Renal effects of amino acid infusion in cardiac surgery.

OBJECTIVE: To evaluate effects of amino acids on renal function and oxygen consumption and the role of individual amino acids on renal blood flow (RBF) changes. DESIGN: Prospective, randomized, controlled study. SETTING: Operating room in cardiothoracic surgery department, university hospital. PARTICIPANTS: Twenty-two male patients submitted to elective first-time coronary artery bypass surgery. INTERVENTIONS: A catheter was placed in the left renal vein for thermodilution RBF measurements and blood sampling. In 11 patients, a balanced mixed amino acid infusion was infused (200 mL/hr) for 30 minutes immediately after the operation. MEASUREMENTS AND MAIN RESULTS: RBF and glomerular filtration rate increased during amino acid infusion compared with the control group. Renal oxygen consumption increased in the amino acid group and correlated with the increase in RBF (r = 0.70, p<0.001). Amino acid infusion induced two- to fourfold increases in plasma concentrations of individual amino acid concentrations and promoted renal extraction of aspartate, glutamate, glycine, and histidine. No correlation was observed between arterial concentration or uptake of individual amino acids and RBF. CONCLUSIONS: The increase in RBF from a mixed amino acid infusion was associated with increased glomerular filtration rate and renal consumption of oxygen. Changes in RBF of a mixed amino acid infusion could not be linked to plasma level or renal uptake of any individual amino acids.

Renal effects of alpha-ketoglutarate early after coronary operations.

BACKGROUND: Alpha-ketoglutarate (alpha-KG) is a Krebs cycle intermediate and the carbon skeleton of glutamate. Alpha-ketoglutarate has provoked interest in heart surgery because of its proposed critical role in myocardial metabolism. This study investigates the role of alpha-KG in renal function after cardiac surgical procedures. METHODS: Twenty-two patients with normal preoperative renal function were included in a prospective, randomized, and controlled study. Eleven patients received intravenous infusion of 30 g alpha-KG/hour after the operation. Measurements were performed before operation, immediately after operation, and after 30 minutes of alpha-KG infusion. RESULTS: Renal blood flow was higher during alpha-KG infusion, 297% +/- 97% (of preoperative value), than in controls, 125% +/- 20% (p < 0.05). Filtration fraction was lower (12.3% +/- 0.05% versus 17.2% +/- 1.1%, p < 0.01), which prevented a significant difference in glomerular filtration rate. The renal arteriovenous differences of lactate, glutamate, glutamine, and glycine changed toward a net release during alpha-KG infusion. CONCLUSIONS: Infusion of alpha-KG enhances renal blood flow early after coronary surgical procedures in patients with normal renal function. The mechanism is unclear, but could be associated with primarily metabolic effects, and may potentially convey a beneficial effect for renal function.

Insulin and amino acid infusion after cardiac operations: effects on systemic and renal perfusion.

OBJECTIVE: The purpose of this study was to answer two questions: (1) Does a mixed amino acid infusion enhance systemic and renal perfusion in the early postoperative period after heart operations? (2) Does the addition of insulin (glucose-insulin-potassium solution) provide additional effects to those of an amino acid infusion? METHODS: Thirty-three male patients undergoing coronary artery bypass grafting (mean age 65.9 +/- 1.2 years) were included in a prospective, controlled, randomized study. Eleven patients (AA group) received infusion of mixed amino acids (11.4 gm), 11 patients (AA + GIK group) received infusion of mixed amino acids (11.4 gm) and insulin solution (225 IU insulin, glucose with glucose clamp technique, and potassium), and 11 patients served as control subjects. RESULTS: Amino acid infusion alone had no effect on systemic vascular resistance or cardiac index but increased renal blood flow 51% +/- 11% (from 114 +/- 13 to 172 +/- 24 ml.min-1.m-2 in one kidney, p < 0.05 vs the control group). Insulin solution in addition to amino acid infusion reduced systemic vascular resistance 24% +/- 3% (from 1280 +/- 85 to 960 +/- 57 dyn.sec.cm-5, p < 0.05 vs the control and AA groups) and increased cardiac index 13% +/- 3% (from 2.3 +/- 0.2 to 2.6 +/- 0.2 L.min-1.m-2, p < 0.05 vs the control and AA groups). Insulin had no significant additive effect on renal blood flow. CONCLUSIONS: Our data imply that (1) infusion of mixed amino acids enhances renal blood flow after cardiac operations but has no effect on systemic perfusion and (2) the addition of insulin solution improves systemic perfusion. The combined treatment may potentially reduce the risk of renal hypoperfusion injury in the postoperative period after coronary artery bypass grafting.

