Based on volume-flow relationships, CNS agents that are highly lipid soluble (log octanol-water partition coefficient > 2) are expected to have equilibration half-times (T1/2 kE0) that are proportional to brain solubility. Propofol, the most lipophilic anaesthetic in clinical use, has T1/2 kE0 values of 1.7 and 2.9 min in rats and humans, respectively, compared with an expected value of at least 8 min. As a first step in exploring this discrepancy between observed and predicted values, we determined the steady state brain:plasma and brain:blood partition coefficients in rats after a 4-h infusion of propofol. Brain:plasma and brain:blood partition coefficients were 8.2 (SD 1.6) and 3.0 (0.5), respectively. T1/2 kE0 predictions based on brain: blood partitioning in rats are more in agreement with the observed equilibration half-time, suggesting that drug bound to the formed elements of blood participates in the uptake and transfer of propofol to its effect site.
A recently developed chromogenic endotoxin assay with plasma Tween 80 pretreatment was compared with the conventional dilution and heating method. Plasma endotoxin was measured in patients with liver cirrhosis and upper gastrointestinal (GI) bleeding by these methods. Plasma endotoxin concentration was calculated from an individual internal standard curve by adding three different standard endotoxin solutions to each sample. By the conventional heating method, added standard endotoxin gave different OD values in each sample and the slope of the standard curve showed interindividual variations. When sample plasma from chronic alcoholics was pretreated with 1% Tween 80 and ultrasonification after heating, the slope of standard curves was somewhat increased and interindividual variation was minimized. Significantly higher plasma endotoxin levels in cirrhotics with upper GI bleeding compared with those without upper GI bleeding was detected by this Tween 80 method. There was a strongly positive correlation between the endotoxin levels determined by this method and those determined by the perchloric acid method and endotoxin-specific substrate in patients with upper GI bleeding. Endotoxin levels, which were elevated 1-2 days after the bleeding, tended to decrease as patients recovered. In summary, the recovery of endogenous and exogenous endotoxin from plasma sample was increased by adding Tween 80 before the chromogenic substrate assay. Transient elevation of plasma endotoxin was demonstrated by this Tween 80 method in patients with liver cirrhosis and upper GI bleeding.
The endotoxin inactivating action of plasma was evaluated in 62 patients with cirrhosis and 10 healthy subjects. Endotoxin from E. coli 0111: B4 was added to each plasma sample to a final concentration of 250 pg/ml and the percentage loss of endotoxin activity by incubation (37°C for 1 h) was calculated as the endotoxin inactivating rate. The plasma endotoxin inactivating rate in cirrhotics was significantly greater than that in healthy subjects, although patients with Child C cirrhosis and marked hyperbilirubinemia had a significantly lower endotoxin inactivating rate than other cirrhotics. The plasma endotoxin inactivating rate was positively correlated to serum HDL‐cholesterol levels. In patients with Child A and Child B cirrhosis, the endotoxin inactivating rate was positively correlated to the endotoxin binding capacity of plasma albumin. The present results support the assumption that the plasma of cirrhotics has a high endotoxin inactivating capacity. Its decrease may augment endotoxicity in patients with advanced liver cirrhosis.
Plasma endotoxin levels in 12 cirrhotics with bleeding from oesophageal varices and 50 cirrhotics without bleeding were measured by the chromogenic assay after the pretreatment of sample by perchloric acid (HClO4) and triethylamine. Endotoxin in cirrhotics with bleeding from varices was significantly higher than those without bleeding. In patients with bleeding, endotoxin increased for 3 days after the bleeding, first in the supernatant fraction and then in the precipitate fraction by HClO4 treatment. Peak plasma alpha 1-acid glycoprotein and haptoglobin were observed 3 days after the bleeding. Alpha 1-antitrypsin gradually increased for 14 days. Transferrin did not markedly change. The endotoxin-binding capacity of transferrin and alpha 1-acid glycoprotein increased immediately after bleeding and thereafter decreased, but that of alpha 1-antitrypsin tended to increase in the recovery period. In summary, the plasma endotoxin concentration and endotoxin-binding capacity of alpha 1-acid glycoprotein and transferrin were shown to have increased after bleeding from varices by this new method. There may be a close relationship between endotoxaemia and acute phase reaction in this situation.
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