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Background
Transfer of a critically ill patient during uninterrupted intensive care introduces numerous practical hazards [1, 2]. Adverse events, such as serious hypotension or ventilation difficulties may occur and hemodynamic instability before transfer is an important risk factor for complications en route [3]. Notwithstanding, with specialised staffing most patient- or equipment-associated incidents can be detected early and handled safely without impact on mortality [4, 5].
However, circumstantial factors not directly related to patient care may be more difficult to attenuate. The number of days spent in intensive care before transfer is a marker of disease severity associated with risk of death after transfer between intensive care units (ICUs) [6, 7]. Night-time ICU discharge has been associated with increased risk of readmission and hospital death in several studies [8]. A low weekend staff-to-patient ratio may be associated with increased mortality [9]. Intuitively, longer distance with extended time in transit during inter-hospital transfer may infer more problems than a shorter transfer.
Notwithstanding, unit-to-unit referral of critically ill patients is part of many health care systems, necessitated for different reasons. In Sweden, transfers between ICUs are registered and categorised in the Swedish Intensive Care Registry. A recent study, using data from all transfers registered over three years, found that patients submitted to transfer due to lack of resources (capacity transfer), suffered a higher risk of death at 30, 90 and 180 days compared to patients transferred for other reasons [10].
The primary aim of this study was to analyse, for all inter-hospital transfers, whether any of the circumstantial factors ICU length of stay before transfer, night-time or weekend transfer, distance travelled or the capacity transfer category was associated with the risk of death 30 days after transfer. Secondly, we wanted to analyse for inter-hospital capacity transfer if any of the other circumstantial factors was associated with an increased risk of death at 30 days.
Methods
This was a cohort study based on data from the Swedish Intensive Care Registry; www.icuregswe.org. After ethical approval (Swedish Ethical Review Authority, Dnr 2020–07089), data retrieval was formally applied for and granted by the board of the registry. In the data set, individual patients were pseudomised, only identifiable by a code number for which the key was not released from the registry. The...