Tight Control of Blood Sugar

"Tight glycemic control" means that the blood sugar is kept within a narrow range. Read the abstract below, and then answer the questions that follow it.

"Methods: In this two-center, prospective, randomized trial, we enrolled 980 children, 0 to 36 months of age, undergoing surgery with cardiopulmonary bypass.

Patients were randomly assigned to either tight glycemic control . . . targeting a blood glucose level of 80 to 110 mg per deciliter . . . or standard care in the cardiac intensive care unit.

Results: A total of 444 of the 490 children assigned to tight glycemic control (91%) received insulin versus 9 of 490 children assigned to standard care (2%). . . . [T]ight glycemic control was not associated with a significantly decreased rate of health care- associated infections (8.6 vs. 9.9 per 1000 patient-days, P = 0.67).

Conclusions: Tight glycemic control can be achieved with a low hypoglycemia rate after cardiac surgery in children, but it does not significantly change the infection rate . . . as compared with standard care."

a. Identify the treatment variable and the response variable.

b. Was this a controlled experiment or an observational study? Explain.

c. What does the p-value show?

d. Can you conclude that the use of tight glycemic control affects the rate of infections? Why or why not?