Rapid 500 mL albumin bolus versus rapid 200 mL bolus followed by slower continuous infusion in post-cardiac surgery patients: a pilot before-and-after study

A low mean arterial pressure (MAP) or cardiac index (CI) is common after cardiac surgery 1,2 and typically triggers treatment with fluid bolus therapy (FBT).3,4 However, insufficient FBT may fail to correct such instability, while excessive FBT may contribute to pulmonary congestion.Therefore, defining the optimal approach to FBT after cardiac surgery is clinically relevant.5,6 During haemodynamic instability, FBT is often administered rapidly.However, it may be better to administer the same amount of fluid as a smaller very rapid (3-4 minutes) bolus followed by a continuous infusion of the remaining fluid.This is because rapid FBT increases plasma atrial natriuretic peptide levels, an effect associated with glycocalyx injury, greater fluid extravasation, and intestinal oedema.7 In contrast, a slow infusion leads to long-lasting plasma volume expanding effects.8,9 Slower 4% albumin infusion could achieve more sustained haemodynamic changes after cardiac surgery, but it may fail to correct hypotension or low cardiac output rapidly enough.Logically, a small but very rapid fluid bolus followed by continuous infusion may combine the advantage of a rapid response with those associated with a sustained effect.Despite these physiological considerations and the findings of an international survey that about 30% of intensive care unit (ICU) clinicians define FBT as fluid given in less than 10 minutes while 50% define it as given over 30 minutes, 10 no investigation has compared these two approaches to FBT in post-cardiac surgery patients.Accordingly, we conducted a prospective before-andafter study of the haemodynamic effect of a rapid complete bolus of 4% albumin compared with a rapid small bolus of 4% albumin followed by a slower continuous infusion over 30 minutes (combined FBT) in post-cardiac surgery patients.We hypothesised that the combined FBT approach would achieve greater MAP effects than rapid FBT during a 30-minute post-FBT observation period. MethodsWe prospectively obtained institutional ethics approval for this study (Reference No. LNR/16/Austin/358).Individual