Hyperinsulinemic Normoglycemia Does Not Meaningfully Improve Myocardial Performance during Cardiac Surgery: A Randomized Trial

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.

Perioperative glycaemic control for people with diabetes undergoing surgery

BACKGROUND

People with diabetes mellitus are at increased risk of postoperative complications. Data from randomised clinical trials and meta-analyses point to a potential benefit of intensive glycaemic control, targeting near-normal blood glucose, in people with hyperglycaemia (with and without diabetes mellitus) being submitted for surgical procedures. However, there is limited evidence concerning this question in people with diabetes mellitus undergoing surgery.

OBJECTIVES

To assess the effects of perioperative glycaemic control for people with diabetes undergoing surgery.

SEARCH METHODS

For this update, we searched the databases CENTRAL, MEDLINE, LILACS, WHO ICTRP and ClinicalTrials.gov. The date of last search for all databases was 25 July 2022. We applied no language restrictions.

SELECTION CRITERIA

We included randomised controlled clinical trials (RCTs) that prespecified different targets of perioperative glycaemic control for participants with diabetes (intensive versus conventional or standard care).

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed the risk of bias. Our primary outcomes were all-cause mortality, hypoglycaemic events and infectious complications. Secondary outcomes were cardiovascular events, renal failure, length of hospital and intensive care unit (ICU) stay, health-related quality of life, socioeconomic effects, weight gain and mean blood glucose during the intervention. We summarised studies using meta-analysis with a random-effects model and calculated the risk ratio (RR) for dichotomous outcomes and the mean difference (MD) for continuous outcomes, using a 95% confidence interval (CI), or summarised outcomes with descriptive methods. We used the GRADE approach to evaluate the certainty of the evidence (CoE).

MAIN RESULTS

A total of eight additional studies were added to the 12 included studies in the previous review leading to 20 RCTs included in this update. A total of 2670 participants were randomised, of which 1320 were allocated to the intensive treatment group and 1350 to the comparison group. The duration of the intervention varied from during surgery to five days postoperative. No included trial had an overall low risk of bias. Intensive glycaemic control resulted in little or no difference in all-cause mortality compared to conventional glycaemic control (130/1263 (10.3%) and 117/1288 (9.1%) events, RR 1.08, 95% CI 0.88 to 1.33; I2 = 0%; 2551 participants, 18 studies; high CoE). Hypoglycaemic events, both severe and non-severe, were mainly experienced in the intensive glycaemic control group. Intensive glycaemic control may slightly increase hypoglycaemic events compared to conventional glycaemic control (141/1184 (11.9%) and 41/1226 (3.3%) events, RR 3.36, 95% CI 1.69 to 6.67; I2 = 64%; 2410 participants, 17 studies; low CoE), as well as those considered severe events (37/927 (4.0%) and 6/969 (0.6%), RR 4.73, 95% CI 2.12 to 10.55; I2 = 0%; 1896 participants, 11 studies; low CoE). Intensive glycaemic control, compared to conventional glycaemic control, may result in little to no difference in the rate of infectious complications (160/1228 (13.0%) versus 224/1225 (18.2%) events, RR 0.75, 95% CI 0.55 to 1.04; P = 0.09; I2 = 55%; 2453 participants, 18 studies; low CoE). Analysis of the predefined secondary outcomes revealed that intensive glycaemic control may result in a decrease in cardiovascular events compared to conventional glycaemic control (107/955 (11.2%) versus 125/978 (12.7%) events, RR 0.73, 95% CI 0.55 to 0.97; P = 0.03; I2 = 44%; 1454 participants, 12 studies; low CoE). Further, intensive glycaemic control resulted in little or no difference in renal failure events compared to conventional glycaemic control (137/1029 (13.3%) and 158/1057 (14.9%), RR 0.92, 95% CI 0.69 to 1.22; P = 0.56; I2 = 38%; 2086 participants, 14 studies; low CoE). We found little to no difference between intensive glycaemic control and conventional glycaemic control in length of ICU stay (MD -0.10 days, 95% CI -0.57 to 0.38; P = 0.69; I2 = 69%; 1687 participants, 11 studies; low CoE), and length of hospital stay (MD -0.79 days, 95% CI -1.79 to 0.21; P = 0.12; I2 = 77%; 1520 participants, 12 studies; very low CoE). Due to the differences within included studies, we did not pool data for the reduction of mean blood glucose. Intensive glycaemic control resulted in a mean lowering of blood glucose, ranging from 13.42 mg/dL to 91.30 mg/dL. One trial assessed health-related quality of life in 12/37 participants in the intensive glycaemic control group, and 13/44 participants in the conventional glycaemic control group; no important difference was shown in the measured physical health composite score of the short-form 12-item health survey (SF-12). One substudy reported a cost analysis of the population of an included study showing a higher total hospital cost in the conventional glycaemic control group, USD 42,052 (32,858 to 56,421) compared to the intensive glycaemic control group, USD 40,884 (31.216 to 49,992). It is important to point out that there is relevant heterogeneity between studies for several outcomes. We identified two ongoing trials. The results of these studies could add new information in future updates on this topic.

