Pro: tight intraoperative glucose control improves outcome in cardiovascular surgery

Perioperative Glycemic Management in Cardiac Surgery: A Narrative Review

Diabetes and hyperglycemic events in cardiac surgical patients are associated with postoperative morbidity and mortality. The causes of dysglycemia, the abnormal fluctuations in blood glucose concentrations, in the perioperative period include surgical stress, surgical techniques, medications administered perioperatively, and patient factors. Both hyperglycemia and hypoglycemia lead to poor outcomes after cardiac surgery. While trying to control blood glucose concentration tightly for better postoperative outcomes, hypoglycemia is the main adverse event. Currently, there is no definite consensus on the optimum perioperative blood glucose concentration to be maintained in cardiac surgical patients. This review provides an overview of perioperative glucose homeostasis, the pathophysiology of dysglycemia, factors that affect glycemic control in cardiac surgery, and current practices for glycemic control in cardiac surgery.

Insulin binding to the cardiopulmonary bypass biomaterials

Hyperglycemia associated with cardiopulmonary bypass (CPB) is an independent predictor of morbidity and mortality. One suggested cause of hyperglycemia during CPB is a decline of serum insulin concentrations. Since plasma C-proteins are not reduced during CPB — suggesting that pancreatic insulin secretion is not affected — the reduction of insulin concentrations is hypothesized to be due to the binding of the insulin protein to the CPB biomaterials. The hypothesis of this study is that insulin binds to the CPB polyvinyl chloride (PVC) tubing and that selected bio-coatings inhibit this process. Human insulin was diluted to a physiologic concentration of 30 μU/mL in saline and exposed to four types of sterile PVC tubing, namely: uncoated, Terumo X-coated, Medtronic Carmeda, and Cobe SMARxT for 30 minutes at 37°C. Insulin concentrations were determined with ELISA. The recovered insulin concentrations were found to be 9.3 ± 0.6 μU/mL in the uncoated (control), 17.7 ± 1.9 μU/mL in the X-coating, 17.9 ± 1.1 μU/mL in the Carmeda, and 14.28 ± 0.17 μU/mL in the SMARxT coated tubing. These data support the hypothesis that the insulin binding to the PVC tubing can be reduced by 48% and up to 35% with X-coating and Carmeda, and SMARxT coating, respectively. Therefore, the use of coated CPB systems is justified to reduce CPB-associated hyperglycemia. Perfusion (2007) 22, 207—210.

Pathophysiological Basis of CNS Injury in Cardiac Surgical Patients: Detection and Prevention

The current understanding of adverse central nervous system (CNS) events following cardiac surgery involves several identifiable, evidence-based mechanisms: athero-sclerotic emboli, microgaseous and microparticulate emboli, and hypoperfusion.1 Secondary factors, including patient co-morbidities and inherent genetic susceptibilities, as well as systemic inflammatory processes and a suboptimal metabolic milieu may interact to potentiate the extent of injury.2 In this review a number of these factors and their potential interactions will be explored with a view towards developing a comprehensive management strategy to minimize CNS injury.

Impact of the aspirated volume of fat tissue in the insulin resistance after liposuction

OBJECTIVE

To investigate insulin resistance imposed by liposuction, correlating its intensity with the extent of the operation.

METHODS

The sample consisted of 20 female patients without comorbidities, aged between 21 and 43 years, body mass index between 19 and 27 kg/m², undergoing liposuction alone or associated with breasts' prosthesis. We assessed insulin resistance at the beginning and end of the procedure by calculating the Homeostasis Model Assessment (HOMA-IR). The operative variables were length of liposuction, breast prosthesis time, body areas submitted to liposuction and total fat aspirated.

RESULTS

The liposuction time was 94-278 min (mean = 174 min), duration of breast prosthesis 20-140 min (mean = 65 min) and total fat aspirated 680-4280 g (mean = 1778 g). Statistical analysis was performed by considering a division line of 1500 g of aspirated fat and there was a significantly increased insulin resistance by HOMA index greater in the group > 1500 g (123% increase) than in the group d" 1500 g (an increase of 53 %) from the baseline data (p = 0.02). Other operative variables showed no significant correlation.

