Background and Goal of Study: Various insulin infusion protocols have been developed to avoid perioperative hypo- and hyperglycaemic events during cardiac surgery with cardiopulmonary bypass (CPB)1. We aimed to identify the risk factors associated with such events when using the University of Ghent Insulin Protocol (UGIP) for achieving a glucose level between 70 and 180 mg/dL. In this protocol, an infusion of insulin is started after induction of anaesthesia at a calculated rate in units per hour. The infusion rate in non-diabetic patients is calculated from the baseline glycaemia divided by 75, or, in diabetic patients from the baseline glycaemia divided by 50. This maintenance dose is doubled when rewarming is started during CPB and the initial dose is reinstituted after protamine administration.
Methods: Data from 776 cardiac surgery patients were retrieved from the institution database. Relative risk for the development of perioperative hyperglycaemic (> 180 mg/dL) and hypoglycaemic (< 70 mg/dL) events were calculated for the following variables: Redo operation, CPB duration > 60 min, age > 70 years, gender, temperature on CPB < 32°C, nadir haematocrit < 24%, inotropic and/or vasoactive support, corticosteroids, and diabetes mellitus. The statistically significant variables were included in a multiple regression analysis to identify the independent risk factors.
Results: Sixteen patients (2%) developed a perioperative hyperglycaemic event. Male gender (RR = 0.34; 95% CI: 0.13 - 0.90; p = 0.029), inotropic support (RR = 3.81; 95% CI: 1.40 - 10.37; p = 0.01), and perioperative corticosteroids (RR = 5.83; 95% CI: 1.96 - 17.30; p = 0.008) showed a significant association with such events but only corticosteroids (p = 0.006) and inotropic support (p = 0.019) were identified as independent risk factors. Thirteen patients (1.7%) developed a perioperative hypoglycaemic event. Inotropic support (RR = 4.87; 95% CI: 1.40 - 17.09; p = 0.035), and diabetes mellitus (RR = 4.87; 95% CI: 1.23 - 11.13; p = 0.028) showed a significant association with such events but only diabetes (p = 0.013) was identified as an independent risk factor.
Conclusion: Independent risk factors for developing perioperative hyperglycaemia when using the UGIP are corticosteroids and inotropic agents, while diabetes mellitus seems to be only independent risk factor for hypoglycaemic events.
1. Lecomte P et al. Anesth Analg 2008,107: 51-8.