AUTHORS' CONCLUSIONS

High-certainty evidence indicates that perioperative intensive glycaemic control in people with diabetes undergoing surgery does not reduce all-cause mortality compared to conventional glycaemic control. There is low-certainty evidence that intensive glycaemic control may reduce the risk of cardiovascular events, but cause little to no difference to the risk of infectious complications after the intervention, while it may increase the risk of hypoglycaemia. There are no clear differences between the groups for the other outcomes. There are uncertainties among the intensive and conventional groups regarding the optimal glycaemic algorithm and target blood glucose concentrations. In addition, we found poor data on health-related quality of life, socio-economic effects and weight gain. It is also relevant to underline the heterogeneity among studies regarding clinical outcomes and methodological approaches. More studies are needed that consider these factors and provide a higher quality of evidence, especially for outcomes such as hypoglycaemia and infectious complications.

Diagnostic Accuracy of Global Longitudinal Strain for Detecting Exercise Intolerance in Patients with Ischemic Heart Disease

Objective: Global longitudinal strain (GLS) is a sensitive and reproducible predictive factor in patients with ischemic heart disease (IHD), although its correlation with exercise tolerance is unknown. We aimed to identify the correlation between global longitudinal strain (GLS) and cardiopulmonary exercise testing (CPX) parameters and assess the prognostic implications and accuracy of GLS in predicting exercise intolerance in populations with ischemic heart disease (IHD) using CPET criteria. Methods: Prospectively, 108 patients with IHD underwent CPX and 2D speckle-tracking echocardiography. Correlation between GLS and multiple CPX variables was assessed using Spearman’s correlation analysis and univariate regression analysis. A receiver operating characteristic (ROC) curve analysis was performed on GLS to detect exercise intolerance. Results: GLS was correlated with peak oxygen uptake (peak VO2; r = −0.438, p = 0.000), %PPeak VO2 (−0.369, p = 0.000), peak metabolic equivalents (METs@peak; r = −0.438, p < 0.01), and the minute ventilation−carbon dioxide production (VE/VCO2) slope (r = 0.257, p < 0.01). Weak-to-moderate correlations were also identified for the respiratory exchange rate at the anaerobic threshold (RER@AT), end-tidal carbon dioxide at the anaerobic threshold (PETCO2@AT), oxygen consumption at the anaerobic threshold (VO2@AT), carbon dioxide production at the anaerobic threshold (VCO2@AT), and metabolic equivalents at the anaerobic threshold (METs@AT; p < 0.01). On multivariate analysis, the results showed that age, the BMI, and GLS are independent predictors for reduced exercise capacity in patients with IHD (p < 0.01). The area under the ROC curve value of GLS for identifying patients with a peak VO2 of <14 mL/kg/min was 0.73 (p = 0.000). Conclusion: As a sensitive echocardiographic assessment of patients with ischemic heart disease, global longitudinal strain is an independent predictor of reduced exercise capacity and has a sensitivity of 74.2% and a specificity of 66.7% to detect exercise intolerance.

Cardioprotective Effects of Glucose-Insulin-Potassium Infusion in Patients Undergoing Cardiac Surgery: A Systematic Review and Meta-Analysis

The infusion of glucose-insulin-potassium (GIK) has yielded conflicting results in terms of cardioprotective effects. We conducted a meta-analysis to examine the impact of perioperative GIK infusion in early outcome after cardiac surgery. Randomized controlled trials (RCTs) were eligible if they examined the efficacy of GIK infusion in adults undergoing cardiac surgery. The main study endpoint was postoperative myocardial infarction (MI) and secondary outcomes were hemodynamics, any complications and hospital resources utilization. Subgroup analyses explored the impact of the type of surgery, GIK composition and timing of administration. Odds ratio (OR) or mean difference (MD) with 95% confidence interval (CI) were calculated with a random-effects model. Fifty-three studies (n=6129) met the inclusion criteria. Perioperative GIK infusion was effective in reducing MI (k=32 OR 0.66[0.48, 0.89] P=0.0069), acute kidney injury (k=7 OR 0.57[0.4, 0.82] P=0.0023) and hospital length of stay (k=19 MD -0.89[-1.63, -0.16] days P=0.0175). Postoperatively, the GIK-treated group presented higher cardiac index (k=14 MD 0.43[0.29, 0.57] L/min P<0.0001) and lesser hyperglycemia (k=20 MD -30[-47, -13] mg/dL P=0.0005) than in the usual care group. The GIK-associated protection for MI was effective when insulin infusion rate exceeded 2 mUI/kg/min and after coronary artery bypass surgery. Certainty of evidence was low given imprecision of the effect estimate, heterogeneity in outcome definition and risk of bias. Perioperative GIK infusion is associated with improved early outcome and reduced hospital resource utilization after cardiac surgery. Supporting evidence is heterogenous and further research is needed to standardize the optimal timing and composition of GIK solutions.

