RESUMO
OBJETIVO: As unidades de terapia intensiva recorrem às equações preditivas, para determinar o gasto energético, ou às recomendações estabelecidas por sociedades internacionais, devido à inacessibilidade da calorimetria indireta. O objetivo deste trabalho foi comparar o gasto energético de pacientes críticos, por calorimetria indireta, aos calculados por meio da equação de Harris-Benedict. MÉTODOS: Estudo retrospectivo observacional realizado no Serviço de Cuidados Intensivos 1 do Centro Hospitalar do Porto. Foram avaliadas as necessidades energéticas, desde janeiro de 2003 até abril de 2012, dos pacientes críticos internados em que foi realizada calorimetria indireta. Procedeu-se ao cálculo da precisão (intervalo de ±10% entre os valores medidos e estimados), da diferença média e dos limites de concordância da equação estudada. RESULTADOS: Foram avaliados 85 pacientes, em que se efetuaram 288 medições por calorimetria indireta. Valores obtidos para necessidades energéticas em diferentes métodos: calorimetria indireta 1.753,98±391,13 kcal ao dia (24,48±5,95 kcal/kg ao dia), equação de Harris-Benedict 1.504,11±266,99 kcal ao dia (20,72±2,43 kcal/kg ao dia). A precisão da equação foi de 31,76%, a diferença média de -259,86 kcal ao dia, com limites de concordância entre -858,84 a 339,12 kcal ao dia. O gênero (p=0,023), a temperatura (p=0,009) e o índice de massa corporal (p<0,001) revelaram-se fatores com impacto significativo no gasto energético. CONCLUSÃO: A equação de Harris-Benedict não é precisa na determinação do gasto energético, subestimando-o e apresentando diferenças significativas para predizer, a nível individual, o gasto energético real.
OBJECTIVE: Given the inaccessibility of indirect calorimetry, intensive care units generally use predictive equations or recommendations that are established by international societies to determine energy expenditure. The aim of the present study was to compare the energy expenditure of critically ill patients, as determined using indirect calorimetry, to the values obtained using the Harris-Benedict equation. METHODS: A retrospective observational study was conducted at the Intensive Care Unit 1 of the Centro Hospitalar do Porto. The energy requirements of hospitalized critically ill patients as determined using indirect calorimetry were assessed between January 2003 and April 2012. The accuracy (± 10% difference between the measured and estimated values), the mean differences and the limits of agreement were determined for the studied equations. RESULTS: Eighty-five patients were assessed using 288 indirect calorimetry measurements. The following energy requirement values were obtained for the different methods: 1,753.98±391.13 kcal/day (24.48 ± 5.95 kcal/kg/day) for indirect calorimetry and 1,504.11 ± 266.99 kcal/day (20.72±2.43 kcal/kg/day) for the Harris-Benedict equation. The equation had a precision of 31.76% with a mean difference of -259.86 kcal/day and limits of agreement between -858.84 and 339.12 kcal/day. Sex (p=0.023), temperature (p=0.009) and body mass index (p<0.001) were found to significantly affect energy expenditure. CONCLUSION: The Harris-Benedict equation is inaccurate and tends to underestimate energy expenditure. In addition, the Harris-Benedict equation is associated with significant differences between the predicted and true energy expenditure at an individual level.
RESUMO
OBJECTIVE: Given the inaccessibility of indirect calorimetry, intensive care units generally use predictive equations or recommendations that are established by international societies to determine energy expenditure. The aim of the present study was to compare the energy expenditure of critically ill patients, as determined using indirect calorimetry, to the values obtained using the Harris-Benedict equation. METHODS: A retrospective observational study was conducted at the Intensive Care Unit 1 of the Centro Hospitalar do Porto. The energy requirements of hospitalized critically ill patients as determined using indirect calorimetry were assessed between January 2003 and April 2012. The accuracy (± 10% difference between the measured and estimated values), the mean differences and the limits of agreement were determined for the studied equations. RESULTS: Eighty-five patients were assessed using 288 indirect calorimetry measurements. The following energy requirement values were obtained for the different methods: 1,753.98±391.13 kcal/day (24.48 ± 5.95 kcal/kg/day) for indirect calorimetry and 1,504.11 ± 266.99 kcal/day (20.72±2.43 kcal/kg/day) for the Harris-Benedict equation. The equation had a precision of 31.76% with a mean difference of -259.86 kcal/day and limits of agreement between -858.84 and 339.12 kcal/day. Sex (p=0.023), temperature (p=0.009) and body mass index (p<0.001) were found to significantly affect energy expenditure. CONCLUSION: The Harris-Benedict equation is inaccurate and tends to underestimate energy expenditure. In addition, the Harris-Benedict equation is associated with significant differences between the predicted and true energy expenditure at an individual level.
