World J Surg DOI 10.1007/s00268-013-2447-1

The Acute Surgical Unit Model Verses the Traditional ‘‘On Call’’ Model: A Systematic Review and Meta-Analysis Vinayak Nagaraja • Guy D. Eslick Michael R. Cox



 Socie´te´ Internationale de Chirurgie 2014

Abstract Background The acute surgical unit (ASU) is a novel model for the provision of emergency general surgery care. The ASU model was initially developed in New South Wales hospitals during 2005 and 2006. Several studies have analysed the effects on patient outcomes and timeliness of care for nontrauma patients presenting with acute general surgical conditions. The purpose of this study was to perform a meta-analysis to determine the efficacy of the ASU model compared with the traditional on-call model for specific conditions. Methods A systematic search was conducted using MEDLINE, PubMed, EMBASE, Current Contents Connect, Cochrane library, Google Scholar, Science Direct, and Web of Science. Original data were extracted from each study and used to calculate a pooled odd ratio (OR) and 95 % confidence interval (CI). Results The search identified 18 studies; appendectomy (n = 9), acute cholecystitis (n = 7), and small-bowel obstruction (SBO) (n = 2). In the appendectomy cohort, the proportion of appendicular perforation were similar in preASU and ASU period (OR 1.02, 95 % CI 0.77–1.37, p = 0.13). The incidence of complications in the appendectomy cohort was significantly lower in the ASU group; 14.5 % pre-ASU and 10.9 % post-ASU (OR 1.649, 95 % CI 0.732–3.714, p = 0.009). The negative appendectomy rate was similar for the pre- and post-ASU groups (OR 1.07, 95 %

V. Nagaraja  G. D. Eslick  M. R. Cox (&) The Whiteley-Martin Research Centre, The Discipline of Surgery, Sydney Medical School, The University of Sydney, Nepean Hospital, Level 5, South Block, Penrith, NSW 2751, Australia e-mail: [email protected]

CI 0.88–1.31, p = 0.83). Likewise the conversion rate to open surgery and total hospital stay were similar between the two groups. The proportion of night time operations reduced significantly in the ASU period (OR 1.9, 95 % CI 1.32–2.74, p = 0.001). In the acute cholecystitis cohort, the conversion rate to open surgery was significantly higher in the pre-ASU group (15.1 %) compared with the post-ASU group (7.5 %) (OR 1.879, 95 % CI 1.072–3.293, p = 0.04) The incidence of complications was higher in the pre-ASU (14 %) compared with the post-ASU (6.8 %) group (OR 2.231, 95 % CI 1.372–3.236, p = 0.03). The mean hospital stay was significantly lower in the ASU period (5.3 vs. 3.7 days, p = 0.0063). There was insufficient data available to analyse outcomes for SBO. Conclusions The ASU model provides a safe surgical environment for patients and is associated with a reduced complication rate for appendectomy and laparoscopic cholecystectomy for acute cholecystitis. There is a reduced conversion rate and a shorter length of stay for patients with acute cholecystitis. Overall, the ASU model has translated to better outcomes for patients presenting with acute general surgical conditions.

Introduction Traditionally in many countries, including Australia, New Zealand, and the United Kingdom, nontrauma patients presenting with an acute general surgical condition were admitted under the care of the general surgeon on call, who was usually occupied with other activities, such as office or clinic consults or elective surgery, which often occur outside of the hospital. This resulted in potential delays in the consultant evaluation and operative treatment of these acute surgical patients. This time-honoured model has

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created difficulties in ongoing management of the acute general surgical workload in hospitals globally [1–3]. The acute surgical unit (ASU) is a novel model in the provision of emergency general surgical care developed in Australia during 2005 and 2006 at The Prince of Wales Hospital, Sydney followed by Nepean Hospital, Sydney and Fremantle Hospital, Perth [4–6]. Recently, it has been implemented by a number of Hospitals in Australia and New Zealand [7–9]. In the United States, an Acute Care Surgery model was introduced to improve theatre time allocation and allow trauma surgeons greater exposure to acute general surgery with the reduction in need for trauma surgery. The US model for acute care surgery combines the care of trauma and emergency surgical presentations using a similar model to the ASU models in Australasia [3, 10– 18]. The establishment of an ASU is a change in the organisational approach to the management of acute general surgical patients [19]. All of the ASU models in Australia and New Zealand are consultant-driven, independent units that manage all acute general surgical admissions [4, 5, 7–9]. There are variations in rostering, handover mechanisms and the ongoing care arrangements for the patients. One key component for all Australasian ASU models is that the consultant’s sole responsibility and role is the assessment and management of the acute general surgical patients. To date, a number of studies have analysed the effects on patient health outcomes and timeliness of care for nontrauma patients within the scope of acute general surgery conditions, but no meta-analysis has been performed. This study provides a detailed analysis of the outcomes for patient care for specific acute surgical conditions comparing the traditional ‘‘on call’’ model with the ASU model.