Effects of prostacyclin on myocardial hemodynamics and metabolism after coronary artery bypass grafting.

OBJECTIVE: To study the effects of incremental infusion rates of prostacyclin on myocardial blood flow and metabolism and central hemodynamics shortly after coronary artery bypass grafting. DESIGN: A pharmacodynamic dose-response study. SETTING: A multi-institutional university hospital. PARTICIPANTS: Twelve patients with two- or three-vessel coronary artery disease and with an ejection fraction greater than 0.5 were studied in the operating room after sternal closure and elective coronary artery bypass grafting. INTERVENTIONS: Prostacyclin was administered at infusion rates of 2.5, 5, 10, and 20 ng/kg/min. Systemic and pulmonary hemodynamics and global (coronary sinus) as well as regional (great cardiac vein) myocardial blood flow and metabolic variables were measured. MEASUREMENTS AND MAIN RESULTS: Infusion rates of 10 and 20 ng/kg/min decreased mean arterial blood pressure (13% and 21%, respectively), systemic vascular resistance (31% and 42%), and pulmonary vascular resistance (11% and 33%), increased cardiac output (28% and 37%), heart rate (9% and 13%), and stroke volume (15% and 20%), but had no effect on central filling pressures. Prostacyclin caused no changes in great cardiac vein flow or coronary sinus flow. Furthermore, prostacyclin caused no changes in regional myocardial oxygen extraction, indicating that prostacyclin did not induce direct coronary vasodilation. There were no electrocardiographic or obvious metabolic signs of myocardial ischemia during prostacyclin infusion. CONCLUSION: Prostacyclin may be a useful afterload-reducing compound after coronary artery bypass grafting because it has no direct coronary vasodilatory effect, which minimizes the risk of myocardial ischemia.

The effects of nitrous oxide on left ventricular systolic and diastolic performance before and after cardiopulmonary bypass: evaluation by computer-assisted two-dimensional and Doppler echocardiography in patients undergoing coronary artery surgery.

We investigated the effects of nitrous oxide (N2O) on central hemodynamics and left ventricular systolic and diastolic function in 25 patients undergoing coronary artery bypass surgery. All patients were receiving beta-blockers and had good left ventricular function. Global and regional systolic left ventricular performance and diastolic function were determined by computer-assisted analysis of transesophageal echocardiographic (TEE) images, and mitral Doppler flow profiles, respectively. The patients were anesthetized with fentanyl and ventilated with oxygen in air. Hemodynamic and TEE measurements were obtained before and after the introduction of N2O in oxygen (60%/40%), before and after cardiopulmonary bypass (CPB). N2O reduced mean arterial pressure, heart rate, stroke volume, and cardiac output both before and after CPB. Left ventricular global area ejection fraction (GAEF) was not changed by the introduction of N2O, either before or after CPB. N2O induced a significant change in regional wall motion after, but not before CPB, as assessed by the relationship between segmental area ejection fraction (SAEF) and GAEF. Analysis of the mitral flow profile indicated an increase in early diastolic relaxation in the pre-CPB period after introduction of N2O, that was absent in the post-CPB period. We conclude that N2O induces regional wall motion abnormalities and possibly diastolic dysfunction post-CPB.

Effects of adenosine infusion on systolic and diastolic left ventricular function after coronary artery bypass surgery: evaluation by computer-assisted quantitative 2-D and Doppler echocardiography.

