Serum Ropivacaine Concentrations in Pediatric Patients Receiving Continuous Wound Catheter Analgesia

There have been numerous investigations of serum concentration of ropivicaine using wound
catheters in adults. These studies have revealed that wound catheters provide effective
analgesia without toxic levels of serum ropivicaine. Our current proposal is different for
two reasons. One, the investigators will be investigating the serum levels of ropivacaine in
pediatric patients. There are currently no studies investigating the efficacy of this
technique in the pediatric population. Two, the wound catheter currently being placed by Dr
Losee (and plastic surgeons in other pediatric centers) as part of standard of care is
different from other wound catheters. Most wound catheters described in the literature are
placed in the surgical wound between muscle and facial planes. The catheter placed by Dr
Losee for his routine postoperative pain control is placed adjacent to the periosteum and
adjacent to the bone harvest site. Dr Losee has been performing this technique as part of
standard patient care and it appears to provide excellent analgesia without side effects from
the ropivacaine. However, it is unknown what effect this location has on serum plasma levels
of ropivacaine. Measuring unbound ropivacaine will help define whether or not these wound
catheters maintain the serum ropivacaine levels below, near, or above toxic levels. Pediatric
studies have investigated the serum ropivacaine levels during epidural infusions and
peripheral nerve blocks. This local anesthetic is safe as long as the administration is
limited to weight based limits. For continuous infusions, ropivacaine should not be
administered at a greater rate than 0.4 -0.5 mg/kg/hr. The wound catheters for The Childrens
Hospital of Pittsburgh Plastic Surgery service are administered at 0.25 mg/kg/hr. Ropivacaine
is the local anesthetic of choice for many pediatric hospitals and for the Acute
Interventional Pediatric Pain Service at the Children's Hospital of Pittsburgh because it
appears to have a slight safety advantage over bupivacaine. Ropivacaine does not bind sodium
channels as avidly as bupivacaine and therefore may not be as cadiac toxic. However, the
location of the catheter can alter absorption and may alter plasma levels. Currently there is
no data for pediatric iliac crest wound catheters. Since this technique is already a standard
of care here at this center, we plan to measure serum ropivacaine levels to define these
values.

It is important to understand the dosages currently being used in this pediatric population
and the effects on serum local anesthetic levels. When local anesthetic is infused through an
epidural, peripheral nerve block, or wound catheter, there is an elevation in local
anesthetic plasma levels in the patient. The plasma levels depend on the dose, concentration
and location of the catheter. Current literature has defined the plasma levels obtained
during continuous infusions of local anesthetic through wound catheters in adults. Safe
infusion rates have been defined for adult catheters. This data does not exist for wound
catheters in pediatric patients and this study will begin to define these limits. In
particular, the catheter currently being placed as standard of care at The Children's
Hospital of Pittsburgh is periostial and it is unknown what effect this location has on serum
ropivacaine levels

Inclusion Criteria:

- Inclusion criteria is any patient age ranging from 5 to 18 years of age that is
scheduled for an iliac crest bone harvest that requires an iliac crest wound catheter

Exclusion Criteria:

- Patient or parent/guardian refusal

- Ropivacaine allergy