Thrombin—antithrombin III complex in fulminant hepatic failure: evidence for disseminated intravascular coagulation and relationship to outcome

Indirect evidence has suggested that intravascular coagulation may occur in patients with fulminant hepatic failure (FHF), the most severe form of acute liver disease. Thrombin is inhibited in circulation by antithrombin III, and measurement of the thrombin-antithrombin III complex (TAT) is a direct measure of thrombin formation. Using a new rapid enzyme-linked immunosorbent assay we have measured TAT in 54 patients on admission, with fulminant hepatic failure. TAT was significantly increased in patients with FHF compared with control subjects (25.8 +/- 2.7 micrograms l-1) compared with 2.6 +/- 0.2 micrograms l-1; n = 10: P less than 0.001). Patients who survived had significantly lower TAT levels than those who did not (17.2 +/- 2.7 micrograms l-1; n = 27 compared with 34.0 +/- 4.2 micrograms l-1; n = 27: P less than 0.005) and patients with FHF caused by viral hepatitis had significantly lower TAT levels than those with FHF due to paracetamol overdose (14.6 +/- 4.7 micrograms l-1; n = 9 compared with 28.0 +/- 3.1 micrograms l-1; n = 45: P less than 0.05). Levels of TAT correlated significantly with prothrombin time (r = 0.36, P less than 0.01) and inversely with fibrinogen (r = -0.51, P less than 0.001). There was no significant correlation with antithrombin III concentration. Thus, using a simple and rapid technique, we have been able to demonstrate increased levels of TAT complex in patients with FHF. This provides more direct evidence of intravascular coagulation and thrombin generation in these patients. These results confirm that the coagulation system is activated in FHF.     

Plasma fibronectin synthesis in normal and injured humans as determined by stable isotope incorporation.

In humans, plasma fibronectin decreases early after operative injury, burn, or trauma, followed by a rapid restoration with a secondary decline typically observed if such patients become septic. We determined the rate of plasma fibronectin and plasma fibrinogen synthesis in normal subjects and injured patients using a stable isotope incorporation technique with [15N]glycine. During a constant 14-h infusion of [15N]glycine, the enrichment of [15N]glycine in both the free plasma glycine precursor pool as well as the urinary hippurate pool was determined; the latter used as an estimate of intracellular hepatic precursor enrichment. [15N]Glycine enrichment in both plasma fibronectin and fibrinogen was also quantified. The synthesis rate (Js/V) expressed in micrograms per milliliter of plasma per hour and the fractional synthesis rate (FSR) expressed as percentage of the plasma pool produced per day were determined. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into urinary hippurate was 35.35 +/- 1.46%/d, whereas the Js/V was 4.45 +/- 0.19 micrograms/ml plasma per h. In normal subjects, the FSR for plasma fibronectin using 15N enrichment into free plasma glycine was 14.73 +/- 0.63%/d, whereas the Js/V was 1.98 +/- 0.09 micrograms/ml plasma per h. Early (2-3 d) after burn injury, fibronectin synthesis was increased (Js/V = 5.74 +/- 0.36; P less than 0.05), whereas later after injury, fibronectin synthesis began to decline (Js/V = 3.52 +/- 0.24; P less than 0.05) based on 15N enrichment of urinary hippurate. In contrast, the Js/V and FSR of plasma fibrinogen, a well-documented acute-phase plasma protein, revealed a sustained elevation (P less than 0.05) after injury in both the trauma and burn patients. Thus, plasma fibronectin synthesis is elevated early postinjury, which may contribute to the rapid restoration of its blood level. However, once fibronectin levels have normalized, the synthesis of plasma fibronectin appears to decline.     

Measurement of plasma fibronectin in patients who develop the adult respiratory distress syndrome

Depletion of plasma fibronectin has been observed in certain clinical conditions predisposing to the adult respiratory distress syndrome and has been associated with cardiopulmonary dysfunction in experimental lung injury. We evaluated prospectively the relationship between plasma fibronectin concentration and the development of the adult respiratory distress syndrome in patients known to be at high risk. Although plasma fibronectin levels in participants at study entry were lower in this population (mean 258 +/- 132 micrograms/ml) than in normal volunteers (461 +/- 127 micrograms/ml, p less than 0.0025), there was no difference between patients who subsequently developed the adult distress syndrome (mean 255 +/- 149 micrograms/ml) and those with similar illness or injury who did not develop the syndrome (260 +/- 126 micrograms/ml). Fibronectin concentration was not further depressed even after development of adult respiratory distress syndrome and did not correlate with degree of pulmonary dysfunction. These data suggest that fibronectin depletion is not an important determinant of respiratory failure in humans. Patients with sepsis syndrome had significantly lower plasma fibronectin levels than those without sepsis (187 +/- 119 micrograms/ml vs. 273 +/- 131 micrograms/ml, p less than 0.05), suggesting a possible role for fibronectin in the pathogenesis of sepsis.     

