Tight perioperative glucose control is associated with a reduction in renal impairment and renal failure in non-diabetic cardiac surgical patients

Preoperative fasting glucose value can predict acute kidney injury in non-cardiac surgical patients without diabetes but not in patients with diabetes

BACKGROUND

Postoperative acute kidney injury (AKI) is a common and costly complication after non-cardiac surgery. Patients with or without diabetes could develop hyperglycemia before surgery, and preoperative hyperglycemia was closely associated with postoperative poor outcomes, but the association between preoperative fasting blood glucose level and postoperative AKI is still unclear.

METHODS

Data from patients undergoing non-cardiac surgery in Chongqing University Cancer Hospital from January 1, 2017, to May 31, 2023, were collected, preoperative glucose value and perioperative variables were extracted, the primary exposure of interest was preoperative glucose value, and the outcome was postoperative AKI.

RESULTS

Data from 39,986 patients were included in the final analysis, 741(1.9%) patients developed AKI, 134(5.6%) in the cohort with DM, and 607(1.6%) in the cohort without DM(OR 1.312, 95% CI 1.028-1.675, P = 0.029). A significant non-linear association between preoperative glucose and AKI exists in the cohort without DM after covariable adjustment (P = 0.000), and every 1 mmol/L increment of preoperative glucose level increased OR by 15% (adjusted OR 1.150, 95% CI 1.078-1.227, P = 0.000), the optimal cut-point of preoperative fasting glucose level to predict AKI was 5.39 mmol/L (adjusted OR 1.802, 95%CI 1.513-2.146, P = 0.000). However, in the cohort with DM, the relation between preoperative glucose and postoperative AKI was not significant after adjusting by covariables (P = 0.437). No significance exists between both cohorts in the risk of AKI over the range of preoperative glucose values.

CONCLUSION

A preoperative fasting glucose value of 5.39 mmol/L can predict postoperative acute kidney injury after non-cardiac surgery in patients without diagnosed diabetes, but it is not related to AKI in patients with the diagnosis.

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.

Glycemic targets in critically ill adults: A mini-review

Illness-induced hyperglycemia impairs neutrophil function, increases pro-inflammatory cytokines, inhibits fibrinolysis, and promotes cellular damage. In turn, these mechanisms lead to pneumonia and surgical site infections, prolonged mechanical ventilation, prolonged hospitalization, and increased mortality. For optimal glucose control, blood glucose measurements need to be done accurately, frequently, and promptly. When choosing glycemic targets, one should keep the glycemic variability < 4 mmol/L and avoid targeting a lower limit of blood glucose < 4.4 mmol/L. The upper limit of blood glucose should be set according to casemix and the quality of glucose control. A lower glycemic target range (i.e., blood glucose 4.5-7.8 mmol/L) would be favored for patients without diabetes mellitus, with traumatic brain injury, or who are at risk of surgical site infection. To avoid harm from hypoglycemia, strict adherence to glycemic control protocols and timely glucose measurements are required. In contrast, a higher glycemic target range (i.e., blood glucose 7.8-10 mmol/L) would be favored as a default choice for medical-surgical patients and patients with diabetes mellitus. These targets may be modified if technical advances for blood glucose measurement and control can be achieved.

The effect of glucose control in liver surgery on glucose kinetics and insulin resistance

BACKGROUND & AIMS

Clinical outcome is negatively correlated to postoperative insulin resistance and hyperglycemia. The magnitude of insulin resistance can be modulated by glucose control, preoperative nutrition, adequate pain management and minimal invasive surgery. Effects of glucose control on perioperative glucose kinetics in liver surgery is less studied.

METHODS

18 patients scheduled for open hepatectomy were studied per protocol in this prospective, randomized study. In the treatment group (n = 9), insulin was administered intravenously to keep arterial blood glucose between 6 and 8 mmol/l during surgery. The control group (n = 9) received insulin if blood glucose >11.5 mmol/l. Insulin sensitivity was measured by an insulin clamp on the day before surgery and immediately postoperatively. Glucose kinetics were assessed during the clamp and surgery.

RESULTS

Mean intraoperative glucose was 7.0 mM (SD 0.7) vs 9.1 mM (SD 1.9) in the insulin and control group respectively (p < 0.001; ANOVA). Insulin sensitivity decreased in both groups but significantly (p = 0.03, ANOVA) more in the control group (M value: 4.6 (4.4-6.8) to 2.1 (1.2-2.6) and 4.6 (4.1-5.0) to 0.6 (0.1-1.8) mg/kg/min in the treatment and control group respectively). Endogenous glucose production (EGP) increased and glucose disposal (WGD) decreased significantly between the pre- and post-operative clamps in both groups, with no significant difference between the groups. Intraoperative kinetics demonstrated that glucose control decreased EGP (p = 0.02) while WGD remained unchanged (p = 0.67).

CONCLUSION

Glucose control reduces postoperative insulin resistance in liver surgery. EGP increases and WGD is diminished immediately postoperatively. Insulin seems to modulate both reactions, but mostly the WGD is affected. Intraoperative EGP decreased while WGD remained unaltered.

REGISTRATION NUMBER OF CLINICAL TRIAL

ANZCTR 12614000278639.

Increased Carotid Intima-Media Thickness was not Associated With Cognitive Dysfunction After Off-Pump Coronary Surgery in Older Adult Patients Without Carotid Stenosis

Increased carotid intima-media thickness (C-IMT), a marker of atherosclerosis, is known to be associated with cerebrovascular and cortical abnormalities and cognitive impairment. This prospective observational study investigated the association between increased C-IMT and postoperative cognitive dysfunction (POCD) in older adult patients undergoing off-pump coronary artery bypass surgery. A total of 201 patients (57 females, 144 males; >60 years) were classified into increased (n = 105) or normal (n = 96) C-IMT groups by a cut-off value of 0.9 mm (bilateral C-IMT mean). Cognitive function was serially assessed with the Korean Mini-Mental State Examination, and Korean Montreal Cognitive Assessment scores preoperatively and at 7 days and 3 months postoperatively. POCD was defined as the deterioration of 1 standard deviation in at least one of the postoperative tests compared with their corresponding baseline scores. Independent risk factors for POCD were evaluated using multivariable analysis. Overall, POCD occurred in 46 patients (23%) over the 3 months. The incidences of POCD at 7 days and 3 months after surgery were similar, and there was no difference in both Korean Mini-Mental State Examination and Korean Montreal Cognitive Assessment test scores before and after surgery between groups. Chronic obstructive lung disease and intraoperative hyperglycemia episodes (>180 mg/dL), but not increased C-IMT, were independent risk factors for POCD. Unlike in nonsurgical cohorts, increased C-IMT was not significantly associated with the occurrence of POCD in older adult patients undergoing off-pump coronary artery bypass surgery.

Intraoperative hyperglycemia in patients with an elevated preoperative C-reactive protein level may increase the risk of acute kidney injury after cardiac surgery

PURPOSE

The effect of hyperglycemia on acute kidney injury (AKI) in patients undergoing cardiac surgery is unclear and may involve as yet unexplored factors. We hypothesized differential effects of intraoperative hyperglycemia on AKI after cardiac surgery depending on baseline inflammatory status, as reflected by the C-reactive protein (CRP) level.