Post-cardiopulmonary bypass longitudinal strain provides higher prognostic ability than baseline strain or change in strain

CONTEXT

Global longitudinal strain (GLS) measured by speckle-tracking echocardiography demonstrates excellent prognostic ability in predicting major adverse cardiac events after cardiac surgery. However, the optimal timing of intraoperative GLS measurement that provides the best prognostic value is unclear.

AIM

Our goal was to evaluate whether GLS measured prior to cardiopulmonary bypass (pre-CPB GLS), following CPB (post-CPB GLS), or change in GLS provides the strongest association with postoperative complications.

SETTING AND DESIGN

Post hoc analysis of prospectively collected data from a clinical trial (NCT01187329). 72 patients with aortic stenosis undergoing elective AVR ± coronary artery bypass grafting between January 2011 and August 2013.

MATERIAL AND METHODS

Myocardial deformation analysis from standardized transesophageal echocardiographic examinations were performed after anesthetic induction and chest closure. We evaluated the association between pre-CPB GLS, post-CPB GLS, and change in GLS (percent change from pre-CPB baseline) with postoperative atrial fibrillation and hospitalization >7 days. The association of post-CPB GLS with duration of mechanical ventilation, N-terminal pro-BNP (NT-proBNP) and troponin T were also assessed.

STATISTICAL ANALYSIS

Multivariable logistic regression.

RESULTS

Risk-adjusted odds (OR[97.5%CI] of prolonged hospitalization increased an estimated 27% (1.27[1.01 to 1.59];P_adj =0.035) per 1% decrease in absolute post-CPB GLS. Mean[98.3%CI] NT-proBNP increased 98.4[20 to 177]pg/mL; P_adj =0.008), per 1% decrease in post-CPB GLS. Pre-CPB GLS or change in GLS were not associated with any outcomes.

CONCLUSIONS

Post-CPB GLS provides the best prognostic value in predicting postoperative outcomes. Measuring post-CPB GLS may improve risk stratification and assist in future study design and patient outcome research.

Left Ventricular Twist Mechanics Before and After Aortic Valve Replacement: A Feasibility Study and Exploratory Analysis

Introduction. We examined whether intraoperative assessment of left ventricular (LV) twist mechanics is feasible with transesophageal echocardiography (TEE). We then explored whether twist mechanics were altered by hemodynamic conditions or patient comorbidities. Methods. In this sub-analysis of clinical trial data, transgastric short-axis echocardiographic images of the LV base and apex were collected in patients having aortic valve replacement (AVR) at baseline and end of surgery. Transvalvular gradients and LV systolic and diastolic function were assessed using two-dimensional (2D) and Doppler echocardiography. 2D speckle-tracking echocardiography was used for off-line analysis of LV twist, twisting rate, and untwisting rate. We examined the intraoperative change in twist mechanics before and after AVR. LV twist mechanics were also explored by diabetic status, need for coronary artery bypass grafting (CABG), and use of epinephrine/norepinephrine. Results. Of 40 patients, 16 patients had acceptable TEE images for off-line LV twist analysis. Baseline median [Q1, Q3] LV twist was 12 [7, 16]°, twisting rate was 72 [41, 97]°/sec, and untwisting rate was -91 [-154, -56]°/s. Median [Q1, Q3] change in LV twist at end of surgery was -2 [-5, 3]°, twisting rate was 7 [-33, 31]°/s, and untwisting rate was 0 [-11, 43]°/s. No difference was noted between diabetic and non-diabetic patients or AVR and AVR-CABG patients. Conclusion. LV twist was augmented in patients with aortic stenosis, though twist indices were not affected by reduced afterload, diabetes, or coronary artery disease. Intraoperative assessment of twist mechanics may provide unique information on LV systolic and diastolic function, though fewer than 50% of TEE examinations successfully assessed twist. Clinical Trial Registry. This work is a sub-analysis of a clinical trial, registered on ClinicalTrials.gov on August 19, 2010 (NCT01187329), Andra Duncan, Principal Investigator.

