MS. G, AGE 67, a retired office clerk, was admitted to her local hospital for an abdominal hysterectomy. On admission, she reported a history of hypertension, type 2 diabetes mellitus, and chronic obstructive pulmonary disease (COPD). She also reported that she smokes about 1.5 packs of cigarettes per day, as she has for the past 50 years (75 pack-year history). Ms. G is obese, with a body mass index (BMI) of 31.9. Recently diagnosed with obstructive sleep apnea, she was prescribed continuous positive airway pressure therapy for use at night. Her history was negative for the use of any controlled substances or illicit drugs. Ms. G's surgical procedure was uneventful. After several hours in the postanesthesia care unit (PACU), she returned to her room. Her SpO2 was 98% on supplemental oxygen via nasal cannula at 2 L/min. She was receiving lactated Ringer's solution infusing at 125 mL/hr and morphine via a patient-controlled analgesia (PCA) pump for postoperative pain management.
Using this hypothetical case as an example, this article reviews the latest information on how best to care for postoperative patients receiving PCA to manage their pain. By illustrating some common pitfalls of PCA use, this case study highlights safe practice recommendations for use of PCA and opioids in hospitals offered by The Joint Commission (TJC), the Institute for Safe Medication Practices (ISMP), and the American Society for Pain Management.1-3
Post-op pain management: Headed for trouble
To control her pain, Ms. G received an initial loading dose of morphine in the PACU and was then begun on PCA. Her pump was programmed to deliver a continuous basal rate of morphine plus a demand dose that she could self-administer at prescribed intervals as she needed it to manage her pain.
In her room, a drowsy Ms. G and her attentive family were educated about PCA by her nurse. After being instructed that only the patient was to push the button to administer the morphine, they indicated that they understood the instructions.
During the first hours after surgery, Ms. G's vital signs were within normal limits. She slept at long intervals but was arousable and cooperative when her vital signs, surgical site dressing, and peripheral venous access were assessed. Her self-reported pain intensity ratings ranged between 3 and 5/0-10. When nurses checked her PCA pump at 4 hours post-op, they found that 16 additional demand doses had been administered.
At 8 hours post-op, after the family had gone home, the unlicensed assistive personnel heard the pulse oximeter alarm, entered Ms. G's room, and rang the call bell. The responding nurse found the patient unresponsive with a respiratory rate of 6/minute and an SpO2 of 82%. She immediately turned off the PCA, supported the patient's airway, activated the rapid response team, and called for a bag-valve mask (BVM).
When the team arrived, Ms. G was being ventilated with the BVM. Her BP was 90/44 with a pulse rate of 56. She remained unresponsive and bradypneic. The team determined that Ms. G's respiratory depression was caused by her opioid infusion. Undiluted I.V. naloxone was quickly administered. Ms. G immediatedly opened her eyes and began to scream with pain.
How could this situation have been prevented or better managed?
Appreciate the risks
PCA is a medication delivery system that lets patients self-administer predetermined doses of opioid medications through a venous access device. PCA infusion pumps were developed and introduced into hospitals in the 1970s and, since then, have become a popular intervention to manage postoperative pain. About 13 million patients receive PCA annually.4 Patients using PCA report improved pain relief, greater patient satisfaction, less sedation, and fewer postoperative complications.5
Although PCA has provided effective postoperative pain management for decades, it poses significant risks, including a 0.5% risk of respiratory depression or arrest.1 PCA errors represent a four-fold higher risk to patients than other reported medication errors.2 TJC reports that causes of adverse events include lack of knowledge about potency differences among opioids, administration of multiple opioids by different modes, and inadequate monitoring of patients receiving opioids for pain relief.1
Medication knowledge: The key to safety
Opioid medications are frequently administered via PCA pumps. Pharmacologically, opioid agonists bind to the mu receptor sites along the ascending pain pathways in the brainstem and spinal cord to inhibit the transmission of pain impulses, decreasing the perception of pain.6 Mu receptors, however, also play an important role in regulating respiratory rate and depth; when the opioids bind to the mu receptors, they impair normal ventilatory effort and have the potential to depress respirations.7 The FDA has issued boxed warnings describing respiratory depression as a potential risk for those receiving opioids for pain relief.6
The opioids used for PCA include morphine and hydromorphone, and, less commonly, fentanyl. Although opioids work similarly and are similarly effective for pain management, they have very different potencies. For example, the equianalgesic doses of I.V. morphine, hydromorphone, and fentanyl are 10 mg, 1.5 mg, and 0.2 mg, respectively.8 TJC reported that 47% of opioid-related adverse drug events reported to their sentinel event database from 2004 to 2011 were wrong-dose medication errors.1
Assessing whether a patient is opioid-naive or opioid-tolerant is important in predicting how the patient may react to opioid medications. The FDA describes opioid-tolerant patients to be those who have been taking, for a week or longer, at least 60 mg of morphine daily, or at least 30 mg of oral oxycodone daily, or at least 8 mg of oral hydromorphone daily, or an equianalgesic dose of another opioid.9 Patients who are opioid-naive are expected to be more susceptible to the effects of opioid medications than those who are opioid-tolerant.
