Perioperative volumes of saline cause a mild acidosis compared with buffered fluids. On the other hand, saline administration maintains plasma osmolality and better repletes vascular volume which is an important goal of perioperative fluid administration. Currently, there is no convincing evidence that either saline or buffered solutions are preferable. Consequently, both types of fluid remain in common use at the Clinic and worldwide.

There has never been a large trial of perioperative saline and balanced salt solutions comparing the incidence of major complications including acute kidney injury. The investigators primary objective is thus to determine the relative safety of perioperative saline and lactated Ringer's solution. Specifically, the investigators propose to test the:

1. Primary hypothesis that a composite of major in-hospital postoperative complications is lower in patients given lactated Ringer's solution compared to normal saline.
2. Secondary hypothesis that acute kidney injury, measured by AKIN criteria, is lower in patients given lactated Ringer's solution compared to normal saline.

The acquisition cost of saline and lactated Ringer's solutions is similar in the United States. (Curiously, buffered solutions are far more expensive than saline in Great Britain.) But to the extent that one fluid or the other provokes more complications, cost of care may be increased with that fluid selection. Cost may also be increased by the need for additional electrolyte monitoring and electrolyte replacement.

The investigators will therefore secondarily conduct an economic evaluation to determine the relative incremental hospital cost of each fluid. To the extent that one fluid or the other reduces cost (assuming similar complication rates), the Clinic will be able to reduce cost by specifying the appropriate fluid without impairing quality.

Evidence that one fluid or the other causes few complications would be a strong quality indicator that the Clinic should standardize perioperative fluid selection.

Inclusion Criteria:

• Patients having colorectal or similar surgery
• Patients having orthopedic or similar surgery
• Patients 18 years and older

Exclusion Criteria:

• Patients under 18 years of age