Nagham Jafar MDa, Hawa Edriss MDb, Ebtesam Islam MD PhDc, Kenneth Nugent MDd
Correspondence to Nagham Jafar MD.
Email: drnaghamsaeed@yahoo.com
SWRCCC 2014;2(7)1:-11
doi:10.12746/swrccc2014.0207.082
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Patients with acute exacerbations of chronic obstructive pulmonary disease usually require an escalation in medical management and often require hospitalization. The outcomes from these episodes depend on the severity of the underlying chronic lung disease, the degree of acute respiratory failure superimposed on the chronic lung disease, comorbidity, and possibly hospital related complications. Hyperglycemia represents an independent risk factor for hospital associated complications and/or mortality in other medical diagnoses, such as stroke and acute myocardial infarction. Recent studies in patients with acute exacerbations of COPD demonstrate that hyperglycemia is associated with an increased length of hospital stay, failure of noninvasive ventilation, and/or mortality. Acute stress and medications used with an acute flare, such as glucocorticoids and beta agonists, increase blood glucose levels. The explanation for poor outcomes likely involves an increase in colonization with pathogenic bacteria, acute changes in host defenses, and possibly metabolic disorders related to hyperglycemia and glycosuria. Patients with acute stress and glucocorticoid related hyperglycemia often have higher blood glucose levels in the afternoon and early evening. Consequently, this problem may be overlooked if clinicians depend on routine a.m. laboratory tests. Therefore, patients with acute flares in COPD should have bedside point of care glucose measurements during the early course of their hospitalizations. Patients with high glucose levels require nutritional management and/or insulin treatment. We need more prospective studies to determine the degree of hyperglycemia in these patients, the acute consequences, and the best management strategies.
Keywords: COPD exacerbation, hyperglycemia, length of stay, mortality and morbidity
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Patients with chronic obstructive pulmonary disease (COPD) have acute exacerbations approximately 1.3 times per year. These exacerbations range in severity from transient decreases in functional status to fatal events. In the United States, exacerbations have contributed to a 102 percent increase in COPD-related mortality from 1970 to 2002 (21.4 to 43.3 deaths per 100,000 persons).1 Effective management of an acute exacerbation of COPD (AECOPD) requires symptom relief and reducing the risk for subsequent exacerbations. Identification of patients at risk for more complicated hospital courses should facilitate in-patient management, and risk factors for adverse outcomes include lower arterial pHs, older age, male gender, underlying comorbidities, disease severity, and in-hospital complications.2 Hyperglycemia is associated with poor outcomes in patients with pneumonia,3 myocardial infarction,4 and stroke,5 but the effect of hyperglycemia on outcomes during AECOPD has not been definitely established. Recent Global Initiative of Chronic Obstructive Lung Disease (GOLD) and American Thoracic Society guidelines do not comment on the control of blood glucose during COPD flares.
Hyperglycemia is very common in any acute
illness, and its pathophysiology includes acute increases
in peripheral insulin resistance and hepatic
glucose production caused by increases in glucocorticoids,
catecholamines, and pro-inflammatory cytokines.6
Below we summarize studies that have evaluated
the effect of hyperglycemia in patients admitted
with AECOPD (Table).
Baker, et al. concluded that hyperglycemia (blood
glucose >126 mg/dl) is associated with an increased
risk of death and prolonged hospital stays (more than
nine days) independent of age, sex, and a previous
diagnosis of diabetes.7 This study also showed that
in the subgroup of patients who had COPD confirmed
by spirometric testing, the blood glucose quartile independently
predicted adverse clinical outcomes, but
the underlying COPD severity did not. This was a retrospective
case control study conducted by retrieving
data from electronic medical records for 284 patients
admitted with AECOPD to St. George’s Hospital (UK)
between 2001 and 2002. In this study, only the highest
blood glucose recorded for the patients during
their hospital stay was used for analysis, and patients
were grouped according to their blood glucose quartile
(group 1, <108 mg/dl, n = 69; group 2, 108–125
mg/dl, n = 69; group 3, 126–160 mg/dl, n = 75; and
group 4, >160 mg/dl, n = 71).The relative risk (RR)
of death or a longer inpatient stay was significantly
increased in group 3 (RR 1.46, 95% CI 1.05 to 2.02,
p = 0.02) and group 4 (RR 1.97, 95% CI 1.33 to 2.92,
p<0.0001) compared to group 1. For each 18 mg/dl
increase in blood glucose the absolute risk of an adverse
outcome increased by 15% (95% CI 4%to 27%,
p = 0.006). Also hyperglycemia was associated with
colonization of sputum with multiple pathogens and
with Staphylococcus aureus in this study.