METHODS

This retrospective study included patients who underwent cardiac surgery seen at our hospital from 2008 to 2018. Patients were classified into four groups according to their preoperative CRP level (≥ 1 or < 1 mg/dl) and their intraoperative time-weighted average glucose concentration (> 140 or ≤ 140 mg/dl): low CRP and normoglycemia, low CRP and hyperglycemia, high CRP and normoglycemia, and high CRP and hyperglycemia. The data were analyzed by multivariable logistic regression analysis.

RESULTS

The data of 3625 patients were analyzed. The logistic regression showed that patients in the high CRP and hyperglycemia group had a significantly higher risk of AKI than patients in the low CRP and normoglycemia group [odds ratio (OR), 1.58; 95% confidence interval (CI) 1.10-2.27], low CRP with hyperglycemia group (OR, 1.69; 95% CI 1.16-2.47) and high CRP with normoglycemia group (OR, 1.50; 95% CI 1.01-2.23).

CONCLUSIONS

Intraoperative hyperglycemia in patients with an elevated preoperative CRP level was significantly related to an increased risk of AKI after cardiac surgery. Individualized perioperative glycemic control may therefore be necessary in these patients.

Standardized Glycemic Management versus Conventional Glycemic Management and Postoperative Outcomes in Type 2 Diabetes Patients Undergoing Elective Surgery

PURPOSE

Optimized postoperative blood glucose control can minimize postoperative complications. Conventional perioperative glycemic control protocol (CG), which has been routinely used in our institution, lacks detailed perioperative glycemic management. A new standardized glycemic control protocol (SG) was designed which employs frequent postoperative monitoring of blood glucose, more tightly targeted blood glucose control, and adjustment of insulin dosage prior to surgery. This study compared the efficacy of postoperative glycemic control and complications with the two protocols, CG and SG.

PATIENTS AND METHODS

Three hundred and eighty type 2 diabetes patients who underwent elective surgeries were included in the study. Of those, 182 patients with CG were identified retrospectively as a historical control cohort. Additional 198 patients with SG were prospectively enrolled. Covariate imbalance was controlled using propensity score matching. Outcomes were evaluated using regression analysis clustered by type of surgery.

RESULTS

The SG group had lower mean levels of postoperative 24-hr blood glucose than the CG group (β =-8.6 mg/dL; 95% CI (-16.5 to -7.9), p=0.042). In SG group, the incidence of ICU admission and of acute kidney injury after surgery was lower than in the CG group (OR 0.36; 95% CI (0.18-0.74), p=0.005 and OR=0.59; 95% CI (0.41-0.85), p=0.005, respectively). There was no significant difference in postoperative hypoglycemia, infection, cardiovascular complications, stroke, or mortality rate between the two groups.

CONCLUSION

For type 2 diabetes patients undergoing elective surgery, the SG protocol is more effective in controlling blood glucose. The protocol can also reduce the incidence of some postoperative complications compared to CG with no increased risk of hypoglycemia.

Effects of Preoperative HbA1c Levels on the Postoperative Outcomes of Coronary Artery Disease Surgical Treatment in Patients with Diabetes Mellitus and Nondiabetic Patients: A Systematic Review and Meta-Analysis

AIMS

To investigate the effect of preoperative HbA1c levels on the postoperative outcomes of coronary artery disease surgery in diabetic and nondiabetic patients.

METHODS AND RESULTS

The MEDLINE (via PubMed), Cochrane Library, Web of Science, Embase, Wanfang Data, China National Knowledge Infrastructure (CNKI), and Chinese Biology Medicine (CBM) databases were used to search the effects of different preoperative HbA1c levels on the postoperative outcomes of coronary artery disease surgical treatment in diabetic and nondiabetic patients from inception to December 2018. Two review authors worked in an independent and duplicate manner to select eligible studies, extract data, and assess the risk of bias of the included studies. We used a meta-analysis to synthesize data and analyze subgroups, sensitivity, and publication bias as well as the GRADE methodology if appropriate. The literature search retrieved 886 records initially, and 23 cohort studies were included in the meta-analysis. In this meta-analysis, we found that there was a reduced incidence of surgical site infections (OR = 2.94, 95% CI 2.18-3.98), renal failure events (OR = 1.63, 95% CI 1.13-2.33), and myocardial infarction events (OR = 1.69, 95% CI 1.16-2.47), as well as a shortened hospital stay (MD = 1.08, 95% CI 0.46-1.71), in diabetic patients after coronary artery disease surgical treatment with lower preoperative HbA1c levels. For nondiabetic patients, a higher preoperative HbA1c level resulted in an increase in the incidence of mortality (OR = 2.23, 95% CI 1.01-4.90) and renal failure (OR = 2.33, 95% CI 1.32-4.12). No significant difference was found between higher and lower preoperative HbA1c levels in the incidence of mortality (OR = 1.06, 95% CI 0.88-1.26), stroke (OR = 1.49, 95% CI 0.94-2.37), or atrial fibrillation (OR = 0.94, 95% CI 0.67-1.33); the length of ICU stay (MD = 0.20, 95% CI -0.14-0.55); or sepsis incidence (OR = 2.49, 95% CI 0.99-6.25) for diabetic patients or for myocardial infarction events (OR = 1.32, 95% CI 0.27-6.31) or atrial fibrillation events (OR = 0.99, 95% CI 0.74-1.33) for nondiabetic patients. The certainty of evidence was judged to be moderate or low.

CONCLUSION

This meta-analysis showed that higher preoperative HbA1c levels may potentially increase the risk of surgical site infections, renal failure, and myocardial infarction and reduce the length of hospital stay in diabetic subjects after coronary artery disease surgical treatment and increase the risk of mortality and renal failure in nondiabetic patients. However, there was great inconsistency in defining higher preoperative HbA1c levels in the studies included; we still need high-quality RCTs with a sufficiently large sample size to further investigate this issue in the future. This trial is registered with CRD42019121531.

Intraoperative hyperglycemia increases the incidence of postoperative delirium

BACKGROUND

Hyperglycemia frequently occurs during major surgery and is associated with adverse postoperative outcomes. This study aimed to investigate the influence of intraoperative hyperglycemia on incidences of postoperative delirium (POD) and postoperative cognitive dysfunction (POCD).

METHODS

Eighty-seven patients aged ≥65 years undergoing elective surgery were included in this prospective observational subproject of the BioCog study. Blood glucose (BG) levels were measured every 20 minutes intraoperatively. Hyperglycemia was defined as BG levels ≥150 mg·dL-1. Patients were assessed for POD twice daily until postoperative day 7. The occurrence of POCD was determined three months after surgery. Multivariable logistic regression was used to identify associations between hyperglycemia and POD as well as POCD. Secondary endpoints comprised duration of hyperglycemia, maximum glucose level (Glucosemax) and differences between diabetic and non-diabetic patients.

RESULTS

POD occurred in 41 (47.1%), POCD in five (15.2%) patients. In two separate multivariable logistic regression models, hyperglycemia was significantly associated with POD (OR 3.86 [CI 95% 1.13, 39.49], P=0.044) but not POCD (3.59 [NaN, NaN], P=0.157). Relative duration of hyperglycemia was higher in POD patients compared to patients without POD (20 [0; 71] % versus 0 [0; 55] %, P=0.075), whereas the maximum glucose levels during surgery were similar between the two groups. Considering only non-diabetic patients, relative duration of hyperglycemia (P=0.003) and Glucosemax (P=0.015) were significantly higher in patients with POD.