Methods Study protocol We followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines where possible in performing our systematic review [20]. A systematic search through MEDLINE (from 1950), PubMed (from 1946), EMBASE (from 1949), Current Contents Connect (from 1998), Cochrane Library, Google Scholar, Science Direct, and Web of Science to November 2013. The search terms included ‘‘Acute Surgical Unit’’, ‘‘Acute Care Surgery,’’ ‘‘Acute Care Surgery Service,’’ ‘‘Acute Care Emergency Surgical Service,’’ ‘‘Acute Care Surgical Service’’ AND ‘‘Emergency Surgical Unit’’ (ESU), which were searched as text word and as exploded medical subject headings where possible. No language restrictions

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were used in either the search or study selection. The reference lists of relevant articles also were searched for appropriate studies. A search for unpublished literature was not performed. Study selection We included studies that met the following inclusion criteria: •



Studies comparing patient outcomes using ASU or acute care surgery models with that of traditional oncall model for specific conditions (acute appendicitis, acute cholecystitis and small bowel obstruction). Original data (or odds ratios) reporting on the number of patients outcomes.

Data extraction Data extraction was performed using a standardized data extraction form, collecting information on the publication year, study design, number of cases, total sample size, population type, country, continent, mean age and clinical data. The event rate and confidence intervals (CIs) were calculated. Statistical analysis Pooled event rate and 95 % CIs were calculated for sensitivity, accuracy and detection rate using a random effects model [21]. Heterogeneity was tested using the Cochran’s Q statistic, with p \ 0.1 indicating heterogeneity, and quantified the degree of heterogeneity using the I2 statistic, which represents the percentage of the total variability across studies which is due to heterogeneity. I2 values of 25, 50, and 75 % corresponded to low, moderate and high degrees of heterogeneity respectively [22]. The quantified publication bias using the Egger’s regression model [23], with the effect of bias assessed using the fail-safe number method. The fail-safe number was the number of studies that we would need to have missed for our observed result to be nullified to statistical non-significance at the p \ 0.05 level. Publication bias is generally regarded as a concern if the fail-safe number is less than 5n ? 10, with n being the number of studies included in the meta-analysis [24]. All analyses were performed with Comprehensive Meta-analysis (version 2.0) Software, Biostat, Englwood, NJ (2005).

Results The original search strategy retrieved 1,259 studies. The abstracts were reviewed and after applying the inclusion

World J Surg

Potentially relevant studies identified and screened for retrieval (n= 1259 )

Studies excluded, editorials, reviews, (n= 11241 )

Studies retrieved for more detailed evaluation (n= 18 ) Studies excluded (n=0)

Studies included in final analysis (n=15)

Fig. 1 Flowchart of studies included in the meta-analysis

and exclusion criteria, articles were selected for full-text evaluation. Of the articles selected, only 18 studies met full criteria for analysis (Fig. 1) and are summarised in Table 1. The search only identified studies assessing the role in acute appendicitis (9 studies), acute cholecystitis (7 studies), and small bowel obstruction (SBO) (2 studies). There was sufficient data to allow independent analysis of the effect of the ASU models on acute appendicitis and

