Table IV.

Balance for covariates in 1:1 matching by propensity score comparing participants who received IV magnesium with participants who did not

Variable	Value according to IV magnesium treatment status
	Not treated	Treated	Difference	Standardized difference a	P value
Age, years	9.3141	9.4070	0.0930	0.5262	0.8598
Male gender	0.7042	0.6479	−0.0563	0.0788	0.4748
Race
Black	0.4648	0.5493	0.0845	0.0842	0.3156
White	0.4366	0.3803	−0.0563	0.0828	0.4962
Other	0.0986	0.0704	−0.0282	0.0468	0.5477
Hispanic ethnicity b	0.0704	0.0704	0.0000	0.0431	1.0000
Asthma exacerbation in past year	0.6901	0.6338	−0.0563	0.0797	0.4795
BMI	19.2375	19.0208	−0.2167	0.8654	0.8023
Prior PICU admission for asthma	0.2817	0.2676	−0.0141	0.0752	0.8514
Prior ETI for asthma	0.0282	0.0282	0.0000	0.0279	1.0000
Symptom duration, hours	3.0070	2.3028	−0.7042	0.9401	0.4538
AAIRS before treatment	9.1127	9.1549	0.0423	0.2786	0.8794
Concurrent influenza	0.0000	0.0141	0.0141	0.0141	0.3173
CCS treatment prior to ED arrival	0.3662	0.2958	−0.0704	0.0793	0.3743
Treatments applied in 1st 2-hours
Albuterol MDI	0.0141	0.0141	0.0000	0.0198	1.0000
Albuterol continuous nebulization	0.9437	0.9437	0.0000	0.0388	1.0000
Terbutaline	0.0563	0.0563	0.0000	0.0388	1.0000
Epinephrine	0.1127	0.1268	0.0141	0.0547	0.7967
BiPAP	0.0423	0.0423	0.0000	0.0339	1.0000

Albuterol by one-time nebulized treatment excluded because all participants treated with IV-Mg received this treatment.

Abbreviation: AAIRS, Acute Asthma Intensity Research Score; BiPAP, bilevel positive airway pressure; BMI, body mass index; CCS, systemic corticosteroid; ETI, endotracheal intubation; IM, intramuscular; MDI, metered-dose inhaler; PICU, pediatric intensive care unit

^aStandardized difference, difference between matched pairs divided by standard deviation

^bHispanic ethnicity defined according to NIH policy NOT-OD-01-053