation (SaO2), respiratory rate (RR) will be recorded every 10 minutes till
the end of surgery.
b- Sensory and motor block: Sensory and motor blocks will be evaluated every 5 minutes
until 20 minutes after injection.
Onset time will be defined as the time interval between the end of total local
anesthetic administration and complete sensory block. Complete sensory block will be
defined by anesthetic block (score 2) on all nerve territories.
Complete motor block will be defined as absence of voluntary movement on hand and
forearm (score 0).
c- Duration of surgery.
4. Postoperative data:
1. Duration of sensory and motor block:
Duration of sensory block will be defined as the time interval between the end of
local anesthetic administration and the complete resolution of anesthesia on all
nerves.
Duration of motor block will be defined as the time interval between the end of
local anesthetic administration and the recovery of complete motor function of the
hand and forearm.
2. Duration of analgesia: interval between onsets of the block to the time of the
first analgesic requirement.
3. Analgesia assessment:
Postoperatively, a Post-Anesthesia Care Unit (PACU) nurse will assess the quality
of analgesia. The pain score will be recorded using the Visual Analouge Scale (VAS)
2, 4, 6, 12 and 24 hours after surgery. Significant pain is defined as one that has
a score of ≥ 4 and as a consequence required a supplementary dose of analgesia.
Intravenous Paracetamol 15 mg/kg, will be administered and recorded.
4. Documentation of any complications: Includes local anesthetic toxicity & drug
additives complications.
Local anesthetic toxicity:
• Initial symptoms are subjective and include perioral tingling or numbness,
lightheadedness, tinnitus, metallic taste, slurred speech, auditory and visual
disturbances.
• Minor symptoms usually do not require treatment. If any of these occur observe
patient closely and identify any potential reasons for systemic toxicity eg: check
for cuff failure - re-inflate.
• Significant neurotoxicity: Objective signs are usually excitatory: twitching,
fasciculation and seizures:
- Check for cuff failure - re-inflate immediately
- Administer Midazolam 2.5-5.0 mg iv
- Support the ABC's as indicated Most seizures are self-limiting but can be
potentiated by hypoxia, acidosis and hypercarbia so these should be treated
aggressively.
• Significant cardiotoxicity: if occurs (eg: hypotension, bradycardia and
arrhythmias): Give oxygen and adopt an ACLS approach Check for cuff failure -
re-inflate immediately Bicarbonate may be indicated to address acidaemia.
Drug additives complications:
All patients will be monitored for any complications that may occur from any
adjuvant drugs used in the study and will be treated promptly.
Statistical analysis All data will be collected and analyzed using SPSS version 20
(SPSS, Inc., Chicago, Illinios, USA). Normally distributed data will be expressed
as mean ± standard deviation, range, numbers and percentages. A probability (p)
value of less than 0.05 will be considered statistically significant.
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