Impact of sepsis, lung injury, and the role of lipid infusion on circulating prostacyclin and thromboxane A(2)

Clinical Nutrition in Critical Care Medicine - Guideline of the German Society for Nutritional Medicine (DGEM)

PURPOSE

Enteral and parenteral nutrition of adult critically ill patients varies in terms of the route of nutrient delivery, the amount and composition of macro- and micronutrients, and the choice of specific, immune-modulating substrates. Variations of clinical nutrition may affect clinical outcomes. The present guideline provides clinicians with updated consensus-based recommendations for clinical nutrition in adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function.

METHODS

The former guidelines of the German Society for Nutritional Medicine (DGEM) were updated according to the current instructions of the Association of the Scientific Medical Societies in Germany (AWMF) valid for a S2k-guideline. According to the S2k-guideline classification, no systematic review of the available evidence was required to make recommendations, which, therefore, do not state evidence- or recommendation grades. Nevertheless, we considered and commented the evidence from randomized-controlled trials, meta-analyses and observational studies with adequate sample size and high methodological quality (until May 2018) as well as from currently valid guidelines of other societies. The liability of each recommendation was described linguistically. Each recommendation was finally validated and consented through a Delphi process.

RESULTS

In the introduction the guideline describes a) the pathophysiological consequences of critical illness possibly affecting metabolism and nutrition of critically ill patients, b) potential definitions for different disease phases during the course of illness, and c) methodological shortcomings of clinical trials on nutrition. Then, we make 69 consented recommendations for essential, practice-relevant elements of clinical nutrition in critically ill patients. Among others, recommendations include the assessment of nutrition status, the indication for clinical nutrition, the timing and route of nutrient delivery, and the amount and composition of substrates (macro- and micronutrients); furthermore, we discuss distinctive aspects of nutrition therapy in obese critically ill patients and those treated with extracorporeal support devices.

CONCLUSION

The current guideline provides clinicians with up-to-date recommendations for enteral and parenteral nutrition of adult critically ill patients who suffer from at least one acute organ dysfunction requiring specific drug therapy and/or a mechanical support device (e.g., mechanical ventilation) to maintain organ function. The period of validity of the guideline is approximately fixed at five years (2018-2023).

Systematic review of clinical adverse events reported after acute intravenous lipid emulsion administration

BACKGROUND

Intravenous lipid emulsions (ILEs) were initially developed to provide parenteral nutrition. In recent years, ILE has emerged as a treatment for poisoning by local anesthetics and various other drugs. The dosing regimen for the clinical toxicology indications differs significantly from those used for parenteral nutrition. The evidence on the efficacy of ILE to reverse acute toxicity of diverse substances consists mainly of case reports and animal experiments. Adverse events to ILE are important to consider when clinicians need to make a risk/benefit analysis for this therapy.

METHODS

Multiple publication databases were searched to identify reports of adverse effects associated with acute ILE administration for either treatment of acute poisoning or parenteral nutrition. Articles were selected based on pre-defined criteria to reflect acute use of ILE. Experimental studies and reports of adverse effects as a complication of long-term therapy exceeding 14 days were excluded.

RESULTS

The search identified 789 full-text articles, of which 114 met the study criteria. 27 were animal studies, and 87 were human studies. The adverse effects associated with acute ILE administration included acute kidney injury, cardiac arrest, ventilation perfusion mismatch, acute lung injury, venous thromboembolism, hypersensitivity, fat embolism, fat overload syndrome, pancreatitis, extracorporeal circulation machine circuit obstruction, allergic reaction, and increased susceptibility to infection.

CONCLUSION

The emerging use of ILE administration in clinical toxicology warrants careful attention to its potential adverse effects. The dosing regimen and context of administration leading to the adverse events documented in this review are not generalizable to all clinical toxicology scenarios. Adverse effects seem to be proportional to the rate of infusion as well as total dose received. Further safety studies in humans and reporting of adverse events associated with ILE administration at the doses advocated in current clinical toxicology literature are needed.

