Fluid distribution kinetics during cardiopulmonary bypass

OBJECTIVE: The purpose of this study was to examine the isovolumetric distribution kinetics of crystalloid fluid during cardiopulmonary bypass. METHODS: Ten patients undergoing coronary artery bypass grafting participated in this prospective observational study. The blood hemoglobin and the serum albumin and sodium concentrations were measured repeatedly during the distribution of priming solution (Ringer's acetate 1470 ml and mannitol 15% 200 ml) and initial cardioplegia. The rate of crystalloid fluid distribution was calculated based on 3-min Hb changes. The preoperative blood volume was extrapolated from the marked hemodilution occurring during the onset of cardiopulmonary bypass. Clinicaltrials.gov: NCT01115166. RESULTS: The distribution half-time of Ringer's acetate averaged 8 minutes, corresponding to a transcapillary escape rate of 0.38 ml/kg/min. The intravascular albumin mass increased by 5.4% according to mass balance calculations. The preoperative blood volume, as extrapolated from the drop in hemoglobin concentration by 32% (mean) at the beginning of cardiopulmonary bypass, was 0.6-1.2 L less than that estimated by anthropometric methods (

Plasma disappearance rate of albumin when infused as a 20% solution.

BACKGROUND The transcapillary leakage of albumin is increased by inflammation and major surgery, but whether exogenous albumin also disappears faster is unclear. METHODS An intravenous infusion of 3 mL/kg of 20% albumin was given over 30 min to 70 subjects consisting of 15 healthy volunteers, 15 post-burn patients, 15 patients who underwent surgery with minor bleeding, 10 who underwent surgery with major bleeding (mean, 1.1 L) and 15 postoperative patients. Blood Hb and plasma albumin were measured on 15 occasions over 5 h. The rate of albumin disappearance from the plasma was quantitated with population kinetic methodology and reported as the half-life (T1/2). RESULTS No differences were observed for T1/2 between volunteers, post-burn patients, patients who underwent surgery with minor bleeding and postoperative patients. The T1/2 averaged 16.2 h, which corresponds to 3.8% of the amount infused per h. Two groups showed plasma concentrations of C-reactive protein of approximately 60 mg/L and still had a similarly long T1/2 for albumin. By contrast, patients undergoing surgery associated with major hemorrhage had a shorter T1/2, corresponding to 15% of the infused albumin per h. In addition, our analyses show that the T1/2 differ greatly depending on whether the calculations consider plasma volume changes and blood losses. CONCLUSION The disappearance rate of the albumin in 20% preparations was low in volunteers, in patients with moderately severe inflammation, and in postoperative patients

Can perioperative hemodilution be monitored with non-invasive measurement of blood hemoglobin?

BACKGROUND Trends in non-invasive measurements of blood hemoglobin (Hb) may be useful for identifying the need for transfusion in the perioperative period. METHODS Crystalloid fluid (5-20 mL/kg) was administered intravenously or by mouth to 30 volunteers and 33 surgical patients in five non-randomized clinical studies where Hb was measured on 915 occasions by non-invasive (Radical-7™) and invasive methodology. The hemodilution curves were compared by volume kinetic analysis and linear regression, with the slope and scattering of the data as key outcome measures. RESULTS The slope was 1.0, indicating unity between the two modes of measuring Hb when crystalloid fluid was infused in volunteers; however, only 40-45% of the variability in the non-invasive Hb could be explained by the invasive Hb. Patients undergoing major surgery, who showed the most pronounced hemodilution (median 24 g/L); non-invasive Hb explained 72% of the variability but indicated only half the magnitude of the invasive Hb changes (slope 0.48, P < 0.001 versus the volunteers). Simulations based on volume kinetic parameters from the volunteers showed 25% less plasma volume expansion after infusion when based on non-invasive as compared to invasive Hb, while no difference was found during infusion. CONCLUSIONS In volunteers the non-invasive Hb had good accuracy (low bias) but poor precision. In surgical patients the non-invasive Hb had good precision but systematically underestimated the hemodilution. Despite severe limitations, the non-invasive technology can be used to follow Hb trends during surgery if supported by occasional invasive measurements to assure acceptable quality of the hemodilution curve. TRIAL REGISTRATIONS ControlledTrials.gov NCT01195025, NCT01062776, NCT01458678, NCT03848507, and NCT01360333 on September 3, 2010, February 4, 2010, October 25, 2011, February 20, 2019, and May 25, 2011, respectively

