Fluid bolus therapy (FBT) in Emergency medicine

- Darshana Kanan

Fluid bolus therapy (FBT) aims to increase the intravascular volume and the pressure gradient for venous return to increase stroke volume (SV) and cardiac output (CO) and meet the overarching goal of improving end-organ perfusion.

Aggressive fluid therapy for this purpose, a major component of early goal-directed therapy (EGDT) was described in the 2001 Rivers et al. sentinel paper. This trial compared standard care with EGDT on septic patients who presented to ED and were admitted to ICU. In addition to standardised goals, the EGDT group had an extra goal of reaching central venous O2 saturation (ScvO2) ≥ 70%. Monitoring this goal was expected to identify global tissue hypoxia despite normal vital signs that would otherwise be overlooked, enabling prompt patient management that would prevent sudden cardiovascular collapse and death. Notably, EGDT was strongly associated with significantly lower in-hospital mortality compared to the standard-care group (relative risk 0.58; p = 0.009).

However, the FEAST, ARISE, ProcESS and ProMISe multicentre trials claimed that EGDT provides no additional benefit in terms of mortality, hospital stay or the need for organ support compared to standard care. A systematic review of the trials investigating EGDT efficacy reinforced this and further associated EGDT with increased vasopressor use and ICU admissions.

Therefore, there is an association between aggressive FBT and fluid overload-mediated harms inflicted upon the patient. Therefore, while FBT is crucial in the management of haemodynamically unstable patients, patients cannot ubiquitously be prescribed fluid therapy. Rather, patients need to be assessed on a case-by-case basis of their fluid responsiveness to determine if and how much FBT would be beneficial to their treatment.

The dangers of fluid overload is associated with the development of acute pulmonary oedema which is the target of my research project. Overall, lung ultrasound (LUS) is a proven dynamic tool to determine pulmonary oedema in a variety of fluid overloaded states. Determining A- or B-line predominance in LUS scans is quick with the former indicating safe fluid resuscitation in terms of lung function while the latter is a pre-radiographic and preclinical sign consistent with pulmonary oedema and potential harms. Thus, in the context of FBT in ED, LUS may help safeguard patients against excessive fluid administration.