Implementation of Surgical Safety Checklists and Postoperative Complication Rates

Introduction

Surgical care remains a substantial contributor to preventable patient harm worldwide, with postoperative complications affecting a clinically significant proportion of patients undergoing inpatient surgical procedures and contributing to prolonged hospitalization, increased healthcare expenditure, and, in severe cases, permanent disability or death. Analyses of adverse surgical events have consistently found that a substantial proportion of complications are attributable not to technical surgical error, but to systems-level failures, including inadequate communication among the surgical team, omitted prophylactic measures such as antibiotic administration or venous thromboembolism prophylaxis, and failures in verification processes intended to prevent wrong-site or wrong-patient surgery (Gawande, 2010; de Vries et al., 2020).

In response to this evidence, the World Health Organization introduced the Surgical Safety Checklist in 2008 as a structured, three-phase intervention designed to standardize critical safety verifications at defined points during the surgical episode: prior to induction of anesthesia (Sign In), prior to skin incision (Time Out), and prior to the patient leaving the operating room (Sign Out). The checklist was designed not merely as a documentation tool, but as a structured communication process intended to promote active verbal confirmation among surgical team members and to surface potential safety concerns before they could result in harm. The original multi-center study evaluating checklist implementation reported substantial reductions in both postoperative complication and mortality rates across a diverse set of international hospital sites (Haynes et al., 2019), establishing the checklist as a cornerstone of contemporary perioperative safety practice.

Subsequent replication studies, however, have produced more heterogeneous findings, with some large-scale evaluations reporting minimal or no measurable effect of checklist implementation on complication rates (Urbach et al., 2018). This inconsistency in the replication literature has prompted increased scrutiny of implementation fidelity as a potential explanatory factor, with several studies suggesting that the safety benefit of the checklist is contingent not on its mere presence in the operating room, but on the degree to which it is used as intended, namely through genuine verbal engagement and active team communication rather than passive or perfunctory completion (Russ et al., 2015; Bergs et al., 2019). Despite this growing recognition of the importance of fidelity, relatively few studies have directly measured checklist use fidelity alongside postoperative outcomes within the same patient population, limiting the ability to disentangle the effect of checklist implementation itself from the effect of how faithfully it is executed in practice.

Given the mixed replication evidence and the theoretical importance of implementation fidelity, further research directly examining both checklist implementation and observed fidelity of use, in relation to objectively measured postoperative complication outcomes, is warranted. The purpose of this study was to examine the association between surgical safety checklist implementation and 30-day postoperative complication rates among adult surgical patients, and to specifically evaluate whether the degree of checklist use fidelity modified the magnitude of this association.

Methods

This study employed a prospective, pre-post observational design conducted across three surgical services, general surgery, orthopedic surgery, and gynecologic surgery, at a single 400-bed acute care hospital. Data collection occurred over a continuous 14-month period, consisting of a 6-month pre-implementation baseline period during which surgical teams followed existing, unstandardized perioperative verification practices, followed by a 2-month training and rollout period, and an 8-month post-implementation period during which a modified WHO Surgical Safety Checklist was used for all included cases. Adult patients aged 18 years or older undergoing an inpatient surgical procedure on one of the three participating services were eligible for inclusion. Emergency cases requiring immediate surgical intervention without opportunity for standard preoperative preparation were excluded, as were cases with incomplete 30-day outcome data. A total of 1,842 surgical cases were included: 912 during the baseline period and 930 during the post-implementation period.

The modified WHO Surgical Safety Checklist implemented during the intervention period retained the three standard phases of the original WHO instrument, adapted with institution-specific verification items relevant to the participating surgical services, including implant availability confirmation for orthopedic cases and specimen labeling verification for general and gynecologic surgical cases. All operating room staff, including surgeons, anesthesia providers, and circulating and scrub nurses, completed a structured training session prior to rollout, emphasizing the checklist’s function as an active communication process requiring genuine verbal participation from all team members rather than a passive documentation requirement.

Checklist use fidelity was directly observed for a stratified random sample of post-implementation cases by trained research observers who were not members of the operating room team, using a validated fidelity assessment tool addressing three domains:

1.Completeness, defined as whether all required items within each of the three checklist phases (Sign In, Time Out, Sign Out) were addressed, regardless of the manner in which they were addressed.

2.Verbal engagement, defined as whether checklist items were confirmed through active verbal exchange involving multiple team members, as opposed to being completed silently or confirmed by a single individual without team input.

3.Team attentiveness, defined as whether team members paused other activity to attend to the checklist process, as opposed to continuing unrelated tasks during checklist administration.

Cases were classified as high-fidelity if they achieved complete, verbally engaged completion across all three checklist phases, and low-fidelity if any phase was incomplete, silently completed, or conducted without adequate team attentiveness. The primary outcome was the occurrence of a postoperative complication within 30 days of surgery, identified through the hospital’s surgical quality registry and supplemented by structured chart review, and classified using the Clavien-Dindo classification system to capture complication severity. Multivariate logistic regression was used to compare complication rates between the pre- and post-implementation periods, and separately between high-fidelity and low-fidelity checklist use within the post-implementation cohort, adjusting for patient age, American Society of Anesthesiologists (ASA) physical status classification, surgical service, and procedure duration. Statistical significance was set at p < .05, and analyses were conducted using Stata version 18.