Sepsis-associated changes of the arachidonic acid metabolism and their diagnostic potential in septic patients

OBJECTIVES

Sepsis-associated changes of the arachidonic acid metabolism and the utility of arachidonic acid metabolites for the diagnosis of sepsis have been poorly investigated so far. Therefore, the primary objective of our study was to screen for differentially regulated arachidonic acid metabolites in septic patients using a lipopolysaccharide whole-blood model and to investigate their diagnostic potential.

DESIGN

Prospective, observational, single-center, clinical study.

SETTING

Intensive care unit at University Hospital Leipzig.

PATIENTS

Thirty-five patients (first cohort 25 patients, second cohort 10 patients) meeting the criteria for severe sepsis or septic shock were enrolled. Eighteen healthy volunteers (first cohort 15 subjects, second cohort 3 subjects) were enrolled as controls.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Arachidonic acid and its metabolites were investigated in supernatants of nonactivated (baseline) and lipopolysaccharide-activated heparinized whole blood of healthy subjects (n=15) and septic patients (n=25) by solid phase extraction and subsequent liquid chromatography-tandem mass spectrometry. Arachidonic acid, arachidonic acid analogues, and the cyclooxygenase-associated metabolites prostaglandin E2, 11-hydroxyeicosatetraenoic acid, and thromboxane B2 were identified as differentiating metabolites between septic patients and healthy subjects. Some of these compounds, including arachidonic acid, its analogues, and the cyclooxygenase metabolites prostaglandin E2 and thromboxane B2 differed at baseline. The inducibility of arachidonic acid and the cyclooxygenase metabolites 11-hydroxyeicosatetraenoic and prostaglandin E2 were reduced by 80% to 90% in septic patients. The degree of the inducibility was associated with severity of sepsis and clinical outcome. A reduced inducibility of COX-2 but preserved inducibility of mPGES-1 on gene expression level were confirmed in an independent cohort of septic patients (n=10) by quantitative reverse-transcription polymerase chain reaction compared to healthy controls (n=3).

CONCLUSIONS

Arachidonic acid metabolism is markedly affected in patients with sepsis. Our data suggest that the analysis of arachidonic acid metabolites in an in vitro whole blood activation model may be a promising approach for risk estimation in septic patients that has to be further evaluated in subsequent large-scale clinical studies.

CRTH2 is a critical regulator of neutrophil migration and resistance to polymicrobial sepsis

Although arachidonic acid cascade has been shown to be involved in sepsis, little is known about the role of PGD(2) and its newly found receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), on the septic response. Severe sepsis is associated with the failure of neutrophil migration. To investigate whether CRTH2 influences neutrophil recruitment and the lethality during sepsis, sepsis was induced by cecal ligation and puncture (CLP) surgery in mice. CRTH2 knockout (CRTH2(-/-)) mice were highly resistant to CLP-induced sepsis, which was associated with lower bacterial load and lower production of TNF-α, IL-6, and CCL3. IL-10, an anti-inflammatory cytokine, was higher in CRTH2(-/-) mice, blunting CLP-induced lethality in CRTH2(-/-) mice. Neutrophil accumulation in the peritoneum was more pronounced after CLP in CRTH2(-/-) mice, which was associated with higher CXCR2 levels in circulating neutrophils. Furthermore, sepsis caused a decrease in the level of acetylation of histone H3, an activation mark, at the CXCR2 promoter in wild-type neutrophils, suggesting that CXCR2 expression levels are epigenetically regulated. Finally, both pharmacological depletion of neutrophils and inhibition of CXCR2 abrogated the survival benefit in CRTH2(-/-) mice. These results demonstrate that genetic ablation of CRTH2 improved impaired neutrophil migration and survival during severe sepsis, which was mechanistically associated with epigenetic-mediated CXCR2 expression. Thus, CRTH2 is a potential therapeutic target for polymicrobial sepsis.

