Hypotension after cardiac surgery within the intensive care unit (ICU) is common and is a frequent trigger for the administration of a fluid bolus.
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Such fluid bolus therapy contributes to about 50% of the total fluid volume patients receive in the first 24 hours after surgery.
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Cengic S, Zuberi M, Bansal V, et al. Hypotension after intensive care unit drop-off in adult cardiac surgery patients. World J Crit Care Med 2020; 9: 20-30
Parke RL, McGuinness SP, Gilder E, et al. Intravenous fluid use after cardiac surgery: a multicentre, prospective, observational study. Crit Care Resusc 2014; 16: 164
Colloid solutions have been widely used for fluid bolus therapy in cardiac surgery.
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This is due to the belief that their increased oncotic pressure leads to less total volume being administered to achieve equivalent haemodynamic effects than crystalloid therapy.
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Such a reduction in volume may be beneficial.
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Sedrakyan A, Gondek K, Paltiel D, et al. Volume expansion with albumin decreases mortality after coronary artery bypass graft surgery. Chest 2003; 123: 1853-7
Yanase F, Cutuli SL, Naorungroj T, et al. A comparison of the hemodynamic effects of fluid bolus therapy with crystalloids vs. 4% albumin and vs. 20% albumin in patients after cardiac surgery. Heart Lung 2021; 50: 870-6
Prowle JR, Kirwan CJ, Bellomo R. Fluid management for the prevention and attenuation of acute kidney injury. Nat Rev Nephrol 2014; 10: 37-47
Wiedemann HP, Wheeler AP, Bernard GR, et al. Comparison of two fluid-management strategies in acute lung injury. N Engl J Med 2006; 354: 2564-75
Tigabu BM, Davari M, Kebriaeezadeh A, et al. Fluid volume, fluid balance and patient outcome in severe sepsis and septic shock: a systematic review. J Crit Care 2018; 48: 153-9
Synthetic colloids cause worse outcomes than crystalloid fluids.
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However, a natural colloid, albumin solution, is safe for most patients, with possible benefits in certain subgroups.
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In Australia and New Zealand, albumin solution is available in two formulations: albumin 4% and albumin 20%. Of these, 4 % albumin is the most frequently used colloid, but the proportion of albumin in the fluid may affect patient outcomes.
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It is plausible that 20% albumin may be better than 4% albumin for fluid resuscitation because the same haemodynamic targets are achieved with much lesser volumes of fluid.
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Bayer O, Reinhart K, Kohl M, et al. Effects of fluid resuscitation with synthetic colloids or crystalloids alone on shock reversal, fluid balance, and patient outcomes in patients with severe sepsis: a prospective sequential analysis. Crit Care Med 2012; 40: 2543-51
Bayer O, Reinhart K, Sakr Y, et al. Renal effects of synthetic colloids and crystalloids in patients with severe sepsis: A prospective sequential comparison. Crit Care Med 2011; 39: 1335-42
Myburgh JA, Finfer S, Bellomo R, et al. Hydroxyethyl starch or saline for fluid resuscitation in intensive care. N Engl J Med 2012; 367: 1901-11
Perner A, Haase N, Guttormsen AB, et al. Hydroxyethyl starch 130/0.42 versus Ringer’s acetate in severe sepsis. N Engl J Med 2012; 367: 124-34
The SSI, Finfer S, McEvoy S, et al. Impact of albumin compared to saline on organ function and mortality of patients with severe sepsis. Intensive Care Med 2011; 37: 86-96
Finfer S, Bellomo R, Boyce N, et al. A comparison of albumin and saline for fluid resuscitation in the intensive care unit. N Engl J Med 2004; 350: 2247-56
Vincent JL, Wilkes MM, Navickis RJ. Safety of human albumin — serious adverse events reported worldwide in 1998–2000. Br J Anaesth 2003; 91: 625-30
Wiedermann CJ, Joannidis M. Albumin replacement in severe sepsis or septic shock. N Engl J Med 2014; 371: 83
Caironi P, Tognoni G, Masson S, et al. Albumin replacement in patients with severe sepsis or septic shock. N Engl J Med 2014; 370: 1412-21
Charpentier J, Mira JP. Efficacy and tolerance of hyperoncotic albumin administration in septic shock patients: the EARSS study. Intensive Care Med 2011; 37 (Suppl): S115
Parke RL, McGuinness SP, Gilder E, et al. Intravenous fluid use after cardiac surgery: a multicentre, prospective, observational study. Crit Care Resusc 2014; 16: 164
Iguchi N, Kosaka J, Bertolini J, et al. Differential effects of isotonic and hypotonic 4% albumin solution on intracranial pressure and renal perfusion and function. Crit Care Resusc 2018; 20: 48-53
Yanase F, Cutuli SL, Naorungroj T, et al. A comparison of the hemodynamic effects of fluid bolus therapy with crystalloids vs. 4% albumin and vs. 20% albumin in patients after cardiac surgery. Heart Lung 2021; 50: 870-6
Mårtensson J, Bihari S, Bannard-Smith J, et al. Small volume resuscitation with 20% albumin in intensive care: physiological effects: the SWIPE randomised clinical trial. Intensive Care Med 2018; 44: 1797-806
We previously conducted a single centre, sequential period trial of 20% albumin compared with a predominantly crystalloid-based fluid bolus therapy strategy after cardiac surgery (HAS FLAIR-I).