The role of cardiolipin in the regulation of mitochondria-dependent apoptosis

Mitochondria are known as the powerhouse of the cell due to their central role in energy generation and as the site of key metabolic pathways. Over the past 15 years, it has become unequivocally clear that most pro-apoptotic stimuli require a mitochondria-dependent step, involving the permeabilisation of the mitochondrial outer membrane to apoptogenic factors, such as cytochrome c and Smac/DIABLO. The release of these factors into the cytosol is tightly regulated by proteins of the Bcl-2 family and results in the activation of the caspase cascade, leading to cell death. This event is considered as a point of no return in the apoptotic pathway and is often inhibited in cancer. Cardiolipin (CL) is a mitochondria-specific phospholipid that contains four acyl-chains. CL has been implicated in many of the mitochondria-dependent steps that lead to the release of apoptogenic factors including interaction with the Bcl-2 family protein tBid, Bax-dependant mitochondrial outer membrane permeabilization and cytochrome c release. Despite this growing body of evidence, the mechanism by which CL and its fatty acyl chain composition regulate mitochondrial apoptotic pathways remains unresolved, mostly due to the lack of cellular model. Tafazzin is a mitochondrial enzyme, which is mutated in Barth syndrome (BTHS) and is involved in the maturation process of CL. In BTHS, loss of tafazzin activity results in a decrease in mature CL, making it a good model to investigate the role of CL in apoptosis. Using BTHS patients-derived lymphoblastoid cells and HeLa cells in which tafazzin was stably knocked-down using RNA interference, this study provides the first evidence that mature CL are required for an efficient extrinsic apoptotic pathway in type II cells. Further investigation of the impaired apoptotic pathway revealed that the major block is in the activation of caspase-8. In this work, mature CL was identified as a crucial component of a mitochondrial platform required for caspase-8 translocation, oligomerization and activation following Fas signalling in type II cells. These results support a model in which once the first cleavage of procaspase-8 occurs at the DISC, the p43/p10 heteromer product translocates and inserts into the mitochondrial membrane in a CL-dependant manner. In the mitochondria, caspase-8 further oligomerizes and auto-cleaves to adopt its fully active form p18/p10. Additionally, it is shown here that mature CL is required for the physiological association of full-length Bid, the major caspase-8 cleavage substrate, with mitochondria. Thus, Bid is directly available for active caspase-8 on the mitochondrial surface where it cleaves into tBid, which in turn inserts into the mitochondrial outer membrane and induces cytochrome c release. Therefore, by tethering full-length Bid on mitochondria and by providing an activation site for caspase-8 following Fas signalling, CL brings together both the enzyme and its substrate and provides a platform from which the mitochondrial phase of apoptosis is launched. In summary, the data presented in this thesis provide the first evidence that mature CL participates in a new mitochondrial associated platform, called the “mitosome”, required for the activation of caspase-8 in type II cells.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Lysosomes in iron metabolism, ageing and apoptosis

The lysosomal compartment is essential for a variety of cellular functions, including the normal turnover of most long-lived proteins and all organelles. The compartment consists of numerous acidic vesicles (pH ∼4 to 5) that constantly fuse and divide. It receives a large number of hydrolases (∼50) from the trans-Golgi network, and substrates from both the cells’ outside (heterophagy) and inside (autophagy). Many macromolecules contain iron that gives rise to an iron-rich environment in lysosomes that recently have degraded such macromolecules. Iron-rich lysosomes are sensitive to oxidative stress, while ‘resting’ lysosomes, which have not recently participated in autophagic events, are not. The magnitude of oxidative stress determines the degree of lysosomal destabilization and, consequently, whether arrested growth, reparative autophagy, apoptosis, or necrosis will follow. Heterophagy is the first step in the process by which immunocompetent cells modify antigens and produce antibodies, while exocytosis of lysosomal enzymes may promote tumor invasion, angiogenesis, and metastasis. Apart from being an essential turnover process, autophagy is also a mechanism by which cells will be able to sustain temporary starvation and rid themselves of intracellular organisms that have invaded, although some pathogens have evolved mechanisms to prevent their destruction. Mutated lysosomal enzymes are the underlying cause of a number of lysosomal storage diseases involving the accumulation of materials that would be the substrate for the corresponding hydrolases, were they not defective. The normal, low-level diffusion of hydrogen peroxide into iron-rich lysosomes causes the slow formation of lipofuscin in long-lived postmitotic cells, where it occupies a substantial part of the lysosomal compartment at the end of the life span. This seems to result in the diversion of newly produced lysosomal enzymes away from autophagosomes, leading to the accumulation of malfunctioning mitochondria and proteins with consequent cellular dysfunction. If autophagy were a perfect turnover process, postmitotic ageing and several age-related neurodegenerative diseases would, perhaps, not take place

Cell death during sepsis: integration of disintegration in the inflammatory response to overwhelming infection

Sepsis is a major health problem and a leading cause of death worldwide. In recent years, a crescendo of attention has been directed to the mechanisms of cell death that develop during this disease, since these are viewed as important contributors to the proinflammatory and anti-inflammatory responses associated with poor outcome. Here we discuss mechanisms of cell death evident severe bacterial infection and sepsis including necrosis, apoptosis, pyroptosis, and extracellular trap-associated neutrophil death, with a particular emphasis on lymphocyte apoptosis and its contribution to the immunosuppressed phenotype of late sepsis. Individual bacterial pathogens express virulence factors that modulate cell death pathways and influence the sepsis phenotype. A greater knowledge of cell death pathways in sepsis informs the potential for future therapies designed to ameliorate immune dysfunction in this syndrome