Fish oil in critical illness: mechanisms and clinical applications

Fish oil is rich in omega-3 fatty acids, which have been shown to be beneficial in multiple disease states that involve an inflammatory process. It is now hypothesized that omega-3 fatty acids may decrease the inflammatory response and be beneficial in critical illness. After a review of the mechanisms of omega-3 fatty acids in inflammation, research using enteral nutrition formulas and parenteral nutrition lipid emulsions fortified with fish oil were examined. The results of this research to date are inconclusive for both enteral and parenteral omega-3 fatty acid administration. More research is required before definitive recommendations can be made on fish oil supplementation in critical illness.

Omega-3 fatty acids in critical illness

Supplementation of enteral nutritional formulas and parenteral nutrition lipid emulsions with omega-3 fatty acids is a recent area of research in patients with critical illness. It is hypothesized that omega-3 fatty acids may help reduce inflammation in critically ill patients, particularly those with sepsis and acute lung injury. The objective of this article is to review the data on supplementing omega-3 fatty acids during critical illness; enteral and parenteral supplemental nutrition are reviewed separately. The results of the research available to date are contradictory for both enteral and parenteral omega-3 fatty acid administration. Supplementation with omega-3 fatty acids may influence the acute inflammatory response in critically ill patients, but more research is needed before definitive recommendations about the routine use of omega-3 fatty acids in caring for critically ill patients can be made.

Lipid emulsions - Guidelines on Parenteral Nutrition, Chapter 6

The infusion of lipid emulsions allows a high energy supply, facilitates the prevention of high glucose infusion rates and is indispensable for the supply with essential fatty acids. The administration of lipid emulsions is recommended within ≤7 days after starting PN (parenteral nutrition) to avoid deficiency of essential fatty acids. Low-fat PN with a high glucose intake increases the risk of hyperglycaemia. In parenterally fed patients with a tendency to hyperglycaemia, an increase in the lipid-glucose ratio should be considered. In critically ill patients the glucose infusion should not exceed 50% of energy intake. The use of lipid emulsions with a low phospholipid/triglyceride ratio is recommended and should be provided with the usual PN to prevent depletion of essential fatty acids, lower the risk of hyperglycaemia, and prevent hepatic steatosis. Biologically active vitamin E (α-tocopherol) should continuously be administered along with lipid emulsions to reduce lipid peroxidation. Parenteral lipids should provide about 25–40% of the parenteral non-protein energy supply. In certain situations (i.e. critically ill, respiratory insufficiency) a lipid intake of up to 50 or 60% of non-protein energy may be reasonable. The recommended daily dose for parenteral lipids in adults is 0.7–1.3 g triglycerides/kg body weight. Serum triglyceride concentrations should be monitored regularly with dosage reduction at levels >400 mg/dl (>4.6 mmol/l) and interruption of lipid infusion at levels >1000 mg/dl (>11.4 mmol/l). There is little evidence at this time that the choice of different available lipid emulsions affects clinical endpoints.

Effects of bolus injection of soybean-based fat emulsion and fatty acids on pulmonary gas exchange function

To determine whether or not a "bolus injection" of soybean-based fat emulsion (SFE), which contains oleic acid (OA), a potent lung-toxic unsaturated C-18 fatty acid, can induce pulmonary dysfunction, we examined the effect of SFE injection on the partial oxygen pressure of arterial blood (Pao2) and pulmonary vascular permeability. In addition, we compared the effect of an injection of SFE with that of OA, soybean oil (a source of SFE), emulsified OA and C-18 fatty acids. Bolus injection of SFE (0.3-4.8 ml/kg) had little effect on Pao2) and pulmonary vascular permeability. Injection of an equivalent amount of OA, on the other hand, significantly decreased Pao2 and increased pulmonary vascular hyper-permeability. This decrease in Pao2 was attenuated by emulsification. Unemulsified soybean oil also induced a decrease in Pao2, although the effect was weaker than that of OA. Other unsaturated C-18 fatty acids (linoleic and linolenic acid) induced a decrease in Pao2 as potent as OA while stearic acid, a C-18 saturated fatty acid, had little effect. Although we did not observe pulmonary toxicity as a result of "bolus injection" of SFE, the chemical form, for example, emulsification and the degree of saturability of the carbon chain, seems to influence the pulmonary toxicities of lipids and fatty acids. Furthermore, the potent pulmonary toxicity of OA seems to depend not only on pulmonary vascular embolization but also pharmacological and/or inflammation-inducing properties.

