Table 1

Characteristics of included studies

Author(s), year, country	Aim	Design	Setting and participants	Sample size	Outcomes regarding fluid balance monitoring	Key findings
Aitken et al, (2013); UK32	AKI Quality of care	Cohort study	Medical, surgical, AKI	243	Adequate FBD (%), inaccurate FB chart (%)	51.8% of patients with AKI had adequate FBD; 43.4% of the remainder had inaccurate FB charts in case notes.
Alexander and Allen (2011) USA33	Policy for FB monitoring	Quasi-experimental	Medical oncology units	427	Compliance with FBD	Before intervention, 12% of patients with indication of FB monitoring had FBD vs 84% after.
Asfour (2016); Egypt52	Accuracy of FB monitoring	Cross-sectional	ICU except dialysis	100	Accuracy of calculated FB compared with researcher’s calculation	65% of FB charts were accurate and 35% were inaccurate.
Baird et al, (2019); UK42	AKI prediction score	Quasi-experimental	Orthopaedic surgery	78	FB monitoring (%)	Before intervention, 62% had adequate FB monitoring postoperatively vs 66% after.
Davies et al, (2017); UK43	Reduce AKI alerts	Quasi-experimental	Orthopaedic trauma	75	Running hourly input, 6 hourly input subtotal, 6 hourly output subtotal and 24-hour total FB	Before intervention, 80% had running 1 hour totals vs 96% after; 36% had 6 hour output vs 68% after. Before intervention, 12% had 24-hour totals vs 72% after and 32% after 6 months.
Davies et al, (2019); Australia*44	Relationship between calculated FB and BW	Prospective cohort study	ICU, requiring CRRT	61	FB charts with calculation errors (%), median deviation in millilitres	Calculation errors prevalent in 27% of charts. Median daily calculation error: 58 mL (range 1–1464 mL). Median cumulative calculation error: 131 mL (range 1–2405 mL).
Diacon and Bell (2014); South Africa34	FB monitoring and measurement accuracy	Cross-sectional	ICU	103	FBD (%), calculation errors (%), deviation in millilitres	95.1% had FBD. Calculation errors: 68.9% deviated 0–500 mL, 13.5% 500–1000 mL, 6.8% 1001–2000 mL, 5.8%>2000 mL
Eastwood et al, (2012); Australia35	Patients receiving IV fluids (%)	Cross-sectional	All inpatients except ICU, ED and PACU	326	Percentage with FB charts maintained (%)	94% of patients receiving intravenous fluids had FB charts vs 44% receiving no intravenous fluids.
Herrod et al, (2010); UK36	Prevalence of dysnatraemias and precipitating factors	Cross-sectional	Surgery Na<130 or >150 mmol/L	55	Complete FB charts (%) Charts with FB calculated (%), median inaccuracy in FB calculation	28% had complete FB charts before dysnatraemia vs 44% after; 37% of charts had no FB calculation. Median calculation error: 72 mL (IQR 9–313 mL) before dysnatraemia vs 130 mL (IQR 71–400 mL) after
Joslin et al, (2015); UK45	AKI recognition and management	Quasi-experimental	AKI	192	Complete FB chart on first day of AKI (%), days with complete FBD (%)	Before intervention, 25% had completed FB charts on first day of AKI vs 34% (p=0.23) after. Before intervention, FBD was completed in 32% of patient days vs 45% after (p=0.002).
Liaw and Goh (2018); Singapore46	Fluid intake charting	Quasi-experimental	Acute surgery	60	Deduction of input/output at midday and over 24 hours. Calculation of 24 hours FB. Involving patients in fluid intake documentation	Before intervention, 3.3% of the FB charts were complete (midday and 24 hours totalling) vs 100% 1 month and 6 months later. Before intervention, patients were involved in 10% of cases vs 87% 1 month later and 83% 6 months later.
Lim et al, (2021); Singapore53	Ordering and documenting fluid in- and output	Cross-sectional	Acute care hospital	2199	Accuracy of FBD defined by recording in millilitres	Overall accuracy 77%. Oral and intravenous fluids 100% accurate, output accurate in 21% of cases