CONCLUSIONS

Intraoperative hyperglycemia was independently associated with POD but not POCD. Relative duration of hyperglycemia appeared thereby to also play a role. Especially hyperglycemic non-diabetic patients might be at high risk for POD.

Glucose control in the ICU

PURPOSE OF REVIEW

Critically ill patients usually develop hyperglycemia, which is associated with adverse outcome. Controversy exists whether the relationship is causal or not. This review summarizes recent evidence regarding glucose control in the ICU.

RECENT FINDINGS

Despite promising effects of tight glucose control in pioneer randomized controlled trials, the benefit has not been confirmed in subsequent multicenter studies and one trial found potential harm. This discrepancy could be explained by methodological differences between the trials rather than by a different case mix. Strategies to improve the efficacy and safety of tight glucose control have been developed, including the use of computerized treatment algorithms.

SUMMARY

The ideal blood glucose target remains unclear and may depend on the context. As compared with tolerating severe hyperglycemia, tight glucose control is well tolerated and effective in patients receiving early parenteral nutrition when provided with a protocol that includes frequent, accurate glucose measurements and avoids large glucose fluctuations. All patient subgroups potentially benefit, with the possible exception of patients with poorly controlled diabetes, who may need less aggressive glucose control. It remains unclear whether tight glucose control is beneficial or not in the absence of early parenteral nutrition.

Comparison of intensive insulin therapy and conventional glucose management in patients undergoing coronary artery bypass grafting

Background and Aims

Hyperglycemia during cardiac surgery is a risk factor for postoperative outcomes. Because incidence of diabetes mellitus is increasing in Indian population, we tried to evaluate the western protocol for strict control of blood sugar perioperatively. The main aim of the study was to evaluate glycemic control during coronary artery bypass grafting and to determine whether intensive insulin therapy (IIT) is better than the conventional one.

Material and Methods

A prospective randomized comparative study was conducted to evaluate IIT and conventional management of glucose in 40 patients undergoing on-pump coronary artery bypass grafting. Outcomes measured were incidence of hyperglycemia or hypoglycemia, incidence of hypokalemia, prolonged intubation, wound infections, strokes, acute renal failure, new onset arrhythmias, length of stay in ICU and hospital, cardiac arrest and mortality. The statistical analysis was done by using Chi-square test, and paired and unpaired t test.

Results

The diabetic patients had significantly higher mean blood sugar and insulin requirement. The incidence of hyperglycemia was significantly higher in conventional management of blood sugar (P = 0.001), whereas hypoglycemia (P = 0.047) and hypokalemia (P = 0.020) were significantly higher in IIT. There were no significant difference in the incidence of prolonged intubation, wound infection, length of ICU and hospital stay, strokes, acute renal failure, new onset arrhythmias, cardiac arrest, and mortality.

Conclusion

The IIT did not improve the morbidity and mortality in our patients undergoing coronary artery bypass grafting.

Wider intraoperative glycemic fluctuation increases risk of acute kidney injury after pediatric cardiac surgery

OBJECTIVE

The association between poor intraoperative glycemic control and postoperative acute kidney injury (AKI) in adult cardiac surgery has been observed, but data in the pediatrics remain unknown. We performed a hypothesis that intraoperative hyperglycemia and/or wider glycemic fluctuation were associated with the incidence of postoperative AKI in pediatric cardiac surgery.

METHODS

A retrospective study was performed in pediatrics who underwent cardiac surgery from 2013 to 2016. Perioperative glycemic data up to 48 hours after surgery were collected and analyzed. Patients with AKI were matched 1:1 with patients without AKI by a propensity score. Variables of demographic data, preoperative renal function and glycemic level, perioperative cardiac condition were matched.

RESULTS

The incidence of AKI was 11.5% (118/1026), with 53.4% (63/118), 30.5% (36/118), and 16.1% (19/118) categorized as AKIN stages I, II, and III, respectively. Children who experienced AKI were younger and cyanotic, underwent more complex surgeries, had higher peak intraoperative glucose levels, wider intraoperative glycemic fluctuation, greater inotropic scores and more transfusions, and poor outcomes (all p < .05). After matching, the AKI group had significantly wider intraoperative glycemic fluctuation (p < .05). Logistic regression showed intraoperative glycemic fluctuation was one of the risk factors for AKI (p = .033) and degree of AKI severity stage increased when the glycemic fluctuation increased (p < .01).

CONCLUSIONS

Wider intraoperative glycemic fluctuation, but not hyperglycemia, was associated with an increased incidence of postoperative AKI after pediatric cardiac surgery.

Association of Elevated Pre-operative Hemoglobin A1c and Post-operative Complications in Non-diabetic Patients: A Systematic Review

IMPORTANCE

Pre-operative hyperglycemia is associated with post-operative adverse outcomes in diabetic and non-diabetic patients. Current pre-operative screening includes random plasma glucose, yet plasma glycated hemoglobin (HbA1c) is a better measure of long-term glycemic control. It is not clear whether pre-operative HbA1c can identify non-diabetic patients at risk of post-operative complications.

OBJECTIVE

The systematic review summarizes the evidence pertaining to the association of suboptimal pre-operative HbA1c on post-operative outcomes in adult surgical patients with no history of diabetes mellitus.

EVIDENCE REVIEW

A detailed search strategy was developed by a librarian to identify all the relevant studies to date from the major online databases.

FINDINGS

Six observational studies met all the eligibility criteria and were included in the review. Four studies reported a significant association between pre-operative HbA1c levels and post-operative complications in non-diabetic patients. Two studies reported increased post-operative infection rates, and two reported no difference. Of four studies assessing the length of stay, three did not observe any association with HbA1c level and only one study observed a significant impact. Only one study found higher mortality rates in patients with suboptimal HbA1c.

CONCLUSIONS AND RELEVANCE

Based on the limited available evidence, suboptimal pre-operative HbA1c levels in patients with no prior history of diabetes predict post-operative complications and represent a potentially modifiable risk factor.

Critical Care Management of Stress-Induced Hyperglycemia

PURPOSE OF REVIEW

We discuss key studies that have set the scene for the debate on the efficacy and safety of tight glycemic control in critically ill patients, highlighting important differences among them, and describe the ensuing search towards strategies for safer glucose control.

RECENT FINDINGS

Differences in level of glycemic control, glucose measurement and insulin administration, expertise, and nutritional management may explain the divergent outcomes of the landmark studies on tight glycemic control in critical illness. Regarding strategies towards safer glucose control, several computerized algorithms have shown promise, but lack validation in adequately powered outcome studies. Real-time continuous glucose monitoring and closed loop blood glucose control systems are not up to the task yet due to technical challenges, though recent advances are promising. Alternatives for insulin have only been investigated in small feasibility studies. Severe hyperglycemia in critically ill patients generally is not tolerated anymore, but the optimal blood glucose target may depend on the specific patient and logistic context.

Endocrine and Metabolic Alterations in Sepsis and Implications for Treatment

Sepsis induces profound neuroendocrine and metabolic alterations. During the acute phase, the neuroendocrine changes are directed toward restoration of homeostasis, and also limit unnecessary energy consumption in the setting of restricted nutrient availability. Such changes are probably adaptive. In patients not recovering quickly, a prolonged critically ill phase may ensue, with different neuroendocrine changes, which may represent a maladaptive response. Whether stress hyperglycemia should be aggressively treated or tolerated remains a matter of debate. Until new evidence from randomized controlled trials becomes available, preventing severe hyperglycemia is recommended. Evidence supports withholding parenteral nutrition in the acute phase of sepsis.

