Surgical Endoscopy

, Volume 24, Issue 2, pp 270–276

Laparoscopic surgery significantly reduces surgical-site infections compared with open surgery

Authors

    • Minimally Invasive SurgeryVeteran Affairs North Texas Healthcare System
  • Samuel E. Wilson
    • University of California, Irvine Medical Center
  • Ninh T. Nguyen
    • University of California, Irvine Medical Center
Article

DOI: 10.1007/s00464-009-0569-1

Cite this article as:
Varela, J.E., Wilson, S.E. & Nguyen, N.T. Surg Endosc (2010) 24: 270. doi:10.1007/s00464-009-0569-1

Abstract

Background

Surgical-site infections (SSIs) are nosocomial infectious complications causing significant morbidity, mortality, and hospital costs. Recently, the US Department of Human Health Services and the Centers for Medicare and Medicare Services outlined measures intended to decrease and prevent hospital-acquired infections such as SSI. This study aimed to compare the incidence of SSI after laparoscopic and open surgery.

Methods

A retrospective analysis of a large administrative, clinical, and financial database (University Health System Consortium) of US Academic Medical Centers and affiliated community hospitals was conducted. Patients who underwent laparoscopic (n = 94,665) or open (n = 36,965) appendectomy, cholecystectomy, antireflux surgery, or gastric bypass between 2004 and 2008 were included in the analysis. The main outcome measure was inpatient diagnosis of SSI after laparoscopic and open surgery.

Results

During the 45-month study period, a total of 131,630 patients underwent one of four selected procedures. Overall, the incidence of SSI was significantly lower in laparoscopic (483 of 94,665, 0.5%) than in open (669 of 36,965, 1.8%) surgery (p < 0.01). Largely, laparoscopic techniques offered a protective effect against SSI (odds ratio [OR], 0.28; 95% confidence interval [CI], 0.25–0.31). Patients treated with laparoscopy were 72% less likely to experience an SSI. This protective effect was shown to be sustained after stratification by severity of illness (minor: OR, 0.19; 95% CI, 0.14–0.26; moderate: OR, 0.30; 95% CI, 0.25–0.35; major/extreme: OR, 0.65; 95% CI, 0.54–0.79), admission status (elective: OR, 0.25; 95% CI, 0.20–0.31; urgent: OR, 0.38; 95% CI, 0.28–0.53; emergent: OR, 0.29; 95% CI, 0.25–0.34), and wound classification (dirty wounds: OR, 0.45; 95% CI, 0.37–0.54).

Conclusions

In US academic medical centers, laparoscopy significantly reduces SSI. Patients treated with laparoscopic procedures are less likely to experience SSI. After stratification by severity of illness, admission status, and wound classification, laparoscopic techniques showed a protective effect against SSI.

Keywords

LaparoscopyOpen surgeryPostoperative wound infectionSurgical-site infection

Surgical-site infections (SSIs) are known hospital-acquired surgical infectious complications associated with significant morbidity, mortality, and hospital costs. According to the National Nosocomial Infections Surveillance (NNIS) System, SSI is the third most commonly reported nosocomial infection [1]. Among surgical patients, SSI is the most common nosocomial infection.

A decade ago, the Centers for Disease Control and Prevention (CDC) set Guidelines for Prevention of Surgical Site Infections [2]. However, surgical techniques such as laparoscopy were not specifically addressed as possible preventive measures for SSI. More recently, the US Department of Human Health Services (HHS) and the Centers for Medicare and Medicare Services (CMS) have outlined measures aimed to decrease and prevent hospital-acquired infections such as SSI. Moreover, the CMS has restructured payment provisions for several hospital-acquired conditions, for example, mediastinitis after coronary artery bypass surgery.

Although most hospital-acquired infectious measures have focused on preventive antimicrobials, we theorize that certain surgical techniques, such as laparoscopy, will further decrease SSI by limiting the degree of trauma and contamination of surgical sites. However, studies evaluating the impact of laparoscopic techniques on the incidence of SSI at US hospitals are few.