Interaction of verapamil and cimetidine: stereochemical aspects of drug metabolism, drug disposition and drug action

The pharmacokinetics, metabolism and pharmacodynamics of verapamil (160 mg p.o. of a pseudoracemic mixture) were evaluated in six healthy volunteers before and after coadministration of cimetidine (400 mg b.i.d.). Enantiomers of verapamil and enantiomers of three major urinary metabolites (norverapamil, D-617 and D-620) were determined in plasma and urine by gas chromatography-mass spectrometry. Coadministration of cimetidine led to a significant increase in the area under the plasma concentration vs. time curve of S-verapamil (29.2 +/- 31.8 min x nmol x ml-1 vs. 41.2 +/- 33.7 min x nmol x ml-1; P less than .003) and R-verapamil (124.7 +/- 112.2 min x nmol x ml-1 vs. 156.8 +/- 105.0 min x nmol x ml-1; P less than .01). The increase was significantly greater for the pharmacologically more potent S-enantiomer compared to R-verapamil (150.3 +/- 37 vs. 117.8 +/- 15%; P less than .05). As a consequence, coadministration of cimetidine increased the negative dromotropic effect of verapamil on atrioventricular conduction in five of six subjects. In addition, fractional metabolic clearance to D-620 and D-617 decreased for both enantiomers. Tubular secretion of S-D-617 was inhibited by cimetidine (342 +/- 104 vs. 238 +/- 52 ml x min-1; P less than .05) whereas secretion of the R-enantiomer remained unchanged (276 +/- 91 vs. 222 +/- 43 ml x min-1). Thus, cimetidine interacts with both hepatic and renal verapamil elimination in a stereoselective manner. The increase in total plasma concentration of verapamil combined with an increase in eutomer/distomer ratio produces a more pronounced pharmacological effect of verapamil when cimetidine is coadministered.     

Mexiletine effects on theophylline disposition

The effect of mexiletine administration on steady-state plasma theophylline concentrations was studied in eight normal healthy men in a prospective open label nonrandomized two-way crossover trial. Repeated doses of 300 mg of sustained-release theophylline were given every 12 hours for 9 days. Mexiletine hydrochloride, 200 mg every 8 hours, was given for five consecutive doses starting on the morning of day 6. Mexiletine increased theophylline levels in all subjects. Mean predose (trough) levels rose from 8.1 +/- 0.1 microgram.ml-1 to 13.4 +/- 0.6 micrograms.ml-1 and AUC(0-12) from 96.8 +/- 9.1 to 160.2 +/- 3.7 micrograms.ml-1.hr. Plasma clearance was reduced by mexiletine from 44.7 +/- 5.1 to 25.4 +/- 1.2 ml.hr-1. Both N-demethylated metabolites of theophylline were decreased by 60% by mexiletine, whose levels remained within its therapeutic range. Theophylline levels returned to pre-mexiletine values when this drug was discontinued. Mexiletine reduces theophylline clearance and increases its plasma concentration by inhibiting N-demethylation of theophylline. Plasma theophylline levels should be monitored when mexiletine is added.     

Atrial natriuretic peptide: evidence of action as a natriuretic hormone at physiological plasma concentrations in man