The relationship between hyperglycemia and
non-invasive ventilation (NIV) outcomes in COPD
patients was investigated in a prospective study by
Chakrabarti, et al..8 These authors concluded that
hyperglycemia on admission is associated with NIV
failures. Eighty-eight COPD patients presented with
acute type II respiratory failure and had NIV initiated
within 24 hours of admission. Random blood glucose
levels were measured before NIV use. Hyperglycemia
was present at baseline in 50% of patients; 16 (18%)
had a pre-existing diagnosis of diabetes mellitus. NIV
failure occurred in 34% of patients (15/44). It was
significantly more common in patients with hyperglycemia
(34%) than in patients without hyperglycemia
(2%). Blood glucose levels were higher in patients
with NIV failure (162.7 ±58 mg/dl vs. 127±39.2 mg/dl;
p=0.003). It is not known whether hyperglycemia is a
direct cause of poor outcomes in AECOPD or whether
it is a marker for other adverse factors, such as
coexisting comorbidities, treatment strategies, or the
severity of illness. This study provided some insight
into the possible underlying mechanisms since the
NIV failure in AECOPD was independent from oral
corticosteroid use immediately before admission, underlying
diabetes mellitus, pH and APACHE II (Acute
Physiology and Chronic Health Evaluation II) scores.
Moretti and colleagues studied 186 patients
admitted to a respiratory intensive care unit with respiratory
failure characterized by a mean pH of 7.23±
0.07 and a mean PaCO2 of 85.3 ±15.8 mm Hg9. The
study used logistical regression analysis to analyze
factors associated with noninvasive respiratory failure
after an initial success (late failures). The presence
of metabolic complications (found in >20% of
the late failures) predicted late failures (more than 48
hrs) of NIV after an initial success. The most frequent
metabolic complication was hyperglycemia (defined
as blood glucose >200 mg/dl) which was present in
all the patients with metabolic disorders. However, all
hyperglycemic patients who developed late failure to
NIV also developed pulmonary infection during the
course of their hospital stays, and this likely contributed
to NIV failure or death.
Burt, et al. reported that length of hospital stay is increased by 10% (21hours) for each 18 mg/dl increase
in mean glucose (P=0.01).10 In this study the
blood glucose levels of 47 patients were monitored
continuously using a device to measure interstitial
glucose levels to determine the pattern of hyperglycemia
in patients receiving prednisolone for AECOPD.
Higher mean daily glucose levels were positively associated
with longer hospital stays; this relationship
with length of stay was not significant for other markers
of disease severity. Parappil et al. retrospectively
analyzed 172 patients admitted with AECOPD, including
39 patients with comorbid diabetes mellitus.11
In this study the presence of DM was associated with
increased length of stay (mean 7.8 days) and mortality
(8%) in comparison with patients without DM (6.5
days and 4% mortality), but these differences were
not statistically significant.