Effect of short-term intralipid infusion on the immune response during low-dose endotoxemia in humans

Novel anti-inflammatory effects of insulin have recently been described, and insulin therapy to maintain euglycemia suppresses the plasma levels of free fatty acids (FFA) and increases the survival of critically ill patients. We aimed to explore the effect of short-term high levels of plasma FFA on the inflammatory response to a low dose of endotoxin. Fourteen healthy male volunteers underwent the following two trials in a randomized crossover design: 1) continuous infusion of 20% Intralipid [0.7 ml.kg(-1).h(-1) (1.54 g/kg)] for 11 h, and 2) infusion of isotonic saline for 11 h (control). In each trial, heparin was given to activate lipoprotein lipase, and an intravenous bolus of endotoxin (0.1 ng/kg) was given after 6 h of Intralipid/saline infusion. Blood samples and muscle and fat biopsies were obtained before the Intralipid/saline infusion and before as well as after infusion of an endotoxin bolus. Plasma levels of FFA, triglycerides, and glycerol were markedly increased during the Intralipid infusion. Endotoxin exposure induced an increase in plasma levels of TNF-alpha, IL-6, and neutrophils and further stimulated gene expression of TNF-alpha and IL-6 in both skeletal muscle and adipose tissue. The systemic inflammatory response to endotoxin was significantly pronounced during Intralipid infusion. Short-term hyperlipidemia enhances the inflammatory response to endotoxin, and skeletal muscle and adipose tissue are capable of producing essential inflammatory mediators after endotoxin stimulation.

Benefit of an enteral diet enriched with eicosapentaenoic acid and gamma-linolenic acid in ventilated patients with acute lung injury*

OBJECTIVE

To explore the effects of an enteral diet enriched with eicosapentaenoic acid (EPA), gamma-linolenic acid (GLA), and antioxidants on the respiratory profile and outcome of patients with acute lung injury.

DESIGN

Single-center, prospective, randomized, controlled, unblinded study.

SETTING

General intensive care department of a tertiary-care, university-affiliated hospital.

PATIENTS

A total of 100 patients with acute lung injury, diagnosed according to the American-European Consensus Conference on ARDS.

INTERVENTIONS

Patients were randomized to receive the standard isonitrogenous, isocaloric enteral diet or the standard diet supplemented with EPA and GLA for 14 days.

MEASUREMENTS AND MAIN RESULTS

Patient demographics, Acute Physiology and Chronic Health Evaluation II score, and type of admission were noted at admission. Compared with baseline oxygenation (EPA + GLA group vs. control group), by days 4 and 7, patients receiving the EPA + GLA diet showed significant improvement in oxygenation (PaO(2)/FIO(2), 317.3 +/- 99.5 vs. 214.3 +/- 56.4 and 296.5 +/- 165.3 vs. 236.3 +/- 79.8, respectively; p < .05). Compliance was significantly higher in the EPA + GLA group observed at day 7 (55.1 +/- 46.5 vs. 35.2 +/- 20.0 mL/mbar, p < .05). No significant difference was found in nutritional variables. Resting energy expenditure was significantly higher in patients in the EPA + GLA group, but their body mass index was also higher (p < .05). A significant difference was found in length of ventilation (p < .04) in favor of the EPA + GLA group. There was no between-group difference in survival.

CONCLUSIONS

In patients with acute lung injury, a diet enriched with EPA + GLA may be beneficial for gas exchange, respiratory dynamics, and requirements for mechanical ventilation.

Partial liquid ventilation with FC-77 suppresses the release of lipid mediators in rat acute lung injury model

OBJECTIVE

To investigate whether the release of lipid mediators is suppressed in rats with experimentally induced acute lung injury managed with partial liquid ventilation (PLV) using FC-77.

DESIGN

Prospective, randomized controlled study.

