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OR Nurse:
doi: 10.1097/01.ORN.0000406638.19178.07
Feature: CE Connection

New thinking about postoperative pain management

D'Arcy, Yvonne MS, CRNP, CNS

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Yvonne D'Arcy is a nurse practitioner in pain management and palliative care at Suburban Hospital-Johns Hopkins Medicine in Bethesda, Md.

Pain can influence a patient's satisfaction with the surgical experience. Follow these tips for good outcomes.

The author makes the following disclosures: Consultant, Ortho-McNeil, Pfizer, Endo; Speaker's Bureau, Endo, Pfizer. The planners have disclosed that they have no financial relationships related to this article.

Despite advances in technology and medications, unrelieved postoperative pain continues to be problematic for surgical patients. Statistics indicate that about 43 million patients in the United States experience acute postoperative pain, with pain intensities of moderate to severe reported by 80% of these patients.1 Additionally, about 50% of postoperative patients report unrelieved pain.2

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Patients report that some of the most painful surgeries are intrathoracic surgeries, gastric surgeries, and abdominal surgeries, with pain lasting from 2 to 8 days.3 In a study of 342 patients who had cardiac, abdominal, or orthopedic surgery, 25% to 76% of the patients reported moderate to severe pain.4 Patients also have reported high levels of dissatisfaction when they experience moderate to severe postoperative pain.5 Remember that patients' pain experiences in the immediate postoperative period and through recovery can influence their satisfaction with the surgical experience and hospitalization as a whole.

Nurses who care for surgical patients in perioperative and postoperative settings must understand the need for adequate pain management and look at new ideas and concepts in how to best manage the pain these patients are experiencing. Pain relief should start in the preoperative period where history taking can reveal a patient who has chronic pain or is opioid-dependent. These patients will require much more attention to pain relief after surgery and additional medication to control their postoperative pain.

Trying to determine which patient is most likely to have increased levels of severe pain can be difficult. One postoperative study found that patients who had higher doses of intraoperative sufentanil, general anesthesia, and preoperative treatment with analgesics were positively associated with a higher potential for severe postoperative pain.6 Another study identified preoperative pain, expected pain, surgical fear, and pain catastrophizing (excessive fear of pain) as contributory to increased postoperative pain intensity.7

This article will discuss differences that affect postoperative pain, the use of opioids, and the addition of new medications and techniques to create a multimodal approach to postoperative pain. By learning about the differences in patients and the use of new ideas and techniques, nurses will be able to include some new options and ideas in their postoperative plan of care for pain management.

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Perioperative pain management

The perioperative period consists of time in preadmission testing, preoperative holding, OR, and the postanesthesia care unit (PACU). Each of these areas provides pieces of the pain management plan of care.

* Preadmission. This is the first contact between nurses and surgical patients. Patient information provided at this time—for example, teaching patients how to use a patient-controlled analgesia pump—can be critical to the success of pain management after the surgical procedure.

* Preoperative holding. Information collected by the perioperative nurse at this point is very important for successful postoperative pain management. Using a pain intensity rating scale for measuring preoperative pain levels can help teach the patient how to respond when questioned later about pain intensity. Pain history, pain medication and correct doses, history of any chronic pain, and any history of substance abuse can help clinicians in the postoperative area to better manage a patient's pain.

* OR. Analgesics administered intraoperatively provide the most effective pain control in the OR. Additional factors that can directly affect postoperative pain include positioning and physical injury; the AORN Perioperative Standards and Recommended Practices states that patients should be free from signs and symptoms related to positioning and physical injury during surgery.8

Improper positioning and padding can directly cause an injury that can result in nerve impingement or nerve compression. The incidence of pressure ulcers caused during surgery ranges from 12% to 45%.9 Interventions that can be used to reduce the incidence of pressure ulcer formation include padding bony prominences, monitoring skin integrity, keeping the patient free from pooled liquids, using a lifter to decrease shear, and using pressure-reducing surfaces.

Patients who are morbidly obese and frail older adults with poor baseline skin integrity are at highest risk for pressure ulcer formation or nerve damage during surgery. Older patients will often complain of hip or back pain if kept in a lithotomy position for an extended period of time.

