Bariatric surgery is an important specialty epidemiologically.1–8 As operating room (OR) capacity is scarce, ORs should be organized such that optimal patient care is combined with maximal efficiency of OR time. Efficiency can be improved by reducing overused OR time9 or by reducing allocated OR time. If procedures take less time by working more efficiently and if realized case durations are closer to planned durations, the long-term allocated OR time can be reduced.10 Furthermore, starting the first case of the day on time contributes to a better cost-efficient use of ORs.11 Every minute of reduction in tardy starts of first cases of the day results in a 1.1-minute reduction in scheduled labor costs.12
One possible option to improve efficient use of ORs is to work with OR teams that are dedicated to work together during the full OR day and to standardize the tasks of the operating team.13,14 We use the term “fixed team” to denote an OR team (surgeon, residents, nurses, and anesthesiologist) that remains the same for the full OR day. The advantage of working with a fixed team is that every team member knows the sequence of steps during surgery and is better able to think ahead. In a fixed team, the procedures are performed in a relatively stable atmosphere where surgeon and staff can concentrate better on the surgical process, because the various tasks are repeated several times during the day by the same staff. The OR is set up more quickly, because every member of the staff knows his or her task. When working together on several consecutive cases, instruments can be changed without explicitly mentioning each tool. In laparoscopic surgery, e.g., the efficiency can be increased considerably if the operator of the laparoscopic camera closely follows the surgeon’s instruments and knows when to fade in and out. These benefits of working in a fixed team improve the confidence of the surgeon and result in better performance.
After consulting their bariatric surgeons and anesthesiologists, OR management in the 2 hospitals under study decided for 2011 to schedule laparoscopic bariatric procedures together on the same day and to work with OR teams that remained fixed for the day. All team members shared the common explicit goal15 to work together on all scheduled cases of the day by optimizing safety (for patients and staff) and procedure duration. The effects of working with fixed OR teams were investigated by testing for improvements in (1) patient outcomes, (2) teamwork and safety climate, and (3) procedure durations.
Study Design and Participants
The study took place in 2 large teaching hospitals in the Netherlands: Catharina Hospital in Eindhoven (CHE) and St. Franciscus Hospital in Rotterdam (FHR). We obtained IRB approval from both hospitals to use their 2010 and 2011 bariatric data. In both hospitals, the following 5 types of laparoscopic bariatric surgeries were included: laparoscopic gastric bypass (LGB), laparoscopic sleeve gastrectomy (LSG), conversion adjustable gastric band (AGB) to LGB, conversion sleeve to LGB, and conversion vertical banded gastroplasty (VBG) to LGB. Some other types (removal AGB or VBG, conversion AGB or VBG to conversion sleeve) were excluded because of small sample sizes (in total 5.5% of all bariatric procedures).
The staff of OR teams consisted of surgeons, residents, OR nurses, and an anesthesiologist. The daily OR schedules were made by responsible staff members who had no part or interest in the study. They did not use any specific algorithm to determine the order in which the patients were operated on during the day, and their only task was to fill the assigned OR time maximally with procedures given the limitations in availability of specialized bariatric surgeons. During every bariatric procedure, an OR nurse specialized in bariatric procedures was attending in the role of scrub nurse or circulating nurse, and another nurse was added who was not specialized but competent and skilled for bariatric procedures. In 2010, the OR was planned conventionally on an individual staff basis, so that the composition of the OR staff changed per scheduled procedure. In 2011, the OR was planned with fixed teams, meaning that the complete OR team worked together in the same composition and in the same OR for all the procedures scheduled for the day. In the latter period, a laparoscopic bariatric OR day was scheduled depending on the availability of a specialized surgeon. The OR team was then completed by residents, OR nurses, and an anesthesiologist, and the staff composition was fixed for the day. The specialized OR nurse, the nonspecialized OR nurse, and the anesthesiologist were chosen randomly from the staff available for the day. The complete OR team was informed of the purposes of working with a fixed team, that is, to improve patient outcomes, teamwork and safety climate and to reduce procedure durations. The teams varied from one day to another, depending on the availability of staff. No effort was made to repeat the same staff composition for several days, because the OR planning would have become too complicated. In 2011, the surgeons involved in laparoscopic bariatric surgery in the 2 hospitals worked nearly exclusively with fixed teams except in emergency cases.
