Postoperative pain is a major problem. Up to 86% of patients experience postoperative pain with 75% of those reporting as moderate to severe in nature.¹ In fact, Tennant et al. reported that over half of patients reported inadequate pain management following their own cases.² Management of postoperative pain is tantamount for several reasons. Given that the opioid epidemic has nearly claimed 450 000 lives from overdose involving elicit and prescription opioids from 1999 to 2018, the role of opioids and attenuation of postoperative pain is crucial.³ Excess opioid prescription is now recognized as an important factor of opioid abuse.⁴ Furthermore, there are concerns that acute pain can become chronic pain.⁴ Specific surgeries have been sighted to increase risk of acute postoperative pain becoming chronic pain including inguinal hernia repair, thoracotomy, and breast surgery.⁵ Postoperative pain is one of the most common factors cited for unexpected admissions to the hospital as well as delayed discharge.⁵ Given these factors and the fact that controlling postoperative pain can be challenging, it is necessary to establish an effective postoperative pain management service.

In this chapter, we will discuss and review (1) current postoperative pain management models, (2) general postoperative pain treatment strategies, (3) utility of pain specialist on site, (4) regular pain assessment measurement tools, (5) continued pain education of patient and team involved, (6) adopting analgesic guidelines such as the enhanced recovery after surgery (ERAS) guidelines, (7) documentation/follow-up plans, and (8) importance of maintaining communication among the team involved in the patient’s care. It is our aim that we be able to review current guidelines and models to effectively run a postoperative pain management services to optimize postoperative pain control for our patients.

Pain control in the perioperative setting has a direct influence in surgical outcomes. A patient experiencing unrelieved pain will have a decreased overall satisfaction and have difficulty engaging in rehabilitation sessions. This will lead to a prolonged recovery and an increase in morbidity, mortality, and the risk of developing persistent pain after surgery.⁶,⁷,⁸ For this reason, an acute pain service (APS) is created as a multidisciplinary team focused on pain management and improving patient functional capacity in the preoperative, intraoperative, and postoperative phases.

An APS consists of a group of motivated medical providers who have knowledge in regional anesthesia and multimodal analgesia. These providers further elaborate an analgesic plan and perform peripheral or neuraxial blocks in the perioperative setting.⁹,¹⁰ However, this
group of providers could benefit from additional medical specialties who could help create a well-rounded approach to treating patients.

The evolution to a formalized service will involve the organization of a multidisciplinary team (anesthesiologist, nurses, surgeons, social workers, physical and occupational therapist) with well-defined goals in terms of analgesia and patient functional capacity.¹¹,¹²,¹³ This involves the allocation of financial, structural, and personnel resources to streamline patient care via specific protocols that result in low variability and effort, with high throughput patient care.¹⁰

Not every protocol can be strictly applied on every situation. In some instances, changes to the original plan must be made tailored to each patient. These circumstances could be the type of surgery, past medical history, medication history, and patient’s desire. Adapting to these variations require depth knowledge in pain management, pharmacology, and multimodal analgesia (including interventional pain management such as neuraxial or peripheral nerve blocks) to select the most appropriate and safest plan.

Essential competencies of a modern APS were described in 2002 by N. Rawal in the Regional Anesthesia and Pain Medicine editorial, which remain the core goals of the discipline today.¹⁴ (1) The APS must be available around the clock to provide consultation and interventions for severe acute pain; (2) Team leaders must round on the patients and assess pain severity and treatment efficacy; (3) The APS team must consist of communication between surgical teams, ward nurses, physical/occupational therapists, and pharmacologist in behalf of patient recovery; (4) The APS team must engage in continuing education for all medical providers, regarding safety and analgesia; (5) Continuous patient education on expectations and available treatments; (6) The APS team must undergo periodic audits and quality controls to ensure the best possible APS system.

Since the 1990s, the number ambulatory surgeries in the United States have increased more than 100%,¹⁵,¹⁶ and the number of outpatient surgical procedures in the United States is expected to grow from ˜129 million procedures in 2018 to ˜144 million procedures by 2023. APS should provide optimal postoperative pain management to patients who receive outpatient procedures.

The complexity in this situation is being efficient with the utilization of time and resources in a high passed center. In a short period, the APS team should identify patients who are at risk for increased postoperative pain (chronic pain patients, history of substance abuse, and orthopedic surgeries) and develop an optimum pain control strategy for each patient who would prevent emergency room visits, delayed discharges, and unplanned re-admissions (by uncontrolled nausea, vomiting, or pain; over sedation with respiratory depression; or complications related to regional anesthesia).⁵ For these reasons, it is imperative the implementation of multimodal analgesia (including regional techniques and peripheral nerve blocks catheters) to minimize opioids requirements. In the immediate postoperative period, nausea, vomiting, and pain should be treated aggressively with rescue medications. Effectiveness of nerve blocks and possible complications should be evaluated.