In a legal precedent, a patient whose arms were both extended at 45 degrees during surgery developed painful tingling and numbness in his right hand. The legal findings indicated that the patient's arms weren't positioned correctly and the surgeon had leaned on the patient's right hand during surgery, causing a nerve compression injury.10

* PACU. The patient first becomes aware of surgical pain in the PACU. I.V. bolus doses of an opioid analgesic can be given at this time to make patients more comfortable, and patient-controlled analgesia (PCA) is often started in the PACU once the patient is awake. The American Society of PeriAnesthesia Nurses (ASPAN) Pain and Comfort Clinical Guideline emphasizes the use of medications for pain and nausea; comfort measures such as positioning and application of heat or cold; and the use of multimodal analgesic agents to control pain.11 In the PACU, pain levels are measured frequently and most PACUs require that patients attain a specific comfort level before they're transferred to the surgical unit.

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Postoperative pain: Not one size fits all

Normally the surgical team doesn't see the patient until the day of surgery. The patient comes to the hospital or ambulatory care center with all their comorbid conditions, allergies, preferences, fears, and expectations. Even though most surgeries follow the same technical process, the individuality of the patient can significantly change the outcome of the surgery.

Just as patients having the same procedure can have differences in medication responsiveness, men and women can have different pain experiences and genetic differences can make controlling postoperative pain a challenge. Patients can metabolize pain medications at a rapid rate, moderate rate, or slow rate, and those who metabolize medications rapidly will need large doses to achieve even moderate levels of pain relief. On the other hand, patients who metabolize medications slowly may need only infrequent doses of medication to keep their pain under control, and should be monitored for respiratory depression.

How patients respond to opioids is an individual process. Opioids are classed as mu-agonist drugs, meaning that they produce analgesia when they bind to a mu receptor, often located on the cell membrane in the spinal column. To date, at least 40 or more variations of mu-binding sites have been identified.12 The effect of this variation creates a higher level of analgesia in some patients, if they're genetically predisposed to have a greater affinity for that analgesic. Conversely, if the patient's binding sites are less responsive for binding when an opioid is given, the analgesic effect may be lessened.

No test can determine which patient has better genetic affinity for morphine, hydromorphone, or fentanyl, for example, but some clinical findings have been reported. In one study, 74 patients who had total knee replacements were grouped by genetic morphine sensitivity:

* group one was the AA homozygous morphine -sensitive variant

* group two was a heterozygous morphine sensitive variant (AG)

* group three was GG or nonsensitive morphine variant.

When the morphine PCA use was tracked postoperatively, group one (AA) used 25 mg of morphine in the first 48 hours postoperatively and reported good pain relief, and group two (AG) used 25 mg of morphine and also reported good pain relief. Group three (GG) used 40 mg of morphine, had poorer pain relief, and had many more attempts over injections on the PCA trying to obtain a better level of pain relief.13

Although this is a small preliminary study, it shows that genetics play a part in patient responsiveness to a specific opioid, and that this responsiveness can affect analgesia. Some patients appear to be genetically programmed to have a good response to morphine, compared with other patients.

For many years, women were excluded from research studies on pain related to the fear that varying levels of estrogen would affect the research outcomes. However, now that research has been done on the differences between pain in men and women, it seems the researchers may have been correct in some of their assumptions.

Pain is a different experience for men and women. Women in general have a lower tolerance and threshold for pain, and men have a greater response to analgesics.14 Men respond better to mu-opioid analgesics; women respond to either mu- or kappa-binding medications such as mixed agonist-antagonist drugs like pentazocine. One of the reasons that opioid effect is different between men and women is that estrogen has been found to decrease the number of mu-receptor sites for opioid binding.15

The composition of women's bodies changes the way that some analgesics are processed; for example, on average, women have a higher percentage of body fat, so lipophilic medications such as fentanyl can react differently, and patients may need repeated dosing to maintain pain relief. In the postoperative period, women are more likely to develop adverse reactions to opioids, such as respiratory depression and nausea.16

Research is uncovering more about how genetics affect pain relief medications. In the meantime, recognizing each patient's needs will help nurses focus on assessing the patient's response to opioids and responding appropriately in spite of individual differences.

