Impact of operative duration on postoperative pulmonarycomplications in laparoscopic versus open colectomy

Rachel M. Owen • Sebastian D. Perez •

Nathan Lytle • Ankit Patel • S. S. Davis •

Edward Lin • John F. Sweeney

Received: 1 November 2012 / Accepted: 22 March 2013

� Springer Science+Business Media New York 2013

Abstract

Background Prolonged operative duration is associated

with increased postoperative morbidity and mortality.

Although laparoscopic colectomy (LC) is associated with

longer operative duration compared with open colectomy

(OC), research shows paradoxically decreased morbidity

following LC versus OC. The direct impact of operative

duration on postoperative pulmonary complications (PPC)

following LC versus OC has not been analyzed.

Methods We queried the ACS/NSQIP 2009-2010 Public

Use File for patients who underwent elective LC and OC.

The associations between operative duration and a PPC

(pneumonia, intubation [48 h, and unplanned intubation)

were evaluated. Multivariable regression models were cre-

ated to determine the independent effect of operative time

on the development of PPC controlling for LC versus OC.

Results A total of 25,419 colectomies (13,741 laparo-

scopic and 11,678 open) were reviewed; 765 (3 %) patients

experienced at least one PPC. Regression modeling dem-

onstrated that for both LC and OC each 60-min increase in

operative time up to 480 min was associated with 13 %

increased odds of PPC [odds ratio (OR) 1.13; 95 % con-

fidence interval (CI) 1.07–1.19]. Beyond 480 min, each

additional 60-min interval was associated with 33 %

increased risk of PPC (OR 1.33; 95 % CI 1.12–1.58).

Overall, PPCs occurred half as often following LC [270

(2 %) laparoscopic vs. 497 (4.3 %) open; OR 0.45; 95 %

CI 0.39–0.53].

Conclusions Operative duration is independently associ-

ated with increased risk of PPC in patients undergoing LC

and OC. However, a laparoscopic approach carries half the

absolute risk of PPC and, when safe, should be preferentially

utilized despite a potential for prolonged operative duration.

Keywords Postoperative pulmonary complication �Operative duration � Laparoscopic colectomy � Open

colectomy � Colorectal surgery

Research suggests that prolonged operative duration can be

associated with increased postoperative morbidity and

mortality, especially postoperative pulmonary complica-

tions (PPC) [1–8]. PPC are associated with a considerable

increase in morbidity, mortality, and healthcare costs. One

study in particular demonstrated that the occurrence of PPC

independently reduced a patient’s median postoperative

survival by 87 % [9]. Furthermore, an analysis assessing

postoperative complications identified postoperative pneu-

monia as the most commonly observed complication,

which was subsequently associated with a 55 % increase in

hospital costs and an 89 % increase in length of stay [10].

It is estimated that nearly 25 % of patient deaths occurring

within 6 days of surgery are related to PPC and that an

astonishing one in five patients who develop a PPC die

within 30 days of surgery [3, 11, 12].

Presented at the SAGES 2013 Annual Meeting, April 17- April 20,

2013, Baltimore, MD.

R. M. Owen � N. Lytle � A. Patel � S. S. Davis � E. Lin �J. F. Sweeney (&)

Division of General and Gastrointestinal Surgery, Emory

University School of Medicine, 1364 Clifton Road NE,

Suite H-124, Atlanta, GA 30322, US

e-mail: jfsween@emory.edu

R. M. Owen

e-mail: rmedber@emory.edu

R. M. Owen � S. D. Perez � J. F. Sweeney

Department of Surgery Patient Safety and Data Management

Program, Emory University School of Medicine, Atlanta, GA,

US

123

Surg Endosc

DOI 10.1007/s00464-013-2949-9

and Other Interventional Techniques

Because PPC drive healthcare costs, increase hospital

length of stay, and substantially impact postoperative

morbidity and mortality, many studies have tried to

determine what patient- and operation-specific risk factors

contribute to PPC [3, 4, 7, 11–15]. Nasogastric intubation,

upper abdominal surgery, obesity, functional status, and

American Society of Anesthesiologist (ASA) class each

have been identified as risk factors for PPC. Consequently,

hospitals across the country have implemented various

prevention measures (aggressive spirometry, selective

nasogastric tube placement, nonnarcotic pain control) to

combat PPC in certain at-risk populations.

