Carbohydrate and lipid metabolism in open-heart surgery

The effect on intermediary metabolism of open-heart surgery with deep hypothermia and circulatory arrest in infants of less than 10 kilograms body weight. A preliminary study

The effects of hypothermic open-heart surgery with circulatory arrest upon intermediary metabolism and endocrine function in small children are still poorly understood. This report presents data obtained in a preliminary study in which seven children of <10 Kg body weight were investigated during and after such procedures. Frequent blood samples were taken from one day preoperatively to seven days postoperatively for estimation of hormone concentrations (insulin, growth hormone, glucagon, cortisol), and intermediary metabolites (glucose, lactate, pyruvate, alanine, glycerol, and 3- hydroxybutyrate).

Marked hyperglycaemia (34·8 ±3·3 mmol/L) was observed during cardiopulmonary bypass probably as a result of the glucose content of the pump prime. Moderate hyperglycaemia persisted for at least seven days postoperatively. A significant increase in lactate concentrations (p < 0·02) was observed during circulatory arrest and peak concentrations of 6·77 +0.87 mmol/L were measured at the end of the operation. Very high blood lactate concentrations were observed at the end of cardiopulmonary bypass in two patients who subsequently died. Peak insulin concentrations (20·7 ± 5·2 mU/L) were lower than those (30-40 mU/L) reported in adults undergoing similar procedures. Glucagon concentrations were significantly elevated during bypass ( p<0·05) to approximately twice the levels reported in adults. Unlike the other hormones, growth hormone concentrations revealed remarkably uniform change, similar to those reported in 'high responding' adults with peak values of 124 ± 26 mU/L, observed during cardiopulmonary bypass. Cortisol concentrations showed no significant changes throughout the study.

Thus, the response of small infants to these procedures differed both qualitatively and quantitatively from that reported in adults. The results suggest that the nature of the prime fluid may be of major importance in the metabolic consequences of such surgery and that glucose and lactate may be better avoided in the pump prime.

Effects of Propofol and Midazolam on Lipids, Glucose, and Plasma Osmolality during and in the Early Postoperative Period Following Coronary Artery Bypass Graft Surgery: A Randomized Trial

It is not clear how levels of serum lipids and glucose and plasma osmolality change during propofol infusion in the pre- and postoperative period of coronary artery bypass graft surgery (CABG). This prospective, randomized, controlled trial evaluated changes in these parameters during propofol or midazolam infusion during and in the early postoperative period following surgery. Twenty patients undergoing CABG were randomized preoperatively into two groups: 10 patients received propofol (induction 1.5 mg/kg, maintenance 1.5 mg kg(-1) h(-1)) and 10 patients received midazolam (induction 0.5 mg/kg, maintenance 0.1 mg kg(-1) h(-1)). Both groups also received fentanyl (induction 20 mug/kg, maintenance 10 microg kg(-1)). Serum lipids, glucose, and plasma osmolality were measured preinduction, precardiopulmonary bypass, at the end of cardiopulmonary bypass, at the end of surgery, and 4 and 24 h postoperatively. In the propofol group, we observed a significant increase in triglycerides and very low-density lipoprotein levels 4 h postoperatively. In the midazolam group, we observed a significant decrease in low-density lipoprotein, cholesterol at the end of cardiopulmonary bypass, end of surgery, and 4 and 24 h postoperatively and significant increase in osmolality at the end of cardiovascular bypass. Changes in glucose levels did not differ significantly different between the two groups. In patients with normal serum lipids, glucose, and plasma osmolality undergoing CABG, propofol infusion for maintenance anesthesia is not associated with dangerous changes in serum lipids, glucose, and plasma osmolality compared with midazolam. A propofol infusion technique for maintenance of anesthesia for cardiac surgery where serum lipids and glucose may be of concern could be recommended as an alternative to midazolam.

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.

Myocardial metabolism and efficiency after warm continuous blood cardioplegia

BACKGROUND

Warm continuous blood cardioplegia (WCBCP) has been recommended during prolonged cardiac arrest to minimize functional deterioration. Myocardial metabolism and efficiency after this cardioplegic modality are not well described.

METHODS

Substrate oxidation, blood flow, and myocardial function were measured before, during, and after 3 hours of WCBCP in 7 pigs.

