Glucose in airway secretions and an association with the presence of Staphylococcus aureus in the respiratory tract

Good glycemic control has been shown to decrease mortality in critically ill patients [1], the predominant effect being a decrease in the incidence of serious infection. Glucose is normally absent from airway surface liquid [2], which may be important to host defenses against infection. Glucose in endotracheal secretions has been attributed to the aspiration of enteral feed [3]. Previously we have found this to be false and that glucose appears in the airway secondary to hyperglycemia. We hypothesize that glucose in airway secretions increases the risk of bacterial airway infections. Our objectives were to observe for relationships between hyperglycemia and the presence of glucose and bacteria in airway secretions.

Methods and results

One hundred critically ill, ventilated patients admitted to a general (medical and surgical) adult intensive care were recruited. Glucose concentrations were measured simultaneously in arterial blood (ABL2000; Radiometer, Copenhagen, Denmark) and endotracheal (ET) secretions (glucose oxidase sticks and GM9D Analyzer; Analox, London, UK). Sputum samples were sent for qualitative microscopy and culture. All patients were enterally fed, unless clinically contraindicated.

Of 100 patients, 89 had microbiology results returned. Fifty-four of 100 had glucose detected in their ET secretions (> 0.5 mmol/l). Patients with ET glucose had a significantly higher blood glucose (8.82 ± 0.31) than those without (6.69 ± 0.23, P = 0.004); this was unrelated to enteral feeding. Significantly more patients with ET glucose had Staphylococcus aureus detected in their sputum (33/49 vs 10/40, P = 0.007). Table 1 presents the results for sensitive S. aureus and methicillin-resistant S. aureus (MRSA).

Table 1 Microbiology results

Comment

Glucose appears in airway secretions and is associated with hyperglycemia. It is not related to enteral feeding. Possible mechanisms include saturation of airway epithelial sodium glucose cotransporters, or increased epithelial permeability. Glucose in airway secretions is strongly associated with S. aureus infection (Table 1). This may be one mechanism by which control of glucose decreases infectious complications.