When comparing operative duration of laparoscopic

colectomy (LC) versus open colectomy (OC), the laparoscopic

approach is, on average, associated with a longer operative

time [16–21]. Despite the longer operative duration associated

with LC, multiple series within the literature report superior

outcomes and decreased morbidity and mortality associated

with LC compared to OC [17, 20, 22–26]. Specifically, studies

have demonstrated that the rate of PPC ranges from 1.0 to

7.1 % for LC compared to 1.0–11.9 % for OC; however, the

definition of PPC is not consistent across the series [17, 20, 22,

24, 25]. The current study evaluates the effect of operative

duration in LC and OC upon the development of PPC. We

hypothesize that regardless of preoperative comorbidities and

operative approach (LC vs. OC), each additional hour of

operative time is independently associated with an increased

risk of PPC. Moreover, we postulate that LC will be

Table 1 Standardized ACS/NSQIP definitions of postoperative pulmonary complications

Pneumonia Must meet criteria from both RADIOLOGY and SIGNS/SYMPTOMS/LABORATORY sections

Radiology

One definitive chest radiological exam (X-ray or CT) with at least one of the following:

• New or progressive and persistent infiltrate

• Consolidation or opacity

• Cavitation

Signs/symptoms/laboratory

For any patient, at least one of the following:

• Fever ([38 �C or [100.4 �F) with no other recognized cause

• Leukopenia (\4,000 WBC/mm3) or leukocytosis (C12,000 WBC/mm3)

• For adults C70 years old, altered mental status with no other recognized cause

AND at least one of the following:

• 5 % BAL-obtained cells contain intracellular bacteria on direct microscopic exam

• Positive growth in blood culture not related to another source of infection

• Positive growth in culture of pleural fluid

• Positive quantitative culture from BAL or protected specimen brushing

OR at least two of the following:

• New onset purulent sputum, change in sputum character, increased respiratory secretions

• New onset or worsening cough, or dyspnea, or tachypnea

• Rales or rhonchi

• Worsening gas exchange, increased oxygen requirements, or increased ventilator demand

Prolonged mechanical

ventilation

Total duration of ventilator-assisted respirations during postoperative hospitalization was [48 h.

This can occur at any time during the 30-day period postoperatively.

This time assessment is CUMULATIVE, not consecutive.

Ventilator-assisted respirations can be via endotracheal tube, nasotracheal tube, or tracheostomy tube.

The date recorded should be after the first 48 h from the time the patient was initially intubated. If the patient was

discharged from the OR intubated, record the date 48 h from the ‘‘Patient Out of Room’’ time.

Unplanned intubation Patient required placement of an endotracheal tube and mechanical or assisted ventilation because of the onset of

respiratory or cardiac failure manifested by severe respiratory distress, hypoxia, hypercarbia, or respiratory

acidosis.

In patients who were intubated for their surgery, unplanned intubation occurs after they have been extubated after

surgery.

In patients who were not intubated during surgery, intubation at any time after their surgery is considered

unplanned.

BAL bronchoalveolar lavage, ACS/NSQIP American College of Surgeons National Surgery Quality Improvement Program

Surg Endosc

123

paradoxically associated with an overall lower risk of PPC,

thus supporting the use of a laparoscopic approach even if

operative duration is increased.

Methods

Definitions

Due to the lack of a standardized definition of PPC, studies

often incorporate numerous signs and symptoms when

referring to PPC. Many of these series include diagnoses,

such as bronchitis, bronchospasm, atelectasis, and pleural

effusion, in their definition of PPC. In this analysis, we

follow the American College of Surgeons National Surgi-

cal Quality Improvement Program (ACS/NSQIP) definition

of PPC which includes postoperative pneumonia, pro-

longed mechanical ventilation beyond 48 h, and unplanned

intubation within 30 days of surgery. Patients who self-

extubated and were subsequently reintubated, as well as

patients who underwent additional surgical procedures

requiring intubation for general anesthesia purposes only,

were not considered to have unplanned intubation. We

utilized standardized ACS/NSQIP criteria for each com-

plication (Table 1). According to NSQIP Surgical Clinical

Reviewer (SCR) protocol, LC cases which were converted

to open are subsequently coded as OC. Operative duration

is defined as the time between surgical start (incision) and

surgical stop (closure).