RESULTS

Free fatty acid and glucose oxidation decreased by 60% +/- 3.8% and 94% +/- 1.2%, respectively, during cardioplegia (both p < 0.05) and increased to 62% +/- 28% and 122% +/- 62% of baseline during the early recovery phase (p < 0.05 for glucose). One hour after WCBCP oxidation rates were similar to baseline. The transient postcardioplegic increase in substrate oxidation was associated with a 43% +/- 23% elevation of oxygen consumption (MVO2) compared with baseline and a 62% +/- 18% increase in myocardial blood flow. Cardiac output and mean arterial pressure did not change significantly after WCBCP, although myocardial function (stroke work, left ventricular end-systolic pressure, end-diastolic pressure, contractility, and efficiency) was depressed (p < 0.05). End-diastolic pressure and contractility improved from early to late phase of recovery, whereas the other indicators of ventricular function remained depressed.

CONCLUSIONS

Myocardial substrate oxidation was preserved after 3 hours of WCBCP, although ventricular function was moderately impaired. Thus, WCBCP with a seemingly normal substrate and oxygen supply was associated with a reduced cardiac efficiency.

Hyperglycemia during normothermic cardiopulmonary bypass: the role of the kidney

BACKGROUND

Hyperglycemia commonly occurs during cardiopulmonary bypass. We studied the quantitative impact of glucose input and its renal excretion on hyperglycemia during cardiopulmonary bypass.

METHODS

The quantity of glucose infused and metabolite and hormone concentrations in plasma, as well as oxygen consumption, carbon dioxide production, and renal glucose excretion, were determined before, during, and after cardiopulmonary bypass in 8 patients.

RESULTS

Hyperglycemia (14 to 29 mmol/L) was accompanied by an increase in plasma insulin levels. The degree of hyperglycemia was directly related to the amount of glucose infused. The rate of oxygen consumption did not decrease and the rate of urea appearance (gluconeogenesis) did not rise. Despite a very high filtered load of glucose, there was very little glucosuria, indicating a markedly enhanced renal absorption of glucose.

CONCLUSIONS

Hormonal and metabolic factors permit the development of hyperglycemia during cardiopulmonary bypass but its severity depends on the quantity of glucose infused and, what appears to be a new finding, a markedly enhanced renal reabsorption of filtered glucose. Thus the kidney plays an important role in the development of severe hyperglycemia during cardiopulmonary bypass.

Serum lipid and glucose concentrations with a propofol infusion for cardiac surgery

OBJECTIVE

To document changes in serum lipids and glucose with a propofol infusion technique for cardiac surgery.

DESIGN

Prospective cohort.

SETTING

University teaching hospital.

PARTICIPANTS

22 elective cardiac surgical patients.

INTERVENTIONS

Frequent venous blood sampling.

MEASUREMENTS AND MAIN RESULTS

Serum lipids and glucose were measured at 10 time periods perioperatively, from preinduction until 4 hours post-cardiopulmonary bypass. Plasma propofol concentrations were also measured in 10 of these patients. There was a significant increase in glucose (P < 0.0005) and decreases in cholesterol (P < 0.0005), high-density lipoprotein (P = 0.004), and low-density lipoprotein (P < 0.0005); there was no significant change in triglycerides (P = 0.39). The propofol infusion resulted in acceptable plasma levels throughout the procedure and allowed early extubation in the intensive care unit, after a mean (SD) of 7.14 (5.9) hours. There was a strong correlation between triglyceride and propofol levels at most time periods (r = 0.38 to 0.98).

CONCLUSIONS

This study demonstrates that a propofol infusion technique does not result in elevation of serum lipids and supports its increased popularity in maintenance of anesthesia for cardiac surgery.

Rationale for metabolic support with amino acids and glucose-insulin-potassium (GIK) in cardiac surgery

Myocardial metabolism and the current state of metabolic intervention under conditions relevant to cardiac surgery are reviewed. The rationale for metabolic support differs considerably in various settings of cardiac surgery. Although preventive measures are theoretically attractive, their use in the preoperative setting remains to be clarified. Amino acid enrichment of blood cardioplegia seems to be justified by an abundance of animal experimental data. In the postoperative setting of cardiac surgery, metabolic abnormalities may explain reversible myocardial dysfunction. Further, the combined effects of ischemia and the systemic neuroendocrine response to surgical trauma may adversely affect recovery. Amino acids, particularly glutamate, seem vital for metabolic recovery in this setting. Treating the relative shortage of glutamate occurring during this period by the administration of exogenous glutamate and counteracting the effects of the systemic neuroendocrine stress response by high-dose glucose-insulin-potassium are measures that have been shown to improve the metabolic state of the heart and subsequently myocardial performance.

