Impact of Transfused Citrate on Pathophysiology in Massive Transfusion

UNLABELLED: This narrative review article seeks to highlight the effects of citrate on physiology during massive transfusion of the bleeding patient. DATA SOURCES: A limited library of curated articles was created using search terms including citrate intoxication, citrate massive transfusion, citrate pharmacokinetics, hypocalcemia of trauma, citrate phosphate dextrose, and hypocalcemia in massive transfusion. Review articles, as well as prospective and retrospective studies were selected based on their relevance for inclusion in this review. STUDY SELECTION: Given the limited number of relevant studies, studies were reviewed and included if they were written in English. This is not a systematic review nor a meta-analysis. DATA EXTRACTION AND SYNTHESIS: As this is not a meta-analysis, new statistical analyses were not performed. Relevant data were summarized in the body of the text. CONCLUSIONS: The physiologic effects of citrate independent of hypocalcemia are poorly understood. While a healthy individual can rapidly clear the citrate in a unit of blood (either through the citric acid cycle or direct excretion in urine), the physiology of hemorrhagic shock can lead to decreased clearance and prolonged circulation of citrate. The so-called Diamond of Death of bleeding-coagulopathy, acidemia, hypothermia, and hypocalcemia-has a dynamic interaction with citrate that can lead to a death spiral. Hypothermia and acidemia both decrease citrate clearance while circulating citrate decreases thrombin generation and platelet function, leading to ionized hypocalcemia, coagulopathy, and need for further transfusion resulting in a new citrate load. Whole blood transfusion typically requires lower volumes of transfused product than component therapy alone, resulting in a lower citrate burden. Efforts should be made to limit the amount of citrate infused into a patient in hemorrhagic shock while simultaneously addressing the induced hypocalcemia

Fluorescence-based optical glucose sensing

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 60-65).Issued also on microfiche from Lange Micrographics.Previous studies have indicated that optical means of blood glucose detection are feasible and provide a minimally invasive alternative to current commercially available modalities. Fluorescence spectroscopy has shown promise in many examples of optical diagnostics and offers the advantage of specificity to particular analytes. Discussed in this thesis are the most recent experimental results of a fluorescence-based glucose sensor in vivo with external monitoring equipment. Polymer spheres containing a competitive binding glucose assay featuring two fluorophores that interact in a resonance energy transfer are implanted under the skin of an animal model, the hairless rat, and preliminary testing on the longevity, feasibility, and responsiveness of the sensor is reported. Fluorophore excitation and signal acquisition occurs via a custom fiber bundle probe that can be placed in direct contact with the subject's skin, delivering argon ion laser light to the sensor through a central fiber and receiving emissions through surrounding fibers. Spectral analysis is performed using a spectrometer and charge-coupled device (CCD) camera connected to a computer. Also included in this thesis is a discussion of modifications made to the Monte Carlo photon propagation modeling software to accommodate spectral input in the form of a Gaussian distributed source (e.g. laser) or an arbitrary user-defined spectrum (e.g. HgXe arc lamp). The new code offers the user the ability to input source information as well as tissue property responses to changes in photon wavelength

Comparative response of platelet fV and plasma fV to activated protein C and relevance to a model of acute traumatic coagulopathy.

BACKGROUND: Acute traumatic coagulopathy (ATC) has been linked to an increase in activated protein C (aPC) from 40 pM in healthy individuals to 175 pM. aPC exerts its activity primarily through cleavage of active coagulation factor Va (fVa). Platelets reportedly possess fVa which is more resistant to aPC cleavage than plasma fVa; this work examines the hypothesis that normal platelets are sufficient to maintain coagulation in the presence of elevated aPC. METHODS: Coagulation responses of normal plasma, fV deficient plasma (fVdp), and isolated normal platelets in fVdp were conducted: prothrombin (PT) tests, turbidimetry, and thromboelastography (TEG), including the dose response of aPC on the samples. RESULTS: PT and turbidimetric assays demonstrate that normal plasma is resistant to aPC at doses much higher than those found in ATC. Additionally, an average physiological number of washed normal platelets (200,000 platelets/mm3) was sufficient to eliminate the anti-coagulant effects of aPC up to 10 nM, nearly two orders of magnitude above the ATC concentration and even the steady-state pharmacological concentration of human recombinant aPC, as measured by TEG. aPC also demonstrated no significant effect on clot lysis in normal plasma samples with or without platelets. CONCLUSIONS: Although platelet fVa shows slightly superior resistance to aPC's effects compared to plasma fVa in static models, neither fVa is sufficiently cleaved in simulations of ATC or pharmacologically-delivered aPC to diminish coagulation parameters. aPC is likely a correlative indicator of ATC or may play a cooperative role with other activity altering products generated in ATC

aPC does not induce fibrinolysis inherently in the presence or absence of tPA.