Data collection

Data for this study came from the ACS/NSQIP Public Use

File (PUF) for years 2009 and 2010. ACS/NSQIP is a

nationally validated, risk-adjusted outcomes database that has

been well-described in the literature and is the only national

program that measures surgical outcomes to improve surgical

care by evaluating preoperative risk factors, postoperative

morbidity and mortality, and patient variable statistics [27–

29]. Data in the PUF include variables describing patient

demographics, preoperative comorbidities and risk factors,

laboratory values, operative variables, and postoperative

events using standardized definitions. In addition, the file

includes the calculated preoperative probabilities of postop-

erative morbidity and mortality for each patient, based on the

ACS/NSQIP risk adjustment models [30–33]. These calcu-

lated probabilities of morbidity and mortality allow us to risk-

adjust for one variable that takes into account numerous

patient characteristics (demographics, comorbidities, proce-

dure type, and institution) in our statistical models.

The PUF was queried for patients who underwent

elective LC or OC. In an effort to analyze a population of

truly elective cases, we excluded all cases which were

coded as emergent and cases in which the patients were

admitted [24 h preoperatively. Complete inclusion and

exclusion criteria are listed in Table 2.

LC and OC cases both with and without PPCs (pneu-

monia, intubation [48 h, and unplanned intubation) were

evaluated against operative duration, length of hospital

stay, and 30-day mortality. Upon review of operative times,

a few cases had unrealistically short operative durations.

Thus, cases within the bottom one percentile of operative

time (anything \44 min) were excluded due to the likeli-

hood of data collection error. All data are complete except

where noted within the text.

Statistical analysis

The primary study endpoint was the development of PPC.

Continuous variables are presented as mean and standard

deviation while categorical variables are presented as fre-

quencies with percentages. Analysis of associations

between independent variables and outcome were per-

formed using Chi-square analysis and Fisher’s exact test

for proportions and a two-sample t test for continuous

variables. Univariate analysis was utilized to identify any

differences between patients undergoing LC versus OC,

and between patients with and without PPCs.

The association between PPCs and operative time was

analyzed using multivariable logistic models to control for

the effects of operative approach (laparoscopic vs. open)

Table 2 Inclusion and exclusion criteria for cohort analysis

Includesa Excludes

Laparoscopic colectomy Emergent cases

44,204, 44,205, 44,206, 44,207,

44,208, 44,210, 44,211, 44,212

Preoperative admission [24 h

Open colectomy

44,140, 44,141, 44,143, 44,144,

44,145, 44,146, 44,147, 44,150,

44,151, 44,155, 44,160

Patients with any of the

following:

-ASA class 5

-DNR status

-Documented pre-operative

sepsis

-Preoperative chronic steroid

use

-Chemotherapy or radiation

within 30 days of procedure

-Disseminated cancer

-Wound class 4

Cases with bottom one

percentile operative timeb

ASA American Society of Anesthesiologists, DNR do not resuscitatea CPT codesb Less than 44 min

Surg Endosc

123

and differences in patient acuity at surgery time. Patient

acuity was adjusted for in two ways (in separate regression

models): by controlling for patient ASA class and preop-

erative functional status, and by controlling for the pre-

operative probability of morbidity (based on patient- and

procedure-specific risk factors) assigned to each patient by

ACS/NSQIP. Based on these models, the predicted prob-

ability of a PPC was generated and presented in a plot as a

function of operative time. All hypothesis testing was

performed using a two-sided alpha value of 0.05. Due to

our large cohort, small differences between the two large

study groups often resulted in statistical significance, thus

we considered not only the statistical significance, but also

the clinical significance of our findings. All data manage-

ment and statistical analyses were performed using SAS

9.2 (SAS Institute, Inc., Cary, NC) and SPSS 17 (IBM

SPSS Inc., Chicago, IL).

