Metabolic changes after cardiac surgery

Nitric Oxide in Cardiac Surgery: A Review Article

Perioperative organ injury remains a medical, social and economic problem in cardiac surgery. Patients with postoperative organ dysfunction have increases in morbidity, length of stay, long-term mortality, treatment costs and rehabilitation time. Currently, there are no pharmaceutical technologies or non-pharmacological interventions that can mitigate the continuum of multiple organ dysfunction and improve the outcomes of cardiac surgery. It is essential to identify agents that trigger or mediate an organ-protective phenotype during cardiac surgery. The authors highlight nitric oxide (NO) ability to act as an agent for perioperative protection of organs and tissues, especially in the heart-kidney axis. NO has been delivered in clinical practice at an acceptable cost, and the side effects of its use are known, predictable, reversible and relatively rare. This review presents basic data, physiological research and literature on the clinical application of NO in cardiac surgery. Results support the use of NO as a safe and promising approach in perioperative patient management. Further clinical research is required to define the role of NO as an adjunct therapy that can improve outcomes in cardiac surgery. Clinicians also have to identify cohorts of responders for perioperative NO therapy and the optimal modes for this technology.

The Quality of Preoperative Glycemic Control Predicts Insulin Sensitivity During Major Upper Abdominal Surgery: A Case-Control Study

Objective

To examine the association of the quality of preoperative glycemic control and insulin sensitivity during major upper abdominal surgery.

Background

In cardiac surgery, glycated hemoglobin A1c (HbA1c), an indicator of glycemic control during the preceding 3 months, correlated with intraoperative insulin sensitivity. Furthermore, insulin resistance showed a significant association with adverse clinical outcomes.

Methods

This study is a post hoc exploratory analysis of a randomized controlled trial in patients undergoing elective hepatectomy and receiving the hyperinsulinemic-normoglycemic clamp (HNC) as a potential intervention to reduce surgical site infections (ClinicalTrials.gov NCT01528189). Immediately before skin incision, the HNC was initiated by infusing insulin at the rate of 2 mU/kg/min. Dextrose was administered at rates titrated to maintain normoglycemia (4.0-6.0 mmol/L). The average of 3 consecutive dextrose infusion rates during steady state was used as a measure of insulin sensitivity. Primary outcome was the relationship between preoperative HbA1c and insulin sensitivity during surgery. Secondary outcomes were the associations of insulin sensitivity with the patient's body mass index (BMI) and postoperative morbidity.

Results

Thirty-four patients were studied. HbA1c (Y = -0.52X + 4.8, P < 0.001, R2 = 0.29), BMI (Y = -0.12X + 5.0, P < 0.001, R2 = 0.43) showed negative correlations with insulin sensitivity. The odds ratio of postoperative complications within 30 days of surgery for every increase in insulin sensitivity by 1 mg/kg/min was 0.22 (95% confidential interval, 0.06-0.59; P = 0.009).

Conclusions

We demonstrate significant associations of the quality of preoperative glycemic control and body mass index with insulin sensitivity during hepatectomy. The degree of insulin resistance correlated with postoperative morbidity.

Effects of pre-operative oral carbohydrates on insulin resistance and postoperative recovery in diabetic patients undergoing coronary artery bypass grafting: study protocol for a prospective, single-blind, randomized controlled trial

BACKGROUND

Preoperative carbohydrates (CHO) supplement has been widely investigated in nondiabetic patients undergoing a variety of surgeries. It has been proved that preoperative CHO could alleviate postoperative insulin resistance (IR) and improve patients' well-being in nondiabetic patients. However, it remains controversial whether preoperative CHO could yield similar effects in diabetic patients. Till now, seldom has the administration of preoperative CHO been investigated in diabetic patients and there are limited studies reporting IR and postoperative recovery of diabetic patients undergoing cardiac surgery.

METHODS AND ANALYSIS

We present a prospective, single-center, single-blind, randomized, no-treatment controlled trial of preoperative CHO on diabetic patients undergoing off-pump coronary artery bypass grafting (OPCAB). A total of 62 patients will be enrolled and randomized to either Group CHO or Group control (CTRL). Patients in Group CHO will consume CHO fluid containing 50 g carbohydrates orally the evening before surgery (20:00-24:00) while their counterparts in Group CTRL will be fasted after 20:00 the evening before surgery. The primary endpoint is postoperative IR assessed via homeostasis model assessment (HOMA). The secondary endpoints are postoperative levels of potential mediators relating to IR including inflammatory factors and stress reaction characterized by serum cortisol. Exploratory endpoints are in-hospital clinical endpoints. Continuous variables will be compared by Student's t-test or Mann-Whitney U test. Categorical variables will be compared with χ² test or Fisher's exact test. All tests in the present study are two-tailed and P<0.05 is considered statistically significant. All analyses will be performed with R 4.0.4.

DISCUSSION

This is the first prospective randomized controlled trial of preoperative CHO in diabetic patients undergoing cardiac surgery, with the hypothesis that preoperative CHO could improve postoperative IR and promote postoperative recovery. The research may assist in improving the clinical outcomes of diabetic patients undergoing OPCAB.

TRIAL REGISTRATION

The trial has been prospectively registered with ClinicalTrials.gov ( https://register.

CLINICALTRIALS

gov ) and Chinese Clinical Trial Registry ( http://www.chictr.org.cn ). Registry number is NCT05540249 and ChiCTR2000029664 respectively. Registered on Sept. 14, 2022.

