Introduction
Method
Population | Concept | Context | Types of sources |
---|---|---|---|
Inclusion criterion: studies of the hospital volume-outcome relationship in surgery, the methodology of which was described in sufficient detail for the extraction of all requisite data. Exclusion criterion: studies of surgeon-specific volume-outcome relationships. | Inclusion criterion: methods used to assess the hospital volume-outcome relationship in surgery. Exclusion criterion: studies in which (i) the hospital volume was a covariate in a model and (ii) the impact of volume per se was not apparent. | Inclusion criteria: all types of surgery, all types of patient-related outcome (length of stay, mortality, morbidity, cost, etc.), all countries. Exclusion criteria: none. | Inclusion criterion: primary quantitative research publications written in English and published after 2009. Exclusion criterion: studies with other designs. |
Database | Keywords and query |
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PUBMED | Keywords: Volume, outcome, hospital, surgery, surgical, mortality, morbidity, cost Query: (“Volume-outcome” OR “Volume-mortality” OR (“hospital volume” AND (“outcome” OR “mortality” OR “morbidity” OR “cost”))) AND (“surgery” OR “surgical”) AND “hospital” NOT “surgeon”[TITLE] |
Scopus | Keywords: Volume, outcome, hospital, surgery, surgical, mortality, morbidity, cost Query: TITLE-ABS-KEY ((“Volume-outcome” OR “Volume-mortality” OR (“hospital volume” AND (“outcome” OR “mortality” OR “morbidity” OR “cost”))) AND “surgery” AND “hospital”) AND NOT TITLE(“surgeon”) AND (LIMIT-TO (PUBSTAGE, “final”)) AND (LIMIT-TO(DOCTYPE, “ar”)) AND (LIMIT-TO (LANGUAGE, “English”)) |
Criteria | Review Result |
---|---|
Inclusion criteria: | |
Assessment of the hospital volume-outcome relationship in surgery | ❒ Yes ❒ No |
A precise description of the methodology (how the outcome was assessed, how the hospital volume was analyzed, and how the statistical analysis was performed). | ❒ Yes ❒ No |
Exclusion criteria: | |
Surgeon-specific volume-outcome relationship only | ❒ Yes ❒ No |
Hospital volume used only as a covariate | ❒ Yes ❒ No |
Publication as systematic review, qualitative study, editorial, letter to the editor, comment, narrative report, or any format other than primary quantitative research | ❒ Yes ❒ No |
Type of data analyzed | Inclusion and exclusion criteria | Outcome | Confounders | Help in the results interpretation | Qualification of the volume variable | Conclusion of the study |
---|---|---|---|---|---|---|
The databases used were sorted into six categories, as recommended by Levac et al. [26]: electronic health records, administrative data, claims data, patient or disease registers, health surveys, or clinical trials data | The use (or not) of International Classification of Diseases (ICD) [30] to classify the diseases studied was recorded. | The scales or scores used to stratify analyses for the initial severity of the patient’s condition were classified as a known score (e.g. the Charlson Comorbidity Index (CCI), as adapted by Deyo [32, 33], or the Elixhauser score [34]) or another scale/score. All the covariates used to adjust the statistical models were listed and then sorted using an inductive approach. | The types of graphic representation of the results were classified as graphs, tables, or both. Graphs were subdivided into scatter plots, line graphs, bar graphs, histograms, pie charts, box plots or other graphs, as described by Slutsky et al. [28] | The variable used to assess hospital volume was classified as continuous, categorical, or both. If volume was considered as a categorical variable, we extracted more detailed information on the categories: quantiles, statistically defined cut-off points, arbitrary thresholds or those based on the literature, and other types. | Lastly, each study conclusion was noted and classified as having found (or not) a statistically significant positive (or negative) relationship between volume and outcome. |
Results
Description of the publications included
Data sources
The surgical disciplines and procedures investigated
Outcomes and hospital volume
Mortality | Length of stay | Hospital readmission | Cost | Surgical complications | General complications | Oncological issues | Characteristics of the hospital stay (continuous) | Quality indicators |