The dual role of the hexosamine biosynthetic pathway in cardiac physiology and pathophysiology

The heart is a highly metabolic organ with extensive energy demands and hence relies on numerous fuel substrates including fatty acids and glucose. However, oxidative stress is a natural by-product of metabolism that, in excess, can contribute towards DNA damage and poly-ADP-ribose polymerase activation. This activation inhibits key glycolytic enzymes, subsequently shunting glycolytic intermediates into non-oxidative glucose pathways such as the hexosamine biosynthetic pathway (HBP). In this review we provide evidence supporting the dual role of the HBP, i.e. playing a unique role in cardiac physiology and pathophysiology where acute upregulation confers cardioprotection while chronic activation contributes to the onset and progression of cardio-metabolic diseases such as diabetes, hypertrophy, ischemic heart disease, and heart failure. Thus although the HBP has emerged as a novel therapeutic target for such conditions, proposed interventions need to be applied in a context- and pathology-specific manner to avoid any potential drawbacks of relatively low cardiac HBP activity.

Glucose-insulin-potassium improves left ventricular performances after aortic valve replacement: a secondary analysis of a randomized controlled trial

Background

Patients with left ventricular (LV) hypertrophy may suffer ischemia-reperfusion injuries at the time of cardiac surgery with impairment in left ventricular function. Using transesophageal echocardiography (TEE), we evaluated the impact of glucose-insulin potassium (GIK) on LV performances in patients undergoing valve replacement for aortic stenosis.

Methods

In this secondary analysis of a double-blind randomized trial, moderate-to-high risk patients were assigned to receive GIK (20 IU insulin with 10 mEq KCL in 50 ml glucose 40%) or saline over 60 min upon anesthetic induction. The primary outcomes were the early changes in 2-and 3-dimensional left ventricular ejection fraction (2D and 3D-LVEF), peak global longitudinal strain (PGLS) and transmitral flow propagation velocity (Vp).

Results

At the end of GIK infusion, LV-FAC and 2D- and 3D-LVEF were unchanged whereas Vp (mean difference [MD + 7.9%, 95% confidence interval [CI] 3.2 to 12.5%; P <  0.001) increased compared with baseline values. After Placebo infusion, there was a decrease in LV-FAC (MD -2.9%, 95%CI − 4.8 to − 1.0%), 2D-LVEF (MD -2.0%, 95%CI − 2.8 to − 1.3%, 3D-LVEF (MD -3.0%, 95%CI − 4.0 to − 2.0%) and Vp (MD − 4.5 cm/s, 95%CI − 5.6 to − 3.3 cm/s).

After cardiopulmonary bypass, GIK pretreatment was associated with preserved 2D and 3D-LVEF (+ 0.4%, 95% 95%CI − 0.8 to 1.7% and + 0.4%, 95%CI − 1.3 to 2.0%), and PGLS (− 0.9, 95%CI − 1.6 to − 0.2) as well as higher Vp (+ 5.1 cm/s, 95%CI 2.9 to 7.3), compared with baseline. In contrast, in the Placebo group, 2D-LVEF (− 2.2%, 95%CI − 3.4 to − 1.0), 3D-LVEF (− 6.0%, 95%CI − 7.8 to − 4.2), and Vp (− 7.6 cm/s, 95%CI − 9.4 to − 5.9), all decreased after bypass.

Conclusions

Administration of GIK before aortic cross-clamping resulted in better preservation of systolic and diastolic ventricular function in patients with LV hypertrophy undergoing aortic valve replacement.

Trial registration

ClinicalTrials.gov: NCT00788242, registered on November 10, 2008.

Hyperinsulinemic Normoglycemia during Cardiac Surgery Reduces a Composite of 30-day Mortality and Serious In-hospital Complications: A Randomized Clinical Trial

BACKGROUND

Hyperinsulinemic normoglycemia augments myocardial glucose uptake and utilization. We tested the hypothesis that hyperinsulinemic normoglycemia reduces 30-day mortality and morbidity after cardiac surgery.

METHODS

This dual-center, parallel-group, superiority trial randomized cardiac surgical patients between August 2007 and March 2015 at the Cleveland Clinic, Cleveland, Ohio, and Royal Victoria Hospital, Montreal, Canada, to intraoperative glycemic management with (1) hyperinsulinemic normoglycemia, a fixed high-dose insulin and concomitant variable glucose infusion titrated to glucose concentrations of 80 to 110 mg · dl; or (2) standard glycemic management, low-dose insulin infusion targeting glucose greater than 150 mg · dl. The primary outcome was a composite of 30-day mortality, mechanical circulatory support, infection, renal or neurologic morbidity. Interim analyses were planned at each 12.5% enrollment of a maximum 2,790 patients.

