Key Point

High blood glucose—often not considered in patients with COPD—is a risk factor for poor in-hospital outcomes in patients admitted with acute COPD exacerbations.

LONDON—Hyperglycemia is associated with poor outcomes in acutely ill patients hospitalized for pneumonia, myocardial infarction, and stroke. Notably, hyperglycemia and diabetes mellitus are common disorders in individuals with COPD. Despite this, no studies have looked at the correlation between hyperglycemia and outcomes in patients hospitalized with acute exacerbations of COPD. Researchers from the Glucose and Pulmonary Infection Group at St. George’s, University of London, conducted a retrospective study to determine the effect of hyperglycemia on outcomes in these patients. They found that the risk of adverse outcomes increased significantly with higher blood glucose levels.¹

The investigation included patients admitted to the study hospital in 2001 and 2002 with a discharge diagnosis of acute exacerbation of COPD with lower respiratory tract infection. Patients’ age and sex were noted, and lung function records, sputum microbiology results, and results of blood glucose tests taken at admission and during hospital stay were retrieved. Admission and discharge dates (or dates of death) were used to calculate length of hospital stay and in-hospital mortality.

The analysis included 291 patients who were admitted to the hospital once and 57 patients who were admitted two or more times. One hundred five patients met the criteria for a diagnosis of GOLD stage I COPD or worse. When more than one glucose measurement was available for a patient, the highest value was used. Blood glucose levels were higher than 6.1 mmol/L in 204 patients and higher than 11.1 mmol/L in 32 patients. The median blood glucose concentration was 7 mmol/L. Patients were assigned to one of the following quartiles based on their blood glucose levels: group 1, blood glucose less than 6 mmol/L; group 2, 6.0 to 6.9 mmol/L; group 3, 7.0 to 8.9 mmol/L; and group 4, greater than 9.0 mmol/L.

ADVERSE EVENTS CORRELATE WITH BLOOD GLUCOSE

The median length of hospital stay was nine days. One hundred fifty-four patients had good clinical outcomes, while 194 had adverse outcomes (death or hospital stay longer than nine days). The relative risk of an adverse outcome was 1.30 in group 2, 1.46 in group 3, and 1.97 in group 4, compared with group 1. After adjustment for age, sex, and previous diagnosis of diabetes, the absolute risk of adverse outcomes increased by 15% for every 1-mmol/L increase in blood glucose. In a subgroup of 193 patients whose blood glucose level at hospital admission was used for the analysis, the absolute risk of adverse outcomes increased by 31% for each 1-mmol/L increase in blood glucose.

The mean blood glucose concentration in patients who survived was 7.7 mmol/L, and 9.1 mmol/L in those who died. The risk of death increased by 10% for every 1-mmol/L increase in blood glucose. Results of sputum cultures indicated that multiple pathogens and Staphylococcus aureus were isolated significantly more often from patients in the higher blood glucose quartiles than from those in the lower quartiles.

A high blood glucose level is not currently seen as a potential risk factor for poor outcomes. "The recent UK guidelines for COPD do not even mention that blood glucose should be measured in a COPD exacerbation—let alone managed," said Emma H. Baker, Reader and Honorary Consultant in Clinical Pharmacology at St. George’s, University of London.

She noted that intervention studies are needed but added that in the current study, a 1-mmol/L increase in blood glucose was associated with a 15% increased absolute risk of adverse outcomes. "This raises the possibility that a 1-mmol/L reduction in blood glucose through intervention could reduce the absolute risk of adverse outcome by 15%,"she pointed out.

The authors acknowledged that their findings do not explain the mechanism behind blood glucose levels and adverse outcomes in COPD patients. Blood glucose is increased during acute illness as the result of different metabolic factors, they observed. Thus, perhaps COPD patients with higher blood glucose levels are more acutely ill than those with lower levels. Additionally, treatment with corticosteroids can increase blood glucose, and those patients who are more ill are also more likely to be receiving higher doses of corticosteroids and consequently to have higher blood glucose levels.

However, studies have shown that a decrease in blood glucose improves clinical outcomes in ICU patients.

Studies have further shown that maintaining blood glucose at 7.2 mmol/L can significantly reduce hospital mortality and length of ICU stay in critically ill patients. "If blood glucose control has a similar impact on patient outcomes from [acute exacerbations of] COPD, this could significantly reduce the one million inpatient bed days and 30,000 deaths annually attributable to COPD," concluded the authors.

—Gale Jurasek

Reference
1. Baker EH, Janaway CH, Philips BJ, et al. Hyperglycaemia is associated with poor outcomes in patients admitted to hospital with acute exacerbations of chronic obstructive pulmonary disease. Thorax. 2006;61:284-289.

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