• Rehana Jan, MD
• Leslie Schechter, PharmD
• Suzanne Lenart, RNC Paul H. Willoughby, MD

       INTRODUCTION

The field of acute pain management has changed substantially in recent years. In the past, acute pain management consisted primarily of opioids given intermittently by intramuscular injection. In addition to pain on injection, this lead to undesirable “analgesic gaps” or periods of inadequate pain control between peak and trough opioid levels. Consequently, patients were often reluctant to request pain medications ordered “as needed.”

        To provide more continuous analgesia, intravenous patient controlled analgesia (IVPCA) was introduced in the 1980s, leading to the development of specialized pain management teams, most often under the direction of anesthesiologists. The application of intrathecal opioids and epidural analgesia for postoperative pain management heralded the first pain service in the United States.¹ In Europe, Narinder Rawal presented his experience introducing the role of nurses as valued members of the acute pain management team.² By the early 1990s, 40% of US hospitals had acute pain services.³

JCAHO = Joint Commission on Accreditation of Healthcare Organizations.

        The American Society of Anesthesiologists (ASA) Task Force first established practice guidelines for acute pain management in 1995.⁴ These guidelines were revised in 2004, and the reader is encouraged to review this document.⁵ The Joint Commission of Accreditation of Healthcare Organizations (JCAHO) established standards (Table 79–1) for pain management in January 2001.⁶ These standards provided an impetus for hospitals to have an institution-wide commitment for policies and procedures to support effective pain management. This effort promoted the concept of pain as the “fifth vital sign” and established the patient’s right to pain management. It also became evident that an effective pain management program can only be achieved with a strong institutional commitment. The revised ASA guidelines of 2004 highlighted the importance of multidisciplinary collaboration among anesthesiologists, surgeons, nurses, pharmacists, and other members of the healthcare team.

        Early advances on this topic focused on safe application of aggressive techniques utilizing protocols and standing orders with the monitoring available on the ward. However, it is the PCA services that paved the way for the development of true acute pain management services providing on-demand systemic as well as epidural and intrathecal analgesia. The US model focused on physician management; the European model put a greater emphasis on the nursing role.

        In recent years, regional anesthesia has gained popularity because if its contribution to postoperative pain management. Single and continuous peripheral neural blockade is increasingly practiced in both the inpatient and outpatient setting. However, effective application of these techniques requires adequate expertise, surveillance, and organization, not simply placing the particular block or catheter. Multidisciplinary acute pain teams can monitor and titrate these techniques to maximize pain relief and safety while minimizing side effects.

        More aggressive techniques such as IVPCA, epidural analgesia, intrathecal opioids, and peripheral blocks find their best results when launched as part of a multimodal analgesic approach that incorporates nonsteroidal antiinflammatory agents (NSAIDs) and cyclooxygenase-2 (COX-2) inhibitors as well as other means of nonpharmacologic means to acute pain management (see Chapter 77, The Role of Nonopioid Analgesic Techniques in the Management of Postoperative Pain, for more information on nonpharmacologic means to pain management).^7,8 True multimodal analgesia targets multiple mechanisms of pain to effectively relieve both rest and dynamic pain.

        A dedicated acute pain management team enhances implementation of these techniques for pain management. The primary goals of an acute pain management service are to offer a wide variety of services, provide a high level of patient surveillance, and integrate these services into the overall hospital setting. Optimal analgesia requires judicious dose adjustment to maximize the benefits and minimize the side effects of therapy. This can only occur if the patient is adequately monitored.

        The purpose of this chapter is to provide strategies for effective postoperative pain management while enhancing safety and facilitating delivery of services. An organizational model for a nursing-based acute pain service is presented. Standard orders and protocols are also provided to facilitate implementation of the suggested principles and approaches. Finally, we provide many of the organizational tools and concepts we have found useful in the organizational design of our acute pain service.