Upon discharge, instruction to continue nonopioids analgesic should be the first line. In cases when opioids are warranted, only short-acting opioids should be prescribed. In case of chronic pain patients, the medications should be individualized and early follow-up with the chronic pain clinic is advised.⁵ In case of nerve catheter was used for outpatient pain control, the patient should receive specific clear instruction regarding nerve catheter maintenance and expectations upon catheter removal. The patient should be contacted over the phone daily by the APS personnel until the catheter is discontinued.

Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage.¹⁷ The perception of pain can be complicated and can be dictated by several variables.¹⁸ Good pain management in the perioperative period is not just humane, but
also, poorly controlled pain has been related to increased morbidity and mortality¹⁷,¹⁹,²⁰,²¹,²² secondary to inability to participate in early rehabilitation, delaying discharge, prolonging recovery times,¹⁹ and increased risk of persistent postsurgical pain²³ that contribute with the opioid crisis that we are facing.

Nociception is the process of a noxious stimulus as a result of four main processes: transduction, transmission, modulation, and perception. Transduction is the conversion of the stimulus to a signal or electrical impulse by a peripheral nociceptor. Transmission is the propagation of the impulse from the periphery to central nervous system. Modulation is the amplification or dampening of the signals by the release of excitatory or inhibitory neuropeptides in the dorsal horn of the spinal cord. Perception is processing of the signal by the sensory cortex.²⁴ Many medications to decrease pain target one or multiple areas of pain perception. Please refer to Table 11.1 for complete general treatment options.

Opioids are by far the mainstay treatment of moderate to severe nociceptive pain, especially in cancer-related situations. A retrospective study across 380 U.S. hospitals showed that about 95% of surgical patients were treated with opioids.²⁵

The reason for their popularity is secondary to their effectiveness to decrease pain, multiple forms of administration and formulations (oral, intravascular, transdermal, sublingual, rectal, subcutaneous, intramuscular, transnasal, or neuraxial), they do not have ceiling effect, they have different modes of administration (scheduled, as needed, patient-controlled analgesia, or continuous infusion), and they have been widely studied drugs.

The main mechanism of action for analgesia is through opioid receptors agonism: µ, κ, and δ located in the peripheral and central nervous system. They are G protein coupled and, when activated, produce reduction of neuronal excitability by hyperpolarization on neurons capable of transduce, modulate, and perceive pain. This activation also explains their well-known side effects: respiratory depression, sedation, euphoria, and decreased gastrointestinal motility.²⁶ These side effects are responsible for increased morbidity, mortality, and length of stay¹⁷,¹⁹,²⁰ after surgery. This has generated the need for a shift in management when approaching postoperative analgesia.

Multimodal analgesia aims to reduce the of opioid dependency in the perioperative period by combining analgesic agents with different mechanism of actions, that work in conjunction to achieve a better analgesia, decreasing the opioid consumption, and consequently diminishing their associated side effects.²⁷ Commonly used drugs are nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen, gabapentinoids, NMDA antagonist, and local anesthetics.

Nonsteroidal anti-inflammatory drugs like ketorolac, ibuprofen, or celecoxib interfere in the transmission and perception of pain. They exert their effect by inhibiting the enzyme cyclooxygenase 1 (COX-1) and/or cyclooxygenase 2 (COX-2) at the peripheral nociceptor
and at the dorsal horn. As consequence, the production of prostaglandins from arachidonic acid is blocked, which decreases inflammation. NSAIDs have shown to reduce opioid requirements in mild to moderate pain and increased patient satisfaction.²⁸,²⁹,³⁰ Related side effects are a product of their own mechanism of action; by inhibiting COX-1, the decreasing production of prostaglandins E2 (PGE2) makes the gastric mucosa propene to gastric ulcers; decreasing PGE2 along with prostaglandin I2 (PGI2) impairs renal blood flow rising the risk of developing or worsening renal failure; blocking platelet’s COX-1 decreases the formation of thromboxane A2 and interferes with platelet aggregation and bleeding. Selective COX-2 inhibitors like celecoxib have the advantage of not increasing the risk of bleeding or gastrointestinal ulceration; however, evidence shown a mild increased risk of cardiovascular events.³¹

Acetaminophen falls into the analgesics and antipyretic medications. Although its main mechanism of action is not well defined, it decreases prostaglandin production centrally in the brain (by blocking COX-1 and COX-2). Studies have also demonstrated the possibility of a variant form; COX-3.³² Studies confirm its benefits in decreasing opioid requirements.³⁰ Unlike NSAIDs, acetaminophen lacks peripheral anti-inflammatory properties and can, therefore, be taken in combination with NSAIDs. This combination might be more effective than either NSAID or acetaminophen alone to decrease opioid consumption.³³ Although acetaminophen has a good safety profile, hepatotoxicity is a risk when daily doses surpass the 4000 mg.