Benefits of Parenteral Lipid Emulsions in Acute Respiratory Failure

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Lipid emulsions in parenteral nutrition can interfere with pulmonary functions in patients displaying anomalies of the ventilation-perfusion ratio. The underlying mechanisms are unknown, but involve modifications of the production of vasoconstrictor and vasodilator eicosanoids as an effect of lipid infusion. Preferential synthesis of one or other of the eicosanoid types depends on the rate of administration of the lipids. Slow flow, corresponding to the administration of 100 g of triglycerides in 10-12 hours, leads to no change in the ventilation/perfusion ratio, and has no effect on gas exchange. TCM-based emulsions, which have little interference with eicosanoids, can be administered during ARDS. However, they have few benefits over a soy emulsion administered slowly. A new finding concerning lipid emulsions is the capacity of emulsions rich in long-chain polyunsaturated fatty acids of the n-3 series (DHA and EPA), derived from fish oil and of borage oil rich in gammalinoleic acid, to affect pulmonary inflammation and bronchial reactivity. These factors open up new and promising perspectives in the prevention and treatment of ARDS.

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Erythropoietin in the Critically Ill

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Introduction: Erythropoietin (EPO) is a recombinant human glycoprotein hormone that stimulates erythropoiesis. There is increasing experience in its use in management of anemia in the critically ill. Methods: This review focuses on clinical, experimental papers regarding erythropoietin usage in the critically ill from the Medline database. Data from our intensive care unit (ICU) were also included. Results: Anemia occurs commonly in the critically ill during ICU stay. Erythropoietin responses are blunted in MODS. EPO is an effective means of increasing haemoglobin and reduces blood transfusion. High doses 300-600U/kg of EPO produce erythropoietic responses within 6 days. For the general critical care patient, studies to date have not shown any increase in adverse events, nor any mortality benefit. Conclusion: Clinical indications include those in whom transfusion is difficult, such as Jehovah’s witnesses, or patients with antibodies. Data in the critically ill support the use of 600U/kg subcutaneously weekly for 4 weeks, with adjuvant therapy of oral iron 300mg/day, vitamin C 100mg/day, folate 5mg/day and possibly vitamin E. We recommend commencing when Hct is less than 30% in patients likely to remain in the ICU beyond one week. Patients should be monitored for hypertension and haemoglobin response. Erythropoietin use is now established as an efficacious, easy to use and safe method of treating anemia in the critically ill.

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Intra-Abdominal Hypertension ?EAn Intensive Care Perspective

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Introduction: Intra-abdominal hypertension isnow well recognized in intensive care patients. Increasing knowledge of the incidence, causes, pathophysiology and outcome of intra-abdominal hypertension has resulted in earlier and more definitive management of the condition in the last decade. Although these advances appear to have improved outcome, many issues remain controversial. Methods: A literature review of relevant papers was conducted. Conclusions: The incidence of intra-abdominal hypertension varies widely depending on the intra-abdominal pressure used to define the condition and the sub-group investigated. Monitoring intra-abdominal pressure by measuring urinary bladder pressure is simple and sufficiently accurate.

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Severe Acute Respiratory Syndrome

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Severe acute respiratory syndrome (SARS) is a new clinical entity which was first observed in Guangdong, China at the end of 2002. Since then there have been more than 7000 probable cases worldwide and more than 800 deaths. The difficulties of managing patients with this potentially fatal condition have been compounded by a lack of data relating to the condition and its highly infectious nature. Although the disease appears to have been brought under control, at least temporarily, a resurgence cannot be discounted and it is important that the medical community be prepared for this. This article summarizes current knowledge of SARS, with particular reference to Intensive Care. Where possible the information given is based on published data but there are no data specifically related to Intensive Care management and therefore some information is based on the opinion of the Intensive Care teams at the Prince of Wales Hospital and Tuen Mun Hospital, Hong Kong. It should be noted, however, that this is a rapidly evolving area of knowledge. Regularly updated information is available at http://www.aic.cuhk.edu.hk/web8.

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Assessment of Matrix Metalloproteinases-1 in Septic Acute

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The extracellular matrix (ECM) does not simply maintain the form of tissues; it is a dynamic factor that plays a major role in cell function. Matrix metalloproteinases (MMPs) are the most important enzymes in ECM degradation, and their activity is controlled strictly by specific inhibitors, that is tissue inhibitors of metalloproteinase (TIMPs). We assessed the clinical course of changes in ECM-degrading enzymes TNF-a, IL-6, IL-8, and nitrite/nitrate (NOx) in the blood of two septic acute respiratory distress syndrome (ARDS) patients. Negative correlation was found between the PaO2/FIO2 ratio (P/F ratio) and MMP-1, but positive correlation was found between the P/F ratio and both the TIMP-1/MMP-1 ratio and MMP-1 • TIMP-1 complex level. TIMP-1 was consistently maintained at high levels. These results suggest that both MMP-1 and TIMP-1 may be involved in septic ARDS, and that the balance between MMP-1 and TIMP-1 is important.