Whole body oxygen consumption after hypothermic cardiopulmonary bypass

Whole body oxygen consumption and the substrate for energy production during the post-bypass period have not been clarified. We hypothesized that the substrate composition for energy production during post-bypass period might be different from that during pre-bypass period because of surgical diabetic state induced by hypothermic cardiopulmonary bypass (CPB). We measured whole body oxygen consumption, carbon dioxide production and respiratory quotient by the gas exchange method using the Datex Deltatrac before and after hypothermic cardiopulmonary bypass. We also measured oxygen consumption by Fick's principle. Whole body oxygen consumption (P < 0.001) and carbon dioxide production (P < 0.05) increased significantly above pre-CPB values after the termination of CPB. Respiratory quotient (P < 0.01) decreased significantly below pre-CPB values after the termination of CPB. We conclude that oxygen consumption increased significantly above pre-bypass values after the termination of hypothermic cardiopulmonary bypass at least under the fentanyl, diazepam, chlorpromazine anesthesia with continuous infusion of nitroglycerin and nicardipine. The changes in respiratory quotient suggest a relatively higher ratio of lipid metabolism for energy production during post-bypass period.

Glucose homeostasis. Comparison between hypothermic and normothermic cardiopulmonary bypass

STUDY OBJECTIVE

Disturbance in blood glucose homeostasis during cardiac surgery may cause visceral and metabolic alterations. Hypothermic CPB induces glucose and hormonal changes. As normothermic CPB is used at some institutions, a comparison of blood glucose and plasma hormones between hypothermic and normothermic CPB was performed.

DESIGN

Prospective nonrandomized study.

SETTING

University cardiac center.

PATIENTS

Twenty-two nondiabetic adults undergoing elective coronary bypass and/or valvular surgery.

INTERVENTIONS

Group 1 (n = 12) underwent hypothermic CPB (25 degrees C) and group 2 (n = 10) normothermic CPB (37 degrees C). In both groups nonpulsatile CPB was achieved with a membrane oxygenator and dextrose-free crystalloid priming. Dextrose was not administered during surgery but was infused postoperatively (125 mg/kg/h).

MEASUREMENTS AND RESULTS

Eight blood samples were drawn during the period of arrival in the operating room (control) to the third postoperative hour. During hypothermic CPB in group 1, blood glucose level increased to 154 +/- 20 mg/dl (mean +/- SD) associated with a decrease in plasma insulin and an increase in epinephrine, despite a decrease in cortisol and growth hormone. During rewarming, the blood glucose value continued to increase (to 197 +/- 35 mg/dl) associated with an increase in glucagon, growth hormone and catecholamines, despite a 374 percent increase in insulin. During CPB in group 2, insulin, glucagon, cortisol and catecholamines were significantly higher than during hypothermic CPB so that the blood glucose level was not significantly different between the two groups during CPB. Blood glucose value was higher in group 1 than in group 2 at closure of the chest (208 +/- 30 vs 175 +/- 19 mg/dl, respectively, p less than 0.02) and at the third postoperative hour (271 +/- 30 vs 221 +/- 51 mg/dl, p less than 0.01). In both groups, however, the postoperative increase in blood glucose was accompanied by a similar increase in insulin, cortisol and catecholamines but glucagon was lower after hypothermic CPB.

CONCLUSIONS

Hyperglycemia occurred perioperatively in cardiac surgery with dextrose-free priming both during hypothermic and normothermic CPB but normothermic CPB resulted in a slow and steady increase in both glucose and insulin concentrations without the major perturbations that occurred with hypothermic CPB. Postoperatively, higher blood glucose was observed in the hypothermic CPB group.

