The effect of glutamate infusion on cardiac performance is independent of changes in metabolism in patients undergoing routine coronary artery bypass surgery.

In a double-blind randomized placebo-controlled study, the effects of intravenous glutamate infusion on myocardial haemodynamics and metabolism were studied in 22 patients undergoing routine coronary artery bypass graft (CABG) surgery. Immediately after aortic cross-clamp release, an intravenous infusion of a solution of glutamate (125 mmol x l(-1)) at a rate of 1.5 ml x h(-1) x kg(-1) was given over 1 h to 11 patients (G group). The other 11 patients received a placebo infusion (0.9% NaCl) (P group). Haemodynamic functions and rates of exchange of glucose, non-esterified fatty acids and lactic acid over the heart were measured before sternotomy (T1), 40 min after cross-clamp release (T2) and 4 h after cross-clamp release (T3). At T2, decreases were seen in comparison with T1 in systemic vascular resistance index, and increases were seen in cardiac index and coronary sinus flow. All of these changes were greater in the G group than in the P group (P<0.05). Myocardial glutamate consumption increased 2-fold after glutamate administration. No significant changes were observed in the myocardial utilization of glucose, lactate or non-esterified fatty acids between the P and the G groups at T1, T2 or T3. These data show that an intravenous glutamate infusion after routine CABG surgery significantly improved cardiac haemodynamic performance without direct effects on cardiac substrate metabolism. This suggests that a reduction of the afterload via a peripheral vasodilatory effect is the main mechanism leading to the observed changes in haemodynamics. Earlier claims that patients with post-operative cardiac failure show metabolic benefits from the glutamate infusion do not seem to apply to patients undergoing routine CABG surgery.

Myocardial substrate uptake and oxidation during and after routine cardiac surgery.

OBJECTIVE: This study was designed to clarify whether myocardial substrate uptake and oxidation change after a period of hypothermic cardioplegic arrest during coronary artery bypass grafting procedures. METHODS: In 30 patients arterial and coronary sinus blood was sampled and coronary sinus flow measurements were performed before and after sternotomy and 10 minutes, 20 minutes, 50 minutes, and 6 hours after release of the aortic crossclamp. Measurement of free fatty acids, lactate, glucose, oxygen content, and carbon dioxide content in arterial and coronary sinus blood allowed calculations of myocardial substrate use, respiratory quotients, and myocardial oxidation rates of carbohydrates and fat. RESULTS: Uptake of free fatty acids and lactate was significant throughout the study and did not change in association with release of the crossclamp. Free fatty acid and lactate uptake measured 6 +/- 4 micromol/min and 23 +/- 26 micromol/min, respectively, before crossclamping compared with 8 +/- 7 micromol/min and 19 +/- 21 micromol/min, respectively, after release of the clamp. Glucose uptake was significant only during the first hour after crossclamp release and increased from 7 +/- 50 to 28 +/- 34 micromol/L after crossclamp release. Myocardial oxygen consumption did not change significantly (0.5 +/- 0.2 mmol/L compared with 0.35 +/- 0.2 mmol/L) after release of the crossclamp. Myocardial oxygen extraction ratio decreased from 58% +/- 8% to 41% +/- 13% after crossclamp release. Respiratory quotient increased after crossclamp release (0.85 +/- 0. 2 compared with 1.00 +/- 0.2), which implies that carbohydrate oxidation increased at the expense of free fatty acid oxidation. CONCLUSION: We conclude that hypothermic cardioplegic arrest during coronary artery bypass graft operations is associated with a transiently increased uptake and oxidation of carbohydrates during the immediate reperfusion phase.

Glutamate metabolism of the heart during coronary artery bypass grafting.

Glutamate infusion has been shown to exert beneficial hemodynamic effects in patients with heart failure after cardiac surgery. To elucidate the underlying mechanism we studied the possibility that glutamate is a Krebs-cycle precursor in the human heart. Therefore [1-13C]glutamate was infused in order to show production of 13CO2 by the heart. In five patients a primed constant infusion of [1-13C]glutamate was started 2|h before the start of sampling from coronary sinus and arterial blood. Plasma concentrations of glutamate and glutamine were determined by high pressure liquid chromatography. Blood concentration of CO2 and enrichment of [1-13C]glutamate, [1-13C]glutamine and [1-13C]glutmaine and 13CO2 were measured by GC-IRMS. The results show that approximately 85% of [1-13C]glutamate taken up by the heart is released released as 13CO2. These results show that synthesis of Krebs-cycle intermediates is a major fate of the glutamate extracted by the human heart.

Streptococcus anginosus, Streptococcus constellatus and Streptococcus intermedius. Clinical relevance, hemolytic and serologic characteristics.

A collection of 518 "Streptococcus milleri" isolates recovered from clinical specimens was identified to the species level according to recently established criteria. Streptococcus anginosus was the most frequently isolated species (59.3%), followed by S constellatus (30.3%) and S intermedius (10.4%). One third (34%) of all isolates were beta-hemolytic. The majority of S anginosus isolates were nonhemolytic, carried Lancefield group F, or were nongroupable. Most of the S constellatus isolates were beta-hemolytic, as well as 16.6% of S intermedius strains. Streptococcus anginosus was recovered more often from the genital and urinary tracts and S constellatus was recovered from the thorax. Streptococcus intermedius was mostly found in the head and neck area, but was also isolated from the abdomen and the skin, bone, and soft tissue. Streptococcus intermedius and nonhemolytic isolates were recovered most often from abscess-related specimens.

Bacteremia involving the "Streptococcus milleri" group: analysis of 19 cases.

During a 3-year study period, 19 patients at the University Hospital of Maastricht developed bloodstream infections with species of the "Streptococcus milleri" group, for an incidence of 0.33 per 1,000 admissions. The patients' median age was 48 years; the male-to-female ratio was 2.8. Eleven patients (57.9%) had underlying diseases, among which malignancy was predominant. Local trauma to the mucosal barrier was an important risk factor. An associated site of infection was found most frequently in the abdominal and thoracic cavities (nine and five cases, respectively). Bacteremia was polymicrobial in four of 19 episodes. The 20 infecting S. milleri strains were identified to the species level; Streptococcus anginosus was the most prevalent (16 strains). Eight strains carried Lancefield group C. The isolates were sensitive to most antibiotics. Abscess formation was documented in nine cases (47.3%); repeated drainage procedures were required in half of these episodes. Mortality was high (five of 19 patients, or 26.3%).

Intervertebral infection caused by Streptococcus milleri. A case report.

Intervertebral infection caused by Streptococcus milleri is described in a 45-year-old man. Initially, a tuberculous infection was suspected; this diagnosis resulted in a considerable delay in correct diagnosis and treatment. The patient recovered well with combined medical-surgical treatment. Streptococcus milleri, a common inhabitant of the gastrointestinal tract, comprises a variety of strains implicated in deep-seated purulent infections. Although reports of this are rare, S. milleri can be the offending organism in intervertebral disk infections.