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RESUMO A proporção entre pressão venosa central menos arterial de dióxido de carbono e conteúdo de oxigênio arterial menos venoso central (Pcv-aCO2/Ca-cvO2) foi proposta como marcador substituto para quociente respiratório e indicador de oxigenação tissular. Alguns pequenos estudos observacionais identificaram que Pcv-aCO2/Ca-cvO2 acima de 1,4 se associa com hiperlactatemia, dependência de suprimento de oxigênio e maior mortalidade. Mais ainda, a Pcv-aCO2/Ca-cvO2 foi incorporada a algoritmos para avaliação da oxigenação tissular e ressuscitação. Contudo, a evidência para estas recomendações é bastante limitada e de baixa qualidade. O objetivo desta revisão narrativa foi analisar as bases metodológicas, os fundamentos fisiopatológicos e a evidência experimental e clínica para dar suporte à utilização da Pcv-aCO2/Ca-cvO2 como marcador substituto para quociente respiratório. De um ponto de vista fisiopatológico, o aumento do quociente respiratório secundariamente a reduções críticas no transporte de oxigênio é um evento dramático e com risco à vida. Entretanto, este evento é facilmente observável e provavelmente não demandaria maiores monitoramentos. Visto que o início do metabolismo anaeróbico é indicado pelo aumento súbito do quociente respiratório e que a faixa normal do quociente respiratório é ampla, o uso do ponto de corte definido como 1,4 para Pcv-aCO2/Ca-cvO2 não faz sentido. Estudos experimentais demonstraram que a Pcv-aCO2/Ca-cvO2 é mais dependente de fatores que modificam a dissociação do dióxido de carbono da hemoglobina do que do quociente respiratório, e o quociente respiratório e Pcv-aCO2/Ca-cvO2 podem ter comportamentos distintos. Estudos conduzidos em pacientes críticos demonstraram resultados controvertidos com relação à capacidade da Pcv-aCO2/Ca-cvO2 para predizer o desfecho, hiperlactatemia, anomalias microvasculares e dependência de suprimento de oxigênio. Um estudo randomizado controlado também demonstrou que a Pcv-aCO2/Ca-cvO2 é inútil como alvo para ressuscitação. A Pcv-aCO2/Ca-cvO2 deve ser interpretada com cautela em pacientes críticos.
ABSTRACT The central venous minus arterial carbon dioxide pressure to arterial minus central venous oxygen content ratio (Pcv-aCO2/Ca-cvO2) has been proposed as a surrogate for respiratory quotient and an indicator of tissue oxygenation. Some small observational studies have found that a Pcv-aCO2/Ca-cvO2 > 1.4 was associated with hyperlactatemia, oxygen supply dependency, and increased mortality. Moreover, Pcv-aCO2/Ca-cvO2 has been incorporated into algorithms for tissue oxygenation evaluation and resuscitation. However, the evidence for these recommendations is quite limited and of low quality. The goal of this narrative review was to analyze the methodological bases, the pathophysiologic foundations, and the experimental and clinical evidence supporting the use of Pcv-aCO2/Ca-cvO2 as a surrogate for respiratory quotient. Physiologically, the increase in respiratory quotient secondary to critical reductions in oxygen transport is a life-threatening and dramatic event. Nevertheless, this event is easily noticeable and probably does not require further monitoring. Since the beginning of anaerobic metabolism is indicated by the sudden increase in respiratory quotient and the normal range of respiratory quotient is wide, the use of a defined cutoff of 1.4 for Pcv-aCO2/Ca-cvO2 is meaningless. Experimental studies have shown that Pcv-aCO2/Ca-cvO2 is more dependent on factors that modify the dissociation of carbon dioxide from hemoglobin than on respiratory quotient and that respiratory quotient and Pcv-aCO2/Ca-cvO2 may have distinct behaviors. Studies performed in critically ill patients have shown controversial results regarding the ability of Pcv-aCO2/Ca-cvO2 to predict outcome, hyperlactatemia, microvascular abnormalities, and oxygen supply dependency. A randomized controlled trial also showed that Pcv-aCO2/Ca-cvO2 is useless as a goal of resuscitation. Pcv-aCO2/Ca-cvO2 should be carefully interpreted in critically ill patients.
