The Lowdown on
Hospital Blood Sugars
April 2004 Cover Story CAP Today
by
Karen Titus
Say
hello to the latest wonder drug-insulin.
It can reduce morbidity and mortality in critically ill patients.
It tackles sepsis head-on. It's cost-effective and can reduce
length of stay. It's got nurses begging to perform more
point-of-care testing. How crazy is that?
More
specifically, tight-really tight, tighter than you ever thought
possible-glycemic control of patients in ICUs, maintained by
hourly bedside glucose monitoring and IV insulin infusions, is
transforming the hospital landscape, undoing generations of
training and practice and exploding the myth that for critically
ill patients, high blood sugars are just fine, thank you very
much. Researchers are taking aim, with numerous studies either
recently completed or underway. And late last year experts issued
the first-ever guidelines for managing in-hospital blood sugar
levels.
These
changes are nothing short of revolutionary, say endocrinologists.
But like most revolutions, it's been a long time in the making.
The change should have come sooner, say many.
"We always
knew, in our heart of hearts, that it was a bad idea to let
patients' sugars be high in the hospital," says David Baldwin, MD,
acting director, endocrinology, Rush University Medical Center,
Chicago. "We would work to keep sugars well controlled in the
hospital, but there was never an institutional or programmatic
approach to it."
"We've
always known to keep sugars low," agrees Irl Hirsch, MD, professor
of medicine, University of Washington School of Medicine, Seattle.
The real issue, he says, was a lack of outcomes data, which they
needed to convince highly skeptical colleagues.
The DIGAMI
(Diabetes and Insulin-Glucose Infusion in Acute Myocardial
Infarction) study should have provided that data. Published in the
late 1990s, in a series of articles, it broke new ground but fell
short of touchstone status. "They took 600 patients having an
acute MI, and they randomized them to either really intensive
glucose control with intravenous insulin versus letting them have
the standard care they'd always gotten in the past," Dr. Baldwin
says. The researchers showed a 30 percent reduction in mortality
in patients whose blood sugar levels were tightly controlled with
IV insulin. "That was striking. But years later, that still had
not become the standard of care anywhere in the world, for reasons
that are just unclear."
It's
possible the DIGAMI trial was disregarded because it was novel.
"It stood by itself," Dr. Baldwin says. "There was nothing else
out there that showed this kind of approach would be beneficial."
The study
also was assailed by critics who rightfully pointed out it tried
to do too much. In the active treatment arm, patients not only had
their glycemic levels tightly controlled in the hospital via
intravenous insulin, but also for at least three months after
discharge, during which they received daily insulin injections to
maintain normal levels. The obvious question arose: What was
responsible for saving lives, the IV insulin or the subcutaneous
insulin? Both?
Or was it
something entirely different? As Dr. Baldwin points out, many of
the patients in the study were diabetics who were already taking
oral antidiabetic agents—including one pill associated with
cardiac toxicity. "Maybe some patients who got insulin got better
because they were no longer taking the pills that may have been
harmful," he says.
A second
DIGAMI study now underway should address the shortcomings of the
first one. The newer study is larger and delineates those
receiving IV and subcutaneous insulin from those who receive only
the in-hospital infusions; it's also looking more carefully at the
types of oral agents patients may be taking. "So they're doing it
in a bigger and hopefully more definitive way," says Dr. Baldwin.
"Because their first study, even though the results were very
clear, had enough question marks that it could never have the
impact that they hoped it would-and that it deserved to have."
Back
to top
That impact would have to wait until 2001.
November 11,
2001, to be exact, when another stand-alone trial appeared. Unlike
the DIGAMI study, however, this one is staring down all
challengers.
"Everything
started in November 2001," says Dr. Baldwin, referring to the
publication of "Intensive Insulin Therapy in Critically Ill
Patients" (N Engl J Med. 2001; 345: 1359-1357) by Greet
Van den Berghe, MD, PhD, et al. "It was a real sentinel article
for this whole field, a huge wake-up call" that has since sent
physicians in an "amazing new direction of focusing our attention
on controlling blood sugar in inpatients."
