Efficacy and safety of phospholipid nanoparticles (VBI-S) in reversing intractable hypotension in patients with septic shock: a multicentre, open-label, repeated measures, phase 2a clinical pilot trial.

Background: Since the 1990's attempts to favorably modulate nitric oxide (NO) have been unsuccessful. We hypothesized that because NO is lipophilic it would preferentially localize into intravascularly infused hydrophobic nanoparticles, thereby reducing its bioavailability and adverse effects without inhibiting its production. We aimed to determine the efficacy and safety of intravenous infusion of a fluid comprised of hydrophobic phospholipid nanoparticles (VBI-S) that reversibly absorb NO in the treatment of hypotension of patients in severe septic shock. Methods: This is a multicentre, open-label, repeated measures, phase 2a clinical pilot trial done at six hospital centers in the USA. Patients in severe septic shock were enrolled after intravenous fluid therapy had failed to raise mean arterial blood pressure (MAP) to at least the generally accepted level of 65 mmHg, requiring the use of vasopressors. The primary endpoint of this study is the proportion of patients in whom MAP increased by at least 10 mmHg. VBI-S was administered intravenously to patients as boluses of 100 ml, 200 ml, 400 ml, and 800 ml at 999 ml/min until the blood pressure goal was reached after which the infusion was stopped, and the MAP was recorded. All patients who received any volume of VBI-S were included in the primary and safety analysis. The study is registered with ClinicalTrials.gov, NCT04257136. Findings: Between February 17, 2020 and January 3, 2023, 20 eligible patients were enrolled in the study. In all 20 (100%) patients, the goal of increasing MAP by at least 10 mmHg using VBI-S was achieved (p = 0.0087, effect size = 0.654). Mean VBI-S volume required to meet the primary goal was 561.0 ± 372.3 ml. The goal of lowering vasopressor dose was also achieved (p = 0.0017). Within 48 h or less after VBI-S, there was a statistically significant improvement in oxygenation, serum creatinine, clotting variables, procalcitonin, lactic acid, and the sequential organ failure assessment (SOFA) score. At 24 h and 48 h following administration of VBI-S, 12/15 (80%) and 9/12 (75%) patients developed hyperlipidemia, respectively. No severe adverse events of VBI-S were observed, and there were no treatment-related deaths. Interpretation: These preliminary findings suggest the safety and efficacy of VBI-S in treating hypotension in patients with septic shock. However, a definitive mortality benefit cannot be demonstrated without a randomized controlled study. Funding: The Naval Medical Research Command-Naval Advanced Medical Development program via the Medical Technology Enterprise Consortium.

Intra-Arterial Perimortem Resuscitation Using a Micellar Colloid.

OBJECTIVE: The following were studied in a perimortem mouse model of rapid blood loss: (a) efficacy of a prototypical micellar colloid, Intralipid 20%, (IL20), compared to albumin (b) comparison of intra-arterial and intravenous resuscitation, (c) efficacy of IL20 at a volume 2 × the volume of blood removed, and (d) efficacy of oxygenated IL20 after clinical death (CD). METHODS: CD, the absence of breathing and zero blood pressure (BP), was produced by removing 55% of the blood volume within 3 minutes. After CD, the chest was opened to observe ventricular contraction. IL20, Ringer's lactate (RL), or albumin was infused perimortem. RESULTS: Without resuscitation CD occurred in 2.85 ± 0.40 minutes. Ventricular contraction persisted 20.50 ± 1.11 minutes after CD. RL infused immediately after CD restored breathing if given intra-arterially but not intravenously. IL20 was superior to the prototypical colloid, albumin in maintaining the BP. Increasing the volume of IL20 further increased BP. Delayed RL infusion after CD failed to restore breathing. Delayed resuscitation after CD with oxygenated IL20 restored breathing and BP. CONCLUSIONS: Micellar colloid is superior to the prototypical colloid albumin and can possibly be of use when signs of life are no longer present. In extremis, intra-arterial infusion is superior to intravenous infusion.

Quantitation of dissolved gas content in emulsions and in blood using mass spectrometric detection.