Both in 2010 and in 2011, the scheduling of patients for operations was based on their arrival to the hospital, on a first-come first-served basis. Criteria for patient eligibility for bariatric surgery included:16 age 18 to 65 years; weight >45 kg above the ideal body weight for sex and height; body mass index above 40 by itself or above 35 in case of an associated obesity illness such as diabetes or sleep apnea; obesity-related health problems; reasonable attempts at other weight loss techniques; no psychiatric or drug dependency problems; capacity to understand the risks and commitment associated with the surgery; and pregnancy not anticipated in the first 2 years after surgery. Criteria for exclusion from the study were emergency or urgent surgery, and trauma and critically ill patients. We refer to the data section below for the measured information on patient outcomes, teamwork and safety climate, and efficiency.
Three Research Hypotheses
Hypothesis 1: Fixed OR Teams Improve Patient Outcomes
Working in teams that remain fixed during the day may lead to more effective teamwork and to better adherence to clinical guidelines.17–19 Our hypothesis is therefore that patient outcomes will be better for the fixed OR teams in 2011 than for the changing OR teams in 2010.
Hypothesis 2: Fixed OR Teams Improve Teamwork and Safety Climate
A trained group in the OR may lead to enhancement of the patient safety culture and teamwork attitudes.17,20,21 Our hypothesis is therefore that staff working in fixed OR teams will report better teamwork than staff working in OR teams that change over the day.
Hypothesis 3: Fixed OR Teams Reduce Procedure Durations
Bariatric surgery with OR teams that remain fixed during the day may reduce procedure durations, both because of efficient work within fixed teams2 and because of team experience gained by performing the same procedure on several patients on the same day. Our hypothesis is therefore that procedure durations of bariatric procedures will be reduced by working with fixed OR teams and by performing the same procedure several times on the same day.
The data consisted of patient demographic and outcome data, staff data obtained from surveys on teamwork and safety climate, and intraoperative data. The number of included patients and procedures was 1387, with 422 observations for 2010 (292 in CHE, 130 in FHR) and 965 observations for 2011 (544 in CHE, 421 in FHR). Patient demographic data were available for gender, age, body weight, body mass index, and mortality. Patient factors did not differ significantly between the 2 periods, 2010 and 2011 (comparison-of-means t-tests had P values >0.05). We report values for 2010 and 2011 for CHE (and for FHR in parentheses). The percentage of male patients was 48% and 47% (43% and 46%), the median age of patients was 40 and 41 years (41 and 42 years), and the mean body mass index was 44.9 and 45.2 kg/m2 (43.7 and 44.1 kg/m2). Neither of the 2 hospitals had any mortality during 2010 and 2011. The patient outcome data consisted of the number of patients with complications, the number of complications per patient, the type of complication, the number of readmissions to the hospital, and the number of reoperations.
Staff data on teamwork and safety were obtained by using the Safety Attitudes Questionnaire (SAQ) that measures caregiver attitudes through 6 factor scales, that is, teamwork climate, job satisfaction, perceptions of management, safety climate, working conditions, and stress recognition.22,23 Each of the 41 items of the SAQ is scored on the 5-point Likert scale, and negatively worded items are scored reversely. The survey included questions such as “Nurse input is well received in this clinical area” and “I would feel safe here being treated as a patient.” Survey participation by OR staff (surgeons, residents, nurses, and anesthetists) was voluntary. To qualify for inclusion, the (full-time or part-time) staff member was required to have worked in the OR for at least 2 months after administration of the questionnaire. The staff survey was answered 2 times in 2011, first in January (at the start of the fixed-team period) and later in June. Of the fixed bariatric OR teams, 59 staff members participated in January (36 in CHE, corresponding to a response rate of 90%, and 23 in FHR, 79%) and 61 in June (35 in CHE, 88%, and 26 in FHR, 90%). Of the standard (nonbariatric) OR teams that changed during the day, 192 staff members participated in January (125 in CHE, 68%, and 67 in FHR, 66%) and 205 in June (134 in CHE, 72%, and 71 in FHR, 70%).
