Patient Safety Tip of the Week
June 10, 2014
Another Clinical Decision Support Tool to Avoid Torsade de Pointes
Last month ISMP
Canada did a safety bulletin on a suspected preventable death due to a known
drug-drug interaction (ISMP
Canada 2014). The case involved an elderly woman admitted with fever and
presumed pneumonia. Prior to admission she was on citalopram 40 mg. daily, an
anticoagulant, an antihypertensive, and nonprescription supplements. Initial
antibiotics were ampicillin and gentamycin but these were later switched to
azithromycin and ceftriaxone. She subsequently suffered a series of syncopal spells and a cardiac arrest. She had a markedly
prolonged QT interval and was also hypokalemic. The citalopram and azithromycin
were discontinued. She ultimately died. It was felt she had a prolonged QT
interval syndrome secondary to citalopram and azithromycin that contributed to
her death.
The article
discusses the literature on the QT interval-prolonging effect of both
citalopram and azithromycin and notes the effects may be additive. They note
the warnings on both drugs that have been disseminated by both Health Canada
and the US FDA. They note 2 potential points for intervention: (1) when the
pharmacy processed the order for azithromycin and (2) when the prolonged QT
interval was first noted.
In several of our prior
columns (see list at the end of today’s column) we’ve discussed the risks of
developing ventricular tachycardia and, specifically, Torsade de Pointes in
hospitalized patients with prolonged QT intervals. There are a number of
reasons why this syndrome is more likely to both occur and result in death in
hospitalized patients. Hospitalized patients have a whole host of other factors
that may help precipitate malignant arrhythmias in vulnerable patients. They
tend to have underlying heart disease, electrolyte abnormalities (eg. hypokalemia, hypomagnesemia, hypocalcemia), renal or hepatic
impairment, and bradycardia, all of which may be precipitating factors. More
importantly they may have the sorts of conditions for which we prescribe the
drugs that are primarily responsible for prolonging the QT interval (eg. haloperidol, antibiotics, antiarrhythmic agents, etc.).
And many of those drugs are given intravenously and in high doses in the
hospital as compared to the outpatient arena. Rapid intravenous infusion of
such drugs may be more likely to precipitate Torsade de Pointes than slow
infusion.
In our previous
columns we provided a number of steps your organization should be taking to
minimize the risks in such cases. We’ve recommended use of clinical decision
support systems (CDSS) and computerized alerts as an important step. No one
could possibly remember all the drugs that can prolong the QT interval. For
a full list of drugs that commonly cause prolongation of the QT interval and
may lead to Torsade de Pointes, go to the CredibleMeds™ website. That site also has a list of
drugs that prolong the QT interval and might possibly cause Torsade de Pointes
and another list of drugs that have conditional risk (eg.
only when combined with other drugs).
Hence, the need for other tools to help alert the clinician that a drug he or
she is about to order might prolong the QT interval. In our April 9, 2013 Patient
Safety Tip of the Week “Mayo
Clinic System Alerts for QT Interval Prolongation” we discussed one such
CDSS tool that had been implemented at the Mayo Clinic (Haugaa
2013).
Now another new
study has demonstrated that use of CDSS and computerized alerts can reduce the
risk of QT interval prolongation (Tisdale
2014). One of the most important considerations is developing a system in
which the risk of alert fatigue is minimized. We know from multiple studies
done in the past that physicians override over 90% of computer alerts during
CPOE (computerized physician order entry). To minimize the risk of alert
fatigue and still accomplish your goal of reducing the risk to patients it is
important to (1) deliver the alert to the right person (2) deliver alerts only
for the most potentially serious events and (3) provide alternative options for
the physician’s response.
They system developed and implemented by Tisdale and
colleagues did all three. First, the alerts first went to the pharmacist, who
would then evaluate the situation and decide whether discussion with and
recommendations for the physician were appropriate. Second, the thresholds to
trigger the alerts were set at levels expected to minimize alert fatigue. And,
third, the pharmacist responding to the alert would present the physician with
some options for actions.
After reviewing extensive data on prior patients in their
CCU’s and reviewing the literature, the researchers opted to trigger the alert
when the QTc interval was >500 ms
or there was an increase in QTc of ≥60 ms from baseline. Their system also identified through the
electronic medical record multiple other conditions or laboratory results that
identified patients at higher risk for QT interval prolongation.
After implementation
of the CDSS system the found a significant reduction in the risk of QT
prolongation (odds ratio 0.65). In addition, they found a significant reduction
in the prescription of non-cardiac drugs known to prolong the QT interval
(especially fluoroquinolone antibiotics and intravenous
haloperidol).
Overall, 82% of
alerts were overridden. That still compares favorably to the frequency with
which other alerts are overridden. Most of the overrides were for cardiac drugs
(eg. amiodarone or other
anti-arrythmic drugs). The authors point out that
overriding the computer alert did not mean that nothing was done. For example,
even though the order for the drug may have been overridden the pharmacist and
physician may have modified some other risk factor (eg.
corrected an electrolyte disturbance or stopped another medication) or
increased the frequency of QTc surveillance.
We recommend you read our previous columns listed below for
suggestions on what your organization should be doing. Since many of the risk
factors in hospitalized patients are potentially modifiable or avoidable it is
imperative that we put into place systems that will help early identification
of patients at risk.
Some of our prior
columns on QT interval prolongation and Torsade de Pointes:
June 29, 2010 “Torsade
de Pointes: Are Your Patients At Risk?”
February 5, 2013 “Antidepressants
and QT Interval Prolongation”
April 9, 2013 “Mayo
Clinic System Alerts for QT Interval Prolongation”
References:
ISMP Canada. Preventable Death Highlights the Need for
Improved Management of Known Drug Interactions. ISMP Canada Safety Bulletin
2014; 14 (5): 1-7 May
14, 2014
http://www.ismp-canada.org/download/safetyBulletins/2014/ISMPCSB2014-5_KnownDrugInteractions.pdf
CredibleMeds™ website.
Haugaa KH, Bos
JM, Tarrell RF, et al. Institution-Wide QT Alert
System Identifies Patients With a High Risk of Mortality. Mayo Clin Proc 2013; 88(4): 315-325
http://download.journals.elsevierhealth.com/pdfs/journals/0025-6196/PIIS0025619613000712.pdf
Tisdale JE, Jaynes HA, Kingery J, et al. Effectiveness of a Clinical Decision
Support System for Reducing the Risk of QT Interval Prolongation in
Hospitalized Patients. Circulation: Cardiovascular Quality and Outcomes 2014;
published online before print May 6, 2014
http://circoutcomes.ahajournals.org/content/early/2014/05/06/CIRCOUTCOMES.113.000651.abstract
Print “PDF
version”
http://www.patientsafetysolutions.com/