A postoperative patient is receiving morphine sulfate via patient-controlled analgesia

Intravenous Patient-Controlled Analgesia

Intramuscular and subcutaneous opioids are inexpensive, easy to administer, and associated with a long history of safety but are not commonly used in the United States because of the need for repeated painful injections, delayed (and sometimes erratic) absorption of drug, and an inconsistent analgesic response caused by variation in plasma opioid concentration. Intravenous patient-controlled analgesia (PCA) allows patients to control their own pain management by self-administering small doses of intravenous opioids. A 2015 meta-analysis concluded that PCA is often preferred by patients compared with nurse-administered analgesia on request, and PCA was shown to provide better pain control and increased patient satisfaction compared with non–patient-controlled methods.28 The American Society of Anesthesiologists (ASA) Task Force for Acute Pain Management in the Perioperative Setting recommended that “these modalities [epidural or intrathecal opioids, systemic opioid PCA, and peripheral regional techniques] should be used in preference to intramuscular opioids ordered ‘as needed.’ ”29 The American Pain Society has recommended the use of intravenous opioid PCA when parenteral administration of analgesics is necessary and the oral route is not available.30

PCA has been used via the intravenous and epidural routes after cesarean delivery. A study that compared intravenous and epidural PCA usingfentanyl reported higher pain scores and greater fentanyl consumption with the intravenous route, although patient satisfaction was similar in the two groups.31 In another study that compared intravenous versus epidural PCA usinghydromorphone, drug requirement was 3- to 4-fold higher in the intravenous group; the two groups had similar pain and sedation scores, but patients in the intravenous group reported more frequent drowsiness and less pruritus.32 Studies that compared intravenous morphine PCA tosingle-shot epidural morphine administration for postcesarean analgesia showed that analgesia and patient satisfaction were better and sedation was less with epidural morphine, although the incidence of pruritus was higher.33–35

EFFICACY

IV-PCA with morphine has been clearly demonstrated to provide superior postoperative analgesia in comparison with traditional intramuscular (IM) morphine regimens, as well as greater patient satisfaction, improved ambulation, and reduced sedation levels.79–82 Although the quality of postoperative analgesia with IV-PCA may be inferior to that with neuraxial techniques,81–83 patient satisfaction tends to be higher with IV-PCA. In a comparison of IV-PCA diamorphine with PCEA diamorphine, pain scores fell more rapidly with PCEA and patients were less sedated during the first postoperative day, but overall satisfaction scores were higher with IV-PCA.84 In fact, of all analgesic regimens, patient satisfaction levels tend to be the highest with IV-PCA. Most parturients who have undergone cesarean delivery appear to use IV-PCA to achieve adequate, but not complete, analgesia. Parturients seem willing to accept a lesser degree of analgesia in order to be more alert, have less nausea, and thus feel better able to interact with their infants. Other important benefits of IV-PCA appear to be a lower incidence of opioid-mediated side effects, such as pruritus,81–83 and a greater degree of patient control over these side effects.84

Significant pain may rapidly supervene after regression of the neuraxial blockade in patients receiving IV-PCA after they have undergone cesarean section with regional anesthesia.85 An opioid “loading dose” should be administered to provide a baseline effective opioid plasma concentration in these patients. Serum levels can subsequently be maintained within a narrow therapeutic range by self-administered IV-PCA boluses. Otherwise, patients may not be able to generate sufficient plasma opioid levels to control their pain with IV-PCA alone, which may therefore fail to provide analgesia for them (Table 23-4).

Intravenous Patient-Controlled Analgesia

Various factors, including the aforementioned broad interpatient and intrapatient variability in analgesic needs, variability in serum drug levels (especially with intramuscular injection), and administrative delays, may contribute to inadequate postoperative analgesia. A traditional prescribed as-needed (PRN) analgesic regimen probably cannot compensate for these limitations. By circumventing some of these issues, IV patient-controlled analgesia (PCA) optimizes delivery of analgesic opioids and minimizes the effects of pharmacokinetic and pharmacodynamic variability in individual patients. IV PCA is based on the premise that a negative-feedback loop exists; when pain is experienced, analgesic medication is self-administered, and when pain is reduced, there are no further demands. When the negative-feedback loop is violated, excessive sedation or respiratory depression may occur. Although some equipment-related malfunctions can occur, the PCA device itself is relatively free of problems, and most problems related to PCA use result from user or operator error.30