Kasirye, et al. studied 209 hospitalized patients
with AECOPD to evaluate factors associated with
in-hospital complications, length of hospitalization,
30-day hospital readmission, and 90-day all-cause
mortality. The study analysis failed to reveal any associations
between higher blood glucose levels and
adverse outcomes but did find that low glucose levels
(less than 90 mg/dl) were associated with increased
hospital complications and increased length of stay
in these patients.12 This study had three important
differences when compared to the Baker study. 1) It
used WHO/GOLD criteria and previous spirometric
measurements to define population with AECOPD,
while the Baker study used only ICD-10 codes. 2) This
study used radiological information to rule out other
comorbidities, like pneumonia, which might confer a
confounding effect on the data. 3) This study used
daily mean blood glucoses to identify hyperglycemia,
since blood glucose levels among AECOPD patients
on systemic corticosteroids tend to peak in the afternoon
and evening hours. Therefore, blood glucose
measurements taken throughout the day more accurately
reflect a patient’s glycemic status. Other studies
have utilized either single admission blood glucose
or a single peak blood glucose obtained fasting
or non-fasting during hospitalization.
Hypoglycemia is not a usual finding in AECOPD,
because hyperglycemia often develops secondary to
stress hormones release, cytokines,13 and treatment
with systemic corticosteroids.14 The presence of hypoglycemia
may be a marker for severity of illness if
its presence is not related to a treatment side effect.
It could reflect defects in glucose counter-regulation.
Therefore, the patient’s inability to develop a hyperglycemic
response might portend adverse clinical
outcomes.15,16
Studies demonstrating that hyperglycemia is associated
with poor outcomes in AECOPD usually
do not identify the possible pathophysiology. In one
cross sectional observation study, the glucose levels
of intubated patients were measured in bronchial secretions
and blood, and the sputum was cultured for
pathogenic bacteria.17 This study demonstrated that
glucose was detected in airway secretions in patients
with hyperglycemia and the risk of colonization with
MRSA was markedly increased in the presence of
glucose (relative risk 2.1; 95% CI 1.2 to 3.8). In addition,
the presence of MRSA was associated with infiltrates
on the chest radiograph, increased levels of
C reactive protein, and prolonged ICU stays (approximately
seven days).17 The Baker study also showed
that hyperglycemia was associated with a significant
increase in the presence of multiple pathogens and
MRSA in the sputum.18 Hyperglycemia may increase
the rate of colonization, and these changes in flora in
association with abnormal host defenses increase the
risk of infection and adverse outcomes.
Hyperglycemia (defined as blood glucose level more than 200 mg/dl ) in acutely ill patients with no prior diagnosis of diabetes, including those admitted for AECOPD, has been linked to several factors, including medications and stress responses to acute illness. It has been reported that more than 38% of patients admitted to the hospital have hyperglycemia (defined by in-hospital fasting glucose level of ≥126 mg/dl or a random blood glucose level of 200 mg/dl).19 COPD itself may be considered as a novel risk factor for new onset type 2 diabetes mellitus through multiple pathophysiological alterations, such as inflammation, oxidative stress, insulin resistance, weight gain, and alterations in metabolism of adipokines.20,21,22 Moreover, infection (a potential cause of AECOPD) can lead to hyperglycemia by the development of peripheral insulin resistance and alterations in hepatic glucose metabolism, leading to the overproduction of glucose and failure of the liver to appropriately adapt when nutritional support is administered.23 We will discuss briefly the factors that can affect glucose metabolism in AECOPD patients.