The effects of adenosine on central hemodynamics, ST-segment changes, and left ventricular (LV) systolic and diastolic function, determined by transesophageal 2-D and Doppler echocardiography, were investigated in 20 patients shortly after coronary surgery. After control measurements, adenosine was infused at incremental infusion rates (30, 60, and 120 micrograms.kg-1.min-1). Adenosine caused dose-dependent increases in heart rate (68.0 +/- 11.2-74.0 +/- 15.7 bpm), cardiac output (3.23 +/- 0.76-4.17 +/- 0.67 L/min), and stroke volume (48.8 +/- 12.5-56.7 L/min), and stroke volume (48.8 +/- 12.5-56.7 mL), decreases in arterial pressure (84.8 +/- 16.6-63.3 +/- 15.2 mm Hg), and systemic and pulmonary vascular resistances (1994 +/- 510-1106 +/- 309 and 209 +/- 54-116 +/- 58 dyne.s.cm-5, respectively), but no changes in cardiac filling pressures. The mean ST segment was slightly but significantly depressed by adenosine (from 0.003 to 0.019 mV). Analysis of LV wall motion showed that adenosine caused no changes in the global area ejection fraction (GAEF), the segmental area ejection fraction (SAEF), or in the SAEF/GAEF ratio, indicating that no regional wall motion abnormalities appeared. Maximum early and late diastolic flow rates (Emax, Amax), determined by mitral Doppler analysis, increased (from 30.1 +/- 14.8 to 40.1 +/- 24.1 and from 37.8 +/- 15.7 to 46.4 +/- 31.3 cm/s, respectively), as did the deceleration slope of the early diastolic filling (from -151 +/- 67 to -210 +/- 107 cm/s-2), whereas no changes were found in the ratio between Emax and Amax, the deceleration time of early diastolic filling, or the velocity time integrals of early or late diastolic filling.(ABSTRACT TRUNCATED AT 250 WORDS)

Thoracic epidural anesthesia during coronary artery bypass surgery: effects on cardiac sympathetic activity, myocardial blood flow and metabolism, and central hemodynamics.

The effects of high thoracic epidural anesthesia (TEA) on cardiac sympathetic nerve activity, myocardial blood flow and metabolism, and central hemodynamics were studied in 20 patients undergoing coronary artery bypass grafting (CABG). In 10 of the patients, TEA (T1-5 block) was used as an adjunct to a standardized fentanyl-nitrous oxide anesthesia. Hemodynamic measurements and blood sampling were performed after induction of anesthesia but prior to skin incision and after sternotomy. Assessment of total and cardiac sympathetic activity was performed by means of the norepinephrine kinetic approach. Prior to surgery, mean arterial pressure (MAP), great cardiac vein flow (GCVF), and regional myocardial oxygen consumption (Reg-MVO2) were lower in the TEA group compared to the control group. During sternotomy there was a pronounced increase in cardiac norepinephrine spillover, MAP, systemic vascular resistance index (SVRI), pulmonary capillary wedge pressure (PCWP), GCVF, and Reg-MVO2 in the control group. These changes were clearly attenuated in the TEA group. None of the patients in the TEA group had metabolic (lactate) or electrocardiographic signs of myocardial ischemia. Three patients in the control group had indices of myocardial ischemia prior to and/or during surgery. We conclude that TEA attenuates the surgically mediated sympathetic stress response to sternotomy, thereby preventing the increase in myocardial oxygen demand in the pre-bypass period without jeopardizing myocardial perfusion.

Central hemodynamics and right ventricular function after coronary artery bypass surgery. A comparison of prostacyclin, sodium nitroprusside, and nitroglycerin for treatment of postcardiac surgical hypertension.

