Femoral blood gas analysis, another tool to assess hemorrhage severity following trauma: an exploratory prospective study

BACKGROUND

Veno-arterial carbon dioxide tension difference (ΔPCO2) and mixed venous oxygen saturation (SvO2) have been shown to be markers of the adequacy between cardiac output and metabolic needs in critical care patients. However, they have hardly been assessed in trauma patients. We hypothesized that femoral ΔPCO2 (ΔPCO2 fem) and SvO2 (SvO2 fem) could predict the need for red blood cell (RBC) transfusion following severe trauma.

METHODS

We conducted a prospective and observational study in a French level I trauma center. Patients admitted to the trauma room following severe trauma with an Injury Severity Score (ISS) > 15, who had arterial and venous femoral catheters inserted were included. ΔPCO2 fem, SvO2 fem and arterial blood lactate were measured over the first 24 h of admission. Their abilities to predict the transfusion of at least one pack of RBC (pRBCH6) or hemostatic procedure during the first six hours of admission were assessed using receiver operating characteristics curve.

RESULTS

59 trauma patients were included in the study. Median ISS was 26 (22-32). 28 patients (47%) received at least one pRBCH6 and 21 patients (35,6%) had a hemostatic procedure performed during the first six hours of admission. At admission, ΔPCO2 fem was 9.1 ± 6.0 mmHg, SvO2 fem 61.5 ± 21.6% and blood lactate was 2.7 ± 1.9 mmol/l. ΔPCO2 fem was significantly higher (11.6 ± 7.1 mmHg vs. 6.8 ± 3.7 mmHg, P = 0.003) and SvO2 fem was significantly lower (50 ± 23 mmHg vs. 71.8 ± 14.1 mmHg, P < 0.001) in patients who were transfused than in those who were not transfused. Best thresholds to predict pRBCH6 were 8.1 mmHg for ΔPCO2 fem and 63% for SvO2 fem. Best thresholds to predict the need for a hemostatic procedure were 5.9 mmHg for ΔPCO2 fem and 63% for SvO2 fem. Blood lactate was not predictive of pRBCH6 or the need for a hemostatic procedure.

CONCLUSION

In severe trauma patients, ΔPCO2 fem and SvO2 fem at admission were predictive for the need of RBC transfusion and hemostatic procedures during the first six hours of management while admission lactate was not. ΔPCO2 fem and SvO2 fem appear thus to be more sensitive to blood loss than blood lactate in trauma patients, which might be of importance to early assess the adequation of tissue blood flow with metabolic needs.

Enhanced targeting of ultrasound contrast agents using acoustic radiation force

Contrast-enhanced ultrasound has shown significant promise as a molecular imaging modality. However, one potential drawback is the difficulty that ultrasound contrast agents (UCA) may have in achieving adhesion to target molecules on the vascular endothelium. Microbubble UCA exhibit a lateral migration toward the vessel axis in laminar flow, preventing UCA contact with the endothelium. In the current study, we have investigated low-amplitude acoustic radiation as a mechanism to move circulating UCA toward targeted endothelium. Intravital microscopy was used to assess the retention of microbubble UCA targeted to P-selectin in the mouse cremaster microcirculation and femoral vessels. Acoustic treatment enhanced UCA retention to P-selectin four-fold in cremaster venules and in the femoral vein and 20-fold in the femoral artery. These results suggest acoustic treatment as a mechanism for enabling ultrasound-based molecular imaging in blood vessels with hemodynamic and anatomical conditions otherwise adversarial for UCA retention.