A PCA device can be programmed for several variables, including the demand (bolus) dose, lockout interval, and background infusion (Table 81.1). An optimal demand or bolus dose is integral to the efficacy of IV PCA because an insufficient demand dose may result in inadequate analgesia, whereas an excessive demand dose may result in a higher incidence of undesirable side effects such as respiratory depression.31 Although the optimal demand dose is uncertain, the data available suggest that the optimaldemand dose is 1 mg for morphine and 40 μg for fentanyl in opioid-naïve patients; however, the actual dose for fentanyl (10-20 μg) is often less in clinical practice.30 The lockout interval may also affect the analgesic efficacy of IV PCA. A lockout interval that is too long may result in inadequate analgesia and decrease the effectiveness of IV PCA. A lockout interval that is too short allows the patient to self-administer another demand dose before feeling the full analgesic effect of the previous dose and thus may contribute to an increase in medication-related side effects. In essence, the lockout interval is a safety feature of IV PCA, and although the optimal lockout interval is unknown, most intervals range from 5 to 10 minutes, depending on the medication in the PCA pump; varying the interval within this range appears to have no effect on analgesia or side effects.30

Most PCA devices allow administration of a continuous or background infusion in addition to the demand dose. Initially, routine use of a background infusion predicted certain advantages, including improved analgesia, especially during sleep; however, analgesic benefits of a background infusion have not been successful in opioid-naïve patients. A background infusion only increases the analgesic dosage used and the incidence of adverse respiratory events in the postoperative period, especially in adult subjects. Furthermore, use of a nighttime background infusion does not improve postoperative sleep patterns, analgesia, or recovery profiles.32 Although routine use of continuous or background infusion as part of IV PCA in adult opioid-naïve patients is not recommended, a background infusion in opioid-tolerant or pediatric patients may be effective (see later sections, “Opioid-Tolerant Patients” and “Pediatric Patients”) (also see Chapter 24).

Patient-Controlled Analgesia

IV patient-controlled analgesia (PCA) is often used for women who have a contraindication to neuraxial analgesia (e.g., severe thrombocytopenia). The infusion pump is programmed to give a predetermined dose of drug upon patient demand. The physician will program the pump to include a lockout interval to limit the total dose administered per hour. Advantages of this method include the sense of autonomy, which patients appreciate, and elimination of delays in treatment while the patient's nurse obtains and administers the dose. In general, PCA results in a decreased total dose of opioid during labor.17 Fentanyl, remifentanil,18 and meperidine are the opioids most commonly used with this technique.

Intravenous Patient-Controlled Analgesia

An increasingly popular and effective modality using the parenteral route of administration is IV PCA. This modality minimizes the steps involved in the delivery of analgesia and increases patient autonomy and control. Opioids are the agent of choice forIV PCA. In comparing IV PCA with conventional intermittent nurse-administered opioid delivery, patients obtain prompt analgesia, receive smaller doses of opioids at more frequent intervals, can maintain blood concentration of drug in the analgesic range, and have a lower incidence of drug-related side effects. Candidates for IV PCA are patients who can understand the basic steps involved in use of the device, who are willing to assume control of their analgesia, and who are physically capable of activating the device. Such patients include children as young as 4 years of age and most adults, including geriatric patients.

The preferred agents for IV PCA are opioids, with morphine sulfate most commonly chosen. Other opioids used for IV PCA include hydromorphone, fentanyl, and meperidine. Methadone IV PCA has been described. Physicians’ orders for IV PCA must specify the drug, drug concentration, loading dose, bolus dose, continuous infusion rate (basal rate), lockout interval, and dose limits. Selection of these parameters is based on the patient’s age, medical status, and level of pain. The routine use of a continuous basal infusion rate with IV PCA remains controversial. With a continuous infusion, drug is delivered to the patient regardless of demand, thus resulting in the potential for a higher incidence of drug-related side effects, including respiratory depression. It is safest to restrict the use of basal infusions to patients in special categories, including those with severe pain from extensive surgery or trauma and patients who are tolerant because of chronic opioid use.

The use of structured protocols and guidelines is encouraged for facilities using IV PCA. The medical and nursing staff need to receive training in the care of patients using this modality. There is an increased risk for complications if staff members are not trained to understand the concept of IV PCA; to perform appropriate patient selection, education, and assessment; to use appropriate drug and dose selection; and to establish appropriate monitoring requirements and protocols for management of side effects.

6 What is intravenous patient-controlled analgesia (PCA)?

Intravenous patient-controlled analgesia (PCA) is a system of opioid delivery that consists of an infusion pump interfaced with a timing device. It allows the patient to titrate the analgesic dose required for optimal control of pain. The patient presses a button, and a preset dose of analgesic is delivered. A programmed “lockout” period (usually 6 to 15 minutes) prevents inadvertent overdoses and excessive sedation. This system may be used on top of a baseline continuous infusion. The parameters that can be set therefore include the presence, or absence, of a background continuous infusion, the bolus dose of opioid administered, and the “lockout” period (during which further opioid cannot be delivered).