The
researchers, noting that hyperglycemia and insulin resistance are
common in critically ill patients, embarked on a one-year study
involving 1,548 adults in the surgical ICU who were receiving
mechanical ventilation. Patients were randomly assigned to receive
intensive insulin therapy (maintaining blood glucose between 80
and 110 mg/dL) or conventional treatment (insulin infusion only if
the blood glucose level exceeded 215 mg/dL, maintaining a level
between 180 and 200 mg/dL).
The
intensive therapeutic approach reduced mortality during ICU stay,
from eight percent with conventional treatment to 4.6 percent with
the tighter control. The greatest reduction in mortality involved
deaths due to sepsis-related multiple-organ failure. Intensive
therapy reduced overall in-hospital mortality by 34 percent,
bloodstream infections by 46 percent, acute renal failure
(requiring dialysis or hemofiltration) by 41 percent, the median
number of red-cell transfusions by 50 percent, and
critical-illness polyneuropathy by 44 percent. Patients whose
blood glucose levels were tightly controlled were also less likely
to need prolonged mechanical ventilation and intensive care.
The results
gave endocrinologists a flag to rally around. "Their study was
totally inspirational for thousands of other people," Dr. Baldwin
says. "You could never say enough about how important it was."
Here at last was solid data showing physicians that a different
approach worked.
"I've
noticed over the years that many of our surgical patients get
infections of their wounds after surgery, seemingly in association
with blood sugars that are quite high after surgery, but I'd never
been able to do much about it," Dr. Baldwin says. A big part of
the problem, he says, was simply trying to persuade his
non-endocrinologist colleagues to consider the link. "They want to
know, Where's the proof? Where's the study that really shows it's
going to make a difference? And there really wasn't one."
Dr. Hirsch
calls the Van den Berghe study the biggest, most important
randomized study to look at the importance of tight glycemic
control. "It did two things: It made people look at what they were
doing in the hospital, but it also made people look at the other
evidence that was already out there."
Back
to top
Until the Van den Berghe study started shaking
things up, in-hospital glycemic control had been a rather clumsy
affair.
For decades
physicians have used a sliding scale to evaluate insulin levels
and administration. "Of course, that's really silly, because
you're treating what happened in the last four hours, but doing so
in the next four hours," says Harrison G. Weed, MD, associate
professor, internal medicine, Ohio State University. "You're
treating the past instead of the future." That approach doesn't
benefit patients and can be dangerous.
At the
University of Washington School of Medicine, physicians moved away
from the sliding-scale approach to an insulin infusion protocol in
1991. "We were very much in the minority," Dr. Hirsch says. The
shift wasn't prompted by outcomes data—because there wasn't any.
"It was based on safety," Dr. Hirsch says. "Because when you look
at how we train residents in the hospital, we don't do a good job
of teaching them how to manage diabetes. Disasters were just
waiting to happen, simply because people were so intimidated by
the use of insulin."
Certainly
hypoglycemia is nothing to sneeze at. But that fear has made
physicians fainthearted when it comes to insulin, and their dread
has been passed along to residents and medical students for years.
"What we've done is taught people how to avoid insulin for as long
as possible," says Dr. Hirsch. "If you look at the big, giant
studies in the United States, you'll see that the average patient
starts insulin with an average A1C of 10.4 percent,
because we're trying to avoid insulin use—even though it may have
been indicated years earlier."
"People are
afraid," says Kwame Osei, MD, professor of medicine and exercise
physiology and director of the Division of Endocrinology,
Diabetes, and Metabolism at OSU.
Trying to
fight that has been a tall order. "The typical American doctor is
happy enough if the sugars are in the 200s," says Dr. Baldwin.
"'200, that's OK. 300s, that's maybe too high. 100s—uh-oh, I'm a
little worried, maybe it's too low.' That was always the fear of
the general doctor—'Oh my God, the sugar's going to go too low,
they're going to crash.'"
