Long-term outcomes in COVID-19 patients admitted to intensive care unit in Norway

- An observational cohort study

Abstract

The COVID-19 pandemic was officially announced in March 2020 and resulted in a large cohort of patients needing intensive care unit (ICU) treatment. The most severely ill COVID-19 patients required ICU treatment due to respiratory failure, resulting in extended stays in the ICU. Some also developed acute respiratory distress syndrome, which has high mortality rates in the ICU. Being critically ill is also associated with long-term symptoms and impairments that can last for months and years after discharge from the hospital. During the two recent decades, the knowledge about long-term outcomes after respiratory failure and ICU treatment has increased, highlighting the complexity of recovery from critical illness. One of the frameworks developed is post-intensive care syndrome (PICS), which includes mental, physical, and cognitive impairments emerging after acute hospitalisation and persisting after discharge from the hospital. We used the PICS framework to investigate long-term symptoms and impairments in this new cohort of ICU patients during the first year after their ICU admission. In addition, we investigated which of the selected clinical and sociodemographic factors were associated with these outcomes. This thesis is part of a larger prospective observational cohort study investigating mortality and long-term outcomes after ICU treatment due to COVID-19 in Norway. Symptoms of post-traumatic stress, cognitive impairment and fatigue were chosen as the primary outcomes in the three papers comprising this thesis, thereby focusing only on the longterm outcomes. We included adult patients with confirmed COVID-19 and registered in the Norwegian Intensive Care and Pandemic Registry from 1 March 2020 until 30 June 2021. The project was a collaboration between the registry and Oslo University Hospital. The project employed both registry data and data collected through telephone interviews, including pre-ICU data, clinical data from the ICU, patient-reported outcome measures and a neurocognitive test. In the first paper, we presented preliminary results from the first wave of COVID-19 patients admitted to ICU in Norway and found that 22.5% of these patients reported having symptoms of post-traumatic stress six months after ICU admission. Being younger, having female sex, and having a high respiratory rate at admission to the hospital were all independently and statistically significantly associated with this outcome. In paper II, we found a statistically significant decline in cognitive impairment defined by a neurocognitive test, from 23.1% at 6 months to 11.1% at 12 months after ICU admission. Older age and reporting symptoms of depression were associated with cognitive impairment at six months, while older age and being frail before ICU admission were associated with cognitive impairment at 12 months. In exploratory analyses, we found that subjective cognitive complaints were noticeably more prevalent than cognitive impairment at the 12-month follow-up, as almost half of the patients reported worse memory, more difficulty concentrating, and more difficulties finding the correct word. Feeling tired was associated with reporting subjective cognitive complaints. In the third and final paper, we found that fatigue was one of the most prevalent symptoms in our study sample. Three out of four patients scored above the cut-off in the fatigue questionnaire at the three-month follow-up, while almost two-thirds still reported fatigue at the 12-month follow-up. Younger age, symptoms of mental health issues (depression and post-traumatic stress), pain/discomfort, and dyspnoea were associated with reporting fatigue. In conclusion, we found that COVID-19 ICU survivors in Norway had a high total symptom burden during their first year after ICU admission. Our results suggest that this patient population should be offered a broad symptom screening through ICU out-patient clinics to identify the need for further follow-up and rehabilitation.