Intravenous Patient-Controlled Analgesia

Intravenous patient-controlled analgesia (IV PCA) is considered the gold standard by which systemic opioids are delivered postoperatively. Unlike that seen for traditional “as needed” PRN analgesic regimens, IV PCA allows the clinician to compensate for several factors, including the wide interpatient and intrapatient variability in analgesic needs, variability in serum drug levels, and administrative delays, which might result in inadequate postoperative analgesia. By incorporating a negative feedback loop into the device itself (presence of pain leads to self-administration of opioid, whereas there should be no demands with the absence of pain), the IV PCA device per se has a safety device integrated into its design, although when the negative feedback loop is violated, excessive sedation or respiratory depression may occur.6,7 The majority of the problems related to IV PCA usage result from user or operator errors, and are not attributable to the device itself.6

The variables that can be programmed into an IV PCA device include the demand or bolus dose, lockout interval, and background infusion. The optimal settings for IV PCA administration of opioids for postoperative pain management are not known; however, there are general principles that may promote effective postoperative analgesia. The demand or bolus dose should be set such that there is not an insufficient demand dose (which may result in inadequate analgesia) nor an excessive demand dose (which may result in side effects such as respiratory depression).8 For opioid-naïve patients, a commonly used demand dose for morphine is 1 mg, and that for fentanyl is 10 to 20 μg.6,8 The lockout interval should be set such that the patient may evaluate the full analgesic effect of the previous dose before self-administration of a subsequent dose. A lockout interval that is too short may contribute to an increase in medication-related side effects whereas one that is too long may result in inadequate analgesia. Commonly used lockout intervals range from 5 to 10 minutes and varying the interval within this range appears to have no effect on analgesia or side effects.6,9 The final variable is the continuous or background infusion. Although the use of a background infusion was initially thought to provide improved analgesia especially during sleep, the routine use of continuous or background infusions in IV PCA in adult opioid-naïve patients is not recommended due to the increased incidence of side effects such as respiratory depression.10,11 Use of a background infusion, even if limited to nighttime, in opioid-naïve patients does not improve analgesia or sleep patterns.10,12,13 However, a background infusion for opioid-tolerant or pediatric patients may be more appropriate.

Use of IV PCA when compared to traditional PRN analgesic regimens may be associated with improved patient outcomes including superior postoperative analgesia, improved patient satisfaction, and possibly a decreased risk of pulmonary complications.14,15 At least two meta-analyses have been conducted in comparing IV PCA to PRN administration of opioids. Both meta-analyses suggest improved analgesia with IV PCA compared to PRN administration of opioids. An early meta-analysis of 15 randomized trials compared PRN IM dosing versus IV PCA but without a significant decrease in opioid consumption.14,15 There was no obvious economic benefit for IV PCA, although one meta-analysis demonstrated a decreased risk of pulmonary complications with IV PCA.14 In addition, patients tended to prefer IV PCA,14,15 which may result in greater patient satisfaction.14-17 In terms of opioid-related side effects, the incidence of these, including respiratory depression (<0.5%), from IV PCA does not appear to differ significantly from that administered via other routes (e.g., IV, IM, or subcutaneous).11,14,17,18

Postoperative Care

Leaving the operating room, patients are dressed with pressure dressings for 36 to 48 hours.

Postoperatively, pain is controlled with intravenous patient-controlled analgesia, and once diet is advanced, oral narcotic pain medication. Ambulation is prescribed after 24 to 48 hours, and hospital discharge is the norm after 72 hours of hospital observation. Nearly 50% of patients are off narcotic-type pain medication by the time of hospital discharge. The labial drains are removed on the day of discharge.

The Foley catheter and vaginal packing are removed on the 6th or 7th postoperative day. Patients are then instructed on dilation. They are expected to dilate three times daily for the first 3 months, then twice daily for 6 to 9 months, then daily thereafter for 15 minutes each session. After 18 months, experimentation with lesser dilation frequencies is possible. The size of the dilator initially is 1 inch but increases to 1½ inches within the first 4 weeks after surgery (Fig. 10.17).

