Insulin requirement in the first 24 hours of intensive care admission predicts outcome

Insulin requirement (in mainly cardiothoracic surgical patients) is suggested as being more strongly associated with ITU mortality than poor glycaemic control [1]. We prospectively recorded insulin administration (soluble human insulin, by infusion; Actrapid^®; Novo Nordisk) in consecutive general ITU patients admitted over a 1-month period to our unit where guidelines are set to attempt to achieve an arterial blood glucose concentration between 4.5 and 8.0 mmol/l. Patients were subsequently divided into two groups according to whether or not they required insulin during the first 24 hours. Blood glucose was measured using the Radiometer^® ABL System 625 or 700 blood gas analysers. Samples were taken at least every 2 hours.

Ninety-eight patients were included in the study: 51 received no insulin, 47 received insulin at some time during the first 24 hours of admission and patients were grouped accordingly. There were no patients with a history of diabetes in the 'no insulin' group and 10 in the 'insulin' group. The mean (SD) number of hours patients who received no insulin were recorded as having a blood glucose > 8.0 was 0.40 (1.41) and for the 47 patients who received insulin 4.74 (4.77). The mean (SD) total insulin dose in the first 24 hours for the 'insulin' group was 38.4 (57.3) IU. Mortality in the 'no insulin' group was 13.1% and in the 'insulin' group 19.1% (chi-square 1.238, P > 0.20). There were no deaths among the previously diagnosed diabetic patients. When these patients were excluded from the analysis the mortality was 13.1% and 32.1%, respectively (chi-square 2.78, P < 0.10, P > 0.05).

The mean (SD) length of stay in the ITU was 4.12 (6.90) days in the 'no insulin' group and 6.77 (8.89) days in the 'insulin' group (one-tailed t test, unequal variance, P = 0.05).

Conclusion

An increased length of stay in ITU is predicted if insulin is required to maintain blood glucose < 8.0 mmol/l in the first 24 hours of ITU admission. An increased mortality may be predicted if insulin is required to maintain blood glucose < 8.0 mmol/l in the first 24 hours of ITU admission in nondiabetic patients.