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PATIENT INSTRUCTIONS

CASE 8-14, QUESTION 3: J.A. is nervous about giving herself an overdose while using PCA. What instructions should

be provided to her?

Patients often worry about the safety of PCA, which can lead

to reluctance to provide themselves with adequate pain relief.

J.A. should be informed that she will be frequently assessed by

the nurse (particularly during the first 24 hours of therapy). If she

becomes sleepy from the opioid, she should not press the button.

When this adverse effect of the opioid has worn off, she will wake

up (plasma opioid level has fallen back into or below the therapeutic range) and she may then press the button to receive a dose

of the opioid if she has pain. This is an important safety feature of

PCA and is the reason family members must not push the button

for the patient. However, J.A. should also know that she may have

to press the button several times (after the lock-out interval has

passed) before her pain is relieved. She must also be informed

that she may require a larger PCA dose, so it is important for

J.A. to assess her pain relief from her current (“usual”) dose that

most patients are initially started on after surgery. Accurate pain

assessment after her prescribed dose is critical for ensuring that

her dose is sufficient to provide the desired level of analgesia. She

should also understand the possible adverse effects of her PCA

medication and what can be done to prevent and treat these

effects, as well as the advantages of providing herself with adequate analgesia (e.g., early ambulation). Finally, she should be

told of the negligible risk of narcotic addiction from short-term

PCA use and be given ample opportunity to ask questions.

CHOICE OF AGENT

CASE 8-14, QUESTION 4: Meperidine is ordered for J.A.’s

PCA. Is this a reasonable drug choice for her?

Ideally, opioids for PCA administration have a rapid onset and

intermediate duration of action (30–60 minutes), with no accumulation or adverse effects. The physicians, nurses, and pharmacists involved with the care of the patient should be familiar

with the drug selected for PCA. Morphine is by far the most

common choice for PCA, although other opioids such as fentanyl and hydromorphone can be used. Drug choice is based

on past patient experiences, allergies, adverse effects, and special

considerations, such as renal function. Meperidine has a metabolite, normeperidine, which is renally excreted, has a long halflife, and can cause cerebral irritation and excitation. Symptoms

of CNS toxicity from normeperidine include agitation, shaky

feelings, delirium, twitching, tremors, and myoclonus or tonicclonic seizures. These symptoms can be seen when meperidine

is administered in higher doses or for a prolonged period.111

The presence of renal insufficiency increases the risk of accumulation of normeperidine.111 Meperidine also inhibits serotonin

reuptake and has a fairly high serotonergic potential. The risk

of a patient developing the serotonin syndrome is greater when

meperidine is coadministered with another drug that has moderate or high serotonergic potential (e.g., fluoxetine, fluvoxamine,

paroxetine, venlafaxine).112 For these reasons, meperidine is a

poor choice for analgesia, particularly for J.A. who has diminished renal function. Morphine is conjugated with glucuronide

in hepatic and extrahepatic sites (particularly the kidney) to its

two major metabolites, morphine-3-glucuronide and morphine6-glucuronide; both metabolites are excreted primarily in the

urine. Morphine-6-glucuronide is an active metabolite that can

accumulate in patients with renal failure, resulting in prolonged

analgesia, sedation, and respiratory depression.113 Because of

169Perioperative Care Chapter 8

TABLE 8-12

Adult Analgesic Dosing Recommendations for Intravenous Patient-Controlled Analgesiaa,102,114,115

Demand Dose (mg)

Drug Usual Concentration Usual Range Lock-Out Interval (minutes)

Fentanyl (as citrate) 10 mcg/mL 0.01–0.02 0.01–0.04 10

Hydromorphone hydrochloride 0.2 mg/mL 0.2–0.3 0.1–0.4 10

Morphine sulfate 1 mg/mL 1–2 0.5–2.5 10

aAnalgesic doses are based on those required by a healthy 55- to 70-kg, opioid-na¨ıve adult. Analgesic requirements vary widely among patients. Doses may need to be

adjusted because of age, condition of the patient, and prior opioid use.

J.A.’s diminished renal function, morphine should probably be

avoided because other options exist. Hydromorphone is not

metabolized to an active 6-glucuronide metabolite, and fentanyl

is metabolized to inactive metabolites. Either hydromorphone

or fentanyl is an appropriate analgesic choice for J.A. Hydromorphone is chosen. Table 8-12 lists common doses and lock-out

intervals for drugs administered by PCA.102,114,115

DOSING

CASE 8-14, QUESTION 5: J.A. was not receiving an opioid before surgery (e.g., she is opioid na¨ıve). What dose of

hydromorphone and what lock-out interval should be used

for her initial PCA pump settings?

If J.A. is experiencing pain before PCA has been initiated,

she should receive a loading dose of IV hydromorphone titrated

to achieve baseline pain relief (may require up to 1 mg). Once

adequate analgesia is achieved, demand doses of 0.2 mg with

a lock-out interval of 10 minutes would be a good choice to

maintain analgesia for this opioid-na¨ıve patient. If J.A.’s pain is

not relieved after two to three demand doses within 1 hour, the

demand dose can be increased to 0.3 mg.

USE OF A BASAL INFUSION

CASE 8-14, QUESTION 6: After the first postoperative

evening, J.A. tells you that she had a terrible time sleeping.

