Perioperative buffered versus non‐buffered fluid administration for surgery in adults
Abstract
Background
Perioperative fluid therapy influences clinical outcomes following major surgery. Fluid preparations may be based on a simple non‐buffered salt solution, such as normal saline, or may be modified with bicarbonate or bicarbonate precursor buffers, such as maleate, gluconate, lactate or acetate, to better reflect the human physiological state. These latter fluids have theoretical advantages over normal saline in preventing hyperchloraemic acidosis. A number of clinical studies have now compared fluid preparations with and without a buffer to achieve a balanced electrolyte solution for perioperative fluid resuscitation.
Objectives
To review the safety and efficacy of perioperative administration of buffered versus non‐buffered fluids for plasma volume expansion or maintenance in adult patients undergoing surgery.
Search methods
We electronically searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2011, Issue 4), MEDLINE (1966 to May 2011), EMBASE (1980 to May 2011), and CINAHL (1982 to May 2011). We handsearched conference abstracts and where possible, contacted leaders in the field.
Selection criteria
We only included randomized trials of buffered versus non‐buffered intravenous fluids for perioperative fluid resuscitation. The trials with other forms of comparisons such as crystalloids versus colloids and colloids versus different colloids were excluded. We also excluded trials using hypertonic fluids and dextrose‐based fluids.
Data collection and analysis
Two authors independently extracted data and assessed the methodological quality of clinical trials. We resolved any disagreements by discussion. We contacted the trial authors to provide additional information where appropriate. We presented pooled estimates of the dichotomous outcomes as odds ratios (OR) and on continuous outcomes as mean differences, with 95% confidence intervals (CI). We analysed data on Review Manager 5.1 using fixed‐effect models, and when heterogeneity was high (I² > 40%) random‐effect models were used.
Main results
We identified 14 publications reporting 13 trials or comparisons with a total of 706 participants. For many of the outcomes reported, there was significant clinical and statistical heterogeneity. The primary outcome of mortality at any time was reported in only three studies with a total of 267 patients. The mortality rate was 2.9% for the buffered fluids group and 1.5% for the non‐buffered fluids group but this difference was not statistically significant. The Peto OR was 1.85 (95% CI 0.37 to 9.33, P = 0.45, I2= 0%). Organ dysfunction was only presented for renal impairment. There was no difference in renal insufficiency leading to renal replacement therapy between the buffered and non‐buffered groups (OR 0.61, 95% CI 0.23 to 1.63, P = 0.32, I2 = 0%). Markers of organ system failure as assessed by urine output, creatinine and its variables (for renal function), PaC02 (respiratory function) and postoperative nausea and vomiting (gastro‐intestinal function) showed a statistically significant difference only in PaC02 levels. The mean difference was 1.18 with lower PaC02 levels in the non‐buffered fluid group (95% CI 0.09 to 2.28, P = 0.03, I2 = 0%) compared to the buffered fluid group.
There was no difference in intraoperative blood loss nor the volumes of intraoperative red cell or fresh frozen plasma transfused between groups. There was an increase in platelet transfusion in the non‐buffered group which was statistically significant after analysing the transformed data (log transformation because the data were highly skewed).
A number of metabolic differences were noted. There was a difference in postoperative pH of 0.06 units, lower in the non‐buffered fluid group (95% CI 0.04 to 0.08, P < 0.00001, I2 = 74%). However, this difference was not maintained on postoperative day one. The non‐buffered fluid group also had significantly greater base deficit, serum sodium and chloride levels.
There was no difference demonstrated in length of hospital stay and no data were reported on cost or quality of life.
Authors' conclusions
The administration of buffered fluids to adult patients during surgery is equally safe and effective as the administration of non‐buffered saline‐based fluids. The use of buffered fluids is associated with less metabolic derangement, in particular hyperchloraemia and metabolic acidosis. Larger studies are needed to assess robust outcomes such as mortality.
PICOs
Plain language summary
Buffered versus non‐buffered fluids given to adults during surgery
During surgery, patients are given fluids into their veins to prevent and treat dehydration and loss of blood. Some fluids consist of a simple salt solution whilst others are matched more closely to the fluid in the blood. These latter fluids are called buffered fluids because they maintain the balance of the acids and bases in the body. We searched the available literature for prospective randomized studies which compared outcomes with the use of buffered fluids and the use of non‐buffered fluids when given to patients during surgery.
We included 14 publications in this Cochrane review, reporting data from 13 trials with a total of 706 participants of whom 368 received buffered fluids and 338 received non‐buffered fluids. The patients who received buffered fluids had an acid‐base balance that was more normal than for those who received non‐buffered fluids; and the need for the transfusion of some blood products was reduced. Overall, buffered fluids are a safe and effective alternative to non‐buffered fluids when given into the veins of patients undergoing surgery.
