Differential effects of calcium channel blockers combined with various opioids on length of stay in hypertensive cardiac surgery patients: analysis of the MIMIC-IV database.

Emergency medical services (EMS) play a central role in the organization of acute care systems. In many high-income countries, EMS demand has increased in recent decades, and a substantial proportion of missions involve patients with low-acuity conditions who may not require specialist emergency department (ED) care  [–]. Registry-based studies from Nordic and other high-income settings have shown that a considerable share of EMS contacts, including both conveyed and non-conveyed patients, involve non-critical or lower-acuity presentations, raising questions about the optimal destination, triage level, and subsequent use of hospital resources for these patients  [–]. Although the term “low-acuity” is widely used in the international literature, definitions vary between health systems and are typically operationalized using routinely collected clinical or administrative data  []. At the same time, EDs worldwide face persistent crowding and operational strain, including prolonged boarding, access block, and resource constraints  [, ]. Boarding of admitted patients in the emergency department has been identified as a major system-level driver of crowding, associated with delays in care, increased lengths of stay, and adverse patient outcomes  []. System-level factors such as staffing, hospital configuration, and time of arrival have been associated with variation in care processes and outcomes in acute care settings, including trauma populations  [, ]. These structural features may influence diagnostic testing and treatment patterns independently of patient-level clinical severity. Low-acuity EMS conveyances are particularly relevant in this context. Previous studies have examined redirection or alternative care pathways for selected low-acuity patients and have highlighted the complexity of prehospital referral decisions and the potential risk of misclassifying time-sensitive conditions  [, ]. Demographic and temporal factors, including age, sex, and time of arrival, have been associated with differences in ED processes, including the length of stay  []. Registry-based linkage studies have shown that prehospital dispatch characteristics, age, and the time of arrival are independently associated with hospital admission versus discharge following EMS transport  []. However, despite growing interest in EMS utilization and ED crowding, studies directly linking prehospital classification to downstream emergency department diagnostic testing and treatment patterns within the same episode of care remain limited. Linking EMS and hospital data at the mission level enables the direct evaluation of how prehospital urgency classification and conveyance decisions are associated with subsequent emergency department management, an interface that remains underexamined in the literature.