Emergency department crowding and cardiac arrest: A retrospective time-series study

Hospitals are designed to be places of healing, but they often function as pressure cookers. When too many sick people arrive at once, the emergency department can become overwhelmed, a state experts call crowding. This happens when the number of patients waiting for care exceeds the number of available beds and staff. Crowding is known to slow down treatment, increase the chance of mistakes, and make it harder for doctors and nurses to spot when a patient is getting worse. While it is well known that a crowded emergency room is a stressful place for everyone involved, a specific and dangerous outcome has remained largely unexplored: the link between this overcrowding and cardiac arrests that happen right inside the emergency department. A cardiac arrest is a sudden stop of the heart, a medical emergency where every second counts. Understanding whether the sheer volume of people in the room makes these sudden stops more likely is a question that could change how hospitals manage their busiest days.

Researchers at North Zealand Hospital in Denmark decided to investigate this connection by looking at their own records over a period of more than three years. They focused on a specific measure of crowding: the occupancy rate. This is a simple count of how many patients are physically present in the department compared to the number of treatment spots available, such as beds, chairs, and stretchers. If there are thirty-three treatment spots and thirty-three patients are in the building, the occupancy rate is one hundred percent. If there are forty-four patients, the rate jumps to one hundred and thirty-three percent, meaning the department is stretched beyond its intended capacity. The team examined daily records of every patient who walked through the doors and every time a cardiac arrest occurred within those walls. They wanted to see if days with higher occupancy rates were also days with more cardiac arrests.

The study covered nearly 1,200 days and included almost 160,000 patient visits. During this time, there were 72 cardiac arrests that happened after patients arrived but before they were moved to another part of the hospital. The researchers found a clear pattern: on days when the emergency department was more crowded, cardiac arrests were more frequent. Specifically, for every ten percentage points the occupancy rate went up, the rate of cardiac arrests increased by twenty-two percent. The difference was most stark when comparing days that were not crowded to days that were severely overcrowded. On days when the number of patients exceeded the available spots by thirty percent or more, the rate of cardiac arrests was nearly six times higher than on days when the department had space to spare. This association held true even after the researchers accounted for other factors like the day of the week, the time of year, and the general passage of time.

To test whether fixing the crowding could fix the problem, the hospital had previously introduced a new way of working designed to move patients through the system faster. This new approach involved nurses quickly sorting patients, getting blood tests done early, and creating a dedicated path for those who needed less intensive care. This change was implemented in early 2023. After the new system was in place, the hospital saw a dramatic drop in overcrowding. The number of days where the department was packed beyond its limits fell from more than half of all days to less than one-fifth. At the same time, the overall rate of cardiac arrests in the emergency department dropped significantly, falling from about 6.6 events per 10,000 visits to just under 2.8.

However, the researchers were careful not to claim that the new system directly caused the drop in cardiac arrests. When they looked closely at the exact moment the new system started, the data did not show an immediate, statistically significant jump or drop in cardiac arrest rates that could be tied solely to the change in management. The decline in arrests happened gradually over time, alongside the decline in crowding, but the study could not prove that one caused the other. It is possible that the new system helped, or it could be that other changes in how the hospital operated during those years contributed to the improvement. The study also checked to see if patients who did not have a cardiac arrest in the emergency room simply had one later, once they were moved to a regular hospital ward. They found no evidence of this; the rate of arrests in the wards did not go up to make up for the drop in the emergency room.

The findings suggest a strong link between how full an emergency department is and how often patients suffer cardiac arrests within it. When the department is packed, with patients waiting in hallways and staff stretched thin, the risk of a sudden heart stop appears to rise. While the study cannot say for certain that crowding causes these arrests, the connection is too strong to ignore. The researchers noted that a crowded environment might make it harder to notice a patient getting worse, or it might delay the care needed to prevent a crisis. The study serves as a reminder that the physical state of a hospital room matters as much as the medical skills inside it. It points to the need for more research to understand exactly how overcrowding leads to these tragic events and to confirm whether reducing the crowd can save lives. For now, the data from North Zealand Hospital tells a clear story: when the emergency department is at its most crowded, the most critical events happen more often.