Results

A total of 25,419 elective cases (13,741 LC and 11,678

OC) were reviewed. Patient demographics based on

operative approach are listed in Table 3. The overall PPC

rate was 3 % (765 patients). On average, patients within

the OC group were 1.7 years older than LC patients (63.3

vs. 61.6 years, p \ 0.001). Dependent functional status,

higher ASA class (3 and 4), and preoperative probability of

morbidity were each significantly higher among the OC

patients. PPCs were more common following an open

approach [497 (4.3 %) open vs. 270 (2 %) laparoscopic,

p \ 0.0001]. Mean hospital length of stay was [2 days

longer for patients following OC (7.5 days vs. 5.2 days,

p \ 0.0001). There was no difference between mean

operative duration for LC and OC.

Patient differences between the PPC group and non-PPC

group are listed in Table 4. Patients with PPC were an

average of 6.8 years older, male, and non-Caucasian. More

than 75 % of PPC patients were ASA 3 or 4 compared with

only 40 % in the non-PPC group (p \ 0.0001). Patients

who were partially or totally functionally dependent before

surgery were more than six times more likely than func-

tionally independent patients to develop a PPC [odds ratio

(OR) 6.42; 95 % confidence interval (CI) 5.09–8.1].

Average hospital length of stay for patients with PPC was

three times longer than those without (p \ 0.0001). Thirty-

day mortality occurred in 92 (0.4 %) patients without PPC,

whereas 110 (14.4 %) patients with one or more PPC died

postoperatively. Overall, patients experiencing one or more

PPC were 44 times more likely to die within 30 days of

surgery than those who did not (OR 44.7; 95 % CI

33.5–59.6).

The average operative duration for patients with PPC

was significantly longer than those without PPC (3.0 vs.

2.7 h, respectively; p \ 0.0001). The relationship between

operative time, procedure type, and the percentage of

patients with at least one PPC is shown in Fig. 1. In all time

intervals except for one, the rate of PPC among patients

who underwent OC surpassed those who underwent LC.

The only instance where the rate of PPC was higher among

laparoscopic cases was during the 8–9 h timeframe; how-

ever, this finding could be confounded by the relatively

small number of patients whose operation lasted 8–9 h (15

LC and 45 OC).

Results of linear regression analysis are shown in

Table 5. In all models, LC was associated with half the risk

of PPC compared with OC. In the model controlling for

differences in preoperative probability of morbidity, each

60-min increase in operative time for operations\480 min

was associated with a 12 % increased risk of PPC (OR

1.12; 95 % CI 1.06–1.18). For operations exceeding

480 min, each additional 60 min of operative time beyond

the 8-h mark was associated with a 36 % increased risk of

PPC (OR 1.36; 95 % CI 1.13–1.64). Similar odds were

calculated in the model controlling for ASA class and

functional status.

Table 3 Demographics by procedure

Patient variable LC (N = 13,741)

n (%)

OC (N = 11,678)

n (%)

p value

Age (year), mean (SD) 61.6 (±14) 63.3 (±14.4) \0.0001

Sexa

Male 6,445 (47.2) 5,359 (46.1) 0.0603

Female 7,201 (52.8) 6,279 (54)

Racea

White 11,129 (86) 9,145 (84.8) 0.0108

Non-white 1,818 (14) 1,641 (15.2)

ASAa

Class I 609 (4.4) 319 (2.7) \0.0001

Class 2 8,215 (59.8) 5,653 (48.4)

Class 3 4,665 (34) 5,271 (45.2)

Class 4 243 (1.8) 421 (3.6)

Pre-Op functional status

Independent 13,501 (98.3) 11,299 (96.8) \0.0001

Partially or totally

dependent

240 (1.8) 379 (3.3)

Pre-Op probability of

morbidity, % (SD)