The administration of exogenous atrial natriuretic peptide (ANP) causes a natriuresis and diuresis in man, but this has, to date, only been demonstrated at plasma ANP concentrations within the high pathological or pharmacological ranges. Evidence that ANP acts physiologically requires the demonstration of a natriuretic effect when it is infused to recreate plasma concentrations similar to those observed after physiological stimuli. We infused human alpha-ANP (1-28) at a calculated rate of 1.2 pmol min-1 kg-1 for 3 h into seven water-loaded normal subjects, achieving plasma ANP concentrations within the upper part of the physiological range. The subjects' resting plasma ANP concentration increased from 3.8 +/- 1.5 to 20.9 +/- 1.9 pmol/l. The infusion of ANP caused a 60% increase of mean urinary sodium excretion from 111 +/- 18 to 182 +/- 30 mumol/min (P less than 0.001) and a 28% increase of mean water excretion from 10.8 +/- 0.8 to 13.8 +/- 1.6 ml/min (P less than 0.01). The infusion suppressed mean plasma renin activity from 1.55 +/- 0.10 to 1.17 +/- 0.06 pmol of ANG I h-1 ml-1 (P less than 0.001). Mean plasma aldosterone concentration (242 +/- 16 basally and 215 +/- 15 pmol/l at the end of ANP infusion) did not change significantly. Pulse rate and blood pressure were unchanged throughout the study. No significant change in any of the variables mentioned above occurred during the infusion of the vehicle alone on a separate study day.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clearance of brain natriuretic peptide in patients with chronic heart failure: indirect evidence for a neutral endopeptidase mechanism but against an atrial natriuretic peptide clearance receptor mechanism.

1. Brain natriuretic peptide is a new natriuretic hormone with striking similarity to atrial natriuretic peptide, but there are no previous data concerning its clearance in man. Two pathways of clearance for atrial natriuretic peptide are recognized: degradation by neutral endopeptidase and binding to atrial natriuretic peptide clearance receptors. We have examined the effect of candoxatril, an inhibitor of neutral endopeptidase (dose range 10-200 mg), and the effect of an infusion of a pharmacological dose [45 micrograms (90 micrograms in two patients)] of synthetic human atrial natriuretic peptide on plasma human brain natriuretic peptide-like immunoreactivity levels in seven patients with mild to moderate chronic heart failure. 2. Plasma human brain natriuretic peptide-like immunoreactivity levels were elevated in all patients (mean +/- SEM 22.0 +/- 6.2 pmol/l) compared with healthy control subjects (1.3 +/- 0.2 pmol/l, n = 11). 3. In all patients, candoxatril increased both plasma atrial natriuretic peptide (P less than 0.05) and plasma human brain natriuretic peptide-like immunoreactivity (P less than 0.05) levels. 4. By contrast, an exogenous infusion of atrial natriuretic peptide had no effect on plasma human brain natriuretic peptide-like immunoreactivity levels despite increasing the plasma atrial natriuretic peptide concentration to 424 +/- 74 pmol/l, which is a level of atrial natriuretic peptide which would have 'swamped' all atrial natriuretic peptide clearance receptors. 5. We have therefore shown that plasma human brain natriuretic peptide-like immunoreactivity levels in chronic heart failure are increased by a neutral endopeptidase inhibitor, but are unchanged by an exogenous infusion of atrial natriuretic peptide.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased elastase-alpha 1-antitrypsin complex in fulminant hepatic failure: relationship to bacterial infection and activation of coagulation.

To study the effect of infection, a frequent complication of fulminant hepatic failure (FHF), on the release of elastase from polymorphonuclear leucocytes and its inhibition in circulation we have measured the concentrations of alpha 1-antitrypsin, which binds and inhibits elastase in the circulation, and of elastase-alpha 1-antitrypsin complex, in 30 patients with FHF. Elastase-alpha 1-antitrypsin complex was significantly increased in FHF as compared to controls (303 +/- 51 micrograms/l compared to 37 +/- 5 micrograms/l; n = 10; P less than 0.001) demonstrating activation of leucocytes in FHF. Infection caused greater release of leucocyte elastase, complex levels were significantly greater in patients who were infected when compared to those who were not (463 +/- 84 micrograms/l; n = 13 compared to 180 +/- 46 micrograms/l; n = 17; P less than 0.01). Also patients who survived had significantly lower complex levels than those who did not (212 +/- 49 micrograms/l; n = 18 compared to 440 +/- 94 micrograms/l; n = 12; P less than 0.02). alpha 1-Antitrypsin activity was not significantly different from control subjects (0.99 +/- 0.06 U/ml compared to 0.97 +/- 0.05 U/ml). However alpha 1-antitrypsin activity was significantly higher in patients who survived (1.17 +/- 0.05 U/ml; n = 18) compared to those who did not (0.71 +/- 0.03 U/ml; n = 12; P less than 0.001) and patients who died had significantly lower levels than control subjects (P less than 0.01) indicating the importance of maintenance of normal inhibitor levels in patients with FHF. The leucocyte activation and release of elastase in FHF was linked to activation of the coagulation system; elastase--alpha 1-antitrypsin complex levels correlated significantly with thrombin-antithrombin III complex levels (r = 0.68; P less than 0.001) and inversely with fibrinogen (r = -0.71; P less than 0.001).     