Acute Kidney Injury After Pediatric Cardiac Surgery: A Secondary Analysis of the Safe Pediatric Euglycemia After Cardiac Surgery Trial

OBJECTIVES

To understand the effect of tight glycemic control on cardiac surgery-associated acute kidney injury.

DESIGN

Secondary analysis of data from the Safe Pediatric Euglycemia after Cardiac Surgery trial of tight glycemic control versus standard care.

SETTING

Pediatric cardiac ICUs at University of Michigan, C.S. Mott Children's Hospital, and Boston Children's Hospital.

PATIENTS

Children 0-36 months old undergoing congenital cardiac surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Cardiac surgery-associated acute kidney injury was assigned using the Acute Kidney Injury Network criteria with the modification that a greater than 0.1 mg/dL increase in serum creatinine was required to assign cardiac surgery-associated acute kidney injury. We explored associations between cardiac surgery-associated acute kidney injury and tight glycemic control and clinical outcomes. Of 799 patients studied, cardiac surgery-associated acute kidney injury occurred in 289 patients (36%), most of whom had stage II or III disease (72%). Cardiac surgery-associated acute kidney injury rates were similar between treatment groups (36% vs 36%; p = 0.99). Multivariable modeling showed that patients with cardiac surgery-associated acute kidney injury were younger (p = 0.002), underwent more complex surgery (p = 0.005), and had longer cardiopulmonary bypass times (p = 0.002). Cardiac surgery-associated acute kidney injury was associated with longer mechanical ventilation and ICU and hospital stays and increased mortality. Patients at University of Michigan had higher rates of cardiac surgery-associated acute kidney injury compared with Boston Children's Hospital patients (66% vs 15%; p < 0.001), but University of Michigan patients with cardiac surgery-associated acute kidney injury had shorter time to extubation and ICU and hospital stays compared with Boston Children's Hospital patients.

CONCLUSIONS

Tight glycemic control did not reduce the cardiac surgery-associated acute kidney injury rate in this trial cohort. We observed significant differences in cardiac surgery-associated acute kidney injury rates between the two study sites, and there was a differential effect of cardiac surgery-associated acute kidney injury on clinical outcomes by site. These findings warrant further investigation to identify causal variation in perioperative practices that affect cardiac surgery-associated acute kidney injury epidemiology.

Effect of moderately intense perioperative glucose control on renal allograft function: a pilot randomized controlled trial in renal transplantation

Recipient diabetes accounts for ~34% of end-stage renal disease in patients awaiting renal transplantation and has been linked to poor graft function. We conducted a single-center, open-label, randomized controlled trial to determine whether moderately intense glucose control during allograft reperfusion would reduce the incidence of poor graft function. Adult diabetics undergoing deceased donor renal transplant were randomized to moderately intense glucose control (n=30) or standard control (n=30). The primary outcome was poor graft function (dialysis within seven days of transplant or failure of serum creatinine to fall by 10% for three consecutive days). Recipients with moderately intense glucose control had less poor graft function in the intention-to-treat (43.3% vs 73.3%, P=.02) and per-protocol analysis (43.2% vs 81%, P<.01). Recipients with moderately intense control also had higher glomerular filtration rate (GFR) at 30 days after transplant in the per-protocol and intention-to-treat analyses. There were no episodes of severe hypoglycemia in either group and no differences in mortality, seizures, stroke, graft loss, or biopsy-proven rejection. Moderately intense glucose control at the time of allograft reperfusion reduces the incidence of poor graft function in diabetic renal transplant recipients and improves glomerular filtration rate at 30 days.

Prediction and Prevention of Acute Kidney Injury after Cardiac Surgery

The incidence of acute kidney injury after cardiac surgery (CS-AKI) ranges from 33% to 94% and is associated with a high incidence of morbidity and mortality. The etiology is suggested to be multifactorial and related to almost all aspects of perioperative management. Numerous studies have reported the risk factors and risk scores and novel biomarkers of AKI have been investigated to facilitate the subclinical diagnosis of AKI. Based on the known independent risk factors, many preventive interventions to reduce the risk of CS-AKI have been tested. However, any single preventive intervention did not show a definite and persistent benefit to reduce the incidence of CS-AKI. Goal-directed therapy has been considered to be a preventive strategy with a substantial level of efficacy. Many pharmacologic agents were tested for any benefit to treat or prevent CS-AKI but the results were conflicting and evidences are still lacking. The present review will summarize the current updated evidences about the risk factors and preventive strategies for CS-AKI.

Prevention and Treatment of Cardiac Surgery Associated Acute Kidney Injury

AIM OF REVIEW

Acute kidney injury (AKI) after cardiac surgery is a relatively common postoperative complication and is independently related to increased mortality and morbidity.

METHOD

In this review, we will focus on risk factors of developing AKI, early detection by biomarkers and preventive strategies for AKI after adult cardiac surgery.

RECENT FINDINGS

Many perioperative factors affect renal function and acute AKI following cardiac surgery. Novel biomarkers of kidney injury such as neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), cystatin C (CysC), have the potential to facilitate the early diagnosis of cardiac surgery associated AKI (CSA-AKI). Pharmacological interventions have been inconsistent to their efficacy, and to date, there is no compelling pharmacologic agent known to reduce the risk of AKI or treat established AKI.

SUMMARY

Preventive strategies of AKI focus on optimal perioperative management.

Hyperglycemia and Acute Kidney Injury During the Perioperative Period

Hyperglycemia and acute kidney injury (AKI) are frequently observed during the perioperative period. Substantial evidence indicates that hyperglycemia increases the prevalence of AKI as a surgical complication. Patients who develop hyperglycemia and AKI during the perioperative period are at significantly elevated risk for poor outcomes such as major adverse cardiac events and all-cause mortality. Early observational and interventional trials demonstrated that the use of intensive insulin therapy to achieve strict glycemic control resulted in remarkable reductions of AKI in surgical populations. However, more recent interventional trials and meta-analyses have produced contradictory evidence questioning the renal benefits of strict glycemic control. Although the exact mechanisms through which hyperglycemia increases the risk of AKI have not been elucidated, multiple pathophysiologic pathways have been proposed. Hypoglycemia and glycemic variability may also play a significant role in the development of AKI. In this literature review, the complex relationship between hyperglycemia and AKI as well as its impact on clinical outcomes during the perioperative period is explored.

Association Between the Neutrophil/Lymphocyte Ratio and Acute Kidney Injury After Cardiovascular Surgery: A Retrospective Observational Study

A high neutrophil-lymphocyte ratio (N/L ratio) was associated with the development of acute kidney injury (AKI) in patients with severe sepsis. We sought to investigate the association between the perioperative N/L ratios and postoperative AKI in patients undergoing high-risk cardiovascular surgery.A retrospective medical chart review was performed of 590 patients who underwent cardiovascular surgeries, including coronary artery bypass, valve replacement, patch closure for atrial or ventricular septal defect and surgery on the thoracic aorta with cardiopulmonary bypass (CPB). Baseline perioperative clinical parameters, including N/L ratios measured before surgery, immediately after surgery, and on postoperative day (POD) one were obtained. Multivariate logistic regression analysis was used to evaluate risk factors.A total of 166 patients (28.1%) developed AKI defined by the KDIGO (kidney disease improving global outcomes) criteria in the first 7 PODs. Independent risk factors for AKI included old age, decreased left ventricular systolic function, preoperative high serum creatinine, low serum albumin and high uric acid levels, intraoperative large transfusion amount, oliguria, hyperglycemia, and elevated N/L ratio measured immediately after surgery and on POD one. The quartiles of immediately postoperative N/L ratio were associated with graded increase in risk of AKI development (fourth quartile [N/L ratio≥10] multivariate odds ratio 5.90, 95% confidence interval [CI] 2.74-12.73; P < 0.001), a longer hospital stay, and a higher in-hospital and 1-year mortality rate (fourth quartile [N/L ratio≥10] adjusted hazard ratio for 1-year mortality [8.40, 95% CI 2.50-28.17]; P < 0.001).In patients undergoing cardiovascular surgery with CPB, elevated N/L ratios in the immediately postoperative period and on POD one were associated with an increased risk of postoperative AKI and 1-year mortality. The N/L ratio, which is easily calculable from routine work-up, can therefore assist with risk stratification of AKI and mortality in high-risk surgical patients.

