Crystalloids Versus Colloids: Fluid Strategies for Better Recovery Outcomes in Cardiac Surgery

Abstract

Objectives

Perioperative fluid resuscitation in cardiac surgery is vital, yet the optimal strategy remains debated. This review evaluates the current evidence on colloid versus crystalloid fluid resuscitation and considers whether alternative outcome measures may help us better identify optimal methods of fluid resuscitation for patients.

Methods

A search of electronic databases PubMed, Medline and Google Scholar was performed from inception to June 2025 to synthesise findings on the perioperative fluid management of patients undergoing cardiac surgery.

Results

Thirteen studies, involving a total of 34,935 patients, were included in this narrative review. Evidence comparing colloids and crystalloids perioperatively in cardiac surgery is mixed. Colloids, particularly albumin, show advantages in fluid balance, reduce vasopressor use and shorten ICU stays, but carry a higher risk of acute kidney injury, especially with synthetic colloids like hydroxyethyl starch. Crystalloids are less associated with renal complications yet contribute to increased fluid retention and longer hospital stays. Few studies, however, report on fluid balance, renal function and preservation of microcirculation, limiting the understanding of fluid strategies on these relevant postoperative outcomes.

Conclusions

Mortality alone may be an insufficient measure for evaluating fluid resuscitation strategies in cardiac surgery. Expanding outcome measures to include fluid balance, preservation of microcirculation and a standardised assessment of renal function could yield more clinically relevant actionable insights and support safer, more individualised fluid management. Further research is warranted to assess these outcomes and establish more holistic, patient-centred standards in postoperative care.