acute cholecystitis, but there was insufficient data to allow for an analysis for SBO. For the appendectomy cohort, the proportion of appendicular perforation were similar in pre-ASU and ASU period (OR 1.02, 95 % CI 0.77–1.37, p = 0.13). The incidence of all complications in the appendectomy cohort was significantly lower in the ASU group: 14.5 % pre-ASU and 10.9 % ASU (OR 1.64, 95 % CI 0.73–3.71, p = 0.009). The negative appendectomy rate was similar for the pre-ASU and ASU groups (OR 1.07, 95 % CI 0.88–1.31, p = 0.83). Likewise, the conversion rate to open surgery was similar between the pre ASU and ASU groups (OR 0.98, 95 % CI 0.51–1.9, p = 0.59). The proportion of night time operations reduced significantly in the ASU period (OR 1.9, 95 % CI 1.32–2.74, p = 0.01). Time from ED to OR (12 vs. 10 h, p = 0.07) was significantly lower in ASU period. The mean hospital stay was similar in both cohorts (2.5 days pre-ASU compared with 2.4 days for ASU, p = 0.5). For the cholecystectomy cohort, the conversion rate to open surgery was significantly higher in the pre-ASU group with 15.1 % pre ASU and 7.5 % in the ASU group (OR 1.879, 95 % CI 1.072–3.293. p = 0.04; Fig. 2). The incidence of complications was higher in the pre ASU (14 %) compared with the ASU (6.8 %) group (OR 2.231, 95 % CI 1.372–3.236, p = 0.003; Fig. 3). The mean time from presentation to operation tended to be lower (65.3 h for pre-ASU compared with 38.5 h for ASU), but this was not significant (p = 0.074). The mean total hospital stay was significantly lower in the ASU period (5.3 vs. 3.7 days, p = 0.0063).

Table 1 Characteristics of the studies included in the systematic review and meta-analysis Author

Year

Country

Condition

Patients pre ASU

Patients ASU

Ekeh et al. [16]

2008

USA

Acute appendicitis

273

279

Earley et al. [15]

2006

USA

Acute appendicitis

127

167 266

Gandy et al. [25]

2010

Australia

Acute appendicitis

176

Cubas et al. [17]

2012

USA

Acute appendicitis

82

93

Qureshi et al. [34]

2011

Canada

Acute appendicitis

139

117

Faryniuk et al. [35]

2013

Canada

Acute appendicitis

35

77

Brockman et al. [36]

2013

Australia

Acute appendicitis

351

357

Poh et al. [37]

2013

Australia

Acute appendicitis

256

283

Pillai et al. [38]

2013

New Zealand

Acute appendicitis

875

982

Pepingco et al. [28]

2010

Australia

Acute cholecystitis

114

157

Cubas et al. [17]

2012

USA

Acute cholecystitis

51

62

Britt et al. [30] Mercer et al. [39]

2009 2004

USA UK

Acute cholecystitis Acute cholecystitis

38 59

83 110 115

Lehane et al. [27]

2010

Australia

Acute cholecystitis

87

Lau et al. [18]

2011

USA

Acute cholecystitis

81

71

Faryniuk et al. [35]

2013

Canada

Acute cholecystitis

5

39

Lien et al. [40]

2012

Australia

Bowel obstruction

50

171

Faryniuk et al. [35]

2013

Canada

Bowel obstruction

27

26

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World J Surg Fig. 2 Laparoscopic cholecystectomy conversion rate

Laparoscopic conversion rate Study name

Statistics for each study

Odds ratio and 95% CI

Odds Lower Upper ratio limit limit Z-Value p-Value Pepingco et al Cubas et al Britt et al Mercer et al Lehane et al.

2.326 0.378 1.754 3.418 1.470 1.879

1.044 0.073 0.561 1.551 0.543 1.072

5.182 2.066 1.964 -1.157 5.478 0.967 7.532 3.049 3.981 0.758 3.293 2.201

0.039 0.247 0.334 0.002 0.449 0.028 0.01

0.1

1

Favours Pre ASU

Fig. 3 All complications (cholecystectomy)

10

100

Favours ASU

All complications Study name

Statistics for each study

Odds ratio and 95% CI

Odds Lower Upper ratio limit limit Z-Value p-Value Pepingco et al Cubas et al Britt et al Lehane et al. Lau et al

1.795 3.900 0.899 2.188 3.016 2.231

0.468 6.879 0.853 1.285 11.835 2.403 0.254 3.180 -0.165 0.931 5.141 1.795 1.034 8.795 2.021 1.372 3.626 3.236

0.393 0.016 0.869 0.073 0.043 0.001 0.01

0.1

1

10

100

Favours Pre ASU Favours ASU

Table 2 Overall odds ratio and 95 % CI for patient outcomes for acute appendicitis and acute cholecystitis Operation Appendectomy

Cholecystectomy

Outcome

Odds ratio

95 % CI

I2 57.73

Number of appendix perforations

1.02

0.77–1.37

Negative appendectomy rate

1.07

0.88–1.31

0

Proportion night time operations

1.9

1.32–2.74

Laparoscopic appendectomy conversion rate

0.98

0.51–1.9

73.97

All complications (appendectomy)

1.649

0.732–3.714

78.86

Laparoscopic cholecystectomy conversion rate

1.879

1.072–3.293

35.95

All complications (cholecystectomy)

2.231

1.372–3.236

0

0

p value 0.13 0.83 0.01 0.59 0.009 0.04 0.003

Heterogeneity and publication bias

Discussion

The heterogeneity of outcomes has been summarized in Table 2. The reason for significant heterogeneity may be attributed to different population groups. Conflicting results can potentially arise from the retrospective nature of studies that were compared. No publication bias was detected using the Egger’s regression model.