In acute illness, glucose production is increased, peripheral glucose utilization is decreased, and this leads to increased plasma glucose levels. This response appears to be mediated by a combination of neurohumoral changes, lipid mediators, and cytokine production. Increased serum concentrations of glucagon, adrenaline, and cortisol occur in response to a variety of pathophysiological stresses. As a part of the acute stress response, reversible insulin resistance develops, and peripheral glucose uptake decreases.24 Stress in acutely ill patients can also lead to increased catecholamine secretion, which can contribute to hyperglycemia.25
Oltmanns, et al. studied 14 healthy male volunteers. These men were subjected to 30 minutes of hypoxia (O2 saturation =75%) and normoxia (O2 saturation= 96%) under conditions of a euglycemic clamp.26 This study concluded that acute hypoxia causes glucose intolerance. Hypoxia also increased plasma epinephrine levels, heart rates, and anxiety. Several animal studies have shown the development of insulin resistance after periods of intermittent hypoxia.27,28 Louis and Punjabi studied the effect of intermittent induced hypoxia on 13 healthy volunteers using an intravenous glucose tolerance test to assess insulin dependent and independent glucose disposal. The study showed that intermittent hypoxia caused insulin resistance and defective insulin independent glucose disposal.29 Pallayova, et al. concluded that intermittent hypoxia is associated with damage to pancreatic beta cells.30 Animal studies have also demonstrated that both acute and chronic sustained hypoxia can cause insulin insensitivity and hyperglycemia.31
AECOPD can be complicated by hypercapneic respiratory failure and respiratory acidosis. Studies have shown that respiratory acidosis causes glucose intolerance by inducing hepatic and peripheral insulin resistance.32 In addition, animal studies suggest that metabolic acidosis can cause impaired insulin secretion.33
a. Glucocorticoids: Hyperglycemia is a well-recognized
complication of corticosteroid therapy. At the
University of Pittsburgh, a retrospective study concluded
that hyperglycemia occurs in the majority of
hospitalized patients receiving high doses of corticosteroids
(≥40 mg per day).34 Since poor outcomes
are associated with hyperglycemia, these authors
suggested that a protocol should be followed to measure
glucose levels in all patients receiving high dose
corticosteroid therapy. Glucocorticoids cause hyperglycemia
by inducing insulin resistance, increasing
liver gluconeogenesis, and impairing pancreatic β-cell
function.35,36
b. Beta agonist medications and other catecholamines:
Several animal and human studies have
demonstrated that B2-agonists can affect glucose
levels by altering pancreatic insulin secretion, liver
metabolism, and glucose uptake.37 The overall result
is hyperglycemia, which can be clinically significant in
patients with AECOPD, since many of these patients
take corticosteroids, have sedentary lifestyles, and
are overweight. Studies have shown that catecholamines
lead to hyperglycemia directly by affecting
the pancreas, by increasing glucagon secretion, or by
exerting a direct effect independent of pancreatic hormone
release.38,39
c. Antibiotics: Several antibiotics have been reported
to cause abnormalities in glucose metabolism
and can cause both hyperglycemia and hypoglycemia.
Fluoroquinolones are the only antibiotics consistently
associated with hyperglycemia.40 A large
cohort with 78, 433 diabetic patients were followed
over a 23 month period to determine the relative risk
of hyperglycemia and hypoglycemia in association
with antibiotic treatment. The absolute risk for hyperglycemia
was 1.6 per 1000 persons for macrolides,
2.1 for cephalosporins, 6.9 for moxifloxacin, 3.9 for
levofloxacin, and 4.0 for ciprofloxacin. The adjusted
odds ratios for fluoroquinolones compared to macrolides
were 2.48 for moxifloxacin, 1.75 for levofloxacin,
and 1.87 for ciprofloxacin.41 Yamada, et al. showed
that chronic treatment with gatifloxacin decreases
islet insulin content by inhibiting insulin biosynthesis.42 Park Wyllie, et al. studied 470 patients treated for
hyperglycemia within 30 days after antibiotic therapy
and found that gatifloxacin was associated with an increased
risk of hyperglycemia (adjusted odds ratio,
16.7; 95 % confidence interval, 10.4 to 26.8).43
d. Theophylline: In an animal study, aminophylline
administration caused hyperglycemia possibly by the
induction of insulin resistance.44 Another study with
preterm infants showed that plasma glucose levels
increased after theophylline therapy was started in
infants with respiratory problems.45
Diabetes mellitus, hyperglycemia, and impaired
glucose tolerance are associated with increased
C-reactive protein, interleukin-6, and tumor necrosis
factor-α.46 Yorek, et al. studied the pro-inflammatory
effect of glucose in vitro and showed that incubation
of endothelial cells in high glucose concentrations results
in radical oxygen species production and activation
of the transcription factor nuclear factor-kappa
B and an increase in monocyte adhesion.47 Glucose
levels have regulatory effects on some pro-inflammatory
cytokines.48 Interestingly, these cytokines (IL-6,
IL-18, and TNF-α) have been implicated in the development
of insulin resistance, atherosclerotic plaque
rupture, and future cardiovascular events, and this
could explain the association between hyperglycemia
and cardiovascular events.49
Several studies have concluded that hyperglycemia
can alter cellular defense mechanisms during infection.