That sort
of thinking has been especially hard on ICU nurses, who typically
have had to try managing their patients with only the vaguest of
orders. Dr. Baldwin gives a classic example: Start IV insulin
infusion if the sugar goes above 200, and titrate to keep the
sugar less than 200. "That would be the entire order. So the poor
nurse had no guideline. You were pretty much telling her 'Fly by
the seat of your pants.'" As a result, sugars were reflexively
kept around 200 by nurses afraid to go lower.
Given all that, the idea of keeping
ICU patients' blood sugar levels between 80 and 110 mg/dL is
nothing short of shocking. Think of it as insulin's four-minute
mile.
When Dr.
Baldwin began rolling out new insulin infusion protocols at Rush
two years ago, 110 mg/dL seemed a little scary even to him. "Our
target is between 80 and 120—because 110 made me nervous at the
time. But now, looking back, we could easily do 110. It's no big
deal."
"Our nurses
are not afraid of it at all anymore," he continues. "But you can
be sure they started out afraid, as did all the doctors."
Starting
with the surgical ICU, Rush began instituting an insulin infusion
protocol April 1, 2002, making it mandatory for all patients who
had undergone any type of cardiovascular surgery, as well as for
all organ transplant patients. Since they were acting primarily on
the Van den Berghe study, Dr. Baldwin and his colleagues chose to
have their early efforts take the form of research studies, so
they could collect their own data and determine whether it
confirmed her results.
Within six
months, Dr. Baldwin reports, the protocol had spread to nearly all
other surgical patients, primarily through nurses and the rotation
of residents into different teams throughout the hospital. "The
nurses in the neurosurgical unit heard about it through the
grapevine, and then they came to me and said, 'We want this too.
We're tired of bad glucose control.' So we taught them, and they
got it up and running," he says. About eight months ago the
protocol was put into place in the medical ICU. "It's been a
gradual thing creeping through the institution," he says. "Once
the nurses start doing something, the residents catch on."
The nurses
love the protocol, he says, even though it means they're
performing more bedside tests. "It means they can safely have the
sugars be running totally in the normal range, which is something
that was totally foreign to them. ICU patients' sugars never run
in the normal range, or at least had not up to then."
This summer
the protocol will take another leap, when Rush will begin using it
for every patient with a myocardial infarction and elevated blood
sugar. "The stress of having a heart attack often makes your
sugars go up, whether you're diabetic or not," Dr. Baldwin
explains. When that takes hold, every ICU at Rush will be using
the protocol.
Back
to top
In
Washington, Dr. Hirsch and his colleagues adjusted their approach
in summer 2002, using a protocol published by Lawrence J.
Markovitz, MD (Endocr Pract. 2002; 8: 10-18). (It's also
published in an article coauthored by Dr. Hirsch: J Clin
Endocrinol Metab. 2003; 88: 2430-2437). They have not yet
published their data, "but we feel it's very safe, and it's
adaptable to someone with any type of diabetes on any floor in the
hospital," Dr. Hirsch says. "In fact, we use that protocol on
every floor except psychiatry."
When Dr.
Baldwin and his colleagues analyzed the data from their first
year's use of the protocol in the SICU, they found them to be "a
little disappointing," he says. In the heart patients, "we did not
find any change in the rate of infections compared to the year
before, when only about half the patients got insulin and the
sugars were not nearly as low."
But he
remains convinced of the protocol's usefulness, and chalks up the
less-than-dramatic results to the relatively small patient
population they evaluated?. "I think we weren't able to show a
difference because we're looking at events that happen only one,
two, three percent of the time," he says. "You need a large number
of patients before you can show a statistically significant
difference."
They did
find that atrial fibrillation, a common complication after
open-heart surgery, dropped by about 30 percent, and postsurgical
infection rates dropped in the transplant patients.
