Identifying high-risk patients, particularly in intensive care units (ICUs), enhances treatment and reduces severe outcomes. Since the pandemic, numerous studies have examined COVID-19 patient profiles and factors linked to increased mortality. Despite six pandemic waves, to the best of our knowledge, there is no extensive comparative analysis of patients’ characteristics across these waves in Portugal. Thus, we aimed to analyze the demographic and clinical features of 1041 COVID-19 patients admitted to an ICU and their relationship with the different SARS-Cov-2 variants in Portugal. Additionally, we conducted an in-depth examination of factors contributing to early and late mortality by analyzing clinical data and laboratory results from the first 72 h of ICU admission. Our findings revealed a notable decline in ICU admissions due to COVID-19, with the highest mortality rates observed during the second and third waves. Furthermore, immunization could have significantly contributed to the reduction in the median age of ICU-admitted patients and the severity of their conditions. The factors contributing to early and late mortality differed. Age, wave number, D-dimers, and procalcitonin were independently associated with the risk of early death. As a measure of discriminative power for the derived multivariable model, an AUC of 0.825 (p < 0.001; 95% CI, 0.719–0.931) was obtained. For late mortality, a model incorporating age, wave number, hematologic cancer, C-reactive protein, lactate dehydrogenase, and platelet counts resulted in an AUC of 0.795 (p < 0.001; 95% CI, 0.759–0.831). These findings underscore the importance of conducting comprehensive analyses across pandemic waves to better understand the dynamics of COVID-19.

识别高危患者，尤其是重症监护病房 （ICU） 患者，可增强治疗并减少严重后果。自大流行以来，许多研究检查了 COVID-19 患者概况和与死亡率增加相关的因素。尽管有六波大流行，但据我们所知，葡萄牙没有对这些浪潮中患者特征进行广泛的比较分析。因此，我们旨在分析 1041 名入住 ICU 的 COVID-19 患者的人口统计学和临床特征，以及他们与葡萄牙不同 SARS-Cov-2 变体的关系。此外，我们通过分析入住 ICU 前 72 小时的临床数据和实验室结果，对导致早期和晚期死亡的因素进行了深入检查。我们的研究结果显示，由于 COVID-19 导致 ICU 收治人数显着下降，在第二波和第三波期间观察到的死亡率最高。此外，免疫接种可能显着有助于降低 ICU 收治患者的中位年龄及其病情的严重程度。导致早期和晚期死亡的因素不同。年龄、波数、 D-二聚体和降钙素原与早逝风险独立相关。作为衍生的多变量模型的判别能力的度量，获得了 0.825 的 AUC （p < 0.001;95% CI，0.719–0.931）。对于晚期死亡率，结合年龄、波数、血液系统癌症、C 反应蛋白、乳酸脱氢酶和血小板计数的模型导致 AUC 为 0.795 （p < 0.001;95% CI，0.759-0.831）。这些发现强调了跨大流行浪潮进行全面分析以更好地了解 COVID-19 动态的重要性。