Reduction in Radiation Exposure through a Stress Test Algorithm in an Emergency Department Observation Unit.

INTRODUCTION: Clinicians are urged to decrease radiation exposure from unnecessary medical procedures. Many emergency department (ED) patients placed in an observation unit (EDOU) do not require chest pain evaluation with a nuclear stress test (NucST). We sought to implement a simple ST algorithm that favors non-nuclear stress test (Non-NucST) options to evaluate the effect of the algorithm on the proportion of patients exposed to radiation by comparing use of NucST versus Non-NucST pre- and post-algorithm. METHODS: An ST algorithm was introduced favoring Non-NucST and limiting NucST to a subset of EDOU patients in October 2008. We analyzed aggregate data before (Jan-Sept 2008, period 1) and after (Jan-Sept 2009 and Jan-Sept 2010, periods 2 and 3 respectively) algorithm introduction. A random sample of 240 EDOU patients from each period was used to compare 30-day major adverse cardiac events (MACE). We calculated confidence intervals for proportions or the difference between two proportions. RESULTS: A total of 5,047 STs were performed from Jan-Sept 2008-2010. NucST in the EDOU decreased after algorithm introduction from period 1 to 2 (40.7%, 95% CI [38.3-43.1] vs. 22.1%, 95% CI [20.1-24.1]), and remained at 22.1%, 95% CI [20.3-24.0] in period 3. There was no difference in 30-day MACE rates before and after algorithm use (0.1% for period 1 and 3, 0% for period 2). CONCLUSION: Use of a simple ST algorithm that favors non-NucST options decreases the proportion of EDOU chest pain patients exposed to radiation exposure from ST almost 50% by limiting NucST to a subset of patients, without a change in 30-day MACE.

Platelet function recovery following exposure to triple anti-platelet inhibitors using an in vitro transfusion model.

INTRODUCTION: Dual anti-platelet therapy (DAPT) with aspirin and a P2Y12 antagonist is standard of care to reduce risk of thrombosis, but does not directly target thrombin-dependent platelet activation. Therefore, PAR-1 antagonist addition to DAPT (i.e., triple anti-platelet therapy; TAPT) may improve the efficacy of treatment, though at the expense of an increase in bleeding risk. Using an in vitro transfusion model, we evaluated if platelet function loss associated with TAPT can be remedied by the addition of drug-naïve platelets. METHODS: To mimic TAPT, platelet-rich plasma (PRP) prepared from consented DAPT patients (DPRP) was incubated with a vorapaxar at therapeutic plasma levels (TPRP). To simulate platelet transfusions, TPRP was mixed with increasing proportions of drug-naïve PRP (NPRP). Platelet function recovery was assessed by light transmission aggregometry (LTA), aggregate morphology, and P-selectin expression. RESULTS: LTA results demonstrated that 20% NPRP was required to restore the ADP aggregation response in TPRP to the response observed in DPRP and 40% NPRP recovered aggregation to >65%. Higher NPRP fractions (60%) were required to restore the platelet reactivity using TRAP-6 (SFLLRN) or arachidonic acid (AA). PAR-4 aggregation was unaffected by platelet antagonists. A decrease in single, free platelets and incorporation of mepacrine-labeled naïve platelets into aggregates occurred with increasing NPRP portions. Upon agonist activation, the surface density and percent of P-selectin positive platelets increased linearly upon addition of NPRP. CONCLUSION: This in vitro model demonstrated that administration of drug-naïve platelets can be a useful strategy for reversing overall platelet inhibition observed with TAPT.