She describes waking up in pain frequently, despite pressing

her PCA button many times. She rates her pain as moderate to severe in intensity and fairly constant. A review of

the history on her PCA device reveals successful delivery of

9 mg of hydromorphone (30 demand doses, 0.3 mg each)

during the past 12 hours. J.A. is not sedated and reports no

adverse effects from hydromorphone. How can J.A.’s pain

management be improved?

Many PCA infusion pumps offer a continuous infusion setting for a basal infusion during intermittent dosing. Use of a basal

(continuous) infusion has not been shown to improve analgesia

and likely increases the risk of adverse effects (owing to the potential of an opioid overdose in some patients). Therefore, routine

basal (continuous) infusion of opioids cannot be recommended

for acute pain management. In an opioid-na¨ıve patient such as

J.A., however, continuing to increase the demand dose increases

the risk of excessive sedation and respiratory depression (owing

to high peak levels). Also, J.A. describes her pain as moderate to

severe in intensity and fairly constant in nature when she does not

regularly push the demand button. For J.A., a continuous infusion

could be beneficial. As a rule of thumb, an opioid-na¨ıve patient

experiencing acute pain (that can change quickly) should receive

no more than one-third of her average hourly usage as a continuous infusion or a maximum of 1 mg/hour of morphine (or its

equivalent, which would be 0.2 mg/hour for hydromorphone).

For J.A., a continuous infusion of 0.2 mg/hour hydromorphone

should be initiated in addition to her demand dose of 0.3 mg

every 8 minutes. Because the onset of action of hydromorphone

is about 5 minutes and the peak effect occurs in 10 to 20 minutes,

shortening the lock-out interval is not recommended because

J.A. could access the next dose of hydromorphone before the

effects of the initial dose can be appreciated. That could lead to

dose-stacking and significant adverse effects, such as excessive

sedation and respiratory depression.

ADVERSE EFFECTS

CASE 8-14, QUESTION 7: The next day, J.A. requested only

a few demand doses and reports adequate pain relief with

her PCA, but now complains of feeling slightly groggy and

nauseated. Bowel sounds are noted on physical examination, and J.A. plans to try to take clear liquids later that

morning. What are the adverse effects of PCA opioids, and

how can J.A.’s complaints be addressed?

Opioids can produce sedation, confusion, euphoria, nausea and vomiting, constipation, urinary retention, and pruritus.

These adverse effects can be managed by dose adjustments or

pharmacologic intervention. Although rare, life-threatening respiratory depression is the most serious adverse effect of opioid

administration.110 Because sedation precedes respiratory depression, systematic assessment of sedation and respiratory parameters should be performed at frequent intervals (every 1 to

2 hours during the first 24 hours of therapy). The patient should

be observed for how quickly he or she arouses when stimulated, and the rate, depth, and regularity of the patient’s respirations should be assessed and compared with the patient’s baseline

status.110,114 Particular attention must be paid to patients at high

risk for respiratory depression from an opioid. These risk factors

include age older than 65 years, obesity, pulmonary disease or

other conditions that reduce ventilatory capacity, and known or

suspected history of sleep apnea.114 Technical problems must also

be ruled out. The PCA pump should be checked to ensure that it

is delivering the correct drug and dose, programming should be

checked for accuracy (e.g., drug concentration, dosing interval),

and the opioid reversal agent naloxone must be readily available. Monitoring for efficacy and adverse effects of PCA therapy

should include pain intensity and quality, response to treatment, number of on-demand requests, analgesic consumption,

BP, heart rate, respiratory rate and effort, and level of sedation,

as well as the presence of other adverse effects of opioids such as

nausea and itching.

J.A.’s PCA hydromorphone dose could be reduced to manage

her sedation and nausea. However, her pain control must be

carefully reassessed to ensure efficacy of the newly lowered dose.

An order for a nonsedating antiemetic (such as ondansetron)

could also be provided. NSAIDs (ketorolac IV or other NSAID

170 Section 1 General Care

orally) or acetaminophen (IV or oral) are not sedating; thus, they

should be added to the analgesic regimen to provide analgesia and

allow a reduction in her opioid dose. However, because of J.A.’s

compromised renal function, acetaminophen is a better choice

than an NSAID. If J.A. is able to take fluids orally, PCA should

be discontinued and oral analgesics administered as needed. As

healing occurs, her pain intensity should lessen, and oral opioid–

acetaminophen products should manage her pain adequately.

EPIDURAL ANALGESIA

CASE 8-15

QUESTION 1: T.M., a 69-year-old man, enters the surgical ICU after surgery for colorectal cancer (lower anterior

resection, urethral stents, ileorectal pull-through). His pain

is managed through a lumbar epidural catheter. What are

the benefits and risks of epidural analgesia, and why was

this approach to postoperative analgesia chosen for T.M.?

ADVANTAGES AND DISADVANTAGES

Epidural analgesia can offer superior pain relief compared with

traditional parenteral (IM, IV, and IV PCA) analgesia116 as well as

facilitate return of GI function, decrease pulmonary complications, and possibly decrease cardiovascular events.117,118 Epidural PCA offers an advantage compared with parenteral opioids

(including IV PCA) because it allows individualization of the

analgesic requirements, lower total drug use, greater patient

satisfaction,119 and improved analgesia.120 Epidural catheter

placement is an invasive procedure that can result in unintentional dural puncture (causing postdural puncture headache),

insertion site inflammation or infection, catheter migration, and,

rarely, epidural hematoma.115

PATIENT SELECTION