Elective, urgent and emergent admission status were studied for all procedure groups. In this study, using a large clinical database of US Academic Medical Centers, we determined and compared the incidence of SSI between laparoscopic and open surgical procedures. The findings of this study will add to the body of literature regarding the impact of laparoscopic surgical techniques on hospital-acquired SSI.

Materials and methods

Data set

The University HealthSystem Consortium (UHC) is an alliance of 97 academic medical centers and 153 of their affiliated hospitals, representing 90% of the nation’s nonprofit academic medical centers. The UHC database is an administrative, clinical, and financial database that provides benchmark measures on the use of health care resources for the purpose of comparative data analysis between academic institutions. It contains discharge information on inpatient hospital stay including patient characteristics, length of hospital stay, overall and specific postoperative morbidity, and observed and expected (risk-adjusted) in-hospital mortality.

To accomplish risk adjustment, the UHC uses regression modeling techniques in combination with the 3 M Health Information Systems, Agency for Healthcare Research and Quality comorbidity software and the UHC complication profiler to assign an illness severity level and expected length of hospital stay, costs, and probability of mortality to every patient in the database.

The assignment of an illness severity level is based on a combination of principal and secondary diagnoses to define different levels of severity and complexity of treatment. The four illness severity categories are minor, moderate, major, and extreme. For example, the severity of a comorbidity such as diabetes would be categorized as moderate and recent myocardial infarction as extreme.

The three illness severity categories are minor, moderate, and major/extreme. The morbidity rate was defined as “the presence of all procedure- and non-procedure-related complications diagnosed before hospital discharge.” The in-hospital mortality rate was defined as “the percentage of patients who died before discharge from the hospital.” The risk-adjusted mortality ratio was defined as “the proportion between the observed and the expected mortality,” and the length of stay was defined as “the period from the index procedure to hospital discharge.”

The UHC clinical database provides an estimated cost of patient care using a ratio of cost-to-charge methodology. The UHC collects detailed patient charges at the revenue code level and estimates costs by multiplying charges by the cost center-specific ratio of cost to charges from the annual Medicare cost report submitted by individual hospitals. The diagnosis of SSI was based on the presence of a procedure-related surgical wound infection complication after laparoscopic and open surgery diagnosed before hospital discharge.

Approval for use of the UHC patient-level data in this study was obtained from the Institutional Review Board of the University of California, Irvine Medical Center, and the UHC.

Study cohort

We analyzed the UHC hospital discharge records of all patients 18 years of age or older who underwent one of four commonly performed gastrointestinal procedures, namely, appendectomy, cholecystectomy, antireflux surgery, or Roux-en-Y gastric bypass. Hospital discharge records were reviewed between 1 October 2004 and 30 June 2008.

Analysis of the four gastrointestinal procedures required the use of appropriate diagnosis and procedural codes as specified by the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM). These four procedures were selected because they have both the laparoscopic and open ICD-9-CM procedural codes for their respective procedures. The specific ICD-9-CM procedure codes for laparoscopic gastric bypass and laparoscopic antireflux surgery first became available only on 1 October 2004. All procedures were performed on an inpatient basis.

The ICD-9-CM diagnosis codes for laparoscopic (47.01) and open (47.0, 47.09) appendectomy, acute appendicitis (540, 540.9), and perforated appendicitis (540.0, 540.1) were used. Perforated appendicitis included a subcategory for generalized peritonitis or peritoneal abscess (i.e., dirty wounds). For laparoscopic (51.23, 51.24) and open (51.21, 51.22) cholecystectomy, the principal ICD-9-CM diagnosis codes for cholelithiasis with (574.0, 574.00, 574.01, 574.1, 574.10, 574.11) and without (574, 574.2) acute cholecystitis were used. For laparoscopic (44.67) and open (44.65, 44.66) antireflux surgery, the principal ICD-9-CM diagnosis codes for esophagitis (530.1, 530.10, 530.11, 530.12, 530.19) and esophageal reflux (530.81) were used. For laparoscopic (44.38) and open (44.31, 4439) gastric bypass, the principal ICD-9-CM diagnosis codes for morbid obesity (278, 278.0, 278.00, 278.01) were used.