Naloxone, an opioid antagonist, is the antidote for opioid-induced respiratory depression. This drug also has a high affinity for mu receptors and successfully competes with and displaces opioids at the receptor sites. This action quickly blocks opioid binding and reverses all opioid effects, including analgesia.10 When given I.V., the onset of action is 2 minutes or less, with a duration of action of 45 to 60 minutes. This is an important consideration because the duration of action of naloxone is shorter than that of most opioids. Because of the possibility of resedation, patients receiving naloxone to reverse the effects of opioids should be continuously monitored for a minimum of 2 hours after the last dose of naloxone.6,11
When naloxone is administered to a patient who is hypotensive, hypovolemic, and/or was experiencing severe pain or stress prior to treatment, a rapid or high-dose infusion of naloxone can cause a sudden catecholamine-mediated sympathetic nervous system response, which may result in cardiac dysrhythmias and vasoconstriction. The vasoconstriction may lead to a fluid shift from the systemic circulation to the pulmonary bed, resulting in pulmonary edema.7 In patients who are physically dependent on opioids, naloxone may precipitate an acute withdrawal syndrome. In postoperative patients, abrupt reversal may also result in a significant reversal of the opioid's analgesic effects, causing acute post-op pain as in Ms. G's case.10
Identify high-risk patients
The best patient care begins with a comprehensive assessment and recognition of risk factors. TJC and the American Society for Pain Management have identified characteristics of patients who are at a high risk for oversedation and respiratory depression and recommend routine screening for these factors in patients undergoing surgical procedures.1,3 Risk factors include:
- sleep apnea or sleep disorder diagnosis
- morbid obesity (BMI greater than 40)
- older than age 55
- no recent opioid use (opioid-naive)
- upper abdominal or thoracic surgical procedures
- concurrent use of other sedating drugs (such as antihistamines, benzodiazepines, or sedatives)
- preexisting pulmonary or cardiac disease or major organ failure
- increased opioid dose requirements
- extended time under general anesthesia.
Identifying patients at high risk for potential opioid-induced adverse reactions allows nursing staff to plan for additional monitoring.
Monitor patients carefully
After initiation of PCA, patients must be assessed frequently to monitor the effects of treatment because most critical events occur within the first 24 hours after surgery.12 The ISMP cautions that patients should be monitored more frequently at night because incidences of opioid-induced respiratory depression are reported to be more common between 0000 (midnight) and 0600.2
Vital signs, pain intensity rating, and level of sedation should be assessed per institutional policies and procedures and individualized according to the patient's postoperative clinical status and response to treatment.1 The San Diego Patient Safety Taskforce recommends obtaining vital signs as follows:13
- at baseline
- at initiation or with change in drug: every 15 minutes for 1 hour, every hour for 4 hours, then every 2 hours
- with every change in dose and after each bolus dose: every hour for 4 hours, then every 2 hours
- in case of an adverse event or deterioration in patient's clinical status: every 15 minutes for 1 hour, every hour for 4 hours, then every 2 hours
- at any hand-offs or shift changes.
Pain and sedation assessments
Pain should be assessed using a standardized pain intensity rating scale or tool, such as the numerical rating scale.