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Treating postoperative pain

Opioids are used to manage postoperative pain, and are most commonly given I.V. because patients in the immediate postoperative period aren't taking food orally. The one delivery method that isn't recommended is I.M. injection because medication absorption can't be regulated and the tissue in the injection site can scar.17,18 Postoperative opioids typically are provided via PCA pump, giving patients more independence in administering a preset dose of medication as soon as it's needed.

Consider PCA as a process rather than just a machine that delivers medication. The PCA process comprises the PCA machine, prescription for medication delivery, medication, and patient; if one of these elements isn't present or is faulty, the process will fail. The human component of this process also includes the nurse who must program the pump correctly and monitor the patient, the pharmacy staff who must deliver the correct medication with the correct concentration, and the prescriber who must be knowledgeable about writing PCA prescriptions.

For maximum effect, patients will need to receive loading doses to provide immediate comfort. They should then be reminded to begin their own bolus doses to maintain their comfort level.

PCA safety is critical for perioperative nurses. In a quality study, misprogramming errors accounted for 71% of the adverse events, 15% were related to human factors causing over- or undermedication, and 9% were related to equipment problems.19 The Joint Commission and the Institute for Safe Medication Practices (ISMP) have made significant recommendations for PCA use for postoperative pain (see Tips for using PCA safely). Even opioid-tolerant patients can become oversedated if opioid doses are high enough. One of the most dangerous adverse effects of PCA use is respiratory depression.

The rate of respiratory depression with PCA is between 0.19% and 5.2%.20 Risk factors for respiratory depression include the use of a basal infusion; age greater than 70; obesity; sleep apnea; concurrent use of central nervous system depressants; upper abdominal or thoracic surgery; renal, hepatic, pulmonary, or cardiac impairment; and a PCA bolus greater than 1 mg morphine without a basal rate.20

Recommendations for nurses caring for at-risk patients on PCA include:

* monitoring respiratory rate and sedation levels every 1 to 2 hours in the first 12 to 24 hours postoperatively for opioid-naïve patients

* including respiratory rate, depth, and rhythm in the sedation assessment

* monitoring oxygen saturation

* more frequent monitoring during nighttime hours.20,21

Techniques for monitoring oxygenation for patients on PCA include pulse oximetry (SpO2) and capnography, which measures end-tidal carbon dioxide (ETCO2) levels. Although pulse oximetry is more commonly used in acute care settings, capnography is gaining in popularity, as it presents a more accurate picture of increasing respiratory depression determined by rising CO2 levels.

One drawback of pulse oximetry is that supplemental oxygen use can alter the accuracy of the oximetry readings; the patient may actually have a lower oxygenation percentage than the readings indicate. Recent recommendations are to use both pulse oximetry and capnography, which can give more accurate and complete information about patients than either when used alone.22 Using pulse oximetry and capnography means the nurse can intervene before oxygen saturation becomes dangerously low (below 85%) or CO2 rises too high (above 45 mm Hg).22

Epidural use in acute care has decreased because many patients who have total joint replacements now receive PCA with peripheral nerve catheters using a local anesthetic. Epidural pain management is recommended for patients who have thoracic or large abdominal surgery, and for patients undergoing major orthopedic surgery. The epidural catheter is placed just outside the spinal canal in the epidural space. Once the catheter is placed, a combination of local anesthetic and an opioid such as fentanyl is infused using a pump similar to an I.V. PCA. Patient-controlled epidural analgesia (PCEA) lets patients administer a bolus dose when they need to be active or if pain levels increase. Epidural analgesia can provide the largest amount of pain relief with the smallest amount of opioid—this is why this pain management modality is used for major surgeries and the sickest, more fragile patients.14

Monitoring patients on epidural analgesia requires assessing pain and adverse effects such as pruritus or nausea, as well as evaluating motor strength in the area that the epidural is serving. If the catheter is placed in the lumbar epidural space, monitor patients for motor weakness in the lower extremities to ensure that the neural blockade hasn't become too dense and is affecting muscle strength. For all patients on PCEA, assess for muscle impairment before walking or transfers.

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New options

Using a multimodal approach to pain management after surgery is strongly recommended to produce better outcomes.17,23 Adjuvant medications such as gabapentin, ketamine (administered I.V.), and regional pain management techniques such as peripheral nerve catheters can be added to other forms of analgesia to enhance pain management.

