(1222) Evaluation of Serum Magnesium Levels in Status Asthmaticus to Avoid Toxicity in an Asthma Pathway

Introduction: Magnesium sulfate (MgSO4) infusions are adjunct in status asthmaticus (SA)–a leading cause of PICU admissions. High levels of magnesium (Mg) may lead to detrimental effects, requiring close monitoring. Adjustments may be required to reach therapeutic levels while avoiding toxicity, making protocolization of MgSO4 administration difficult. This study evaluates serum Mg levels and titration adjustments for improved protocolization of MgSO4 therapy in SA.

Methods: Retrospective study of PICU SA patients started on a MgSO4 infusion as part of an institutional Mg asthma pathway over 14 months. In addition to standard asthma therapies, the Mg adjunct pathway has a MgSO4 75mg/kg bolus (max 2g) followed by a 50 mg/kg/hr (max 2g/hr) infusion. Infusions are subsequently titrated based on serum Mg levels obtained every 4 hours (goal level 4-5 mg/dL). Serum Mg levels were analyzed in relationship to bolus dose timing and infusion rates stratified based on demographics, including age, sex, BMI, and pediatric asthma severity (PAS) score. Correlation between Mg levels, PICU length of stay (LOS) and time to q2h albuterol were assessed.

Results: 253 Mg levels among 51 patients were evaluated. Levels checked before 4 hours were more likely to be subtherapeutic (56% vs 44%, p=0.002). 83.3% (5/6) patients who received a bolus or increased infusion rate in response to a level checked before 4 hours were subsequently supratherapeutic. Supratherapeutic patients were older than those with levels in the target or subtherapeutic ranges (7.5 vs 4 years, p=0.045). There were no significant correlations between sex, BMI, renal or hepatic function and supratherapeutic levels. Patients with supratherapeutic Mg levels had longer PICU LOS (1.7 vs 1.2 days, p=0.035) and time to q2h albuterol (22.1 vs 13.4 hr, p=0.004).

Conclusions: Patients with supratherapeutic Mg levels had longer PICU LOS and time to q2h albuterol, suggesting that increasing the current target is unlikely to yield clinical benefit. Association between age and supratherapeutic levels may suggest that older patients would benefit from a lower initial infusion rate. Checking a safety level early may be desired, but uptitrations should not be considered until the 4h lab as this trended towards supratherapeutic levels.