CLINICAL TRIALS UNIT

Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.

Comparison of Machine Learning Models Including Preoperative, Intraoperative, and Postoperative Data and Mortality After Cardiac Surgery

IMPORTANCE

A variety of perioperative risk factors are associated with postoperative mortality risk. However, the relative contribution of routinely collected intraoperative clinical parameters to short-term and long-term mortality remains understudied.

OBJECTIVE

To examine the performance of multiple machine learning models with data from different perioperative periods to predict 30-day, 1-year, and 5-year mortality and investigate factors that contribute to these predictions.

DESIGN, SETTING, AND PARTICIPANTS

In this prognostic study using prospectively collected data, risk prediction models were developed for short-term and long-term mortality after cardiac surgery. Included participants were adult patients undergoing a first-time valve operation, coronary artery bypass grafting, or a combination of both between 1997 and 2017 in a single center, the University Medical Centre Groningen in the Netherlands. Mortality data were obtained in November 2017. Data analysis took place between February 2020 and August 2021.

EXPOSURE

Cardiac surgery.

MAIN OUTCOMES AND MEASURES

Postoperative mortality rates at 30 days, 1 year, and 5 years were the primary outcomes. The area under the receiver operating characteristic curve (AUROC) was used to assess discrimination. The contribution of all preoperative, intraoperative hemodynamic and temperature, and postoperative factors to mortality was investigated using Shapley additive explanations (SHAP) values.

RESULTS

Data from 9415 patients who underwent cardiac surgery (median [IQR] age, 68 [60-74] years; 2554 [27.1%] women) were included. Overall mortality rates at 30 days, 1 year, and 5 years were 268 patients (2.8%), 420 patients (4.5%), and 612 patients (6.5%), respectively. Models including preoperative, intraoperative, and postoperative data achieved AUROC values of 0.82 (95% CI, 0.78-0.86), 0.81 (95% CI, 0.77-0.85), and 0.80 (95% CI, 0.75-0.84) for 30-day, 1-year, and 5-year mortality, respectively. Models including only postoperative data performed similarly (30 days: 0.78 [95% CI, 0.73-0.82]; 1 year: 0.79 [95% CI, 0.74-0.83]; 5 years: 0.77 [95% CI, 0.73-0.82]). However, models based on all perioperative data provided less clinically usable predictions, with lower detection rates; for example, postoperative models identified a high-risk group with a 2.8-fold increase in risk for 5-year mortality (4.1 [95% CI, 3.3-5.1]) vs an increase of 11.3 (95% CI, 6.8-18.7) for the high-risk group identified by the full perioperative model. Postoperative markers associated with metabolic dysfunction and decreased kidney function were the main factors contributing to mortality risk.

CONCLUSIONS AND RELEVANCE

This study found that the addition of continuous intraoperative hemodynamic and temperature data to postoperative data was not associated with improved machine learning-based identification of patients at increased risk of short-term and long-term mortality after cardiac operations.

Nutritional Management of Patients with Fontan Circulation: A Potential for Improved Outcomes from Birth to Adulthood

Fontan circulation (FC) is a surgically achieved palliation state offered to patients affected by a wide variety of congenital heart defects (CHDs) that are grouped under the name of univentricular heart. The procedure includes three different surgical stages. Malnutrition is a matter of concern in any phase of life for these children, often leading to longer hospital stays, higher mortality rates, and a higher risk of adverse neurodevelopmental and growth outcomes. Notwithstanding the relevance of proper nutrition for this subset of patients, specific guidelines on the matter are lacking. In this review, we aim to analyze the role of an adequate form of nutritional support in patients with FC throughout the different stages of their lives, in order to provide a practical approach to appropriate nutritional management. Firstly, the burden of faltering growth in patients with univentricular heart is analyzed, focusing on the pathogenesis of malnutrition, its detection and evaluation. Secondly, we summarize the nutritional issues of each life phase of a Fontan patient from birth to adulthood. Finally, we highlight the challenges of nutritional management in patients with failing Fontan.

Fatal outcome after heart surgery in PMM2-CDG due to a rare homozygous gene variant with double effects

Variants in Phosphomannomutase 2 (PMM2) lead to PMM2-CDG, the most frequent congenital disorder of glycosylation (CDG). We here describe the disease course of a ten-month old patient who presented with the classical PMM2-CDG symptoms as cerebellar hypoplasia, retinitis pigmentosa, seizures, short stature, hepato- and splenomegaly, anaemia, recurrent vomiting and inverted mamillae. A severe form of tetralogy of Fallot was diagnosed and corrective surgery was performed at the age of 10 months. At the end of the cardiopulmonary bypass, a sudden oedematous reaction of the myocardium accompanied by biventricular pump failure was observed immediately after heparin antagonization with protamine sulfate. The patient died seven days after surgery, since myocardial function did not recover on ECMO support. We here describe the first patient carrying the homozygous variant g.18313A > T in the PMM2 gene (NG_009209.1) that either can lead to c.394A > T (p.I132F) or even loss of 100 bp due to exon 5 skipping (c.348_447del; p.G117Rfs*4) which is comparable to a null allele. Proliferation and doubling time of the patient's fibroblasts were affected. In addition, we show that the induction of cellular stress by elevating the cell culture temperature to 40 °C led to a decrease of the patients' PMM2 transcript as well as PMM2 protein levels and subsequently to a significant loss of residual activity. We assume that metabolic stressful processes occurring after cardiac surgery led to the drop of the patient's PMM activity below a life-sustaining niveau which paved the way for the fatal outcome.