The aim of this study was to compare the effects of prostacyclin on central hemodynamics and right ventricular function to the more widely used vasodilators sodium nitroprusside (SNP) and nitroglycerin (NTG), and to investigate whether prostacyclin is more selective to the pulmonary vascular bed compared to SNP and NTG after coronary artery bypass surgery. Twelve patients with two-vessel or three-vessel coronary artery disease and an ejection fraction > 0.5 were included. Hemodynamic measurements were made postoperatively in the intensive care unit using a pulmonary artery fast-response ejection fraction/volumetric thermodilution catheter. The aim was to control and maintain mean arterial blood pressure around 75 to 80 mmHg with each drug. After a 10-minute infusion of each drug at a stable infusion rate, central hemodynamic variables as well as right ventricular end-diastolic volume (RVEDV), end-systolic volume (RVESV) and ejection fraction (RVEF) were measured or derived in triplicate. The average infusion rates of SNP, NTG, and prostacyclin were 2.3 +/- 0.8 micrograms/kg/min, 12.6 +/- 6.0 micrograms/kg/min and 20.0 +/- 0.5 ng/kg/min, respectively. Cardiac output, stroke volume, RVEDV, and central filling pressures were highest for prostacyclin compared to both NTG and SNP. Systemic vascular resistance (SVR) was lowest for prostacyclin but the effects on pulmonary vascular resistance (PVR) were comparable to that of SNP. The PVR/SVR ratio was significantly lower with both SNP and NTG when compared to prostacyclin. RVEF did not differ among the three drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of adenosine on renal function and central hemodynamics after coronary artery bypass surgery.

In the early postoperative period after coronary artery bypass surgery, arterial hypertension commonly occurs which requires intravenous vasodilator therapy. Purine adenosine is a potent vasodilator and when exogenously administered it decreases systemic arterial blood pressure effectively. We evaluated the effects of adenosine on central hemodynamics and renal function when used to control postoperative hypertension after coronary artery bypass grafting (CABG). Two separate series of experiments were performed postoperatively in the Intensive Care Unit (ICU). In the first study (n = 10), postoperative hypertension was controlled in the rewarming phase, with sodium nitroprusside (SNP, 1.7 +/- 0.4 micrograms.kg-1 x min-1) or adenosine (147.2 +/- 38.9 micrograms.kg-1 x min-1) to keep mean arterial systolic pressure at approximately 80 mm Hg. In the second study on a separate group of patients (n = 9), low doses of adenosine (0, 30, 60, 90, and 0 micrograms.kg-1 x min-1) were infused when the patients were normotensive and rewarmed. Central hemodynamics, urine flow (UF), renal blood flow (RBF), glomerular filtration rate (GFR), and ECG were evaluated during periods of 30 min for each drug in the first study and during each dose of adenosine in the second study. RBF and GFR were determined using standard urinary clearance methods for 51Cr-ethylenediaminetetraacetic acid and p-aminohippuric acid. In the first study, adenosine infusion, compared to SNP, decreased (A - V)O2, increased central filling pressures and heart rate, and caused a more pronounced ST segment depression. During adenosine administration RBF (-44%), GFR (-52%), and UF (-76%) decreased, while renal vascular resistance and filtration fraction (FF) were unaltered compared to data obtained during SNP infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasodilation with adenosine or sodium nitroprusside after coronary artery bypass surgery: a comparative study on myocardial blood flow and metabolism.