To increase the homogeneity of the cohort, the diagnosis-related group (DRG-288) for operative treatment of obesity also was used to examine the data for gastric bypass. Age groups were defined as ages 18–39 years, 40–64 years, and older than 65 years. The most common race/ethnicities were analyzed including whites, blacks, and Hispanics. Elective and urgent/emergent admission status was studied for all procedure groups.

Main outcome measures

The main study outcome was the overall incidence and individual rate of SSI after four laparoscopic and open surgical procedures: appendectomy, cholecystectomy, antireflux surgery, and gastric bypass. The odds ratios (ORs) for the development of SSI after laparoscopic and open procedures were analyzed.

Statistical analysis

We compared patient characteristics (gender, age groups, race/ethnicity, and severity class), length of hospital stay, 30-day readmission, and overall and individual rates of SSI after laparoscopic and open surgery. The rate of SSI after laparoscopic versus open surgery also was examined according to the severity of illness, admission status, and degree of wound contamination. Data are expressed as mean ± standard deviation.

Differences in patient characteristics and SSIs between laparoscopic and open groups were analyzed using Fisher’s exact test or Pearson’s chi-square test. Univariate analysis was performed, and the 95% confidence interval (CI) of the OR were obtained. Continuous variables were compared using Student t-tests. Statistical analysis was performed using Epi-Info statistical software, version 3.3.2 (CDC, Atlanta, GA, USA). A p value less than 0.01 was considered significant.

Results

Demographics

During the study period, a total of 131,630 patients underwent one of the four selected procedures: appendectomy (n = 54,353), cholecystectomy (n = 34,448), antireflux (n = 7,342), or gastric bypass (n = 35,487). The great majority of patients had laparoscopic surgery (n = 94,665, 72%), whereas a lower number underwent open surgery (n = 36,965, 28%).

The distribution of laparoscopic and open techniques for all procedures is shown in Table 1. The number of females was significantly greater in the laparoscopic group. The preponderance of patients younger than 64 years received laparoscopic procedures, whereas the group older than 65 years had open surgery more often. Whites underwent laparoscopic procedures more commonly, whereas blacks and Hispanics had greater numbers of open procedures. The proportion of patients with a minor severity of illness or a “low risk” level was greater for the laparoscopic approach. Patients with moderate or major/extreme severity of illness preferentially underwent open operations. Most of the laparoscopic procedures were performed on an elective basis, whereas the open operations were performed on an urgent or emergent basis. As expected, the majority of appendectomies (82.5%) and cholecystectomies (55%) were performed emergently, whereas most of the antireflux (89.5%) and gastric bypass (97.3%) procedures were performed electively. Of the laparoscopic appendectomies, 28.7% were perforated (dirty cases), whereas 34.6% of the open procedures had a perforation.
Table 1

Demographic data for patients who underwent laparoscopic and open surgeries

Variable

Laparoscopic

Open

p Value

Total cases

94,665

36,965

<0.01

Procedure (%)

    Appendectomy

61.5

38.5

<0.01

    Cholecystectomy

80.8

19.2

<0.01

    Antireflux

76.5

23.5

<0.01

    Gastric bypass

78.3

21.7

<0.01

Gender (%)

    Female

63.3

49.3

<0.01

    Male

36.7

50.7

<0.01

Age groups (years)

    18–39

44.1

43.0

<0.01

    40–64

46.5

44.9

<0.01

    ≥65

9.4

12.1

<0.01

Race/ethnicity (%)

    White

69.7

67.2

<0.01

    Black

14.1

15.1

<0.01

    Hispanic

16.2

17.7

<0.01

Severity of illness (%)

    Minor

59.6

47.8

<0.01

    Moderate

35.0

42.2

<0.01

    Major/extreme

5.4

10.0

<0.01

Admission status (%)

    Elective

42.6

31.3

<0.01

    Urgent

11.4

13.2

<0.01

    Emergent

46.0

55.5

<0.01

Values are number of cases and proportions (%). Laparoscopy versus open surgery groups (p < 0.01, Fisher’s exact test). Other race/ethnicities not shown

In-hospital main outcomes

Laparoscopic surgery offered significantly lower overall morbidity (including SSI); shorter hospital stay, and lower hospital costs (Table 2). The risk-adjusted mortality ratio, although comparable between surgical techniques, was lower for laparoscopic antireflux surgery and higher for open cholecystectomy, with a higher observed mortality than expected.
Table 2