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We reported a reduction in fluid balance along with a reduction in the duration and total dose of noradrenaline administered.
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However, our previous trial had substantial methodological limitations. Accordingly, there is uncertainty about the choice of optimal fluid bolus solution for patients in the ICU after cardiac surgery.
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Wigmore GJ, Anstey JR, St. John A, et al. 20% Human Albumin Solution Fluid Bolus Administration Therapy in Patients After Cardiac Surgery (the HAS FLAIR Study). J Cardiothorac Vasc Anesth 2019; 33: 2920-7
Wigmore GJ, Anstey JR, St. John A, et al. 20% Human Albumin Solution Fluid Bolus Administration Therapy in Patients After Cardiac Surgery (the HAS FLAIR Study). J Cardiothorac Vasc Anesth 2019; 33: 2920-7
Lewis SR, Pritchard MW, Evans DJW, et al. Colloids versus crystalloids for fluid resuscitation in critically ill people. Cochrane Database Syst Rev 2018; (8): CD000567
Hanley C, Callum J, Karkouti K, et al. Albumin in adult cardiac surgery: a narrative review. Can J Anaesth 2021; 68: 1197-213
For these reasons, we designed the 20% Human Albumin Solution Fluid Bolus Administration Therapy in Patients after Cardiac Surgery-II (HAS FLAIR-II) trial. Our objective is to determine whether fluid bolus therapy after cardiac surgery with 20% albumin reduces the duration of vasopressor therapy compared with crystalloid therapy. In this article, we describe the protocol and statistical plan for the HAS FLAIR-II trial in order to reduce the risk of analysis bias arising from knowledge of the study findings as they emerge during the analysis of the study data.
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Chan A-W, Tetzlaff JM, Altman DG, et al. SPIRIT 2013 statement: defining standard protocol items for clinical trials. Ann Intern Med 2013; 158: 200-7
Schulz KF, Altman DG, Moher D. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ 2010; 340: c332
ICH Harmonised Tripartite Guideline. Statistical principles for clinical trials. International Conference on Harmonisation E9 Expert Working Group. Stat Med 1999; 18: 1905-42
Methods
Design
This is a phase 2b, multicentre, parallel group, open-label randomised controlled trial conducted at six metropolitan ICUs in Australia. HAS FLAIR-II has been designed with reference to the Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT)
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checklist and the Consolidated Standards of Reporting of Trials (CONSORT) guidelines.
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Chan A-W, Tetzlaff JM, Altman DG, et al. SPIRIT 2013 statement: defining standard protocol items for clinical trials. Ann Intern Med 2013; 158: 200-7
Schulz KF, Altman DG, Moher D. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ 2010; 340: c332
Study population
The study population of interest is patients admitted to the ICU after cardiac surgery who require a fluid bolus. The need for a fluid bolus will be determined by the patients’ treating doctor. Patients will be eligible to be enrolled if they fulfil all the inclusion criteria and none of the exclusion criteria (Table 1).
Intervention
The intervention is human albumin solution administered as 100 mL of 20% weight by volume of human albumin solution (CSL Behring, Melbourne, VIC, Australia). It is presented as a slightly viscous, almost colourless, liquid in a 100 mL clear glass bottle.
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The intervention will be administered as a bolus (defined in the Online Appendix). Patients assigned to the intervention who are assessed by the treating doctor as requiring further fluid bolus therapy will receive this as 20% albumin up to a maximum of 400 mL (80 g albumin) per calendar day. If the daily maximum is reached, additional fluid bolus therapy on that calendar day will be administered as 4% albumin — presented as 4% weight by volume of human albumin solution (CSL Behring) as a slightly viscous almost colourless liquid in a 500 mL clear glass bottle.