Quantitation of dissolved gases in blood or in other biological media is essential for understanding the dynamics of metabolic processes. Current detection techniques, while enabling rapid and convenient assessment of dissolved gases, provide only direct information on the partial pressure of gases dissolved in the aqueous fraction of the fluid. The more relevant quantity known as gas content, which refers to the total amount of the gas in all fractions of the sample, can be inferred from those partial pressures, but only indirectly through mathematical modeling. Here we describe a simple mass spectrometric technique for rapid and direct quantitation of gas content for a wide range of gases. The technique is based on a mass spectrometer detector that continuously monitors gases that are rapidly extracted from samples injected into a purge vessel. The accuracy and sample processing speed of the system is demonstrated with experiments that reproduce within minutes literature values for the solubility of various gases in water. The capability of the technique is further demonstrated through accurate determination of O(2) content in a lipid emulsion and in whole blood, using as little as 20 µL of sample. The approach to gas content quantitation described here should greatly expand the range of animals and conditions that may be used in studies of metabolic gas exchange, and facilitate the development of artificial oxygen carriers and resuscitation fluids.

Histidine inhibits the degradation of cells suspended in Ringer's lactate.

BACKGROUND: We previously demonstrated that the degradation of a suspension of Jurkat cells in Ringer's lactate (RL) was inhibited by the addition of a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid/Tris buffer. Given the ability of histidine to buffer protons in the physiologic range (pKa = 6.0), we hypothesized that this amino acid would have the same effect. METHODS: RL was made in our laboratory using sodium l-lactate. Jurkat cells were suspended in RL alone or RL with various concentrations of histidine or other test reagents at 37 degrees C for 4 hours or 24 hours in an atmosphere of 95% air and 5% CO2. Using flow cytometry, we measured cell shrinkage, phosphatidylserine translocation, propidium iodide uptake, and intracellular oxygen free radical production. RESULTS: Cell shrinkage was induced by suspension in RL after 4 hours incubation. At 4 hours, cell shrinkage was inhibited by all concentrations of histidine tested, 7.8 mumol/L to 10 mmol/L. There was no statistical difference between cells suspended in medium and cells suspended in 1 mmol/L or 10 mmol/L histidine. After 24 hours incubation, 100% of the cells in RL had undergone cell shrinkage whereas in 10 mmol/L histidine only a mean of 20% of the cells had undergone cell shrinkage. The inhibitory effect of 1 mmol/L histidine at pH 7.4 was compared with that at pH 6.8. After 4 hours incubation, there was no difference. After 24 hours incubation, the inhibitory effect at pH 7.4 was significantly greater that that at pH 6.8. Histidine at 1 mmol/L to 10 mmol/L significantly reduced the percentage of cells that underwent phosphatidylserine translocation and propidium iodide uptake. The effect of the dipeptide buffer, glycylglycine, and the two other positively charged amino acids, arginine and lysine, after 4 hours incubation was compared with histidine at 1 mmol/L. At 1 mmol/L, histidine was superior to arginine and lysine and indistinguishable from glycylglycine. Intracellular free radical production was measured at 0.5 mmol/L, 1.0 mmol/L, and 10 mmol/L histidine concentrations. There was significant inhibition only at 10 mmol/L. CONCLUSIONS: Characteristics of apoptotic cell death that occur in cells suspended in RL are inhibited by the addition of histidine, arginine, and lysine as well as the dipeptide glycylglycine, which, with a pKa of 8.25, also buffers in the physiologic range. Histidine is superior to lysine and arginine at 1 mmol/L. The salutary effect of histidine at 0.5 mmol/L and 1 mmol/L is caused by a mechanism other than the inhibition of oxygen free radicals. Moreover, the buffering of protons may play a role at 24 hours but made no difference at 4 hours.

Heterogeneity in the effect of albumin and other resuscitation fluids on intracellular oxygen free radical production.

BACKGROUND: We hypothesized that by studying a suspension of a single cell type in various resuscitation fluids, we could compare their effects on parameters associated with cell death. METHODS: Jurkat cells were suspended in resuscitation fluids. Using flow cytometry, light scatter, phosphatidylserine translocation, propidium iodide uptake, and intracellular H2O2 production were measured. RESULTS: Buffer (pH, 7.4) and albumin added to Ringer's lactate inhibited the adverse changes, including intracellular oxygen free radical production. Oxygen free radical production was variable within the cell population and inhibited by albumin but not other colloids or crystalloids. This correlated well with the ability of albumin to enhance metabolic activity. A flavoprotein inhibitor blocked H2O2 production, suggesting that mitochondria are the source of the H2O2 and the variability. CONCLUSION: Oxygen free radical inhibition by albumin could explain both its beneficial and its harmful effects.