In-hospital outcomes for patients who underwent laparoscopic and open surgeries

Variable

Laparoscopic

Open

p Value

Total cases

94,665

36,965

<0.01

Overall morbidity (%)

    Appendectomy

8.5

10.0

<0.01

    Cholecystectomy

8.6

25.0

<0.01

    Antireflux

10.5

25.2

<0.01

    Gastric bypass

7.4

13.4

<0.01

Risk-adjusted mortality ratio

    Appendectomy

0.7

0.7

NA

    Cholecystectomy

0.7

1.1

NA

    Antireflux

0.2

0.5

NA

    Gastric bypass

0.8

0.9

NA

Length of stay (days)

    Appendectomy

2.1 ± 2.3

3.2 ± 3.2

<0.01

    Cholecystectomy

3.3 ± 3.6

6.5 ± 6.2

<0.01

    Antireflux

3.1 ± 4.8

8.2 ± 11.3

<0.01

    Gastric bypass

2.6 ± 2.1

4.0 ± 4.5

<0.01

Costs (US$)

    Appendectomy

7,751 ± 6,218

8,091 ± 8,802

<0.01

    Cholecystectomy

9,170 ± 8,984

14,848 ± 17,471

<0.01

    Antireflux

10,043 ± 10,924

17,409 ± 22,447

<0.01

    Gastric bypass

13,611 ± 7,760

14,158 ± 14,755

<0.01

30-day readmission (%)

    Appendectomy

2.4

3.6

<0.01

    Cholecystectomy

2.1

4.4

<0.01

    Antireflux

1.9

3.0

<0.01

    Gastric bypass

2.5

4.9

<0.01

NA not applicable

Data are presented are means ± standard deviations and proportions (%). Risk adjusted mortality ratio (observed to expected mortality). Laparoscopy versus open surgery groups (p < 0.01, t-test or Fisher’s exact test when applicable). Overall morbidity includes surgical-site infection (SSI)

Overall, SSI was diagnosed during the index hospitalization for 1,152 patients (0.9%). Of these patients, 483 (0.5%) of 94,665 had laparoscopic, and 669 (1.8%) of 36,965 (p < 0.01) underwent open surgery. Laparoscopic appendectomy, cholecystectomy, antireflux surgery, and gastric bypass procedures all were associated with significantly lower rates of SSI than the corresponding open surgeries.

The SSI complication rates for individual procedures are shown in Table 3. Patients with minor and moderate severity of illness who experienced SSI had primarily open procedures, whereas those in the major/extreme category who experienced SSI had laparoscopy. For all four procedures, the length of hospital stay, although high with both techniques, was significantly shorter for the laparoscopic than for the open operations. The overall hospital costs related to the treatment of SSI was significantly higher for laparoscopic appendectomy and anti-reflux surgery and for open cholecystectomy. For all the procedures analyzed, the 30-day readmission rates were significantly higher for the open surgery groups than for the laparoscopy groups. Most notably, the readmission rates for open cholecystectomy and gastric bypass were nearly twice as high as for their laparoscopic counterparts.
Table 3

In-hospital outcomes for patients who experienced SSI complications after laparoscopic and open surgery

Variable

Laparoscopic

Open

p Value

Total SSI cases

483

669

<0.01

SSI (%)

    Appendectomy

0.7

1.9

<0.01

    Cholecystectomy

0.4

2.2

<0.01

    Antireflux

0.3

1.4

<0.01

    Gastric bypass

0.4

1.2

<0.01

Severity of illness (%)

    Minor

13.3

15.7

<0.01

    Moderate

44.1

50.2

<0.01

    Major/extreme

42.7

34.1

<0.01

Length of hospital stay (days)

    Appendectomy

10.8 ± 5.3

11.4 ± 6.3

<0.01

    Cholecystectomy

11.8 ± 12.0

15.1 ± 9.0

<0.01

    Antireflux

20.5 ± 46.7

25.1 ± 26.4

<0.01

    Gastric bypass

13.6 ± 11.2

16.1 ± 15.0

<0.01

Hospital costs (US$)