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Humanos , Oxigênio/metabolismo , Artérias , Veias , Dióxido de Carbono/sangue , Pressão , GasometriaRESUMO
Objective@#To study the nutritional status and energy metabolic characteristics of patients with nonalcoholic fatty liver disease (NAFLD), and to provide evidence for clinical evaluation and intervention.@*Methods@#A total of 359 NAFLD patients diagnosed on ultrasound from June 2015 to March 2017 were selected as study subjects and divided into mild, moderate to severe fatty liver disease group and 50 healthy subjects as control group. The changes of ICW, ECW, body fat, skeletal muscle, protein and visceral fat area (VFA) of patients and controls were analyzed by using body composition analyzer. The energy metabolism index was measured by the oxidation rate of resting energy expenditure(REE), respiratory quotient (RQ), and the oxidation rates of the three nutrients (CHO %, FAT %, and PRO %). According to different types of data, non-parametric tests like Kruskal-Wallis or χ2 were used for this analysis.@*Results@#Compared with the mild fatty liver group and the control group, the moderate and severe fatty liver group the BMI, waist circumference, waist-hip ratio were significantly elevated (P-value < 0.001), and their serum alanine aminotransferase, triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein, FBS levels were significantly increased (P value < 0.05). The Body composition analysis showed that there was no significant difference in skeletal muscle content between the three groups (P = 0.067). The ICW, ECW, protein, body fat content of moderate and severe fatty liver group were significantly higher than those of mild fatty liver group and control group (P < 0.01), but there was no significant difference between the mild fatty liver group and the control group. There was significant difference in the VFA between the three groups, while VFA in the moderate and severe fatty liver group was significantly increased. Metabolic results showed that the RQ of patients with moderate-severe fatty liver and mild fatty liver were 0.72 ± 0.08 and 0.78 ± 0.06, respectively, which were lower than those of the control group (0.80 ± 0.02), P = 0.004. Resting energy expenditure (REE) was not significantly different between moderate and severe fatty liver group and mild fatty liver group (P = 0.207), but both were significantly higher than those of the control group (P < 0.001). The percentages of CHO, FAT and PRO in moderate and severe fatty liver group were 19.49% ± 9.71%, 66.23% ± 12.54% and 14.22% ± 6.11% respectively. Compared with the control group, CHO % decreased, and FAT % increased.@*Conclusion@#NAFLD patients have different extent of nutritional imbalance and energy metabolism disorders, the use of Body Composition analyzer and metabolic cart can comprehensively assess and monitor NAFLD patient’s nutrition and energy metabolism status, to provide a basis for clinical intervention.
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PURPOSE: Recently, there has been a marked increase in childhood obesity, and that has aroused social concern. Obesity increases several metabolic disease such as hypertension, diabetes, fatty liver, heart disease and the mortality rate. Complications of obesity are more closely related with the accumulation of visceral fat. Therefore, fundamental treatment of obesity Should be the reduction of body fat. Exercise is the best way to reduce body fat, especially to consume the free fatty acid released from adipocytes. However, it is anticipated that children's response to exercise could differ from adult's. This research was done to find the difference adaptations of energy metabolisms in exercises between children and adults. METHODS: Sprague-Dawley male rats were divided into a young group(two-three months old), adult group(six months old) and an old group(fifteen months old). At fed ad libitum, O2 consumption and CO2 production were measured before and after the exercise. Before and after fasting for 24 hours, O2 consumption and CO2 production were measured. After fasting for 24 hours, the blood was taken to analyse the plasma glucose and free fatty acid. RESULTS: The fasting oxygen consumption decreased only in young rats compared with that of the fed state. The fasting respiratory quotient was decreased in the young and adult rats compared with those of the fed state. The post exercise oxygen consumption was increased in the young and adult rats but not in the old rats. The post-exercise respiratory quotient was decreased only in the young rats. There was no significant change of plasma glucose and free fatty acid between fed and fasting state in the young rats, while the fasting glucose levels were increased in the adult and old rats. CONCLUSION: These results mean that the responses to fasting and exercise differ among rats of different age groups and young rats can burn fat more easily during exercise and fasting than those of the adult and old rats because of the better metabolic flexibility of young rats.