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2018, Critical Care
https://doi.org/10.1186/S13054-018-1973-5…
215 pages
1 file
Fig. 1 (abstract P001). Cellular metabolism as measured in oxygen consumption rate (OCR) (n = 4). Basal denotes energetic demand of the cell under baseline condition; spare respiratory capacity denotes the capability of the cell to respond to energetic demand; proton leak denotes remaining basal respiration not coupled to ATP production, can be a sign of mitochondrial damage; ATP production shows ATP produced by the mitochondria to meet the energetic need of the cell.
Critical Care Clinics, 1995
Critical illness is associated with major abnormalities in metabolism. The "metabolic response to stress" 104 is characterized by changes in metabolic rate, altered substrate (carbohydrate, fat, and protein) utilization, and catabolism. These alterations in the endogenous metabolic milieu provide a challenge when designing nutritional support regimens. This has increased interest in measuring metabolic rate and substrate utilization to provide a better understanding of how, when, and what to feed critically ill patients. Measuring metabolic rate in critically ill patients is performed using indirect calorimetry-calculating energy expenditure from measurements of oxygen consumption (Vo 2) and carbon dioxide production (Vco 2). This article reviews the techniques used in performing these measurements, data interpretation, and clinical applications. HISTORICAL OVERVIEW Since the discovery that gases support life, researchers have pursued ways to measure the energy output of living creatures. Lavoisier not only discovered "oxygene" but, in 1780, constructed a combustion calorimeter.53 In 1784, he was "the first to carry out respiration trials as we understand the term today, by measuring the amounts of 0 2 [oxygen] consumed and/or C0 2 [carbon dioxide] produced by an animal." 53 From 1778 to the present, there has been a continuous evolution of metabolic measurement instruments built by those driven by curiosity regarding
Critical Care, 2017
Introduction Imbalance in cellular energetics has been suggested to be an important mechanism for organ failure in sepsis and septic shock. We hypothesized that such energy imbalance would either be caused by metabolic changes leading to decreased energy production or by increased energy consumption. Thus, we set out to investigate if mitochondrial dysfunction or decreased energy consumption alters cellular metabolism in muscle tissue in experimental sepsis. Methods We submitted anesthetized piglets to sepsis (n = 12) or placebo (n = 4) and monitored them for 3 hours. Plasma lactate and markers of organ failure were measured hourly, as was muscle metabolism by microdialysis. Energy consumption was intervened locally by infusing ouabain through one microdialysis catheter to block major energy expenditure of the cells, by inhibiting the major energy consuming enzyme, N+/K + -ATPase. Similarly, energy production was blocked infusing sodium cyanide (NaCN), in a different region, to bloc...
British Journal of Anaesthesia, 1999
Abnormal oxygen use and organ failure in the critically ill may result from 'poisoning' of mitochondrial function. Measurement of arterial ketone body ratio (AKBR) has been proposed to reflect mitochondrial redox state and may provide a useful marker to monitor mitochondrial function in the critically ill. We measured AKBR (acetoacetate to β-hydroxybutyrate) and plasma lactate concentrations in 20 critically ill patients, on 3 consecutive days after admission to the intensive care unit. Nine (45%) patients died (five with sepsis) within the 30-day followup period. AKBR increased significantly over the 3 days of the study in patients who died (Pϭ 0.034) and decreased in those who survived (PϽ0.0001). In addition, there was a significant difference between survivors and non-survivors (Pϭ0.015). We conclude that serial AKBR measurement may be useful in the management of septic patients.
Minerva anestesiologica, 2006
Oxidation of substrates is the main biochemical process used by the human body to produce energy. Different substrates (carbohydrates, lipids, and proteins) have different effects on oxygen consumption and carbon dioxide production: during the critical phase of pathologies it could be relevant pay attention to the use of various nutrients, that have some altered effect respect to the normal subjects metabolism, and during the length of metabolic treatment, too. Generally, nutrition lead to replenish body stores, while endogenous substrates are used to be oxidized. Critically ill patients show a preference for prompt energy availability (i.e. glucose) to avoid endogenous protein catabolism; lipids are shown to have a more pronounced storage effect. Adequate amount of energy intake in carbohydrates determine an increase of RQ, that means a shift from a more lipid-based to a more glucose-based oxidation. Composition of dietary intake can be usefully different for each pathology, and al...
