1. Patient-controlled analgesia (PCA) is any technique of pain management that allows patients to administer their own analgesia on demand.
   1. The five variables associated with all modes of PCA include bolus dose, incremental (demand) dose, lockout interval, background infusion rate, and 1- and 4-hour limits (Table 56-7: Usual Intravenous Opioid Patient-Controlled Analgesia Regimens for Opioid-Naive Adult Patient).
   2. Risk Factors for Use of Opioid Patient-controlled Analgesia (Table 56-8: Relative Risk Factors Associated with Patient-Controlled Analgesia)
2. Neuraxial Analgesia. Since the discovery of the opioid receptor, the intrathecal administration of opioids and the epidural administration of opioids plus a local anesthetic have produced significant pain control.
   1. Epidural analgesia is a critical component of multimodal perioperative pain management and improved patient outcome.
      1. The efficacy of an epidural technique is determined by numerous factors, including catheter incision site congruency, choice of analgesic drugs, rates of infusion, duration of epidural analgesia, and type of pain assessment (rest vs. dynamic).
      2. Ideally, the epidural catheter is positioned congruent with the surgical incision (Table 56-9: Guidelines for Adult Epidural Catheter Dosing Regimen).
      3. A local anesthetic plus an opioid in the epidural space is the most common drug combination and is believed to have a synergistic effect.
      4. Epidurally administered opioids have the distinct advantage of producing analgesia without causing significant sympatholytic effect or motor blockade.
      5. Analgesia occurs by way of a spinal mechanism (diffusion of drug into the spinal fluid) and through a supraspinal mechanism after systemic adsorption. Opioids with intermediate lipophilicity (hydromorphone, alfentanil, meperidine) have the ability to easily move between the aqueous and lipid regions of the arachnoid membrane and therefore have high meningeal permeability, which potentially confers higher bioavailability in the spinal cord. Nevertheless, morphine has greater bioavailability in the spinal cord than alfentanil, fentanyl, and sufentanil.
      6. In general, epidural administration of hydrophilic opioids tends to have a slow onset, a long duration, and a mechanism of action that is primarily spinal in nature. Epidural administration of lipophilic opioids, on the other hand, has a quick onset, a short duration, and a mechanism of action that is primarily supraspinal and secondary to rapid systemic uptake.
      7. Adjuvant medications that may enhance analgesia include clonidine and ketamine.
      8. Extended-release epidural morphine (DepoDur) consists of morphine encapsulated within a liposome delivery system, which provides controlled release of morphine for up to 48 hours. DepoDur is only approved for lumbar epidural administration.
   2. Intrathecal analgesia is provided with a variety of opioid analgesics (morphine, hydromorphone, meperidine, methadone, fentanyl, sufentanil) (Table 56-10: Intrathecal Analgesia).
      1. Hydrophilic opioids (morphine) traverse the dura slowly, bind to epidural fat poorly, and slowly enter the plasma. They tend to have a slow onset of action and a long duration and provide a broad band of analgesia. Delayed respiratory depression is more common with hydrophilic opioids secondary to rostral spread.
      2. Lipophilic opioids (fentanyl) rapidly cross the dura, are quickly sequestered into epidural fat, and promptly enter the systemic circulation. Lipophilic opioids tend to have a rapid onset of action, a short duration, and a narrow band of analgesia. Delayed respiratory depression is less of a problem with the lipophilic opioids.
      3. Other useful analgesic additives include the α2-agonists, NSAIDs, NMDA receptor antagonists, acetylcholinesterase inhibitors, adenosine, epinephrine, and benzodiazepines (Table 56-11: Intrathecal Analgesic Additives).
3. Peripheral Nerve Blockade. Single injection of peripheral nerve blockade may provide pain control that is superior to opioids with fewer side effects. Single-injection techniques are limited in duration, but continuous peripheral nerve block techniques may extend the benefits of peripheral nerve blockade well into the postoperative period (Table 56-12: Recommended Dosing Regimen of Local Anesthetics for Continuous Peripheral Nerve Blockade).
   1. The Brachial Plexus
      1. The interscalene block is the ideal peripheral nerve block for painful orthopedic and vascular procedures performed on the shoulder and upper arm but is a poor choice for forearm and hand surgery because the ulnar nerve is commonly spared.
      2. The supraclavicular approach to the brachial plexus provides anesthesia to the entire upper extremity with a single injection of local anesthetic. The safety of this approach has improved dramatically with the use of ultrasonography.
      3. The infraclavicular block is ideally suited for surgical procedures below the midhumerus such as the hand, wrist, forearm, or elbow. The block targets the brachial plexus at the level of the cords, where it is in close proximity to the axillary artery. Ultrasound guidance has dramatically improved the safety and success of the infraclavicular approach.
   2. The Lumbar Plexus
      1. Posterior approach (psoas compartment block) is indicated for major surgeries of the hip and knee. When combined with sciatic nerve blockade, virtually any surgical procedure can be performed on the lower extremity. The incidence of sciatic nerve injury after total knee arthroplasty, unrelated to regional anesthesia technique, is reported to be in the range of 0.2% to 2.4%. Sciatic nerve blockade can mask these complications.
      2. Anterior approach (femoral nerve block). Although the nerve can be visualized with ultrasonography both above and below the inguinal ligament, it is ideally visualized at the level of the inguinal crease; at this level, the nerve is positioned approximately 0.5 cm lateral to the femoral artery. The nerve provides motor innervation to the quadriceps femoris, sartorius, and pectineus muscles as well as sensory innervation to the anterior thigh and knee and the medial aspect of the lower extremity terminating as the saphenous nerve. Femoral nerve blockade (may be ultrasound guided) provides site-specific analgesia and is an integral part of any multimodal analgesic regimen after major knee or hip surgery.
      3. Saphenous nerve blockade is frequently combined with a lateral popliteal block or sciatic block for procedures involving the lower leg. The saphenous nerve is the only branch of the lumbar plexus below the knee and is the largest sensory terminal branch of the femoral nerve.
   3. Sacral Plexus
      1. After foot and ankle surgery, sciatic nerve blockade provides safe, effective, and long-lasting postoperative analgesia. Ultrasound guidance provides real-time visualization and high-quality images of the sciatic nerve. Continuous popliteal sciatic nerve blockade can be used in the inpatient and outpatient settings.
      2. Paravertebral blockade may provide segmental analgesia for numerous surgical procedures (thoracotomy, mastectomy, nephrectomy, cholecystectomy, rib fractures, video-assisted thorascopic surgery, and inguinal and abdominal procedures).

Acute Pain Management

1. Acute Pain Defined
2. Anatomy of Acute Pain
3. Pain Processing
4. Chemical Mediators of Transduction and Transmission
5. The Surgical Stress Response
6. Preemptive Analgesia
7. Strategies for Acute Pain Management
8. Assessment of Acute Pain
9. Opioid Analgesics
10. Nonopioid Analgesic Adjuncts
11. Methods of Analgesia
12. Continuous Peripheral Nerve Blockade Caveats
13. Complications from Regional Anesthesia
14. Perioperative Pain Management of Opioid-Dependent Patients
15. Organization of Perioperative Pain Management Services
16. Special Considerations in the Perioperative Pain Management of Children