Effect of hypophysectomy on caffeine elimination in rats

Two groups of 8-week-old Sprague-Dawley male rats were used: 8 hypophysectomized (H[-]), operated on day 0, treated by daily sc tetracosactid (ACTHs: 10 micrograms), and thyroxine (T4:5 micrograms/100 g); 7 sham-operated, treated by sc saline solution. ACTHs, T4, saline solution were administered on days 7-16. The animals received po caffeine (CAF) 4 mg/kg as citrate salt on day 15. Ten blood samples were drawn from the tail. Plasma CAF concentrations were determined by HPLC. CAF apparent clearance and apparent volume of distribution were lower in H(-) rats than in controls: 0.281 +/- 0.072 vs 0.455 +/- 0.165 l/kg/h (-38%; P less than 0.05) and 0.520 +/- 0.239 vs 1.28 +/- 0.266 l/kg (-59%; P less than 0.01) respectively. CAF half-life was lower in H(-) rats than in controls: 1.33 +/- 0.621 vs 2.12 +/- 0.676 h (-37%; P less than 0.01). CAF is a drug with a low hepatic extraction ratio and low plasma protein binding. CAF clearance is therefore primarily dependent on intrinsic clearance, which depends on the activity of the enzymes involved in CAF metabolism. These data suggest that hepatic CAF metabolism is reduced in H(-) rats treated by SC ACTHs and T4. The decrease in CAF apparent volume of distribution is probably related to dehydration, as suggested by increase in urine flow and hematocrit. The CAF half-life was probably low because the volume of distribution was proportionally more decreased than the clearance. Our results suggest that the pituitary gland plays a role in the regulation of hepatic CAF metabolizing enzymes.     

Intrinsic hepatic clearance of indocyanine green in the pig: Dependence on plasma protein concentration

Intrinsic hepatic clearance (K) of indocyanine green (ICG) is used as a quantitative measure of liver function. ICG is tightly bound to plasma proteins. The purpose of this study was to examine the effect of changes of plasma protein concentration on K in anaesthetized pigs with intact hepatic circulation. In addition, an attempt was made to evaluate the corresponding changes of the unbound intrinsic clearance of ICG. The plasma protein concentration was changed by exchange of plasma with either dextran-70 or donor pig plasma. Plasma albumin concentration was measured in a peripheral artery and changes of the concentrations of other plasma proteins were assumed to parallel those of albumin. ICG was given as a constant infusion and K was calculated from peripheral artery and hepatic vein concentrations of ICG according to the sinusoidal perfusion model. One experimental series comprised 3 measurement periods: From Period 1 to Period 2 (eight animals) albumin concentration was decreased by 36.6 +/- 6.5% (Mean +/- SD). This was associated with an increase of K of 32.8 +/- 28.8% (P = 0.004). From Period 2 to 3 (five animals) albumin was increased by 13.2 +/- 3.2% and K decreased by 18.5 +/- 8.3% (P = 0.03). In the second experimental series (eight animals), albumin concentration was increased by 21.6 +/- 10.3% and K decreased by 20.3 +/- 8.1% (P = 0.001). For both series, changes in albumin concentration were associated with oppositely directed changes of K in 20 out of 21 comparisons (P less than 0.001). Thus K depends not only on hepatocyte function but also on plasma protein concentration. This finding should affect interpretation of K when used as a liver function test. Changes of the unbound intrinsic clearance of ICG were examined indirectly by means of the K.a product (a: albumin concentration). According to the overall evaluation of the data the unbound intrinsic clearance of ICG was not affected by the changes in plasma protein concentration, but the results were internally inconsistent, apparently due to a time-dependency of the K.a product. We suggest this to be due to a slow but steady decrease of the 'background' K. After correction for the average decrease of K of 0.102% per min our data were in accordance with the hypothesis that the unbound clearance of K was enhanced by the binding protein(s) of ICG.