Balanced or unbalanced?
One of the main areas for debate within this area of medicine has been whether to use saline, or saline-based products (unbalanced), versus a fluid which contains electrolytes at similar levels to those found in plasma (balanced). At the Great World Fluid Debate (GWFD) over recent years, evidence has been presented showing that the use of saline can have harmful effects on patients, and that patients benefit from the use of balanced fluids. The potential issue with using saline is the risk of creating acid–base disorders in already critically ill patients. The acidosis can be caused from having excess levels of chloride within the plasma expanders, which can lead to hyperchloraemic metabolic acidosis (HCMA).
Shaw et al: Major complications, mortality and resource utilization after open abdominal surgery .
Professor Andrew Shaw, of Duke University Medical Centre, recently published a large observational trial that compared saline with a balanced plasma substitute in over 30,000 surgical patients. The primary outcome was major morbidity, and secondary outcomes included minor complications and acidosis-related interventions. The results showed that the use of a balanced fluid was associated with significantly:
- Less electrolyte disturbance
- Fewer acidosis investigations
- Fewer blood transfusions
- Less renal failure requiring dialysis
- Fewer interventions
- Less postoperative infection
The authors concluded that there was an increased risk of major morbidity and resource utilisation in those patients receiving saline.
Yunos et al: Association between a chloride-liberal versus chloride-restrictive intravenous fluid administration strategy and kidney injury in critically ill adults .
Yunos et al conducted a prospective, open-label, sequential period study of 760 patients admitted to the intensive care unit during a 6-month control period, compared with 773 patients admitted during the intervention period. During the control period, the patients were given traditional chloride-liberal intravenous fluid therapy, while during the intervention period patients received a chloride-restrictive regime. The results showed that the implementation of a chloride-restrictive strategy was associated with:
Other studies have also shown that HCMA has associated risks and that the use of balanced solutions can help to avoid the development of HCMA.
- A significant decrease in the incidence of acute kidney injury and failure.
- A significant decrease in the use of renal replacement therapy.
Mythen et al 2001
“..in our opinion there is enough evidence rendering the use of fluids high in chloride unwise..”, “...there is now mounting evidence that the administration of unbalanced fluids in sufficient quantities may cause abdominal dysfunction, renal dysfunction and possibly, clotting abnormalities.” 
Wilkes et al 2001
“..the use of balanced IV infusions can avoid the development of HCMA...” 
Lobo et al 2010
“The use of newer preparations of colloids in balanced solutions results in less derangement in acid-base status and seems to be a promising strategy to overcome metabolic acidosis...” 
For more information about the composition of fluids follow the link to Summary of IV fluids composition.
References Shaw et al. Major complications, mortality and resource utilization after open abdominal surgery. Ann Surg 2012; 255: 821-9.
 Yunos et al:-Association between a chloride-liberal versus chloride-restrictive intravenous fluid administration strategy and kidney injury in critically ill adults. JAMA 2012; 308 (15): 1566-72.
 Mythen et al. Hyperchloremic metabolic acidosis: is it clinically relevant? Transfus Altern Transfus Med 2001; 3(4): 15-19.
 Wilkes N et al. The effects of balanced versus saline-based hetastarch and crystalloid solutions on acid-base and electrolyte status and gastric mucosal perfusion in elderly surgical patients. Anesth Analg 2001; 93: 811-816.
 Lobo DN et al. Effect of volume loading with 1 litre intravenous infusions of 0.9% saline, 4% succinylated gelatine (Gelofusine) and 6% hydroxyethyl starch (Voluven) on blood volume and endocrine responses: a randomized, three-way crossover study in healthy volunteers. Crit Care Med 2010; 38: 464-70.