The intraoperative data consisted of procedure time and surgical time, type of laparoscopic bariatric surgery (LGB, LSG, or 1 of the 3 conversion types of procedures), and staff composition of the OR team. Procedure time is the total duration of stay of the patient in the OR, surgical time is the time from incision to closure of the wound, and peripheral time is the difference between procedure time and surgical time.24 For the fixed team period, additional information was available on the number and the sequencing of the procedures performed by the same fixed team on the same day and in the same OR.
Table 1 shows the sample sizes of the procedures that were included in the analysis along various dimensions: 2 periods (standard OR planning with changing OR teams during 2010 and planning with fixed OR teams during 2011); 2 hospitals; 5 surgeons who performed bariatric procedures in the 2 hospitals; and 5 types of bariatric procedures. The fixed-team period had 197 OR days, and every OR day counted a predetermined number of slots, i.e., number of procedures, that ranged between 2 and 8. The average number of procedures per day was 4.9. The data for “slot on day” in the table imply, e.g., that 68 (130–62) of the OR days had 5 procedures in total. The data for “same on day” count the number of times (including the current procedure) that the same procedure was performed before on the same day. For example, of the 965 procedures, 414 were performed for the first time during an OR day, and 4 procedures were performed for the eighth time (this occurred on 4 OR days with 8 slots and with the same procedure performed throughout the day). The mean number of same procedures within the same OR day was 2.2. To prevent small group sizes, some of the groups were combined with resulting sample sizes shown in the column “high” of Table 1. Such combinations were applied for the 3 conversion types of procedures, for slot numbers 5 and higher (with value truncated at 5, involving 80 truncations, 5.8% of all procedures), and for the fourth up to the eighth same procedure within the same day (with value truncated at 4, involving 75 truncations, 5.4% of all procedures).
For hypothesis 1 on patient outcomes, we used the Fisher’s exact test for 2-way contingency tables to test for differences in outcomes between the 2 groups, i.e., changing OR teams in 2010 and fixed OR teams in 2011.
For hypothesis 2 on teamwork and safety climate, we applied comparisonofmeans ttests to test for differences in means of the SAQ scores. We used Spearman’s Rho to test for correlation between the SAQ scores on teamwork and safety climate.
For hypothesis 3, the procedure durations (in minutes) were transformed by taking logarithms.25,26 The log-transformed data showed much less skewness than the original duration data (0.38 instead of 1.38) and hardly any excess kurtosis (−0.02 instead of 2.76). For our exploratory analysis we applied parametric comparison-of-means (t- or ANOVA) tests to test for differences in mean log-durations among various groups: 2 years; 2 hospitals; 5 surgeons; 5 types of bariatric procedures; 5 levels of the factor slot on day; 4 levels of the factor same on day (obtained after truncation for the fixed-team period, as described before). We also applied nonparametric Kruskal-Wallis tests for the comparison of mean rank scores, which do not depend on the logarithmic transformation. The standard deviations of the log-durations were compared between the 2 years and between the 2 hospitals by means of Levene’s F-test.
