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Abstract

Introduction: Due to concerns regarding high sodium loads in children with recovering cardiac function, use of hypotonic parenteral maintenance fluid therapy in children after cardiac surgery is still common at most centers. To our knowledge however, no data exists to date comparing different maintenance fluid strategies in this patient population. We aimed to compare the use of 0.45% saline to 0.2% saline in parenteral maintenance fluid therapy in children recovering from cardiac surgery. Methods: An IRB-approved retrospective study was conducted on children ≤ 12 years of age who underwent cardiac surgery with cardiopulmonary bypass at our institution from 8/15/2012–8/14/2013 and recovered in the ICU for at least 48 hours. Patients from 2/15/2013 - 8/14/2013, who received 0.45% saline as part of parenteral maintenance fluid therapy, were compared to patients from 8/15/2012 - 2/14/2013, who received 0.2% saline, using t-tests, Mann-Whitney U tests, or χ-square tests as appropriate. Sodium values were recorded for up to seven ICU days post-operatively. Data are provided as mean±standard deviation unless otherwise noted. Results: Sixty-nine patients receiving 0.45% saline and 74 receiving 0.2% saline were reviewed. Median ages of those receiving 0.45% and 0.2% were 6.3 months (range: 0.03–142) and 6.6 months (range: 0.17–120), respectively, P=0.72. Baseline sodium was 143.6 ± 0.3 meq/dL in patients receiving 0.45% and 144.5 ± 0.4 meq/dL in patients receiving 0.2%, P=0.10. In patients receiving 0.45% however, hyponatremia occurred less often (35% versus 52%, P=0.03), lowest sodium measured was higher (135.7 ± 0.5 meq/L versus 134.2 ± 0.4 meq/dL, P<0.016), and mean change in sodium from baseline was lower (7.9 ± 0.5 meq/L versus 10.3 ± 0.6 meq/dL, P=0.003). Of note, the number of post-operative ICU days on which sodium measurements were obtained was similar between groups, 4.5 ± 0.2 (0.45%) versus 4.4 ± 0.2 (0.2%), P=0.90. Unexpectedly, peak sodium was lower in those receiving 0.45%, 148.2 ± 0.4 meq/L versus 149.3 ± 0.4 meq/dL, P=0.04. Lastly, median ICU stay was not statistically different between groups, 4 days (intraquartile range: 3–14.5) in patients receiving 0.45% and 6 days (intraquartile range: 4–14) in patients receiving 0.2%, P=0.385. Conclusions: Use of 0.45% saline as compared to 0.2% saline as part of parenteral maintenance fluid therapy is associated with a lower incidence of hyponatremia but not a greater incidence of hypernatremia or prolonged ICU length of stay. Future research comparing isotonic parenteral maintenance fluid therapy to 0.45% saline is warranted in this patient population.