DIGAMI (Diabetes Mellitus, Insulin Glucose Infusion in Acute Myocardial Infarction): theory and practice

Acute Hyperglycemia Induced by Ketamine/Xylazine Anesthesia in Rats: Mechanisms and Implications for Preclinical Models

The effects of anesthetic agents, commonly used in animal models, on blood glucose levels in fed and fasted rats were investigated. In fed Sprague-Dawley rats, ketamine (100 mg/kg)/xylazine (10 mg/kg) (KX) produced acute hyperglycemia (blood glucose 178.4 ± 8.0 mg/dl) within 20 min. The baseline blood glucose levels (104.8 ± 5.7 mg/dl) reached maximum levels (291.7 ± 23.8 mg/dl) at 120 min. Ketamine alone did not elevate glucose levels in fed rats. Isoflurane also produced acute hyperglycemia similar to KX. Administration of pentobarbital sodium did not produce hyperglycemia in fed rats. In contrast, none of these anesthetic agents produced hyperglycemia in fasted rats. The acute hyperglycemic effect of KX in fed rats was associated with decreased plasma levels of insulin, adrenocorticotropic hormone (ACTH), and corticosterone and increased levels of glucagon and growth hormone (GH). The acute hyperglycemic response to KX was dose-dependently inhibited by the specific Α2-adrenergic receptor antagonist yohimbine (1–4 mg/kg). KX-induced changes of glucoregulatory hormone levels such as insulin, GH, ACTH, and corticosterone were significantly altered by yohimbine, whereas the glucagon levels remained unaffected. In conclusion, the present study indicates that both KX and isoflurane produce acute hyperglycemia in fed rats. The effect of KX is mediated by modulation of the glucoregulatory hormones through stimulation of Α2-adrenergic receptors. Pentobarbital sodium did not produce hyperglycemia in either fed or fasted rats. Based on these findings, it is suggested that caution needs to be taken when selecting anesthetic agents, and fed or fasted state of animals in studies of diabetic disease or other models where glucose and/or glucoregulatory hormone levels may influence outcome and thus interpretation. However, fed animals are of value when exploring the hyperglycemic response to anesthetic agents.

Superiority of moderate control of hyperglycemia to tight control in patients undergoing coronary artery bypass grafting

OBJECTIVE

Although consensus in cardiac surgery supports tight control of perioperative hyperglycemia (glucose<120 mg/dL), recent studies in critical care suggest moderate glycemic control may be superior. We sought to determine whether tight control or moderate glycemic control is optimal after coronary artery bypass grafting.

METHODS

From 1995 to 2008, a total of 4658 patients with known diabetes or perioperative hyperglycemia (preoperative glycosylated hemoglobin≥8 or postoperative serum glucose>126 mg/dL) underwent isolated coronary artery bypass grafting at our institution. Patients were stratified into 3 postoperative glycemic groups: tight (≤126 mg/dL), moderate (127-179 mg/dL), and liberal (≥180 mg/dL). Preoperative risk factors, glycemic management, and postoperative outcomes were analyzed.

RESULTS

Operative mortality was 2.5% (119/4658); major complication rate was 12.5% (581/4658). Relative to moderate group, more patients in tight group had preoperative renal failure (tight 16.4%, 22/134, moderate 8.3%, 232/2785, P=.001) and underwent emergent operations (tight 5.2%, 7/134, moderate 1.9%, 52/2785, P=.007); however, Society of Thoracic Surgeons predicted mortality risk was lower in tight group (P<.001). Moderate group had lowest mortality (tight 2.9%, 4/134, moderate 2.0%, 56/2785, liberal 3.4%, 59/1739, P=.02) and incidence of major complications (tight 19.4%, 26/134, moderate 11.1%, 308/2785, liberate 14.2%, 247/1739, P<.001). Risk-adjusted major complication incidence (adjusted odds ratio 0.7, 95% confidence interval 0.58-0.87) and mortality (adjusted odds ratio 0.6, 95% confidence interval 0.37-0.83) were lower with moderate glucose control than with tight or liberal management.

CONCLUSIONS

Moderate glycemic control was superior to tight glycemic control, with decreased mortality and major complications, and may be ideal for patients undergoing isolated coronary artery bypass grafting.

Differential effects of oral hypoglycemic agents on glucose control and cardiovascular risk

Cardiovascular disease (CVD) burden remains the predominant cause of mortality and morbidity in the United States and in most of the developed world. The ongoing twin epidemics of obesity and type 2 diabetes mellitus provide a groundswell source for sustaining this trend for the foreseeable future (increasing the prevalence of CVD by 2-4 times), unless radical changes are made in public health policy. Oral hypoglycemic agents (OHAs) remain a mainstay for management of type 2 diabetes in most practice settings. Although these agents are primarily prescribed to achieve better glycemic control, it is important to evaluate what effects they have on cardiovascular risk and whether there are significant differences in effects among the different OHAs. This review presents the available data on the effects of the various OHAs on cardiovascular risk surrogates and actual events in retrospective and prospective study design settings.

Smoking enhances absorption of insulin but reduces glucodynamic effects in individuals using the Lilly-Dura inhaled insulin system

AIM

To quantify the pharmacokinetic (PK) and glucodynamic (GD) impact of smoking on inhaled and subcutaneous (SC) insulin administration in healthy subjects.

METHODS

This study employed the euglycemic clamp procedure in a four-period, four-way randomized crossover design. Eight smoking and eight non-smoking healthy males were given SC insulin on two occasions and human insulin inhalation powder (HIIP) on two other occasions.

RESULTS

Smokers exhibited greater insulin exposure (AUC(0-t')) than non-smokers, following both routes of insulin administration (HIIP, P = 0.003, 58% increase; SC, P = 0.006, 24% increase). The maximum insulin concentration (C(max)) following HIIP was greater in smokers by 172% (P = 0.001) compared with non-smokers. The glucodynamic effects were greater in smokers following HIIP, consistent with the insulin concentration difference observed. However, maximum glucose response (R(max)) following SC was decreased by 36% (P = 0.001) and obtained later [time of maximum glucose response (TR(max)); P < 0.001] in smokers than in non-smokers. Smokers appeared less sensitive to insulin [total glucose infused during the clamp procedure normalised by total insulin exposure (G(tot))/AUC(0-t')] than non-smokers following both SC (P = 0.001) and inhaled (P = 0.011) routes of administration.

CONCLUSION

Smokers had substantially increased peak HIIP insulin concentration, but the glucodynamic effect was partially offset, most likely because of increased insulin resistance.

The Importance of Normoglycemia in Critically Ill Patients

Hyperglycemia is a risk factor for adverse outcomes in acutely ill patients with and without diabetes. One third of all patients admitted to tertiary care facilities have hyperglycemia, with approximately 12% having had no prior history of diabetes. Hyperglycemia adversely affects fluid balance, predisposes to infection, morbidity following acute cardiovascular events, and increases the risk for renal failure, polyneuropathy, and mortality in ICU patients. Because traditional thought suggests hypoglycemia presents a more serious risk to critically ill patients than does hyperglycemia, clinicians are often less than aggressive in treating blood glucoses under 200 mg/dl. Current research, however, demonstrates that even modest degrees of hyperglycemia are associated with adverse outcomes in critically ill patients. Safe implementation of normoglycemia in intensive care patients can be labor intensive and requires well-formulated treatment strategies and interdisciplinary support. Therefore, understanding the importance of intensive glucose control, being comfortable with current clinical treatment modalities, and having the necessary resources to provide this type of care, are vital to critical care nursing practice today.