Adverse Outcomes in Obese Cardiac Surgery Patients Correlates With Altered Branched-Chain Amino Acid Catabolism in Adipose Tissue and Heart

Background: Predicting relapses of post-operative complications in obese patients who undergo cardiac surgery is significantly complicated by persistent metabolic maladaptation associated with obesity. Despite studies supporting the linkages of increased systemic branched-chain amino acids (BCAAs) driving the pathogenesis of obesity, metabolome wide studies have either supported or challenged association of circulating BCAAs with cardiovascular diseases (CVDs). Objective: We interrogated whether BCAA catabolic changes precipitated by obesity in the heart and adipose tissue can be reliable prognosticators of adverse outcomes following cardiac surgery. Our study specifically clarified the correlation between BCAA catabolizing enzymes, cellular BCAAs and branched-chain keto acids (BCKAs) with the severity of cardiometabolic outcomes in obese patients pre and post cardiac surgery. Methods: Male and female patients of ages between 44 and 75 were stratified across different body mass index (BMI) (non-obese = 17, pre-obese = 19, obese class I = 14, class II = 17, class III = 12) and blood, atrial appendage (AA), and subcutaneous adipose tissue (SAT) collected during cardiac surgery. Plasma and intracellular BCAAs and BC ketoacids (BCKAs), tissue mRNA and protein expression and activity of BCAA catabolizing enzymes were assessed and correlated with clinical parameters. Results: Intramyocellular, but not systemic, BCAAs increased with BMI in cardiac surgery patients. In SAT, from class III obese patients, mRNA and protein expression of BCAA catabolic enzymes and BCKA dehydrogenase (BCKDH) enzyme activity was decreased. Within AA, a concomitant increase in mRNA levels of BCAA metabolizing enzymes was observed, independent of changes in BCKDH protein expression or activity. BMI, indices of tissue dysfunction and duration of hospital stay following surgery correlated with BCAA metabolizing enzyme expression and metabolite levels in AA and SAT. Conclusion: This study proposes that in a setting of obesity, dysregulated BCAA catabolism could be an effective surrogate to determine cardiac surgery outcomes and plausibly predict premature re-hospitalization.

Evaluation of preoperative oral carbohydrate administration on insulin resistance in off-pump coronary artery bypass patients: A randomised trial

BACKGROUND

In fasting cardiac surgery patients, preoperative carbohydrate (CHO) drink intake attenuated insulin resistance and improved cardiac metabolism, although its beneficial effects were not evident after cardiac surgery possibly due to cardiopulmonary bypass-related extreme systemic inflammation.

OBJECTIVE

We aimed to evaluate whether preoperative CHO intake affected insulin resistance and free-fatty acid (FFA) concentrations in off-pump coronary revascularisation.

DESIGN

A randomised controlled trial.

SETTING

Primary care in a university hospital in Korea from January 2015 to July 2016.

PATIENTS

Sixty patients who underwent elective multi-vessel off-pump coronary revascularisation were randomised into two groups. Three patients were excluded from analysis and 57 patients completed study.

INTERVENTION

The CHO group received oral CHO (400 ml) the prior evening and 2 to 3 h before surgery, and the control group was fasted from food and water according to standard protocol.

MAIN OUTCOME MEASURES

Insulin resistance was assessed twice, after anaesthetic induction and after surgery via short insulin tolerance test. FFA, C-reactive protein and creatine kinase-myocardial band concentrations were determined serially for 48 h after surgery.

RESULTS

Insulin sensitivity was greater (P = 0.002) and plasma FFA concentrations were lower (P = 0.001) after anaesthetic induction in the CHO group compared with the Control group, although there were no intergroup differences after surgery. The postoperative peak creatine kinase-myocardial band concentration was significantly lower in the CHO group compared with the Control group [8.8 (5.4 to 18.2) vs. 6.4 (3.5 to 9.7) ng ml, P = 0.031].

CONCLUSION

A preoperative CHO supplement significantly reduced insulin resistance and FFA concentrations compared with fasting at the beginning of the surgery, but these benefits were lost after off-pump coronary revascularisation. Despite their transient nature, these beneficial effects resulted in less myocardial injury, mandating further studies focused on the impact of preoperative CHO on myocardial ischaemia and cardiac function after coronary revascularisation.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT 02330263.

Multimedia Exercise Training Program Improves Distance Walked, Heart Rate Recovery, and Self-efficacy in Cardiac Surgery Patients

BACKGROUND

Patient education has been shown to be more effective when delivered using multimedia than written materials. However, the effects of using multimedia to assist patients in cardiac rehabilitation have not been investigated.

OBJECTIVE

The purpose of this study is to examine the effect of an inpatient multimedia exercise training program on distance walked in the 6-minute walking test (6MWT), heart rate recovery, and walking self-efficacy of patients who had undergone heart surgery.

METHODS

For this longitudinal quasi-experimental study, 60 consecutive patients were assigned to an experimental (n = 20; inpatient multimedia exercise training program) or control (n = 40; routine care) group. Data were collected at 3 times (before surgery, 1 to 2 days before hospital discharge, and 1 month after hospital discharge) and analyzed with the generalized estimating equation approach.

