Plasma endotoxin levels and functions of peripheral granulocytes in surgical patients with respiratory distress syndrome

Modeling autonomic regulation of cardiac function and heart rate variability in human endotoxemia

Heart rate variability (HRV), the quantification of beat-to-beat variability, has been studied as a potential prognostic marker in inflammatory diseases such as sepsis. HRV normally reflects significant levels of variability in homeostasis, which can be lost under stress. Much effort has been placed in interpreting HRV from the perspective of quantitatively understanding how stressors alter HRV dynamics, but the molecular and cellular mechanisms that give rise to both homeostatic HRV and changes in HRV have received less focus. Here, we develop a mathematical model of human endotoxemia that incorporates the oscillatory signals giving rise to HRV and their signal transduction to the heart. Connections between processes at the cellular, molecular, and neural levels are quantitatively linked to HRV. Rhythmic signals representing autonomic oscillations and circadian rhythms converge to modulate the pattern of heartbeats, and the effects of these oscillators are diminished in the acute endotoxemia response. Based on the semimechanistic model developed herein, homeostatic and acute stress responses of HRV are studied in terms of these oscillatory signals. Understanding the loss of HRV in endotoxemia serves as a step toward understanding changes in HRV observed clinically through translational applications of systems biology based on the relationship between biological processes and clinical outcomes.

Evaluation of the effects of steroids on experimental septic lung injury

To evaluate the clinical usefulness of steroids for septic lung injury, we investigated the effects of methylprednisolone (MP) on this disorder using an experimental rat model of cecal ligation and puncture (CLP). While 92% of the rats that underwent CLP (CLP rats) died within 30 h, those given high-dose MP (30 mg/kg) just after the operation (CLP + MP rats) survived for a significantly longer period (p < 0.01). Concentrations of endotoxin (ET) in arterial blood were significantly higher in the CLP + MP rats than in the CLP rats, while those in the bronchoalveolar lavage fluid (BALF) were significantly lower. Alveolar macrophages (AM) obtained from the CLP rats (CLP-AM) generated more O2-than did AM from sham-operated rats (sham-AM) following stimulation. However, the administration of MP did not reduce the upregulated generation of O2-by CLP-AM. While CLP-AM produced less leukotriene (LT)B4 than did sham-AM following stimulation with A23187, the administration of MP further reduced LTB4 production. When AM were cultured with [3H]arachidonic acid (3H-AA), the uptake of the isotope and the 3H release were significantly less in CLP-AM than in sham-AM. The administration of MP did not cause recoveries in the uptake and release of 3H-AA by CLP-AM. Although the survival time of CLP rats was significantly prolonged and the translocation of ET into BALF was reduced by steroid administration, the steroid effects were not explained by those on altered AM function. The upregulated generation of O2- and reduced LTB4 production from CLP-AM were not reversed by the treatment of this drug.

Postcardiopulmonary bypass lung edema. A preventable complication?

Potential etiologic factors of postcardiopulmonary bypass (post-CPB) lung edema (LE) were investigated (phase 1 study). Further patient treatment was modified according to the results of phase 1 study and the influence that these changes had on the incidence of the complication was assessed (phase 2 study). In phase 1 study, among 100 patients who underwent coronary bypass graft surgery, prolonged assisted ventilation was required for severe LE in 7 cases, and 6 patients had a moderate form of LE. Patients who suffered from severe LE had left and right ventricular dysfunction and normal pulmonary vascular resistance. Three predictors of LE were evidenced by logistic regression analysis: number of bypass grafts completed with internal mammary arteries (p = 0.013), transfusions of blood collected in mobile units (p = 0.014), and the combination of a significant lesion of the left main stem and the right coronary artery at preoperative angiography (p = 0.040). In phase 2 study, a further group of 100 patients was treated differently by improving myocardial protection during surgery, achieving a higher rectal temperature at the end of CPB, and reducing the amount of transfusions. This resulted in only one case of LE (p < 0.001). In conclusion, the cases of post-CPB LE evidenced in our study were related to postoperative ventricular dysfunction and blood transfusions. Any means of improving postoperative hemodynamic stability and reducing the need for transfusions could thus prevent the latter complication.

The increase of low density subpopulations and CD10 (CALLA) negative neutrophils in severely infected patients

We investigated the changes in polymorphonuclear leukocyte (PMN) subpopulations that accompany severe bacterial infection and examined their usefulness as a parameter for assessing the severity of infection. The Percoll density gradient was used to fractionate neutrophils into subpopulations of high density (1.09-1.10), intermediate density (1.08-1.09), and low density (1.07-1.08) with the majority of neutrophils from normal volunteers being of high density. By contrast, neutrophils from infected patients were of intermediate or low density, while those from severely infected patients showed a high percentage of the low density fraction with functional changes in lower chemotactic and beta-gulcuronidase activity. When each density subpopulation in the normal blood neutrophils was tested, low density PMNs had the lowest chemotaxis and minimal beta-glucuronidase activity. These results indicate that the increase in low density PMNs in patients with severe infection clearly reflects the functional impairment of PMNs. Flow cytometric analysis demonstrated that the neutrophils from severely infected patients had an decrease in CD10 expression. The percentage of CD10 positive PMNs correlated well with the severity of infection and with the clinical course of the patients. Thus, we conclude that PMN-density and CD10 expression change during severe bacterial infection, and that the measurement of PMN-subpopulations may be used to complement the clinical assessment of the severity of infections.

