Table 2. Study characteristics.

Reference	Study methodology	Setting	Outcomes/Endpoints	Results	Limitations
Conley et al., 2011 (12)	Qualitative – interview – post-implementational, conducted during 4 months	USA. 5 State hospitals (different sizes & forms of implementation). 60–90 min interviews with 5 implementation leaders + 1 surgeon, 30–45 min interviews with surgeons.	Factors for effective SSC implementation	Explain why (education) and adaptively show how (training) to use the checklist led to buy-in among surgical staff and sustained checklist use	Phone interviews. Small number of interview partners. Different stages of checklist implementation
Haynes et al., 2011 (13)	Quantitative – survey – pre-/post-interventional, data collection during 2 weeks each pre- and post-implementational	Canada, India, Jordan, New Zealand, Philippines, Tanzania, England, USA. 8 hospitals. Different surgical specialties. 538 questionnaires from 7 hospitals (281 before & 257 after implementation)	SSC’s effect on postoperative outcomes. OR staff’s attitudes & perceptions towards SSC	Mean SAQ score increased from 3.91 to 4.01. Perception of teamwork and safety climate improved post-implementational and were associated with enhanced postoperative outcomes	Voluntary participation. Hospital sample may not be representative. Staff’s knowledge about an on-going quality improvement project could lead to bias. Only 10% of SAQ was used
Takala et al., 2011 (14)	Quantitative – survey – pre-/post-interventional, data collection during 4–6 weeks each pre- and post-implementational with an implementation time in between of 2–4 weeks	Finland. 4 university & teaching hospitals. Different surgical specialties. 1,748 questionnaires (901 before & 847 after implementation)	SSC’s effect on safety-related issues & communication	Awareness of patient-safety related issues, the procedure and its risk got increased by the checklist. Team communication improved and communication failures decreased post-implementational	Prospectively collected data. Use of checklist could not have been blinded. Heterogeneity of participating units might be a weakness or strength
Böhmer et al., 2012 (15)	Quantitative – survey – pre-/ 3 months post-interventional	Germany. 1 university hospital. Traumatology & Orthopedics. 71 questionnaires	SSC’s effect on perioperative safety standards & interprofessional cooperation	Checklist implementation leads to changed staff attitude with increased awareness of patient-safety relevant factors and improved rating for interprofessional cooperation	None written
Fourcade et al., 2012 (16)	Mixed methods – interview, observation, survey – post-implementational	France. 18 cancer centers. Surgical procedures performed under general or loco-regional anesthesia. Collective interviews with 16 staff members, individual interviews with 8 key surgical staff members. Email questionnaire from 1 person per center (OR staff or quality department staff). 20 hours of direct observations	SSC’s compliance/completeness rates, identify barriers & develop a strategy for effective SSC use	Mean compliance rate was 90.2%, mean completeness rate was 61%. The main barriers were duplication of items with existing processes, lack of communication between surgeon & anesthetist, time management, lack of timing and understanding of items, ambiguity and risks not covered by the checklist	Hawthorne effect. Overestimation of the use of checklists due to the mandatory use of it. Staff members participating in the collective interviews were also involved in the evaluation. Interventional radiology and local anesthesia were excluded
Delgado Hurtado et al., 2012 (17)	Quantitative – survey – post-implementational, 1 year after implementation	Guatemala. 3 hospitals (2 public teaching hospitals, 1 private). 147 questionnaires	OR staff’s knowledge & acceptance of the SSC	93.8% of the respondents were aware of the existence of the checklist, 88.8% knowing its content. Majority of staff members accepted the SSC and its implementation	The differences on the number of participants in the subgroups. Self-reported nature of the questionnaire
Levy et al., 2012 (18)	Quantitative – observation, survey – post-implementational, data collection of observations during 7 weeks	USA. 1 teaching pediatric hospital. Different pediatric surgical specialties. Only elective operations. 29 questionnaires, observation of 142 operations	SSC adherence, OR atmosphere, OR staff’s attitude, perception & understanding of the SSC	Despite a documented compliance rate of 100% in hospital data, adherence was significantly less with an average number of 4/13 checklist items checked. Significant differences in survey results were seen in the content, responsible person, and presence of staff members during checklist implementation, indicating a lack of understanding and timing of the checklist	Hawthorne effect. Lack of outcome measures correlating with checklist adherence, no conclusions can be drawn about the impact of checklist adherence. The checklist is made for adults, not pediatrics