    Appendectomy

22,088 ± 38,784

19,814 ± 9,610

<0.01

    Cholecystectomy

26,200 ± 31,136

34,841 ± 17,293

<0.01

    Anti-reflux

57,324 ± 7,496

50,677 ± 44,811

<0.01

    Gastric bypass

42,450 ± 13,721

42,250 ± 20,839

NS

NS not significant

Data are means ± standard deviations for the number of cases and the proportion of total cases (%). SSI versus overall surgery groups (p < 0.01, t-test or Fisher’s exact test when applicable)

Odds for surgical-site infection

Overall, patients undergoing laparoscopic procedures had 72% less probability of experiencing a SSI (Table 4). The likelihood of experiencing a SSI was 64% less for patients who underwent a laparoscopic appendectomy, 81% less for those who had a laparoscopic cholecystectomy, 81% less for those who had laparoscopic antireflux surgery, and 67% less for those who underwent a laparoscopic gastric bypass.
Table 4

Odds ratio for the development of surgical-site infections after laparoscopic compared with open surgery

Procedure

OR

95% CI

Chi-square

p Value

Appendectomy

0.36

0.31–0.42

168.0

<0.01

Cholecystectomy

0.19

0.15–0.24

219.2

<0.01

Antireflux

0.19

0.10–0.36

31.7

<0.01

Gastric bypass

0.33

0.25–0.43

68.3

<0.01

Overall

0.28

0.25–0.31

517.6

<0.01

OR odds ratio, CI confidence interval

p < 0.01, chi-square test (χ2), comparison with open surgery

Surgical technique was significantly associated with SSI (chi-square, 517.6; p < 0.01). In general, laparoscopy offered a protective effect against SSI for all the procedures analyzed. This protection was shown to be sustained after stratification by severity of illness as follows: minor severity (OR, 0.19; 95% CI, 0.14–0.26), moderate severity (OR, 0.30; 95% CI, 0.25–0.35), and major/extreme severity (OR, 0.65; 95% CI, 0.54–0.79). The greatest impact was observed for the minor severity of illness category (81% less probability of having an SSI).

In addition, after stratification by admission status, laparoscopic surgery also showed prevention of SSI development as follows: elective admission status (OR, 0.25; 95% CI, 0.20–0.31), urgent admission status (OR, 0.38; 95% CI, 0.28–0.53), and emergent admission status (OR, 0.29; 95% CI, 0.25–0.34). The main influence observed was with elective laparoscopic procedures (75% less probability of experiencing a SSI). When laparoscopy was used to treat perforated acute appendicitis with peritonitis or abdominal abscess (dirty wounds), the patient had 55% less probability of experiencing a SSI than with open appendectomy (OR, 0.45; 95% CI, 0.37–0.54).

Discussion

Analysis of the outcomes data contained in a large clinical database of US Academic Medical Centers found that the incidence of SSI after four commonly performed laparoscopic and open gastrointestinal procedures was markedly lower for laparoscopy. The findings showed that laparoscopic surgery offered a protective effect against SSI compared with open operations. This protective effect was shown to be maintained after stratification for severity of illness, admission status, and degree of surgical-site contamination. For each operation, patients who underwent the laparoscopic operation were less likely to experience an SSI.

Surgical-site infections, formerly termed surgical wound infections, are one of the most frequent postoperative infectious complications [3]. Among all surgical patients, SSI was the most common hospital-acquired surgical infection [4]. When surgical patients with SSI died, the great majority of the deaths were related to the infection. Furthermore, SSI is associated with a longer hospital stay and additional hospital costs [5]. In addition, patients with SSI had longer and costlier hospitalizations than patients who did not have such infections [6, 7]. They were twice as likely to die, more likely to spend time in an intensive care unit (ICU), and more than five times more likely to be readmitted to the hospital.