The effects of adenosine and sodium nitroprusside (SNP) on central hemodynamics and myocardial blood flow and metabolism were investigated postoperatively after elective coronary artery bypass (CABG) surgery in ten sedated and mechanically ventilated patients in the intensive care unit. During three consecutive 15-min periods, SNP (0.8 +/- 0.1 micrograms.kg-1 x min-1), adenosine (88.9 +/- 13.3 micrograms.kg-1 x min-1), and then again SNP (0.7 +/- 0.1 micrograms.kg-1 x min-1) were infused to control postoperative hypertension at a mean arterial pressure of approximately 80 mm Hg. Systemic and pulmonary hemodynamics and global (coronary sinus flow, CSF) as well as regional (great cardiac vein flow, GCVF) myocardial blood flow and metabolic variables were measured. During adenosine infusion, in comparison to SNP, heart rate was unchanged, stroke volume index and cardiac index increased (24% and 32%, respectively), and the systemic vascular resistance index decreased (-26%). Mean pulmonary arterial pressure (24%) as well as pulmonary capillary wedge pressure (27%) and central venous pressure (18%) were higher with adenosine compared to SNP. Adenosine also increased CSF and GCVF (108% and 103%, respectively) without altering the CSF/GCVF flow ratio compared to SNP. Furthermore, adenosine increased the coronary oxygen content (51%) and decreased the arterio-great cardiac vein oxygen content difference (-48%) without changing regional myocardial oxygen consumption, indicating a more pronounced hyperkinetic myocardial circulation compared to SNP. In addition, adenosine infusion decreased arterial PO2 (-11%) and increased the intrapulmonary shunt fraction (57%). The PR interval time of the electrocardiogram was prolonged (12%) and the ST segment was more depressed during adenosine infusion compared to SNP.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial circulatory and metabolic effects of halothane when used to control intraoperative hypertension in patients with coronary artery disease.

The effect of halothane on regional myocardial metabolism and blood flow, when used as an adjunct to fentanyl-nitrous oxide anaesthesia, to treat intraoperative hypertension was investigated. Fifteen patients with two- or three-vessel coronary artery disease with an ejection-fraction greater than 0.5 and on beta-blockers up to the morning of surgery were studied during elective coronary artery by-pass grafting. Systemic and pulmonary haemodynamics, global (coronary sinus, CSF) and regional (great cardiac vein, GCVF) myocardial blood flow were measured. Measurements were made: 1) after induction of anaesthesia but prior to skin incision, 2) during sternotomy, and 3) during halothane administration after its use to reduce arterial pressure to the pre-sternotomy level. The increase in systemic arterial pressure during sternotomy was due to an increase in systemic vascular resistance index (SVRI), and was accompanied by an increase in pulmonary capillary wedge pressure (PCWP), regional myocardial oxygen consumption and extraction, GCFV and CSF. Halothane reduced arterial blood pressure to pre-sternotomy levels within 7.1 +/- 0.6 min at an end-tidal concentration of 0.96 +/- 0.11%. Halothane caused a decrease in SVRI, total coronary vascular resistance, regional myocardial oxygen consumption and extraction, while cardiac index, heart rate and GCVF/CSF ratio remained unchanged. Mean regional myocardial lactate extraction was not affected by sternotomy or halothane. During halothane administration one patient developed regional myocardial lactate production which was not present during sternotomy. However, another two patients, who had regional myocardial lactate production during sternotomy, did not produce lactate or had less negative value of regional myocardial lactate extraction during halothane administration.

Effects of adenosine on myocardial blood flow and metabolism after coronary artery bypass surgery.

The effects of adenosine on myocardial blood flow and metabolism, central hemodynamics, and the intrapulmonary shunt fraction were investigated. Fourteen patients with two- or three-vessel coronary artery disease and with an ejection fraction greater than 0.5 were studied in the operating room following sternal closure after elective coronary artery bypass grafting. Systemic and pulmonary hemodynamics and global (coronary sinus), as well as regional myocardial blood flow (great cardiac vein flow), and metabolic variables were measured. Adenosine was given in infusion rates of 15, 30, 60, and 120 micrograms.kg-1.min-1. Infusion rates of 60 and 120 micrograms.kg-1.min-1 decreased mean arterial blood pressure (11% and 16%, respectively), systemic vascular resistance index (30% and 43%), and pulmonary vascular resistance index (24% and 31%), increased cardiac index (25% and 45%), heart rate (14% and 15%), and stroke volume index (9% and 25%), and had no effect on central filling pressures. These infusion rates doubled the intrapulmonary shunt fraction and decreased arterial O2 tension by 26%. Great cardiac vein flow and coronary sinus flow increased 60% with adenosine infusion of 30-60 micrograms.kg-1.min-1 and 120% with 120 micrograms.kg-1.min-1. The ratio of great cardiac vein flow to coronary sinus flow, regional myocardial oxygen consumption, and mean regional lactate extraction and uptake were not significantly altered by adenosine. Adenosine caused a significant depression of the ST segment at infusion rates of 60 and 120 micrograms.kg-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Trauma metabolism and the heart. Uptake of substrates and effects of insulin early after cardiac operations.

