Outcomes in Vaso-Occlusive Crisis Treatment in the Emergency Department Vs. Acute Care Observation Center

INTRODUCTION: Acute painful vaso-occlusive crises (VOC) are the leading cause of emergency department (ED) encounters and hospital admissions for those with sickle cell disease (SCD). For SCD patients, the goal of the sickle cell acute care observation unit (ACOU) at University of Illinois Health (UIH) is to improve patient outcomes by providing immediate care for an uncomplicated VOC. At our urban hospital which cares for more than 500 adult SCD patients, a considerable portion of SCD patients, despite having access to the ACOU, continue to present to the ED for treatment of an uncomplicated VOC. In order to help improve our current system, this study investigated outcomes in SCD patients who receive care for an uncomplicated VOC in the ACOU versus the ED at UIH.

METHODS: By querying the electronic medical record, a retrospective study was conducted to analyze outcomes of encounters from the ACOU and ED at UIH between October 2019 and December 2019, specifically including SCD patients ≥18 years old who received morphine for treatment of an uncomplicated VOC. Encounters for complicated VOCs such as acute chest syndrome and stroke were excluded. Endpoints collected include time to first dose of morphine, total milligrams (mg) of IV morphine equivalents given, number of total morphine doses, admission rates, subsequent hospital length of stay, and 30-day inpatient admission rates. Time to the first dose (log transformed) and total dose in mg were analyzed by linear mixed effects models. The number of doses and hospitalization days were analyzed by negative binomial mixed effects model. Admissions and 30-day admissions were analyzed by logistic mixed effects models. These models adjusted for age, gender, and severe Hb genotype (HbSS or HbS beta⁰-thalassemia) and treated patient identity as random effect. P values were obtained from Wald- test.

RESULTS: The ACOU data set contains 394 patient encounters for 79 patients with a median age of 33 years (interquartile range [IQR], 28-40), 71% female, and 73% with severe sickle genotypes. The ED data set contains 391 patient encounters for 128 patients with a median age of 30 years (IQR, 26-41), 53% female, and 74% with severe sickle genotypes. In the ACOU, the median time to first dose of morphine was 49 minutes (IQR, 39-60) compared to 107 minutes (IQR, 71-194) in the ED. The time to first dose was significantly longer in the ED compared to the ACOU (e^β=2.5, p <2×10^-16). There was no significant difference in the total number of morphine doses received nor the total mg of morphine received between the two locations. Admission rate from ACOU was 6.6% compared to 53% from ED (OR=0.019, p=2x10^-16). Of those admitted, the median number of hospitalization days from the ACOU was 4 days (IQR, 2.3-5.8) and 4 days (IQR, 2.0-6.5) from the ED. There was no significant difference in hospitalization days (p=0.6). The 30-day admission rate was 55% from the ACOU compared to 58% from the ED. 30-day admission rate however had strong intra-patient correlation (i.e., a patient was likely re-admitted multiple times): 44% of patients from the ACOU had admissions within 30 days of their ACOU visit compared to 32% from the ED. Controlling for the intra-patient correlation, ACOU visits had a higher 30-day admission rate than ED visit (OR=2.8, p=0.0015).

DISCUSSION: SCD patients treated for an uncomplicated VOC at the sickle ACOU at UIH had a significantly shorter time to initial dose of IV pain medication. The wait time in the ED before first dose of IV pain medication received was more than double than those treated in the ACOU. Patients treated for an uncomplicated VOC in ACOU and ED had similar hospitalization days without a statistically significant difference. The 30-day admission rate to the inpatient setting was comparable for those treated in the ED versus the ACOU. However, given that only 6.6% of patients from the ACOU were admitted during the study period, this suggests that most patients who use both the ED and ACOU tend to be subsequently admitted from the ED. SCD patients may be presenting to the ED for treatment of VOC if capacity in the ACOU is exceeded or are presenting outside of hours of operation (currently 2 shifts Monday through Saturday). Therefore, improving access to our ACOU by increasing capacity and hours of operation may subsequently also lead to a decrease in time to first dose of medication and decrease in the overall 30-day admission rate.