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Defibrillation

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For much of medical history, the precise mechanism of sudden cardiac arrest was assumed to be the abrupt cessation of activity in diastole. Not until the nineteenth century was ventricular fibrillation recognized as the causative entity, and not until the late twentieth were practical electrical defibrillators developed for terminating this dysrhythmia. Timely defibrillation is considered by many to be the most important single factor in successful cardiac arrest resuscitation. The likelihood of survival is directly related to the duration of cardiac arrest and the time that elapses before the first defibrillation attempt occurs. Over the past two decades, automatic external defibrillators have been developed and improved to provide more rapid defibrillation for victims of cardiac arrest. Their development has been considered the most important recent advance for improving outcome in out-of-hospital sudden death. The internal microprocessor-based system contained in the automatic defibrillator detects VF and prepares the machine to deliver a shock. It has been recommended that these devices be made available for use by basic rescue responders, lay bystanders with a minimal amount of training, and family members of high-risk patients. Public access defibrillation is increasingly seen as a logical extension of the automatic external defibrillator concept.

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Defibrillation

Authors:

For much of medical history, the precise mechanism of sudden cardiac arrest was assumed to be the abrupt cessation of activity in diastole. Not until the nineteenth century was ventricular fibrillation recognized as the causative entity, and not until the late twentieth were practical electrical defibrillators developed for terminating this dysrhythmia. Timely defibrillation is considered by many to be the most important single factor in successful cardiac arrest resuscitation. The likelihood of survival is directly related to the duration of cardiac arrest and the time that elapses before the first defibrillation attempt occurs. Over the past two decades, automatic external defibrillators have been developed and improved to provide more rapid defibrillation for victims of cardiac arrest. Their development has been considered the most important recent advance for improving outcome in out-of-hospital sudden death. The internal microprocessor-based system contained in the automatic defibrillator detects VF and prepares the machine to deliver a shock. It has been recommended that these devices be made available for use by basic rescue responders, lay bystanders with a minimal amount of training, and family members of high-risk patients. Public access defibrillation is increasingly seen as a logical extension of the automatic external defibrillator concept.

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Cytokines, NF-kB, Activated Protein C, Oxidized Phospholipids,

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Sepsis and septic shock are responsible for substantial morbidity and mortality in the intensive care units. NF-kB, macrophage migration inhibitory factor (MIF), tumor necrosis factor-a (TNF-a), interleukin-1 (IL-1), IL-6, reactive oxygen species, inducible nitric oxide (iNO), oxidized phospholipids, and eicosanoids play a significant role in the pathogenesis of sepsis and septic shock. Conversely, adenosine, activated protein C, oxidized phospholipids, w-3 fatty acids, some inducible cyclo-oxygenase products, and insulin show anti-inflammatory actions and have beneficial effects in sepsis and septic shock. Hence, it is suggested that combined use of some of these naturally occurring and endogenous anti-inflammatory compounds may be of significant benefit in sepsis and septic shock.

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Hyperchloremic Metabolic Acidosis and fluid Resuscitation

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Adequate fluid resuscitation is still a major treatment to optimize hemodynamics and to restore organ perfusion in the case of volume depletion. To achieve this goal, a wide variety of fluids are available to the clinician. Due to their different composition, the usual classification opposites crystalloids and colloids. Despite numerous studies, controversy still exists on the ideal fluid resuscitation. The trend to choose preferentially one or another during the last century has moved just like a pendulum. Acidosis as a consequence of fluid replacement is well known since more than 80 years ago. Initially, according to the classical Henderson-Hasselbalch approach, this disturbance was simply explained by a phenomenon of plasma bicarbonate dilution which was responsible for a proportional decreased pH. Consequently, acidosis has been called "dilutional acidosis". But, in the 1970s, Stewart described a new concept for the interpretation of acid-base equilibrium. In this approach, pH variations result from changes in 3 independent variables which are the strong ion difference (SID), the total charge in weak acids and the PaCO2. This concept emphasizes the implication of chloride and weak acids in acid-base equilibrium. Considering this approach, it is clear that the infusion of fluids containing high concentration of chloride leads to hyperchloremic metabolic acidosis. In this way, acidosis is not related to a simple dilution, but to the decreased SID which results totally from hyperchloremia. According this concept, crystalloids and colloids are now sub-classified into balanced or unbalanced categories. Balanced solutions are those that contain a concentration of chloride close to that of the plasma, whereas the unbalanced fluids are those characterized by a proportional high chloride concentration. Since about 10 years ago, normal saline, an unbalanced solution, remains the most popular choice of IV fluid. Due to its preferential administration, hyperchloremic metabolic acidosis is more and more frequently observed during the perioperative period and in critically ill patients. Numerous experimental and clinical trial have confirmed this phenomenon. Finally, whatever the exact mechanism, iatrogenic hyperchloremic metabolic acidosis produced by unbalanced expanders is now demonstrated. But, the real question is about the clinical relevant of potentially harmful effect of these changes, especially of hyperchloremia. Actually, the answer is not univocal. Only short-term infusion of unbalanced fluids has been studied, so that, only slight and transient hyperchloremic metabolic acidosis are described. Nevertheless, some recent data support transient postoperative cerebral, renal or digestive dysfunction in patients with hyperchloremia. A worsen outcome and a shorter survival time have been also found in experimental septic rats, long-term resuscitated with unbalanced solutions. However, these results need to be confirmed by further prospective randomized clinical trial of clinical outcome. In other words, present data which are still essentially biological modifications, cannot permit objectively to avoid totally or partially volume expansion with unbalanced solutions.

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Ventilation-Induced Lung Injury and Its Prevention

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The influence of detrimental forms of mechanical ventilation on the fluid balance across the alveolo-capillary barrier and its influence on the surfactant system have been extensively described in literature. Moreover, possible mechanisms by which such ventilation strategies exert systemic effects and effects on other organs are becoming increasingly realized. This paper describes the complications of detremental forms of mechanical ventilation and the physiological background to prevent such complications.

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