Clinical Risk Scoring Models for Prediction of Acute Kidney Injury after Living Donor Liver Transplantation: A Retrospective Observational Study

Acute kidney injury (AKI) is a frequent complication of liver transplantation and is associated with increased mortality. We identified the incidence and modifiable risk factors for AKI after living-donor liver transplantation (LDLT) and constructed risk scoring models for AKI prediction. We retrospectively reviewed 538 cases of LDLT. Multivariate logistic regression analysis was used to evaluate risk factors for the prediction of AKI as defined by the RIFLE criteria (RIFLE = risk, injury, failure, loss, end stage). Three risk scoring models were developed in the retrospective cohort by including all variables that were significant in univariate analysis, or variables that were significant in multivariate analysis by backward or forward stepwise variable selection. The risk models were validated by way of cross-validation. The incidence of AKI was 27.3% (147/538) and 6.3% (34/538) required postoperative renal replacement therapy. Independent risk factors for AKI by multivariate analysis of forward stepwise variable selection included: body-mass index >27.5 kg/m² [odds ratio (OR) 2.46, 95% confidence interval (CI) 1.32–4.55], serum albumin <3.5 mg/dl (OR 1.76, 95%CI 1.05–2.94), MELD (model for end-stage liver disease) score >20 (OR 2.01, 95%CI 1.17–3.44), operation time >600 min (OR 1.81, 95%CI 1.07–3.06), warm ischemic time >40 min (OR 2.61, 95%CI 1.55–4.38), postreperfusion syndrome (OR 2.96, 95%CI 1.55–4.38), mean blood glucose during the day of surgery >150 mg/dl (OR 1.66, 95%CI 1.01–2.70), cryoprecipitate > 6 units (OR 4.96, 95%CI 2.84–8.64), blood loss/body weight >60 ml/kg (OR 4.05, 95%CI 2.28–7.21), and calcineurin inhibitor use without combined mycophenolate mofetil (OR 1.87, 95%CI 1.14–3.06). Our risk models performed better than did a previously reported score by Utsumi et al. in our study cohort. Doses of calcineurin inhibitor should be reduced by combined use of mycophenolate mofetil to decrease postoperative AKI. Prospective randomized trials are required to address whether artificial modification of hypoalbuminemia, hyperglycemia and postreperfusion syndrome would decrease postoperative AKI in LDLT.

Potentially modifiable risk factors for acute kidney injury after surgery on the thoracic aorta: a propensity score matched case-control study

Perioperative risk factors were identified for acute kidney injury (AKI) defined by the RIFLE criteria (RIFLE = risk, injury, failure, loss, end stage) after surgery on the thoracic aorta with cardiopulmonary bypass (CPB) in this case-control study. A retrospective review was completed for 702 patients who underwent surgery on the thoracic aorta with CPB. A total of 183 patients with AKI were matched 1:1 with patients without AKI by a propensity score. Matched variables included age, gender, body-mass index, preoperative creatinine levels, estimated glomerular filtration rate, a history of hypertension, diabetes mellitus, cerebrovascular accident, smoking history, or chronic obstructive pulmonary disease to exclude the influence of patient demographics, preoperative medical status, and baseline renal function. Multivariate logistic regression analysis was used to evaluate for independent risk factors in the matched sample of 366 patients. The incidence of AKI was 28.6% and 5.9% of patients from the entire sample required renal replacement therapy. AKI was associated with a prolonged postoperative hospital stay and a higher one-month and one-year mortality both in the entire and matched sample set. Independent risk factors for AKI were a left ventricular ejection fraction <55%, preoperative hemoglobin level <10 g/dL, albumin <4.0 g/dL, diagnosis of dissection, operation time >7 hours, deep hypothermic circulatory arrest (DHCA) time >30 min, pRBC transfusion >1000 mL, and FFP transfusion >500 mL. Although the incidence of poor glucose control (blood glucose >180 mg/dL) was higher in patients with AKI in matched sample, it was not an independent risk factor.AKI was still associated with a poor clinical outcome in the matched sample. Potentially modifiable risk factors included preoperative anemia and hypoalbuminemia. Efforts to minimize operation time and DHCA time along with transfusion amount may protect patients undergoing aortic surgery against AKI.

Protective effects of tight glucose control during cardiopulmonary bypass on myocardium in adult nondiabetic patients undergoing valve replacement

BACKGROUND

In this study, we aimed to evaluate the protective effect of tight glucose control during cardiopulmonary bypass on myocardium in adult nondiabetic patients undergoing isolated aortic valve replacement in a prospective and randomized trial.

METHODS

Sixty-five adult nondiabetic patients undergoing selective isolated aortic valve replacement were enrolled and randomly assigned to an insulin group (patients received a continuous insulin infusion during surgery; n = 33) or a control group (patients were not administered insulin unless their blood glucose level exceeded 200 mg/dL; n = 32). Cardiac troponin I was assayed preoperatively, and then at 2, 6, 12, 24, and 48 hours after aortic cross-declamping. The pre-, intra-, and postoperative relevant data of all selected patients were analyzed.

RESULTS

Tight glucose control reduced postoperative peak release by 48% for cardiac troponin I compared with the control group (0.48 ± 0.12 vs 0.71 ± 0.17 ng/mL; P < 0.0001). Patients with continuous insulin infusion had lower peak inotropic score during the first postoperative 24 hours and peak level of blood glucose (5.8 ± 2.2 vs 8.2 ± 3.1 μg/kg/min; P < 0.0001; 131.9 ± 23.8 vs 191.1 ± 38.5 mg/dL; P < 0.001, respectively), shorter duration of mechanical ventilation and intensive care unit stay and hospital stay compared with the control group (11.6 ± 2.9 hours vs 14.8 ± 3.5 hours; P = 0.0002; 28.4 ± 7.2 hours vs 36.5 ± 7.8 hours; P < 0.0001; 9.4 ± 3.3 days vs 11.5 ± 4.2 days; P = 0.0283, respectively).

CONCLUSIONS

Tight glucose control during cardiopulmonary bypass might provide myocardial protection in adult nondiabetic patients undergoing isolated aortic valve replacement.