RESULTS

Most subjects were men (66.7%), had a mean age of 61.32 ± 13.4 years and left ventricular ejection fraction of 56.96% ± 13.28%, and underwent coronary artery bypass graft surgery (n = 34, 56.7%). Subjects receiving the exercise training program showed significantly greater improvement than those in the control group in the 6MWT walking distance (P < .001), heart rate recovery (P = .04), and self-efficacy (P = .002) at hospital discharge. Furthermore, the intervention effects on 6MWT distance (P < .001) and self-efficacy (P < .001) were sustained at 1 month after hospital discharge.

CONCLUSION

Our inpatient multimedia exercise training program safely improved distance walked in the 6MWT, heart rate recovery, and self-efficacy at hospital discharge in patients after heart surgery and maintained their improvement in 6MWT and self-efficacy 1 month later.

Lactate Elevation During and After Major Cardiac Surgery in Adults: A Review of Etiology, Prognostic Value, and Management

Elevated lactate is a common occurrence after cardiac surgery. This review summarizes the literature on the complex etiology of lactate elevation during and after cardiac surgery, including considerations of oxygen delivery, oxygen utilization, increased metabolism, lactate clearance, medications and fluids, and postoperative complications. Second, the association between lactate and a variety of outcomes are described, and the prognostic role of lactate is critically assessed. Despite the fact that elevated lactate is strongly associated with many important outcomes, including postoperative complications, length of stay, and mortality, little is known about the optimal management of postoperative patients with lactate elevations. This review ends with an assessment of the limited literature on this subject.

Postnatal serum concentrations of endogenous free fatty acids in newborns admitted to the neonatal intensive care unit: effects on unbound bilirubin

Background

Few studies have reported the characterization of postnatal serum concentrations of endogenous free fatty acids (FFAs) in high-risk newborns and their effects on unbound bilirubin (UB).

Methods

Serum concentrations of FFA, albumin (Alb), UB and total bilirubin (TB) were measured in 713 samples obtained within 5 days after birth from 439 newborns without intravenous lipid supplementation admitted to the neonatal intensive care unit (NICU). Serum FFA was reported as the day-specific percentile-based curve. Serum FFA and FFA/Alb ratios were compared in term and preterm patients. To assess the impact of FFA on UB, daily changes in FFA/Alb and UB/TB ratios were compared in term patients without receiving phototherapy or any drugs, and linear regression analysis was performed between FFA/Alb ratio and serum UB concentration or UB/TB ratio using 140 sera with hyperbilirubinemia of term and preterm patients.

Results

A percentile-based curve showed that serum FFA peaked at 1 day of age and progressively decreased. Serum FFA and the FFA/Alb ratio were significantly higher in term than in preterm patients at birth and 1 and 3 days of age. FFA/Alb ratio significantly changed over 5 days after birth, but UB/TB ratio remained constant. FFA/Alb ratio did not correlate with serum UB concentration or UB/TB ratio in sera with hyperbilirubinemia.

Conclusions

We assessed postnatal concentrations of serum FFA in a large number of high-risk newborns admitted to the NICU. The concentration of endogenous FFAs in newborns admitted to the NICU was not rising until it influenced UB.

Does a reduced glucose intake prevent hyperglycemia in children early after cardiac surgery? a randomized controlled crossover study

INTRODUCTION

Hyperglycemia in children after cardiac surgery can be treated with intensive insulin therapy, but hypoglycemia is a potential serious side effect. The aim of this study was to investigate the effects of reducing glucose intake below standard intakes to prevent hyperglycemia, on blood glucose concentrations, glucose kinetics and protein catabolism in children after cardiac surgery with cardiopulmonary bypass (CPB).

METHODS

Subjects received a 4-hour low glucose (LG; 2.5 mg/kg per minute) and a 4-hour standard glucose (SG; 5.0 mg/kg per minute) infusion in a randomized blinded crossover setting. Simultaneously, an 8-hour stable isotope tracer protocol was conducted to determine glucose and leucine kinetics. Data are presented as mean ± SD or median (IQR); comparison was made by paired samples t test.

RESULTS

Eleven subjects (age 5.1 (20.2) months) were studied 9.5 ± 1.9 hours post-cardiac surgery. Blood glucose concentrations were lower during LG than SG (LG 7.3 ± 0.7 vs. SG 9.3 ± 1.8 mmol/L; P < 0.01), although the glycemic target (4.0-6.0 mmol/L) was not achieved. No hypoglycemic events occurred. Endogenous glucose production was higher during LG than SG (LG 2.9 ± 0.8 vs. SG 1.5 ± 1.1 mg/kg per minute; P = 0.02), due to increased glycogenolysis (LG 1.0 ± 0.6 vs. SG 0.0 ± 1.0 mg/kg per minute; P < 0.05). Leucine balance, indicating protein balance, was negative but not affected by glucose intake (LG -54.8 ± 14.6 vs. SG -58.8 ± 16.7 μmol/kg per hour; P = 0.57).

CONCLUSIONS

Currently recommended glucose intakes aggravated hyperglycemia in children early after cardiac surgery with CPB. Reduced glucose intake decreased blood glucose concentrations without causing hypoglycemia or affecting protein catabolism, but increased glycogenolysis.

TRIAL REGISTRATION

Dutch trial register NTR2079.