Madu et al, (2021); UK54	Chart completeness and accuracy	Quasi-experimental	General medicine	82	Accurate measurements, calculation errors, complete documentation	Before intervention, 25% of measurements were accurate vs 39% after 1 month and 5% after 6 months, correct daily totals in 20% vs 40% after 1 month and 15% after 6 months, 14% of charts complete vs 31% after 1 month and 5% after 6 months
Møller et al. (2013); Denmark37	Quality improvement	Prospective cohort study	Acute surgery, PPU	1650	Quality-of-care indicator: daily FBD	Before intervention, 74% had FBD vs 79% after. RR 1.07 (95% CI 1.02 to 1.13; p=0.010)
Perren et al, (2011); Switzerland*38	Accuracy of FBD; agreement w BW	Cross-sectional	ICU	147	Complete FB charts, FB charts with calculation errors	12% were excluded due to an incomplete FB chart; 33% of nurse-registered cumulative FB was inaccurate, errors: −3606 mL to +2020 mL. Mean absolute error of 445±668 mL
Pinnington et al, (2016); UK47	Complete FBD	Quasi-experimental	Three wards	120	Complete FB charts	Before intervention, 32% of FB charts were completed correctly vs 92% after. In AKI patients, 20% had FBD before vs 91% after.
Szmuda et al, (2014); Poland39	Calculation errors; FBD and chart completeness	Cross-sectional	NICU and NHDU, SAH	41	Complete FB charts, FB miscalculations	63.4% of FB charts were complete, 80.2% in NICU and 58.7% in NHDU (p<0.01). Fluid intake miscalculations in 27.4% of charts. Most common errors: underestimating intake (80.6%), omitting drugs (66.9%)
Tura et al. (2020); Ethiopia48	Managing postpartum haemorrhage	Cross-sectional	Obstetric	45	Standard of care criteria: fluid intake/output chart is maintained	In 13.3%, a fluid intake/output chart was maintained.
Vincent and Mahendiran (2015); UK49	Quality of FB monitoring	Quasi-experimental	General medicine	147	FBD, indication of FBD. Chart completion: boxes filled of all total boxes. Accurate totals=<10% error	Before intervention, 67% were on FBD (indicated in 53%) vs 38% after (indicated in 93%). Average chart completion rate before intervention was 50% vs 70% after. Average chart accuracy was 41% before vs 61% after.
Wakeling (2011); UK40	FBD and FB complications; Hydrant drinking aid	Quasi-experimental	Orthopaedic, surgery, urology	313	Complete FB charts (%)	Before intervention, 19%–50% of FB charts were complete vs 29–62% after. Completeness improved (5–18 percentage points).
Walker et al. (2012); UK41	Improve guideline adherence	Quasi-experimental	Acute wards	101	Completion of FB charts	Before intervention, 62.3% had FBD vs 70.8% after (p=0.36).
Yang et al, (2019); Taiwan51	Compliance with FB monitoring	Quasi-experimental	Congestive heart failure	24	FB charts used with electrolytes and physical assessment. Patients involved in FBD	Before intervention, 58% had FB charts with physical assessment vs 100% after; 42% were involved in recording before intervention vs 75% immediately after.
Zhu et al, (2018); China50	Non-pharmacological fever management	Quasi-experimental	Infectious disease, HIV	60	Formal assessment of fluid in- and output volume documented	Before intervention, 0% had fluid input/output documented vs 73% 10 days after intervention.

*Studies addressing cumulative fluid balance.
AKI, acute kidney injury; BW, body weight; CRRT, continuous renal replacement therapy; ED, emergency department; FB, fluid balance; FBD, fluid balance documentation; ICU, intensive care unit; NHDU, neurosurgical high-dependency unit; NICU, neurosurgical ICU; PACU, postanaesthetic care unit; PPU, perforated peptic ulcer; SAH, subarachnoid haemorrhage.