Severe hypoglycaemia during intensive insulin therapy: a rare event in critically ill patients

Introduction

Tight glycemic control reduces mortality in surgical intensive care patients and in long-term medical intensive care patients. The incidence of severe hypoglycaemia (glucose ≤2.2 mmol/l) in the intensive treatment group has been 3.1–5.1%. Recently, a large study on intensive insulin therapy was prematurely discontinued due to safety issues. The incidence of hypoglycaemia was 9.8% in intensive treatment group and the mortality among patients experiencing hypoglycaemia was 18.6%. As the safety of intensive insulin therapy has been questioned, we screened all patients during a 17-month period to see the incidence of hypoglycaemia and its effects on the prognosis of the patients.

Methods

A retrospective study was performed in two ICUs, one eight-bed general ICU and one 10-bed surgical ICU. All patients treated between 7 February 2005 and 30 June 2006 were included in the study. A nurse-driven intensive insulin protocol with a target blood glucose level of 4–6.1 mmol/l had been introduced in 2004. All blood glucose measurements performed during the ICU treatment were analysed. The patients were divided into two groups according to the lowest detected blood glucose value (≤2.2 or ≥2.3 mmol/l).

Results

A total of 1,024 patients (1,124 treatment periods) were included in the study. Thirty patients were excluded due to incompleteness of the data. During the study period 61,203 blood glucose measurements were performed, 1,578 (2.6%) of which were below the target value of 4 mmol/l. Severe hypoglycaemia (≤2.2 mmol/l) occurred in 25 patients (36 measurements). The incidence was 0.059% of the measurements and 2.3% of the patients. The median age, sex, APACHE II score, SAPS II or diagnosis category did not differ between the groups. The median (IQR) ICU and hospital length of stay was 4.3 (1.8–10.6) and 18 (8.5–39.5) days in patients with lowest blood glucose ≤2.2, and 2.7 (1.2–5.7) and 13 (7–23) days in patients with lowest blood glucose ≥2.3 (P = 0.058 and P = 0.077, respectively). The hospital mortalities were 25% and 15%, respectively; the difference was not statistically significant.

Conclusion

Severe hypoglycaemia during intensive insulin therapy is rare in protocol-driven ICU treatment compared with previous clinical trials. When present, hypoglycaemia may have an impact on the outcome of the patients