Other,
larger studies may bolster his views. A study by Anthony Furnary,
MD (J Thorac Cardiovasc Surg. 2003; 125: 1007-1021),
involving more than 3,000 patients over 10 years showed that
giving perioperative insulin drips to coronary artery bypass graft
patients who are diabetic reduced in-hospital mortality as well as
infections, Dr. Baldwin reports.
The Van den
Berghe study recently had its first confirmation, presented at the
Society of Critical Care Medicine's annual meeting in Orlando in
late February. James Krinsley, MD, director of critical care at
The Stamford (Conn.) Hospital, reported that using an intensive
protocol in a medical-surgical ICU, aimed at maintaining levels
between 80 and 140 mg/dL, resulted in a six percent reduction in
in-hospital mortality, for a relative risk reduction of 29
percent. The year-long study compared 800 consecutive admissions
with 800 historical controls. "The data showed almost exactly the
same thing as what Dr. Van den Berghe showed in 2001," says Dr.
Hirsch. "So I don't think any of this is fluke." (Dr. Krinsley
also published a study in Mayo Clinical Proceedings
[2003; 78: 1471-1478], involving 1,826 ICU patients with a wide
range of medical and surgical diagnoses, that showed hyperglycemia
increased the patient's chance of death.)
In addition
to the second DIGAMI study, Dr. Baldwin points to a large,
multicenter study underway in England, the GIST study (Glucose
Insulin in Stroke Trial), which is looking at tighter glycemic
control in patients with acute stroke. "There's a lot of indirect
data that indicate if you let patients' blood sugars be high when
they're having a stroke, that the extent of the permanent damage
to their brain is far greater than if you gave them insulin right
away and kept their sugars normal," he says.
More
immediately, there are new guidelines on managing blood sugars in
hospitalized patients, whether diabetic or not. The guidelines
emerged from a consensus conference held in December that was
sponsored and attended by "every possible interested party of
doctors, nurses, and specialties," Dr. Baldwin says. The
guidelines are available on the Web site of the American
Association of Clinical Endocrinologists (www.
aace. com/). In addition, the February issue of Diabetes
Care (http://
care. diabetesjournals. org/ content/vol27 / issue2/ index.shtml)
contains a technical review (authored in part by Dr. Hirsch) of
the literature from which the guidelines were derived. "It's the
bible on the subject," says Dr. Baldwin.
The
guidelines can be summed up in two numbers: 110 and 180, the
former being the maximum for all ICU patients, and the latter the
maximum for all non-ICU hospitalized patients. "Below 180 is the
target for the postprandial glucose level for those patients who
are eating," Dr. Hirsch clarifies. "Before eating, the number is
110." With these guidelines, says Dr. Baldwin, the whole mentality
that OK'd higher levels "has been formally written off."
Back
to top
The
how-low-can-you-go limbo
dance is likely to continue. "The line between abnormal and normal
has been drifting down," says Dr. Baldwin. "And it may very well
go down in the future as we learn more." Though 80 is likely to
remain the low range of normal, the upper range is definitely in
flux, he says.
It's only a
matter of time before other institutions see the light. "We're
going to see change," Dr. Hirsch says, if for no other reason than
fear of litigation. "What has driven a lot of hospitals is the
threat of disaster and, quite frankly, the attorneys. And I know
of two hospitals in the last year where there have been deaths
from sliding-scale insulin." He adds that the December consensus
conference included a representative of the JCAHO, and while it's
difficult to say how the guidelines will be translated into
hospital accreditation, "the fact they were there suggests to me
that there will be greater emphasis on appropriate diabetes care."
Tight
controls will also spread well beyond the ICU. Dr. Baldwin is
particularly excited about a recently published study in
Circulation, which evaluated tight glycemic control in
patients with acute MI who received TPA (Chaudhuri A, et al. 2004;
109: 849-854). Those who received IV insulin had smaller
infarctions—the area of dead heart muscle was reduced by 30
percent. "That's just mind-boggling," Dr. Baldwin says.