        INTRAVENOUS PATIENT-CONTROLLED ANALGESIA

IVPCA is commonly used as part of a multimodal approach to postoperative pain control. Sechzer⁹ and Forrest¹⁰ popularized the concept of PCA. Patients self-administer small doses of intravenous opioid at predetermined intervals (lockout), to maintain a minimum effective analgesic concentration ( MEAC). This titration of the opioid provides a more constant plasma level of analgesic” and more consistent analgesia.¹¹ Maintaining opioid plasma levels within a tight range improves analgesia while reducing unwanted side effects that can occur with larger boluses. PCA pumps can be programmed to deliver opioids either by intermittent patient-controlled bolus doses alone or with a continuous background (or basal) infusion. PCA pumps are programmed to set the demand dose, lockout interval, hourly total dose, and basal infusion. Importantly, before starting PCA, analgesia must be established with an initial loading dose of opioid.¹² Without front loading, MEAC is not achieved for at least three elimination half-lives.¹³ PCA is intended to maintain a level of pain control, not to initiate satisfactory analgesia. Therefore, if the PCA process is interrupted by pump failure, a faulty intravenous, or inadequate patient dosing, the patient will require bolus titration to achieve comfort before reinitiating PCA.

Clinical Pearls

PCA advantages over intermittent injections include fewer analgesic gaps, maintaining analgesia with less total opioid consumption (thus with fewer side effects), less use of nursing staff time, and improved patient satisfaction. Patients can anticipate and proactively manage their pain, particularly before moving or coughing. There is also a psychological advantage because of the shortened interval between perception of pain and administration of medication.

        In the opioid-naïve patient, the addition of a basal infusion to IVPCA has been shown not to improve analgesia, but increases the risks of this technique.¹⁴ Without a basal infusion, the risk of clinically significant respiratory depression is generally low. Patients maintain normal levels of arterial CO2 in the early postoperative period while receiving PCA therapy. Postoperative respiratory functions (forced expiratory volume, functional residual capacity, and peak flow rates) are not significantly different from those in patients receiving intramuscular injections of opioids.^15–17

Clinical Pearls

The most common problem associated with IVPCA use is operator error, the most common cause of which is programming error and incorrect drug concentration.¹⁸ When a medication error involves a PCA pump, the risk of patient harm increases 3.5 times.¹⁹ The FDA‛s Manufacturer and User Facility Device Experience (MAUDE) Database for 2004 identified 21 deaths involving IVPCA pumps; 16 deaths were related to large-volume infusion pumps (LVP). Given that there are approximately 10 times as many EVPs as PCA pumps, it appears that the risk of a severe respiratory event from a PCA pump is at least 10 times greater than with an LVP.²⁰ To avoid these errors the nursing staff must understand the basis for therapy and be knowledgeable about the operational aspects of PCA pumps.

Clinical Pearls

Patient-related PCA problems include failure to understand PCA therapy, intentional analgesic abuse, underutilization because of unwarranted fears of addiction, and PCA by proxy (operation by an individual other than the patient). Patients should be educated about PCA before surgery; the education should be frequently reinforced throughout treatment.

        Morphine is the most commonly used PCA opioid. Hydromorphone and fentanyl are also favored because of their favorable metabolite profile. Meperidine has little place as an analgesic because of its neurotoxic metabolite, normeperi- dine. Table 79–2 summarizes the commonly used IVPCA equianalgesic opioid solutions.

        An iontophoretic, transdermal drug-delivery system (ITS) has demonstrated the ability to provide needle- free patient-controlled delivery of fentanyl. This patientcontrolled transdermal analgesia (PCTA) system is a preprogrammed and self-contained device about the size of a credit card. Clinical trials have demonstrated analgesic efficacy similar to that from standard morphine IVPCA.²¹

        When converting between opioids, these conversion doses should be considered as an approximation because of incomplete cross tolerance. Patient responses may vary when converting from one opioid to another. Similar rules apply when converting the IV opioid therapy to the oral opioid analgesic therapy (Table 79–3).

        Safe and effective use of PCA requires institution-wide protocols and standard orders (Figure 79-9 through 79-4). Clinicians must have a thorough understanding of equianalgesic opioid doses (see Table 79–2).

