Role of fibrinogen in trauma-induced coagulopathy.

Coagulation defects related to severe trauma, trauma-induced coagulopathy (TIC), have a number of causal factors including: major blood loss with consumption of clotting factors and platelets, and dilutional coagulopathy after administration of crystalloids and colloids to maintain blood pressure. In addition, activation of the fibrinolytic system or hyperfibrinolysis, hypothermia, acidosis, and metabolic changes can also affect the coagulation system. All of these directly affect fibrinogen polymerization and metabolism. Other bleeding-related deficiencies usually develop later in massive bleeding related to severe multiple trauma. In major blood loss, fibrinogen reaches a critical value earlier than other procoagulatory factors, or platelets. The question of the critical threshold value is presently the subject of heated debate. A threshold of 100 mg dl(-1) has been recommended, but recent clinical data have shown that at a fibrinogen level of <150-200 mg dl(-1), there is already an increased tendency to peri- and postoperative bleeding. A high fibrinogen count exerts a protective effect with regard to the amount of blood loss. In multiple trauma patients, priority must be given to early and effective correction of impaired fibrin polymerization by administering fibrinogen concentrate.

Alteration of hepatic fatty acid metabolism after burn injury in pigs.

BACKGROUND: The primary goal of this study was to investigate hepatic fatty acid (FA) metabolism after severe thermal injury. METHODS: Sixteen pigs were divided into control (n = 8) and burn (n = 8, with 40% full thickness total body surface area burned) groups. Catheters were inserted in the right common carotid artery, portal vein, and hepatic vein for blood sampling. Flow probes were placed around the hepatic artery and portal vein for blood flow measurements. Animals were given pain medication and sedated until the tracer study on day 4 after burn. The pigs were infused for 4 hours with U-13C16-palmitate in order to quantify hepatic FA kinetics and oxidation. RESULTS: Liver triglyceride (TG) content was elevated from 162 +/- 16 (control) to 297 +/- 28 micromol TG/g dry liver wt. (p < .05). Hepatic FA uptake and oxidation were similar between the 2 groups, as were malonyl-coenzyme A (CoA) levels and activities of acetyl-CoA carboxylase and adenosine monophosphate (AMP)-activated protein kinase. In contrast, incorporation of plasma-free fatty acids into hepatic TG was elevated (p < .05) and very low density lipoprotein TG (VLDL-TG) secretion was decreased from 0.17 +/- 0.02 (control) to 0.03 +/- 0.01 micromol/kg per minute in burned pigs (p < .05). CONCLUSIONS: The accumulation of hepatic TG in burned animals is due to inhibition of VLDL-TG secretion and to increased synthesis of hepatic TG. Fatty acids are not channeled to TG because of impaired oxidation.

Surfactant phosphatidylcholine in thermally injured pigs.

OBJECTIVE: To investigate the effect of a thermal injury on pulmonary surfactant phosphatidylcholine kinetics. DESIGN: Random, controlled study. SETTING: University research laboratory. SUBJECTS: Yorkshire swine (n = 8) with and without a 40% total body surface area burn. INTERVENTIONS: A new isotope tracer methodology was used to quantify surfactant phosphatidylcholine kinetics. Four days after burn, [1,2-13C2]acetate and [U-(13)C16]palmitate were infused continuously for 8 hrs to quantify surfactant phosphatidylcholine synthesis, secretion, recycling, and irreversible loss. MEASUREMENTS AND MAIN RESULTS: The total surfactant phosphatidylcholine pool size was reduced from the control value of 2.65 +/- 0.05 to 1.61 +/- 0.08 micromol/g wet lung in burned animals (p <.05), as was the proportional contribution of palmitate to lung surfactant phosphatidylcholine composition. This reduction was associated with a significant decrease in lung dynamic compliance from the control value of 66 +/- 6 to 55 +/- 6 mL/cm H2O for burned pigs (p <.05). The most prominent response of lung phosphatidylcholine kinetics was a decrease in the total lung phosphatidylcholine synthesis from a control value of 12.7 +/- 1.2 to 5.5 +/- 0.3 nmol phosphatidylcholine-bound palmitate x hr(-1) x g of wet lung(-1) in burned animals (p<.05). CONCLUSIONS: Pulmonary phosphatidylcholine content and palmitate composition decrease after burn injury because of a decrease in the rate of phosphatidylcholine synthesis. These responses likely contribute to impaired lung compliance.

Caval backflow: a potential problem during blood sampling from the hepatic vein.

A proper measurement of splanchnic metabolism involves sampling blood from the hepatic vein without backflow contamination of blood from the caval vein. We have investigated the potential problem of caval backflow in human volunteers with an indwelling hepatic vein catheter by sampling blood with different amounts of suction on the syringe (ie, sampling speeds). We also investigated the potential problem in pigs in which a balloon catheter was inserted in the hepatic vein. Pure hepatic vein samples were obtained with the balloon inflated and compared with samples obtained from the same catheter in the conventional manner. In overnight fasted humans, drawing blood samples from the hepatic vein with minimal suction ("slow" drawing) resulted in glucose values 9.6% higher than drawing the samples with greater suction ("fast" drawing). The calculated arterial-venous balance across the splanchnic bed was 4.8 times greater with "slow" blood drawing as compared with "fast" drawing. Values obtained from the pigs showed no concentration differences between pure hepatic vein samples and "slow" drawing from the hepatic vein. The current study indicates that it is possible to obtain a "true" hepatic vein sample, but backflow from the caval vein is a potential pitfall that can have a physiologically significant impact on calculated balance data.

Glucose effects on lung surfactant kinetics in conscious pigs.