In addition to the above single-factor analysis methods, we also considered the joint estimation of the simultaneous effects of several factors on procedure durations. We used regression models for this purpose, with log-durations as the dependent variable and with (a selection of) the following explanatory factors: fixed team (dummy variable with value 0 for 2010 and value 1 for 2011); experience (surgeon-specific number of previous laparoscopic bariatric procedures performed since the start of 2010); squared experience (relevant if learning effects decrease over time); surgeon (4 dummy variables to account for differences among the 5 surgeons); procedure (2 dummy variables for the 3 considered types of procedures); slot on the day and same on the day (dummy variables, for respectively 5 and 4 levels). We included possible learning effects because procedure durations may improve with increased experience.27,28 As both hospitals worked with fixed teams in the last year of the considered 2-year period, we paid particular attention to disentangle the structural break of different OR planning since the start of 2011 from the experience effect that was built up gradually over both 2010 and 2011. The models allowed for different variances per hospital and per year, and the resulting regression equations with heteroskedastic error terms were estimated by weighted least squares (maximum likelihood). We also investigated the fixed-team and experience effects on surgical time and on peripheral time (the difference between procedure time and surgical time). The explanatory factors for surgical durations were identical to those for procedure durations. As surgeons were hardly involved in peripheral activities, the model for peripheral time contains a hospital dummy instead of surgeon dummies. As the teams changed from one day to another, the experience differed among team members, and we defined experience for peripheral activities in terms of the hospital-specific number of previous laparoscopic bariatric procedures that were performed since the start of 2010.
We also analyzed the fixed-team effect separately per surgeon and per procedure type, controlling for (squared) experience effects. In this case, we used the following test equation where “Time” is the procedure duration in minutes, “Exper” denotes the number of previous laparoscopic bariatric procedures performed by the surgeon since the start of 2010, and “Fixed” is a dummy variable with value 0 for 2010 (OR teams that change over the day) and with value 1 for 2011 (OR teams that remain the same over the full day).
log(Time) = α + β × Exper + γ × Exper2 + δ × Fixed + ε
Here α, β, γ, and δ are unknown model parameters, and ε denotes an unobserved error term that absorbs all random effects on log-durations. The square of experience was included to allow learning effects to be relatively larger when experience is still small (if β < 0 and γ > 0). Experience was measured by surgeon, as laparoscopic surgery is a highly specialized skill and also because the other team members varied in their experience. In the analysis below, the above model was sometimes extended by adding possible team learning effects within the day, in particular when the fixed team performed the same type of procedure on several patients on the same day. The above equation was estimated by ordinary least squares, and the effect of working with fixed OR teams was evaluated in terms of the estimated value of δ (and its t-value, 2-sided P value, and 99% confidence interval, which were all computed by standard regression formulas). If the coefficient of squared experience was not significant, the model was re-estimated without this term.
RESULTS AND DISCUSSION
Table 2 summarizes the patient outcomes in terms of the number and type of complications resulting from surgery, the number of readmissions to the hospital after surgery, and the number of reoperations. Most of the patient outcomes improved somewhat, in the sense that most of the observed incident risks were lower in 2011 than in 2010, but none of the differences was significant (at the 5% level). Our study did therefore not support the hypothesis of improved patient outcomes, although these outcomes likely did not worsen when working with fixed teams.
Teamwork and Safety Climate
Table 3 summarizes the scores that were obtained from surveys on teamwork and safety climate. We distinguish 8 groups, 4 for each hospital. In each hospital, 1 group worked solely in teams that changed during the day, and another group worked in fixed bariatric OR teams that remained the same during the day. Furthermore, 1 survey took place early in January 2011, at the start of bariatric surgery with fixed OR teams, and a second one was taken late in June 2011. The results in Table 3 show that the 2 hospitals generated largely similar responses on teamwork and safety in all 4 groups (standard and fixed team, in January and June). None of the 4 corresponding differences in mean scores between the 2 hospitals was significant (at 5% level). Table 3 therefore also presents the outcomes for the 2 hospitals combined. There was no significant correlation between the scores on teamwork and safety (Spearman’s Rho had P = 0.89).