MDMA and MDA Concentrations in Antemortem and Postmortem Specimens in Fatalities Following Hospital Admission

Over the last 15 years, numerous deaths involving "Ecstasy" (3,4-methylenedioxymethamphetamine, MDMA) have been reported and described in the literature. In most cases, either antemortem or postmortem concentration data are available. Because of the wide range of results and potential idiosyncratic nature of MDMA toxicity, interpretation of both antemortem and postmortem concentrations is difficult. The possible influence of postmortem redistribution may be an overlooked factor, but existing data involve postmortem concentrations from varying anatomical sites. However, this paper describes for the first time an evaluation of the concentrations of MDMA and 3,4-methylenedioxyamphetamine (MDA) found in five fatalities admitted to hospital where both antemortem and postmortem blood samples were available. Admission MDMA and MDA concentrations ranged between 0.55 and 4.33 mg/L and 0 and 0.10 mg/L, respectively, in antemortem serum/plasma. Postmortem blood MDMA and MDA concentrations ranged between 0.47 and 28.39 mg/L and 0.02 and 1.33 mg/L, respectively. Postmortem concentrations were higher than corresponding antemortem concentrations in all 5 cases with postmortem/antemortem ratios between 1.1 and 6.6 for MDMA and 1.5 and 13.3 for MDA. Differences in concentrations were also observed between anatomical sites, with central sites (e.g., heart) having much higher concentrations than peripheral sites (e.g., femoral). Overall, MDMA and MDA appear to exhibit postmortem redistribution and concentrations measured in postmortem specimens (even from peripheral sites) are not directly comparable with antemortem findings close to or prior to death.

An animal model of venous hypertension: The role of inflammation in venous valve failure

BACKGROUND

Clinical observation suggests that chronic venous insufficiency is related to failure of venous valves. Duplex ultrasound studies of lower extremity superficial veins regularly show valve failure and venous reflux. Gross morphologic observation of venous valves in surgical specimens shows tearing, splitting, scarring, and disappearance of valves.

HYPOTHESIS

Venous valve damage is acquired, linked with venous hypertension, and affected by inflammation.

OBJECTIVE

The objective of this study was to investigate the inflammatory process in valve remodeling associated with acute and chronic venous hypertension.

METHODS

A femoral arteriovenous fistula was created in study animals (Wistar rats, n = 60), and animals without an arteriovenous fistula were studied as controls (n = 5). At 1, 7, 21, and 42 days animals with the femoral arteriovenous fistula were anesthetized, and systemic pressure, the pressure in the femoral vein distal to fistula, and the pressure of the femoral vein in the contralateral hind limb were measured. Timed collection of blood backflow after division of the femoral vein distal to the fistula and in the alive, anesthetized animal was collected, measured, and calculated per unit time to be used as an indicator of valve insufficiency. The femoral vein distal to the fistula was harvested; valvular structures were examined and measured. Specimens were processed, and longitudinal sections were made and challenged with immunostaining antibodies against matrix metalloprotease (MMP)-2 and MMP-9. Sections were examined, and expression of molecular markers was determined by light absorption measurements after image digitization.

RESULTS

One week after the procedure, all animals exhibited some degree of hind limb edema ipsilateral to the arteriovenous fistula. Pressure in the femoral vein distal to the fistula was markedly increased on average to 96 +/- 9 mm Hg. Reflux was increased in a time-dependent manner, with the 21-day and 42-day groups showing the highest values. Valves just distal to the fistula showed an increased diameter of the valvular annulus and a shortening of the annular height. Venous wall findings included fibrosis and fusion of the media and adventitia and scarring and disappearance of valves principally in the 21- and 42-day specimens. Immunolabeling for MMP-2 showed an increased level in the 21- and 42-day groups. MMP-9 showed an increased level at 1 day, followed by a more marked level in the 21- and 42-day groups.

CONCLUSIONS

In this animal model of venous hypertension the findings of limb edema, increasing valvular reflux, and morphologic changes of increased annulus diameter and valve height are seen. Histologic changes included massive fibrosis of media and fusion with adventitia. Inflammatory markers MMP-2 and MMP-9 are strongly represented, and valve disappearance occurs after these markers are present. The gross morphologic changes seen are quite similar to those observed in human surgical specimens removed in treatment of venous insufficiency.

CLINICAL RELEVANCE

When observed angioscopically at the time of vein stripping, saphenous vein valves show severe deformities including shortening, scarring, and tearing. The current model of induced venous hypertension demonstrates early venous valve changes that replicate those observed in humans. This observation provides a link from venous hypertension to an induced inflammatory reaction that stimulates the valve damage. Thus the model could be useful for defining the fundamental mechanisms that cause venous valve failure and varicose veins and in pharmacologic testing to prevent or treat venous insufficiency.

