Hypoglycaemia is associated with a higher mortality in critically ill patients

Introduction

Hypoglycaemia, a common complication of strict glucose control in critically ill patients, has controversial effects on mortality. The hyperglycaemic index (HGI) takes into account the unequal time distribution of blood glucose sampling and is a better predictor of death than other methods to quantify hyperglycaemia [1]. By analogy with the HGI, we defined the hypoglycaemic index (HGI-60) as the area above the glucose curve and lower than 60 mg/dl divided by the length of ICU stay. The objective of the study was to evaluate the effects of hypoglycaemia on inhospital mortality in critical care patients using a new method for quantification of hypoglycaemia, the hypoglycaemic index (HGI-60).

Methods

A retrospective study performed in four mixed ICUs. From 2004 through 2006, patients treated with continuous insulin therapy were included. Admission type, sex, age, the occurrence of hypoglycaemia <60 mg/dl, APACHE II score and outcome (hospital dead) were recorded. The HGI-60 is calculated after simple interpolation of all glucose values measured during the ICU stay. The relations between independent variables and hospital mortality were determined by logistic regression analysis.

Results

One hundred and ninety-six patients were included. The mean age was 60.5 years and 56% were male. The mean APACHE II score was 22.8 and the hospital mortality was 51.5%. The HGI-60 median was 0.02 mg/dl/hour (interquartile range 0 to 0.13) in survivors versus 0.07 mg/dl/hour (interquartile range 0 to 0.23) in nonsurvivors (P = 0.01). Results of logistic regression analysis show that HGI-60 was associated with higher hospital mortality independently of the APACHE II score (OR = 7.2; 95% CI = 1.6 to 32.1; P = 0.009). The HGI-60 had a higher area under the receiver operating characteristic curve (0.70) than the occurrence of hypoglycaemia (0.67).

Conclusion

Hypoglycaemia during the ICU stay is a marker of increased mortality. The hypoglycaemic index (HGI-60) is a better predictor of mortality than the occurrence of hypoglycaemia.