The mean scores did not differ significantly for the following 3 groups of staff: standard team in January, fixed team in January, and standard team in June (teamwork, 3.14, 3.22, and 3.21, respectively; safety, 3.30, 3.41, and 3.36, respectively). The mean scores for fixed-team staff in June (teamwork, 4.08, safety, 4.16) were both significantly higher than in the other 3 groups, and the improvement of about 0.8 on a 5-point scale is quite substantial. These outcomes provide support for our hypothesis that teamwork and safety climate improved by working with OR teams that remained fixed for the day as compared to OR teams that changed over the day. In addition, some surgeons and nurses mentioned spontaneously during the study that they experienced a “team spirit” and a “smooth workflow.”
Another outcome of the staff surveys was that, in both the standard and fixed OR team groups, registered nurses scored significantly less positively (at 5% level) than surgeons did on the experienced teamwork and safety climate. Nurses reported more frequently the following complications: It was difficult to speak up; disagreements were not appropriately resolved; their input was not well received when decisions were needed; they did not receive appropriate feedback about their performance; culture made it hard to learn from the errors of others. Similar differences in perception between surgeons and nurses have been reported before.29 Differences between nurses and surgeons in status, authority, responsibilities, and experience are among the possible causes of these findings, but the surveys did not contain information on these variables.
Procedure Duration: Single Factor Effects
Table 4 provides comparisons of procedure times for various factors: 2 years (changing teams in 2010 and fixed teams in 2011); 2 hospitals (CHE and FHR); 5 surgeons; 3 types of bariatric procedures; and for 2011 also slot on day and same on day (both truncated as described before). For each of these factors, the mean and the mean rank score of procedure durations differed significantly among groups (P < 0.0001). In particular, bariatric procedures took on average 24% (99% CI, 19% to 29%) less time in 2011 than in 2010, and procedure times for fixed teams declined over the day and for procedures that were repeated within the same day. Furthermore, the variation of log-durations as measured by the SD differed significantly, both between the 2 years (P = 0.0006) and between the 2 hospitals (P = 0.0005).
Table 5 compares the log-durations for 2010 and 2011 for each of 15 combinations of surgeon and procedure type, and also after aggregation by surgeon and by procedure. In addition to the unadjusted comparisonofmeans ttest, we also compared the means after correcting for quadratic surgeon-specific experience effects, as described before. The reduction of durations over time was partly due to improved experience of the surgeons. After combining the outcomes for all surgeons and procedures, the estimated break effect of working with fixed OR teams since 2011 was reduced from 24.6% (99% CI, 21.3% to 27.9%) to 10.6% (99% CI, 4.9% to 16.3%), the difference being attributed to learning effects.
Procedure Duration: Multiple Factors
Table 6 shows the outcomes of 3 regressions involving the joint effects of all considered factors on log-durations. In the first regression, the experience effect was modeled separately for 2010 and 2011. The quadratic experience effects were not significant, and the resulting piecewise linear experience curve had a significant break between 2010 and 2011 (P value <0.0001).a The average experience effect per bariatric procedure was estimated as 0.19% (99% CI, 0.12% to 0.26%) in 2010 and 0.06% (99% CI, 0.01% to 0.11%) in 2011. The fixed-team effect was estimated as 12.9% (99% CI, 7.6% to 18.2%).
Instead of a sudden break in experience effects between 2010 and 2011, we considered it to be more natural to assume that the effects of experience declined gradually over time. Therefore, the second regression modeled the experience effect jointly for 2010 and 2011 by means of a quadratic relation, allowing for a level break between 2010 and 2011 because of the transition from working with changing OR teams in 2010 to working with fixed OR teams in 2011. The marginal experience effect declined gradually over time.b The fixed-team effect was now estimated as 10.8% (4.489–4.381 = 0.108, SE 0.022, P value <0.0001), with 99% CI, 5.0% to 15.3%. This value of 10.8% is close to the value of 10.6% obtained in Table 5 in case all surgeons and procedures were combined.
