To find incidence of hyponatremia in patients administered either of hypotonic or isotonic maintenance fluid for 24 hours

Abstract

Background : Maintenance intravenous fluids are most commonly necessary in hospitalised children who cannot be fed by enteral route,preoperative and postoperative patients.For almost half a century,most of the Paediatricians around the world were using hypotonic solution(0.2% saline in 5% dextrose) for maintenance fluids according to the guidelines set by Holliday and Segar . The wisdom of this approach to intravenous fluid therapy has been questioned recently ,especially in the hospitalised children who have various osmotic and non-osmotic stimuli for vasopressin release, leading to impaired ability to excrete free water along with secondary natriuresis due to suppression of aldosterone release ,thereby increasing the probability of developing clinically symptomatic hyponatremia.We hypothesized that use of isotonic maintenance fluid (0.9% saline in 5% dextrose) would be more safer than hypotonic fluid (0.14% saline in 5% dextrose) in decreasing the incidence of hospital acquired hyponatremia in the sick children at standard maintenance rate. Methods : This open-labelled randomized controlled trial was conducted in the Paediatric emergency of a secondary care hospital.Children in the age group of 0.6 to 12 years who were admitted and anticipated to receive maintenance intravenous fluid for 24 hours were included into the study.Written informed consent was obtained from the parent or guardian of all the patients before participation in the trial.The study protocol was approved by the Institute Ethics Committee.Children with baseline hyponatremia (serum sodium < 135 mEq/L),hypernatremia(serum sodium >145 mEq/L),neurological disorders,acute diarrhoea and dehydration,shock,head trauma,severe acute malnutritrion,those with pre-existing chronic diseases,diabetic ketoacidosis and suspected poisoning were excluded.Children with fluid overload conditions(like cirrhosis, congestive heart failure,acute and chronic renal failure and nephrotic syndrome)or receiving drugs like diuretics,mannitol,vasopressin, carbamazepine which can cause abnormality in the serum sodium were also excluded.Based on findings of Montanana et al,which showed the incidence of hyponatremia in hypotonic group to be 20.6% and in the isotonic group to be 5.1%,with power of 80% and applying 95%confidence interval,a sample size of 125 patients was calculated by web based power/sample size calculator,out of which 63 were randomized to receive isotonic fluid(0.9% saline in 5% dextrose) and 62 for hypotonic fluid(0.14% saline in 5% dextrose)at standard maintenance rate.Both fluids had potassium in the concentration of 20 mEq/L.Randomisation was done by computer generated random number tables. The allocated intervention was kept in sequentially labelled sealed envelopes and was opened after enrolment of the patient.Baseline demographic, hemodynamic characteristics and level of consciousness were noted at presentation.Level of consciousness,heart rate,respiratory rate,blood pressure andSpO2 were monitored every 6 hourly for first 24 hours of admission.Baseline investigations like complete blood counts,serum sodium,serum potassium,blood sugar,renal function tests and those relevant to the patient illness were done. Serum osmolality was calculated at the time of enrolment and after 24 hours by the formula:Serum osmolality=(2 × serum sodium) + (blood sugar/18) + (blood urea/2.8).Serum sodium was repeated after 24 hours of intravenous fluid therapy. All enrolled patients were monitored for signs and symptoms of sodium imbalance,signs of dehydration during first 24 hours. Results : Baseline variables were comparable in two groups. Hyponatremia at 24 hours was seen in 11(17.4%)patients in isotonic and in 29(47%)patients of hypotonic group (P=0.02).The odds ratio for developing hyponatremia in hypotonic group was 4.32(95%CI: 1.89, 9.90)as compared to isotonic group.There were 25 patients (59.5%) of respiratory tract illness who developed hyponatremia in hypotonic group as compared to 6 patients (13.9%)of isotonic group (P=0.001).At 24 hours,both mean serum sodium and mean serum osmolality were significantly lower in hypotonic group as (P=0.002) and (P=0.001) respectively Conclusion : To conclude,the type of fluid is important in deciding the incidence of hyponatremia in hospitalized children. Among the fluids,isotonic fluids are safer choice than the traditional hypotonic fluids in hospitalized children requiring maintenance fluid therapy.Current clinical situations demand such a maintenance solution and volume which maintains tonicity and balance in acute illness,rather than one which merely provides a daily sodium or calorie requirement.