        PERIPHERAL NERVE BLOCKS

Peripheral nerve blocks are useful in providing surgical anesthesia and postoperative analgesia^22–23 with an acceptable side effect profile.^23–24 Single-injection techniques are limited in duration but can be extremely useful in the immediate postoperative period. Continuous catheter techniques can extend the duration of analgesia to the desired length of time. The greatest hindrance to the catheter technique was the unavailability of appropriate equipment both for catheter insertion and drug delivery. Both of these obstacles have now been overcome. There are commercially available catheter insertion kits and drug delivery systems. The infusion pumps now available are small, portable, and lightweight. There is a large variety of commercially available PCA pumps with different characterists.²⁵ The introduction of these lightweight, portable infusion pumps has made home infusion possible, and it has been shown to be effective in randomized, doubleblind, placebo-controlled studies.^26–28

^a In opioid naive patients.

ACL = anterior cruciate ligament.

        Numerous approaches have been described to the lumbar, sacral, and brachial plexuses and in the paravertebral space. The planned surgical procedure will determine the peripheral nerve block needed for postoperative analgesia. A brief example of common indications is listed in Table 79–4. The reader should refer to the respective chapters on individual nerve block techniques for in-depth discussion on indications and technical aspects of their use. In general, the peripheral nerve block techniques are indicated in patients expected to have moderate-to-severe postoperative pain that is not easily controlled with opioids or when opioid side effects are problematic.

        Possible modes of local anesthetic infusion through these catheters include intermittent bolus, continuous infusion, or continuous infusion with PCA boluses. Infusion mode is often a matter of clinician preference. Continuous infusions and continuous infusion with PCA have been shown to be superior to the intermittent bolus technique.²⁹

        In an ambulatory setting, patient selection is critical. Only patients who are capable of accepting the additional responsibility of the catheter and infusion pump should be selected. Since some degree of cognitive dysfunction may occur in the early postoperative period, patients will benefit from a caregiver at home for the first 24-48 h who can participate in patient care. To decrease the risk of local anesthetic toxicity, patients with hepatic or renal insufficiency should not be sent home with continuous catheters if they do not have a caregiver at home. Hence, patients without a caregiver, with baseline cognitive difficulties, with certain underlying medical problems, or patients living a distance from the medical facility may be poor candidates for ambulatory infusion techniques.

Figure 79–1. Adult patient-controlled analgesia (PCA) order form.

Figure 79–2. PCA/CADD pump/continuous IV infusion analgesia flow sheet.

Figure 79–3. Pain assessment sheet.

Figure 79–4. Pain assessment sheet.

        Recommendations for local anesthetic injection volume and catheter infusion rates are provided in the respective chapters. The reader should note that the suggested doses, volumes, concentrations, and infusion rates are only general guidelines and must be adjusted for individual patients. More in-depth discussion on these variables can be found in Chapters 10 (Local Anesthetic Solutions for Continuous Nerve Blocks) and 64 (Continuous Peripheral Nerve Blocks in Outpatients).

        The successful use of peripheral catheters in the ambulatory setting requires patient education that should start in the preoperative area and extend into the postoperative period. Both patients and their caregiver must be involved. Instructions should be both verbal and written and include pager numbers and telephone numbers of responsible healthcare providers who will be available around the clock if problems occur. Although the surgeon is responsible for the overall care of the patient, the anesthesiologist providing the continuous regional technique must be responsible and available for catheter-related problems.

        Key elements of patient instructions include:

Careful follow-up is necessary with any continuous catheter technique. Visiting nurses maybe helpful. Patients may benefit from daily telephone contact with specific questions about quality of analgesia, local anesthetic side effects, and possible catheter site infection. Documentation of these patient contacts should be made.

