Intensive insulin therapy in the intensive care unit: assessment by continuous glucose monitoring

Background

Intensive insulin therapy to keep glycaemia at 80–110 mg/dl reduced mortality and morbidity in a surgical ICU. It is not known whether these findings are applicable to a medical ICU. Continuous glucose monitoring (CGM) might improve adjustment of insulin therapy.

Aims

To assess whether insulin regimens (subcutaneous [s.c.] vs intavenous [i.v.]), based on discontinuous glucose monitoring, are adequate in achieving euglycaemia in a medical ICU. Secondary outcome measures were the influence of glycaemia on inflammatory, renal, and metabolic parameters.

Methods

So far, 28 patients (male/female: 16/12, mean age 64 ± 16 years, non-diabetic/type 2 DM/type 1 DM: 16/9/3, i.v. vs s.c. insulin: 13/15; median APACHE II score: 20, range 12–32, SOFA score 6 [2–15]; 10 septic shock patients) were recruited in a single-center, prospective, observational study. Forty-eight-hour CGM was initiated within 3 days after admission at ICU, using a subcutaneous glucose sensor (GlucoDay^®; Menarini Diagnostics) and compared with arterial blood glucose samples.

Results

During 48-hour continuous monitoring, glycaemia was >140 mg/dl in 37 ± 28% of the time, and < 60 mg/dl in 5 ± 10% of the time. Target glycaemia (80–110 mg/dl) was reached in only 25 ± 16% of the time. The mean insulin dose per day was 72 units (range 0–276). Patients on s.c. insulin spent more time at glycaemia >110 mg/dl (70 ± 27% vs 47 ± 16% on i.v. insulin, P = 0.016), but similar time at glycaemia < 60 mg/dl. Patients with septic shock had higher insulin needs (119 ± 90 vs 46 ± 55 units/day, P = 0.013), and tended to spend less time at glycaemia >110 mg/dl (47 ± 22 vs 66 ± 25%, P = 0.062). Diabetic patients spent more time at hyperglycaemia (%time >140 mg/dl: 51 ± 27 vs 26 ± 24%, P = 0.019). Patients who died at ICU had a higher SOFA score (9 ± 4 vs 6 ± 3, P = 0.027), a higher lactate (P = 0.003), a higher ferritin (P = 0.043), a lower total protein concentration (P = 0.023), but similar glycaemic profiles (% time > 200, >140, >110, < 80 and < 60 mg/dl) and insulin dose. Presence of diabetes, insulin regimen and dose did not influence mortality. Glycaemia correlated with leucocyte count (r = 0.37, P = 0.05), total protein concentration (r = 0.37, P = 0.049), but not with renal and liver parameters. CGM detected peaks (e.g. when starting total parenteral nutrition) and dales of glycaemia much earlier than discontinous monitoring. CGM data correlated with arterial blood glucose. There were no adverse events with the use of the GlucoDay^®.

Conclusions

The GlucoDay^® system, a good method to monitor glucose excursions in ICU patients, was well tolerated. Continuous glucose monitoring is mandatory for optimal titration of insulin therapy in the ICU, as target glycaemia (80–110 mg/dl) was only reached in 25% of the time. An i.v. insulin therapy is better than a s.c. regimen to obtain target glycaemia.