The role of perioperative sodium bicarbonate infusion affecting renal function after cardiothoracic surgery

Cardiac surgery associated acute kidney injury (CSA-AKI) is associated with poor outcomes including increased mortality, length of hospital stay (LOS) and cost. The incidence of acute kidney injury (AKI) is reported to be between 3 and 30% depending on the definition of AKI. We designed a multicenter randomized controlled trial to test our hypothesis that a perioperative infusion of sodium bicarbonate (SB) during cardiac surgery will attenuate the post-operative rise in creatinine indicating renal injury when compared to a perioperative infusion with normal saline. An interim analysis was performed after data was available on the first 120 participants. A similar number of patients in the two treatment groups developed AKI, defined as an increase in serum creatinine the first 48 h after surgery of 0.3 mg/dl or more. Specifically 14 patients (24%) who received sodium chloride (SC) and 17 patients (27%) who received SB were observed to develop AKI post-surgery, resulting in a relative risk of AKI of 1.1 (95% CI: 0.6–2.1, chi-square p-value = 0.68) for patients receiving SB compared to those who received SC. The data safety monitoring board for the trial recommended closing the study early as there was only a 12% probability that the null hypothesis would be rejected. We therefore concluded that a perioperative infusion of SB failed to attenuate the risk of CSA-AKI.

Effects of intensive glycemic control on outcomes of cardiac surgery

OBJECTIVES

To investigate the effects of postoperative intensive glycemic control on patient outcomes.

BACKGROUND

Ineffective perioperative glycemic control has been associated with high mortality and morbidity rates among cardiac surgery patients.

METHODS

212 cardiac surgery patients were allocated by a quasi-experimental design to: a) a control group (n = 107) with targeted blood glucose levels 161-200 mg/dl or b) a therapy group (n = 105) with blood glucose target 120-160 mg/dl. We compared the two groups on their mortality, length of stay, duration of intubation, incidence of severe hypoglycemia and frequency of postoperative infections.

RESULTS

The mean postoperative blood glucose levels were significantly lower for the therapy group compared with the control group (153.9 mg/dl vs. 173.9 md/dl, p < 0.001). The intensive glycemic control was strongly associated with decreased in-hospital mortality (7 deaths/105 patients for the control group vs. 1 death/105 patients for the therapy group; p = 0.033). We did not identify any statistically significant associations regarding the other patient outcomes.

CONCLUSIONS

This randomized quasi-experimental trial found lower in-hospital mortality with more intense blood glucose control. Effective postoperative glycemic control did not affect the other studied patient outcomes.

Peri-operative hyperglycemia is associated with delayed graft function in deceased donor renal transplantation

Increasing evidence indicates that recipient diabetes is a risk factor for delayed graft function (DGF) after renal transplant and that peri-operative hyperglycemia increases ischemia-reperfusion injury. To evaluate whether peri-operative hyperglycemia as measured in the post-anesthesia care unit (PACU) after transplant is a risk factor for DGF, we retrospectively reviewed 976 adult recipients of deceased donor renal transplants between January 1, 1997 and December 1, 2004. Logistic regression was used to evaluate risk factors for DGF. In our final multivariate model, recipient blood glucose level in the PACU (odds ratio [OR] 1.10 per 25 unit increase, 95% confidence interval (CI) 1.14-2.46, p = 0.03) was a statistically significant predictor of DGF along with donor age (OR 1.02, 95% CI 1.01-1.03, p < 0.01), cold ischemia time (OR 1.04, 95% CI 1.02-1.07, p < 0.01), recipient male gender (OR 1.68, 95% CI 1.14-2.68, p = 0.01), and a panel-reactive antibody >30% (OR 1.92, 95% CI 1.20-3.05, p = 0.01). We conclude that recipient blood glucose measured in the PACU is associated with DGF and begs the question of whether improved peri-operative glucose control will decrease the incidence of DGF.

Impact of intraoperative hyperglycaemia on renal dysfunction after off-pump coronary artery bypass

OBJECTIVES

Acute kidney injury (AKI) is one of the most frequently occurring complications after off-pump coronary artery bypass graft (OPCAB). Hyperglycaemia is a major, potentially modifiable risk factor of adverse outcome after cardiac surgery known to aggravate organ damage. The aim of this study was to address the association between intraoperative glucose concentration and postoperative AKI in patients who underwent OPCAB.

METHODS

The medical records of 880 consecutive patients were retrospectively reviewed. Patients were divided into three groups according to the time-weighted average of intraoperative glucose concentrations (<110, 110-150 and >150 mg/dl), and the incidence of AKI (increase of serum creatinine to >2.0 mg/dl and 2 × most recent preoperative value or a new requirement for dialysis) was compared. Multivariate logistic regression analysis was performed to identify independent risk factors for postoperative AKI.

RESULTS

The incidence of AKI was higher in patients with a glucose level >150 mg/dl than in patients with a glucose level = 110-150 mg/dl [8% (20 of 251) vs 3% (14 of 453), P = 0.004]. On multivariate analysis, glucose >150 mg/dl (odds ratio [OR], 2.78; 95% confidence interval [CI], 1.12-6.86, P = 0.027), coefficient of variation of glucose (OR, 1.04; 95% CI, 1.01-1.07, P = 0.027) and preoperative serum creatinine >1.4 mg/dl (OR, 8.81; 95% CI, 3.90-19.9, P < 0.001) were identified as independent risk factors for postoperative AKI.

CONCLUSIONS

Intraoperative glucose concentration >150 mg/dl and increased variability of glucose were independently associated with AKI after OPCAB. Tight intraoperative glycaemic control (<110 mg/dl) does not seem to provide additional benefit in terms of AKI.

Update on clinical trials for the prevention of acute kidney injury in patients undergoing cardiac surgery

BACKGROUND

Effective therapeutic agents for the prevention and treatment of acute kidney injury (AKI) after cardiac surgery remain elusive despite the tremendous advances in surgical techniques, technology, and understanding of disease processes. Recent developments and their effect on the incidence of AKI after cardiac surgery are discussed.

DATA SOURCES

Published clinical trials in PubMed, strength of evidence assessed by the guidelines of the American Family Physicians.

CONCLUSIONS

The definition of AKI has changed, and the focus of interventions has shifted from treatment to prevention to recovery from AKI. Antioxidants and biological agents have been added to classic armaments of hydration and diuretics in addition to tighter metabolic control to prevent AKI. Although the treatment options remain unsatisfactory, a lot of progress nevertheless continues to be made in the prevention and treatment of AKI.

Implementation of an intraoperative glycemic control protocol for cardiac surgery in a high-acuity academic medical center: an observational study

STUDY OBJECTIVE

To examine the effect on morbidity and mortality of an established intraoperative insulin protocol in cardiac surgical patients.

DESIGN

Retrospective observational study.

SETTING

Single-center, 782 bed, metropolitan academic hospital.

PATIENTS

1,616 adult patients undergoing cardiac surgical procedures with cardiopulmonary bypass (CPB).

INTERVENTIONS

An intraoperative, intravenous (IV) insulin protocol designed to maintain blood glucose values less than 150 mg/dL was implemented.

MEASUREMENTS

Blood glucose was evaluated on entry to the operating room, every 30 minutes during CPB, and at least once after discontinuation of CPB. Blood glucose values were followed postoperatively, as dictated by institutional policy.

MAIN RESULTS

Intraoperative predictors of 30-day mortality using multivariate logistic regression included hyperglycemia on initiation of CPB (OR 1.0, P = 0.05). The strongest predictor of 30-day mortality was the development of postoperative renal failure requiring hemodialysis (OR 3.26, P = 0.001).

