The present study compared different parameters of multiple trauma care among various times of the day. Contrary to the findings in previous studies, we showed that the time of admission had no effect on the length of hospital stay or outcome among multiple trauma patients. We believe that this is evidence that a consistent level of trauma care is available 24 h per day.
Unlike in previous evaluations , the majority of multiple trauma patients were male, irrespective of the time of day they were admitted. Most injuries occur in environments and circumstances that involve sex-based differences in behavior; hence, there is a higher prevalence of all injury mechanisms in males, especially traffic accidents .
The age of multiple trauma patients differed significantly between those admitted during the day and at night. Trauma patients admitted at night were significantly younger than those admitted during the day, which agrees with previous findings .
During the day, many traffic accidents are caused by commuter traffic . The group of multiple trauma patients older than 65 years has increased significantly in recent decades, although older people tend to go out during the day more than they do at night . Traffic accidents at night might be caused by people traveling to various party venues . In particular, alcohol-related crashes involving young drivers are relatively more common at night .
Traffic accidents are the most common cause of multiple trauma . Most car and motorcycle accidents occur in the evening. In Germany, approximately 80% of traumatic injuries are caused by motor vehicle accidents . At noon and during the afternoon rush hour, there are relatively more traffic accidents .
Minor falls are a major cause of accidents. Especially in the elderly population, minor falls are a common cause of multiple trauma, and the number of falls has increased in recent years [28, 29]. Predisposing risk factors that are becoming increasingly important due to the increase in the population of older patients might be comorbidities, age-associated loss of strength or balance and the use of certain medications .
The percentage of suspected suicides was the highest at night. Several studies have found a circadian variation in suicide rates depending on age, with a morning peak for older patients and an evening peak for younger patients . Biologic factors, such as sunshine and daylight cycles, as well as biomarkers, such as melatonin, serotonin and cortisol, play major roles in circadian variations in suicide .
Our study did not identify any substantial difference in the ISS and GCS scores based on the time of day. The highest mean ISS and the lowest preclinical GCS score occurred at night. The percentages of patients with head injuries and penetrating trauma peaked at night. Dim lighting contributes to the severity of traffic injuries . Reaction times are substantially longer under poor conditions . Factors such as fatigue and alcohol contribute to the impaired ability of drivers to avoid severe collisions at night .
Time is critically important in multiple trauma patients . Several authors have shown a correlation between the time to initial trauma care and the long-term outcome . The outcomes differ significantly between emergency patients admitted during the day and at night, and the mortality rate is higher among those admitted at night . Cognitive performance and hand-eye coordination are impaired in professionals working at night . An analysis of the quantity and quality of emergency physicians has shown that physicians working night were slower at intubation and made more errors .
In our evaluation, the prehospital period was longer at night. Emergency treatment, especially in cases of vehicle accidents and those requiring technical rescue, can be complicated and time-consuming in the dark. In addition, rescue stations might not be as well staffed as they are during the day.
Multiple severe injuries necessitate more stabilizing interventions and prolong the out-of-hospital time . There is a general consensus that critical and life-threatening injuries must be managed during the out-of-hospital phase even when this causes delay .
During the night shift, the time spent waiting in the emergency room and time from arrival at the emergency room until the performance of an emergency operation were short and comparable with the times during the day. These findings are contrary to previous results since most hospitals are understaffed at night, and the performance of physicians is worse at night than during the day .
Egol et al. suggested that understaffed hospitals and overfatigued physicians were responsible for the higher mortality at night . A higher risk of mortality at night was also observed for patients admitted to level III and IV hospitals in the United States . We found longer time periods until the performance of CT scans in level III trauma independent of the time of day, but delay did not cause a subsequent delay in the performance of emergency operations or a prolonged hospital stay.
Multiple trauma management in the emergency room seems paradoxical, with fast treatment considered essential, while the precise diagnostic imaging needed is time consuming .
Parsch et al.  evaluated the times to different medical interventions, such as intubation, venous catheter insertion and splinting, during business and nonbusiness hours. There were no differences in the trauma room treatment parameters between the day and night shifts . It may be that the knowledge and experience gained during previous evaluations ensures a consistent level of trauma care even at night. Patients with high ISSs and severe head injuries were found to have longer stays in the emergency department than trauma patients with lower ISSs , but we did not find relevant differences in ISSs in level I trauma centers. Higher ISSs were observed for level III trauma centers at night, but higher ISSs did not correlate with a longer duration of care.
One explanation might be that the implementation of the European Working Time Directive has changed the working conditions in hospitals over the past years [42,43,44]. The primary aim of the law regarding working hours was to protect clinical employees from being made to work overtime for the benefit of patients . Reducing the amount of time spent working, performing shift work and increasing rest time might have helped improve the quality of patient care and accelerated the time to the performance of procedures in all clinical departments at night.
We did not find fundamental differences in the length of stay in the ICU or length of stay in the hospital based on the time of arrival, which correlates with the findings of Morales et al. .
It is generally accepted that the early identification of injuries with rapid resuscitation and management can improve the survival of multiple trauma patients . We evaluated the RISC II score during the day and at night. The RISC II score is a prognostic factor for the outcome, independent of arrival time and level of trauma center . The highest RISC II score occurred in the patients admitted at night, which correlated with an increase in severe head injuries and a lower GCS in our evaluation. Increasing injury severity results in higher RISC II scores .
We found no essential difference between the RISC II score and mortality rate in any time period, which highlights the high prognostic relevance of the RISC II score. There were no differences between the expected and observed mortality rates. The highest RISC II score and highest mortality rate were observed at night. The RISC II score combines different factors that are predictive of the survival of trauma patients .
The specifics of the trauma center and arrival time are not included in this score; therefore, a regression analysis was performed. Our regression analysis showed no correlation between the time of day and mortality rate. Time of arrival and trauma care did not affect the mortality rate. Barbosa et al. evaluated trauma patients who underwent surgery and found that admission at night was an independent predictor of hospital mortality , but there was no focus on multiple trauma patients, and only patients from one public trauma center were included.
Hirose et al. divided a day into two intervals and showed a negative impact of admission at night on the outcome in emergency trauma patients in Japan . The emergency medical services and medical system in Japan differ from those in Europe or the United States, and personnel are on duty for a full 24-h period . Even when materials and medical staff are limited, the optimal provision of trauma care remains critical. Laupland et al. did not find a difference between patients who arrived at night and those who arrived during the day, which may reflect the highly developed trauma care system in Canada . There seems to be a high degree of variation in trauma care, and what holds true in one region is not necessarily applicable in another.
We highlight that the admission of multiple trauma patients at night does not have a negative effect on outcomes or mortality in German trauma centers. These findings reflect the quality of multiple trauma care in German hospitals around the clock. We believe that understanding the difficulties and weaknesses in emergency management at night has fundamentally improved trauma care at night.