Postoperative cognitive dysfunction is correlated with urine formaldehyde in elderly noncardiac surgical patients

Post-operative cognitive dysfunction (POCD), especially in elderly patients, has been reported in many studies. Although increasing age, duration of anesthesia, postoperative infections, and respiratory complications were regarded as the risk factors for POCD, no extracerebral diagnostic biomarkers have been identified as indicators of POCD. Ninety-five patients, ages 65-80 years, scheduled for major orthopedic or abdominal surgery were enrolled. Twenty-two patients aged between 20 and 40 years undergoing the same procedures served as controls. Subjects received neuropsychological tests one-day prior and one week post procedure. To determine the presence of POCD, the criteria were used as described in most previous studies. Morning urine samples were obtained one day before surgery and on day 1, day 2 and day 7 post operatively. Urine formaldehyde was determined with high-performance liquid chromatography. The urine formaldehyde level of all patients with and without POCD increased on the first 2 days after surgery. But the formaldehyde concentration (on day 7) in patients with POCD was significantly higher than that in patients without POCD (p < 0.01). In the young control group, no patient was diagnosed with POCD. Although the changes in urine formaldehyde of young patients during perioperative period were similar to those in elderly patients without POCD, the formaldehyde concentrations measured at four time points were all significantly lower than those in elderly patients (p < 0.05). Levels of urine formaldehyde were elevated in the perioperative period, with the highest levels at day 7 in patients with POCD. This suggests that the increase on day 7 may provide a new physiologic marker along with neuropsychological assessments to assist in the diagnosis of POCD.

Resting energy expenditure after Fontan surgery in children with single-ventricle heart defects

BACKGROUND

Data on resting energy expenditure (REE) and oxygen consumption (VO(2)) after pediatric cardiopulmonary bypass (CPB) will facilitate optimal nutrient prescription.

METHODS

The authors measured continuous REE and VO(2), using an in-line indirect calorimetery (IC) in 30 consecutive children with single-ventricle physiology immediately after Fontan surgery. REE during steady state at 8 hours after surgery was compared with standard equation-estimated energy expenditure (EEE). Patients were classified into 3 groups: hypermetabolic (measured REE [MREE]/EEE ratio >1.2), hypometabolic (MREE/EEE ratio <0.8), and normometabolic (MREE/EEE ratio 0.8-1.2). Demographic, anthropometric, and perioperative clinical characteristics were examined for their correlation with metabolic status.

RESULTS

In 26 of 30 patients with completed IC, mean REE at 8 hours after surgery was 57 ± 20 kcal/kg/d, and mean VO(2) was 110 ± 35 mL/min. Mean values of VO(2) and REE did not change within the first 24 hours after surgery. There was poor correlation between MREE at 8 hours and the EEE using the World Health Organization equation (r = 0.32, P = .11). Most patients (n = 19, 73%) were either normometabolic or hypometabolic. Lack of hypermetabolism was significantly associated with higher intraoperative serum lactate level and positive fluid balance compared with the rest of the group.

CONCLUSIONS

The authors report a low prevalence of hypermetabolism in children with single-ventricle defects after Fontan surgery. Measured REE had poor correlation with equation-estimated energy expenditure in a majority of the cohort. The absence of increased energy expenditure after CPB will influence energy prescription in this group.

Continuous glucose monitoring in patients undergoing cardiac surgery

OBJECTIVES

Hyperglycemia is a prominent feature among patients exposed to major stress such as in cardiac surgery. The implementation of a continuous glucose monitoring system (CGMS) for glucose monitoring during cardiac surgery was assessed.

SUBJECTS AND METHODS

Fifty-nine consecutive patients who underwent cardiac surgery were monitored by CGMS. Patients' fluid glucose content, drug requirements, and hemodynamic and physiologic parameters were evaluated.

RESULTS

Of the 59 patients, 32 completed the monitoring with CGMS. Patients were divided into three groups: diabetes patients, patients without diabetes history who developed significant hyperglycemia perioperatively, and patients who did not develop hyperglycemia. Hyperglycemia was most frequently observed postoperatively. Hyperglycemic patients required significantly more insulin (81±40 vs. 34±37 units, P=0.005) and experienced an increased early complication rate, although this difference was not significant. CGMS erroneously detected late-phase operative and immediate postoperative hypoglycemia in approximately one-third of patients as reflected from venous blood sample measurements.

CONCLUSIONS

CGMS enables close monitoring and optimal control of blood glucose among patients undergoing major cardiac surgery, although its reliability is limited during the cardiac surgery phase and in the early postoperative period, because of incorrect hypoglycemic readings.

Plasma acetate, gluconate and interleukin-6 profiles during and after cardiopulmonary bypass: a comparison of Plasma-Lyte 148 with a bicarbonate-balanced solution

INTRODUCTION

As even small concentrations of acetate in the plasma result in pro-inflammatory and cardiotoxic effects, it has been removed from renal replacement fluids. However, Plasma-Lyte 148 (Plasma-Lyte), an electrolyte replacement solution containing acetate plus gluconate is a common circuit prime for cardio-pulmonary bypass (CPB). No published data exist on the peak plasma acetate and gluconate concentrations resulting from the use of Plasma-Lyte 148 during CPB.

