CHARACTERIZING THE FLOW OF SHORT-STAY PATIENTS IN THE INTENSIVE CARE UNIT

Purpose: Intensive care unit (ICU) volume continues to grow despite limited bed capacity, increasing the need for optimizing ICU patient flow.  We sought to characterize “short-stay” patients (those booked for transfer within 24 hours) by acuity and throughput out of the ICU.  

Methods: We obtained patient-level emergency department (ED) to Medical-ICU (MICU) admissions data from September 2010 to June 2011 for Yale-New Haven Hospital, which contains 40 MICU beds and 15 step-down unit (SDU) beds.  We also obtained MICU and Medicine Service (floor) census data, at four time points each day.  Patients were designated as “acute” if they met Society for Critical Care Medicine Guidelines for ICU Admission or received a critical care-level intervention, versus “sub-acute” if they met neither criterion.  Throughput data included ICU admission time, ICU service time, and ICU wait-time for transfer to the floor/SDU.  We performed a linear regression on ICU transfer wait-time and census levels, using ordinary least-squares, to investigate the impact of hospital crowding on patient throughput.   

Results:   970 patients were admitted from the ED to ICU over nine months, including 434 (37.5%) short-stay patients, of whom approximately 50% were classified as sub-acute.  Short-stay patients had an average ICU service time of 14.1 hours, followed by an average wait time of 10.0 hours for transfer to the floor/SDU (Table 1).  Although average ICU service time for non-short-stay patients exceeded three days, wait time for transfer was similar at 11.6 hours.  Overall wait-time for transfer out of the ICU decreased by 0.72 hours [SE: 0.12, p<0.0001] for each patient in the ICU census, and increased by 0.11 hours [SE: 0.02, p<0.0001] for each patient in the floor census, after controlling for time of day fixed-effects.   

Conclusions: Empirical results indicate that patient crowding in the ICU and floor significantly impacts transfer wait-times out of the ICU, suggesting that the ICU is currently under strain.  Short-stay ICU patients spend a substantial proportion of their ICU length of stay waiting for transfer out of the ICU, resulting in bottlenecks for other critically-ill patients.  Half of these short-stay patients did not meet published admission guidelines nor receive critical care interventions, suggesting that they may not clinically warrant ICU stays.  Identifying and triaging sub-acute patients to alternate units may improve ICU bed availability and throughput.