The Addition of Clonidine to 0.2% Ropivacaine for Wound Instillation After Minor Lower Abdominal Surgery in Children

The optimal method of controlling postoperative pain in children undergoing hernia repair would effectively relieve pain for extended periods of time and have no adverse effects. Unfortunately, such an ideal technique does not exist.

The control of postoperative pediatric pain after hernia repair is achieved with a combination of oral and intravenous pain medications and "nerve blocks". "Nerve blocks" are achieved by injecting local anesthetics or what is commonly referred to as "freezing "next to the nerve supply of the wound. "Freezing" the major nerves supplying sensation at the site of hernia repair in children, while they are asleep, is effective. At CHEO, this technique in addition to administering ketorolac, a liquid intravenous form of an anti-inflammatory agent similar to Advil, is the current technique of choice for postoperative pain control after inguinal hernia.

It is not unusual for these patients to require extra pain medications postoperatively. Available means of pain control in addition to those mentioned above include codeine-like medications, Tylenol, Advil-like medications and opioids administered intravenously. The addition of these medications increases the risk of suffering from side effects including respiratory depression, nausea and vomiting, and itching.

Ideally, the prolongation of postoperative pain relief by the addition of a second medication to the "freezing" during the nerve block would limit the need for additional pain medication and hence, decrease their associated side effects. Clonidine has the potential to be such a medication. It has been shown to provide pain relief by affecting several areas of the nervous system including the brain, the spinal cord and nerves. Clonidine prolongs pain relief of certain local anesthetics when used in nerve blocks for adults. Unfortunately, there are no studies that have examined the combination of clonidine and the local anesthetic ropivacaine for nerve blocks in children. Presently, the injectable form of clonidine is not marketed and is considered investigational in Canada.

The current study will be a prospective double -blind, randomized, controlled trial. It will compare the effects on postoperative pain relief of "freezing" (ropivacaine 0.2 %) alone and in combination with clonidine for a nerve block in children undergoing hernia repair. In addition, it will measure changes in the child's level of sedation, breathing, heart rate, blood pressure and any complications. Finally, it will assess how satisfied the parents are with this technique.

The researchers anticipate that the addition of clonidine to "freezing" will result in prolongation of postoperative pain relief in children undergoing hernia repair compared to "freezing" used alone.

Inclusion criteria

• Unilateral inguinal hernia or hydrocele
• 1 to 12 years old
• American Society of Anesthesiology classification I-II
• Written informed consent

Exclusion criteria

• Exclusion to nerve block
• Clotting disorder
• Infection
• Known allergy to clonidine or ropivacaine
• History of chronic, therapeutic administration of analgesics
• Receiving medications for attention deficit hyperactivity disorder
• Patients taking oral clonidine
• Undergoing bilateral hernia repair
• Morbid obesity