METHODS

Thirty adult patients were systematically allocated 1:1 to CPB prime with either bicarbonate-balanced fluid (24 mmol/L bicarbonate) or Plasma-Lyte 148. Arterial blood acetate, gluconate and interleukin-6 (IL-6) levels were measured immediately before CPB (T1), three minutes after CPB commencement (T2), immediately before CPB separation (T3), and four hours post separation (T4).

RESULTS

Acetate concentrations (normal 0.04 to 0.07 mmol/L) became markedly elevated at T2, where the Plasma-Lyte group (median 3.69, range (2.46 to 8.55)) exceeded the bicarbonate group (0.16 (0.02 to 3.49), P < 0.0005). At T3, levels had declined but the differential pattern remained apparent (Plasma-Lyte 0.35 (0.00 to 1.84) versus bicarbonate 0.17 (0.00 to 0.81)). Normal circulating acetate concentrations were not restored until T4. Similar gluconate concentration profiles and inter-group differences were seen, with a slower T3 decay. IL-6 increased across CPB, peaking at T4, with no clear difference between groups.

CONCLUSIONS

Use of acetate containing prime solutions result in supraphysiological plasma concentrations of acetate. The use of acetate-free prime fluid in CPB significantly reduced but did not eliminate large acetate surges in cardiac surgical patients. Complete elimination of acetate surges would require the use of acetate free bolus fluids and cardioplegia solutions.

TRIAL REGISTRATION

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12610000267055.

[Adrenal function after induction of cardiac surgery patients with an etomidate bolus: a retrospective study]

OBJECTIVE

A single bolus dose of etomidate decreases cortisol synthesis by inhibiting the 11-beta hydroxylase, a mitochondrial enzyme in the final step of cortisol synthesis. In our institution, all the patients undergoing cardiac surgery receive etomidate at anesthesia induction. The purpose of this study was to assess the incidence of adrenocortical dysfunction after a single dose of etomidate in selected patients undergoing major cardiac surgery and requiring high-dose norepinephrine postoperatively.

STUDY DESIGN

Retrospective descriptive study in the surgical ICU of a university hospital.

PATIENTS AND METHODS

Sixty-three patients presented acute circulatory failure requiring norepinephrine (>0,2 microg/kg/min) during the 48 hours following cardiac surgery. Absolute adrenal insufficiency was defined as a basal cortisol below 414 nmo/l (15 microg/dl) and relative adrenal insufficiency as a basal plasma cortisol between 414 nmo/l (15 microg/dl) and 938 nmo/l (34 microg/dl) with an incremental response after 250 microg of synthetic corticotropin (measured at 60 minutes) below 250 nmol/l (9 microg/dl).

RESULTS

Fourteen patients (22%) had normal corticotropin test results, 10 (16%) had absolute and 39 (62%) relative adrenal insufficiency. All patients received a low-dose steroid substitution after the corticotropin test. Substituted patients had similar clinical outcomes compared to patients with normal adrenal function.

CONCLUSION

A high incidence of relative adrenal failure was observed in selected cardiac surgery patients with acute postoperative circulatory failure.

Acid-base effects of a bicarbonate-balanced priming fluid during cardiopulmonary bypass: comparison with Plasma-Lyte 148. A randomised single-blinded study

Fluid-induced metabolic acidosis can be harmful and can complicate cardiopulmonary bypass. In an attempt to prevent this disturbance, we designed a bicarbonate-based crystalloid circuit prime balanced on physico-chemical principles with a strong ion difference of 24 mEq/l and compared its acid-base effects with those of Plasma-Lyte 148, a multiple electrolyte replacement solution containing acetate plus gluconate totalling 50 mEq/l. Twenty patients with normal acid-base status undergoing elective cardiac surgery were randomised 1:1 to a 2 litre prime of either bicarbonate-balanced fluid or Plasma-Lyte 148. With the trial fluid, metabolic acid-base status was normal following bypass initiation (standard base excess 0.1 (1.3) mEq/l, mean, SD), whereas Plasma-Lyte 148 produced a slight metabolic acidosis (standard base excess -2.2 (2.1) mEq/l). Estimated group difference after baseline adjustment was 3.6 mEq/l (95% confidence interval 2.1 to 5.1 mEq/l, P=0.0001). By late bypass, mean standard base excess in both groups was normal (0.8 (2.2) mEq/l vs. -0.8 (1.3) mEq/l, P=0.5). Strong ion gap values were unaltered with the trial fluid, but with Plasma-Lyte 148 increased significantly on bypass initiation (15.2 (2.5) mEq/l vs. 2.5 (1.5) mEq/l, P < 0.0001), remaining elevated in late bypass (8.4 (3.4) mEq/l vs. 5.8 (2.4) mEq/l, P < 0.05). We conclude that a bicarbonate-based crystalloid with a strong ion difference of 24 mEq/l is balanced for cardiopulmonary bypass in patients with normal acid-base status, whereas Plasma-Lyte 148 triggers a surge of unmeasured anions, persisting throughout bypass. These are likely to be gluconate and/or acetate. Whether surges of exogenous anions during bypass can be harmful requires further study.

Serum concentrations of cortisol, interleukin 6, leptin and adiponectin predict stress induced insulin resistance in acute inflammatory reactions

Introduction

Inflammatory stimuli are causative for insulin resistance in obesity as well as in acute inflammatory reactions. Ongoing research has identified a variety of secreted proteins that are released from immune cells and adipocytes as mediators of insulin resistance; however, knowledge about their relevance for acute inflammatory insulin resistance remains limited. In this study we aimed for a clarification of the relevance of different insulin resistance mediating factors in an acute inflammatory situation.