CONCLUSION

Insulin resistance shows significant increase in liposuction, and it is correlated to the volume of aspirated fat.

Avoiding stroke during cardiac surgery

The life saving benefits of cardiac surgery are frequently accompanied by negative side effects such as stroke, that occurs with an incidence of 2%-13% dependent to type of surgery. The etiology is most likely multifactorial with embolic events considered as main contributor. Although stroke presents a common complication, no guidelines for any routine use of pharmacological substances or non-pharmacological strategies exist to date. Non-pharmacological strategies include monitoring of brain oxygenation and perfusion with devices such as near infrared spectroscopy and Transcranial Doppler help. Epiaortic and transesophageal echocardiography visualize aorta pathology, enabling the surgeon to sidestep atheromatous segments. Additionally can the use of specially designed aortic cannulae and filters help to reduce embolization. Brain perfusion can be improved by using antero- or retrograde cerebral perfusion during deep hypothermic circulatory arrest, by tightly monitoring mean arterial blood pressure and hemodilution. Controlling perioperative temperature and glucose levels may additionally help to ameliorate secondary damage. Many pharmacological compounds have been shown to be neuroprotective in preclinical models, but clinical studies failed to confirm these results so far. Remacemide, an NMDA-receptor-antagonist showed a significant drug-based neuroprotection during cardiac surgery. Other substances currently assessed in clinical trials whose results are still pending are acadesine, an adenosine-regulating substance, the free radical scavenger edaravone and the local anesthetic lidocaine. Stroke remains as significant complication after cardiac surgery. Non-pharmacological strategies allow perioperative caregivers to detect injurious events and to ameliorate stroke and its sequelae. Considering the multi-factorial etiology though, stroke prevention will likely have to be addressed with an individualistic combination of different strategies and substances.

Anesthesia for patients with diabetes mellitus

PURPOSE OF REVIEW

Diabetes mellitus has diverse effects on all organ systems of the body. Insulin physiology and metabolic control are far more complex than previously thought. Research continues to reveal more information about the central role of insulin in metabolism. The treatment of hypertension and nephropathy as well as hyperglycemia in patients with diabetes has emerged as being critical for prevention of long-term diabetic complications. The issue of primary importance to the anesthesiologist is whether strict glycemic and hemodynamic control during the perioperative period affect outcome.

RECENT FINDINGS

Maintenance of euglycemia and physiologic control of insulin responses to changes in glucose levels have been shown to prolong life and reduce complications from diabetes mellitus. The identification and treatment of prediabetic patients may significantly delay the onset of overt diabetes. Perioperative control of glucose has become tighter, but the optimum level of glucose and ideal method of insulin delivery during surgery remain controversial. Perioperative control of blood pressure and vascular responses may be as important as glucose control for prevention of adverse perioperative events.

SUMMARY

Tight long-term control of glucose and blood pressure improve outcome in patients with diabetes. The same philosophy of management is being applied to the perioperative period. Routine measurement of intraoperative blood glucose levels and appropriate insulin administration are now standard practice, but the ideal regimen for insulin administration remains to be determined.

Attempted control of hyperglycemia during cardiopulmonary bypass fails to improve neurologic or neurobehavioral outcomes in patients without diabetes mellitus undergoing coronary artery bypass grafting

OBJECTIVE

Hyperglycemia worsens outcomes in critical illness. This randomized, double-blind, placebo-controlled clinical trial tested whether insulin treatment of hyperglycemia during cardiopulmonary bypass would reduce neurologic, neuro-ophthalmologic, and neurobehavioral outcomes after coronary artery bypass grafting.

METHODS

Three hundred eighty-one nondiabetic patients undergoing isolated coronary artery bypass grafting were given infusions of insulin or placebo when their blood glucose concentration exceeded 100 mg/dL during cardiopulmonary bypass. The primary outcome measure was the combined incidence of new neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death observed at 4 to 8 days postoperatively. This same measure was assessed secondarily at 6 weeks and 6 months. Length of hospital stay was also compared as a secondary assessment.