Assessing the patient's level of sedation is critical because sedation generally precedes respiratory depression, offering an opportunity for intervention if it's detected early.2 As with pain, sedation should also be assessed using a standardized scale, such as the Ramsey Sedation Scale, Pasero-McCaffery Opioid-induced Sedation Scale, or the Richmond Agitation-Sedation Scale (RASS). (See Using the RASS.)
The RASS is preferred by many institutions because it's concise and simple to use, and it combines sedation and agitation into one scale.2,13 Institutional policy should include clear guidance about which levels of sedation would indicate the need to intervene (such as increase monitoring frequency, discontinue PCA, or notify the prescriber).2
Because opioids depress respiratory function in the central nervous system, respiratory assessment is an essential element of patient monitoring. Respiratory assessment should include an evaluation of respiratory rate and quality. Parameters should include the following:2,13
- respiratory rate, counted for a full minute
- depth (normal, shallow, deep)
- pattern of respirations (regular, irregular)
- quality of respiratory effort (effortless/comfortable, labored)
- breath sounds (clear, decreased, adventitious).
The routine use of pulse oximetry (SpO2) monitoring to measure changes in patient oxygenation is recommended, especially if the patient is at risk for respiratory depression. Oximetry readings, however, are late indicators of respiratory depression because values may remain near normal for several minutes after the patient stops breathing. This technology should be part of a comprehensive assessment process rather than a substitute for frequent and thorough respiratory assessment.1,2,12
Recently, capnography, a noninvasive continuous way to measure the partial pressure of exhaled carbon dioxide (CO2), has been found to be a valuable addition to pulse oximetry in the management of patients receiving PCA.14 Researchers have documented that increases in a patient's end-tidal carbon dioxide (ETCO2) measurement provide an early indication of hypoventilation and CO2 retention.14,15 One meta-analysis found that respiratory depression was 28 times more likely to be detected in a sample of patients monitored by capnography than in the patient controls who weren't.14
Postoperative patients may experience signs and symptoms reflecting adverse reactions to the opioid prescribed for pain, the anesthesia they received, or the surgical procedure itself. Adjuvant treatments for nausea, pruritus, and agitation include phenothiazines, sedative-hypnotics, and antihistamines. When taken with opioids, these medications may produce additional sedation and contribute to the development of respiratory depression, necessitating even more frequent patient monitoring.16
Use standardization and safe technology
To reduce potential medication errors, TJC recommends creating and implementing policies and procedures to address the safe administration of opioids and use of PCA.1 Strategies such as using standard drug concentrations, order sets, and drug administration protocols limit treatment options to those accepted as standard of care and reduce opportunities for confusion and error.13 Modifications should be made to order sets and protocols to reflect changes in best practices. For example, since 2009 the ISMP has recommended against basal infusions in opioid-naive patients because the risk of respiratory depression in patients receiving basal doses plus PCA is at least five times greater than in patients receiving PCA doses only.17 To further enhance patient safety, the ISMP and TJC recommend that two nurses independently check all prescriptions for PCA with the pump settings to ensure the correct medication is selected and the pump is programmed or reprogrammed correctly.18
The development of new “smart pump” technology has also been shown to help decrease PCA adverse events.19 Several medical device companies are marketing PCA pumps with integrated capnography, which monitors both SpO2 and ETCO2. When the pump senses repetitive patterns of oxygen desaturation, climbing ETCO2, and apnea, it alerts caregivers.
