Pain Following Spinal Surgery

Nonsteroidal Antiinflammatory Drugs

Nonsteroidal antiinflammatory drugs (NSAIDs) block the inflammatory mediators by acting on the cyclooxygenase (COX) enzyme, reducing the postoperative pain, and facilitating an early ambulation. Jirarattanaphochai and Jung conducted a metaanalysis comprising of 17 studies and found that patients receiving a combination of NSAIDs and opioids had lower pain scores than the group receiving opioids alone. NSAIDs may be administered either orally (diclofenac sodium, ibuprofen, mefenamic acid) or intravenously (diclofenac or ketorolac). It has been found that ketorolac, when used with parenteral narcotics, is more effective than parenteral narcotics alone for postoperative pain following lumbar disc surgery. This combination has been found to contribute to an early discharge from the hospital after lumbar disc surgery. NSAIDs are mainly helpful for the initial three days after surgery. In addition to causing platelet dysfunction, risk of hemorrhage, gastric ulceration, and renal toxicity, there are concerns that NSAIDs may affect the bone metabolism and osteoblastic proliferation. Reuben et al. found that short-term perioperative administration of celecoxib, rofecoxib, or low-dose ketorolac (< or = 110 mg/day) had no significant deleterious effect on skeletal nonunion. In contrast, higher doses of ketorolac (120–240 mg/day), a history of smoking, and two-level vertebral fusions were found to significantly increase the incidence of nonunion following the spinal fusion surgery. Li et al. did a metaanalysis comprising of five retrospective studies with 1,403 participants. The authors found that short-time (<14 days) exposure to normal-dose NSAIDs (ketorolac, diclofenac sodium, celecoxib, or rofecoxib) were safe after spinal fusion, whereas short-time (<14 days) exposure to high-dose ketorolac increased the risk of nonunion. Therefore, the effect of perioperative NSAIDs on spinal fusion might be dose-dependent. NSAIDs should be used cautiously in renal, coronary, and cerebrovascular diseases.

Paracetamol (acetaminophen) has emerged as an effective and safe drug for the treatment of postoperative pain. Acetaminophen has analgesic and antipyretic effects, but unlike NSAIDs, it has weak peripheral antiinflammatory effects. It has minimal effect on the platelet function, making it useful during the intraoperative and postoperative periods. The analgesic mechanism of acetaminophen is not understood properly. It is believed to have a central action by acting as an inhibitor of the prostaglandins via the COX pathway. Acetaminophen rapidly enters the central nervous system (CNS), producing profound analgesia. In vitro, acetaminophen demonstrated a 4.4 times receptor selectiveness to COX-2 compared with COX-1. It is known to act as a nitric oxide pathway inhibitor through substance P or N-methyl- d -aspartate (NMDA) and strengthens the descending serotonergic inhibitory pathways. Active metabolites of acetaminophen have shown to affect the cannabinoid receptors. After intravenous administration of acetaminophen, a rapid and high plasma concentration is achieved within 5 min. Peak plasma concentration occurs within 15 min after administration. The dose of intravenous acetaminophen in adolescents and adults is 1 g every 4–6 h, with a maximum daily dose of 4 g. In children more than 2 years, and adults weighing less than 50 kg, 15 mg/kg should be administered at the same interval. Children and infants less than 2 years of age should receive no more than 10 mg/kg, and neonates and premature infants 7.5 mg/kg. The elimination half-life is 2–3 h, and the duration of analgesic effect is approximately 4–6 h. This may be prolonged in infants, neonates, and patients with renal impairment.

Corticosteroids

Aminmansour et al. found that the administration of 40 mg dexamethasone effectively reduces the postoperative radicular leg pain and narcotics usage in patients operated on for single-level herniated lumbar disc. A systemic review was published in 2014 by Jamjoom et al. to review the literature aimed at examining the efficacy of the use of intraoperative epidural steroids in lumbar disc surgery. Steroids may reduce the inflammation, inhibit phospholipase A2, and decrease substance P levels at the dorsal root ganglion. Sixteen trials published from 1990 to 2012 showed strong evidence favoring the use of epidural steroids to reduce pain in the early postoperative stage (0–2 weeks). They found, however, that steroids are ineffective in reducing pain in the late stage (more than 2 months to 1 year) or in reducing the duration of hospital stay. Their effectiveness in reducing pain in the intermediate stage (more than 2 weeks to 2 months) was found to be limited. The authors, however, concluded that the heterogeneity between the trials made it difficult to make undisputed conclusions. Before any valid conclusions can be made, there is a need for a large multicenter trial.