To the Editor
We whole heartedly agree with Bailey et al.1 and Moritz and Ayus,2 who support the practice of perioperative isotonic fluid administration in the postoperative surgical patient. The 3 most recent studies referenced in the editorial3–5 add further support in favor of isotonic fluids preventing or minimizing hyponatremia while not exposing patients to the potential risks of hypernatremia.
In recommending 0.9% saline as the isotonic fluid of choice, the authors have based their selection on comparison with lactated Ringer's solution, a “balanced salt” solution. Although considered isotonic with plasma, concerns are raised regarding the relative hypotonic nature of the fluid with a sodium concentration of 130 mEq/L. The concern we have with the use of normal saline as a perioperative fluid is the associated hyperchloremic metabolic acidosis, which is a regular feature if large volumes of normal saline are infused intraoperatively.6,7 It is our understanding that the acidosis is due to associated increase in chloride ion concentration and alteration in the strong ion difference. Although outcome studies are lacking, we have concerns that the large chloride load and associated acidosis may be deleterious for both cardiac and renal function in the perioperative phase, especially in children undergoing cardiac surgery or in those with renal disease. It can also make differentiating the cause of an increasing base deficit difficult in procedures associated with significant blood loss and fluid replacement when periods of hypotension and/or hypoperfusion may occur.
An alternative isotonic, isosmotic “balanced salt ”solution is commercially available and has been widely used as our intraoperative replacement fluid of choice for more than 15 years. This fluid is Plasma-Lyte 148 (Baxter, Deerfield, IL). The osmolality of the solution is 294 mOsm and therefore more closely approximates plasma osmolality than lactated Ringer's solution. It has a slightly reduced sodium concentration compared with normal saline with a sodium ion concentration of 140 mmol/L (but significantly higher than lactated Ringer's solution) and a significantly lower chloride concentration of 98 mmol/L (Table 1). It also has potassium, magnesium, and gluconate/acetate as a bicarbonate ion producing buffer. It does not contain calcium and thus there is no concern with its interface with blood and blood products. Comparison with 0.9% saline as an intraoperative fluid in adults many years ago demonstrated a similar benefit to that shown by lactated Ringer's solution in producing less hyperchloremic acidosis.8
We therefore suggest the use of Plasma-Lyte 148 solution as an alternative to normal saline as a perioperative isotonic solution in children. However, we accept that the clinical comparison with normal saline has not been undertaken in children and that this would be useful in elucidating which isotonic fluid is best in the perioperative period.
James Houghton, FANZCA
Niall Wilton, MRCP, FRCA
Starship Children's Hospital
Auckland, New Zealand
Dr. Bailey did not wish to respond.
1. Bailey A, McNaull P, Jooste E, Tuchman J. Perioperative crystalloid and colloid fluid management in children: where are we and how did we get here? Anesth Analg 2010;110:375–90
2. Moritz M, Ayus JC. Water water everywhere: standardizing postoperative fluid therapy with 0.9% normal saline. Anesth Analg 2010;110:293–5
3. Montañana PA, Modesto i Alapont V, Ocón AP, López PO, López Prats JL, Toledo Parreño JD. The use of isotonic fluid as maintenance therapy prevents iatrogenic hyponatremia in pediatrics: a randomized, controlled open study. Pediatr Crit Care Med 2008;9:589–97
4. Neville KA, Sandeman DJ, Rubinstein A, Henry GM, McGlynn M, Walker JL. Prevention of hyponatremia during maintenance intravenous fluid administration: a prospective randomized study of fluid type versus fluid rate. J Pediatr 2010;156:313–9
5. Yung M, Keeley S. Randomized controlled trial of intravenous maintenance fluids. J Paediatr Child Health 2009;45:9–14
6. Hadimioglu N, Saadawy I, Saglam T, Ertug Z, Dinckan A. The effect of different crystalloid solutions on acid-base balance and early kidney function after kidney transplantation. Anesth Analg 2008;107:264–9
7. Waters J, Gottlieb A, Schoenwald P, Popovich M, Sprung J, Nelson D. Normal saline versus lactated Ringer's solution for intra-operative fluid management in patients undergoing abdominal aortic aneurysm repair: an outcome study. Anesth Analg 2001;93:817–22
8. McFarlane C, Lee A. A comparison of Plasmalyte 148 and 0.9% saline for intra-operative fluid replacement. Anaesthesia 1994;49:779–81