13.5 (±5.1) 21.6 (±7.4) \0.0001

Operative Duration,

Mean (SD), hours

2.7 (±1.2) 2.7 (±1.4) 0.1313

LOS, Mean (SD), days 5.2 (±10.3) 7.5 (±6.1) \0.0001

Postoperative

pulmonary

complication

270 (2) 497 (4.3) \0.0001

Mortality 67 (0.5) 135 (1.2) \0.0001

ASA American Society of Anesthesiologists, LC laparoscopic colectomy, LOSlength of stay, OC open colectomya Data incomplete for patient sex, race, and ASA class; thus numbers will not

add up to 24,419

Surg Endosc

123

Figure 2 illustrates the substantial increase in the inci-

dence of PPCs following 8 h of operative time. OC lasting

\8 h were associated with a PPC rate of 4.1 % (480/

11,586), whereas LC within the same timeframe carried a

PPC rate of 1.9 % (265/13,703). On the other hand, PPC

occurred in 18.5 % (17/92) of patients if their OC lasted

longer than 8 h. LC[8 h in duration were associated with

less than half as many PPC (7.9 %, 3/38 patients).

Regression modeling was used to calculate the predicted

probability of PPC based on operative duration and oper-

ative approach (Fig. 3). While the probability of PPC

increases with operative time, two salient findings are

apparent: 1) the probability of PPC during LC lasting up to

8 h is still less than the probability of PPC in OC following

\1 h of operative time, and 2) the probability of PPC

dramatically escalates following 8 h of operative time,

regardless of approach.

Discussion

Multiple series within the literature have demonstrated

overall efficacy and clinical benefit of LC versus OC [17,

20, 22–25]. What has not been previously considered,

however, is that a laparoscopic approach can often take

longer, especially in the academic surgical environment

where the learning curve of laparoscopic surgery often is

steep. Due to the fact that previous research has associated

worse outcomes with longer operative durations [1–7], it

could be argued that the longer operative times associated

with LC might offset the potential for improved outcomes.

The current study provides evidence that even when the

operative times are substantially longer than OC, LC are

associated with significantly lower rates of PPC.

While the majority of series within the literature report

prolonged operative times associated with LC [16–21], our

results show that the average operative time for LC vs. OC

is equivalent (2.7 h for both). We believe there are several

reasons why the current data show similar times for LC and

OC. First, LC cases that are converted to OC cases are

coded as OC, thus likely increasing the average operative

time associate with OC. Second, more than half of the cases

within our series are LC, possibly representing an increas-

ing trend of surgeons opting to choose the laparoscopic

approach. As a result, the increased volume of LC cases is a

likely marker of increased technical proficiency among

colorectal and general surgeons, thus leading to decreased

operative times associated with the laparoscopic approach.

Reasons for increased PPC among the OC group, despite

operative duration, could be numerous. First and foremost,

the substantially increased amount of postoperative pain

associated with an open versus laparoscopic procedure is

likely a major factor in developing PPC. Multiple series

have demonstrated that LC is associated with significantly

reduced amounts of pain following surgery [18–20]. The

considerably larger midline incision following OC can lead

to a domino effect of events, which increases the risk of

PPC. Severe pain often decreases patient compliance with

incentive spirometry. Furthermore, intensified pain leads to

increased need for narcotics, which further suppresses

patient respiratory drives, thus leading to decreased pul-

monary toilet and increased postoperative atelectasis.

Studies also have associated prolonged postoperative ileus

and extended hospital length of stays following OC, both of

which can realistically lead to PPC [18–20, 26]. Many

patients with postoperative ileus also have nasogastric

tubes, thus increasing the risk for aspiration of gastric

contents. Longer hospital stays are associated with

increased risk of nosocomial infections, particularly hos-

pital-acquired pneumonia.

