Duration of Leg Nerve Blocks With Dexamethasone Added to Local Anesthetic

This is a double blinded randomized controlled trial on the effect on duration of action
when we add dexamethasone to our 3 routine peripheral nerve blocks (femoral, obturator and
sciatic nerve) for total knee replacement surgery.

Technique:

A computer generated randomization will determine if dexamethasone 8mg (2 cc of 4mg/cc)
will be given to the patient intravenously or mixed with the ropivacaine for the lower limb
blocks. A sham 2 ml of normal saline will be given in the other route. For example, if the
patient is assigned to the Ropivacaine + Dexamethasone Combination arm, 2 ml of
dexamethasone will be drawn up and labeled "PNB" (peripheral nerve block) by a person not
involved in the block or anesthetic management of the patient and given to the regional
anesthesiologist to add to their local anesthetic solution. Another 2 ml of normal saline
labeled (IV) will be drawn up by the same person and the sham will be given to the
anesthesia team taking care of the patient during surgery for them to give it to the patient
intravenously just before the start of the surgery.

Alternatively, if the patient is assigned to the Ropivacaine-Only Block arm, a person not
involved in the patient care will draw up 2 ml of normal saline and label it "PNB" and give
it to the regional anesthesiologist and 2ml of dexamethasone and label it "IV" to the
anesthesia team taking care of the patient during surgery for them to give it to the patient
intravenously just before the start of surgery.

Randomization:

70 patients will be randomly selected to receive either:

1. Combo A = 38 cc of 0.5% Ropivacaine with 2 cc of 4mg/cc Dexamethasone in the lower
limb blocks PLUS 2cc normal saline intravenously. 15 cc of solution will be used for
the femoral block, 20 cc for the popliteal block and 5 cc will be used for the
obturator block.

2. Combo B = 38 cc of 0.5% Ropivacaine with 2 cc of saline in the lower limb block PLUS
2cc of 4mg/cc of Dexamethasone intravenously. 15 cc of solution will be used for the
femoral block, 20 cc for the popliteal block and 5 cc will be used for the obturator
block.

Blinding:

A sealed envelope will be given to an anesthesia provider not involved in the peripheral
nerve block, follow up assessment of the block or provide perioperative anesthesia care to
the patient. This person would draw up 2 cc of dexamethasone and 2 cc of normal saline and
label them for intravenous (IV) injection or addition to the ropivacaine mixture in the
lower limb block (PNB) depending on the instructions in the envelope.

The anesthesia provider performing the peripheral nerve block, providing perioperative
anesthesia care including the general anesthesia or monitored anesthesia care nor the
anesthesia providers assessing the patients block will not have information regarding the
route of dexamethasone given.

Block performance:

All blocks are to be performed by 1 of our 7 regional anesthesiologists with expertise in
ultrasound-guided lower limb blocks who will be blinded to the presence of dexamethasone to
the local anesthetic. Blinding the performer will help to eliminate performance bias. Two
20 cc syringes of 0.5% ropivacaine will be prepared for the block. One cc of the study drug
will be injected into each syringe and mixed.

Before nerve blockade, all patients will receive intravenous access and standard monitoring,
which included noninvasive blood pressure, electrocardiogram, and pulse oximetry.

Sedation and anxiolysis are achieved with intravenously administered midazolam in 1- to
2-mg increments up to 5 mg and fentanyl in 25 ug increments as needed up to 250 ug.

POPLITEAL NERVE BLOCK

Popliteal nerve block will be performed with the patient lying supine and the operative leg
propped up on an elevation pillow allowing the posterior popliteal fossa to be accessed. A
linear, high-frequency US probe of 5 to 12 MHz (S-nerve, sonosite) covered with a sterile
dressing will be placed in the popliteal fossa in a transverse plane. The tibial and common
peroneal nerve are identified superficial and lateral to the popliteal vessels then traced
cephalad until they unite. This is the point of needle placement.

After sterilization and application of LA (3ml of 0.5% lidocaine) to the skin, a 22-gauge,
Tuohy is advanced through the skin at the lateral border thigh in alignment with the long
axis of the ultrasound probe in the same plane as the US beam (ie, in-plane technique). The
needle is to be positioned under US guidance to the tibial nerve and common peroneal nerve.

The needle is to be always visualized before LA injection. Hydrolocation or dissection
beyond 3 cc is not to be used to avoid dilution effect. Once needle position was
satisfactory and after negative aspiration, 10 mL of LA is to be injected incrementally over
2 minutes with direct sonographic visualization of the LA spread around the tibial nerve.
The needle is to be repositioned under US guidance to ensure adequate spread of LA around
the tibial nerve. A circumferential spread of the LA is sought. Extra care is taken never to
inject within the nerve. Expansion and compartmentalization of the nerve structure will
result in abandonment of the study. Similarly, 10 ml of LA is injected circumferentially
around the common peroneal nerve.