Acute appendicitis and cholecystitis are the most common general surgical emergencies seen in emergency departments. Deficiency of timely access to acute surgery is an increasing problem globally [1–3]. There are numerous factors contributing to this problem including, shortage of surgeons, increased subspecialization postfellowship

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training, inadequate access to acute operating theatres and lack of a dedicated on-call team [8]. The results of this meta-analysis show that for patients requiring appendicectomy there was a similar incidence of perforation at the time of surgery but a significant reduction in the incidence of postoperative complications. This may reflect the increase consultant supervision of the operation as well as more timely assessment and reduced time to the operating room seen in the ASU models [4, 5]. The improved timeliness in care observed in the ASU cohort was a consequence of the presence of a team available inhouse to perform emergency surgery during daylight hours. The length of time to theatre from emergency department was reduced in the ASU group. This reduction in time may reflect improved consultant availability for patient assessment. Earlier recognition of surgical candidates combined with greater control of theatre allocation may decrease time to theatre. Although there was a reduced complication rate noted for appendicectomy in the ASU group, the total inpatient stay was the same for both groups. Although there was a 2 h reduction in time of presentation to the operation this 2 h reduction would have minimal impact on the total length of stay. The reduction in the complication rate from 14.9 to 10.9 % would not be expected to effect the duration of hospital stay. There was a significant reduction in the proportion of appendectomies done overnight. The likely reasons for this are the improved access to operating theatres during daylight hours in the ASU models as well as the improved availability of the consultant surgeon. One of the studies reported a significant reduction in overnight appendectomies (26.1 % pre-ASU to 15 % ASU) with an increase in the proportion of overnight cases having perforation (8.7 % pre-ASU to 14.7 % ASU) [25]. This indicated that the sick patients requiring more urgent appendicectomy were being appropriately selected. In the acute cholecystitis cohort, there were clear advantages in the ASU model with a reduced conversion rate, reduced complication rate, and reduced total bed stay. The reduction in conversion rate may be due to an increase in consultant availability for supervision of the surgery and more timely surgery [4, 5, 26, 27]. In one study, the introduction of the ASU occurred with a change in routine management of acute cholecystitis with an increase in laparoscopic cholecystectomy being performed on the index admission from 55 to 93 % [28]. Other studies may have had similar changes in the management of acute cholecystitis but they were not reported. Operating on cases earlier and not allowing them to settle may account for some of the reduction in the conversion rate, but is not the sole explanation. Other factors improving these outcomes may include improved performance associated with increased frequency of laparoscopic cholecystectomy in

acute cholecystitis and reduction in out-of-hours surgery when the surgical team is fatigued. The proportion attributable to these reasons cannot be determined from the present study. The reduced complication rate for surgery in acute cholecystitis could in part be related to the reduction in the conversion rate. Cases requiring conversion to open surgery are associated with a higher complication rate, in particular wound and respiratory complications [29]. Other factors contributing to a reduce complication rate may include increased consultant supervision and a reduction in overnight operating [5, 28]. There was a significant reduction in the mean total length of stay by 1.6 days for the acute cholecystitis cohort. Although the time from presentation to surgery was not significantly different (p = 0.074) there was a clear trend with a 26.8 h reduction. The more timely surgical intervention is a contributor to the reduction in the total inpatient stay and also may account for some of the reduction in the conversion rate and the complication rate. In turn, the reduced conversion rate and complication rate would be expected to reduce the duration of hospital stay. The significant reduction in hospital stay is associated with significant cost savings as reported by one of the studies with an average cost of $5,936.20 in the pre-ASU group compared with a cost of $4,873 in the ASU group [30]. Another reported system improvement associated with the introduction of ASU models is the reduction in overnight operations with an associated increase in the proportion of operations being performed in hours [5, 25, 31]. In one study, the rate of overnight surgery for all presentations fell from 15.8 to 7.8 % with an associated rise in daytime surgery from 57.4 to 77.5 % [5]. In another report, 55.4 % of all emergent procedures were performed between 7:30 am and 5:30 pm, compared with 70 % after implementation (p = 0.0002). As expected, procedures performed after 5:30 pm decreased from 44.6 to 30 % (p \ 0.001) [31]. The unnecessary performance of surgery out of hours in known to be associated with increased complication rates [32]. Several studies have reported the increase in the proportion of cases that are supervised by a consultant in the ASU model [4–6, 8, 25, 31]. The greater consultant presence in theatre and more assisting by consultants has created an improved environment for training. The increased consultant presence has ensured that both the patient and the trainee achieve better outcomes [26, 27, 33]. The junior medical staff (interns and residents) are provided with better on the job training, clinical, and assessment, due to the presence of a consultant in the hospital all day [5]. Unfortunately, there was insufficient data in the two studies comparing outcomes for SBO to be assessed. Acute appendicitis and acute cholecystitis are the two most