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Behring C. Australian product information: Albumex 20 (human albumin) — solution for intravenous infusion. CSL Behring, 2020. https://www.cslbehring.com.au/-/media/cslb-australia/documents/aus-pis-and-cmis/albumex-20-au-pi-1300.pdf? (viewed Oct 2)
Behring C. Australian product information: Albumex 4 (human albumin) — solution for intravenous infusion. CSL Behring, 2020. https://labeling.cslbehring.com/PI/AU/Albumex/EN/Albumex-4-Product-Information.pdf? (viewed Oct 2022)
Comparator
Participants assigned to the comparator will receive a crystalloid solution for at least the first 1000 mL of fluid bolus therapy, after which the treating clinician is permitted to use 4% albumin. The comparator group was chosen based on observational data.
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Suitable crystalloid solutions include, but are not limited to, 0.9% sodium chloride solution, compound sodium lactate or Plasma-Lyte148 (Baxter Healthcare). Administration of any albumin will be recorded and reported, with concentrations other than 4% being a protocol deviation.
Parke RL, McGuinness SP, Gilder E, et al. Intravenous fluid use after cardiac surgery: a multicentre, prospective, observational study. Crit Care Resusc 2014; 16: 164
Hammond NE, Taylor C, Saxena M, et al. Resuscitation fluid use in Australian and New Zealand Intensive Care Units between 2007 and 2013. Intensive Care Med 2015; 41: 1611-9
Duration of the study treatment
The duration of study treatment is for a maximum of 7 days after randomisation, with study treatment and observations censored at ICU discharge. The intervention or comparator will continue for all fluid bolus therapy administered in the index ICU admission until vasopressors are discontinued for 4 consecutive hours in the presence of a mean arterial pressure (MAP) ≥ 65 mmHg, or an alternative target MAP set by the treating clinician. For patients not receiving vasopressor therapy, the intervention or comparator will continue for all fluid boluses until midnight on day 7.
Screening
All patients admitted to a participating ICU following cardiac surgery will be considered for enrolment. Screening will be conducted by a site investigator or a member of the research department. Screening commenced on 31 August 2020. Inclusion and exclusion of patients (including reasons for exclusion) will be reported according to the CONSORT guidelines (Figure 1).
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Schulz KF, Altman DG, Moher D. CONSORT 2010 statement: updated guidelines for reporting parallel group randomised trials. BMJ 2010; 340: c332
Assignment of study treatment
Randomisation is performed using the randomisation module in REDCap (Research Electronic Data Capture) — a secure, web-based interface.
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Allocation concealment before randomisation is maintained using a permuted, variable size block schedule, stratified by site and the presence of a vasopressor at the time of randomisation. Randomisation is not performed until a participant fulfils all eligibility criteria and can be assigned to a study treatment.
Harris PA, Taylor R, Minor BL, et al. The REDCap consortium: building an international community of software platform partners. J Biomed Inform 2019; 95: 103208
Harris PA, Taylor R, Thielke R, et al. Research electronic data capture (REDCap) — a metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform 2009; 42: 377-81
Blinding of study treatment
It is not feasible to blind the study treatment and group assignment during trial conduct. However, during the analysis and drafting of the manuscript, the investigators, statisticians, and writing committee members will work with binary coded (A, B) data rather than the actual trial-group assignments. Further, the manuscript writing will be performed in duplicate, with the groups (A, B) interchanged. Importantly, group analyses of variables that may unblind the group allocation codes (eg, serum albumin, all fluid therapy volume and type) will be deferred until the two draft manuscripts have been completed.
Additional non-study treatment
All non-study treatments are left to the discretion of the treating clinicians. The use of maintenance fluids contributes to the daily fluid administration, the type and amount of maintenance fluid will be left to the discretion of the treating clinician.
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The use of 4% albumin for fluid bolus therapy in the comparator arm after 1000 mL of crystalloid fluid bolus therapy is at the discretion of the treating clinician. This crossover intervention will be specifically quantified and reported.
Bihari S, Prakash S, Potts S, et al. Addressing the inadvertent sodium and chloride burden in critically ill patients: a prospective before-and-after study in a tertiary mixed intensive care unit population. Crit Care Resusc 2018; 20: 285-93
Delaney A, Angus DC, Bellomo R, et al. Bench-to-bedside review: the evaluation of complex interventions in critical care. Crit Care 2008; 12: 210
Strategies to improve adherence to interventions
The study protocol for HAS FLAIR-II was presented at each of the participating sites and has included discussions with both the intensive care physicians and cardiac surgeons. Should the scenario arise where there is not clinical equipoise regarding the study treatment for a patient, they will be excluded. Such consultations combined with visual aids of the protocol targeted at the clinical staff have been employed to improve consistency in protocol implementation.
Baseline and operative characteristics
Baseline data and operative characteristics will be recorded and presented (Online Appendix).