---|---|---|---|---|---|---|---|---|
Death occurring during a pre-defined time period (1, 7, 30, 60, 90 or 180 days, 1, 2, 3 or 5 years) | Continuous length of stay (from admission to discharge) | Readmission for any cause during a pre-defined time period (2 weeks, 30 days, 6 weeks, 90 days, or 1, 2, or 3 years) | Costs billed by the hospital, excluding physicians’ fees | Severity of the complication: Clavien-Dindo grade III or higher | At least one complication within a specific time period (in-hospital stay, 30 or 90 days, 75th percentile of the length of stay) or the complication rate | successful surgery: positive surgical margins (circumferential), number of resected lymph nodes, complete resection or not, restorative surgery performed or not. | Being in the intensive care unit (ICU) for longer than a specific time (1 or 2 days) or requiring organ support (mechanical ventilation or dialysis) | Patient safety indicators |
Failure-to-rescue rates: death after a major complication within a pre-defined period of time (30 days, 90-days, in-hospital) | Continuous post-surgical length of stay (from surgery to discharge) | Readmission for a specific cause (aseptic revision, rescue surgery as a full procedure after a partial one, implant revision) | Sum of all costs except the cost of initial surgery (considered to be similar across all centres) | Abscess, haemorrhage, or anastomotic leakage | Major complications, defined as the need for surgical intervention or organ supply within a specific time period (in-hospital, 14 days) | Recurrence of cancer: local recurrence, distant metastases, and vital status | Routine discharge versus nonroutine discharge (i.e. to rehabilitation, home, or a care home) | Surgical reconstruction rate |
Ratio between observed and expected (O/E) deaths | Continuous length of uninterrupted institutional care | A composite of readmission to an acute care hospital for any cause and all-cause death within a specific time period | Excess costs, defined as those above a defined cut-off (median, 75th percentile, etc.) | Surgical site bleeding, need for transfusion, or transfusion volume | Kidney failure or urinary tract infection | Risk ratios for positive margins | Time to surgery/transplantation or the door-to-balloon time | Proportion of pneumectomies |
Risk-adjusted mortality: the O/E ratio multiplied by the overall mortality rate for the cohort | Prolonged length of stay: longer than a cut-off (insurance period, median value, 75th percentile, 90th percentile, etc.) | Risk-adjusted readmission rate, the O/E ratio multiplied by the overall readmission rate for the cohort | Cost per day of treatment: the total cost divided by the length of stay | Perforation or laceration (bowel, oesophageal, ureteral, rectum, bladder, nerve, etc.) | One of the eight emergency general surgery complications | Time to recurrence or progression-free survival time | Duration of treatment with antibiotics | Amputation-free survival |
Hospital-standardized mortality ratio | Unplanned readmission to the same hospital | Cost-per-episode of surgery, adjusted for wage index | Surgical site infection, wound infection | Sepsis, septicaemia, shock, or prosthesis or implant infection | Travel time or distance to hospital | Sphincter preservation | ||
Disease-related death (cancer, surgery, or sepsis related) | Readmission rate for each subspecialty or diagnosis | Cost-per-episode of surgery, adjusted for inflation | Major amputation (lower limb, organ) | Pulmonary embolism, deep venous thrombosis | Number of hours requiring organ support | Survival of thumb replantation | ||
Time-to-death, as the time interval between surgery and death | Reoperation during the initial hospital stay | Neurological or cerebrovascular complications | Duration of surgery | |||||
Post-discharge mortality | Need for a permanent pacemaker | Duration of anaesthesia | ||||||
In-hospital mortality | Respiratory failure or arrest | |||||||
Cardiac arrest or myocardial infarction |
Covariates included in the model, and assessment of the initial severity