In a controlled, randomized study the myocardial uptake/release of individual free fatty acids, glucose, lactate, pyruvate, alanine, and glycerol was studied 1 hour after completion of coronary operations. The effects of insulin were evaluated by means of a hyperinsulinemic "clamp" technique. No significant uptake of free fatty acids was found despite markedly elevated arterial concentrations (mean +/- standard error of the mean, 2.01 +/- 0.19 mmol.L-1), oleic acid, together with palmitic and linoleic acid, constituting 80% of the total plasma free fatty acid level. Insulin treatment (1 unit.kg bw-1.hr-1) prevented a further increase of the plasma free fatty acid level, observed concomitantly in the control group. Insulin affected all individual free fatty acids similarly. Changes in plasma free fatty acid levels occurring during the study and the corresponding myocardial uptake correlated (rS = 0.50 to 0.81). No significant uptake or release of glucose, lactate pyruvate, and glycerol occurred, whereas a myocardial release of alanine was seen. The heart and the concomitant leg uptake/release of glucose (rS = 0.40, p less than 0.05) and lactate (rS = 0.67, p less than 0.01) correlated. A substantial uptake of glucose was achieved and a more positive myocardial balance was obtained for alanine, lactate, and pyruvate with insulin. The changes in heart and the concomitant leg uptake/release correlated (glucose, rS = 0.62, p less than 0.01; lactate, rS = 0.64, p less than 0.01; pyruvate, rS = 0.71, p less than 0.01). It is concluded that the myocardial uptake of substrates during the first hours after coronary surgery is markedly abnormal with no uptake of free fatty acids or carbohydrates. These changes can be explained to some extent by the insulin resistance of trauma metabolism and can be modified by insulin treatment.

Trauma metabolism and the heart: studies of heart and leg amino acid flux after cardiac surgery.

Flux of plasma amino acids was measured across the heart and the leg (reflecting mainly skeletal muscle) in 18 patients 1 hour after completion of aorto-coronary bypass surgery. There was a net loss of amino acids from the leg (-324.9 +/- 39 nmol/min/100 ml tissue) while amino acid flux across the heart was not statistically different from zero. There were however positive intertissue correlations between leg and myocardial flux of tyrosine and most other amino acids, suggesting that protein metabolism of both tissues were affected in the same catabolic direction by the trauma response. Alanine and glutamine accounted for 50% of the amino acid release from the leg, which is in accordance with observations in association with other types of trauma. Alanine and glutamine also dominated amino acid release from the heart. Glutamate and aspartate were taken up by both tissues. The principal difference between the tissues was a myocardial uptake of leucine and isoleucine, in contrast to a leg release.

Control of intraoperative hypertension with isoflurane in patients with coronary artery disease: effects on regional myocardial blood flow and metabolism.

The effect of isoflurane on regional myocardial metabolism and blood flow, when used as an adjunct to fentanyl-nitrous oxide anesthesia, to control intraoperative hypertension was investigated. Twenty-two patients with two- or three-vessel coronary artery disease with an ejection fraction greater than 0.5 and on beta-blockers up to the morning of surgery were studied during elective coronary artery by-pass grafting. Systemic and pulmonary hemodynamics, and regional (great cardiac vein, GCVF) myocardial blood flow and myocardial metabolic parameters were measured. In 10 patients, both GCVF and global (coronary sinus, CSF) myocardial blood flows were recorded. Measurements were made 1) after induction of anesthesia but prior to skin incision, 2) during sternotomy, and 3) during isoflurane administration after its use to reduce arterial pressure to the presternotomy level. The increase in systemic arterial pressure during sternotomy was due to an increase in systemic vascular resistance accompanied by increases in heart rate, pulmonary capillary wedge pressure, (PCWP) regional myocardial oxygen consumption and extraction, GCVF and total coronary vascular resistance. Isoflurane reduced systemic arterial pressure but not PCWP, to presternotomy levels within 6.9 +/- 0.7 minutes at an end-tidal concentration of 1.5 +/- 0.2%. Isoflurane induced a pronounced systemic and coronary vasodilatation and increases in cardiac index, heart rate and regional myocardial oxygen extraction while the GCVF/CSF ratio remained unchanged. While mean regional--MLE% values were not effected by sternotomy, in two patients myocardial lactate production was seen during sternotomy but not during isoflurane. In another two patients, isoflurane induced lactate production.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose and lactate balances in heart and leg after coronary surgery: influence of insulin infusion.