SETTING

Research laboratory in a university.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

After tracheostomy was performed under general anesthesia, lung injury was induced by intratracheal instillation of HCl. The PLV group was then subjected to conventional gas ventilation for 30 mins, followed by PLV using FC-77. The control group was subjected to conventional gas ventilation throughout the study period.

MEASUREMENTS AND MAIN RESULTS

In the PLV group the following results were obtained: a) impaired oxygenation was markedly improved; b) the increase in the serum levels of lipid mediators such as leukotriene B4, thromboxane A2, and 6-keto-prostaglandin F1alpha was suppressed; and c) the increase in the concentrations of leukotriene B4, thromboxane A2, and 6-keto-prostaglandin F1alpha in the total lung homogenate at 180 mins after lung injury was also suppressed.

CONCLUSION

This study indicates that PLV using FC-77 suppresses the release of lipid mediators in our rat model of acute lung injury. However, further investigation is needed to clarify the precise mechanism of this effect.

Effect of a Novel Thromboxane A2 Inhibitor on Right Ventricular-Arterial Coupling in Endotoxic Shock

We investigated the effects of a dual thromboxane (TX)A2 synthase inhibitor and TXA2 receptor antagonist (BM-573) on right ventricular-arterial coupling in a porcine model of endotoxic shock. Thirty minutes before the onset of 0.5 mg/kg endotoxin infusion, six pigs (Endo group) received an infusion with a placebo solution, and six other pigs (Anta group) with BM-573. Right ventricular pressure-volume loops were obtained by the conductance catheter technique. The slope (Ees) of the end-systolic pressure-volume relationship and its volume intercept at 25 mmHg were calculated as measures of right ventricular systolic function. RV afterload was quantified by pulmonary arterial elastance (Ea), and Ees/Ea ratio represented right ventricular-arterial coupling. Mechanical efficiency was defined as the ratio of stroke work and pressure-volume area. In this model of endotoxic shock, BM-573 blunted the early phase of pulmonary hypertension, improved arterial oxygenation, and prevented a decrease in right ventricular myocardial efficiency and right ventricular dilatation. However, the drug could not prevent the loss of homeometric regulation and alterations in right ventricular-arterial coupling. In conclusion, dual TXA2 synthase inhibitor and receptor antagonists such as BM-573 have potential therapeutic applications, improving right ventricular efficiency and arterial oxygenation in endotoxic shock.

Propofol does not induce pulmonary dysfunction in stressed endotoxic pigs receiving Intralipid

OBJECTIVE

To assess the effect of diisopropyl phenol (propofol), with and without Intralipid, on the cardiopulmonary system and on thromboxane production in endotoxic pigs.

DESIGN

Prospective, randomized animal study.

SETTING

Animal research laboratory at a major teaching hospital.

SUBJECTS

Twenty-four pigs, divided into three groups (n = 8).

INTERVENTIONS

Pulmonary arterial catheters and arterial cannulas were inserted into all pigs. Each pig received a 30 ng/kg bolus of endotoxin at 1 hr, followed by a continuous infusion of endotoxin at 24 ng x kg-1 x hr-1. Diisopropyl phenol at 25, 75, and 200 microg x kg-1 x min-1 was administered to all pigs, beginning at 1, 2, and 3 hrs, respectively. The pigs were divided into three groups to receive 0.25 g x kg-1 x hr-1, 0.08 g x kg-1 x hr-1, or no Intralipid, starting at time t = 0. Heart rate and mean arterial, central venous, and pulmonary arterial pressures were recorded continuously. Core temperature, arterial blood gases, mixed venous oxygen saturation, pulmonary arterial occlusion pressure, and cardiac output were measured intermittently. Thromboxane B(2) concentrations were measured at baseline and at 60, 75, 120, 135, 180, 195, and 240 mins. Data are expressed as mean +/- sd. Groups were compared by using repeated analysis of variance, with p <.05 used for statistical significance.