Clinical Pearls

Patients may remove their peripheral infusion catheters at home, may return to the medical facility to have them removed, or a visiting nurse may remove the catheter. This may depend on the patients’ abilities, the distance they must travel from the hospital, and their degree of mobility. Reusable infusion pumps may be mailed to the surgical facility in a padded envelope. With proper selection and education of patients, the incidence of injury to the blocked limb is very low.³⁰

Complications of Continuous Catheter Techniques

IVPCA = intravenous patient-controlled analgesia, NSAIDs = nonsteroidal antiinflammatory drugs, COX-2 = cydooxygenase 2, TKR= total knee replacement, BKA = below the knee amputation, ACL = anterior cruciate ligament, ORIF = open reduction, internal fixation.

Successful use of peripheral nerve catheter infusions requires an infrastructure consisting of anesthesiologists, surgeons, pharmacists, and nurses:

        MULTIMODAL APPROACH TO ACUTE PAIN MANAGEMENT

Multimodal analgesia produces optimal pain relief by targeting pain at multiple pathways.³⁵ Combining analgesic techniques and drugs has a synergistic or additive effect and decreases the requirement for individual medication, thereby reducing the incidence of side effects.³⁶

        The surgical stress response produces endocrine and metabolic responses in the body. These pathways can be targeted pharmacologically at specific levels by adopting a multimodal approach to pain control.³⁷ The focus of the multimodal approach to acute postoperative pain management is to facilitate the patient’s rehabilitation. Multimodal approaches combined with accelerated recovery protocols can reduce length of hospital stay.³⁸ This has been shown to work when the surgical team, anesthesiologists, nurses, and patients work together within established clinical pathways.³⁹

        Chronic pain has been identified as a consequence of surgery and poorly controlled acute pain.⁴⁰ Multimodal techniques may reduce central sensitization, improve pain control, and ultimately reduce long-term sequelae. The concepts of preemptive analgesia are discussed in Chapter 76 (Preemptive Analgesia, Regional Anesthesia, and the Prevention of Chronic Postoperative Pain). Local anesthetics and regional anesthesia techniques are critical components of multimodal analgesia. Potential uses are described in the following sections and in Table 79–5.

        Opioids and nonsteroidal antiinflammatory drugs (NSAIDs) act both centrally and peripherally to decrease afferent impulses to the dorsal horn of the spinal cord. Ketamine, an ?γ-methyl-D-aspartate (NMDA) receptor antagonist, when used in small doses (0.5-0.15 mg/kg IV) has been shown to improve pain relief if administered with opioids intravenously or epidurally.^41,42

        With appropriate patient selection, NSAIDs can be very effective. However, in some patients and situations NSAIDs can exert an antiplatelet effect that can cause surgical bleeding. They may also cause renal dysfunction. NSAIDs have an opioid-sparing effect⁴³ and can be administered orally or parentally. COX-2 inhibitors do not have an antiplatelet effect, making them desirable for postoperative pain management. Concern for cardiovascular problems has led to the withdrawal of certain COX-2 inhibitors from the market. However, this risk is associated with a duration of use longer than is indicated for most acute pain situations.

        CONTINUOUS EPIDURAL ANALGESIA

Use of continuous epidural infusions of local anesthetic with or without opioids has become a cornerstone of multimodal analgesia.⁴⁴ The use of dilute local anesthetic solutions has been shown to decrease the incidence of deep venous thrombosis in the postoperative period.⁴⁵ It is an effective weapon in attenuating the endocrine metabolic response to surgical stress and to provide dynamic pain relief.⁴⁶ The epidural catheter must be functional and cover the dermatomal distribution of the surgical incision to be effective. Epidural catheters are best inserted at the middermatome of surgical trauma. Care must also be taken to advance between 3 and 5 cm of epidural catheter into the epidural space. A shallower insertion results in greater incidence of catheter dislodge- ment, whereas an excessive length of catheter reduces efficacy and increases risk of’catheter knotting. The routinely used nylon epidural catheters are difficult to direct in the epidural space, regardless of the direction of the epidural needle bevel. Hence, it is best to target a short length of catheter at the precise spinal cord level to cover surgical pain.

Clinical Pearl

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Stimulating Catheters. Ultrasound-Assisted Nerve Blocks in Adults. Cutaneous Blocks for the Upper Extremity. Cervical Plexus Block.