2014
† Energy requirements are difficult to measure precisely in critically ill intensive care unit patients and are not monitored routinely. † This small study compared two commercially available metabolic monitors (Medgraphics Ultima and Deltatrac II) with a Douglas bag technique. † There was poor agreement between readings from the three devices. † More accurate devices are needed to monitor gas exchange in mechanically ventilated patients. Background. The accuracy of oxygen consumption measurement by indirect calorimeters is poorly validated in mechanically ventilated intensive care patients where multiple confounders exist. This study sought to compare the Medgraphics Ultima (MGU) and Deltatrac II (DTII) devices, and the Douglas bag (DB) technique in mechanically ventilated patients at rest. Methods. Prospective comparison of oxygen consumption measurement using three indirect calorimetry techniques in stable, resting mechanically ventilated patients at rest. Oxygen consumption (VO 2), carbon dioxide production (VCO 2), resting energy expenditure (REE), and respiratory quotient (RQ) were recorded breath-by-breath by the MGU over a 30-75 min period. During this time, simultaneous measurements were taken using the DTII, the DB, or both. Results. While there was no systematic error (bias) between measurements made by the three techniques (VO 2 : MGU vs DTII 3.6%, MGU vs DB 3.3%), the limits of agreement were wide (VO 2 : MGU vs DTII 33%, MGU vs DB 54%). Conclusions. Resting oxygen consumption values in stable mechanically ventilated patients measured by the three techniques showed acceptable bias but poor precision. There is an important clinical and research need to develop new indirect calorimeters specifically tailored to measure oxygen consumption during mechanical ventilation.
CHEST Journal, 1984
Critical Care, 2014
Novel insights into the metabolic alterations of critical illness, including new findings on association between blood glucose at admission and poor outcome, were published in Critical Care in 2013. The role of diabetic status in the relation of the three domains of glycemic control (hyperglycemia, hypoglycemia, and glycemic variability) was clarified: the association between mean glucose, high glucose variability, and ICU mortality was stronger in the non-diabetic than in diabetic patients. Improvements in the understanding of pathophysiological mechanisms of stress hyperglycemia were presented. Novel developments for the management of glucose control included automated closed-loop algorithms based on subcutaneous glucose measurements and microdialysis techniques. In the field of obesity, some new hypotheses that could explain the 'obesity paradox' were released, and a role of adipose tissue in the response to stress was suggested by the time course of adipocyte fatty-acid binding protein concentrations. In the field of nutrition, beneficial immunological effects have been associated with early enteral nutrition. Early enteral nutrition was significantly associated with potential beneficial effects on the phenotype of lymphocytes. Uncertainties regarding the potential benefits of small intestine feeding compared with gastric feeding were further investigated. No significant differences were observed between the nasogastric and nasojejunal feeding groups in the incidence of mortality, tracheal aspiration, or exacerbation of pain. The major risk factors to develop diarrhea in the ICU were described. Finally, the understanding of disorders associated with trauma and potential benefits of blood acidification was improved by new experimental findings.
Acta medica Indonesiana, 2008
Critical ill patients experience acute physiological changes because the body cannot fulfill the oxygen demand to perform normal aerobic metabolism. Factors determining oxygen delivery include cardiac output, hemoglobin, and oxygen saturation. Incapability to fulfill adequate oxygen of the body to produce adenosine triphosphate (ATP) may occur due to decreased oxygen delivery and/or increased oxygen consumption. A condition in which oxygen consumption becomes very dependent on oxygen delivery is called critical oxygen delivery. Parameters to evaluate the adequate oxygen delivery to meet the oxygen consumption are central vein oxygen saturation (SvO2), serum lactate, oxygen extraction ratio (O2ER). A comprehension about oxygen delivery and consumption is very important to overcome tissue hypoxia and various factors in critical ill patients.
CHEST Journal, 1990
We performed a prospective study in 28 critically ill patients to document variations in oxygen consumption and oxygen transport that occur spontaneously, without any experimental interventions designed to change Do!. Each study consisted of from three to five sets of measurements, including thermal dilution cardiac output and blood gases. The interval between any two measurements ranged from 20 to 60 minutes. It was concluded that changes in V0 2 and Do! can occur spontaneously in patients with normal The survival of all mammalian cells depends on a continuous supply ofoxy~en. To supply the oxygen requirements, oxygen is transported from the environment to the cells of the body via a delivery systenl which is dependent on three organ systems: lungs, blood and circulatory system. 1. Z The classic view of the relationship bern'een oxygen consumption and oxygen transport (D()z = cardiac output X arterial O 2 content) is that, under norlnal conditions, Vo z is a reflection of metabolic demands, and over a wide range of 002, does not depend on D()2.: 1 When 00 2 decreases because of a decrease in either cardiac output, hemoglobin, or arterial oxygen saturation, V0 2 remains equal to oxygen demand and is independent of 00 2 until a Hcritical" 0()2. 4-7 Belo\\' this Hcritical" 002, any further decrease produces a fall in V0 2 .2 Since oxygen demand is no longer satisfied, a lactic acidosis develops reflecting the onset of anaerobic metabolism. Recent studies have challenged this classic view. Several reports 2-4.R have found that, in some groups of critically ill patients,9-13 V0 2 appeared to be limited by oxygen transport even at normally adequate levels of 002, some of whom were thought to have normal lactate levels.IO.13.14 Clinical interventions which increased 00 2 in these patients were accompanied by a
Intensive Care Medicine, 1996
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