Preservation of pancreatic beta cell function with pulsatile cardiopulmonary bypass

Pancreatic islet cell function and tissue metabolism were studied during and after cardiopulmonary bypass in 38 patients undergoing an open heart operation. Twenty patients were operated on with pulsatile cardiopulmonary bypass (group I) and 18, with nonpulsatile cardiopulmonary bypass (group II). Hyperglycemia was observed during and early after operation in both groups. In group I during cardiopulmonary bypass, the immunoreactive insulin and c-peptide levels and the insulin to glucagon molar ratio increased significantly compared with the preoperative values, but in group II, these variables did not alter significantly. An hour postoperatively, the immunoreactive insulin (71 +/- 34 muIU/mL) and c-peptide (8.3 +/- 3.0 ng/mL) levels and the insulin to glucagon molar ratio (11.0 +/- 5.2) in group I were significantly higher than those in group II (immunoreactive insulin, 29 +/- 20 muIU/mL; c-peptide, 4.8 +/- 1.8 ng/mL; insulin to glucagon molar ratio, 3.4 +/- 2.6). The blood lactate level in group I (41 +/- 22 mg/dL) was significantly lower than that in group II (78 +/- 30 mg/dL) an hour postoperatively. In conclusion, pulsatile cardiopulmonary bypass is quite effective in preserving pancreatic beta cell function and tissue metabolism during and early after open heart procedures.

Albumin prevents erythrocyte crenation in patients undergoing extracorporeal circulation

Free fatty acid-induced massive erythrocyte crenation has been reported in patients undergoing extracorporeal circulation (EC), suggesting that the crenated cells impair microcirculatory flow and tissue oxygenation during and after the operation. Effect of albumin administration on erythrocyte crenation was examined in 18 patients undergoing coronary bypass operation: 9 patients were given 25 g and another 9 patients were given 50 g of human albumin as a part of the priming solution. Erythrocyte crenation was almost completely prevented in the patients given 50 g albumin. Crenated erythrocytes during EC were 3.6 +/- 2.3% (mean +/- SD) of all erythrocytes and 2.8 +/- 3.7% after EC. This was significantly lower than in patients without albumin administration (63.4 +/- 34.0% during EC and 28.6 +/- 33.3% after EC, n = 20). But the effect was less striking in the patients given 25 g albumin, 32.4 +/- 39.1% during and 28.3 +/- 40.8% after EC. Maintaining an adequate level of plasma albumin is important in preventing erythrocyte crenation during EC, improving microcirculatory flow in patients undergoing open heart surgery.

Hormonal and metabolic changes during hypothermic coronary artery bypass surgery in diabetic and non-diabetic subjects

Hormonal and metabolic responses to hypothermic coronary artery bypass grafting (CABG) were studied in three groups: 8 non-diabetic patients, 8 patients with non-insulin-dependent diabetes mellitus (NIDDM) given a glucose pump priming solution and 8 NIDDM patients given a non-glucose infusion. There were no significant differences in stress hormone responses between NIDDM and non-diabetic patients, with adrenaline concentrations rising 10-fold, noradrenaline 4-fold and cortisol 2 to 3-fold. Glucagon rose significantly during bypass only in the NIDDM patients who did not receive a glucose prime. Comparable marked hyperglycaemia was seen in both glucose primed groups during bypass and exclusion of glucose from the prime in NIDDM patients prevented this major rise. Postoperatively, the rise in insulin in the glucose primed NIDDM patients contrasted with the slower rise in the non-glucose primed NIDDM patients who were also hyperglycaemic by this stage. Perioperative hyperglycaemia in NIDDM patients undergoing CABG can be prevented by using a non-glucose priming solution and by giving insulin infusion, particularly postoperatively.

Erythrocyte crenation induced by free fatty acids in patients undergoing extracorporeal circulation

Normal erythrocyte morphology is necessary for proper distribution of blood-flow in the microcirculation. Erythrocyte shape was studied in 20 patients undergoing extracorporeal circulation (EC) during coronary bypass surgery. Crenated erythrocytes comprised a mean 64% of all erythrocytes during and 29% after EC. Free fatty acid (FFA) content of the erythrocyte membranes was significantly increased at both times, and FFA content correlated with the proportion of crenated erythrocytes. Washing crenated cells with defatted albumin solution transformed them back to discocytes, simultaneously removing more FFA than that removed from pre-EC discocytes. The plasma FFA to albumin ratio became disproportionately increased during EC; the increased level correlated with severity of erythrocyte crenation. Maintaining a higher level of albumin during EC by adding 50 g human albumin to the extracorporeal system prevented erythrocyte crenation. Entry of plasma FFA not bound to albumin into erythrocyte membranes during EC causes massive erythrocyte crenation.