MEASUREMENTS AND MAIN RESULTS

All pigs completed the 4-hr study. Marked variabilities were noted for individual pigs. Following the infusion of endotoxin, compared with baseline, there was a significant increase in pulmonary vascular resistance and a decrease in Pao(2) (p <.001 and p <.008, respectively). This response was not affected by the increasing dose of diisopropyl phenol, nor were there differences between the Intralipid and control groups. Pao(2) remained significantly lower in all groups, compared with the baseline measurements (p <.001) over the 4 hrs of the experiment. Thromboxane B(2) concentrations remained elevated compared with baseline and were significantly higher (p <.05) in the high-dose Intralipid group, compared with the low-dose and the control groups, during the last hour of the experiment.

CONCLUSIONS

Small doses of endotoxin, when given to pigs, induce major perturbations of cardiopulmonary function. Neither Intralipid, high vs. low dose, nor diisopropyl phenol, at sedating vs. anesthetizing doses, worsened the physiologic derangement associated with the stress of low-dose endotoxemia.

Effects of BM-573, a novel thromboxane A2 inhibitor, on pulmonary hemodynamics in endotoxic shock

Thromboxane A2 is considered to be partially responsible for the increase in pulmonary vascular resistance observed after endotoxin administration and to participate in proinflammatory reactions. The effects of a novel dual TXA2 synthase inhibitor and TXA2 receptor antagonist (BM-573) on pulmonary hemodynamics were investigated in endotoxic shock. 30 mins before the start of a 0.5 mg/kg endotoxin infusion, 6 pigs (Endo group) received a placebo infusion and 6 other pigs (Anta group) received a BM-573 infusion. In Endo group, pulmonary artery pressure increased from 25 +/- 1.8 (T0) to 42 +/- 2.3 mmHg (T60) (p < 0.05) after endotoxin infusion while, in Anta group, it increased from 23 +/- 1.6 (T0) to 25 +/- 1.5 mmHg (T60). This difference is due to a reduction in pulmonary vascular resistance in Anta group while pulmonary arterial compliance changes in Endo group remained comparable with the evolution in Anta group. In Endo group, PaO2 decreased from 131 +/- 21 (T0) to 74 +/- 12 mmHg (T300) (p < 0.05), while in Anta group, PaO2 was 241 +/- 31 mmHg at the end of the experimental period (T300). These results demonstrate that TXA2 plays a major role in pulmonary vascular changes during endotoxin insult. Concomitant inhibition of TXA2 synthesis and of TXA2 receptors by BM-573 inhibited the pulmonary vasopressive response during the early phase of endotoxin shock as well as the deterioration in arterial oxygenation.

Effect of estradiol administration on splanchnic perfusion after trauma-hemorrhage and sepsis

PURPOSE OF REVIEW

This review focuses on the latest mechanistic understanding of the effects of estradiol on the splanchnic circulation and the possibility of estradiol treatment as an adjunct for the treatment of trauma-hemorrhage and sepsis.

RECENT FINDINGS

Systemic hypotension induced by shock accompanies marked alterations in blood flow to various organs. Decreased splanchnic perfusion is frequently observed after insults, such as severe hemorrhage or sepsis, which leads to the destruction of the intestinal mucosal barrier and hepatic dysfunction. Studies suggest that estradiol acts as a facilitator of the intestinal blood flow via the increased production of nitric oxide, decreased production of vasoconstrictors, attenuated neutrophil adhesion, and decreased formation of oxygen free radicals.

SUMMARY

Trauma-hemorrhage results in decreased circulating blood volume. In contrast, sepsis is an inflammatory state mainly mediated by bacterial products. However, these divergent insults show similar pathophysiologic alterations in terms of the splanchnic circulation. Because estradiol effectively protects the organs from circulatory failure after various adverse circulatory conditions, many studies are being performed to clarify the molecular mechanism of estradiol action with regard to tissue circulation. Estradiol improves the macro- and microcirculation of the splanchnic organs by multiple mechanisms. Nonetheless, it remains unclear which mechanism plays the most important role in the treatment of trauma-hemorrhage and sepsis. Additional studies are required to elucidate the precise mechanism of estradiol action and to determine the usefulness of estradiol treatment for severe hemorrhage and sepsis in patients.