More on avoiding opiate toxicity
with PCA by proxy
From the May 29, 2002 issue
PROBLEM: A 72-year-old woman underwent cancer surgery
and her surgeon prescribed patient controlled analgesia (PCA)
with a 2 mg morphine loading dose and 1 mg every 10 minutes
prn (6 mg maximum per hour). Initially, the patient was restless
and agitated in the post anesthesia care unit, but she remained
obtunded after surgery. Despite the patient's inability to verbalize
pain, nurses pushed the PCA button and delivered frequent doses
of morphine over the next 48 hours. Subsequently, the patient
suffered a cardiorespiratory arrest and seizure, leading to
hypoxic encephalopathy. She died several months later without
ever regaining consciousness. In our March 3 and March 20, 2002
issues, we warned about the risk of overdosing patients when
family members or clinicians activate PCA for patients (PCA
by proxy). With patient controlled analgesia, there's
a built-in safety feature to avoid toxicity because a sedated
patient will not push the PCA button. We also noted that nurse
controlled analgesia may be appropriate in critical care settings
if patient selection protocols have been established and appropriate
assessment tools are in place to guide the level of pain and
sedation. But in the case above, the patient was not an appropriate
candidate for PCA and proper assessment tools were not used
to guide nurse controlled analgesia. This patient was
at risk for morphine toxicity because she was obtunded, obese,
and had compromised lung capacity (COPD). Although vital signs
were recorded periodically (oxygen saturation monitoring was
not used), nurses did not recognize the signs of morphine toxicity
and they continued to administer the analgesic despite serious
hypotension and very shallow respirations.
SAFE PRACTICE RECOMMENDATION: To reduce the risk of
overdoses with PCA, consider the following:
- Establish selection criteria for PCA and nurse
controlled analgesia. While PCA can be used for a wide range
of patients to safely manage pain (not agitation or restlessness),
some patients are unsuitable candidates due to level of
consciousness, psychological reasons, or limited intellectual
capacity. Also identify the types of patients who may be
suitable for nurse controlled analgesia. Establish risk
factors (age, weight, preexisting conditions, concomitant
medications, etc.) that would require increased monitoring.
Periodically reassess the appropriateness of therapy at
regular intervals.
- Develop protocols and standardized order sets to
guide the selection of drugs, dosing, lockout periods, and
infusion devices. Avoid using meperidine (risk of neurotoxicity),
and if hydromorphone is used, ensure proper dosing based
on narcotic equivalents. Also prohibit the use of other
analgesics while PCA is being administered.
- Carefully monitor patients. Opiates, even at therapeutic
doses, can suppress respiration, heart rate, and blood pressure,
so the need for monitoring and observation cannot be overemphasized.
Pay particular attention to the first 24 hours and at night
since the effects of opiate analgesics on intellectual functioning
are not entirely predictable and nocturnal hypoxia can be
a serious side effect. Monitoring parameters should include
regular clinician assessment of vital signs, alertness,
pulse oximetry or capnography, and patient self-reported
pain using a consistent pain scale. If support staff takes
vital signs, a clinician should review the information as
soon as available. If continuous pulse oximetry or capnography
is not available for all patients, use it for those with
heightened risk of toxicity and when nurse controlled analgesia
is employed.
- Require two clinicians to independently double check
patient identification and PCA device dose settings prior
to use (and each pump refill) to detect possible errors.
- Educate patients and families about the proper
use of PCA (start during pre-op testing visit). Warn family
members and staff about the danger of pressing the button
for the patient, except when the patient requires physical
assistance and has clearly expressed the need and desire
for a bolus of medication.
- Educate staff about proper use of PCA. Encourage
clinicians to critically think about the cumulative dose
that the patient could receive if the maximum dose limits
were given. Also ensure that they fully understand the hazards
of using analgesics. With so many tragic events related
to analgesics, perhaps it's time to run simulations for
medical teams where "actors" purposely misuse
analgesics (write incomplete orders; select an inappropriate
drug, dose, or method of administration; misprogram a pump;
ignore double checks; forget critical monitoring points;
miss obvious signs of toxicity; etc.) so that the teams
can identify and stop the at-risk behaviors.
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