Results

Patient and procedural characteristics, including age, ASA classification, and distribution across surgical services, did not differ significantly between the pre-implementation and post-implementation cohorts (all p > .05), supporting comparability between periods. Checklist use fidelity was directly observed for 246 post-implementation cases, of which 58.5% (n = 144) met criteria for high-fidelity use and 41.5% (n = 102) were classified as low-fidelity.

The overall 30-day postoperative complication rate declined significantly following checklist implementation, from 12.4% (113/912) during the baseline period to 8.1% (75/930) during the post-implementation period (adjusted odds ratio = 0.62, 95% CI 0.46–0.85, p = .003), after adjusting for age, ASA classification, surgical service, and procedure duration. When post-implementation cases were stratified by observed checklist fidelity, a substantially larger safety benefit was evident among high-fidelity cases: the complication rate was 6.3% among high-fidelity cases compared to 10.9% among low-fidelity cases (adjusted odds ratio = 0.54, 95% CI 0.40–0.73, p < .001).

Analysis by complication type revealed that the largest absolute reductions following checklist implementation occurred in surgical site infection, which declined from 5.1% to 2.9% of cases, and unplanned return to the operating room, which declined from 2.8% to 1.4% of cases. Reductions in venous thromboembolism and postoperative pneumonia were more modest, though the direction of effect remained consistent with an overall safety benefit. Among the observed cases, deficiencies in verbal engagement were the most common fidelity failure, occurring in 68% of cases classified as low-fidelity, more frequently than incomplete item coverage or inadequate team attentiveness. Cases with documented verbal antibiotic timing confirmation during the Sign In phase and explicit verbal confirmation of surgical site marking during the Time Out phase showed the strongest individual association with reduced surgical site infection and reduced return-to-operating-room rates, respectively.

Discussion

The findings of this study demonstrate a significant reduction in 30-day postoperative complication rates following implementation of a structured surgical safety checklist, consistent in direction with the original multi-center evaluation of the WHO Surgical Safety Checklist (Haynes et al., 2019). More notably, this study extends the existing evidence base by directly demonstrating that the magnitude of safety benefit was substantially larger among cases with high-fidelity checklist use compared to those with low-fidelity or incomplete use, providing empirical support for the hypothesis that checklist effectiveness is contingent on the manner of its execution rather than its mere presence in the operating room (Russ et al., 2015; Bergs et al., 2019).

This fidelity-dependent pattern offers a plausible explanation for the heterogeneity observed across the broader checklist replication literature, including studies reporting minimal measurable effect of checklist implementation on complication rates (Urbach et al., 2018). If, as this study’s findings suggest, the checklist’s safety benefit derives substantially from active verbal team communication rather than passive item completion, then studies evaluating checklist implementation without accounting for fidelity of use may systematically underestimate the intervention’s true effect where fidelity is poor, while overestimating it where documentation-only completion is mistaken for genuine use. This distinction carries direct implications for hospitals seeking to implement or re-invigorate checklist programs: administrative mandates requiring checklist documentation, without corresponding attention to the quality and manner of team engagement during checklist administration, may fail to produce the anticipated safety benefit.

The specific pattern of complication reduction observed in this study, with the largest gains in surgical site infection and unplanned return to the operating room, aligns coherently with the checklist items most directly targeting these outcomes, namely verbal antibiotic timing confirmation and surgical site marking verification. This alignment strengthens confidence that the observed association reflects a genuine mechanistic effect of checklist-driven communication rather than a spurious association attributable to secular improvement in surgical outcomes over the study period. The finding that verbal engagement deficiency, rather than incomplete item coverage, was the predominant fidelity failure observed suggests that future implementation and training efforts should place particular emphasis on cultivating genuine team communication behavior, rather than focusing primarily on ensuring that checklist items are addressed in some form.

This study has several limitations. The pre-post design, without a concurrent control group, limits the ability to fully exclude secular trends in surgical outcomes unrelated to checklist implementation, though no other major perioperative quality initiatives were introduced on the participating services during the study period. Fidelity observation was conducted for a stratified sample rather than the full post-implementation cohort, which may limit precision in characterizing the fidelity-outcome relationship, and the presence of an observer during fidelity assessment may have modestly influenced team behavior toward more engaged checklist use than would occur unobserved. The single-site setting may also limit generalizability to hospitals with different surgical case mix, team composition, or existing safety culture. Future research employing multi-site designs with fidelity observation across the full surgical case volume, and examining the specific training and workflow interventions most effective at sustaining high-fidelity checklist use over time, would further strengthen the evidence base guiding perioperative safety practice. Taken together, these findings support continued implementation of structured surgical safety checklists, while emphasizing that sustained institutional attention to fidelity of use, not implementation alone, is necessary to realize the checklist’s full potential for reducing postoperative complications.

References

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