Glucose and insulin changes in infants and children undergoing hypothermic open-heart surgery

Marked hyperglycemia was observed in patients undergoing hypothermic open-heart surgery. To evaluate potential mechanisms responsible for hyperglycemia, paired samples were evaluated for glucose and insulin levels in 3 groups of patients. Group 1 consisted of 8 patients less than 2 years of age undergoing cardiac surgery requiring total circulatory arrest; Group 2 consisted of 9 patients less than 2 years of age undergoing open-heart procedures but not requiring total circulatory arrest; Group 3 consisted of 10 patients greater than 2 years of age, none of whom required total circulatory arrest. All 3 groups had striking hyperglycemia during cardiac surgery and in the first few hours after the operation. Despite elevated glucose levels during surgery, insulin levels failed to increase proportionately in response to hyperglycemic stimulus. Subsequently, in a fourth group of 10 patients less than 2 years of age not undergoing total circulatory arrest, the amount of glucose infused was restricted and they did not have hyperglycemia. In children, osmotic diuresis resulting from hyperglycemia after open-heart surgery may be misinterpreted as an index of satisfactory cardiorenal performance. Accordingly, it is recommended that the diluent added to the pump blood prime solution contain no supplemental glucose; also, intraoperative fluid should consist of a balanced electrolyte solution but no glucose.

Metabolic effect of glucose, insulin and potassium cardioplegia

Glucose-insulin-potassium (GIK) solution is widely used as a cardioplegic infusate for myocardial protection during aortic cross-clamping, to obtain rapid diastolic arrest and preservation of energy stores. Nine male patients with aorto-coronary bypass grafting procedure were studied with regard to the metabolic influence of GIK cardioplegia. Hyperglycemia was induced by the infusion of GIK solution for one week after surgery. The serum level of non-esterified fatty acid was high for one week while the triglyceride level was maintained at a high level only in the early post-operative period. Insulin, glucagon and growth hormone which influence carbohydrate and lipid metabolism were also elevated for one week after infusion of GIK solution. We conclude that the derangement of carbohydrate and lipid metabolism which is provoked by the use of GIK cardioplegia normalizes within two weeks after operation.

Inhibitory mechanisms of insulin secretion associated with hypothermic open-heart surgery

In order to clarify the inhibitory mechanism of insulin secretion associated with open-heart surgery, the influence of insulin antagonistic hormones on insulin secretion was studied in 20 patients with congenital heart diseases undergoing open-heart surgery, under simple deep hypothermia. Despite a hyperglycemia, plasma immunoreactive insulin and C-peptide showed no change during the cooling period, while with the exception of plasma human growth hormone, dopamine-beta-hydroxylase, immunoreactive glucagon, cortisol and cyclic AMP in plasma, either showed no change, or a decrease during the cooling period. It is assumed that catecholamine, glucocorticoid and glucagon do not play an important role in the inhibitory mechanism of insulin secretion during hypothermic open-heart surgery, and a transient hypofunction of the pancreas as well as the liver and the adrenal gland is probably involved.

Influence of morphine anaesthesia on the endocrine-metabolic response to open-heart surgery

Twelve patients scheduled for aortic valve replacement during extracorporal circulation were randomly allocated to either morphine anaesthesia or fluroxene anaesthesia. Morphine in a total dose of 4 mg/kg was administered before skin incision. At the start of extracorporal circulation all patients received 25 g glucose intravascularly. The endocrine-metabolic response to surgery, as expressed by changes in plasma ACTH, cortisol, insulin, growth hormone, cyclic adenosine-3',-5'-monophosphate (cyclic AMP), glucose, free fatty acids, blood b-hydroxybutyrate and cumulative nitrogen balance was measured before and during anaesthesia and surgery, and on the first five post-operative days. It was found that morphine anaesthesia blocked the increase in ACTH, cortisol, growth hormone, cyclic AMP, and glucose during surgery. However, after initiation of extracorporal circulation only ACTH, cortisol, and, to a lesser degree, the glucose and insulin response to glucose were lowered by morphine anaesthesia. From the first to the fifth days after operation no differences between the two groups could be demonstrated in any parameter. Cumulative nitrogen balance was similar in the two groups. It is concluded that morphine in large doses administered before skin incision inhibits the initial endocrine-metabolic response to open-heart surgery, but that the effect is short-lasting and without effect on overall postoperative protein catabolism.