Intravenous Patient-Controlled Analgesia

Many opioids have been used effectively for intravenous patient-controlled analgesia (IV PCA). Opioids that are pure μ-receptor agonists tend to be the first choice for IV PCA.26 The ideal opioid for IV PCA has a rapid onset of action, high efficacy, and intermediate duration of action without significant accumulation of drug or metabolites over time.12 Morphine, hydromorphone, and fentanyl most closely fulfill these criteria and are widely used for opioid-based IV PCA. Conversely, meperidine is generally considered a poor choice for IV PCA agent because the active metabolite, normeperidine, can accumulate and cause CNS excitation, including delirium, tremors, myoclonus, and seizures.27 However, there may be occasions when meperidine is a reasonable analgesic option. The most recent study examining the safety and efficacy profile of meperidine PCA28 indicated a CNS toxicity rate of 2%, and recommended a maximum safe dose of 10 mg/kg per day for no longer than 3 days. Patients should be without comorbid renal or hepatic dysfunction, and require careful evaluation and monitoring. All opioids have a similar spectrum of adverse effects, although qualitative differences are detectable. The patient’s clinical history and hospital protocols tend to influence the choice of opioid selected for IV PCA. There are few prominent differences in pain scores and incidence of adverse effects between different opioids.26,29,30 Consequently, patients tend to be satisfied with PCA regardless of the opioid used. The typical dosing, lockout interval, and basal infusion parameters are indicated in Table 13.1.

For safety reasons, a continuous background infusion with IV PCA should only rarely be prescribed for spontaneously breathing opioid-naïve patients.31,32 Continuous infusions pose increased risk for respiratory depression.33–35 If a patient becomes sedated, continuing delivery of opioid at a basal rate may cause respiratory depression. Continuous opioid infusion in association with PCA may provide more constant plasma opioid levels and improve analgesia.32 However, other investigators found that addition of a basal infusion rate did not reduce pain, fatigue, or anxiety,31,36 and failed to improve quality of sleep. The number of patient demands, number of supplemental bolus doses, and total opioid use were also not changed in patients receiving basal infusions of opioids. Additionally, most PCA programming errors that have resulted in adverse side effects occurred during the use of basal infusions.35 In selected opioid-tolerant patients with high opioid requirements, a background infusion may be used to deliver the equivalent of the usual opioid dose taken by the patient.12 Use of a background rate of infusion may necessitate higher vigilance and/or increased monitoring of the patient.

The addition of ketamine (an N-methyl-d-aspartate [NMDA] receptor antagonist) to IV PCA solutions may improve analgesia in some, but not all, circumstances. The use of ketamine as a PCA adjunct is biologically attractive for several reasons: NMDA receptor activation is associated with the early development of opioid tolerance, an effect that could be ameliorated by ketamine.37,38 Additionally, NMDA receptor antagonists are inherently analgesic, providing both a (direct) pain-control benefit and an (indirect) opiate sparing effect. Optimization of postoperative IV PCA after spine and hip surgery indicated the ideal ratio of morphine and ketamine to be 1:1, with a lockout interval of 8 minutes.39 However, two studies showed that either ketamine as an adjunct for IV PCA did not improve pain, or that the potential usefulness of ketamine was offset by a high incidence of adverse effects and no opioid-sparing.40,41 One study used a PCA regimen comprising background infusion plus PRN bolus doses of fentanyl/ketamine/ondansetron in patients at high risk of postoperative nausea and vomiting after major spine surgery.42 Although total fentanyl consumption was reduced in the ketamine-PCA group, the severity of nausea was significantly higher, with similar reported pain scores. It is also important to consider the possibility that ketamine can arouse psychomimetic effects and impair cognition.

Clonidine is an α2-adrenoreceptor agonist with analgesic properties. The addition of clonidine to morphine PCA significantly reduced nausea and vomiting in a female population undergoing lower abdominal surgery.43 However, other studies fail to show significant benefits from inclusion of clonidine with IV PCA.44

Dexmedetomidine is a potent, highly selective α2-adrenoreceptor agonist, with analgesic, anxiolytic, and sedative properties, but without effects on respiratory function.45 Perioperative infusion is associated with improved analgesia, reductions in opiate consumption, and less postoperative nausea and vomiting.46 To date, there is one study investigating the analgesic effect of adding dexmedetomidine to morphine IV PCA. Patients received either morphine 1 mg/mL PCA or morphine 1 mg/mL plus dexmedetomidine 5 μg/mL PCA, programmed to deliver 1 mL per demand bolus, with a 5-minute lockout and no background infusion. The addition of dexmedetomidine resulted in superior analgesia, significant morphine sparing, and less nausea. These benefits were achieved without additional sedation or undesired hemodynamic changes.

Morphine Intravenous Patient-controlled Analgesia

When postoperative pain is prolonged, morphine IV–patient-controlled analgesia (IV-PCA) may be used. Many physicians tend to underdose morphine IV-PCA. In healthy patients, use a continuous rate of 1 to 1.2 mg/hr, a patient demand bolus of 1.3 to 1.5 mg, and a lockout time of 8 to 10 minutes, based on the patient's weight and gender (lower weight patients use the lower doses/longer lockout times). Less frequent or lower doses leave the patient in constant pain. We prefer fentanyl IV-PCA in all cases, except for the narcotic-addicted patient.