Positioning-Related Complications of Minimally Invasive Radical Prostatectomies

Abstract

Background and Purpose:

Because of recent advances in minimally invasive surgical techniques, robot-assisted radical prostatectomy (RARP) has become the primary treatment option in prostate cancer. RARP, however, necessitates patients to be placed in a steep Trendelenberg position, which presents multiple opportunities for complications relating to the positioning of the patient. Our study aims to study the prevalence and demographic predictors of these positioning complications and assess their impacts on length of stay (LOS) and total cost.

Patients and Methods:

We included patients who underwent RP from 2008 to 2009 using data extracted from the Nationwide Inpatient Sample database. Positioning complications (eye, nerve, compartment syndrome/rhabdomyolysis) were identified using patient-level diagnosis and procedural International Classification of Disease, 9th edition, Clinical Modification codes. Logistic regression models assessed relationships between demographic factors and occurrence of complications and the effects of them on prolonged LOS and total inpatient cost.

Results:

Positioning complications occurred in 0.4% of cases with eye complications contributing the most to this frequency. Laparoscopic RP procedure (odds ratio [OR]=2.88, P<0.01) and comorbidities (OR=2.34, P<0.01) were highly associated with increased odds of positioning complication occurrence, whereas RARP procedures (OR=0.93, P>0.4) were not associated with positioning complications. Having positioning complications increased a patient's odds of having increased inpatient costs and extended LOS by almost 400% and 300%, respectively.

Conclusion:

The steep Trendelenberg position used in RARP was not shown to be associated with patient positioning-related complications in this sample. The occurrence of positioning-related complications, however, places huge burdens on total inpatient costs and LOS.

Introduction

Prostate cancer is the most common noncutaneous cancer in U.S. men, making its most common treatment, radical prostatectomy (RP), one of the most commonly performed surgeries.¹ With the advent of minimally invasive surgical techniques, robot-assisted RP (RARP) has become the primary treatment option of choice by both physicians and patients since its introduction in 2001.² Previous studies have found that RARP provides similar oncologic outcomes, fewer postoperative complications, and shorter convalescence time compared with open procedures.^2

–5 These benefits have helped to increase the demand for this procedure and allow RARP to overtake open radical prostatectomy (ORP) as the procedure of choice.^6
–8

RARP necessitates patients being placed in the steep Trendelenburg position during surgery, in which the patient lies face up with his head and body tilted 25 to 45 degrees downward and legs in the lithotomy position.⁹ This position uses gravity to pull the abdominal viscera away from the operative field but may have negative physiologic effects when the patient is left in this position for extended periods.⁸ Previous studies and case reports have described positioning complications in laparoscopic and robotic urologic procedures involving the eyes (i.e., postoperative visual loss), nerves, and extremities (rhabdomyolysis and compartment syndrome).^{8

–16} Previous studies have assessed complications relating to prolonged exposure to the steep Trendelenburg position, but none has described positioning complications after RARP in a national, population-based sample.^8
–10

The primary aim of this study is to characterize the positioning complications of RARP nationally, specifically focusing on complications likely related to time spent in the steep Trendelenburg and lithotomy positions, such as rhabdomyolysis, compartment syndrome, neuralgias, and eye injuries), and exploring accompanying patient and hospital factors that may influence these complications. In addition, we sought to determine the effect of these positioning complications on total hospital costs and lengths of stay (LOS).

Patients and Methods

Sample

This was a retrospective study using inpatient data from 2008 to 2009 extracted from discharge information in the Healthcare Cost and Utilization Project Nationwide Inpatient Sample (NIS) database. NIS is assembled annually by the Agency for Healthcare Research and Quality and provides data on more than 8 million hospital admissions, encompassing discharge information from 44 states and more than 1000 hospitals. These data are used by researchers and policymakers to follow national trends in healthcare utilization, costs, and access. NIS is specifically designed to represent a 20% sample of the United States with a weighting system that allows for population level estimates.