For the fixed-team period of 2011, we investigated the presence of withintheday team learning effects by means of the regression shown at the right side of Table 6. The slot number of a procedure, that is, its position in the sequence of procedures over the day, had no significant effect (at the 1% level, P = 0.03). Significant time gains were obtained by performing the same type of procedure several times within the same day, with an average gain per extra case of 5.1% (99% CI, 2.8% to 7.4%).
The above analysis for procedure durations was also performed for surgical durations (excluding peripheral activities in the OR) and for peripheral time (presurgical preparations and postsurgical patient care in the OR). For surgical time, the results were comparable to those presented before for procedure time. The experience effect was quite similar.c The fixed-team effect for surgical time was estimated as 12.3% (95% CI, 4.8% to 17.9%). The fixed-team effect for peripheral time was not significant (3.1%, P = 0.39).
Summarizing our findings, the outcomes supported our hypothesis that the procedure duration of bariatric procedures improved by working with fixed OR teams and by performing the same procedure several times on the same day. Efficiency gains of about 10% were realized mostly during surgery. The gains in peripheral OR activities were not found to be significant. Although such gains were found in another study for less complex procedures,2 standardization of the relatively more complex laparoscopic bariatric procedures did not produce efficiency gains in peripheral activities.
Procedure Duration: Further Discussion
Because the dependent variables in Table 6 consisted of log-transformed durations and the residuals of the models were approximately normally distributed, the estimated effects on the mean and on the SD of the durations (in minutes) were the same.d Therefore, the fixed-team effect of about 10% for procedure and surgical durations did not apply only for the mean duration, but also for the uncertainty in durations (measured by the SD). Working with fixed OR teams not only saved OR time, it also reduced the uncertainty by about 10%.
For the 3 regressions in Table 6, some of the standard deviations differed significantly (at 1% level), and we estimated the models by means of maximum likelihood (weighted least squares with estimated values of the standard deviations per year and per hospital). For all 3 regressions, a diagnostic analysis of the (weighted) residuals indicated, apart from the presence of some outliers, no clear deviations from normality and no clear patterns over time (measured as either surgeon-specific or hospital-specific bariatric experience). If we define a positive (negative) outlier as a value that lies more than 2 times the interquartile range above (below) the median, then at most 3% of the residuals were classified as outliers. These outliers were distributed quite symmetrically, up to 5 standard deviations above and below the median. The occurrence of outliers after correction for surgeon and procedure type effects was not surprising, because of large differences in relevant characteristics of obese patients, such as body weight, adhesions, visceral fat, enlarged liver, and airway management during anesthesia.
The results were rather robust with respect to various model variations. If the surgeon-specific experience was measured separately per type of bariatric procedure, the fixed-team effect was estimated to be slightly larger (about 15% instead of about 10%). We also estimated the regressions by ordinary least squares with White standard errors31 that correct for heteroskedasticity of unknown type. The resulting estimates and 99% confidence intervals for the fixed-team effects were similar to the ones reported before (e.g., for procedure time, the 99% CI is 7.5% to 18.3%, as compared to 5.0% to 15.3% in Table 6). For the fixed-team period, we also considered models with nontruncated values for the variables slot on day and same on day. As before, the slot position was not significant, whereas every next procedure of the same type within the same day saved time (99% CI, 2.5% to 6.2%, as compared to 2.8% to 7.4% in Table 6).
Laparoscopic bariatric surgery with OR teams that remained fixed during the day resulted in a better teamwork and safety climate for staff members, without loss of quality of patient care. Working with such fixed teams reduced procedure times by about 10%, with additional gains of about 5% per repetition of the same procedure within the same day. The speed of operation improved most if a fixed OR team performed the same procedure on several patients on the same day.
The outcomes of working with fixed teams provided better opportunities for OR planners, depending on their risk attitude,32 to schedule more patients per day. Although even in 2010 the schedule could already accommodate another procedure, it took until 2012 before the OR management decided, motivated by the outcomes of this study, to schedule an additional procedure per day for 1 of the 5 bariatric surgeons, and it is expected that the other bariatric surgeons will soon also be allowed to perform more operations per day. All laparoscopic bariatric procedures in both hospitals are currently scheduled with teams that remain fixed for the day. The OR management closely monitors the experiences of working with fixed teams because of the potential risk of personality clashes between team members who work together for a longer time.