RESULTS

At the third interim analysis (n = 1,439; hyperinsulinemic normoglycemia, 709, standard glycemic management, 730; 52% of planned maximum), the efficacy boundary was crossed and study stopped per protocol. Time-weighted average glucose concentration (means ± SDs) with hyperinsulinemic normoglycemia was 108 ± 20 versus 150 ± 33 mg · dl with standard glycemic management, P < 0.001. At least one component of the composite outcome occurred in 49 (6.9%) patients receiving hyperinsulinemic normoglycemia versus 82 (11.2%) receiving standard glucose management (P < efficacy boundary 0.0085); estimated relative risk (95% interim-adjusted CI) 0.62 (0.39 to 0.97), P = 0.0043. There was a treatment-by-site interaction (P = 0.063); relative risk for the composite outcome was 0.49 (0.26 to 0.91, P = 0.0007, n = 921) at Royal Victoria Hospital, but 0.96 (0.41 to 2.24, P = 0.89, n = 518) at the Cleveland Clinic. Severe hypoglycemia (less than 40 mg · dl) occurred in 6 (0.9%) patients.

CONCLUSIONS

Intraoperative hyperinsulinemic normoglycemia reduced mortality and morbidity after cardiac surgery. Providing exogenous glucose while targeting normoglycemia may be preferable to simply normalizing glucose concentrations.

Reduced Left Ventricular Global Longitudinal Strain Predicts Prolonged Hospitalization: A Cohort Analysis of Patients Having Aortic Valve Replacement Surgery

BACKGROUND

Left ventricular ejection fraction (LVEF) is often preserved in patients with aortic stenosis and thus cannot distinguish between normal myocardial contractile function and subclinical dysfunction. Global longitudinal strain and strain rate (SR), which measure myocardial deformation, are robust indicators of myocardial function and can detect subtle myocardial dysfunction that is not apparent with conventional echocardiographic measures. Strain and SR may better predict postoperative outcomes than LVEF. The primary aim of our investigation was to assess the association between global longitudinal strain and serious postoperative outcomes in patients with aortic stenosis having aortic valve replacement. Secondarily, we also assessed the associations between global longitudinal SR and LVEF and the outcomes.

METHODS

In this post hoc analysis of data from a randomized clinical trial (NCT01187329), we examined the association between measures of myocardial function and the following outcomes: (1) need for postoperative inotropic/vasopressor support; (2) prolonged hospitalization (>7 days); and (3) postoperative atrial fibrillation. Standardized transesophageal echocardiographic examinations were performed after anesthetic induction. Myocardial deformation was measured using speckle-tracking echocardiography. Multivariable logistic regression was used to assess associations between measures of myocardial function and outcomes, adjusted for potential confounding factors. The predictive ability of global longitudinal strain, SR, and LVEF was assessed as area under receiver operating characteristics curves (AUCs).

RESULTS

Of 100 patients enrolled in the clinical trial, 86 patients with aortic stenosis had acceptable images for global longitudinal strain analysis. Primarily, worse intraoperative global longitudinal strain was associated with prolonged hospitalization (odds ratio [98.3% confidence interval], 1.22 [1.01-1.47] per 1% decrease [absolute value] in strain; P = .012), but not with other outcomes. Secondarily, worse global longitudinal SR was associated with prolonged hospitalization (odds ratio [99.7% confidence interval], 1.68 [1.01-2.79] per 0.1 second(-1) decrease [absolute value] in SR; P = .003), but not other outcomes. LVEF was not associated with any outcomes. Global longitudinal SR was the best predictor for prolonged hospitalization (AUC, 0.72), followed by global longitudinal strain (AUC, 0.67) and LVEF (AUC, 0.62).

CONCLUSIONS

Global longitudinal strain and SR are useful predictors of prolonged hospitalization in patients with aortic stenosis having an aortic valve replacement.

Myocardial Protection by Glucose-Insulin-Potassium in Moderate- to High-Risk Patients Undergoing Elective On-Pump Cardiac Surgery: A Randomized Controlled Trial

BACKGROUND

Low cardiac output syndrome is a main cause of death after cardiac surgery. We sought to assess the impact of glucose-insulin-potassium (GIK) to enhance myocardial protection in moderate- to high-risk patients undergoing on-pump heart surgery.

