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Safety issues with adding lidocaine
to IV potassium infusions
From the February 12, 2004 issue
Problem: A physician prescribed three sequential IV potassium
chloride infusions of 40 mEq in 250 mL bags for a patient with
severe hypokalemia. Each bag was to be given over 4 hours. Soon
after starting the first bag, the patient complained of burning
pain at the infusion site. Following hospital policy, the physician
then prescribed 25 mg of lidocaine to be added to each subsequent
bag of potassium chloride to reduce vein discomfort. A nursing
supervisor went to a night drug cabinet and selected what she
thought were six (three for each remaining bag) 1 mL ampuls
of 1% XYLOCAINE MPF (lidocaine, 10 mg/mL). However, she
accidentally picked out six polypropylene plastic ampuls of
Xylocaine MPF (10 mg/mL Polyamp DuoFit), 10 mL each (100 mg).
These ampuls are designed for needle-free systems and have twist-off
caps that are compatible with Luer and tapered syringes (photo
appears in the PDF format). The nursing supervisor handed the
ampuls to a staff nurse and told her to add the contents of
2 ½ ampuls to each subsequent IV bag. This introduced
an element of confirmation bias, and the nurse simply followed
her supervisor’s directions without recognizing that she
was adding 250 mg (25 mL) of lidocaine to each bag, not 25 mg.
Thus, the patient received 500 mg of lidocaine over the course
of the night. Fortunately, the patient had a pacemaker; so even
if adverse effects occurred, they were suppressed. Under different
circumstances, an adverse effect from lidocaine toxicity could
have resulted.
The hospital attributed the error, in part, to unclear labeling
of this newer form of Xylocaine packaging. In fact, other
reporters have complained about how similar these are to respiratory
therapy products in low-density polyethylene (LDPE) plastic,
and how difficult it is to read the label if the ampul is
removed from its original packaging. The label information
is in black print, which is hard to read in poor lighting
or when the opaque, colorless plastic ampuls are held against
a dark background.
In addition to the above incident, we’ve received a
report in which regular insulin was added to a potassium infusion
instead of lidocaine. Multiple bags were prepared this way,
resulting in recurrent hypoglycemia before error discovery.
We also heard about a case in which a nurse added potassium
chloride to a bag of lidocaine, instead of the reverse. Adding
to the confusion, lidocaine is available in a variety of different
formulations (e.g., with and without preservatives or epinephrine,
in 1% and 2% concentrations). Although rare, an allergic reaction
to lidocaine is also possible.
Safe Practice Recommendation: Certainly, poor labeling
played a part in this error. If Xylocaine MPF (Polyamp DuoFit)
ampuls are available at your practice site, they should remain
in their overwraps until immediately before use to better
communicate the amount of drug contained in each. The quantity
of 10 mL lidocaine ampuls available in floor stock is also
an issue. Had fewer ampuls been available in the night cabinet,
the supervisor might have taken a second look at the amount
needed for a dose, or called a pharmacist. Another crucial
factor: adding lidocaine to a potassium chloride infusion
should be a function carried out in the pharmacy whenever
possible.
More to the point, however, is the need to ask this basic
question: Do the benefits of adding lidocaine to potassium
chloride infusions outweigh the risks? All of the safety issues
raised above need to be weighed carefully. Keep in mind, any
time an extra step is added to a process - in this case, adding
an additional drug - it introduces the potential for errors.
In the past, we’ve discouraged adding lidocaine to IV
potassium infusions because it might mask infection or vein
injury that presents as phlebitis. We suspect that it could
also mask symptoms of a potassium chloride overdose by preventing
the burning sensation that characteristically occurs along
the vein.
There are just a few studies that have shown improved patient
tolerance to potassium administered through peripheral veins
with the addition of lidocaine. Lim et al.(1) found the use
of lidocaine effective in a group of 28 patients when it was
given as a 3 mL bolus prior to infusion of 20 mEq of KCl in
100 mL of 5% dextrose. Pucino et al.(2) also found lidocaine
effective in reducing pain in a study of 18 hypokalemic patients
who received infusions of KCl 20 mEq in 65 mL of diluent,
with and without lidocaine 50 mg. However, the number of patients
in these studies is small, and the methods used are not comparable.
Effectiveness depends on the rate of infusion, drug concentration,
and site of infusion. Thus, it isn’t surprising that
respondents to an informal survey found lidocaine ineffective
and had opted for alternatives such as: optimizing oral replacement;
increasing potassium dilution; slowing the IV rate; lowering
the solution’s osmolality; splitting and administering
the dose in less concentrated solutions via two veins simultaneously;
and employing a safe, rational, standardized protocol with
replacement parameters that include access via a large bore
vein as appropriate.
References: (1) Lin ET et al. Efficacy
of lignocaine in alleviating potassium chloride infusion pain.
Anaesth Intensive Care 1993; 21:129.
(2) Pucino F et al. Patient tolerance to
intravenous potassium chloride with and without lidocaine.
Drug Intell Clin Pharm 1988; 22:676-9.
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