Characteristics of the included studies
| Study | Study design | Age (years) | No of participants | Length of ICU admission | Nursing ratios | LOS (days) | Flap loss | Total hospital charges (mean) | Outcomes |
| Nkenke et al 2009 Germany18 | PS | Mean (SD) ICU=62.8 (9.7) Non-ICU=63.5 (9.5) | ICU=50 Non-ICU=50 | Mean (SD) 3.5 (10.9) | NR | Mean ICU=10.28 Non-ICU=9.89 | 1 | NR | Flap loss and other complications, readmission, length of hospital stays and hospital cost |
| Arshad et al 2013 USA9 | RS | Mean ICU=59.2 Non-ICU=58.9 | ICU=131 Non-ICU=126 | NR | NR | Mean ICU=10.28 Non-ICU=9.89 | 9 | ICU was US$2134 greater than non-ICU | Flap failure, LOS, hospital cost and other complications. |
| Yang et al 2019 USA20 | RS | Mean (SD) 64.28 (11.70) | ICU=205 Non-ICU=100 | NR | NR | Mean (range) ICU=6 (5–8). Non-ICU=5 (5–7) | 9 | 35% higher hospital costs in ICU | Flap loss, reoperation, readmission, LOS, other complications. |
| Panwar et al 2015 USA11 | RS | Mean (SD) ICU=62.46 (13.5) Non-ICU=63.3 (11.6) | ICU=175 Non-ICU=72 | NR | 1:3 to 1:4 | Mean (range) ICU=8 (7–11) Non-ICU=7 (6–9.5) | 9 | Mean (range) ICU=US$33 642 (US$28 143–US$43 196; non-ICU= US$28 524 (US$22 611–US$33 226) | Flap failure, in-hospital mortality, and morbidity, hospital length of stay (LoS), total hospital-based charges, and cost of care, operative time, ischaemia time, site of tissue harvest. |
| Chen et al 2018 Taiwan21 | RS | Mean (SD) ICU=53.8 ± 10.3 Non-ICU=52.2 ± 9.6 | ICU=138 Non-ICU=179 | NR | 1:2 in the ICU; 1:9 during the day, 1:12 in the evening, and 1:16 in night shift in the ward | Mean (SD) ICU=22.1 ± 13.1 Non-ICU=24.2 ± 13.9 | 8 | NR | Ventilation length, use of sedation, flap outcomes, flap complications, systemic complications, in-hospital mortality, and hospitalisation. Flap outcomes |
| Yalamanchi et al 2020 USA22 | RS | Mean (SD) ICU=64.6 (13.0) Non-ICU=61.5 (13.2) | ICU=146 Non-ICU=192 | Mean 7 (IQR 6–9) days | 1:3 | Mean (IQR) ICU=8.5 (6–9) Non-ICU=8 (4–8) | 13 | Mean ICU= US$47 315.44 Non-ICU= US$38 853.50 | Postoperative complications, reoperation, and flap failure, ICU length of stay, total LOS, readmission rates, and hospital cost. |
| Cervenka et al 2019 USA17 | RCT | >18 | ICU=57 Non-ICU=61 | ICU for 12–24 hour | 1:3 and 1:4 | Mean (range) ICU=8.89 (4–30). Non-ICU=8.97 (4–21). | 1 | Mean ICU= US$466 199 Non-ICU= US$486 150 | LOS, flap failure rate, surgical and medical complications and total cost of hospitalisation |
| Clemens et al 2015 USA19 | RS | Mean (SD) 60 (14.1) years | 680 ICU=605 Non-ICU=75 | NR | NR | Non-ICU=5.9 6 (1.8) ICU=9.56 (7.5) | 10 | NR | Flap failure rate, LOS, minor and major complications |
ICU, intensive care unit; LOS, length of hospital stay; NR, not reported; PS, prospective study; RCT, randomised controlled trail; RS, retrospective study.