Introduction
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High blood glucose (BG) variability is considered to affect the prognosis of acutely ill patients. However, the significance of BG variability is not clearly elucidated. We investigated the significance of BG variability with a bedside-type artificial pancreas (AP).

Methods
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Strict BG control was performed by an AP, the STG22. Patients were evaluated at early (E) phase and late (L) phase (1 week after E phase). The number of patients was 83, among which 67 patients with daily mean BG (BGm) below 200 mg/dl were selected, because patients with BGm above 200 mg/dl had extremely high mortality, or 56%. They were classified into two groups, a group with high BG variability and a group without, based on the daily standard deviation of BG (BGsd). The two groups were compared regarding the following items: (1) mortality; (2) BGm, daily maximal and minimal BG (BGmax, BGmin), and daily BG difference (BGd); (3) demographic data; (4) administered glucose and insulin; and (5) degree of organ dysfunction and SOFA score.

Results
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\(1\) In the E phase, patients with BGsd above 14 mg/dl (group H, n = 26, mean BGsd 25 ± 11) had significantly higher mortality (46% vs. 17%) as compared with those with BGsd below 14 mg/dl (group N, n = 41, mean BGsd 9 ± 3). In the L phase, mortality was not significantly different between the groups with higher BGsd and those with lower BGsd at any point. (2) There was no significant difference in BGm between group H and group N (173 ± 24 vs. 173 ± 15). (3) BGmax and BGd in group H were significantly higher than those in group N (228 ± 42 vs. 191 ± 18, and 93 ± 39 vs. 37 ± 14, respectively). BGmin in group H was significantly lower than that in group N (132 ± 28 vs. 154 ± 16). (4) There was no significant difference in the abovementioned another items between group H and group N.

Conclusion
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High BG variability in the acute phase proved to be one of the highest risk factors. Therefore, strict BG control focusing on stabilization of BG variability especially in the acute phase was considered one of the important therapies. The AP was most reliable and therefore useful for clarifying the significance of strict BG control, and strict BG control using an AP should be considered in order to obtain the better outcome.