The primary goal of this study was to investigate the effects of glucose infusion on surfactant phosphatidylcholine (PC) metabolic kinetics in the lungs. A new stable isotope tracer model was used in which [1,2-(13)C(2)]acetate and uniformly labeled [U-(13)C(16)]palmitate were infused in 12 normal overnight-fasted pigs to quantify lung surfactant kinetics with or without glucose infusion (24 mg. kg(-1). min(-1)). With glucose infusion, the rate of surfactant PC incorporation from de novo synthesized palmitate increased from the control value of 2.1 +/- 0.2 to 15.5 +/- 1.9 nmol PC-bound palmitate. h(-1). g wet lung(-1) (P < 0.05), whereas the incorporation rate from plasma preformed palmitate decreased from the control value of 20.9 +/- 1.9 to 11.6 +/- 1.1 nmol palmitate. h(-1). g wet lung(-1) (P < 0.05). The palmitate composition in lamellar body surfactant PC increased from the control value of 61.7 +/- 2.1% to 75.9 +/- 0.6% (P < 0.05). The surfactant PC secretion rate decreased from the control value of 239.0 +/- 26.1 to 81.9 +/- 5.3 nmol PC-bound palmitate. h(-1). g wet lung(-1) (P < 0.05). We conclude that, whereas surfactant secretion was inhibited by glucose infusion, neither total surfactant PC synthesis nor the surfactant PC pool size was significantly affected due to an increased reliance on de novo synthesized fatty acids.

Changes in intermediary metabolism in severe surgical illness.

Under normal circumstances there is a reciprocal relation between the availability of free fatty acids (FFAs) and glucose in plasma. In the fasted state, FFAs predominate in both availability and the relative contribution to energy production, whereas the same is true for glucose in the fed state. The extent of glucose oxidation is directly determined by its availability, whereas FFAs are normally available well in excess of their rate of oxidation. The rate of FFA oxidation is determined by the rate of transfer into the mitochondria via the carnitine palmitoyltransferase (CPT) enzyme system, which in turn is regulated by the metabolism of glucose. With critical illness the stress response involves mobilization of both plasma glucose and FFAs simultaneously in both the fed and fasted states. In the situation of excess availability of substrates, the metabolism of glucose limits the oxidation of FFAs, thereby channeling those fatty acids into triglyceride (TG) stores in the muscle and the liver. The high FFA concentrations and increased tissue TG stores can limit glucose clearance from the blood, thereby contributing to the development of hyperglycemia. Also, the excessive metabolism of glucose can result in lacticacidemia and can contribute to the depletion of muscle glutamine. The nutritional treatment of such patients must account for these underlying metabolic responses to avoid amplifying potentially detrimental responses to the excess availability of substrates already present in the fasting state.

Lung surfactant kinetics in conscious pigs.

The primary goal of this study was to determine the contributions of plasma free fatty acids (FFA) and de novo synthesized fatty acids (FA) to lung surfactant phosphatidylcholine (PC) synthesis. A new stable isotope tracer model was developed in which [1, 2-(13)C(2)]acetate and uniformly labeled [U-(13)C(16)]palmitate were infused in nine normal overnight fasted pigs to quantify surfactant kinetics in the basal state and during low-dose glucose infusion (2 mg. kg(-1). min(-1)). There was no effect of glucose; therefore, all data were pooled. The surfactant PC-bound palmitate incorporation rate from plasma palmitate was 20.9 +/- 1.9 nmol palmitate. h(-1). g wet lung(-1), compared with the rate of 2.1 +/- 0.3 nmol palmitate. h(-1). g wet lung(-1) from de novo synthesized palmitate. The PC-bound palmitate secretion rate from the lamellar body pool to the alveolar surface pool was 239 +/- 26 nmol palmitate. h(-1). g wet lung(-1). Approximately 90% of the secreted PC recycled back to the lamellar bodies for reutilization. We conclude that plasma is the primary contributor of FA for surfactant PC synthesis under the conditions of this experiment.

Coronary reactive hyperaemia after nitric oxide inhibition in the anaesthetized goat.

In the dog it has been shown that, while the inhibition of the endothelial release of nitric oxide reduces the duration, the total hyperaemic flow and the peak flow of the acetylcholine and myogenic coronary vasodilator responses, in the reactive hyperaemia the peak is not affected. The difference has been attributed to the different time required by the coronary blood flow to reach its maximum: long enough when acetylcholine is given or myogenic vasodilatation is elicited, this time is very short in the reactive hyperaemia. Thus it has been argued that only when the time to the peak of a hyperaemic response is sufficiently long, the increased shear stress acting on the coronary endothelium at the beginning of the hyperaemia can enhance the maximum value of the vasodilatation. Such an effect is impaired by NO-inhibition. Since in the goat the time to the peak of the coronary reactive hyperaemia is much longer than in the dog (10-14 s vs 3-4 s), the present study aimed at investigating whether the same effect caused by the NO-inhibition on the maximum flow of the acetylcholine and myogenic hyperaemic responses in the dog, can also be obtained in the goat for the peak flow of the coronary reactive hyperaemia. Experiments performed in anaesthetised goats showed that NO-inhibition reduces the duration of the reactive hyperaemia without affecting the maximum hyperaemic flow. It is suggested that in the reactive hyperaemia the large predominance of metabolic factors prevents the shear stress from playing a role in enhancing the peak flow.

Partial Bochdalek's herniation; computerized tomographic evaluation.

The advent of computerized tomographic scanning has provided an accurate and noninvasive method for the diagnosis of suspected, small, partial diaphragmatic herniations.