Our results are supported by previous publications comparing SSI rates between laparoscopic and open surgery. Most recently, the report of Romy et al. [8] on a Swiss SSI surveillance program showed that laparoscopic surgery was associated with a decreased risk for SSI after appendectomy, cholecystectomy, and colectomy. Similarly, it was demonstrated previously from large nationwide databases that for colon resections performed to manage benign and malignant diseases, laparoscopic colectomy had a significantly lower incidence of SSI than open colectomy [912]. Also, in a small group of patients with gastric cancer, laparoscopic gastric resections were found to be associated with a lower SSI rate than open resections [13].

In a second study, our group also showed that laparoscopic appendectomy provided lower SSI rates than open appendectomy, particularly for morbidly obese individuals [14]. In a separate large database study, Nguyen et al. [15] showed that patients who had an open gastric bypass were five times more likely to experience an SSI, and this difference was maintained after control for risk severity. Richards et al. [16] also concluded that laparoscopic cholecystectomy was associated with lower SSI rates than open cholecystectomy, even after adjustment for several risk factors.

Laparoscopic or minimally invasive techniques have been available since 1985, when the first laparoscopic cholecystectomy was performed by Mühe in Germany [17]. Soon thereafter, the laparoscopic method was adopted with enthusiasm by US surgeons. The major differences between laparoscopic and open procedures are the method of access, the method of exposure, and the extent of operative trauma. Findings also have shown laparoscopy to be a physiologically superior operation compared with open surgery because it causes less impairment of immediate postoperative pulmonary function, less systemic stress, improved immunologic responses, and less local tissue trauma [1822]. The contributing factors to the lower SSI rates for laparoscopically treated patients are believed to be a shorter surgical incision, decreased tissue trauma and contamination, and elimination of mechanical retraction of the abdominal wall. Not to be considered inconsequential, an SSI occurring after laparoscopic surgery has less impact because the infectious process is lessened by the much smaller surgical site (up to 15 mm).

Although the laparoscopic approach is known to have higher operating room costs, mainly due to laparoscopic equipment expenses, the total hospital costs are offset by a reduction in the length of hospital stay and a decrease in the number of costly complications. Although both approaches appear to be safe, laparoscopic surgery was not only associated with a shorter length of hospital stay, less overall morbidity, and lower hospital costs, but additionally provided a protective effect against SSI for all procedures examined. As demonstrated in prior studies, patients who experienced SSI complications had a significantly longer hospital stay and higher hospital costs than those who did not. However, those with SSI had a shorter hospital stay if they had undergone laparoscopic procedures, with overall hospital costs comparable with open surgery.

A trend toward the use of laparoscopic techniques, particularly in “low-risk” and younger surgical groups, was evident for patients undergoing elective procedures. Nevertheless, the protective benefits of laparoscopy against SSI were shown to be maintained when patients were stratified by severity of illness, admission status, and the presence of peritonitis or abscess. It is plausible that groups considered “high risk” and elderly that undergo urgent or emergent operations resulting in “dirty” wounds also may benefit from minimally invasive approaches.

We have shown that the surgical approach itself may lessen hospital-acquired SSI. Indeed, laparoscopic techniques have been shown to reduce SSI rates for a wide variety of gastrointestinal procedures including the four common operations analyzed in the current study.

One limitation of the UHC database is that it does not provide information regarding complications occurring after discharge, even if the complication occurred within 30 days after the surgery. This would tend to bias our results in favor of laparoscopic operations because such patients would have an earlier discharge and therefore less time for observation for wound infection. However, patients who underwent open surgery had significantly higher readmission rates within 30 days. Also, there is no information on postoperative infection experienced by patients who had laparoscopic surgery converted to open surgery. Finally, we performed only a univariate analysis and severity-of-illness stratification. Given the characteristics of the UHC database, we were not able to conduct a multivariate or stepwise regression analysis.

In conclusion, we found that laparoscopic surgical techniques significantly decreased the incidence of SSI for patients hospitalized at academic medical centers. This advantage was shown to persist when patients were stratified by severity of illness, admission status, and degree of wound contamination. Compared with open surgical techniques, laparoscopic surgery conferred protection against SSI for the common gastrointestinal procedures studied. The results of this study should encourage surgeons and federal health agencies to view laparoscopic surgical techniques as an evidence-based approach for reducing the incidence of hospital-acquired SSI.

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© Springer Science+Business Media, LLC 2009