Does preperitoneal local anesthesia in laparoscopic gastric bypass surgery reduce postoperative pain and opioid consumption?

Bariatric surgery for morbid obesity is a fast growing area of surgery in
western counties (1). In our hospital bariatric surgery is performed 800-900
times a year. Laparoscopic bariatric surgery induces less postoperative pain
than open bariatric surgery (2), but opioids are still necessary for optimal
analgesia. The reduction of opioid consumption and quick mobilisation is
especially important in obese patients. Obstructive sleep apnea syndrome is
often found in these patients and this is an important riskfactor for
hypoventilation after use of opioids (3).
Recently we have changed our protocol for bariatric surgery from our *common
practice* (CP) anesthesia to the modified Fast-track (FT) protocol. This
protocol is based on the Fast-track protocol, as described by Bergland et
al(1). We expected this protocol would lead to a reduction in postoperative
pain and opioid consumption.
In a retrospective study (unpublished data) we compared 100 patients of our CP
protocol with 60 patients from the FT protocol. The main changes made in the
analgesic part of the protocol were the change from long-acting analgesics,
morfine and during surgery sufentanil, to short- and ultrashort-acting
analgesics, sufentanil at induction and remifentanil during surgery, combined
with preperitoneal infiltration of bupivacaine 0.5%. Both groups were given
paracetamol 1 gram during surgery, which was continued after surgery 4 times a
day. After surgery the CP-group was given patient controlled analgesia (PCA)
with morfine. The FT-group got subcutanous morfine on demand.
We compared these two groups on opioid consumption and numeric rating scale
(NRS) for pain after surgery. This evaluation shows a significant reduction in
opioid consumption of 19mg (SD+/-15mg) to 7.3mg (SD+/- 7,5mg) of morfine in the
first 24 hours after surgery. In the CP-group 95% of the patients needed
opioids after surgery compared to 65% of the patients in the FT-group.
NRS-scores in both groups are similar. Our hypothesis is that this effect comes
from preperitoneal infiltration with bupivacaine, since our short- and
ultrashort working analgesics will be completely eliminated from the body
within approximately 10 minutes after surgery.
However, we can not conclude from this retrospective study that preperitoneal
infiltration with local anesthetics have an opioid-sparing effect. Also several
other factors have changed. Surgical technique has changed leading to less
tissue damage. Also we now have a very dedicated team of doctors and nurses
taking care of this specific group of patients. Another very important change
is our change from PCA-analgesia to on demand analgesia, which may affect
opioid consumption as well(4).
No studies have been done researching preperitoneal infiltration with a local
anesthetic in morbidly obese patients undergoing laparoscopic gastric bypass
surgery. One study has researched a combined preemptive and preventive
analgesia in open gastric bypass surgeries. This study shows a combination of
preoperative intravenous ketorolac, subcutaneous bupivacaine along the planned
incision and bupivacaine in the rectus fascia before closing leads to a
reduction in postoperative analgesics.(5)
Several studies have been done in other surgeries researching preperitoneal
local anesthetics. These studies show oppsite results. Bar-Dayan et al found
preperitoneal bupivacaine attenuates pain following laparoscopic inguinal
hernia repair, while Dean et al found no significant effect on pain. (6,7)
Studies researching continuous infusion of local anesthetics after abdominal
surgery show a reduction in pain, use of other analgesics and an accelerated
postoperative recovery. (8,9)
Three studies have been done researching intraperitoneal local
anesthetics.(10,11,12) A meta-analysis of these studies shows evidence in
favour of intraperitoneal local anesthetics for reduction of pain and opioid
consumption.(13)
Because no studies about this subject have been done and our retrospective
study shows inconclusive but promising results, a double-blind randomized
clinical trial is needed to compare the effect of preperitoneal infiltration
with bupivacaine with a placebo.

Primary objective:
To evaluate the postoperative opioid consumption and pain after laparoscopic
bariatric surgery. Our hypothesis is that less opioids will be consumed by
patients in the group receiving local anesthetics compared to normal saline.

Secondary objectives:
To evaluate side-effects from opioids, mobilisation, length of hospitalstay and
patientsatisfaction with pain treatment. Our hypothosis is that in our
treatment group we will less side-effect from opioids. We expect to see that
mobilisation within two hours after surgery will be possible for more patients
in our treatment group, length of hospitalstay will be shorter and
patientsatisfaction with pain treatment will improve.

This is a double-blind, randomized controlled clinical trial.

This study will have two groups:
1) Preperitoneal infiltration with bupivacaine 0.5%
2) Preperitoneal infiltration with normal saline 0.9%

Postoperatively, the groups will be followed, pain scores are recorded and
opioidconsumptie will be checked.

Local infiltration with bupivacaine 0.5% 30-40 ml or normal saline 0.9%

Additional risks are minor. Bupivacaine is a local anesthetic used in daily
practice and complications are rarely seen.
The burden of this study is minimal. No extra visits or blood samples need to
taken. Patients will have to fill in the use of postoperative analgesics and
their painscores will be asked every 6 hours. The day after surgery patients
will be asked if they were satisfied with paintreatment.