Hyperglycemia during cardiopulmonary bypass

Determinants of prolonged intensive care unit stay in patients after cardiac surgery: a prospective observational study

BACKGROUND

Prolonged intensive care unit (ICU) stay of patients after cardiac surgery has a major impact on overall cost and resource utilization. The aim of this study was to identify perioperative factors which prolong stay in ICU.

METHODS

All adult patients from a single, specialized cardiac center who were admitted to the ICU after cardiac surgery during a 2-month period were included. Demographic and clinical characteristics, comorbidities, preoperative use of drugs, intraoperative variables, and postoperative course were recorded. Hemodynamic and blood gas measurements were recorded at four time intervals during the first 24 postoperative hours. Routine hematologic and biochemical laboratory results were recorded preoperatively and in the first postoperative hours.

RESULTS

During the study period 145 adult patients underwent cardiac surgery: 65 (45%) underwent coronary artery bypass graft surgery, 38 (26%) valve surgery, 26 (18%) combined surgery and 16 (11%) other types of cardiac operation. Seventy nine (54%) patients had an ICU stay of less than 24 hours. Random forests analysis identified four variables that had a major impact on the length of stay (LOS) in ICU; these variables were subsequently entered in a logistic regression model: preoperative hemoglobin [odds ratio (OR) =0.68], duration of aortic clamping (OR =1.01) and ratio of arterial oxygen partial pressure to inspired oxygen fraction (PaO₂/FiO₂) (OR =0.99) and blood glucose during the first four postoperative hours (OR =1.02). ROC curve analysis showed an AUC =0.79, P<0.001, 95% CI: 0.71-0.86.

CONCLUSIONS

Low preoperative hemoglobin, prolonged aortic clamping time and low PaO₂/FiO₂ ratio and blood glucose measured within the first postoperative hours, were strongly related with prolonged LOS in ICU.

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.

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 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.

Inadequate blood glucose control is associated with in-hospital mortality and morbidity in diabetic and nondiabetic patients undergoing cardiac surgery

BACKGROUND

Derangement of glucose metabolism after surgery is not specific to patients with diabetes mellitus. We investigated the effect of different degrees of blood glucose control (BGC) on clinical outcomes after cardiac surgery.

METHODS AND RESULTS

We analyzed 8727 adults operated on between April 1996 and March 2004. The highest blood glucose level recorded over the first 60 hours postoperatively was used to classify patients as having good (<200 mg/dL), moderate (200 to 250 mg/dL), or poor (>250 mg/dL) BGC; 7547 patients (85%) had good, 905 (10%) had moderate, and 365 (4%) had poor BGC. Patients with inadequate BGC were more likely to present with advanced New York Heart Association class, congestive heart failure, hypertension, renal dysfunction, and ejection fraction <50% (P0<or=.001). We found that 52% of patients with poor, 31% with moderate, and 8% with good BGC had diabetes mellitus. Inadequate BGC, but not diabetes mellitus (P=0.79), was associated with in-hospital mortality (good, 1.8%; moderate, 4.2%; poor, 9.6%; adjusted odds ratio: poor versus good BGC, 3.90 [95% confidence interval, 2.47 to 6.15]; moderate versus good BGC, 1.68 [95% confidence interval, 1.25 to 2.25]). Inadequate BGC also was associated with postoperative myocardial infarction (eg, odds ratio, poor versus good BGC: 2.73 [95% confidence interval, 1.74 to 4.26]) and with pulmonary and renal complications in patients without known diabetes mellitus (eg, odds ratio, poor versus good BGC: 2.27 [95% confidence interval, 1.65 to 3.12] and 2.82 [95% confidence interval, 1.54 to 5.14] respectively).

CONCLUSIONS

More than 50% of patients with moderate to poor BGC after cardiac surgery were not previously identified as diabetic. Inadequate postoperative BGC is a predictor of in-hospital mortality and morbidity.

Perioperative blood glucose control during adult coronary artery bypass surgery

Coronary artery bypass graft (CABG) procedures are among the most frequently performed surgical procedures in the United States. People with cardiovascular disease who also have diabetes have a greater risk of poor outcomes after CABG procedures than patients who do not have diabetes. This literature review examines current information regarding perioperative blood glucose (BG) control. It emphasizes BG control in adults during the hypothermic period of cardiopulmonary bypass. Hyperglycemia, not the diagnosis of diabetes, significantly increases the risk of adverse clinical outcomes, longer hospitalizations, and increased health care costs.

Conventional approach to glucose management for diabetic patients undergoing coronary artery bypass surgery

Continuous insulin infusion was not an effective mode of treatment in maintaining safe blood glucose levels (<200 mg/dl) during the intraoperative period of diabetic patients requiring open-heart surgery. The two modifications investigated to gain better control of the blood glucose were a change in the base solution of the cardioplegia and the use of a sliding insulin scale. Fifty patients including Type I and Type II diabetics were selected for the purpose of this study. The patients were then randomly divided into two groups categorized by the type of cardioplegic solution administered and the mode of insulin treatment. Group I patients received a dextrose 5%-based cardioplegic solution and blood glucose was treated via continuous intravenous insulin infusion. Group II patients received normal saline 0.9%-based cardioplegic solution and blood glucose was treated via sliding scale. Blood glucose levels were monitored pre- and postcardiopulmonary bypass (CPB) and every 30 min while on CPB. Glucose values were analyzed by group t test. A p value of <0.05 was considered statistically significant. When comparing Group I (mean=258 mg/dl) with Group II (mean=158 mg/dl), there was a statistically significant difference between the glucose values at each of the time intervals when the glucose values were recorded. In conclusion, Group II maintained an acceptable blood glucose level (<200 mg/dl) throughout the entire intraoperative period, which suggests that the combination of the sliding insulin scale and modification of the base cardioplegic solution was an effective mode of treatment.