Our study was restricted to the evaluation of short-term effects in 2 bariatric centers in the Netherlands. It is of course relevant to also evaluate the longer-term effects on patient outcomes and on the teamwork and safety climate, and to perform similar studies in other cultures and in ORs with more surgeons and with another case mix of procedures. It may be worthwhile to pay more attention to the effect of managerial interventions by preceding such studies by a phase of education, goal setting, and commitment, including emphasis on the performed managerial interventions.
Name: Pieter S. Stepaniak, PhD.
Contribution: This author helped design the study, analyze the data, and prepare the manuscript.
Name: Christiaan Heij, PhD.
Contribution: This author helped analyze the data and prepare the manuscript.
Name: Marc P. Buise, MD, PhD.
Contribution: This author helped design the study and prepare the manuscript.
Name: Guido H. H. Mannaerts, MD, PhD.
Contribution: This author helped design the study, perform the surgeries, and prepare the manuscript.
Name: J. Frans Smulders, MD.
Contribution: This author helped design the study, perform the surgeries, and prepare the manuscript.
Name: Simon W. Nienhuijs, MD, PhD.
Contribution: This author helped design the study, perform the surgeries, and prepare the manuscript.
This manuscript was handled by: Franklin Dexter, MD, PhD.
1. Haslam DW, James PTJ. Obesity Lancet 2005;366(9492):1197–209
2. Finkelstein EA, Trogdon JG, Cohen JW, Dietz W. Annual medical spending attributable to obesity: Payer- and servicespecific estimates. Health Affairs. 2009;28:822–31
3. Sjostrom L, Lendroos A, Peltonen M, Torgerson J, Bouchard C, Carlsson B, Dahlgren S, Larsson B, Narbro K, Sjöström CD, Sullivan M, Wedel H. Lifestyle, diabetes, and cardiovascular risk factors 10 years after bariatric surgery. N Engl J Med. 2004;351:2683–93
4. Johansson E, Bockerman P, Kiiskinen U, Heliovaara M. Obesity and labour market success in Finland: the difference between having a high BMI and being fat. Econ Hum Biol. 2009;7(1):36–45
5. Maggard MA, Shugarman LR, Suttorp M, Maglione M, Sugerman HJ, Livingston EH, Nguyen NT, Li Z, Mojica WA, Hilton L, Rhodes S, Morton SC, Shekelle PG. Metaanalysis: surgical treatment of obesity. Ann Intern Med. 2005;142:547–59
6. Buchwald H, Avidor Y, Braunwald E, Jensen MD, Pories W, Fahrbach K, Schoelles K. Bariatric surgery, a systematic review and metaanalysis. JAMA. 2004;292:1724–37
7. Wang Y, Beydoun MA. The obesity epidemic in the United States—gender, age, socioeconomic, racial/ethnic and geographic characteristics: a systematic review and meta-regression analysis. Epidemiol Rev. 2007;29:6–28
8. Kehlet H. Fasttrack colorectal surgery. Lancet. 2008;371(9615):791–3
9. Dexter F, Traub RD. How to schedule elective surgical cases into specific operating rooms to maximize the efficiency of use of operating room time. Anesth Analg. 2002;94:933–42
10. Pandit JJ, Dexter F. Lack of sensitivity of staffing for 8-hour sessions to standard deviation in daily actual hours of operating room time used for surgeons with long queues. Anesth Analg. 2009;108:1910–5
11. Dexter EU, Dexter F, Masursky D, Garver MP, Nussmeier NA. Both bias and lack of knowledge influence organizational focus on first case of the day starts. Anesth Analg. 2009;108:1257–61
12. Dexter F, Epstein RH. Typical savings from each minute reduction in tardy first case of the day starts. Anesth Analg. 2009;108:1262–7