The antiepileptic drugs gabapentin and pregabalin limit neuronal calcium influx by blocking reuptake at the synaptic junction. This decreases neuronal firing and the release of pain-facilitating substances such as substance P.24 Gabapentin is indicated as adjunctive therapy to treat partial seizures in epilepsy and the pain of postherpetic neuralgia. Pregabalin is indicated as adjunctive therapy for partial seizures as well as for the pain of postherpetic neuralgia, fibromyalgia, and diabetic neuropathy. A new use, currently off-label, is to treat acute pain after surgery and trauma by preventing the creation of central sensitization (increased sensitivity in the brain to pain signals).

A systematic review of 22 randomized controlled trials indicates that a single dose of gabapentin (300 mg to 1,200 mg) given 1 to 2 hours preoperatively can reduce opioid use by 20% to 62%.24 Long-term pain relief was a more varied outcome and gabapentin's effect was reduced after 12 hours in one trial only. As an indication of improved pain control, in two of the studies, patients who received preoperative gabapentin made their first requests for postoperative analgesia later than those who didn't receive preoperative gabapentin. When gabapentin administration was continued postoperatively, patients had a positive difference between pain relief with the active drug and placebo.24

Medications such as gabapentin and pregabalin reduce pain and opioid use, and also reduce some of the more troublesome opioid adverse effects, such as nausea, vomiting, and urine retention. The major drawback to using these medications is sedation and dizziness.

Ketamine, an N-methyl-D-aspartate (NMDA) antagonist and anesthetic agent, can be used as an adjunct to opioids to modulate central sensory processing. Ketamine is thought to prevent NMDA-mediated sensitization of spinal cord dorsal horn neurons. Reviews of this drug are mixed. The variability of results may be due in part to the dosing or timing of drug administration.25 Ketamine also has significant adverse effects, including hallucination, nightmares, and amnesia.

A study of 143 patients undergoing prostatectomy compared pain intensity and opioid use by PCA. Researchers found that pain and opioid use didn't differ among the three study groups even at 2 weeks to 6 months.26 In a systematic review of 37 studies, ketamine use was recommended as a small-dose adjunct to opioids, and was found to be safe and useful for decreasing opioid consumption.27

A newer regional anesthesia technique, peripheral nerve blocks, has been found to be especially effective in orthopedic patients. The use of these catheters can extend the effect of a nerve block for up to several days; combining a peripheral nerve block with PCA can provide very effective pain relief. (For more on this topic, see Understanding peripheral nerve blocks in the September issue of OR Nurse 2011.)

Peripheral nerve block catheters are often connected to a small softball-sized reservoir that delivers medication at a preset rate for a predetermined period of time. These devices can be set up as a soaker hose configuration along either a surgical incision for localized pain relief or a nerve such as the femoral nerve. The medication in the reservoir is a local anesthetic alone, most commonly bupivacaine or ropivacaine. As the medication infuses, the ball collapses and the catheter can be removed.

Patients who had joint replacement surgery and were given peripheral nerve blocks for postoperative pain reported superior pain relief, earlier mobilization, fewer adverse reactions, and higher patient satisfaction.28–30 A meta-analysis of 19 studies with opioids and peripheral nerve blocks found that the combination of a peripheral nerve block and opioids provided superior pain relief no matter where the catheter was placed, resulted in reduced opioid use, and fewer opioid-related adverse reactions.31

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Adding in complementary therapies

The use of complementary and alternative techniques for additive pain management has become popular in the acute care setting. (Integrative therapy refers to complementary and alternative techniques as part of the total plan of care.) Aromatherapy, massage, and relaxation techniques can help decrease the anxiety and stress of surgery. Distraction can also decrease pain by taking the patient's mind off of the pain and redirecting it to something interesting, such as TV or crossword puzzles. Pain guidelines from the American Pain Society, ASPAN, and American Society of Anesthesiologists all recommend combining nonpharmacologic options for pain relief with medication management.11,17,23 Patients prefer using techniques that can reduce pain, aren't medications, and have no possibility of sedation or adverse reactions such as constipation.

Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacologic pain relief option that patients can easily try. Apply electrodes near peripheral nerves or close to the site of surgery. TENS uses a mild electric current that passes over the area with high-frequency pulses; this activates gamma-aminobutyric acid (GABA), a pain-inhibiting substance, and activates spinal opioid receptors to reduce nociceptive transmission. Low-frequency TENS is thought to release endorphins, substances that function like endogenous opioids.32

Studies with patients who had herniorrhaphy, laparoscopic abdominal surgery, cardiac surgery, and thoracotomy all had positive results that included reduced pain, improved pulmonary function, and reduced need for opioids when TENS was used.30 Because TENS is noninvasive, it's easy to discontinue if the patient doesn't feel it's helping manage pain.

Music is a fairly simple technique that can be used with almost any patient to provide increased pain relief, distraction, and relaxation. Patients can be given portable players and can select their preferred style of music. A study of 517 patients who selected their preferred type of music and used it either alone or combined with jaw relaxation exercise found that pain was decreased and sleep enhanced.33

In another meta-analysis of 170 patients and 138 controls, music-assisted relaxation provided a better quality of sleep for patients with a variety of conditions.34 Using music therapy doesn't require a lot of equipment or investment. Tapes or discs can be reused and portable players can be provided to patients for use during hospitalization and recycled. One important aspect of using a technique such as music and relaxation is that there are no adverse reactions such as nausea or constipation.

Although these are just a few of the possible complementary therapies for adjunct pain relief, the data do indicate a place and need for these techniques. Many are simple and easy to use, with benefits that far outweigh any extra effort needed to use them.

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Special patient populations

Older patients and patients who are opioid-tolerant are at risk for being undertreated for pain after surgery. In general, older patients are able to tolerate opioids, but because of physiologic age-related changes (such as decreased muscle to fat ratio) they may need dose adjustments and more careful monitoring.35 Nurses caring for older patients should be aware that they have the potential for increased complication rates during and after surgery.36

For older patients, always perform a complete pain assessment and make sure that the patient is able to see and hear you. Use a behavioral pain assessment scale for patients who are nonverbal, cognitively impaired, or unable to provide a self-report of pain. When choosing an opioid medication for an older patient, consider these recommendations:

* Try to use shorter-acting medications to minimize adverse reactions.

* Use dose reductions of 25% to 50% to decrease the potential for oversedation.

* Monitor the older adult more frequently to determine if the dose is too high or is causing adverse reactions. Remember that older adults have decreased renal excretion and liver changes that can affect medication metabolism.

* Avoid propoxyphene, meperidine, pentazocine, indomethacin, and amitriptyline because of toxic metabolites and adverse reactions.37

For patients who have chronic pain and are opioid-tolerant, surgery may create some special concerns.

* Have patients take their usual doses of opioid medications before surgery.

* Medication doses may have to be increased by 25% to 50% related to the patient's postoperative pain report.

* Try to be nonjudgmental and encourage a therapeutic relationship so that the patient and the nurse can work toward mutually beneficial pain goals.38

Care for older patients and patients who take opioids regularly may be more time-consuming, but these patients can achieve adequate postoperative pain relief safely and progress to a timely discharge.

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Finding the right mix

Using a combination of treatment options, medications, and techniques, nurses can improve the level of postoperative pain relief for surgical patients.

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Tips for using PCA safely14,39–41

For PCA use to be as safe as possible, The Joint Commission and the ISMP recommend:

* Selecting patients who are good candidates for PCAs. Infants and confused patients aren't good candidates for PCA use.

* Eliminating PCA by proxy (that is, letting someone other than the patient push the PCA button); educate patients and their families on PCA use and reinforce that only the patient should push the PCA button.

* Using standard prescription sets and standardized medication concentrations.

* Requiring nurses to maintain proficiency with PCAs, know how to enter a prescription correctly, and use independent nurse checks to confirm dosages.

* Checking PCA pump setting at least once every 4 hours.

* Monitoring patients who are on PCA carefully to assess for adverse effects or other conditions (such as pulmonary embolism) that mimic oversedation.

* Using a sedation scale such as the Ramsay scale to monitor sedation levels consistently.

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© 2011 Lippincott Williams & Wilkins, Inc.