Oxidative metabolism of circulating granulocytes in adult respiratory distress syndrome

Among the different mechanisms involved, polymorphonuclear leukocytes (PMNs) may play a central role in the pathogenesis of adult respiratory distress syndrome (ARDS). PMNs were evaluated in 15 patients with ARDS, in 21 at risk of developing ARDS (AR), and in 36 controls (C). Spontaneous and opsonized zymosan (OZ), phorbol myristate acetate (PMA), and F-Met-Leu-Phe (F-M-L-P)-stimulated oxygen radical production was measured by luminol- and lucigenin-enhanced chemiluminescence (CL). Spontaneous CL activity of PMNs from ARDS patients was significantly greater than that from the PMN control (luminol CL, 2.8 +/- 0.6 vs. 0.8 +/- 0.1 mV, p less than 0.001; lucigenin CL, 2.0 +/- 0.6 vs. 0.30 +/- 0.04 mV, p less than 0.001), and the CL value from AR patients (luminol CL, 1.3 +/- 0.2 mV, p less than 0.001 vs. C; lucigenin CL, 0.8 +/- 0.1 mV, p less than 0.001 vs. C) was found to be between the ARDS and C patients. The peak of PMA-stimulated CL occurred earlier and it was significantly higher in ARDS patients than in AR patients (p less than 0.05) and controls (p less than 0.001). When the CL response was elicited with F-M-L-P, no difference among the three groups was found. When stimulated with OZ, the peak CL generated by PMNs from ARDS patients was significantly depressed compared with controls (luminol CL, 26.7 +/- 1.8 vs. 40.9 +/- 2.3 mV, p less than 0.01; lucigenin CL, 5.0 +/- 0.4 vs. 7.4 +/- 0.5 mV, p less than 0.005) with a similar result being obtained from AR patients (luminol CL, 32.1 +/- 2.5 mV, p less than 0.01 vs. C). Plasma from ARDS and AR patients showed a defective opsonizing capacity, suggesting in vivo complement consumption in both patient groups. No correlation between the severity of hypoxemia, the cause of ARDS, the outcome, and the different PMN functions could be established. Our results are in agreement with a determinant role of PMNs in the development of ARDS. The opposite metabolic responses may explain both the pulmonary injury and the increased susceptibility to infections observed in patients at risk of or with ARDS.

Organ procurement for pulmonary transplantation

Selection of suitable donors is critical to the success of clinical pulmonary transplantation. Requirements for lung donors, management before explantation, and methods of preservation were reviewed for the 70 heart-lung, eight double-lung, and two single-lung transplantations performed at the University of Pittsburgh since 1982. Careful observation of trends of hyperoxygenation studies, chest roentgenograms, and Gram stain and culture results of tracheal secretions, as well as findings on bronchoscopy, can help identify which lungs not only have adequate function but are acceptable for transplantation. In spite of the rigid criteria used, 76% of tracheal cultures from donors deemed acceptable grew organisms. The presence of oropharyngeal flora has been shown to correlate with the development of early intrathoracic infections in the recipient. Prophylactic broad-spectrum antibiotic treatment of the donor is desirable to treat microbial contamination that could cause focal injury to the donor lung and predispose to infection in the recipient. Acceptance of less than ideal donors is ill-advised even though rejection of such donors conflicts with the current shortage of organs.

Endotoxaemia, pulmonary complications, and thrombocytopenia in liver transplantation

Plasma endotoxin was measured in 64 patients undergoing primary liver replacement. Endotoxin concentrations increased during the anhepatic phase of the operations, and remained high for several days. Although the severity of endotoxaemia did not correlate with duration of the anhepatic phase, there was a correlation between endotoxaemia and the need for perioperative platelet transfusions, ventilator dependency postoperatively, and one-month case-fatality.

Endotoxin release from neisseria meningitidis. Relationship between key bacterial characteristics and meningococcal disease

A method was established in order to measure total and filtrable (CF) endotoxin in cultures of Neisseria meningitidis strains. The Limulus lysate (LAL) test gave results which paralleled those of the standard rabbit pyrogen test and of gas chromatography (GLC), concerning detection of different CF endotoxin levels. Meningococci varied in their ability to produce CF endotoxin. Cultures of similar bacterial densities, whether with a high (E+) or a low (E-) release of endotoxin in CF, had both high yields of endotoxin in sonicated culture suspensions determined by the LAL test. GLC demonstrated only small differences in total LPS contents between E+ and E- strains. This suggests that strains with similar cell wall endotoxin contents may vary in CF endotoxin. Electron microscopy revealed that E+ strains presented a high number of free, outer cell wall fragments (blebs, tubuli, membranes and aggregates of such structures) in surroundings. Few such free, small structures were found around E- strains. The amount of CF endotoxin of E+ strains was in part a function of the number of colony forming units (CFU/ml), and generally followed the growth curve. Because of its moment of appearance, and also based on electron microscopy findings, CF endotoxin appeared mainly to be released from living bacteria. The CF level of endotoxin was low or not detected at all in cultures of E- strains although their cultures reached higher mean CFU-levels than the niveaus required for the detection of CF endotoxin in the E+ strains. The E+ property was strain dependent. Meningococci isolated from CSF or blood had a significantly higher proportion of E+ strains (88.2%) and a higher CF endotoxin titre (greater than or equal to 10(3); 34.5%), than isolates from carriers (32.3% and 10.8%, respectively) (p less than 0.001 and p less than 0.001, respectively). A high mean CFU/ml in cultures seemed to be more often associated with isolates from patients than from carriers, more often with the presence than abscence of capsular polysaccharide (p less than 0.05), and more often with the presence than absence of the E+ property (p = 0.002). E+ strains were mostly serogroupable (i.e. encapsulated), regardless of source of the isolate (99% case and 80% carrier isolates). In contrast, serogroupable bacteria were not necessarily E+ when isolated from carriers (54.8%). The serogroup most apt to cause disease tended to have the highest proportion of E+ strains and the highest level of CF endotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)