Methods

Insulin resistance was measured in a cohort of 37 non-diabetic patients undergoing cardiac surgery by assessment of insulin requirement to maintain euglycaemia and repeated measurements of an insulin glycaemic index. The kinetics of cortisol, interleukin 6 (IL6), tumour necrosis factor α (TNFα), resistin, leptin and adiponectin were assessed by repeated measurements in a period of 48 h.

Results

Insulin resistance increased during the observation period and peaked 22 h after the beginning of the operation. IL6 and TNFα displayed an early increase with peak concentrations at the 4-h time point. Serum levels of cortisol, resistin and leptin increased more slowly and peaked at the 22-h time point, while adiponectin declined, reaching a base at the 22-h time point. Model assessment identified cortisol as the best predictor of insulin resistance, followed by IL6, leptin and adiponectin. No additional information was gained by modelling for TNFα, resistin, catecholamine infusion rate, sex, age, body mass index (BMI), operation time or medication.

Conclusions

Serum cortisol levels are the best predictor for inflammatory insulin resistance followed by IL6, leptin and adiponectin. TNFα, and resistin have minor relevance as predictors of stress dependent insulin resistance.

Glycemic profile in infants who have undergone the arterial switch operation: hyperglycemia is not associated with adverse events

OBJECTIVE

Tight glycemic control improves outcomes in critically ill adults. There are limited data regarding the effect of glycemic profiles in infants after cardiac operations. The aim of this study was to evaluate the association of hyperglycemia and hypoglycemia on adverse events in infants undergoing the arterial switch operation.

METHODS

From 2000 through 2005, 93 infants underwent the arterial switch operation (mean age, 2.5 +/- 5.9 weeks; mean weight, 3.4 +/- 0.8 kg). All serum glucose values during the first 24 postoperative hours were documented. The effect of time spent in specific glycemic bands on adverse events was determined.

RESULTS

Twenty-three (25%; group 1) infants spent more than 50% of the time with glucose values between 80 and 110 mg/dL, and 13 (14%; group 2) spent more than 50% of the time with glucose values of greater than 200 mg/dL. A total of 71 adverse events was documented in 45 (48%) of 93 infants. Group 1 infants were more likely to have any adverse event (P = .001) and renal insufficiency (P < .001). Group 2 infants were not more likely to have adverse events. When controlling for preoperative and operative factors, being in group 1 was an independent predictor of postoperative adverse events (P = .004).

CONCLUSION

Hyperglycemia does not appear to be detrimental in postoperative infants with congenital heart disease. Infants who spent the majority of the time with glucose values between 80 and 110 mg/dL were at increased risk for adverse events. The ideal glycemic profile in the postoperative cardiac infant has yet to be defined.

Glucose metabolism and catecholamines

Until now, catecholamines were the drugs of choice to treat hypotension during shock states. Catecholamines, however, also have marked metabolic effects, particularly on glucose metabolism, and the degree of this metabolic response is directly related to the beta2-adrenoceptor activity of the individual compound used. Under physiologic conditions, infusing catecholamine is associated with enhanced rates of aerobic glycolysis (resulting in adenosine triphosphate production), glucose release (both from glycogenolysis and gluconeogenesis), and inhibition of insulin-mediated glycogenesis. Consequently, hyperglycemia and hyperlactatemia are the hallmarks of this metabolic response. Under pathophysiologic conditions, the metabolic effects of catecholamines are less predictable because of changes in receptor affinity and density and in drug kinetics and the metabolic capacity of the major gluconeogenic organs, both resulting from the disease per se and the ongoing treatment. It is also well-established that shock states are characterized by a hypermetabolic condition with insulin resistance and increased oxygen demands, which coincide with both compromised tissue microcirculatory perfusion and mitochondrial dysfunction. This, in turn, causes impaired glucose utilization and may lead to inadequate glucose supply and, ultimately, metabolic failure. Based on the landmark studies on intensive insulin use, a crucial role is currently attributed to glucose homeostasis. This article reviews the effects of the various catecholamines on glucose utilization, both under physiologic conditions, as well as during shock states. Because, to date (to our knowledge), no patient data are available, results from relevant animal experiments are discussed. In addition, potential strategies are outlined to influence the catecholamine-induced effects on glucose homeostasis.

Preoperative Oral Carbohydrate Administration to ASA III-IV Patients Undergoing Elective Cardiac Surgery

In this study we investigated the effects of preoperative oral carbohydrate administration on postoperative insulin resistance (PIR), gastric fluid volume, preoperative discomfort, and variables of organ dysfunction in ASA physical status III-IV patients undergoing elective cardiac surgery, including those with noninsulin-dependent Type-2 diabetes mellitus. Before surgery, 188 patients were randomized to receive a clear 12.5% carbohydrate drink (CHO), flavored water (placebo), or to fast overnight (control). CHO and placebo were treated in double-blind format and received 800 mL of the corresponding beverage in the evening and 400 mL 2 h before surgery. Patients were monitored from induction of general anesthesia until 24 h postoperatively. Exogenous insulin requirements to control blood glucose levels <or=10.0 mmol/L were used as a marker for PIR. Gastric fluid volume was measured by passive gastric reflux and preoperative discomfort using visual analog scales. Postoperative clinical and surgical data were recorded. Blood glucose levels and insulin requirements did not differ between groups. Patients receiving CHO and placebo were less thirsty compared with controls (P < 0.01 and P = 0.06, respectively). Ingested liquids did not cause increased gastric fluid volume or other adverse events. The CHO group required less intraoperative inotropic support after initiation of cardiopulmonary bypass weaning (P < 0.05). In conclusion, preoperative CHO administration before cardiac surgery does not affect PIR. Clear fluids reduce thirst and may be recommended as a safe procedure in ASA III-IV patients. Further research is indicated to investigate possible cardioprotective effects of preoperative CHO intake.