Glucose and lactate balances in leg (representing mainly skeletal muscle) and heart were studied 1 hour after aortocoronary bypass surgery and insulin treatment. Seventeen men were randomized to receive 25 U fast-acting insulin as a bolus injection, followed by continuous infusion of 1 U/kg b.w. for 1 hour, or to serve as controls. In the leg a small glucose uptake was found while the lactate balance was negative. During the study period the lactate release increased further in the control group. In the myocardium no significant extraction of glucose or lactate could be demonstrated. Insulin treatment resulted in a fivefold increment of leg glucose uptake and in significant myocardial glucose uptake. Myocardial lactate balance was also improved by insulin treatment, with fractional extraction increased from 6 to 21%. It is concluded that myocardial carbohydrate metabolism is restricted in the early period after cardiac surgery, and that this seems to result from insulin resistance induced by the surgical trauma.

The effect of insulin on the leg and splanchnic balance of glucose and gluconeogenic substrates after cardiac surgery.

The effect of insulin and glucose infusion on the leg and splanchnic balance of glucose and the gluconeogenic substrates lactate, pyruvate, alanine and glycerol was studied in 13 patients directly after cardiac surgery. Insulin was infused continuously at a rate of 1.0 Unit/kg/hr during 1 hour. Sixteen patients served as a control group and received no insulin and glucose infusion. A significant increase in arterial lactate concentration in both the control group (from 1.40 +/- 0.19 to 1.68 +/- 0.24 mmol/l p less than 0.01) and the insulin group (from 1.58 +/- 0.27 to 2.07 +/- 0.22 mmol/l, p less than 0.05) was observed. The arterial pyruvate concentration was significantly increased (from 0.075 +/- 0.019 to 0.105 +/- 0.021 mmol/l, p less than 0.01) and glycerol was significantly decreased (from 0.15 +/- 0.03 to 0.12 +/- 0.03 mmol/l, p less than 0.05) during the insulin and glucose infusion. The alanine concentration was unchanged in both groups. Insulin and glucose infusion was followed by an increased leg uptake of glucose (from 0.15 +/- 0.14 to 1.06 +/- 0.16 mmol/min/100 ml, p less than 0.05), and by a changed splanchnic glucose balance (from -8.2 +/- 2.8 to +4.0 +/- 1.2 mmol/kg/min, p less than 0.01). A net leg release and at the same time a net splanchnic uptake of all gluconeogenic substrates was observed. The insulin and glucose infusion did not significantly change either the splanchnic balance or the leg balance of the gluconeogenic substrates.

Splanchnic glucose balance and insulin resistance in the early postoperative phase of cardiac surgery.

The splanchnic balance of glucose was studied in the basal state and at three levels of "clamped" hyperinsulinemia (260 +/- 23, 510 +/- 59, 3875 +/- 367 mU/liter) in 24 patients (43-70 years of age), who had undergone coronary surgery about 1 hr previously. The splanchnic balance of glucose in the basal state was negative in all patients (-1.6 +/- 0.3 mg/kg/min) and was changed into a zero-balance within 30 min when 0.15 or 0.3 U/kg/hr of insulin was infused. At an insulin infusion rate of 1.0 U/kg/hr the net splanchnic glucose balance was turned into a significant positive balance of an average 0.9 +/- 0.3 mg/kg/min.