Key points

Introduction

Pain management after spinal deformity correction surgery for scoliosis in the pediatric population can be difficult due to the magnitude of the procedure. Deformity correction with posterior spinal fusion, with or without anterior procedures, causes significant tissue trauma that can result in debilitating pain. Historically, pain control has been achieved with intravenous (IV) opiates through patient-controlled anesthesia (PCA) or through IV push methods administered by nursing staff. Opiates provide excellent analgesic effect; however, the consequences of using opiates alone may include inadequate analgesia, nausea, vomiting, constipation, urinary retention, somnolence, respiratory depression, and possibly longer hospital stays, or even opiate dependence. In adult total joint arthroplasty, multimodal pain control has become an increasingly common method to achieve pain control without these sequelae. Recently, the same techniques have been studied in pediatric spinal deformity correction surgery as well. The purpose of this article is to outline the state of pain management in pediatric spine patients, including the use of multimodal management and to evaluate where further advances can be made.

Introduction

Pain management after spinal deformity correction surgery for scoliosis in the pediatric population can be difficult due to the magnitude of the procedure. Deformity correction with posterior spinal fusion, with or without anterior procedures, causes significant tissue trauma that can result in debilitating pain. Historically, pain control has been achieved with intravenous (IV) opiates through patient-controlled anesthesia (PCA) or through IV push methods administered by nursing staff. Opiates provide excellent analgesic effect; however, the consequences of using opiates alone may include inadequate analgesia, nausea, vomiting, constipation, urinary retention, somnolence, respiratory depression, and possibly longer hospital stays, or even opiate dependence. In adult total joint arthroplasty, multimodal pain control has become an increasingly common method to achieve pain control without these sequelae. Recently, the same techniques have been studied in pediatric spinal deformity correction surgery as well. The purpose of this article is to outline the state of pain management in pediatric spine patients, including the use of multimodal management and to evaluate where further advances can be made.

Opiates

Opiates are the mainstay of treatment for postoperative pain in many pediatric procedures, especially those in which the patient or surgeon expects significant postoperative pain. Opiates act on receptors in the brain, spinal cord, and peripheral tissues. There are several types of opiate-based pain medications that vary in their potency and duration of action. Opiates can be given in multiple different modalities including, but not limited to, orally, intravenously, by a patient-controlled anesthesia (PCA) device, an epidural injection, or intrathecal administration. Most patients are treated in the immediate postoperative period with IV or PCA methods and transitioned to oral-based intake, but adverse effects may limit the dose of opiates a patient can receive. Opiate administration also may prolong hospital stay if adverse effects require treatment or if the patient is unable to mobilize and participate in physical therapy. Despite this, opiates remain an effective analgesic, and they are used as the mainstay of treatment because of their potent analgesic properties. Tolerance to opiates can develop relatively quickly, with some medications more likely than others to cause this.

Acute opiate tolerance has been reported with the use of the medication remifentanil. Remifentanil is an opiate frequently used by anesthesia providers during spinal deformity surgery because of its potency, short duration of action, and lack of interference with neuromonitoring; however, it has been shown to cause acute opioid tolerance, leading to 30% higher opiate requirements in the postoperative period. It is believed that opiate-related adverse events may be related to the total dose given. Minor adverse events, including vomiting, pruritus, and constipation, are common and occur in approximately 40%, 20% to 60%, and 15% to 90% of patients, respectively. More severe adverse events such as respiratory depression occur much less frequently; in 1 review, the rate of respiratory depression was identified as 0.0013%.