CONCLUSIONS

Implementation of an intraoperative IV insulin protocol, while associated with improved glycemic control, was not associated with improved outcomes. While improved glycemic control on initiating CPB was associated with decreased 30-day mortality, the effect was small. Implementation of our insulin protocol was highly associated with decreased renal failure postoperatively. Further prospective studies are warranted to better establish causality.

Novel biomarkers for cardiac surgery-associated acute kidney injury: a skeptical assessment of their role

Cardiac surgery-associated acute kidney injury (AKI) is common and is associated with a high mortality rate. Traditional biomarkers of AKI (creatinine and urea) increase slowly in response to renal injury, are insensitive to mild degrees of AKI, and are influenced by nonrenal factors. There is considerable interest in novel biomarkers of AKI such as neutrophil gelatinase-associated lipocalin that increase rapidly after renal injury, detect mild degrees of AKI, and are less subject to nonrenal factors. It has been postulated that the early diagnosis of cardiac surgery-associated AKI using novel biomarkers will result in improved outcomes. However, there is little evidence that interventions started early in the course of evolving AKI enhance renal recovery. Until effective therapies are developed that significantly improve the outcome from AKI, there is little benefit from early diagnosis using novel biomarkers.

Predictors of Prolonged Stay in the Intensive Care Unit following Cardiac Surgery

The prediction of intensive care unit length of stay (ICU-LOS) could contribute to more efficient ICU resources' allocation and better planning of care among cardiac surgery patients. The aim of this study was to identify the preoperative and intraoperative predictors for prolonged cardiac surgery ICU-LOS. An observational cohort study was conducted among 150 consecutive patients, who were admitted to the cardiac surgery ICU of a tertiary hospital of Athens, Greece from September 2010 to January 2011. Multivariate regression analysis revealed that patients with increased creatinine levels preoperatively (odds ratio (OR) 3.0, P = 0.049), history of atrial fibrillation (AF) (OR 6.3, P = 0.012) and high EuroSCORE values (OR 2.6, P = 0.017) had a significant greater probability to stay in the ICU for more than 2 days. In addition, intraoperative hyperglycemia (OR 3.0, P = 0.004) was strongly associated with longer ICU-LOS. In conclusion, the high perioperative risk, the history of AF and renal dysfunction, and the intraoperative hyperglycemia are significant predictors of prolonged ICU stay. The early identification of patients at risk could allow the efficient ICU resources' allocation and the reduction of healthcare costs. This would contribute to nursing care planning depending on the availability of healthcare personnel and ICU bed capacity.

Intensive insulin therapy in the ICU--reconciling the evidence

Hyperglycaemia during critical illness unequivocally correlates with adverse outcome. Three proof-of-concept randomized controlled trials have shown that preventing hyperglycaemia in patients admitted to the intensive care unit (ICU) reduces organ failure and mortality. A subsequent multicentre, randomized controlled trial found that targeting normoglycaemia in this patient population does not affect organ function differently than targeting an intermediate glucose level (7.8-10.0 mmol/l). However, an intermediate glucose target evoked less hypoglycaemia and, for currently unexplained reasons, also fewer deaths than a normoglycaemic target. Moreover, tolerating a caloric deficit, rather than providing nutrients parenterally, accelerated recovery from critical illness in the presence of normoglycaemia. Whether macronutrient restriction renders moderate hyperglycaemia less harmful remains to be investigated. Hence, if adequate monitoring tools and expertise are available, normoglycaemia remains the only proven effective target for insulin treatment of hyperglycaemia in ICU patients. However, if these conditions are not fulfilled in clinical practice, is an intermediate target range preferable? In the absence of hard evidence, common sense supports such an intermediate blood glucose target.

The correlation between peri-operative hyperglycemia and mortality in cardiac surgery patients: a systematic review

BACKGROUND

Hyperglycemia occurs frequently in patients undergoing cardiac surgery. It has been identified as a risk factor for increased peri-operative morbidity and mortality.

AIM

To review the evidence of the correlation of peri-operative hyperglycemia with mortality in cardiac surgery patients and to discuss the main results in order to provide evidence-based knowledge for the appropriate glycemic control.

METHODS

We searched the electronic databases MEDLINE, CINAHL and EMBASE in June 2010. The material of our study was articles published between 1 January 1990 and 31 May 2010, which investigated the correlation between peri-operative hyperglycemia and in-hospital and/or 30-day cardiac surgery mortality.

RESULTS

Out of the 16 reviewed articles in our study, 12 (75%) significantly associated hyperglycemia and inadequate blood glucose control with increased mortality. In addition, four of the reviewed articles were controlled randomized trials and among them only one demonstrated strong correlation between poor glycemic control and mortality. No study was multi-centre and the reviewed articles were characterized by different definitions of peri-operative hyperglycemia, different intensity and duration of the applied therapy and heterogeneity of the population.

CONCLUSION

It is clear that peri-operative hyperglycemia is harmful for cardiac surgery patients. The significant shortage of randomized controlled trials, the absence of multicentre studies, the different definitions of peri-operative hyperglycemia, the different intensity and duration of the applied insulin therapy protocol and the heterogeneity of the studied population (diabetics and non-diabetics) are significant limitations, which could explain the inconsistent findings of the literature. These limitations indicate the need for further research.

Glycemic control: how tight in the intensive care unit?

Determining the optimal level of glycemic control in critical illness has proven difficult since the original Leuven study conclusions were published in 2001. Conflicting evidence, scientific methodologies, hospital cultures, and a-priori biases have challenged many clinical practice patterns. Specifically, the prioritization of patient safety has resulted in many practitioners changing from a glycemic control target of 80-110 mg/dL to a more liberal target of 140-180 mg/dL. However, a detailed examination of the evidence can provide a more population-specific glycemic control strategy. This position paper presents an approach for cardiac surgery patients in the intensive care unit (ICU) consistent with extant evidence and real-life variables. We argue that in the cardiac surgery ICU, glycemic targets may be as low as 80-110 mg/dL when formal intensive insulin therapy and nutrition support protocols are used with low rates of hypoglycemia, patient safety mechanisms, properly trained staff, and a supportive hospital administration all in force. Cardiac surgery ICUs that already follow this model may continue with 80-110 mg/dL blood glucose targets, whereas others may advance their blood glucose targets in a stepwise fashion: from 140 to 180 mg/dL to 110-140 mg/dL to 80-110 mg/dL, on the basis of their performance.

Carbohydrate provision in the era of tight glucose control

Glycemic control in the critically ill patient has remained a controversial issue over the last decade. Several large trials, with widely varying results, have generated significant interest in defining the optimal target for blood-glucose control necessary for improving care while minimizing morbidity. Nutritional support has evolved into an additional area of critical care where appropriate practices have been associated with improved patient outcomes. Carbohydrate provision can impact blood-glucose levels, and the relationship between nutrition and glucose levels has become more complex in the era of improved glycemic control. This review discusses the controversy surrounding intensive-insulin therapy in the intensive care unit and explores the relationship with nutritional support, both in the enteral and parenteral form. Achieving realistic goals in both carbohydrate provision and glycemic control may improve patient outcome, and are not mutually exclusive practices.

Does tight glucose control prevent myocardial injury and inflammation?

