Introduction: Despite increased focus on patient safety, complication rates in hospitals have remained unchanged with reports ranging between one out of twenty patients and one out of four patients, often related to surgery. However, half of the complications may be prevented throughout the surgical pathway. To inform and study effects of targeted patient safety interventions requires patient outcome data of high accuracy. Introduction of the World Health Organization surgical safety checklists (WHO SSC) has been reported to increase safety, also in our hospital. Aims: The overall objective for the study was to investigate effects of using safety checklists on patient outcomes in medicine. Further, to evaluate effects of adding a validated Norwegian version of the pre- and postoperative parts of the SURPASS checklists in combination with the established WHO SSC on emergency reoperations, 30-day unplanned readmissions, 30-day mortality and length of hospital stay, in addition to verified in-hospital complications using a reliable and validated method. Methods: In the first study, we conducted a systematic literature search in Cochrane Library, MEDLINE, EMBASE and Web of Science on effects on patient outcomes of using safety checklists in medicine. Following the PRISMA guidelines ensured transparency of reporting. The studies were eligible if they quantitatively reported possible effects of using safety checklists. In the second study, validation of a Norwegian version of the pre- and postoperative SURPASS checklists in combination with the established WHO SSC was performed in one neurosurgical department. Adaptation and validation of the new checklists were in accordance to guidelines from the WHO included forth- and back translation, testing the content in clinical practice, focus groups, expert panels, and final approval of the checklists. The third study used a prospective observational design to investigate complications in surgical admissions using two different methods. Utilising the Global Trigger Tool (GTT) and the International Classification of Diseases 10th version (ICD-10) identified and verified in-hospital complications in the same admissions with GTT appointed as the reference standard. Tests were performed to investigate strength of method agreement of estimating complications. In the fourth study, the validated pre- and postoperative SURPASS checklists were implemented as an add-on to the established WHO SSC using a Stepped Wedge Cluster Controlled Trial (SWCCT) design in three surgical clusters, each serving as their own controls (neurosurgery, orthopaedics and gynaecology) in one hospital. One separate department in the intervention hospital and two external hospitals without new checklists constituted parallel controls. Effects on verified in-hospital complications, emergency reoperations, 30-day readmissions, 30-day mortality and length of hospital stay were investigated over 29 months from November 2012 through March 2015. Results: Thirty-four studies met the inclusion criteria of the systematic review of the literature showing improvements in four groups of patient outcomes: morbidity and mortality; adherence to guidelines; human factors; and adverse events. None of the included studies reported on checklist use resulting in decreased patient safety (Study I). Translation of the pre- and postoperative SURPASS checklists in combination with the WHO SSC was completed and reached face validity. Testing of the content was performed for 29 neurosurgical procedures with all checklist users (ward nurse and physicians, surgeons, anaesthesiologists, operating theatre nurses, post-anaesthetic care unit nurses, and discharging physicians and nurses). Focus groups revealed that wording needed to be adapted to clinical practice and that checklist items challenged existing workflow. The expert panels scored content validity to > 80 %. All the steps involved adjustments to the checklist content. The final back translated SURPASS checklist version was approved by the Dutch copyright holder (Study II). In 700 random surgical admissions complications were identified in 30.3 % (298/700) using the GTT method. Extracted ICD-10 codes indicating a complication yielded a rate of 47.4 % (332/700) in the same admissions. However, when excluding ICD-10 codes representing conditions present on admission, in-hospital complications were verified for 20.1 % (141/700) of the admissions. After the verification procedure, agreement of complications between findings using both methods increased from 68.3 % to 83.3 % (Study III). The fourth study compared 3,892 before and 5,117 procedures after the pre- and postoperative SURPASS checklists implementation in intervention clusters. In addition, investigations of 9,678 surgical procedures in parallel control hospitals were performed. Crude analysis of in-hospital complications showed an increase of complications from 14.7 % to 16.5 % (p=0.025). However, in-hospital complications decreased in adjusted intention to treat analyses (Odds Ratio (OR): 0.73; 95% Confidence Interval (CI): 0.54 to 0.98; p = 0.035). Logistic regression on effects of the SURPASS checklists, show a significant decrease in in-hospital complications (OR: 0.70; 95% CI: 0.50 to 0.98; p = 0.036) and emergency reoperations (OR: 0.42; 95% CI: 0.23 to 0.76; p = 0.004) with full compliance to the preoperative SURPASS checklist in adjusted analysis. With obtained full compliance to the postoperative SURPASS checklists 30-day readmissions were decreased (OR: 0.32; 95% CI: 0.16 to 0.64; p = 0.001) in adjusted analysis. Thirty-day mortality and length of hospital stay remained unchanged. For parallel control hospitals, the in-hospital complications increased, whereas emergency reoperations, 30-day readmissions and 30-day mortality were unchanged. Conclusions The systematic review of the literature concluded that use of safety checklists may have positive impact on patient outcomes as more clinicians adhere to standardised guidelines and procedures; improve human factors; and reduce adverse events, morbidity and mortality. We need more studies with strong study designs investigating effects of checklists used throughout the surgical pathway. The first Norwegian version of the pre- and postoperative SURPASS checklists in combination with the already established WHO SSC was validated following guidelines on translation and adaptation from the WHO. Using ICD-10 codes to monitor complications increased accuracy significantly when codes indicating complications were verified to have emerged in-hospital. Full compliance with the pre- and postoperative SURPASS checklists were associated with reduced in-hospital complications, emergency reoperations and 30-day readmissions when added to the already established intraoperative WHO SSC