In addition to operative duration and laparoscopic versus

open approach, the current study also identifies other

Table 4 Demographics by postoperative pulmonary complication

Patient variable No PPC

(N = 24,652)

n (%)

PPC

(N = 767)

n (%)

p value

Age (year), mean (SD) 62.2 (± 14.2) 69 (± 17.8) \0.0001

Sexa

Male 11,377 (46.4) 427 (55.7) \0.0001

Female 13,141 (53.6) 339 (44.3)

Racea

White 19,683 (85.5) 591 (82.7) 0.0332

Nonwhite 3,335 (14.5) 124 (17.3)

ASAa

Class I 921 (3.7) 7 (0.9) \0.0001

Class 2 13,696 (55.6) 175 (22.9)

Class 3 9,450 (38.4) 486 (63.5)

Class 4 567 (2.3) 97 (12.7)

Pre-Op functional status

Independent 24,127 (97.9) 673 (87.7) \0.0001

Partially or totally

dependent

525 (2.1) 94 (12.3)

Pre-Op probability of

morbidity, % (SD)

17 (7.2) 25.6 (10.8) \0.0001

Procedure

Laparoscopic 13,471 (54.6) 270 (35.2) \0.0001

Open 11,181 (45.4) 497 (64.8)

Operative duration

(hour), mean (SD)

2.7 (± 1.3) 3.0 (± 1.9) \0.0001

LOS (days), mean

(SD)

5.8 (± 8.1) 17.6 (± 15.6) \0.0001

Mortality 92 (0.4) 110 (14.4) \0.0001

ASA American Society of Anesthesiologists, LOS length of stay, PPCpostoperative pulmonary complicationa Data incomplete for patient sex, race, and ASA class; thus numbers

will not add up to 24,419

Surg Endosc

123

variables that have a significant impact upon the risk of

developing PPC. We demonstrate that older, non-Cauca-

sian, male patients, ASA class 3 or higher and those who

are at least partially dependent from a functional stand-

point are substantially more likely to develop PPC. Pre-

vious studies within the literature also have demonstrated

that elderly male patients are at higher risk of PPC [3, 5–7,

11, 15, 34]. Furthermore, many series within the literature

also note ASA class and functional status to be significant,

if not the most significant, risk factors for PPC [3, 5, 7, 11,

13]. The significant difference in the rate of PPC among

Caucasians and non-Caucasians is a novel finding that

requires additional prospective studies to further verify this

result.

Fig. 1 Percentage of PPC by

procedure type and operative

duration. PPC postoperative

pulmonary complication

Table 5 Logistic regression models

Odds ratio estimates for PPC

Effect Model 1 Model 2 Model 3

Crude Controlling for NSQIP preop

probability of morbidityaControlling for ASA class

and functional status

OR (95 % CI) OR (95 % CI) OR (95 % CI)

Approach

Laparoscopic versus open 0.452 (0.389, 0.525) 0.452 (0.389, 0.526) 0.553 (0.474, 0.644)

Operative duration

Each hour before 8 h 1.119 (1.064, 1.177) 1.118 (1.063, 1.177) 1.126 (1.07, 1.185)

Each hour after 8 h 1.362 (1.131, 1.639) 1.363 (1.132, 1.641) 1.33 (1.122, 1.576)

NSQIP National Surgical Quality Improvement Program, PPC postoperative pulmonary complication, OR odds ratio, CI confidence intervala NSQIP-derived preoperative risk of postoperative morbidity as a tool that allows for risk-adjustment of numerous variables among patients

(including patient demographics, preoperative comorbidities, type of procedure and type of institution)

Surg Endosc

123

Patients within the OC group were more likely to be

older, have a higher ASA class, and be partially or totally

functionally dependent before surgery, thus placing them at

higher risk for PPC than those in the LC group. Although

these differences likely represent selection criteria of the

operating surgeon, controlling for these variables (age,

ASA, and functional status) did not eliminate the additional

risks associated with an open approach and/or prolonged

operative duration. A recent series investigating safety of

LC in patients with high ASA class (3 and 4) showed that

not only is LC a safe option for high-risk patients, but it

also is associated with better outcomes than OC [35].

Furthermore, because the results of our regression analyses

are risk-adjusted, the comparison of patients in equal time

intervals is adjusted for differences in preoperative risk,

therefore making a fair comparison between the two pro-

cedures at any given time. Additionally, our results dem-

onstrate that the risk of PPC following LC is less than OC

even when comparing it to lesser time intervals (i.e. LC at

450 min has less risk than OC at 200 min). As a result, we

argue that patients with higher preoperative risks of post-

operative morbidity and mortality need to be especially

considered for LC if at all possible.

