In the setting of a normal ejection fraction, fluid is only administered when the expectation is that cardiac output will increase, and vasopressors are utilized if the aforementioned devices show fluid will not increase cardiac output. Excess fluid in certain general surgical cases can cause ileus and bowel edema, and in cardiac cases, it can cause hemodilution. Patients randomized to restricted and liberal fluid resuscitation strategies found a clear linear relationship between total fluids administered (and weight gain) and complications following colorectal surgery including pulmonary edema and tissue-healing complications. Further multiple studies exist demonstrating fewer complications with normovolemia than with liberal strategies of fluid resuscitation.
It must be understood that goal-directed therapy does, in no way, mean reduction in fluid administration. For some procedures, it may be necessary to administer more than anticipated fluid volumes (orthopedics), while for others, the opposite may be true (abdominal). Normovolemia is important to maintain perfusion without volume overload. Thus, the idea behind goaldirected therapy is to maintain zero fluid balance coupled with minimal weight gain or loss. Hypovolemia is associated with reduced circulating blood volume, decreased renal perfusion, altered coagulation, microcirculation compromise, and endothelial dysfunction, among other processes. Hypervolemia is associated with splanchnic edema, decreased pulmonary gas exchange secondary to pulmonary edema, impaired wound healing, anastomotic dehiscence, decreased mobility, altered coagulation, and endothelial dysfunction, amidst others processes.
From a recent Cochrane review, there is no evidence that colloids are superior to crystalloid for resuscitation in patients. Therefore, crystalloid fluids should generally be the primary intravenous fluid during the perioperative course. In cardiac surgery, the utilization of 0.9% normal saline solution was associated with hyperchloremia and poor postoperative outcomes, including higher length of stay and increased mortality.118 Further, a more balanced crystalloid, such as Plasma-Lyte, was associated with improved outcomes in 22,851 surgical patients. In this study, there was a 2.05 odds ratio predictor of mortality with normal saline. Other complications such as acute kidney injury, gastrointestinal complications, major hemorrhage, and major infection were also increased in the group of
patients that were hyperchloremic after normal saline administration. Based on such evidence, it would seem prudent to proceed with a more balanced solution, such as PlasmaLyte, to reduce complications.
Surgery and anesthesia profoundly alter the normal physiologic and metabolic states. Estimating the patient’s ability to respond to these stresses in the postoperative period is the task of the preoperative evaluation. Perioperative complications are often the result of failure, in the preoperative period, to identify underlying medical conditions, maximize the patient’s preoperative health, or accurately assess perioperative risk. Sophisticated laboratory studies and specialized testing are no substitute for a thoughtful and careful history and physical examination. Sophisticated technology has merit primarily in confirming clinical suspicion.