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frequent presentations to ASUs [4, 5, 8] and, therefore, provide the best data sets for comparison of the traditional and ASU models. Overall, the results of this study clearly demonstrate the improved patient outcomes associated with the implementation of the ASU model for the management of acute appendicitis and acute cholecystitis. The patient outcomes, including more timely assessment, reduced length of stay, reduced out of hours operating, and reduced complication rates, are likely to occur for other acute general surgical presentations, such as soft tissue abscesses, small and large bowel obstruction, acute pancreatitis, acute diverticulitis, and perforated peptic ulcer disease. These results should encourage the increase uptake of the ASU model for the care of acute general surgical admissions and the effective separation of emergency and elective surgical workloads. References 1. Uranues S, Lamont E (2008) Acute care surgery: the European model. World J Surg 32:1605–1612. doi:10.1007/s00268-0089501-4 2. Hoyt D, Kim H, Barrios C (2008) Acute care surgery: a new training and practice model in the United States. World J Surg 32:1630–1635. doi:10.1007/s00268-008-9576-y 3. Diaz JJ Jr, Miller RS, May AK et al (2007) Acute care surgery: a functioning program and fellowship training. Surgery 141:310–316 4. Parasyn AD, Truskett PG, Bennett M et al (2009) Acute-care surgical service: a change in culture. ANZ J Surg 79:12–18 5. Cox MR, Cook L, Dobson J et al (2010) Acute surgical unit: a new model of care. ANZ J Surg 80:419–424 6. Von Conrady D, Hamza S, Weber D et al (2010) The acute surgical unit: improving emergency care. ANZ J Surg 80:933–936 7. Poole GH, Glyn T, Srinivasa S et al (2012) Modular acute system for general surgery: hand over the operation, not the patient. ANZ J Surg 82:156–160 8. Hsee L, Devaud M, Middelberg L et al (2012) Acute Surgical Unit at Auckland City Hospital: a descriptive analysis. ANZ J Surg 82:588–591 9. Hsee L, Devaud M, Civil I (2012) Key performance indicators in an acute surgical unit: have we made an impact? World J Surg 36:2335–2340. doi:10.1007/s00268-012-1670-5 10. Spain DA, Miller FB (2005) Education and training of the future trauma surgeon in acute care surgery: trauma, critical care, and emergency surgery. Am J Surg 190:212–217 11. Reilly PM, Schwab CW (2007) Acute care surgery: the academic hospital’s perspective. Surgery 141:299–301 12. Malangoni MA (2007) Acute care surgery: the general surgeon’s perspective. Surgery 141:324–326 13. Committee on Acute Care Surgery American Association for the Surgery of Trauma (2007) The acute care surgery curriculum. J Trauma Acute Care Surg 62:553–556 14. Austin MT, Diaz JJJ, Feurer ID et al (2005) Creating an emergency general surgery service enhances the productivity of trauma surgeons, general surgeons and the hospital. J Trauma Acute Care Surg 58:906–910 15. Earley AS, Pryor JP, Kim PK et al (2006) An acute care surgery model improves outcomes in patients with appendicitis. Ann Surg 244:498–504

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The acute surgical unit model verses the traditional "on call" model: a systematic review and meta-analysis.

The acute surgical unit (ASU) is a novel model for the provision of emergency general surgery care. The ASU model was initially developed in New South...
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