RP case selection

NIS includes diagnostic and procedural field codes classified according to International Classification of Diseases, 9th edition, Clinical Modification (ICD-9CM) coding. In selecting cases, we identified patients who had a diagnosis of prostate cancer and had undergone open or minimally invasive RP starting in late 2008, once an identifiable ICD-9 code for robot assistance became available.

Covariates

Patient-level covariates included age, race, insurance status, number of comorbidities, and patient income based on ZIP code. All patient-level covariates were treated as categorical variables, with the exception of age, which was continuous. Hospital-level covariates of interest included number of hospital beds, annual hospital RP case volume, and hospital teaching status. Bed count (small (<200), medium (201–400), large (>400 beds)) and teaching status and location (urban, urban-teaching, or rural) were coded as categorical variables by NIS. Annual RP case volume was calculated by dividing the total number of RPs performed at each hospital by the number of years that hospital appears in the NIS, which varies.

Outcome measures

Outcome measures of interest included the probability of occurrence of a complication related to patient positioning, increased inpatient costs (as a binary and continuous outcome), and prolonged LOS. We measured the occurrence of positioning complications using the ICD-9CM codes pertaining to injuries of the eyes (acute conjunctivitis, conjunctival edema, orbital edema, etc.), nerves (brachial plexus lesions, ulnar nerve lesions, radial nerve lesions, etc.), rhabdomyolosis, and compartment syndrome. These events were identified as potential complications that may arise because of the difference in patient positioning during a robotic vs an open procedure and also because of the presence of the robot itself and its working elements. Prolonged LOS and increased inpatient costs were defined as at or above the 90th percentile in hospital stay and in costs for our entire sample. Cost information was determined by converting total hospital inpatient charges to costs, using the NIS-supplied charge-to-cost numeric convertor.

Statistical analysis

Chi-square and Fisher exact tests were used to compare groups and to assess univariate level associations between patient- and hospital-level covariates and the outcomes of interest. Multivariable logistic regression models, utilizing generalized estimating equations, were used to assess the associations between our outcomes of interest and the covariates. These models were fit to determine predictors of positioning-related complications, as well as prolonged LOS, increased patient costs, and mortality, in which occurrence of positioning complications was included as a covariate.

Statistical significance was two-sided and defined as a P value <0.05. All statistical analyses were performed using SAS 9.2 (Cary, NC). Any sample size with fewer than 11 samples were suppressed per NIS for 0<n<11. The Columbia University Medical Center Institutional Review Board (IRB) has approved this research as not human subjects because of the use of publicly available de-identified patient data (IRB approval # AAAI7009).

Results

We identified a weighted sample of 175,699 patients with a diagnosis of prostate cancer who underwent RP in 2008 to 2009, all of whom were included in our univariate and multivariate analyses. Among them, 61,656 (35.1%) patients had RARP, 2682 (1.5%) patients had laparoscopic robotic prostatectomy (LRP), and 111,361 (63.4%) patients had ORP. Table 1 lists patient and hospital characteristics of the sample.

Table 1.

