M. Schywalsky

Coincidence of pro- and anti-inflammatory responses in the early phase of severe sepsis: Longitudinal study of mononuclear histocompatibility leukocyte antigen-DR expression, procalcitonin, C-reactive protein, and changes in T-cell subsets in septic and postoperative patients.

ObjectiveTo determine the time course of histocompatibility leukocyte antigen (HLA)-DR expression in peripheral blood mononuclear cells and their relationship to markers of inflammation, organ function, and outcome during severe sepsis. DesignProspective, longitudinal study. SettingUniversity hospital intensive care unit. PatientsTwenty-three postoperative patients with severe sepsis and 26 patients with uneventful postoperative course as well as 24 healthy, age-matched subjects. InterventionsSerum procalcitonin was determined by using an immunochemiluminescence assay, and C-reactive protein and leukocyte antigens were determined by using flow cytometry over 14 days in parallel with clinical data collection. Measurements and Main ResultsDespite a relative lymphopenia, absolute lymphocyte counts and CD4+/CD8+ T-cell ratio in septic patients were significantly elevated above normal. Particularly, CD4+ and CD8+ T-cell counts in nonsurvivors of sepsis were approximately twice as high as those of survivors. Significantly decreased monocytic HLA-DR expression was observed in both survivors and nonsurvivors at the onset of severe sepsis. Percentages of HLA-DR+ lymphocytes, however, were significantly increased during sepsis, especially in nonsurvivors. Whereas survivors of sepsis showed a continuous recovery of monocytic HLA-DR expression to ≥70% within 10 days, nonsurvivors were characterized by a second decrease in monocytic HLA-DR expression after day 7 or a permanent suppression (<40%). Peak of systemic inflammatory reaction, documented by maximum serum concentrations of procalcitonin and C-reactive protein, coincided with the nadir of monocytic HLA-DR expression. Moreover, procalcitonin and C-reactive protein as well as scores on the Acute Physiology and Chronic Health Evaluation II and Sepsis Organ Failure Assessment were inversely correlated with the monocytic HLA-DR expression. ConclusionsDecreases in monocytic HLA-DR expression occurred simultaneously with signs of hyperinflammation as early as the onset of severe sepsis and usually developed in opposite directions than inflammatory markers and sepsis severity scores.

Fish oil-supplemented parenteral diets normalize splanchnic blood flow and improve killing of translocated bacteria in a low-dose endotoxin rat model.

Objective: Intestinal ischemia decreases barrier function of the gut and enhances translocation of bacteria and toxins. Several studies indicate that fish oil can modulate prostaglandin formation and thus, regional blood flow and immune function. This study was performed to determine the effects of parenteral diets with omega‐3 fatty acids on microcirculation and barrier function of the gut. Design: Prospective, randomized, controlled animal study. Setting: University laboratory. Subjects: A total of 64 male Sprague‐Dawley CD rats. Interventions and Measurements: For 48 hrs, eight groups of eight rats each received total parenteral nutrition with four different types of lipids. The source of fat in group L was soybean oil only and in group L‐M a mixture of soybean oil and medium‐chain triglycerides. In groups FO‐20 and FO‐40, 20% or 40%, respectively, of the soybean oil in group L‐M was replaced by fish oil. The other four groups received an additional continuous infusion of endotoxin (0.1 mg/100 g body weight per day) for the last 24 hrs. Blood flow was measured with microspheres, and translocation was determined by microbiological methods and instillation of radioactive‐marked bacteria into the gut. Main Results: In the animals without fish oil, the endotoxin application reduced the blood flow to the intestine ∼25%. Animals with fish oil in their diets showed normal values. Translocation of gut bacteria was increased significantly in all endotoxin groups. However, less‐viable bacteria could be detected in the animals with fish oil diets in their mesenteric lymph nodes and livers. Conclusions: In this model, diets enriched with fish oil abolish the endotoxin‐induced decrease of nutritive blood flow to the gut and ameliorate the bactericidal defense of the splanchnic region. The lower count of viable bacteria in the fish oil groups is more related to an improved killing of translocated bacteria than a reduction of the translocation rate.

Pharmacokinetics and pharmacodynamics of the new propofol prodrug GPI 15715 in rates

Background and objective: We studied the pharmacokinetics and pharmacodynamics of GPI 15715 (Aquavan® injection), a new water-soluble prodrug metabolized to propofol by hydrolysis. Methods: Nine adult male Sprague-Dawley rats (398 ± 31 g) received a bolus dose of 40 mg GPI 15715. The plasma concentrations of GPI 15715 and propofol were determined from arterial blood samples, and the pharmacokinetics of both compounds were investigated using compartment models whereby the elimination from the central compartment of GPI 15715 was used as drug input for the central compartment of propofol. Pharmacodynamics were assessed using the median frequency of the EEG power spectrum. Results: A maximum propofol concentration of 7.1 ± 1.7 μg mL−1 was reached 3.7 ± 0.2 min after bolus administration. Pharmacokinetics were best described by two-compartment models. GPI 15715 showed a short half-life (2.9 ± 0.2 and 23.9 ± 9.9 min), an elimination rate constant of 0.18 ± 0.01 min−1 and a central volume of distribution of 0.25 ± 0.02 L kg−1. For propofol, the half-life was 1.9 ± 0.1 and 45 ± 7 min, the elimination rate constant was 0.15 ± 0.02 min−1 and the central volume of distribution was 2.3 ± 0.6 L kg−1. The maximum effect on the electroencephalogram (EEG) - EEG suppression for >4 s - occurred 6.5 ± 1.2 min after bolus administration and baseline values of the EEG median frequency were regained 30 min later. The EEG effect could be described by a sigmoid Emax model including an effect compartment (E0 = 16.9 ± 7.9 Hz, EC50 = 2.6 ± 0.8 μg mL−1, ke0 = 0.35 ± 0.04 min−1). Conclusions: Compared with known propofol formulations, propofol from GPI 15715 showed a longer half-life, an increased volume of distribution, a delayed onset, a sustained duration of action and a greater potency with respect to concentration.

