Multimodal Postoperative Pain Control After Orthopaedic Surgery

Function

NSAIDs

Non-steroidal anti-inflammatory drugs (NSAIDs) are common over-the-counter medications used daily for pain and inflammation. The mechanism of NSAIDs has been traditionally described by their peripheral efficacy in decreasing the pro-inflammatory mediators, prostaglandins. More recently, NSAIDs have been attributed to having a central role that augments its known peripheral action, by which it promotes the production of endogenous opioid peptides.[5] Due to fracture healing and fusion concerns, there are conflicting arguments in the orthopedic literature on the use of NSAIDs for pain control. Basic science studies have shown increased time to fusion in animal models using NSAIDs, though fracture healing has demonstrated mixed results. Hsu et al. recommend using NSAIDs in the MMA model due to a lack of high-quality evidence supporting decreased fracture healing in the clinical setting.[6] NSAIDs are proven to be effective for musculoskeletal pain, with head-to-head clinical studies noting equivalent pain control with NSAIDs compared with opioids with a reduced risk profile.[7][8] NSAIDs are used to target the associated inflammation. Recent studies have looked at the efficacy of pre-operative administration of NSAIDs and their results on postoperative pain scores. Pre-operative loading of meloxicam has decreased VAS pain scores in patients undergoing total knee arthroplasty for primary arthritis compared to post-operative administration alone.[9] A resulting decrease in the amount of patient-controlled analgesia was also seen. Contraindications with NSAIDs include peptic ulcer disease, chronic or end-stage renal disease, bronchial asthma, and breastfeeding women.[10]

Acetaminophen/Paracetamol

Acetaminophen is a commonly used over-the-counter analgesic and antipyretic. It is the most common alternative for patients who cannot use NSAIDs due to contraindications stated previously. Its mechanism of action is complex, as it acts on both the peripheral and central COX pathways, affecting the serotonergic, cannabinoid, and nitric oxide pathways [10]. Thus, it is used to target the pain cascade. Contraindications to the use of acetaminophen include liver disease or active alcohol intake, which can cause acute liver injury.

Gabapentinoids

Gabapentin, originally used as an anticonvulsant drug, is a commonly used modulator of neuropathic pain. It inhibits the trafficking of protein subunits to decrease the voltage-gated calcium channels on the plasma membrane of dorsal root ganglion neurons.[11] It has often been used in the treatment of diabetic neuropathic pain but has also been shown to be effective in treating acute pain. A meta-analysis of post-operative spine surgery showed decreased pain scores at 12 and 24 hours. In this same study, it was also shown that the addition of gabapentin to the normal post-operative pain regimen showed a significant decrease in total morphine consumption, as well as decreased vomiting, pruritus, and urinary retention, which are associated with morphine use.[12] 

Gabapentin is a scheduled drug that has been misused in opioid-addicted patients. It can act to potentiate methadone high and negate symptoms of opioid withdrawal.[13] The use of gabapentin is associated with confusion, fatigue, and somnolence, which can be mitigated somewhat by using the lowest dose possible. A strategy used by some surgeons is to use gabapentin preoperatively at bedtime a couple of days before surgery. It can be increased to 2 or 3 times daily post-operatively if needed. If patients are unable to use gabapentin, then pregabalin can be substituted. Gabapentin is contraindicated in patients with myasthenia gravis and myoclonus disorders.[14][15]

Transcutaneous Electrical Stimulation (TENS)

TENS is a method of pain control in which a small voltage electrical current is delivered to the skin over the desired site of analgesia. This modality can be used in the postoperative period to stimulate large-diameter peripheral nerves, which are believed to decrease pain by activating opioid receptors through an endogenous pathway.[1] There are mixed results on the use of TENS as an adjunct to normal post-op pain control, some attributing the variation in results to the amplitude and frequency used during treatment. A meta-analysis including twenty-one randomized controlled trials found that TENS around the surgical site decreased post-op analgesic consumption by 26.5 % and decreased opioid use post-operatively by 35.5 %.[16] Contraindications to the use of TENS include severe lymphedema, compromised skin at the desired location of application, or the presence of a pacemaker or defibrillator.

Cryotherapy

Cryotherapy is a part of the traditional physical aspect of decreasing pain in an extremity, whether post-operative or treating a closed injury such as an ankle sprain. It is the use of an external cold source in an attempt to decrease the temperature of the tissue in that area. Ice packs, cold water therapy, gaseous cryotherapy, and continuous flow cryotherapy are all used in cryotherapy. The effects on tissue include decreased edema, inflammatory mediators, and blood flow via vasoconstriction or local vasculature.[17][18][19] Various studies have looked at the effect of cryotherapy after orthopedic surgeries. Studies show a decrease in pain scores as compared to controls, as well as a decrease in opioid use postoperatively when cryotherapy is used in conjunction with traditional methods of pain control.[20][21][22][23][24][25] Complications with cryotherapy include nerve palsies, mostly involving superficial peripheral nerves. These injuries range from brief paresthesia to complete nerve injury without return of function. It is important to have appropriate insulation between the cold source and the targeted area. This is especially important in areas with less subcutaneous fat or patients with less fat content.[6]

Nerve Blocks

Nerve blocks include local and regional anesthesia to the targeted area. Nerve blocks are commonly used methods of analgesia in elective orthopedic surgery cases, including arthroscopy and arthroplasty. These can be utilized preoperatively, intraoperatively, or post-operatively. Hsu et al. recommend using a continuous catheter over a single shot when administering a nerve block. They report better pain control with a decreased chance of rebound pain often associated with lower extremity blocks. Various nerve block methods may differ based on surgeon preference, depending on the patient and surgical site. Problems include rebound pain and an increased risk of falls.[6]