Böhmer et al., 2013 (19)	Quantitative – survey – pre-/post-interventional, data collection before implementation and after 3, 18 and 24 months	Germany. 1 university hospital. Traumatology & Orthopedics, Anesthesiology & Intensive Care Medicine. 99 questionnaires	SSC’s effect on perioperative safety standards & interprofessional cooperation	Some aspects of patient-safety relevant information were rated more positively even 2 years after implementation. Teamwork and communication did not improve in a long-term, except from surgeon’s point of view	Self-reported nature of the questionnaire. The questionnaire was not validated
Haugen et al., 2013 (20)	Quantitative – survey – pre-/post-interventional, data collection during 4 weeks each pre- and post-implementational,	Norway. 1 tertiary university hospital. Different surgical specialties, Anesthesiology & Intensive Care Medicine. Elective and emergency operations. 641 questionnaires (349 before & 292 after implementation)	SSC’s effect on safety culture perceptions, SSC compliance	The checklist intervention group showed significant improvements on several baseline culture factors compared to the control group. Post-implementational, the intervention group showed only a significant improvement on 2/12 factors of patient safety culture factors	No statement on checklist adherence. The low response rate might be a limitation for sample representativeness. Differences in professional backgrounds between responders and non-responders
Pickering et al., 2013 (21)	Quantitative – observation – post-implementational, data collection during 21 months	United Kingdom. 5 hospitals (1 district general hospital, 3 teaching hospitals, 1 tertiary referral center). Different surgical specialties. Elective & emergency operations. Observation of 294 operations	Quality of SSC performance	While time-out was performed in 87.4%, sign-out was only conducted in 8.8%. In time-outs, all items were checked in 54.9%, the whole team present in 77.4% and active participation was observed in 72.8%. There were no significant differences between surgical specialties, but between hospital sites	Hawthorne effect. Limited spread of hospitals & specialties involved. Degree of subjectivity in observations. Small sample of hospitals may not be representative
Cullati et al., 2014 (22)	Quantitative – survey – data collection during 1 day	Switzerland. Participants of the joint meeting of the Swiss Society of Surgery and the Swiss Society of Anesthesia and Reanimation. 152 questionnaires	SSC implementation, perceived compliance & personal opinions towards it	67.7% of respondents reported having a checklist in their hospital. While 8/10 respondents answered they would apply the sign-in and time-out very often/always, only 5/10 respondents acknowledged the sign-out was performed never/rarely. Most respondents agreed that the SSC improves intraoperative safety and team communication. Fewer respondents agreed that the SSC enhances teamwork and reduces social hierarchy	Low participation rate. Self-reported & voluntary nature of the questionnaire
Russ et al., 2015 (23)	Quantitative – observation – post-implementational, data collection during 21 months	England. 5 hospitals (different health regions, larger teaching & smaller community hospitals). Different surgical specialties. Elective & emergency procedures. Observation of 565 time-out & 309 sign-out sessions	Usage & quality of SSC performance	Average adherence to checklist items was 2/3, in 40% of the cases team members were absent and in 70% they failed to pause or focus on checks. Information sharing improved across the OR team. Sign-out was not completed in 39% of cases, mostly because of lack of knowledge when to perform it. There was large variation in checklist use between hospital sites, but not between surgical specialties and between elective and emergency procedures. When a surgeon led the SSC and when all team members were present and paused, quality of SSC performance was improved	Hawthorne effect. Sign-in part is missing. Only certain surgical specialties were observed. Observations may be biased because of cultural factors and results cannot be generalized. No long-term data
Russ et al., 2015 (24)	Qualitative – interview – post-implementational, data collection during 1 year	England. 10 hospitals (different geographic regions & sizes, teaching & community hospitals, different incident reporting levels, different stages of checklist implementation). 119 interviews	SSC implementation and its barriers & facilitators	Some barriers mentioned in the interviews were related to the checklist itself, such as its design, or overlap with existing processes. The most common barrier was resistance from senior clinicians. Facilitators mentioned modifying the checklist, providing education/training, providing feedback on local data, fostering strong leadership, and establishing accountability	Small sample of hospitals may not be representative. Voluntary nature of the questionnaire. Long data collection period. The opinion of the management staff was neglected
Molina et al., 2016 (25)	Quantitative – survey – pre-/post-interventional, data collection before implementation and 1–2 years after baseline survey	USA. 13 hospitals. 1,744 questionnaires (929 before & 815 after implementation)	SSC’s effect on OR staff perceptions & perioperative safety	54.1% of respondents answered their team would always use the SSC effectively. 73.6% indicated it would prevent problems or complications. The implementation of the SSC was associated with improvements in OR staff’s perception of teamwork, communication, coordination between surgeons and anesthesia, effective leadership, the ability to be assertive when necessary to improve safety and mutual respect	No data about change over time. No statement possible about consequences on patient outcome. Non-response bias was neglected. Only inpatient hospitals in South Carolina. Only hospitals that completed the post-implementation questionnaire. Only 54.1% of respondents reported using the SSC effectively; question if changes in perception is really from SSC implementation