The lower rates of PPC following LC not only improve

patient morbidity, but also further advocate for an overall

cost savings compared with OC. Although the direct

operating room costs of LC are initially greater than OC,

studies have shown that total hospital charges following the

laparoscopic approach are significantly lower, mostly due

to shorter hospital length of stay [23, 35–39]. With the

average PPC costing upwards of $50,000 [8], costs fol-

lowing LC are further reduced secondary to significantly

decreased rates of postoperative complications. Further-

more, a previous series by our authors demonstrates that

PPC significantly increase the risk of unplanned hospital

readmissions by a factor of three (OR 3.45; 95 % CI

2.08–5.71) [40]. As a result, potential cost-savings are

associated with preventing not only a postoperative com-

plication, but also that of a subsequent readmission.

Interestingly, our findings have been echoed by a recent

series [41] reporting outcomes following prolonged lapa-

roscopic cholecystectomy versus converted procedures.

Data demonstrate that despite the increase in operative

duration with prolonged laparoscopic cases, hospital post-

operative complication rates were equivocal, hospital

length of stay was significantly shorter, and overall cost

were significantly decreased compared to the conversion to

open group. As a result, the authors conclude that pro-

longed laparoscopic cases are not associated with adverse

outcomes.

We believe there are several limitations within our

study. First, even though NSQIP data were gathered in a

prospective manner, the analysis of PPC rates associated

with operative time was conducted in a retrospective

fashion. Due to the retrospective nature of the analysis, it is

plausible that there are unobserved variables or selection

biases which could be contributing to the differences

between the patients who did and did not develop PPCs.

Furthermore, the NSQIP PUF file contains de-identified

patient data, thus it is likely there are surgeon-specific or

hospital-specific factors that are confounding our results.

Second, cases were collected and stratified based upon

CPT codes. While this is useful for analysis, there are

differences between patients that cannot be captured. For

example, a colectomy for cancer versus a colectomy for

diverticulitis theoretically could be considered different

cases. Furthermore, we do not differentiate between right

and left colectomies. Moreover, some of the open cases

may have been started laparoscopically and then converted

to open procedures at some point during the operation;

however, it is not possible to detect such cases within the

study database. Due to the limitations of using CPT codes

Fig. 2 Percentage of PPC before/after 8 h of surgery, by procedure

type. PPC postoperative pulmonary complication

Fig. 3 Predicted probability of PPC. PPC postoperative pulmonary

complication

Surg Endosc

123

to create our patient cohorts, there remains an element of

selection bias that cannot be eliminated. Although we tried

to create a homogenous patient population via our exclu-

sion criteria and control for patient differences in our risk-

adjustment models, it is possible that our procedure

groupings are too broad.

Third, the database includes cases from both high- and

low-volume centers, which likely have various different

postoperative protocols for the patient recovery-phase. The

NSQIP PUF contains de-identified data at both the patient

and institutional level, thus it is not possible to control for

these differences in our analysis. Future studies looking at

such differences in center volume and surgeon experience

in relation to operative duration and postoperative out-

comes are needed.

Conclusions

Although factors contributing to the development of PPCs

are multifactorial, our data demonstrate that operative

duration is independently associated with increased risk of

PPC following both LC and OC. Despite the similar risk

associated with operative duration between laparoscopic

and open approaches, laparoscopic cases were more than

two times less likely than open cases to be associated with

PPCs. As a result, LC was associated with much lower

rates of PPCs, even when the cases lasted longer than their

open counterparts. These findings further advocate that,

when safe, laparoscopy should be preferentially utilized in

colectomy cases despite a potential for prolonged operative

duration.

Acknowledgments American College of Surgeons National Surgi-

cal Quality Improvement Program and the hospitals participating in

the ACS NSQIP are the source of the data used herein; they have not

verified and are not responsible for the statistical validity of the data

analysis or the conclusions derived by the authors.

Disclosures Drs. Owen, Lytle, Patel, Davis, Lin, Sweeney, and Mr.

Perez have no conflict of interest or financial ties to disclose.

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