FEMORAL NERVE BLOCK

1. A femoral nerve block is placed in the usual manner of our institutional practice.
Femoral nerve block will be performed with the patient lying supine. A linear,
high-frequency US probe of 5 to 12 MHz (S-nerve, sonosite) covered with a sterile
dressing will be placed on the inguinal crease in a transverse plane. The femoral
artery is identified and traced cephalad until the profundus branch joins the femoral
artery proper. This is the level of needle placement.

2. After sterilization and application of LA (3ml of 1% lidocaine) to the skin, a
19-gauge, Tuohy is advanced through the skin at the lateral border of the upper thigh
in alignment with the long axis of the ultrasound probe in the same plane as the US
beam (ie, in-plane technique). The needle is to be positioned under US guidance to the
lateral and anterior portion of the femoral nerve.

3. The needle is to be always visualized before LA injection. No more than 3cc of
hydrolocation or hydrodissection is allowed. Once needle position was satisfactory and
after negative aspiration, a 20 mL syringe containing 20 mL of LA where 10mL is to be
injected incrementally over 3 minutes with direct sonographic visualization of the LA
spread. The needle is to be repositioned under the femoral nerve US guidance to ensure
adequate spread of LA above the nerves using the remaining 5 mL of LA. A
circumferential spread of the LA is sought. Extra care is taken never to inject within
the nerve.

OBTURATOR NERVE BLOCK The single shot obturator nerve block is performed with the patient
lying supine with the leg slightly abducted and flexed at the hip joint. The same ultrasound
probe is used and positioned more medially to locate the fascial plane between the adductor
brevis and adductor magnus where the posterior division of the obturator nerve lies. After
local infiltration of the skin with 3cc of 1% lidocaine, a 22 G Tuohy needle is advanced in
plane with until it lies within the fascial plane of the adductor magnus and adductor
brevis. No more than 3 cc of hydrolocation or hydrodissection is allowed. 5 cc of
ropivacaine is injected here taking care that hydrodissection of the fascial plane occurs
and avoiding intramuscular injection.

INTRAOP General anesthesia is performed in the usual fashion. Fentanyl is used
intraoperatively if the heart rate or blood pressure deviated greater than 20% from the
baseline if deemed appropriate. No other opioid or analgesics (such as ketorolac or
ketamine) will be given as per institutional practice. If there is suspicion that the
blocks are not working intraoperatively, the patient may be withdrawn from the study and
alternative analgesia may be given. The dexamethasone or sham is given at the beginning of
the surgery and ondansetron 4 mg is given at the end of surgery.

POST-ANESTHESIA CARE UNIT In PACU, the patient is evaluated for femoral, sciatic and
obturator block success. If any of the 3 blocks are deemed non functional, the patient is
withdrawn from the study and noted.

The patient will be given hydromorphone 0.2mg IV boluses in PACU to maintain the VAS score
below 4 if necessary. The standard institutional hydromorphone PCA set at 0.2mg bolus every
10 minutes with no basal.

At the time of discharge from PACU, the patients are given a diary to record their
perception of sensation and movement every awake hour on a scale of 0 to 2. Zero being no
sensation, 1 = some sensation and 2 being full sensation being recorded separately on top of
the foot and on the bottom of the foot. Similarly a 0 to 2 scale for strength. 0 being no
movement, 1= some movement, 2 = full strength in pointing the toes towards the nose and in
pointing the toes away from the nose.

Patients will also be given instructions to record the location of their pain when it first
returns and each time they require pain medications; being on top or at the bottom of the
knee.

FOLLOW UP All patients will be be seen the day after the surgery for their time to first
return of sensation and time to first return of movement. Also information regarding the
full return of sensation and time to full return of movement is obtained. If sensory and
motor function remains intact, a further interview will be conducted daily until full
sensory and motor function returns. All complications will be noted.

All patients will have their PCA and medication records checked for the time of their first
request for analgesia. Patients will be interviewed on the location of their pain for this
request for analgesia if the patient's pain location record is ambiguous.

Inclusion Criteria:

- American Society of Anesthesiologists physical status I to III,

- Aged 18 and above,

- Undergoing total knee replacement.

Exclusion Criteria:

- Body mass index of more than 45 kg/m2 (higher chance of failure)

- Weight less than 70 kg

- Diabetes

- Injection site deformities

- Infection at the injection site

- Existing peripheral neuropathy

- Allergy to LA agents

- Contraindications to dexamethasone

- Patients with severe PONV

- Patients with peptic ulceration or upper GI bleed of unknown origin

- Coagulopathy

- Any other contraindication to lower limb peripheral nerve block