Fluid distribution kinetics during cardiopulmonary bypass

OBJECTIVE: The purpose of this study was to examine the isovolumetric distribution kinetics of crystalloid fluid during cardiopulmonary bypass. METHODS: Ten patients undergoing coronary artery bypass grafting participated in this prospective observational study. The blood hemoglobin and the serum albumin and sodium concentrations were measured repeatedly during the distribution of priming solution (Ringer's acetate 1470 ml and mannitol 15% 200 ml) and initial cardioplegia. The rate of crystalloid fluid distribution was calculated based on 3-min Hb changes. The preoperative blood volume was extrapolated from the marked hemodilution occurring during the onset of cardiopulmonary bypass. Clinicaltrials.gov: NCT01115166. RESULTS: The distribution half-time of Ringer's acetate averaged 8 minutes, corresponding to a transcapillary escape rate of 0.38 ml/kg/min. The intravascular albumin mass increased by 5.4% according to mass balance calculations. The preoperative blood volume, as extrapolated from the drop in hemoglobin concentration by 32% (mean) at the beginning of cardiopulmonary bypass, was 0.6-1.2 L less than that estimated by anthropometric methods (p<0.02). The mass balance of sodium indicated a translocation from the intracellular to the extracellular fluid space in 8 of the 10 patients, with a median volume of 236 ml. CONCLUSIONS: The distribution half-time of Ringer's solution during isovolumetric cardiopulmonary bypass was 8 minutes, which is the same as for crystalloid fluid infusions in healthy subjects. The intravascular albumin mass increased. Most patients were hypovolemic prior to the start of anesthesia. Intracellular edema did not occur. .

Curso de Atualização em Emergências Médicas: aula 19: reposição volêmica / Course of Updating in Medical Emergencies: class 19: volemic replacement

Hipovolemia em pacientes agudamente enfermos é um evento relativamente comum, e com importância clínica para o paciente, sendo a rápida e vigorosa reposição volêmica capaz de diminuir o risco de morte inicialmente e de evolução para falência renal na sequência. Neste artigo revisaremos os diferentes tipos de expansores, suas propriedades, vantagens e desvantagens. Os cristaloides se mantêm como preferência pela segurança, eficácia e baixo custo, com a desvantagem da importante formação de edema. As soluções hipertônicas têm indicação no atendimento pré-hospitalar por ser eficaz, porém com estabilização hemodinâmica de caráter efêmero, e pela possibilidade de distúrbios eletrolíticos. Estudos clínicos randomizados não demonstraram superioridade da albumina aos cristalóides e assim como são de custo alto ficam como segunda alternativa ou casos selecionados.

Hypovolemia in critically ill patients is a common event in intensive care patients, and it is clinically relevant for the patient. The fluid replacement is used to try to reduce risk of death and evolution to renal failure. In this article we review different types of expansors, their properties, advantages and disadvantages. Crystalloids are indicated for the safety, efficacy and low cost, the only disadvantage is oedema formation. Hypertonic crystalloid are indicated only in prehospitalar fluid resuscitation, because of your efficacy, but for a short period of time, and the possibility of hydroeletrolitic derangements. There is no evidence that colloids are more effective than crystalloids in reducing mortality in people who are critically ill or injured, and the high cost, turn them the second choice.