METHODS

A randomized controlled trial was performed in adult patients (Bernstein-Parsonnet score >7) scheduled for elective aortic valve replacement and/or coronary artery bypass surgery. Patients were randomized to GIK (20 IU of insulin, 10 mEq of potassium chloride in 50 mL of glucose 40%) or saline infusion given over 60 minutes on anesthetic induction. The primary end point was postcardiotomy ventricular dysfunction (PCVD), defined as new/worsening left ventricular dysfunction requiring inotropic support (≥120 minutes). Secondary end points were the intraoperative changes in left ventricular function as assessed by transoesophageal echocardiography, postoperative troponin levels, cardiovascular and respiratory complications, and intensive care unit and hospital length of stay.

RESULTS

From 224 randomized patients, 222 were analyzed (112 and 110 in the placebo and GIK groups, respectively). GIK pretreatment was associated with a reduced occurrence of PCVD (risk ratio [RR], 0.41; 95% confidence interval [CI], 0.25-0.66). In GIK-treated patients, the left systolic ventricular function was better preserved after weaning from bypass, plasma troponin levels were lower on the first postoperative day (2.9 ng·mL(-) [interquartile range {IQR}, 1.5-6.6] vs 4.3 ng·mL(-) [IQR, 2.4-8.2]), and cardiovascular (RR, 0.69; 95% CI, 0.50-0.89) and respiratory complications (RR, 0.5; 95% CI, 0.38-0.74) were reduced, along with a shorter length of stay in intensive care unit (3 days [IQR, 2-4] vs 3.5 days [IQR, 2-7]) and in hospital (14 days [IQR, 11-18.5] vs 16 days [IQR, 12.5-23.5]), compared with placebo-treated patients.

CONCLUSIONS

GIK pretreatment was shown to attenuate PCVD and to improve clinical outcome in moderate- to high-risk patients undergoing on-pump cardiac surgery.

A Comparison of Global Longitudinal, Circumferential, and Radial Strain to Predict Outcomes After Cardiac Surgery

OBJECTIVE

Myocardial strain measured by speckle-tracking echocardiography detects subtle regional and global left ventricular dysfunction. Myocardial strain is measured in the longitudinal, circumferential, and radial dimensions; however, it is unclear which dimension of strain is the best predictor of postoperative outcomes.

DESIGN

A secondary analysis of prospectively collected data from a clinical trial (NCT01187329).

SETTING

The cardiothoracic surgical operating rooms of an academic tertiary-care center.

PARTICIPANTS

Cardiothoracic surgery patients with aortic stenosis having aortic valve replacement (AVR) with or without coronary artery bypass grafting enrolled in a clinical trial.

INTERVENTIONS

Myocardial deformation analysis from standardized investigative transesophageal echocardiographic examinations performed after induction of anesthesia.

MEASUREMENTS AND MAIN RESULTS

The authors compared the ability of intraoperative global longitudinal strain (GLS), global circumferential strain (GCS), and global radial strain (GRS) strain to predict adverse postoperative outcomes, including prolonged hospitalization and the need for pharmacologic hemodynamic support after cardiac surgery. The association of GLS, GCS, and GRS with prolonged hospitalization (>7 days) and the need for pharmacologic hemodynamic support, with epinephrine or norepinephrine after cardiopulmonary bypass, were assessed using separate multivariable logistic regression models with adjustment for multiple comparisons. Of 100 patients, 86 had acceptable measurements for GLS analysis, 73 for GCS, and 72 for GRS. Worse GLS was associated with prolonged hospitalization [odds ratio [OR] (98.3% confidence interval [CI]) of 1.21 (1.01-1.46) per-unit worsening in strain (p = 0.01, significance criterion <0.0167)] and the need for inotropic support with epinephrine [OR (99.2% CI) of 1.81 (1.10-2.97) per-unit worsening in strain (p = 0.002, significance criterion <0.0083)], but not norepinephrine. GCS and GRS were not associated with adverse outcomes.

CONCLUSION

GLS, but not GCS or GRS, predicts prolonged hospitalization and the requirement for inotropic support with epinephrine after AVR.

Early Left and Right Ventricular Response to Aortic Valve Replacement

BACKGROUND

The immediate effect of aortic valve replacement (AVR) for aortic stenosis on perioperative myocardial function is unclear. Left ventricular (LV) function may be impaired by cardioplegia-induced myocardial arrest and ischemia-reperfusion injury, especially in patients with LV hypertrophy. Alternatively, LV function may improve when afterload is reduced after AVR. The right ventricle (RV), however, experiences cardioplegic arrest without benefiting from improved loading conditions. Which of these effects on myocardial function dominate in patients undergoing AVR for aortic stenosis has not been thoroughly explored. Our primary objective is thus to characterize the effect of intraoperative events on LV function during AVR using echocardiographic measures of myocardial deformation. Second, we evaluated RV function.

