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Abstract(s)
A administração de fluidos com o objectivo de aumentar o débito cardíaco é uma prática
comum e um recurso valioso na abordagem ao doente hemodinamicamente instável. Contudo,
recentemente, têm sido demonstrados diversos efeitos prognósticos adversos da utilização
excessiva de fluidos, e da sua aplicação em doentes incapazes de converter o aumento do
volume intravascular em aumento do débito cardíaco.
Classicamente, parâmetros estáticos, como a pressão venosa central e a pressão de oclusão
da artéria pulmonar, foram utilizados na avaliação do estado de volume intravascular.
Contudo, diversos estudos evidenciaram a alta ineficácia destes indicadores em predizer a
capacidade de resposta à administração de fluidos.
Consequentemente, nos últimos anos, têm sido propostos diversos parâmetros dinâmicos, que
apresentam maiores valores preditivos. Os métodos dinâmicos procuram identificar variações
do volume de ejecção, utilizando métodos invasivos e não invasivos, em resposta a mudanças
da pré-carga, como são as induzidas pela ventilação, pela elevação passiva dos membros
inferiores e pela administração de pequenos volumes de fluidos. Estes métodos são baseados
no conceito de capacidade de resposta à administração de fluidos que designa os indivíduos
cujo coração se encontra a operar na parte de maior declive da curva de Frank-Starling.
Cada um dos métodos recorre a um procedimento que induz a alteração da pré-carga e a um
processo de estudo que, directa ou indirectamente, avalia a variação do volume de ejecção
resultante. Assim, cada método apresenta vantagens e limitações próprias, as quais devem
ser reconhecidas pelo médico na sua aplicação clínica.
Fluid administration intended to raise cardiac debit is a common practice and a valuable resource in the approach of hemodynamically unstable patients. However, recently various adverse effects have been demonstrated, from both the use of excessive fluids and their use in patients unable to raise the cardiac debit after increasing intravascular volume. Classically, static parameters, such as the central venous pressure and the pulmonary artery occlusion pressure, were used for intravascular volume assessment, and thus, as indicators of need for fluid administration. However, several studies have demonstrated the high ineffectiveness of these indicators in predicting fluid responsiveness. Consequently, over the last years, various dynamic parameters with higher predictive values have been proposed. The dynamic methods seek to identify variations in stroke volume, using both invasive and noninvasive methods, in response to changes in preload, as are those caused either by ventilation, by passive leg raising or by intravenous infusion of small fluid volumes. These methods are based on the concept of fluid responsiveness, which designates individuals whose heart is operating at the higher slope of the Frank-Starling curve. Each method uses a procedure for inducing a change in preload and a manner of studying that directly or indirectly measures the change in stroke volume variation. Thus, each method has its own advantages and limitations, which shall be recognized by the physician upon their clinical application.
Fluid administration intended to raise cardiac debit is a common practice and a valuable resource in the approach of hemodynamically unstable patients. However, recently various adverse effects have been demonstrated, from both the use of excessive fluids and their use in patients unable to raise the cardiac debit after increasing intravascular volume. Classically, static parameters, such as the central venous pressure and the pulmonary artery occlusion pressure, were used for intravascular volume assessment, and thus, as indicators of need for fluid administration. However, several studies have demonstrated the high ineffectiveness of these indicators in predicting fluid responsiveness. Consequently, over the last years, various dynamic parameters with higher predictive values have been proposed. The dynamic methods seek to identify variations in stroke volume, using both invasive and noninvasive methods, in response to changes in preload, as are those caused either by ventilation, by passive leg raising or by intravenous infusion of small fluid volumes. These methods are based on the concept of fluid responsiveness, which designates individuals whose heart is operating at the higher slope of the Frank-Starling curve. Each method uses a procedure for inducing a change in preload and a manner of studying that directly or indirectly measures the change in stroke volume variation. Thus, each method has its own advantages and limitations, which shall be recognized by the physician upon their clinical application.
Description
Keywords
Monitorização Hemodinâmica Pré-Carga Resposta A Fluidos Volume de Ejecção Volume Intravascular