It may even
be enough to pressure cardiologists to adhere to tighter controls,
though that group of specialists has been tough to budge. At Rush,
however, they're beginning to buy into it. "Cardiology has had so
much clinical success with lytic therapy, angioplasty, and stents
that the benefits of insulin therapy have been under their radar
screen," says Dr. Baldwin. "Intensive therapy with insulin hasn't
been within their usual realm of training or expertise." But, he
says, he and the Rush cardiologists recently formed a plan to
adopt the insulin protocol for diabetic MI patients. "And the
nurses are in-serviced and ready to go."
A big step
in convincing others is to alleviate their fears about
hypoglycemia. As it turns out, it's not that hard.
In trying
to reduce high blood sugars at his institution, reports Dr. Weed,
"we also dramatically reduced the episodes of low blood sugar. The
episodes of hypoglycemia dropped from 15 per month to one per
month." These figures come from one-month trials, done at separate
times—not a perfectly controlled experiment. "Nonetheless, it's a
really dramatic drop," he says. "And since we did a good job of
avoiding hypoglycemia, people have agreed to tighten up the
protocol." Like other hospitals, OSU began its efforts in the SICU,
moved to the MICU, and is gradually adding other wards.
Dr. Weed
and his colleagues are also making sure the protocol is maintained
when critically ill patients leave the ICU to have procedures done
in other areas of the hospital. "We now have the equipment for
doing the blood glucose testing in the radiology and cardiology
procedure suites, so they can continue to have their sugars
checked and their insulin infusion rate adjusted as needed," he
says.
Hypoglycemia simply isn't the big concern that it was 10 years
ago, adds Dr. Hirsch, pointing to the availability of insulin
analogues. "We can get blood sugars under excellent control with
very little risk of hypoglycemia."
Back
to top
As
fears about insulin and hypoglycemia recede,
a clearer picture should emerge about why insulin works so well in
so many settings.
There's no
end to the theories, but Dr. Baldwin boils them down to several
essential points. First, he notes, high blood sugars paralyze
portions of the immune system. "If you look at why patients didn't
die in the Van den Berghe study, the only cause of death that was
reduced across the board was sepsis."
In heart
attack and stroke patients, insulin may keep penumbra tissue from
a buildup of destructive acid levels, thereby limiting the volume
of dead tissue. It may also help maintain metabolism in healthy
tissue despite lower levels of oxygenated blood.
Insulin
also turns out to have a huge number of anti-inflammatory
properties, inhibiting inflammatory growth factors such as
activator protein 1 and early growth response gene-1. "Insulin
acts in these areas [affected by MI or stroke] to preserve and let
the tissue survive the insult," Dr. Baldwin says.
There's
more—insulin appears to have considerable anticoagulant
properties. That could make it a potent ally in reducing tissue
death from stroke and MI, even more so than risky and expensive
clot busters and emergency angioplasties. "What does insulin cost?
Pennies. Pennies! And all you have to do is check the sugar every
hour," says Dr. Baldwin.
All
enthusiasm aside, plenty of questions remain. "What are the longer
term results?" asks David Gurka, MD, PhD, director of the section
of critical care medicine and director of the MICU at Rush.
"They've shown that patients do better in the ICU, but how do they
do when they get out? Do they need tighter monitoring? There
hasn't been enough time for that followup to happen—maybe we'll
start to see that data in the next year or so."
Dr. Osei
raises other questions that may have a bearing on the laboratory's
role. "Is the benefit due to insulin per se, or to tighter
controls? What is insulin's impact independent of glucose?"
Monitoring insulin levels, hardly routine now, may become
important. So might monitoring proinflammatory markers and free
fatty acids.
It will
also be important, he notes, to coordinate the transition between
IV insulin and subcutaneous insulin as patients move out of ICUs.
"Just giving them insulin in the ICU and then sending them to the
ward without continuation of the protocol is a disservice."
But the
larger disservice will be failing to keep tighter glycemic control
in hospitalized patients. While the focus has been on hypoglycemia
for years, "it turns out the real disaster is on the other end,"
says Dr. Baldwin.
|