The recent report by Shamim, et al. [1] brings out the most common and continued problem encountered in pediatric intensive care units. Research has proved that using isotonic fluids as maintenance fluids in sick children results in fewer hyponatremic episodes compared to hypotonic fluids [2,3]. However, there are few issues:

The statistics could have been extended to see how many children will be harmed if used hypotonic fluids compared to reduced volume isotonic fluids. The number needed to harm in this trial (to cause hyponatremia), if using hypotonic fluids, would be 1 in 4 at 24 hours (95% CI 1.9-15.2) and 48 hours (95% CI 1.9-11.8), which is higher compared to an earlier study [2]. The absolute risk increases by 30 percent if hypotonic fluids are used. However, the earlier trial used the same volume of fluids in both the participant groups which points towards a need of reduced volume rather than standard volume maintenance fluids apart from employing isotonic fluids, to reduce hyponatremia.

The participants in both groups received 1 mL of potassium chloride per 100 mL of intravenous fluids. The isotonic group compared to hypotonic group has received lesser potassium maintenance, as the volume was reduced to 60 percent in this group. However, there was no hypokalemia in the isotonic group. The potassium maintenance should have been adjusted so that the both groups received the same amount of potassium.

The study also had limitation of not measuring the urine osmolality. The basic principle to prevent hyponatremia in pediatric intensive care depends on the amount of free water given which further depends on the solute load (intravenous fluids) and urine osmolality. During the sickness the vasopressin levels would be high resulting in high urine osmolality. Hyponatremia can still occur in children given isotonic fluids at reduced volume which is also seen in this study.

It is very clear that the maintenance fluids used in sick children should be isotonic with reduced standard volume to prevent hyponatremia. How far and how much to reduce depends on the sickness of the child. If the child is very sick, the fluid reduction should be higher. In extreme sickness, the question to further reduce maintenance fluids or to increase the solute concentration in the maintenance fluids remains unanswered?

1. Shamim A, Afzal k, Manzir AS. Safety and efficacy of isotonic (0.9%) vs. Hypotonic (0.18%) saline as maintenance intravenous fluids in children: A randomized controlled trial. Indian Pediatr. 2014;51:969-74.

2. Montanana PA, Modesto AV, Ocon AP, Lopez PO, Lopez PJL, Toledo PJD. 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.