METHODS

In this supplementary analysis of 100 patients enrolled in a clinical trial (NCT01187329), 97 patients underwent AVR for aortic stenosis. Of these patients, 95 had a standardized intraoperative transesophageal echocardiographic examination of systolic and diastolic function performed before surgical incision and repeated after chest closure. Echocardiographic images were analyzed off-line for global longitudinal myocardial strain and strain rate using 2D speckle-tracking echocardiography. Myocardial deformation assessed at the beginning of surgery was compared with the end of surgery using paired t tests corrected for multiple comparisons.

RESULTS

LV volumes and arterial blood pressure decreased, and heart rate increased at the end of surgery. Echocardiographic images were acceptable for analysis in 72 patients for LV strain, 67 for LV strain rate, and 54 for RV strain and strain rate. In 72 patients with LV strain images, 9 patients required epinephrine, 22 required norepinephrine, and 2 required both at the end of surgery. LV strain did not change at the end of surgery compared with the beginning of surgery (difference: 0.7 [97.6% confidence interval, -0.2 to 1.5]%; P = 0.07), whereas LV systolic strain rate improved (became more negative) (-0.3 [-0.4 to -0.2] s; P < 0.001). In contrast, RV systolic strain worsened (became less negative) at the end of surgery (difference: 4.6 [3.1 to 6.0]%; P < 0.001) although RV systolic strain rate was unchanged (0.0 [97.6% confidence interval, -0.1 to 0.1]; P = 0.83).

CONCLUSIONS

LV function improved after replacement of a stenotic aortic valve demonstrated by improved longitudinal strain rate. In contrast, RV function, assessed by longitudinal strain, was reduced.

The response to Trendelenburg position is minimally affected by underlying hemodynamic conditions in patients with aortic stenosis

PURPOSE

Trendelenburg positioning is commonly used to temporarily treat intraoperative hypotension. The Trendelenburg position improves cardiac output in normovolemic or anesthetized patients, but not hypovolemic or non-anesthetized patients. Therefore, the response to Trendelenburg positioning may vary depending on patient population or hemodynamic conditions. We thus tested the hypothesis that the effectiveness of the Trendelenburg position, as indicated by an increase in cardiac output, improves after replacement of a stenotic aortic valve. Secondarily, we evaluated whether measurements of left ventricular preload, systolic function, or afterload were associated with the response to Trendelenburg positioning.

METHODS

This study is a secondary analysis of a clinical trial which included patients having aortic valve replacement (AVR) who were monitored with pulmonary artery catheters (NCT01187329). We examined changes in thermodilution cardiac output with Trendelenburg positioning before and after AVR. We also examined whether echocardiographic and hemodynamic measurements of preload, afterload, and systolic function were associated with changes in cardiac output during Trendelenburg positioning.

RESULTS

Thirty-seven patients were included. The median [IQR] cardiac output change with Trendelenburg positioning was -3% [-10%, 5%] before AVR versus +4% [-4%, 15%] after AVR. Estimated median difference in cardiac output with Trendelenburg was 5% (95% CI 1, 15%, P = 0.04) greater after AVR. The response to Trendelenburg positioning was largely independent of hemodynamic conditions.

CONCLUSION

The response to Trendelenburg positioning improved following AVR, but by a clinically unimportant amount. The response to Trendelenburg positioning was independent of hemodynamic conditions.

Experience using high-dose glucose-insulin-potassium (GIK) in critically ill patients

PURPOSE

To audit the use of GIK in terms of safety, haemodynamic effects, and impact on catecholamine dosage.

MATERIALS AND METHODS

A retrospective, descriptive, evaluative audit of GIK use within the adult ICU of a London teaching hospital was conducted. Rescue therapy of GIK (up to 1.0Unitsinsulin/kg/h) was administered to improve cardiac function. Outcomes were ICU survival, change in cardiac index (CI) and blood lactate levels, events of hypoglycaemia, hyperglycaemia, hypokalaemia and hyperkalaemia, and discontinuation time of catecholamine inotropes.

RESULTS

Of 85 patients treated with GIK, 13 (15.3%) survived their ICU stay and 9 (10.5%) were discharged home. In patients surviving until 72h, a trend of improved CI and lactate levels was seen, often with reductions in catecholamine dosing. Inotropes were discontinued in 35 (54%) patients. Severe hypoglycaemia (<2mmol/l), hyperglycaemia (>20mmol/l), hypokalaemia (<2.5mmol/l) and hyperkalaemia (>7mmol/l) during GIK affected 1, 6, 8 and 1 patients, respectively. These abnormalities were quickly identified. No measurable harm was noted.