RESULTS

The 2 groups were well matched at baseline. The insulin-treated group had significantly lower blood glucose concentrations during bypass. Sixty-six percent of subjects in the insulin-treated group and 67% of subjects in the control group demonstrated a new or worsening neurologic, neuro-ophthalmologic, or neurobehavioral deficit or neurologic death at the 4- to 8-day assessment. Outcomes were also similar in the 2 groups at 6 weeks (37% and 39% incidence, respectively) and 6 months (30% and 25%, respectively). Median lengths of stay were 7 and 6 days, respectively, in the treatment and control groups. None of these outcome differences was statistically significant.

CONCLUSION

Attempted control of hyperglycemia during cardiopulmonary bypass had no significant effect on the combined incidence of neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death and failed to shorten the length of hospital stay. These results do not contradict those of other studies showing that aggressive control of hyperglycemia in the postoperative period will improve outcome.

Intraoperative glucose control in diabetic and nondiabetic patients during cardiac surgery

OBJECTIVE

The purpose of this study was to evaluate intraoperative glucose control.

DESIGN

Prospective unblinded study.

SETTING

Tertiary care center.

PARTICIPANTS

Diabetic (n = 17) and nondiabetic (n = 23) patients undergoing elective cardiac surgery.

INTERVENTIONS

Diabetics received a modified insulin regimen consisting of a fixed rate infusion of regular insulin, 10 U/m2/h, and a variable infusion of D10W, adjusted to maintain glucose between 101 to 140 mg/dL.

MEASUREMENTS AND MAIN RESULTS

Baseline glucose was higher in diabetics versus nondiabetics (mean +/- standard error of the mean: 203 +/- 27 v 117 +/- 3 mg/dL, p < 0.005). After baseline, insulin levels were increased in diabetics to 410 to 568 microU/mL. Corresponding insulin levels in nondiabetics were 12 to 40 microU/mL. Compared with baseline, glucose was decreased by 10% +/- 29% in diabetics during hypothermic cardiopulmonary bypass and increased by 21% +/- 30% in nondiabetics (p < 0.005). After discontinuation of bypass, glucose was lower in diabetics (137 +/- 12 mg/dL) versus nondiabetics (162 +/- 8 mg/dL, p < 0.005). Nine diabetics had adequate intraoperative glycemic control during hypothermic bypass (glucose 123 +/- 8 mg/dL, insulin 550 +/- 68 microU/mL, glucose infusion rate 1.87 +/- 0.29 mg/kg/min), 6 approached adequate control near the end of surgery (glucose 147 +/- 8 mg/dL, insulin 483 +/- 86 microU/mL, glucose infusion rate 0.35 +/- 0.05 mg/kg/min), and 2 never achieved control. Diabetics with elevated initial glucose >300 mg/dL did not achieve adequate glycemic control. Four diabetics (3 with renal failure) required injection of 50% dextrose after bypass for hypoglycemia.

CONCLUSION

Adequate glycemic control can be achieved in most diabetics during cardiac surgery using a modified insulin clamp technique provided initial glucose is <300 mg/dL.

Perioperative management of a child with glycogen storage disease type III undergoing cardiopulmonary bypass and repair of an atrial septal defect

The glycogen storage diseases (GSD) are a heterogenous group of inherited disorders involving one of the several steps of glycogen synthesis or degradation. Type III GSD, also known as Cori's or Forbe's disease, results from a deficiency of the enzyme, amylo-1,6-glucosidase, which is responsible for the breakdown or debranching of the glycogen molecule during catabolism. As a result of this deficiency, inadequate glycogen breakdown occurs, resulting in hypoglycaemia during periods of fasting or stress, as well as storage of excessive glycogen, predominantly in the liver. Glycogen accumulation in the liver leads to hepatogmegaly and, in some instances, hepatic dysfunction with cirrhosis in the third and fourth decades of life. Additionally, deficiency of the enzyme in skeletal and cardiac muscle can lead to skeletal muscle weakness and cardiomyopathy. We present a 28-month-old girl who presented for anaesthetic care for cardiopulmonary bypass and closure of an atrial septal defect. The potential perioperative implications of GSD type III are discussed.