| Objective: With more knowing about the side-effect of postoperative insulin resistance(IR) on metablic and physiologic state of patients, recently more and more interests has arisen to find an effective strategy to prevent postoperative IR and an intensive study for the mechanisms of IR is becoming urgent. Up to now, there has been a simple and useful tactic named preoperative oral carbohydrate to reduce postoperative IR. In many upper abdominal and total hip replacement surgeries, the effect of this tactic has been fully confirmed in reducing the deterioration of postoperative insulin sensitivity, though its inner actions remain unclear. But for the more severely surgical trauma situation such as in CABG patients, who were usually, to some extent, accompanied by insulin resistance previously, whether such oral carbohydrate rich beverage shortly before the operation is safety, and its effectiveness in reducing postoperative IR still remain under-investigated. On the other hand, it has been shown that the disability of GLUT4-induced glucose transport in peripheral tissues ( i.e. skeletal muscle and adipose ) owe a mainly contribution to the development of the postoperative decrease of insulin sensitivity. However, the further study about GLUT4 protein's mRNA transcription is unenough, and how or where the preoperative oral carbohydrate loading takes its action in attenueating IR is not certain from the available data. To know more the two questions mentioned above, we presently perform the below experiments.Methods: Thirty elective CABG patients were randomized topreparation with 16.7% glucose drink(treatment group) and overnight fasting(control group). The treatment group were given 600ml to drink on the evening before and another 300ml on the morning of surgery, taken no later than 3h before the initiation of anesthesia. The patients' gastric empty capacity was measured by inserting a nasogastric tube to calculate the residuum and PH values of gastric content. Another variable described as APACHE-2 previously was measured to evaluate the patients' conditions . Blood glucose were measured immediately and serum insulin were sampled and following analyzed by radio immunoassay ( RJA ) at different time points during the course of preoperation, operation, and postoperation for both groups. And the insulin sensitivity at each point were calculated, using a formula named IAI described previously. The skeletal muscle and adipose tissue were sampled from the incision when the operation started, ongoing, and finished. The concentrations of the mRNAs corresponding tothe gene of GLUT4 were measured by RT-PCR,Results: It was showed that a quiet similar effect on gastric emptying and the same as the APACHE-2 values between the groups(P>0.05 ). Both the groups showed decreased insulin sensitivity immediately after surgery starting, and express a trend for constantly deterioration in IR. The relative reduction in insulin sensitivity was most pronounced on the 24 h after operation. Then the insulin sensitivity rose up slowly and returned to normal 7 days after operation. It was found that the preoperative oral glucose loading could attenuate immediate postoperative insulin resistance ( 1 h after surgery). Whole body insulin sensitivity decreased by 20.91% in the treatment group VS. 47.01% in the fasting group(f<0.05). The concentration of mRNA of GLUT4 of skeletal muscle showed no changes during operation. However, the content of mRNA of GLUT4 in samples of adipose exhibited a marked decline at the end of operation. Another finding lied in the fact that neither skeletal muscle nor adipose tissue show significant difference in the content of GLUT4 mRNA between the groups.Conclusion: Preoperative oral carbohydrate treatment could lead to a less reduced insulin sensitivity after CABG just as much safely and effectively as it do in the non-cardiac surgery. Adipose tissue show quitely different biological response to stress in the hand of transcription of GLUT4 gene, compared with its action in skeletal...
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