Platelet responses to intravenous infusion of Intralipid in healthy volunteers

Impact of lipid emulsions in parenteral nutrition on platelets: a literature review

Lipid emulsions are essential components of parenteral nutrition solutions that provide energy and essential fatty acids. The complexity of the formulations of lipid emulsions may lead to adverse outcomes such as platelet reactivity and changes in platelet aggregation and related coagulation. Platelets are responsible for haemostasis; they activate and demonstrate morphological changes upon extracellular factors to maintain blood fluidity and vascular integrity. Although parenteral nutrition lipid emulsions are generally found safe with regard to modulation of platelet activity, studies are still accumulating. Thus, this review aims to investigate platelet-related changes by parenteral nutrition lipid emulsions in human studies. Studies have pointed out patients at risk of bleeding and increased platelet aggregation responses due to the administration of lipid emulsions. Lipid emulsions may further benefit patients at high risk of thrombosis due to anti-thrombotic effects and should be cautiously used in patients with thrombocytopenia. The reported platelet-related changes might be associated with the fatty acid change in the plasma membranes of platelets following changes in platelet synthesis and plasma levels of eicosanoids. In conclusion, studies investigating platelets and parenteral nutrition should be supported to minimize the adverse effects and to benefit from the potential protective effects of parenteral nutrition lipid emulsions.

Platelet functional and transcriptional changes induced by intralipid infusion

Multiple studies have shown the effects of long-term exposure to high-fat or western diets on the vascular system. There is limited knowledge on the acute effects of high circulating fat levels, specifically on platelets, which have a role in many processes, including thrombosis and inflammation. This study investigated the effects of acute, high-fat exposure on platelet function and transcript profile. Twenty healthy participants were given an intravenous infusion of 20% Intralipid emulsion and heparin over 6 hours. Blood samples were taken prior to and the day after infusion to measure platelet function and transcript expression levels. Platelet aggregation was not significantly affected by Intralipid infusion, but, when mitochondria function was inhibited by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) or oligomycin, platelet aggregation was higher in the post-infusion state compared to baseline. Through RNA sequencing, and verified by RT-qPCR, 902 miRNAs and 617 mRNAs were affected by Intralipid infusion. MicroRNAs increased include miR-4259 and miR-346, while miR-517b and miR-517c are both decreased. Pathway analysis identified two clusters significantly enriched, including cell motility. In conclusion, acute exposure to high fat affects mitochondrial-dependent platelet function, as well as the transcript profile.

Intravenous lipids for preterm infants: a review

Extremely low birth weight infants (ELBW) are born at a time when the fetus is undergoing rapid intrauterine brain and body growth. Continuation of this growth in the first several weeks postnatally during the time these infants are on ventilator support and receiving critical care is often a challenge. These infants are usually highly stressed and at risk for catabolism. Parenteral nutrition is needed in these infants because most cannot meet the majority of their nutritional needs using the enteral route. Despite adoption of a more aggressive approach with amino acid infusions, there still appears to be a reluctance to use early intravenous lipids. This is based on several dogmas that suggest that lipid infusions may be associated with the development or exacerbation of lung disease, displace bilirubin from albumin, exacerbate sepsis, and cause CNS injury and thrombocytopena. Several recent reviews have focused on intravenous nutrition for premature neonate, but very little exists that provides a comprehensive review of intravenous lipid for very low birth and other critically ill neonates. Here, we would like to provide a brief basic overview, of lipid biochemistry and metabolism of lipids, especially as they pertain to the preterm infant, discuss the origin of some of the current clinical practices, and provide a review of the literature, that can be used as a basis for revising clinical care, and provide some clarity in this controversial area, where clinical care is often based more on tradition and dogma than science.

Comparison of coagulation and blood loss during anaesthesia with inhaled isoflurane or intravenous propofol

Propofol has been reported to affect blood coagulation. This prospective, randomized study compared coagulation and blood loss during anaesthetic maintenance with target-controlled intravenous propofol infusion vs. inhaled isoflurane. Thirty-eight ASA I-III patients undergoing head and neck surgery were allocated randomly to receive either inhaled isoflurane at end-tidal concentration 1-1.5% (group I, n=20) or target-controlled infusion (TCI) of propofol at target concentration 2-5 microg ml(-1) (group P, n=18). Thrombelastography on recalcified whole blood was performed pre-induction, and at 15, 30, 60, 90, 120 min post-induction and 30 min after anaesthesia in both groups. Blood loss was estimated from weighing swabs and the volume in suction bottles. Induced hypotension was not used, and perioperative body temperature was similar between groups. There were no significant differences in thrombelastographic coagulation (R-time, K-time, maximum amplitude and angle) or fibrinolytic variables (lysis index at 30 and 60 min) at all times between groups. Total blood loss was also not significantly different (median group I: 350 ml, range 20-1200 ml; group P: 200 ml, range 50-800 ml). Shortening of R-time and widening of angle developed over time in both groups (P<0.05 groups I and P, repeated measures ANOVA). We conclude that maintenance of anaesthesia with propofol TCI at 2-5 microg ml(-1) does not cause detectable coagulation changes on thrombelastography nor increase surgical blood loss when compared to inhaled isoflurane.

Lipid changes in plasma and blood cells following intravenous 10% fat infusion in man

The effects of a 500 ml 4 hr infusion of 10% fat emulsion (Lipovenös) on the lipid content of plasma lipoproteins and blood cells, and on the platelet aggregation rate, were studied in ten volunteers. The infusion resulted in a significant (P < 0.05) initial increase in plasma total triglycerides (more than 5 times), phospholipids (28.7%) and free cholesterol (43.3%), but a decrease in the free cholesterol content of erythrocytes and mononuclear cells (by 4.4% and by 22.7%, respectively). Plasma cholesteryl ester was reduced by 18.2% after the infusion, most of the reduction being accounted for by the 16.5% reduction in high-density lipoproteins. Our findings suggest more than 35% of the free cholesterol accumulated in plasma to derive from peripheral tissues, in turn suggesting overall reverse cholesterol transport from peripheral tissues to plasma to be enhanced. Post-infusion platelet aggregation in response to adenosine disphophate was significantly reduced, the peak rate by 31% and 1 min. rate by 20.6% (P < 0.05 in both cases). These changes in plasma lipids found in normal volunteers suggest that a short-term intravenous infusion of 10% Lipovenös might also be beneficial in preventing atherosclerosis.

Reduction of the plasma levels of tissue plasminogen activator after infusion of a lipid emulsion in humans

A lipid emulsion of soybean oil, egg lecithin, and glycerol, widely used as a standard component of parenteral nutrition regimens, has been reported to induce changes in some hemostatic parameters known to be associated with increased thrombotic risk. We studied the effect of a single infusion of this lipid emulsion (500 mL of a 10% emulsion, give over 5 to 6 hours) on the plasma levels of tissue plasminogen activator and plasminogen activator inhibitor 1 antigens in 12 patients with various diseases. Twelve matched patients, not treated with lipid, served as controls. In patients receiving the lipid emulsion, tissue plasminogen activator was markedly reduced at the end of the infusion (p < .001) and remained significantly lower than the basal levels 24 hours later (p < .05). By contrast, in control patients, the activator was slightly but significantly increased (p < .01) at the time interval corresponding to the postinfusion sample. Plasminogen activator inhibitor 1 was similar in control and treated patients at all intervals. The release of tissue plasminogen activator in response to 10 minutes of venous stasis, evaluated in six lipid-treated patients at the end of the infusion, was not different from that observed in six control patients. It is concluded that the lipid emulsion induces a marked decrease in the circulating levels of tissue plasminogen activator.