Hyperglycemia has been postulated to be cardiotoxic. We addressed the hypothesis that uncontrolled blood glucose induces myocardial damage in diabetic patients undergoing isolated coronary artery bypass graft surgery receiving continuous insulin infusion in the immediate postoperative period. Our primary aim was to assess the degree of tight glycemic control for each patient and to link the degree of glycemic control to intermediate outcome of myocardial damage. We prospectively enrolled 199 consecutive patients with diabetes undergoing isolated coronary artery bypass graft surgery from October 2003 through August 2005. Preoperative hemoglobin A1c and glucose measures were collected from the surgical admission. We measured biomarkers of myocardial damage (cardiac troponin I) and metabolic dysfunction (blood glucose and hemoglobin A1c) to identify a difference among patients under tight (90-100% of glucose measures < or = 150 mg/dL) or loose (<90%) glycemic control. All patients received continuous insulin infusion in the immediate postoperative period. We discovered 45.6% of the patients were in tight control. We found tight glycemic control resulted in no significant difference in troponin I release. Mean cardiac troponin I for tight and loose control was 4.9 and 8.5 (ng/mL), p value .3.We discovered patients varied with their degree of control, even with established protocols to maintain glucose levels within the normal range. We were unable to verify tight glycemic control compared to loose control was significantly associated with decreased cardiac troponin I release. Future studies are needed to evaluate the cardiotoxic mechanisms of hyperglycemia postulated in this study.

Postoperative glycemic control in cardiac surgery patients

Glycemic control in postoperative cardiac patients is necessary to improve outcomes in wound infection and overall mortality. In recent years, clinical trials evaluating blood glucose control in critically ill patients advocated for intense blood glucose management and found a significant reduction in morbidity and mortality. Some organizations published recommendations regarding blood glucose management in critically ill patients reflecting this information. However, recent clinical trials evaluating blood glucose target ranges in critically ill patients have found conflicting results, which has prompted reevaluation of current goals and guidelines, allowing for less stringent blood glucose target ranges. With the inconsistency of clinical trials evaluating a target blood glucose range for critically ill patients, specifically postoperative cardiac surgery patients, the target blood glucose range is still not clearly defined. Additional comparisons of specific glucose ranges would allow for a clearer definition of recommended blood glucose goals to target in postoperative cardiac patients.

Preventing acute kidney injury after noncardiac surgery

PURPOSE OF REVIEW

In surgical patients, outcome is strictly dependent on the occurrence of postoperative complications, and a postoperative failing kidney has a significant independent effect on outcome. Acute kidney injury (AKI) occurs in 1% of noncardiac surgical patients and is commonly associated with more serious complications. It is important to prevent AKI wherever possible.

RECENT FINDINGS

The mainstay of postoperative AKI prevention is perioperative maintenance of blood volume with adequate cardiac output by hemodynamic monitoring and fluids/inotropes infusion. There is a growing interest for pharmacological and metabolic interventions. Most interventions, however, have been predominantly evaluated in cardiac surgery and no definite conclusion can be translated in other settings. Tight control of glycemia is still matter of debate and a role, if any, may be limited to cardiac surgical patients.

SUMMARY

Adopting adequate nephroprotective strategies is favored by knowing the moment of the actual insult to the kidney. Nevertheless, in the literature too many areas of uncertainty still exist due to the lack of renal risk stratification, of adequately powered studies, of uniform AKI definition, and of appropriate sample composition. The only recommendation for renal protection still consists in maintaining an optimal blood volume and an adequate cardiac output.

Effect of remote ischemic preconditioning on renal dysfunction after complex valvular heart surgery: a randomized controlled trial

OBJECTIVE

Acute kidney injury after cardiac surgery with cardiopulmonary bypass is closely related to systemic inflammatory reactions and oxidative stresses. Remote ischemic preconditioning is a systemic protective strategy whereby brief limb ischemia confers systemic protection against prolonged ischemia and inflammatory reactions in distant organs. This study investigated whether remote ischemic preconditioning provides systemic protective effect on kidneys that are not directly exposed to ischemia-reperfusion injury during complex valvular heart surgery.

METHODS

Seventy-six adult patients undergoing complex valvular heart surgery were randomly assigned to either remote ischemic preconditioning group (n = 38) or control group (n = 38). Remote ischemic preconditioning consisted of 3 10-minute cycles of lower limb ischemia and reperfusion with an automated cuff inflator. Primary end points were comparisons of biomarkers of renal injury including serum creatinine, cystatin C and neutrophil gelatinase-associated lipocalin, and incidence of acute kidney injury. Secondary end points were comparisons of myocardial enzyme release and pulmonary parameters.

RESULTS

There were no significant differences in serum levels of biomarkers of renal injury between groups throughout the study period. The incidence of acute kidney injury did not differ between groups. Creatine kinase isoenzyme MB at 24 hours after surgery was lower, and intensive care unit stay was shorter in the remote ischemic preconditioning group than in the control group.

CONCLUSIONS

In patients undergoing complex valvular heart surgery, remote ischemic preconditioning did not reduce degree of renal injury or incidence of acute kidney injury whereas it did reduce myocardial injury and intensive care unit stay.

Effects of moderate intensity glycemic control after cardiac surgery

BACKGROUND

The impact of intensive insulin therapy on the clinical outcomes of hospitalized patients is highly controversial. We used a protocol based on dynamic insulin administration targeted to achieve moderately tight glycemic control and tested its impact on clinical outcomes after cardiac surgery.

METHODS

Patients with diabetes mellitus or random blood glucose greater than 150 mg/dL were treated in the intensive care unit with intravenous insulin, followed by a multi-injection protocol consisting of 4 glargine/aspart insulin injections in the ward, with a glycemic target of 110 to 150 mg/dL. The study cohort (n = 410) consisted of consecutive patients undergoing cardiothoracic surgery. Control patients (n = 207) were admitted during the first 8 months and treated according to standard of care. The intervention group of patients (n = 203) were operated on during the following 8 months. The main outcome measures were glycemic control and the rate of postsurgery infections.

RESULTS

During the intervention, mean blood glucose ± SD was 151 ± 19 mg/dL and 157 ± 32 mg/dL in the intensive care unit and ward, respectively, versus 166 ± 27 mg/dL and 184 ± 46 mg/dL during the control period (p < 0.0001). The incidence of hypoglycemia (blood glucose less than 60 mg/dL) was low and similar in the two groups (2.5% control versus 3% intervention). Intensive insulin treatment decreased the risk for infection from 11% to 5% (56% risk reduction, p = 0.018), mainly by reducing the incidence of graft harvest site infection (6.9% versus 2.5%, p = 0.034). The incidence of atrial fibrillation after coronary artery bypass graft surgery decreased from 30% to 18% (39% risk reduction; p = 0.042).

CONCLUSIONS

Moderate-intensity dynamic blood glucose control after cardiac surgery is effective and safe, and is associated with improved clinical outcomes.

Intensive insulin therapy to maintain normoglycemia after cardiac surgery

Drugs used in the perioperative period could have an effect on survival as recently pointed out by an international consensus conference on the reduction in mortality in cardiac anesthesia and intensive care. Insulin infusion to achieve a strict glycemic control is the best example of how an ancillary (i.e. non-surgical) drug/technique/strategy might influence survival rates in patients undergoing cardiac surgery. The author of this "expert opinion" presents her insights into the use of insulin in this setting and suggest that based on available evidence based medicine, insulin infusion, titrated to "normoglycemia" is a complex intervention, that not only requires the simple administration of a "drug", the hormone insulin, but also needs tools and skills to accurately measure and control blood glucose to achieve normoglycemia while avoiding hypoglycemia and large glucose fluctuations.