Nonsteroidal anti-inflammatory drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a group of medications whose primary mechanism of action is inhibition of the enzyme cyclooxygenase (COX). This leads to a decrease in the production of prostaglandins, which are involved in the inflammatory response. NSAIDs have been demonstrated to provide good analgesia while decreasing postoperative opiate use after posterior spinal fusion in pediatric scoliosis surgery. This may lead to a decrease in opiate-related adverse effects. It has been shown that NSAIDs decrease the number of hospital days patients require PCA use and also decrease the likelihood of prolonged hospital length of stay, defined as 4 days or more in a scoliosis database review by Rosenberg. The concern with the use of NSAIDs is that they have gastrointestinal (GI) and renal adverse effects and have been linked to delayed bone healing in animal models. This has been corroborated in certain adult populations. Sucato and colleagues compared patients who received ketorolac and those who did not after posterior spinal fusion for adolescent idiopathic scoliosis. An overall pseudarthrosis rate of 2.5% was found, but ketorolac did not increase the likelihood of pseudarthrosis. There is also a concern about the effects of NSAIDs on platelet function by inhibiting formation of thromboxane A2; however, bleeding-related adverse events such as increased likelihood of transfusion or increased reoperation rates have not been associated with the use of ketorolac when given in the postoperative period.

Other analgesics

Other medications

Other medications have been used in treating postoperative pain after scoliosis surgery. Ketamine has been used in many ways, including a low-dose infusion for 72 hours; however, this did not affect pain scores or opiate consumption. Benzodiazepines such as diazepam and muscle relaxants such as cyclobenzaprine frequently are given postoperatively to help with muscle spasm after surgery. Although there is little evidence to support their use, they are routinely given. Finally, local anesthetics such as lidocaine and bupivacaine can be placed around the surgical wound to help with local pain control or they may be used as part of a continuous infusion into the wound via a pump. One study showed that a continuous infusion of 0.25% bupivacaine at a rate of 4 mL/h decreased opiate use by 38% on postoperative day 1. After postoperative day 1, opiate use was similar. However, the study did not compare continuous local anesthetic infusion to a single injection of local anesthetic to the wound at the time of closure.

Regional anesthesia

Epidural analgesia has been given in many forms for pain control after pediatric scoliosis surgery. An epidural provides excellent pain control and can be placed by the surgeon intraoperatively. It is important to note that local anesthetics used in the epidural regimen may make neurologic examination after surgery difficult and may mask an underlying neurologic injury. This can be avoided by dosing the epidural to start after completion of a detailed postoperative neurologic examination. Continuous epidural anesthesia has been shown to lead to improved pain scores and decreased opiate use when compared with PCA, with decreased systemic side effects including nausea, constipation, and urinary retention. An epidural catheter is even safe to use when the epidural space is exposed by Smith-Petersen osteotomies or when sublaminar cables are used. Epidural catheters, however, have a relatively high failure rate of 8% to 37%. Turner and colleagues injected radiopaque dye into the epidural catheter before routine postoperative chest radiographs were taken and found that 5 of 14 patients (35%) had inadequate pain control, and no dye was seen in the epidural space. Two of the 14 patients (14%) had dye in the paravertebral gutters, but had adequate pain control. The remaining patients had dye in the epidural space and had adequate pain control. The use of 2 catheters has been shown to decrease the failure rate and provide superior analgesia. The epidural catheter has the potential to migrate in the spinal canal as well, with 32% migrating 1 segment and 8% migrating 2 segments. The clinical significance of this is unknown, but if migration occurs outward, it may lead to inadequate analgesia. If the migration is inward, there is a potential for infection or neurologic injury; this was not observed in this study, which looked solely at migration.

Intrathecal administration of opiates is another option for regional anesthesia. This can be done preoperatively or by the surgeon directly injecting the dura. Intrathecal morphine has been shown to provide 12 to 36 hours of analgesia and lead to decreased IV opiate requirements and improved pain scores compared with PCA. There is also a correlation between intrathecal morphine use and decreased blood loss in pediatric spinal fusion surgery for scoliosis. The exact mechanism is unknown, but it is thought to be related to a lower mean arterial pressure (MAP) ; however, another study showed an intrathecal dose-independent decrease in blood loss that was not associated with a lower MAP. A concern with the use of intrathecal opiates is that the medication can migrate in the cerebrospinal fluid to the brainstem and potentially increase the risk of adverse effects. Although it has been shown that intrathecal opiates increase the risk of pruritus, as does epidural administration, other adverse effects such as nausea, vomiting, constipation, and respiratory depression are not increased with intrathecal opiates. Intrathecal opiates are safe and provide a powerful adjunct for pain control in the first 12 to 36 hours after deformity correction surgery for scoliosis.