High glucose levels alter the immune system
by decreasing neutrophil degranulation during inflammation,
by causing defects in adherence,50 and by impairing
phagocytosis,51 chemotaxis,52 bacterial killing,
and the respiratory burst.53 Hyperglycemia can also
reduce protease secretion by neutrophils, leading to
decreases in antimicrobial activity.54 Turina, et al concluded
that short term hyperglycemia affects all major
components of innate immunity and impairs the ability
of the host to control infection.55 Von Kanel reported
that a short term rise in blood glucose levels in normal
individuals can lead to a decrease in the number of
lymphocytes and cause redistribution in lymphocytes
subsets.56 These abnormalities are reversed when
glucose is lowered.57 A recent review suggested an
association between diabetes and a decreased risk of
lung injury, possibly mediated by reduced inflammatory
responses secondary to hyperglycemia.58
Hyperglycemia is a common problem in hospitalized
patients and can be both a difficult and costly
problem during patient care. Observational and
randomized controlled studies suggest that good
glycemic control in hospitalized patients improves
outcomes in both medical and surgical patients. The
Endocrine Society, the American Diabetes Association,
the American Heart Association, the American
Association of Diabetes Educators, the European
Society of Endocrinology, and the Society of Hospital
Medicine conducted a group meeting to formulate
evidence-based practice guidelines for the management
of hyperglycemia in hospitalized patients in the
non-critical care setting. The following is a brief summary
of their recommendations.59
1. Diagnosis of hyperglycemia and diabetes mellitus in hospitalized patients:
The management of blood glucose levels in critical care settings is a controversial topic with several randomized controlled trials comparing “tight” to “loose” blood glucose control. The large international randomized controlled trial (“the NICE-SUGAR Study”) demonstrated target blood glucose of less than 180 mg/dl resulted in lower mortality than a target of 81 to 108 mg/dl in critical care units.60
In this review, we have discussed studies that suggest a relationship between hyperglycemia and poor outcomes in AECOPD. However, these studies do not completely explain the pathophysiology underlying these complications. Also, one study failed to find a relationship between hyperglycemia in patients with AECOPD and reported that hypoglycemia was associated with poor outcomes. Other studies have reported poor outcomes in patients with diabetes mellitus and hyperglycemia who are admitted for different medical conditions, such as myocardial infarction61 and cerebrovascular accidents.62,63 Krinsley studied the relationship between hyperglycemia and hospital mortality in a heterogeneous group of critically ill patients and concluded that even modest hyperglycemia after intensive care unit admission was associated with a substantial increase in hospital mortality in patients with a wide range of medical and surgical diagnoses.64 Animal model studies and other observational studies suggest that possible mechanisms include defective immune responses and an increased risk of infection, increased thrombotic events, increased oxidative stress, and increased inflammatory markers.65 Several studies have shown that hyperglycemia is associated with increased numbers of pathogens and MRSA colonization of the sputum.
Hyperglycemia has been associated with increased morbidity, increased mortality, and longer lengths of stay, and more hospital costs in patients with both medical and surgical conditions. AECOPD is associated with hyperglycemia due to the stress related hormonal response to acute illness and possibly some of the medications routinely used in the treatment of AECOPD. Several studies suggest that hyperglycemia has adverse outcomes in patients with AECOPD, but the pathophysiology underlying these effects has not been determined. We need more research on outcomes in AECOPD in patients with hyperglycemia, using larger sample sizes and taking into consideration a design which can control for cofounders and provide more insight into the pathophysiology. In addition, a study on targeted glycemic control and outcomes is needed.
Table Summery of the studies investigating the relationship between blood glucose level and COPD exacerbation outcomes
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