CONCLUSIONS

High-dose GIK can be safely used in critically ill patients, though blood glucose and potassium levels must be monitored frequently. GIK was associated with improved CI and blood lactate levels. Impact on survival requires prospective evaluation.

Hyperinsulinemic normoglycemia decreases glucose variability during cardiac surgery

PURPOSE

Increased glucose variability may be associated with worse outcomes in critically ill patients. Hyperinsulinemic normoglycemia provides intensive glucose control during surgery and may reduce glucose variability. Our objective was to compare glycemic variability between two methods of glucose control in cardiac surgical patients: hyperinsulinemic normoglycemia vs standard insulin infusion. We also assessed whether the effect differed between patients with and without diabetes mellitus.

METHODS

We compared measures of glycemic variability, including the primary outcome, average real variability (ARV), and secondary outcomes, within-patient standard deviation (SD) and glucose lability index (GLI), in 252 patients who received hyperinsulinemic normoglycemia and 266 patients who received standard therapy. Data was randomly sampled from each patient treated with hyperinsulinemic normoglycemia, so patients in each group had a similar number of glucose measurements. The significance level for each hypothesis was 0.05, and 0.025 within diabetic status.

RESULTS

For nondiabetic patients, hyperinsulinemic normoglycemia reduced mean glucose measure-to-measure variability for ARV by an estimated -0.23 (97.5% CI -0.30, -0.16) mg/dl/min (P < 0.001) versus standard care. There was no difference in glycemic variability between groups for diabetic patients, with difference in means (97.5% CI) of -0.10 (-0.20, 0.02) mg/dl/min, P = 0.07. Mean SD was lower for hyperinsulinemic normoglycemia patients overall, with difference in means (95% CI) of -19 (-22, -16), P < 0.001, with a stronger effect in nondiabetics (interaction P = 0.042). GLI was also lower with hyperinsulinemic normoglycemia.

CONCLUSION

Hyperinsulinemic normoglycemia decreases glucose variability for cardiac surgical patients with a stronger effect in nondiabetic patients.

The effect of perioperative insulin treatment on cardiodepression in mild adiposity in mice

Background

While most studies focus on cardiovascular morbidity following anesthesia and surgery in excessive obesity, it is unknown whether these intraoperative cardiovascular alterations also occur in milder forms of adiposity without type 2 diabetes and if insulin is a possible treatment to improve intraoperative myocardial performance. In this experimental study we investigated whether mild adiposity without metabolic alterations is already associated with cardiometabolic dysfunction during anesthesia, mechanical ventilation and surgery and whether these myocardial alterations can be neutralized by intraoperative insulin treatment.

Methods

Mice were fed a western (WD) or control diet (CD) for 4 weeks. After metabolic profiling, mice underwent general anesthesia, mechanical ventilation and surgery. Cardiac function was determined with echocardiography and left-ventricular pressure–volume analysis. Myocardial perfusion was determined with contrast-enhanced echocardiography. WD-fed mice were subsequently treated with insulin by hyperinsulinemic euglycemic clamping followed by the same measurements of cardiac function and perfusion.

Results

Western-type diet feeding led to a 13 % increase in bodyweight, (p < 0.0001) and increased adipose tissue mass, without metabolic alterations. Despite this mild phenotype, WD-fed mice had decreased systolic and diastolic function (end-systolic elastance was 2.0 ± 0.5 versus 4.1 ± 2.4 mmHg/μL, p = 0.01 and diastolic beta was 0.07 ± 0.03 versus 0.04 ± 0.01 mmHg/μL, p = 0.02) compared to CD-fed mice. Ventriculo-arterial coupling and myocardial perfusion were decreased by 48 % (p = 0.003) and 43 % (p = 0.03) respectively. Insulin treatment in WD-fed mice improved echo-derived systolic function (fractional shortening 42 ± 5 % to 46 ± 3, p = 0.05), likely due to decreased afterload, but there was no effect on load-independent measures of systolic function or myocardial perfusion. However, there was a trend towards improved diastolic function after insulin treatment (43 % improvement, p = 0.05) in WD-fed mice.

Conclusions

Mild adiposity without metabolic alterations already affected cardiac function and perfusion during anesthesia, mechanical ventilation and surgery in mice. Intraoperative insulin may be beneficial to reduce afterload and enhance intraoperative ventricular relaxation, but not to improve ventricular contractility or myocardial perfusion.