Opioids

As discussed previously, opioids are a common medication used for severe acute pain. Orthopedic surgeons commonly use them in the post-operative period for pain control. There are significant risks associated with their use, including misuse, addiction, and overdose. Opioids bind the mu-opioid receptor and inhibit neurotransmitter release in the central nervous system. In their clinical practice guidelines, Hsu et al. recommend that opioids be used in the smallest dose and for the shortest amount of time possible. Short-acting opioids are preferred and recommended, as compared to long-acting opioids, which provide less opioid absorption per unit of time.[6] The oral administration of opioids is preferred to IV administration in postoperative patients who can tolerate the oral route. Pain scores are equivalent, with fewer morphine equivalents ingested in the oral administration group.[26] 

Multiple sources strongly recommend that opioids not be prescribed in conjunction with benzodiazepines due to the risk of increased sedation, overdose, and abuse. Park et al. noted a 3.9-time increase in overdose due to respiratory depression when using opioids in conjunction with benzodiazepines.[27] Opioids have been noted to be very effective and act synergistically when used with NSAIDs, compared to opioids as monotherapy.[28] Wojahan et al looked at the number of opioids consumed after knee arthroscopy and observed that 81 % of patients take fewer than twenty pills postoperatively.[29] This leads to the notion that when utilizing opioids in the postoperative patient, orthopedic surgeons are writing prescriptions too high in quantity. This results in a medication surplus that is then available for misuse. This misuse may also involve diversion to use by persons not under the physician’s care. Adverse effects of opioids include nausea, vomiting, dizziness, constipation, somnolence, and headache.

Cognitive Strategies

Cognitive strategies are great tools to implement for all patients before and after surgery. Providing patients with an appropriate estimate or overestimate of the pain level to expect postoperatively is a good strategy to help prepare patients for their surgery. Patients with co-morbid psychological issues, including anxiety, low appreciation of self-worth, and major depression, have been noted to experience more pain per nociception.[30] There is significant variation in the pain perceived among patients due to varying psychosocial issues. Patients who suffer from comorbid anxiety, major depression, opioid tolerance, and low self-worth may benefit from psychiatry consultation while admitted to the hospital. The honest, direct dialogue between the surgeon and the patient is of utmost importance regarding pain relief expectations. Enlisting support for acute pain and addiction medicine services is recommended in the clinical guidelines by Hsu et al.[6]

Issues of Concern

Opioid Safety

Opioids can be associated with significant morbidity if not handled appropriately. On the other hand, they can be a great tool to control postoperative pain when used correctly in the appropriate patient. In the in-patient and out-patient setting, it is important to reassess patient pain and change the pain regimen accordingly constantly. It is particularly important in the in-patient setting that a sedation status be performed before and after administration of each opioid medication or other medications with sedating effects, for that matter. This is recommended in the clinical practice guidelines by Hsu et al.[6] 

Pasero designed an opioid sedation scale to help monitor patients and guide medication regimen changes in the in-patient setting.[31] Since sedation is an impending sign of respiratory distress, direct monitoring of the patient before and after receiving medication is vital. Hsu et al. also recommend co-prescribing naloxone for patients who are at increased risk for respiratory depression. No studies demonstrate that this directly decreases prescription overdoses. Still, it has been seen to decrease overdoses on a community scale when naloxone has been made available to illicit drug users. Patients who would benefit from this include previous drug abusers and patients with anxiety who may be prescribed benzodiazepines by other providers. It is also recommended that all physicians register and monitor the Prescription Drug Monitoring Drug Program (PDMP) before prescribing pain medication.

Clinical Significance

Multimodal analgesia is the future for the alleviation of pain in many fields of medicine. The field of orthopedic surgery has been at the forefront of this new tool's clinical use and innovation for postoperative pain relief. This model shows benefits in many ways in the clinical setting. Orthopedic surgery can often be associated with significant pain in the early postoperative period. Balancing the need for pain control while mitigating the risk of adverse effects such as opioid dependence and adverse effects of medication with comorbid conditions can be difficult. MMA provides a broad array of medications and strategies that can be combined to work synergistically with one another to help orthopedic surgeons treat their patients as productively and safely as possible. Recent studies corroborate the idea that this model helps decrease post-operative pain beyond the standard monotherapy opioid regimen. This leads to less opioid use and, therefore, less risk to the patient.[32] Individual surgeons often create their regimens for how they approach MMA. Hsu et al. have broken their pain regimens into classes based on the severity of the injury and the associated surgery. The classes include major musculoskeletal surgery, minor musculoskeletal surgery, and non-operative or closed treatment. These recommended regimens include opioid management as well as alternative or adjuvant non-opioid medications (NSAIDs, gabapentin, acetaminophen).[6] This can be a good starting point for the young physician or physician who has not yet adopted an MMA approach in their practice. 

Enhancing Healthcare Team Outcomes

Just as successful multi-modal pain management requires different classes of medications, enhancing team outcomes requires many different types of team members. Some coordination may be required by a pain management doctor, anesthesiologist, pharmacists, PACU nurses, recovery nurses, and pre-operative nurses. Successful multi-modal pain management requires a streamlined strategy from pre-op to intra-op and post-op, including regional anesthesia, patient counseling, and multiple medications, but this has been shown to reduce narcotic usage and lead to successful postoperative pain management.[33]