Fatal 4-MTA intoxication: development of a liquid chromatographic-tandem mass spectrometric assay for multiple matrices

The case history and toxicological findings of an overdose fatality involving 4-methylthioamphetamine (4-MTA) and 3,4-methylenedioxymethamphetamine (MDMA) are reported along with a description of the analytical method. Detection and quantitation of 4-MTA and MDMA were performed by liquid chromatography-tandem mass spectrometry using phentermine as internal standard. Application of this technique to a variety of matrices allowed an insight in the distribution of 4-MTA. Several blood samples including femoral vein blood (5.23 mg/L), urine (95.5 mg/L), vitreous humor (1.31 mg/L), bile (36.4 mg/L), and numerous tissue samples such as liver (30.8 mg/kg), spleen (4.10 mg/kg), and frontal lobe (31.7 mg/kg) were assayed. These values indicated that 4-MTA could be identified as the cause of this fatality, whereas the concentrations of MDMA, also described, are less important because the concentrations found are lower. This case reports, for the first time, an extensive toxicological analysis of 4-MTA, by which the data presented may shed some light on the distribution of 4-MTA.

Secretion and clearance of the mature form of adrenomedullin in humans

In the biosynthesis of adrenomedullin (AM), glycine-extended AM, an intermediate form (iAM) processed from proAM is converted to AM[1-52]-NH2, the bioactive mature form of AM (mAM), by enzymatic amidation. We earlier showed that both molecular forms of AM circulate in human plasma. In the present study, to investigate the secretion and clearance sites of mAM and iAM in humans, we examined the plasma mAM and iAM concentrations in the femoral artery and vein (FA and FV), the aortic root and coronary sinus (AO and CS), and the pulmonary artery and capillary (PA and PC) of patients with ischemic heart disease. Plasma mAM in FV was significantly (p<0.001) higher than in FA. There also was a significant (p<0.001) step-up in the plasma mAM of the CS as compared to the AO. In contrast, plasma mAM was significantly (p<0.001) reduced in the PC as compared to the PA. However, such differences were not observed in plasma iAM levels. These findings suggest that in humans the vasculature of the lower extremities and the heart produce and secrete mAM and that the lung is a clearance site of circulating mAM.

The tissue plasminogen activator and urokinase response in vivo during natural resolution of venous thrombus

PURPOSE

The aim of this study was to measure the distribution of endogenous plasminogen activators during thrombolysis with an endothelial-conserving model of laminated thrombosis.

METHODS

Thrombi were raised in the inferior vena cava of rats with thrombin and flow reduction. The thrombi, adjacent vein wall, and distant veins (the superior vena cava) were removed at intervals from 1 hour to 21 days from formation and then cryohomogenized and assayed with specific bioimmunoassays for tissue-type (t-PA) and urokinase-type plasminogen activators (u-PA).

RESULTS

The measured t-PA activity of the vein wall around the thrombus was reduced compared with the control inferior vena cava at 4 days. Both the u-PA and t-PA content of the thrombus increased progressively during thrombolysis. The t-PA activity increased significantly in the distant vein walls in the animals with thrombi. Immunocytochemistry and in situ hybridization localized the t-PA to a mononuclear cell infiltrate and showed up-regulation of mRNA for rat t-PA in these monocytes.

CONCLUSIONS

The local plasminogen activator response was predominantly within the thrombus itself. Increased t-PA activity was additionally found in distant veins but was reduced in the vessel wall adjacent to the thrombus. This is the first report to show that u-PA activity is increased within organizing thrombus in vivo and that most of the t-PA activity is localized to a monocyte infiltrate.