Santana et al., 2016 (26)	Quantitative – survey – pre-/post-implementational, data collection was conducted 2 weeks before the pre-intervention period and 2 weeks after the post-intervention period	Brazil. 3 public hospitals (different sizes). Different surgical specialties. 472 questionnaires (257 before & 215 after implementation)	OR staff’s attitudes & opinions towards surgical safety	A statistically significant improvement of the perception of safety and teamwork from nursing staff and anesthesiologists was observed after SSC implementation. Concerns about patient safety and compliance with standards and rules improved post-implementational, especially from nursing staff. The majority of staff considered the checklist easy and quick to use, felt that it improved communication, contributed to the development of a surgical safety culture and helped prevent errors. There was only little improvement in surgeon attitudes	Small sample of hospitals. Results may not be representative due to the differences of staff/hospitals/patients. Prospective design. Changes in politic may increase awareness of patient-safety independently from SSC implementation
Korkiakangas, 2017 (27)	Qualitative – observation – post-implementational, data collection during 6 months	England. Teaching hospital. Different surgical specialties. Only elective surgery. Observation of 20 operations	Identifying communication mechanisms influencing team mobilizing for the SCC execution	Key aspects of team mobilization for the SSC, which influenced each other were the timing, the distribution of staff in the OR and the instigation practices used. An appropriate timing seemed when most staff members were present, poor timing when staff were scattered through in the OR or busy with other tasks. Participation improved with instigation practices, such as a loud inclusive call informing everyone that the time-out was about to begin	Small sample sizes may not be representative. Not about completing the entire checklist
Sokhanvar et al., 2018 (28)	Quantitative – survey – data collection during 8 months	Iran. 8 tertiary general hospitals. 145 questionnaires	OR staff’s attitude, awareness & knowledge of the SSC and its acceptance	92% of the respondents were aware of the existence of the SSC and 73.9% knew its content. 60% strongly agreed that the SSC improved patient safety and more than 90% answered that it enhanced teamwork. Acceptance of the checklist was high among all professions, lowest among surgeons. Lack of time and training were the main barriers. Surgeons were more sensitive to these barriers. Training courses were mentioned as facilitating checklist implementation	Participation was voluntary. Locally adapted version of SSC. Self-reported questionnaire. Differences in numbers of subgroups
White et al., 2018 (29)	Mixed methods – survey, observation, focus groups – 12–18 months post-implementational, data collection during 4 weeks	Madagascar. 14 hospitals (different sizes and different performances of checklist utilization). 149 questionnaires. 1 focus group per hospital. Observation of 1–3 operations/simulations per hospital	Usage of the SSC and its impact, safety attitude, team behavior, implementation barriers	Sustained checklist use got reported by 74% after 15 months. The majority of respondents reported improved understanding of patient safety, which was associated with sustained checklist use, and job satisfaction. Implementation of the SSC showed improvements in hospital culture and hospital practice. Main barriers to effective checklist implementation were lack of time in an emergency and obstructive leadership	Self-reported questionnaire. Small sample size of observations. Sometimes observation of simulations. Focus groups were not recorded and thus evaluation could be more subjective. Social pressure in focus groups due to hierarchical authority culture. Follow-up rate was only 37%. Only 2/3 of original hospital sites were visited
Schwendimann et al., 2019 (30)	Mixed methods – interview, observation – post-implementational, data collection during 5 months	Switzerland. 1 university hospital. Observation of 72 time-outs & 32 sign-outs. 11 interviews	Barriers & facilitators of SSC application, quality of usage	Time-outs were performed in 96–100% of cases, sign-outs only in 22%. The poor performance rate of the sign-outs was mainly due to the absence of key staff members. Facilitators for effective checklist usage were well-informed specialists who supported the SSC, as well as teams focused on checklist performance and its content. Barriers were staff insecurity, a negative attitude towards the SSC, lack of teamwork and hesitation to complete the checklist	Sample bias may not be representative. Hawthorne effect

SSC, Safe Surgery Checklist; SAQ, Self-Assessment Questionnaire; OR, operating room.