Balanced versus unbalanced salt solutions: What difference does it make?

There are strong observational data that support the notion that avoiding an elevated Cl− concentration or using fluids that reduce the rise in Cl− reduces renal dysfunction, infections, and possibly even mortality. However, observational studies only can indicate an association and cannot indicate causality. Unfortunately, randomized trials to date are far too limited to address this crucial issue. What is clear is that appropriate randomized trials will require very large populations. It also is not known whether the important variable is the concentration of Cl−, the difference in concentrations of Na+ and Cl−, or the total body mass of Cl−.