As with all medications they administer, nurses are challenged to ensure that the right patient receives the right medication via the right route at the right dose and right time.13 Medication safety strategies such as tall man lettering (for example, HYDROmorphone), and barcoding can also help to prevent errors.1,13 Pharmacists should use conversion systems to calculate correct doses of opioids when converting from one medication to another or from one route of administration to another (for example, from oral to I.V.). Nurses should consult with pharmacists when questions arise.1
Educate patients and staff
Lack of effective patient education has been a factor in many errors involving PCA. Ideally, patients should be educated preoperatively for their postoperative use of PCA and be carefully instructed about the dangers of PCA by proxy. Patients and their families should understand the relationships between having pain, pushing the button, and achieving adequate pain relief.18 They should know to alert nursing staff if they experience inadequate pain control or adverse reactions to medications, need help getting out of bed, or have any other safety concerns. Patients should expect to be awakened frequently so that staff can properly assess them.13
Post-op, nursing staff should regularly reinforce instructions. TJC mandates that printed instructions be provided to patients, families, and caregivers about opioid medications, including their expected and adverse reactions, potential risks (such as tolerance and addiction), interactions, and safe storage and disposal.1
Staff education should focus on maintaining patient safety. Nurses caring for patients using PCA should be adequately trained in use of the PCA pump. Training should include identification of patient risk factors, patient monitoring responsibilities, and education about opioid administration. This includes how to assess patients for adverse drug reactions, recognize advancing sedation, and adjust the plan of care based on the patient's risk profile.1
Manage respiratory depression effectively
Standard order sets addressing the administration of PCA with opioid medications should include actions to be taken if respiratory depression occurs. Most sources agree that a respiratory rate of 8 to 10 breaths/minute or less is an indication of distress and that action is indicated. The following protocol is a composite of best practices found in the literature.3,13,20,21
Suspect respiratory depression if the patient has:
- a respiratory rate of 8 to 10 breaths/minute or less
- shallow respirations, poor respiratory effort, and noisy respirations
- depressed mental status
- oxygen desaturation or increasing ETCO2.
Take the following actions:
- Stop the PCA infusion immediately but maintain a functional venous access device.
- Arouse the patient immediately and remind him or her to “take a deep breath.”
- Consider supplemental oxygen.
If the patient arouses (RASS = -2 [light sedation]) but requires brief physical stimulation or repeated verbal reminders to stay awake:
- Notify the healthcare provider for a prescription to hold PCA for 1 hour and/or decrease the dose.
If the patient is experiencing severe sedation (RASS = -3 to -5 [moderate sedation to unarousable]) with respiratory rate less than 8 breaths/minute or if the patient is experiencing apnea or imminent respiratory arrest:
- Stop the opioid.
- Provide ventilatory support with BVM and supplemental oxygen as needed to maintain effective ventilation.
- Administer naloxone per facility protocol until respiratory rate is above 10 breaths/minute and the patient arouses easily.
- Attempt to minimize total reversal of analgesia, especially in postoperative patients and patients at the end of life, by administering diluted I.V. naloxone every minute as per facility policy and procedure until the patient is responsive.16,17
- Monitor cardiovascular status.
- Notify the healthcare provider.
Back to the patient
Let's return to the case of Ms. G to identify avoidable PCA pitfalls. Ms. G was at great risk for respiratory depression: She was obese, a long-term smoker, older than age 55, and diagnosed with obstructive sleep apnea and COPD. She underwent a surgical procedure under general anesthesia that involved an abdominal incision. The education regarding her postoperative management was incomplete and took place after the surgery while she was still under the influence of anesthetic medications. She was opioid-naive and received successive doses of an opioid medication postoperatively in addition to a basal opioid infusion, which isn't appropriate for an opioid-naive patient. She'd been using positive pressure airway therapy at home, but wasn't using it in the hospital. Had the staff caring for Ms. G recognized she was at increased risk for respiratory depression on admission, they could have planned for more careful postoperative observation when her family left her unattended.
When Ms. G was found to be experiencing respiratory depression, the staff was quick to come to her aid. The sudden reversal of the opioid by the rapid administration of the full dose of naloxone, however, left her in severe pain and at great risk for serious adverse reactions, including massive catecholamine release that could have resulted in pulmonary edema and death. For the next few hours, benzodiazapines and nonsteroidal anti-inflammatory medications were used to manage her discomfort until the effects of the naloxone dissipated.
Nurses play an important role in identifying patients at risk for opioid-induced respiratory depression, performing ongoing assessment and monitoring of patients during PCA, and initiating prompt interventions to prevent the worsening of adverse events.3 Keeping up to date on best practices and the latest recommendations of patient safety organizations enables nursing staff to better predict, prevent, and if necessary manage this life-threatening postoperative complication.