Patient Safety Tip
of the Week
May 8, 2018 Heparin Overdose
It’s been 10 years since we had lots of headlines about
deaths related to inadvertent overdosing with heparin. Most of the cases
discussed back then pertained to accidental use of high-dose heparin “flushes”
in children and infants (see the list of prior columns at the end of today’s
column).
A recent report from the California Department of Public
Health (CDPH
2018) brings the heparin issue back into the spotlight. A patient with
chronic renal failure requiring dialysis was admitted with altered mental
status, worsening renal failure, and a clotted A-V fistula. She was sent to the
Interventional Radiology Department for a procedure to declot the A-V fistula.
During the procedure she received 25,000 units of heparin diluted in a 250 milliliter bag of saline. She subsequently developed
internal bleeding that led to her death.
The CDPH report notes that a physician asked for a heparin
drip in a pressure bag. The nurse said she asked the physician “do you want
25,000 units in a 250 milliliter bag of saline?” and he
responded “yes”. The nurse connected the IV tubing to the 250
milliliter bag of concentrated heparin and the physician manually
controlled the rate of infusion with a roller clamp. No double checks were
performed. The nurse later stated she did not think the physician intended to
infuse the entire bag, otherwise she would never have “spiked” it (connected
the IV tubing to the bag).
After the procedure a radiology technician showed the empty
bag to a second nurse, who recognized that this was a much higher dose of
heparin than usually used. Apparently, the normal dose for this procedure is
1,000 units of heparin in 500 milliliters of saline. That nurse informed the
other nurses, the physician, and the radiology technician of the situation.
Upon return to the ICU the patient was noted to have
bleeding from her arm and lab studies revealed a prolonged PTT and that her
hemoglobin had dropped from 10 to 5.9. The patient subsequently died of
hypovolemic shock.
In a subsequent interview with the CDPH, the physician
recalled the nurse asking if he wanted a heparin drip but did not recall
discussing the dosage. He recalled answering “yes, heparin in saline” and that
his usual practice was to use 500 units of heparin per liter of saline for the
drip.
The CDPH report and hospital response focus largely on the
fact that no double check was performed before the heparin dose was
administered. The hospital’s policy did call for a double check of IV heparin
doses by two qualified health care professionals. A second RN was expected to validate
and document the correct dosage. But in this case there
was no double check by either another nurse or the physician.
The hospital’s plan of correction (POC) did focus on the
issue of double checks, requiring that checks be done by two qualified health
care professionals for all high-alert medications (of which heparin is one).
Double checks do have problems of their own (see our October 16, 2012 Patient Safety Tip
of the Week “What
is the Evidence on Double Checks?”) but note that we still consider double
checks to be an action of intermediate strength worth using in multiple
situations, particularly for all high-alert medications. But they need to be
truly “independent” double checks.
But there are several other factors that contributed to this
adverse event. First, and foremost, this was a verbal order. Verbal orders are prone to error (see our January 10, 2012 Patient Safety Tip of
the Week “Verbal
Orders”). Verbal orders should only be used in emergency
circumstances or in circumstances where it is impractical for a physician to
enter the order. When verbal orders are used, there must be “readback” where the nurse receiving the
order specifically reads back all the information pertinent to dosing. That did
not happen in this case. In fact, this was really
a “reverse verbal order”! Though the physician had requested a heparin
drip, it was really the nurse who initiated the specific order. Hence, the
required “readback” would have fallen to the physician.
The fact that the whole process really took place verbally
also bypassed several patient safety tools we use in medication safety. No
order was placed in a CPOE system, which could have provided clinical decision
support tools to ensure proper dosing. Also, the lack of input into an IT
system precluded use of a barcoding system that also could have served as
another line of defense against medication error.
Remember, this event took place in an interventional
radiology suite. Not all hospitals have all their individual units connected to
the hospital-wide electronic medical record and, hence, do not have integration
with tools like barcoding and CPOE with clinical decision support. In some
cases, it is truly a lack of IT integration, In
others, it is a matter of culture.
In this hospital’s POC, they began using an upgrade of their
EMR in the interventional radiology area and cath lab. This included a one-step
medication order entry section and a section for documentation of
administration. It requires entry of concentration for all high-alert
medications. They note the physician can review all in one screen.
We’ve also pointed out in other columns the tendency to
consider heparin not as a medication, particularly when heparin “flushes” are
being used to keep IV lines open. Unfortunately, that cavalier attitude to
heparin is all too widespread.
And then there is the question we always ask
“why are formulations of such high-dose,
concentrated heparin available on the unit in the first place?”. Does the
interventional radiology unit do any procedures that would require such high-dose,
concentrated formulations? If not, such formulations should be available only
in the pharmacy, so that staff on the units cannot inadvertently administer
overdoses. This is akin to the old problem of patients dying from injection of
concentrated potassium chloride on patient care units. That problem was only
solved when we removed vials of concentrated KCl from units other than the
pharmacy. In this hospital’s POC their Pharmacy did an audit of medication
cabinets in the Angio Lab and removed all 25,000 units/250 milliliter heparin
bags. They also now have Pharmacy affix a high-alert double check sticker on
all 25,000 units/250 milliliter heparin bags.
Removal of the high-dose formulations from “floor stock” is
what we consider a strong intervention. It fits in the category of a constraint
or forcing function, which are the strongest action steps (see our March 27, 2012 Patient Safety Tip of the Week
“Action
Plan Strength in RCA’s” and our slide show “Weak
vs. Strong Responses to an RCA”).
Have you done an inventory to ensure you have no “floor
stock” of high-dose heparin formulations? And are all your units, including
your OR and radiology and procedural units, integrated with your EMR or at
least have their own IT systems that utilize CPOE, clinical decision support,
and barcoding?
Perhaps the biggest lesson from the California case is that
facilities are still vulnerable to this sort of preventable error.
See some of our prior
columns on inadvertent heparin overdoses:
December 2007 “1000-fold
Heparin Overdoses Back in the News Again”
May 2008 “UK
NPSA Alert on Heparin Flushes”
July 15, 2008
“Heparin
Flushes.....Again!”
References:
CDPH (California Department of Public Health). 2018. Intake
Number CA00512428. Accessed April 21, 2018
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