Hyperglycemia increases cerebral intracellular acidosis during circulatory arrest

Phosphorus 31 nuclear magnetic resonance spectroscopy was used to assess cerebral high-energy phosphate metabolism and intracellular pH in normoglycemic and hyperglycemic sheep during hypothermic circulatory arrest. Two groups of sheep (n = 8 per group) were placed in a 4.7-T magnet and cooled to 15 degrees C using cardiopulmonary bypass. Spectra were acquired before and during circulatory arrest and during reperfusion and rewarming. Intracellular pH and adenosine triphosphate levels decreased during circulatory arrest. Compared with the normoglycemic animals, the hyperglycemic group was significantly more acidotic with the greatest difference observed during the first 20 minutes of reperfusion (6.40 +/- 0.08 versus 6.08 +/- 0.06; p < 0.001). Intracellular pH returned to baseline after 30 minutes of reperfusion in the normoglycemic group but did not reach baseline until 1 hour of reperfusion in the hyperglycemic animals. Adenosine triphosphate levels were significantly higher in the hyperglycemic group during circulatory arrest. Repletion of adenosine triphosphate during reperfusion was similar for both groups. These results support the hypothesis that hyperglycemia during cerebral ischemia drives anaerobic glycolysis and thus leads to increased lactate production and an increase [corrected] in the intracellular acidosis normally associated with ischemia.

Hormonal and metabolic response to operative stress in the neonate

It is evident from this review that newborns, even those born prematurely, are capable of mounting an endocrine and metabolic response to operative stress. Unfortunately, many of the areas for which a relatively well-characterized response exists in adults are poorly documented in neonates. As is the case in adults, the response seems to be primarily catabolic in nature because the combined hormonal changes include an increased release of catabolic hormones such as catecholamines, glucagon, and corticosteroids coupled with a suppression of and peripheral resistance to the effects of the primary anabolic hormone, insulin.

Aneurysms of the basilar artery treated with circulatory arrest, hypothermia, and barbiturate cerebral protection

Complete circulatory arrest, deep hypothermia, and barbiturate cerebral protection are efficacious adjuncts in the surgical treatment of selected giant intracranial aneurysms. These techniques were utilized in seven patients, one with a large and six with giant basilar artery aneurysms; four had excellent results, one had a good result, one had a fair outcome, and one died. The rationale for the use of complete cardiac arrest with extracorporeal circulation, hypothermia, and barbiturate cerebral protection is outlined. The surgical and anesthetic considerations are reviewed. The perioperative morbidity and long-term results support the use of these techniques in selected patients with complex intracranial vascular lesions.

The management of insulin dependent diabetes during cardiopulmonary bypass and general surgery

Two groups of insulin dependent diabetic subjects have been studied: six undergoing general surgical procedures and six undergoing hypothermic cardiopulmonary bypass surgery for coronary artery vein grafting. Intravenous glucose insulin mixtures were infused from the onset of surgery in both groups of patients, supplying 0.4 units of insulin per gram of glucose per hour, and 0.6 units of insulin per gram of glucose per hour in general and cardiac surgical patients respectively. Postoperatively diabetes was controlled carefully with an insulin syringe pump regulated by venous blood glucose monitoring. In cardiac surgical patients far more insulin was required to control diabetes postoperatively than in the general surgery patients (at 1 hour 1.6 units, SEM 0.4 compared to 0.7 SEM 0.1, p less than 0.05; and at 4 hours 2.0 units SEM 0.3 compared to 0.8 units SEM 0.1, p less than 0.02). Five non-diabetic subjects who underwent surgery for coronary artery venous bypass grafting were also studied. They developed significant postoperative hyperglycaemia (5.0, SEM 0.2, mmol/litre pre-operatively, compared with 8.8, SEM 0.7, mmol/litre p less than 0.03 at 1 hour and 10.2, SEM 1.7, mmol/litre, p less than 0.02 at 4 hours after bypass terminated).

[Development of blood sugar and insulinemia in the first 12 postoperative hours. Effects of glucose and insulin intake]

Serum levels of glucose and insulin are studied during 12 hours in the early post-operative period after intra-abdominal surgery. Five groups of non diabetic patients are perfused with incremental doses of glucose, G. I: no glucose, G. II: 8,33 g . h-1 of glucose during 6 hours, G. III: 16,66 g . h-1 of glucose during 6 hours, G. IV: 16,66 g . h-1 of glucose with 20 mu insulin; G. V: 16,66 g . h-1 of glucose with 40 mu insulin. In all groups a significant rise in serum levels of glucose is observed (10,5-15,6 mmol . l-1). At the same time serum level of insulin remains unchanged except when insulin is infused. However exogenous insulin is unable to prevent the serum level of glucose to rise post-operatively.

A review of hypersomolar hyperglycemic nonketotic dehydration (HHND): etiology, pathophysiology and prevention during intravenous hyperalimentation

The records of 200 patients, nutritionally supported by synthetic means, were reviewed for evidence of clinical hyperosmolar hyperglycemic nonketotic dehydration (HHND). There was a 3% incidence of morbidity, with a single mortality. Laboratory values demonstrated a positive correlation between persistent glucosuria and HHND. The pathophysiology of HHND demonstrated a relative insulin lack with sufficient insulin to prevent lipolysis, but insufficient to prevent hyperglycemia, glucosuria and osmotic diuresis. The mechanism and management of the pseudodiabetes of stress is reviewed. It is concluded that HHND is an avoidable iatrogenic morbidity. Prevention of osmotic diuresis secondary to glucosuria and, therefore, prevention of HHND is achieved by providing exogenous insulin sufficient to prevent glucosuria.