13. Harders M, Malangoni MA, Weight S, Sidhu T. Improving operating room efficiency through process redesign. Surgery. 2006;140:509–14
14. Stepaniak PS, Vrijland W, de Quelerij M, de Vries G, Heij C. Working with a fixed operating room team on consecutive similar cases and the effect on case duration and turnover time. Arch Surg. 2010;145:1165–70
15. Cohen SG, Baily DE. What makes teams work: group effectiveness research from the shop floor to the executive suite. J Manage. 1997;23:239–90
16. International Federation for the Surgery of Obesity and Metabolic Disorders. Available at http://www.ifso.com
Accessed July 17, 2012
17. Weaver SJ, Rosen MA, Diaz Granados D, Lazzara EH, Lyons R, Salas E, Knych SA, McKeever M, Adler L, Barker M, King HB. Does teamwork improve performance in the operating room? A multilevel evaluation. Jt Comm J Qual Patient Saf. 2010;36:133–42
18. Lingard L, Espin S, Whyte S, Regehr G, Baker GR, Reznick R, Bohnen J, Orser B, Doran D, Grober E. Communication failures in the operating room: an observational classification of recurrent types and effects. Qual Saf Health Care. 2004;13:330–4
19. Muller S, Zalunardo MP, Hubner M, Clavien PA, Demartines NA. Fixed team program reduces complications and length of hospital stay after open colonic surgery. Gastroenterology. 2009;136:842–7
20. Pronovast PJ, Freischlag JA. lmproving teamwork to reduce surgical mortality. JAMA. 2010;304:1721–2
21. Neily J, Mills PD, Young-Xu Y, Carney BT, West P, Berger DH, Mazzia LM, Paull DE, Bagian JP. Association between implementation of a medical team training program and surgical mortality. JAMA. 2010;304:1693–700
22. Sexton JB, Helmreich RL, Neilands TB, Rowan K, Vella K, Boyden J, Roberts PR, Thomas EJ. The safety attitudes questionnaire: Psychometric properties, benchmarking data, and emerging research. BMC Health Serv Res. 2006;6:44
23. Sexton JB, Thomas EJ, Helmreich RL. Error, stress, and teamwork in medicine and aviation: cross sectional surveys. BMJ. 2000;320:745–9
24. Glossary of times used for scheduling and monitoring of diagnostic and therapeutic procedures.AORN J. 1997;66:601–6
25. Stepaniak PS, Heij C, Mannaerts GHH, de Quelerij M, de Vries G. Modeling procedure and surgical times for CPT-anesthesiasurgeon combinations and evaluation in terms of case duration prediction and OR efficiency. Anesth Analg. 2009;109:1232–45
26. Strum DP, May JH, Vargas LG. Modeling the uncertainty of surgical procedure times: comparison of log-normal and normal models. Anesthesiology. 2000;92:1160–7
27. Ramsay CR, Grant AM, Wallace SA, Garthwaite PH, Monk AF, Russell IT. Assessment of the learning curve in health technologies: A systematic review. Int J Technol Assess. 2000;16:1095–1108
28. Pisano GP. Learning-before-doing in the development of new process technology. Research Policy. 1996;25:1097–119
29. Thomas EJ, Sexton JB, Helmreich RL. Discrepant attitudes about teamwork among critical care nurses and physicians. Critical Care Med. 2003;31:956–959
30. Casella G, Berger RL Statistical Inference. 1990 Pacific Grove, CA Wadsworth
31. White H. A heteroskedasticity-consistent covariance matrix estimator and a direct test for heteroskedasticity. Econometrica. 1980;48:817–38
32. Stepaniak PS, Mannaerts GH, de Quelerij M, de Vries G. The effect of the operating room coordinator’s risk appreciation on operating room efficiency. Anesth Analg. 2009;108:1249–56