Multimodal Analgesia
This post discusses multiple options for analgesia that can be used to help reduce relying solely on one mechanism to control post-operative pain, such as with opiates.
Multimodal analgesia is the practice of utilizing various analgesic medications that work on different receptors associated with pain pathways. By attacking pain from multiple receptors, you can reduce the burden of side effects that typically come with using only one medication. For example, you can reduce the total amount of opiates a patient will need post-operatively with a well balanced analgesic plan. This practice has gained a lot of favor recently in light of the opioid epidemic.
NSAIDs like Ketorolac (Toradol) and Celecoxib (Celebrex) are commonly used perioperatively. Cyclooxygenase (COX) receptors produce prostaglandins that promote inflammation. NSAIDs block COX receptors, leading to reduced inflammation. They can reduce opioid requirements by 30%. NSAIDs have a ceiling effect for analgesia, but not for side effects. Some adverse effects to look out for include gastrointestinal bleeding and renal injury. There is no evidence that they increase surgical bleeding.
Acetaminophen (Tylenol) is an antipyretic and analgesic that also works on COX receptors. It can decrease opioid requirements by 20%. IV acetaminophen is commonly used perioperatively. However, oral acetaminophen pre-operatively will have very similar analgesic effects.
Steroids have potent anti inflammatory and immunosuppressive effects that decrease the inflammatory response at the site of surgery. This decreases the pain input into the spinal cord from the site of surgery. Glucocorticoids, like dexamethasone (Decadron), are preferred perioperatively. The analgesic dose of 8 to 10 mg is slightly higher than the anti-nausea dose of 4 mg. There is no evidence that a single dose of steroids will increase surgical site infection or increase blood sugars relative to the already hyperglycemic state created by the surgery itself.
Alpha-2 receptor agonists such as dexmedetomidine (Precedex) have effects in the peripheral and central nervous system. Adding about 30-50 mcg of dexmedetomidine to a peripheral nerve block has been shown to increase length of block time with very minimal side effects. IV dexmedetomidine is commonly used as boluses in the pediatric population to decrease opioid requirements. Infusions can also be utilized for awake fiberoptic intubations and procedural sedation.
Local anesthetics such as bupivacaine are used subcutaneous at the surgical site, as well as for regional nerve blocks. Intravenous lidocaine has been shown to reduce systemic inflammation and directly depressed peripheral and central neuronal excitability. Recent evidence has shown a reduction in opioids required after major open abdominal surgeries when a lidocaine infusion was utilized intraoperatively and continued in the PACU.
Alpha-2-delta ligands, such as gabepentin and pregabalin have been shown to decrease overall post-operative opioid consumption. However, effective doses are commonly associated with prolonged sedation, dizziness, and nausea. For this reason, these medications are falling out of favor perioperatively.
Lastly, ketamine is growing in popularity for it’s subanesthetic analgesic properties. Ketamine is an NMDA-antagonist and has been shown to be particularly useful in surgical patients who chronically take opioids. There is growing use of ketamine infusions post-operatively in the PACU and on surgical wards.