Sample Demographics

	ORP		LRP		RARP
	N=111,361		N=2682		N=61,656
Factors	N	%	N	%	N	%
Mean age	61.5 years		62.0 years		61.3 years
Positioning complications
One or more	413	0.4%	DS	1%	249	0.4%
None	110,948	99.6%	2647	99%	61,407	99.6%
Race
White	69,396	62.3%	1853	69%	41,128	66.7%
Black	10,932	9.8%	196	7%	5136	8.3%
Hispanic	4991	4.5%	DS	2%	2347	3.8%
Asian Pacific Islander	1449	1.3%	DS	0%	856	1.4%
Native American	216	0.2%	0	0%	893	1.4%
Other	2591	2.3%	98	4%	1610	2.6%
Missing	21,787	19.6%	468	17%	9686	15.7%
Insurance type
Private insurance	68,407	61.4%	1730	65%	39,468	64.0%
Medicare	34,966	31.4%	883	33%	18,982	30.8%
Medicaid	2187	2.0%	DS	1%	875	1.4%
Other	5474	4.9%	DS	1%	2272	3.7%
Missing	327	0.3%	0	0%	59	0.1%
Patient income based on ZIP code
Under $35,000	21,229	19.1%	421	15.7%	9939	16.1%
$35,000 to $45,000	26,963	24.2%	570	21.3%	14,120	22.9%
More than $45,000	60,024	53.9%	1597	59.5%	36,088	58.5%
Missing	3145	2.8%	94	3.5%	1509	2.4%
Comorbidities
None	40,183	36.1%	842	31.4%	22,800	37.0%
One or more	71,178	63.9%	1840	68.6%	38,856	63.0%
Missing	0	0%	0	0%	0	0%
Hospital teaching status
Rural	6425	5.8%	DS	1%	946	1.5%
Urban nonteaching	34,810	31.3%	991	37%	16,744	27.2%
Urban teaching	69,712	62.6%	1659	62%	42,543	69.0%
Missing	414	0.4%	DS	0%	1424	2.3%
Hospital bed size
Small	9352	8.4%	71	3%	9706	15.7%
Medium	22,681	20.4%	459	17%	10,481	17.0%
Large	78,914	70.9%	2143	80%	40,045	64.0%
Missing	414	0.4%	DS	0%	1424	2.3%

DS=Data suppressed because of insufficient cell size as defined by the Healthcare Cost and Utilization Project Data User Agreement.

ORP=open radical prostatectomy; LRP=laparoscopic radical prostatectomy; RARP=robot-assisted radical prostatectomy.

Fewer than 1% of patients experienced one or more positioning complication (Table 2). Eye complications, including blindness in one eye, visual disturbances, and corneal foreign bodies, were the most common, accounting for 51.1% of total events. The remaining 49% consisted of nerve injuries, rhabdomyolysis, and compartment syndrome. The strongest predictor of a positioning complication was having LRP, with more than three times the likelihood compared with ORP (odds ratio [OR]=3.80, 95% confidence interval [CI]: 1.71, 8.45, P<0.01) (Table 3). Patients who had RARP were not more likely to have a positioning complication develop than patients after ORP, after adjusting for patient and hospital-level predictors (Table 3). Furthermore, patients with one or more comorbidities had more than twice the odds of a positioning complication developing compared with patients who had none (OR=2.17, 95% CI: 1.44, 3.28, P<0.01) (Table 3). In addition, patients with an annual income of more than $35,000 had a lower chance of having a positioning complication compared with those with an annual income of less than $35,000 (P<0.01) (Table 3). Patient race and payer type were not associated with having any positioning complications (Table 3).

Table 2.

Positioning Complications After Radical Prostatectomy

	Robotic (n=61,656)		Nonrobotic (n=114,043)
Complication category	Frequency	%	Frequency	%	P-value
Eye	102	0.17%	255	0.22%	0.0110
362.30: Retinal vascular occlusion	DS		DS
365.22: Acute angle - closure glaucoma	0		DS
368.80: Visual disturbances, unspecified	DS		DS
369.30: Blindness, bilateral	0		DS
369.60: Blindness, unilateral	DS		132
369.80: Visual loss, unilateral	DS		DS
372.00: Acute conjunctivitis	DS		DS
372.73: Conjunctival edema	0		DS
373.00: Blepharitis	DS		DS
376.30: Exopthalmos	0		DS
376.33: Orbital edema	DS		DS
379.92: Swelling of the eye, unspecified	DS		DS
918.20: Superficial injury of the conjunctiva	DS		DS
918.90: Superficial injury of the eye, unspecified	DS		0
930.00: Corneal foreign body	DS		DS
Nerve	100	0.16%	118	0.10%	0.0009
353.00: Brachial plexus lesions	DS		DS
354.10: Other lesion of the median nerve	DS		DS
354.20: Lesion of the ulnar nerve	DS		DS
354.30: Lesion of the radial nerve	DS		DS
355.00: Lesion of the sciatic nerve	DS		DS
355.20: Other lesion of the femoral nerve	DS		DS
355.30: Lesion of the lateral popliteal nerve	DS		DS
955.20: Injury to the ulnar nerve	DS		DS
956.10: Injury to the femoral nerve	DS		DS
957.10: Injury to other specified nerves	DS		DS
957.90: Injury to other nerve, not otherwise specified	DS		DS
Rhabdomyolysis or compartment syndrome	47	0.08%	76	0.07%	0.4911
728.88: Rhabdomyolysis	DS		76
958.90: Compartment syndrome	DS		0
Total	249	0.40%	449	0.39%	0.7391