Propofol in rats: testing for nonlinear pharmacokinetics and modelling acute tolerance to EEG effects.

BACKGROUND AND OBJECTIVE Pharmacokinetics of propofol in rats have usually been described using linear models. Furthermore, there are only a few investigations for a pharmacodynamic model of the electroencephalographic effects of propofol in rats. We investigated pharmacokinetics and pharmacodynamics of propofol in rats with special regard to linearity in pharmacokinetics and development of tolerance. METHODS Twelve adult male Sprague-Dawley rats received propofol in three successive infusion periods of 30 min each with infusion rates of 0.5, 1 and 0.5 mg kg(-1) min(-1). Propofol plasma concentrations were determined from arterial blood samples. Pharmacokinetics were tested for linearity using the ratio of the concentrations at the end of the first and second infusion interval as a model independent criterion. Several linear and nonlinear models were investigated with population pharmacokinetic analysis. Pharmacodynamics were analysed using the median frequency of the electroencephalographic power spectrum as a quantitative measure of the hypnotic effect. RESULTS Pharmacokinetics were found to be nonlinear and were best described by a two-compartment model with Michaelis-Menten elimination (Vm = 2.17 microg mL(-1) min(-1), Km = 2.65 microg mL(-1), k12 = 0.30 min(-1), k21 0.063 min(-1), Vc = 0.13 L). Acute tolerance to the electroencephalographic effect of propofol was observed. The hypnotic effect was best described by a sigmoid Emax model (E0 = 17.8 Hz, Emax = 17.7 Hz, EC50 = 4.1 microg mL(-1), gamma = 2.3, ke0 = 0.36 min(-1)) with competitive antagonism of propofol and a hypothetical drug in an additional tolerance compartment. CONCLUSIONS For the applied infusion scheme, propofol pharmacokinetics in rats were nonlinear and a development of tolerance to the electroencephalographic effect of propofol was observed during an infusion time of 90 min.

Influence of pyrrolidine dithiocarbamate on the inflammatory response in macrophages and mouse endotoxin shock.

To analyze the immunomodulatory effect of pyrrolidine dithiocarbamate (PDTC) on the endotoxin (LPS) stimulated inflammatory response, we measured the LPS-stimulated cytokine and NO production in murine peritoneal macrophages, J774A.1 cells and human whole blood in the presence of PDTC (60 microM). PDTC significantly inhibited the production of nitrite, IL-1beta and IL-6 in these cells. TNFalpha release was stimulated in murine cells, but suppressed in human whole blood. We further investigated the influence of PDTC on mortality and cytokine release in mouse endotoxin shock. PDTC was i.p. injected 30 min prior to the induction of endotoxin shock in female NMRI-mice and survival was significantly improved as compared to controls (48% vs 20%, n=25 per group). Plasma concentrations of TNFalpha were slightly augmented while IL-6 levels were decreased in PDTC-treated animals as compared to controls, however, without reaching significance. We conclude that PDTC is a potent immunomodulatory substance that modulates the inflammatory response in vitro and reduces mortality in mouse endotoxin shock. The pathophysiological mechanisms of the protective effect of PDTC in vivo, however, appears to be pluripotent, comprising both antioxidative properties and the inhibition of NF-kB.

Concentration–Effect Relations, Prediction Probabilities (Pk), and Signal-to-noise Ratios of Different Electroencephalographic Parameters during Administration of Desflurane, Isoflurane, and Sevoflurane in Rats

Background:The authors investigated the suitability of different electroencephalographic parameters to quantify the anesthetic effect of desflurane, isoflurane, and sevoflurane in rats. Methods:Ten male Sprague-Dawley rats were anesthetized in a randomized crossover design with maximum values of 11% desflurane, 2.1% isoflurane, and 3.5% sevoflurane. The electroencephalogram was recorded with implanted electrodes and a wireless telemetry system. Concentration–effect relations and signal-to-noise ratios were determined for the approximate entropy and for the median frequency and the spectral edge frequency, which were modified to account for spikes and burst suppression. The prediction probability Pk with respect to the response to a painful stimulus was determined. Results:All drugs produced deep anesthesia with burst suppression and no response at the highest concentrations. The occurrence of spikes and burst suppression made a modification of median frequency and spectral edge frequency necessary to obtain Pk values greater than 0.5 and monotonic sigmoid concentration–effect relations. The Pk values were between 0.89 and 0.98, with significantly higher values for modified median frequency and spectral edge frequency during desflurane and sevoflurane. The signal-to-noise ratios were between 3.0 and 6.4 dB, with significantly better values for modified spectral edge frequency and approximate entropy during sevoflurane. Conclusions:If modified for spikes and burst suppression, median frequency and spectral edge frequency as well as the unmodified approximate entropy were able to assess the anesthetic effect of desflurane, isoflurane, and sevoflurane in rats. For sevoflurane, the modified spectral edge frequency was best with regard to signal-to-noise ratio and prediction probability.