<p>Clotting parameters of normal PFP and PRP (normalized to 200,000 platelets/mm³) treated exogenously with aPC and tPA were measured in TEG. Clot lysis parameters (A) LY30 and (B) LY60 (percentage of clot lysis at 30 and 60 min, respectively) demonstrate that for a given dose of tPA (0, 1, 1.5, or 2 nM), the dose of aPC (0, 175, or 750 pM) has no effect on clot lysis. The doses of aPC correspond to those found in trauma and the steady-state pharmacological dose. Concentrations of tPA were chosen such that a known response would occur in the absence of aPC. In the absence of tPA, PFP did not experience any lysis while PRP had a limited degree of clot lysis. However, for all non-zero doses of tPA, PFP experienced a greater degree of lysis than PRP. Means of three samples with standard deviation are shown.</p

Platelet supplementation effects on TEG coagulation measurements in fVdp and normal PFP.

<p>(A) While increasing the number of platelets in PFP has very little effect on the initiation of coagulation, a much more powerful response is observed in fVdp as platelets are increased from 10,000/mm³ to 100,000/mm³ (***: p<0.001 for the null hypothesis that PFP = fVdp; **: p<0.01; *: p<0.05; n.s.: not significant). Diminishing returns are seen in higher numbers of platelets, with no significant differences observed in the 300,000/mm³ and 400,000/mm³ concentrations of platelets compared with equivalent numbers in PFP. (B) Increasing platelets from 10,000/mm³ to 100,000/mm³ dramatically improves the alpha angle; the effect plateaus above 150,000 platelets/mm³. No alpha angle differences are observed due to the presence of fV protein in the plasma. (C) Similar to rate of clotting, strength of clot rises rapidly with increasing platelet counts until 100,000/mm³ where a plateau occurs. No significant differences are observed between fVdp and normal PFP with equal numbers of platelets. Means of three samples with standard deviation are shown.</p

Prothrombin times of plasmas treated with aPC.

<p>Increasing aPC from 0 to 3.3 nM has no effect on PT regardless of fV levels. In fVdp and fVdp supplemented with 2(***: p<0.001 for the null hypothesis of the indicated samples; **: p<0.01; *: p<0.05). Means of three samples are shown with standard deviation.</p

Platelets are resistant to the anti-coagulant effects of aPC as measured in TEG.

<p>For fVdp containing 200,000/mm³, the (A) R-time (clotting time), (B) alpha angle (rate of clotting), and (C) G-value (clot strength) are only strongly affected by aPC at a concentration of 100 nM compared to all lower doses. The 33 nM dose of aPC demonstrated a significant difference versus all lower concentrations in the alpha angle and all lower concentrations except 10 nM for R-time. G-value was not significantly affected except by the 100 nM aPC dose, although the trend is observable at 33 nM (***: p<0.001 for the null hypothesis that the indicated samples are equal; **: p<0.01; *: p<0.05; n.s.: not significant). Means of three samples with standard deviation are shown.</p

aPC concentrations below 10 nM have no significant effect on PL acceleration of clotting in PFP.

<p>In the turbidimetric assay, fibrin crosslinking corresponds to an increase in absorbance at 405</p

Nanomolar amounts of aPC are required to degrade fVIII activity.

<p>In fresh PFP, no change in fVIII activity by aPC was observed until a dose >10 nM (p<0.001). fVdp showed a similar trend (p<0.05 that 3.3 nM and 100 nM aPC are different); fVIIIdp was used as a negative control. The mean and standard deviation of four PFP samples is shown; fVdp and fVIIIdp are means and standard deviations of two technical replicates.</p