Plasma concentrations of syndecan-1 are dependent on kidney function

Background Elevated plasma concentrations of syndecan-1 and heparan sulfate in studies of trauma, sepsis, and major surgery are commonly assumed to indicate acute glycocalyx degradation. We explored a possible role of the kidneys for these elevations. Methods Plasma and urine concentrations of syndecan-1, heparan sulfate, and biomarkers of inflammation were measured over 5 hours in 15 hospital patients treated for post-burn injury. The renal clearances of syndecan-1 and heparan sulfate (CLR) were calculated and their influence on the plasma concentration predicted by simulation. Results The urine/plasma concentration ratio was 0.9 (0.3-3.0) for syndecan-1 and 2.8 (2.0-4.3) for heparan sulfate. The CLR varied 250-fold for syndecan-1 and 10-fold for heparan sulfate. Multiple linear regression analysis showed that CLR for syndecan-1 was positively associated with the creatinine clearance (P &amp;lt; .0032) and the urine flow (P &amp;lt; .015). CLR for heparan sulfate increased with interleukin-6 (P &amp;lt; .003) and the urine flow (P &amp;lt; .01). Simulations suggested that a change in CLR from the mean of the highest 3 to the lowest three values would double plasma syndecan-1 within 4 hours and cause a 7-fold rise after 24 hours. A similar change in CLR for heparan sulfate would triple the plasma level within 24 hours, even if no increased shedding of the glycocalyx takes place. Conclusions The renal elimination of syndecan-1 and heparan sulfate varied greatly. A change in kidney function, which is common after trauma and major surgery, might alone induce several-fold changes in their plasma concentrations.Funding Agencies|Grifols; Region Ostergotland, Sweden</p

Recruitment of efferent lymph during infusion of 20% albumin

Background: Intravenous infusion of hyper-oncotic 20 % albumin expands the plasma volume by approximately twice the infused volume. We investigated whether the recruited fluid stems from accelerated flow of efferent lymph, which would add protein to the plasma, or from reversed transcapillary solvent filtration, where the solvent is expected to be low in protein.Methods: We analyzed data from 27 intravenous infusions of 20 % albumin (3 mL/kg; approximately 200 mL) over 30 min given to 27 volunteers and patients. Twelve of the volunteers were also given a 5 % solution and served as controls. The pattern of blood hemoglobin, colloid osmotic pressure, and the plasma concentrations of two immunoglobulins (IgG and IgM) were studied over 5 h.Results: A decrease of the difference between the plasma colloid osmotic pressure and plasma albumin occurred during the infusions and was almost four times greater for 5 % albumin than for 20 % albumin at 40 min (P &amp;lt; 0.0036), which indicates that non-albumin protein enriched the plasma when 20 % was infused. Moreover, the difference between the infusion-derived dilution of the blood plasma based on hemoglobin and the two im-munoglobulins amounted to-1.9 % (-6 to +0.2) for 20 % albumin and to-4.4 % (25th-75th percentile range -8.5 to +0.2) during experiments with 5 % albumin (P &amp;lt; 0.001). This supports that the plasma was enriched by immunoglobulins, probably via the lymph, when 20 % was infused.Conclusions: Between half and two-thirds of the extravascular fluid that was recruited during infusion of 20 % albumin in humans consisted of protein-containing fluid consistent with efferent lymph.Funding Agencies|Grifols; County Council of Ostergotland, Sweden; County Council of Ostergotland, Sweden</p

Kinetics of 5% and 20% albumin : A controlled crossover trial in volunteers

Background Albumin for intravenous infusion is marketed in two concentrations, 20% and 5%, but how they compare with regard to plasma volume expansion over time is unclear. Methods In a prospective crossover study, 12 volunteers received 3 ml kg(-1) of 20% albumin and, on another occasion, 12 ml kg(-1) of 5% albumin over 30 min. Hence, equivalent amounts of albumin were given. Blood was collected on 15 occasions over 6 h. Mass balance and volume kinetics were used to estimate the plasma volume expansion and the capillary leakage of albumin and fluid based on measurements of blood hemoglobin, plasma albumin, and the colloid osmotic pressure. Results The greatest plasma volume expansion was 16.0 +/- 6.4% (mean +/- SD) with 20% albumin and 19.0 +/- 5.2% with 5% albumin (p &amp;lt; .03). The volume expansion with 20% albumin corresponded to twice the infused volume. One third of the 5% albumin volume quickly leaked out of the plasma, probably because of the higher colloid osmotic pressure of the volunteer plasma (mean, 24.5 mmHg) than the albumin solution (19.1 mmHg). At 6 h, the capillary leakage amounted to 42 +/- 15% and 47 +/- 11% of the administered albumin with the 20% and 5% preparations, respectively (p = .28). The corresponding urine outputs were 547 (316-780) ml and 687 (626-1080) ml (median and interquartile range; p = .24). Conclusion The most important difference between the fluids was a dehydrating effect of 20% albumin when the same albumin mass was administered.Funding Agencies|Grifols</p