Prior to the COVID-19 pandemic a flexible approach to visiting was adopted by many Intensive Care Units in the United Kingdom. Due to the rapid spread globally of COVID-19, significant policy changes were put in place, including the restriction on visitors to patients in hospital. Evidence has emerged demonstrating the negative impact of these restrictions on patients with COVID-19, their families and the staff caring for them. However, there is limited data about the impact of these restrictions in the non-COVID ICU environment. This study aimed to explore the experiences of staff caring for non-COVID-19 patients in a cardiothoracic critical care unit during the COVID-19 pandemic. This qualitative research study adopted a grounded theory methodological approach. This methodology was used due to the unique situation, with no prior research available. We recruited healthcare staff that worked in a cardiothoracic critical care unit during the COVID-19 pandemic. Semi structured interviews were carried out, transcribed, and analysed. Using the data collected, a theory was constructed. Interviews were carried out with 20 healthcare staff from a range of professions including nurses, doctors, and allied health professionals. Following data analysis four main categories emerged from the data: impact and implementation of visiting restrictions; the dehumanisation of patients; end-of-life care and witnessing distress. From these four categories, a theory has emerged suggesting that healthcare staff in a non-covid ICU were regularly exposed to potentially moral injurious events, despite being shielded from caring for patients with COVID-19. This study provides a theory that healthcare staff caring for non-COVID-19 critical care patients during the period of visiting restrictions were exposed to potentially morally injurious events. Repeated exposure to potentially morally injurious events can lead to the development of moral injury and its adverse consequences. This study highlights the need to support all staff in the post COVID era, including those who worked in a non-COVID environment.