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A1426
October 16, 2007 9:00 AM - 10:30 AM Room Room 301 |
| Online Measurement of Acetone in Expiratory Air by Mass Spectrometry during Cardiac Surgery |
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Martin M. Schmoelz, M.D., Siegfried Praun, M.Sc., Ph.D., Michael Schmoeckel, M.D., Ph.D., Christian Kowalski, M.D., Gustav Schelling, M.D., Ph.D. Department of Anesthesiology, Ludwig Maximilians University, Munich, Bavaria, Germany |
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Introduction: Several studies have recently shown substantial clinical benefits of tight glucose control in the critical care unit and during major surgery. Elevated blood glucose levels are associated with an increased risk of postoperative wound infection, cardio-vascular events and poor outcome in hospitalized patients1. Low insulin release and -resistance in patients with established diabetes, or its relative ineffectiveness when insulin action is antagonized by massive stress such as sepsis and surgical trauma leads to glucose production from glycogenolysis and gluconeogenesis, resulting in hyperglycemia. Furthermore, lipolysis provides free fatty acids, the oxidation of which generates ketones such as acetoacetic and -hydroxybutyric acids2. Here we show that the volatile ketonebody acetone which appears under conditions of hyperglycemia and metabolic stress can be measured in expiratory air of patients undergoing cardiac surgery using online mass-spectrometry. Methods: We used a mass spectrometry system based on ion-molecule reactions coupled with quadrupole mass spectrometry (IMR-MS), which provides a highly-sensitive method for online and offline measurements of organic and inorganic compounds in gasesa. The IMR-MS system was directly connected to patients (n=20) undergoing cardiac surgery via a T-piece inserted between the endotracheal tube and the Y-connector of the anesthesia machine. Airway gas was continuously sampled at 50 ml/min. We quantified the ketonebody acetone in expiratory air. Acetone concentrations were averaged over a period of 5 min when blood drawings were done for blood glucose determination (59 pairwise measurements). We then compared acetone measurements in two groups of patients: Patients with known non-insulin-dependent diabetes mellitus (n=8, 23 measurements) and non-diabetics (n=12, 36 measurements). The relationship between acetone signalling in expiratory air, blood glucose concentration and diabetic status were analyzed by partial Pearson´s correlation and by regression analyses. Results: Acetone concentrations in expiratory air correlated significantly with blood glucose measurements in both patients with diabetes (r=0.68, p<0.001, n=23) and in patients without diabetes (r=0.56, p<0.001, n=36) and were significantly higher in diabetic patients than in non-diabetics (p<0.001, Fig.). The slope of the regression line between blood glucose concentrations and acetone concentrations was steeper for measurements in diabetic patients than for non-diabetic measurements (β=591 vs. β=119). Above a blood glucose concentration of 110 to 120 mg/dl, acetone concentrations clearly differentiated between diabetics and non-diabetics (Fig.). Conclusion: Online measurement of acetone in expiratory air by IMR-MS may allow the early detection of low-insulin release or insulin-resistance states in metabolically stressed patients undergoing major surgery. 1N.Engl.J.Med. 2006; 355: 1903-11 2Diabetes Care 2006; 29: 1150-9 aAirsense Mass Spectrometry Systems, V&F medical development GmbH, A-6067 Absam, Austria.[figure1] Anesthesiology 2007; 107: A1426 |
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