Enteral nutrition in critically ill patients with severe hemodynamic failure after cardiopulmonary bypass

BACKGROUND & AIMS

The study was designed to investigate and quantify nutritional support, and particularly enteral nutrition (EN), in critically ill patients with severe hemodynamic failure.

METHODS

Prospective, descriptive study in a surgical intensive care unit (ICU) in a university teaching hospital: patients aged 67+/-13 yrs (mean+/-SD) admitted after cardiac surgery with extracorporeal circulation, staying 5 days in the ICU with acute cardiovascular failure. Severity of disease was assessed with SAPS II, and SOFA scores. Variables were energy delivery and balance, nutrition route, vasopressor doses, and infectious complications. Artificial feeding delivered according to ICU protocol. EN was considered from day 2-3. Energy target was set 25 kcal/kg/day to be reached stepwise over 5 days.

RESULTS

Seventy out of 1114 consecutive patients were studied, aged 67+/-17 years, and staying 10+/-7 days in the ICU. Median SAPS II was 43. Nine patients died (13%). All patients had circulatory failure: 18 patients required intra-aortic balloon-pump support (IABP). Norepinephrine was required in 58 patients (83%). Forty patients required artificial nutrition. Energy delivery was very variable. There was no abdominal complication related to EN. As a mean, 1360+/-620 kcal/kg/day could be delivered enterally during the first 2 weeks, corresponding to 70+/-35% of energy target. Enteral nutrient delivery was negatively influenced by increasing dopamine and norepinephrine doses, but not by the use of IABP.

CONCLUSION

EN is possible in the majority of patients with severe hemodynamic failure, but usually results in hypocaloric feeding. EN should be considered in patients with careful abdominal and energy monitoring.

Adhesion molecules, catecholamines and leucocyte redistribution during and following exercise

The circulating blood normally contains no more than 1-2% of the body's population of leucocytes. The numbers and phenotypes of circulating leucocyte subsets can change dramatically during and immediately following exercise. The surface expression of adhesion molecules makes an important contribution to such responses by changing patterns of cell trafficking. Alterations in the surface expression of adhesion molecules could reflect a shedding of molecules, selective apoptosis or differential trafficking of cells with a particular phenotype, effects from mechanical deformation of the cytoplasm, active biochemical processes involving cytokines, catecholamines, glucocorticoids or other hormones, or changes in the induction of adhesion molecules. The expression of adhesion molecules changes with maturation and activation of leucocytes. Typically, mature cells express lower densities of L-selectin (CD62L), the homing receptor for secondary lymphoid organs, and higher densities of LFA-1 (CD11a), the molecule associated with trafficking to non-lymphoid reservoir sites. The neutrophils and natural killer cells that are mobilised during exercise also express high levels of Mac-1 (CD11b), a marker associated with cellular activation. Possibly, exercise demarginates older cells that are awaiting destruction in the spleen. Plasma concentrations of catecholamines rise dramatically with exercise, and there is growing evidence that catecholamines, acting through a cyclic adenosine monophosphate second messenger system, play an important role in modifying the surface expression of adhesion molecules. Analogous changes can be induced by other forms of stress that release catecholamines or by catecholamine infusion, and responses are blocked by beta(2)-blocking agents. Catecholamines also modify adherence and expression of adhesion molecules in vitro. Cell trafficking is modified by genetic deficiencies in the expression of adhesion molecules, but leucocyte responses to exercise and catecholamines are generally unaffected by splenectomy. A number of clinical conditions including atherogenesis and metaplasia are marked by an altered expression of adhesion molecules. The effects of exercise on these molecules could thus have important health implications.

Changes in the IGF-IGFBP axis in critical illness

In critical illness, serum concentrations of the growth hormone-dependent complexes containing insulin-like growth factors I and II are decreased. This is initially due to a transient growth hormone resistance, but in the longer term, the less pulsatile pattern of growth hormone secretion may be a major factor since only pulsatile growth hormone increases the levels of insulin-like growth factor-I and the acid-labile subunit. Other factors contributing to a low insulin-like growth factor level are nutritional deficiency and the direct effects of inflammatory cytokines. The growth hormone-independent proteins IGFBP-2, IGFBP-4 and IGFBP-6 increase in critical illness, suggesting a redistribution of insulin-like growth factors from growth hormone-dependent ternary complexes with IGFBP-3 and IGFBP-5 to binary complexes with these binding proteins, which might facilitate transport to the tissues. IGFBP-1, which is acutely regulated by metabolic status, is elevated on admission to intensive care but may fall in response to nutritional support. Initial evidence suggests that the level of IGFBP-1 may be predictive of outcome in critically ill patients, suggesting a possible prognostic role for this protein.