Differences in amiodarone, digoxin, flecainide and sotalol concentrations between antemortem serum and femoral postmortem blood

1. The concentrations of amiodarone/desethylamiodarone, digoxin, flecainide and sotalol were measured in serum collected immediately prior to death and in postmortem blood collected from the femoral vein and artery of an 18-year-old male with congenital heart disease who developed a fatal arrhythmia. 2. The concentrations of all four drugs in the sample collected during life were consistent with the dosage given and in the range accepted for normal therapy. 3. There were no differences in amiodarone/desethylamiodarone, flecainide and sotalol concentrations in arterial or venous postmortem blood. 4. The concentrations of desethylamiodarone, digoxin, flecainide and sotalol but not amiodarone, were higher in postmortem blood than in antemortem serum. The flecainide concentration was significantly greater than the upper limit associated with toxicity in life. Without knowledge of the true concentration measured in life, this apparently high, toxic concentration would have suggested that death could have resulted from arrhythmogenic/proarrhythmic effects of the drug in excess. 5. These results further demonstrate the hazards in interpreting postmortem blood concentrations following suspected drug intoxication.

Site dependence of postmortem blood methadone concentrations

A case investigated by the Office of the Chief Medical Examiner, State of Maryland, identified methadone at a heart blood concentration of 2.4 mg/L and a subclavian blood concentration of 0.8 mg/L. Due to these discrepant results, a study was undertaken to determine whether such inconsistencies occurred in other methadone cases. Of the 15 cases studied, only four had heart blood and alternate blood concentrations within 20% of one another. In only 53% of the cases were variations of < 60% observed. The data failed to show a trend where one site was consistently higher or lower than the other site.

L-Arginine deficiency after liver transplantation as an effect of arginase efflux from the graft. Influence on nitric oxide metabolism

L-Arginine plays an important role in protecting animals against ammonia intoxication, enhances immune function, stimulates wound healing, and is the precursor for the endothelium-derived relaxing factor, recently recognized as nitric oxide (NO). In this study, we investigated the influence of hepatic reperfusion on amino acid metabolism after human OLT. After 10 sec of reperfusion, the arterial plasma levels of L-arginine dropped from 105 +/- 12 mumol/L to 3.8 +/- 0.6 mumol/L (P < 0.001), whereas plasma ornithine increased from 40 +/- 5.5 mumol/L to 129 +/- 15 mumol/L (P < 0.001). The reduced L-arginine levels remained subnormal for several hours after OLT. This drop in plasma L-arginine was due to an arginase release from the implanted graft. Immediately after reperfusion, the plasma concentrations of arginase increased from pretransplantation values of 18 +/- 13 IU/L to 2384 +/- 1456 IU/L (P < 0.01). Measurement of plasma nitrite (NO2-) and nitrate (NO3-), which are the stable end products of NO, revealed that NO2- decreased about 50% after reperfusion (from 1.64 +/- 0.32 mumol/L to 0.80 +/- 0.17 mumol/L; P < 0.001), whereas NO3- levels remained unchanged (76 +/- 23 mumol/L vs. 63 +/- 8 mumol/L). We conclude that hepatic reperfusion causes L-arginine deficiency by liberating high amounts of arginase from the implanted graft. This L-arginine depletion may influence the NO synthesis in patients after OLT.

[Evolution of biomechanical changes and microstructural components in autogenous vein grafts]

We evaluated the compliance characteristics of autogenous vein grafts clinically and experimentally. The image analysis instrument was applied in measuring the relative contents of elastin and collagen of the grafts. The results showed the consistent compliance mismatch between the vein graft and the host artery, but no definitive bearing on abnormal blood flow velocity waveform by the compliance mismatch. The compliance characteristics of the vein graft resembled these of the vein rather than those of the artery. The relative contents of elastin and collagen within the graft wall and the ratio of collagen to elastin (C/E) did not change significantly as a function of time. The vein graft and vein had the similar value of C/E, which was lower than that of the artery.

Beta-endorphin concentration in the femoral and spermatic venous blood of males affected by varicocele

Several studies in the rat indicate that opioid peptides produced in the testicular interstitial compartment can affect events in the tubular compartment. For example, it is thought that some specific functions of Sertoli cells, such as androgen-binding protein production are decreased by a paracrine mechanism. In this study ACTH beta-endorphin and cortisol were measured in the femoral and spermatic venous blood drawn from 18 patients affected by varicocele during catheterization for venous occlusion. The results showed the absence of a significant secretory gradient of beta-endorphin in the human testis and also demonstrated that this opioid is circulating at picomolar concentrations within human testis under stress conditions.