Patient characteristics | Hospital characteristics | Clinical conditions | Severity | Details of the disease | Details of the surgery | Details of the hospital stay | Post-operative events |
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Age (patient, donor, recipient, gestational age) | Hospital size (number of beds) | Laboratory results (albumin, anaemia, hyperlipidaemia, natremia, and creatinine) | The All Patient Refined Diagnosis Related Group score | Time to treatment (door-to-balloon time, waiting time, etc.) | Type of procedure and approach (laparoscopic, open, percutaneous, minimally invasive, etc.) | Admission source (nursing facility, home, transfer within hospital, or ambulance) | Adverse effects |
Substance abuse/consumption (alcohol, illicit drugs, tobacco, etc.) | Hospital ownership or type (private or public sector) | Signs of shock on admission (heart rate, hypotension, Glasgow Coma Scale, Japan Coma Scale, hemodynamic instability, ECG) | The Charlson-Comorbidity Index [32] | Tumour characteristics (site, shape, size, stage, grade, differentiation status, histological subgroup, clinical-TNM, pre-therapeutic-TNM, extent, metastasis, distance from critical organs) | Concomitant procedures (additional resections, lymphadenectomy, and valve surgery) | Distance (from home, from previous facility, to the closest high-volume hospital, total distance travelled, etc.) | Resection status (complete resection of positive margins) |
Sex or gender | Hospital teaching status or level (trauma centre, centre of excellence, reference centre, etc.) | Heart disease (atrial fibrillation, LVEF trend, NYHA class [33]) | The Elixhauser score [34] | Injury severity and mechanism, trauma site | Details of anaesthesia (substance used, duration, and local or general) | Cost (total or out-of-pocket) | Complications |
Language | Hospital location (urban, rural, city, state, country, region) | Lung disease (chronic obstructive pulmonary disease, asthma, chronic lung conditions) | The American Society of Anesthesiologists score (ASA) [35] | Multiple and/or synchronous tumours | Treatment modality (resection, laser, stenting, bariatric procedure, etc.) | Admission status (scheduled or emergency) | Post-operative radiotherapy or chemotherapy |
Body mass index (or birthweight or obesity) or body surface area | Number of licensed practical nurses per occupied bed | Liver disease (cirrhosis or failure) | Self-reported comorbidities | Aneurysm characteristics (diameter and rupture) | Risk Adjustment for Congenital Heart Surgery [36] | Discharge type (transfer, recovery unit, nursing home, etc.) | |
Geographic information (city, state, country, zip code, population, density) | Number of registered nurses per occupied bed | Renal disease (chronic or acute renal failure, creatinine, or dialysis) | The modified Kellgren-Lawrence score [37] | Specific scores: International Federation of Gynecology & Obstetrics [38], Furhman [39], Injury Severity Score [40], Kidney Donor Risk Index [41]) | Surgical indication | Length of uninterrupted institutional care (LUIC) | |
Economic status or income (self-reported, zip-code-based, quartiles) | Chronic diseases (diabetes and depression) | The Score for Neonatal Acute Physiology [42] | Lymph node status and lymphadenectomy | Surgeon’s specialty | Period of admission (the year and/or month, on a weekday vs. the weekend) | ||
Educational level (self-reported, parents’ level, zip-code-based) | Pre-operative medical treatment (neo-adjuvant chemotherapy or radiotherapy, immunosuppressive therapy, aspirin, beta blocker, biopsies, statins) | Pre-operative patient-reported outcome measures | Benign or malignant tumours | Time interval between diagnosis and surgery | Total length of stay | ||
Social security status (or primary payer) | Previous surgery (coronary surgery, aortic surgery, total hip/knee replacement, or carotid revascularization) | Diagnosis and/or aetiology | Intraoperative blood volume loss and/or transfusion requirement | Specific length of stay (LUIC, ICU, pre-surgery unit) | |||
Race or ethnicity | Previous or active cancer | Date of diagnosis | Oncological issues (concomitant examination and result, microscopic or macroscopic negative margins) | Ambulatory status | |||
Family history of disease | Number of diagnoses | ICU stay | |||||
Primary tumour site |