DS=Data suppressed because of insufficient cell size as defined by the Healthcare Cost and Utilization Project Data User Agreement.

Table 3.

Probability of Incurring a Positioning-Related Complication

Factors	OR	95% CI	P-value
Mean age	1.02	0.99, 1.05	0.2583
Race
White	Reference
Black	1.73	1.09, 2.75	0.0200
Hispanic	0.39	0.10, 1.63	0.1991
Asian Pacific Islander	1.15	0.29, 4.60	0.8414
Native American	1.26	0.62, 2.56	0.5225
Other	0.55	0.15, 2.10	0.3822
Insurance type
Private insurance	Reference
Medicare	0.79	0.49, 1.27	0.3233
Medicaid	0.85	0.26, 2.79	0.7861
Other	0.72	0.28, 1.86	0.4982
Patient income based on ZIP code
Under $35,000	Reference
$35,000 to $45,000	0.46	0.29, 0.73	0.0010
More than $45,000	0.57	0.39, 0.84	0.0041
Comorbidities
None	Reference
One or more	2.17	1.44, 3.28	0.0002
Hospital teaching status
Rural	Reference
Urban nonteaching	1.83	0.67, 5.01	0.2401
Urban teaching	2.10	0.79, 5.55	0.1357
Hospital bed size
Small	Reference
Medium	1.27	0.62, 2.59	0.5153
Large	1.50	0.80, 2.80	0.2100
RP type
Open radical prostatectomy	Reference
Laparoscopic radical prostatectomy	3.80	1.71, 8.45	0.0010
Robot-assisted radical prostatectomy	0.94	0.62, 1.43	0.7830
Annual RP volume
Low volume	Reference
Medium volume	0.83	0.54, 1.27	0.3857
High volume	0.46	0.28, 0.78	0.0040

OR=odds ratio; CI=confidence interval.

The mean inpatient cost of undergoing an ORP, LRP, or RARP was $12,075, $13,802, and $13,088, respectively. Increased inpatient costs, defined as costs at or above the 90th percentile of costs in this sample, were set at $19,696. Having a positioning complication was the primary driver of increased costs (OR=3.85, 95% CI: 2.51, 5.90, P<0.01 vs no positioning complication) (Table 4). Similarly, Medicaid patients had greater odds of incurring increased costs than privately insured patients (OR=1.56, 95% CI: 1.09, 2.23, P<0.02). In addition, patients with higher incomes were more likely to have higher inpatient costs than patients with lower incomes (middle level income OR=1.28, 95% CI: 1.06, 1.55, P<0.01; high level income OR=1.77, 95% CI: 1.39, 2.25, P<0.01).

Table 4.

Probability of Increased Costs

Factors	OR	95% CI	P-value
Mean age	1.02	1.02, 1.02	<0.0001
Positioning complications
One or more	3.85	2.51, 5.90	<0.0001
None	Reference
Race
White	Reference
Black	1.42	1.12, 1.80	0.0036
Hispanic	1.78	1.27, 2.51	0.0009
Asian Pacific Islander	2.12	1.45, 3.09	0.0001
Native American	0.62	0.30, 1.30	0.2086
Other	1.19	0.75, 1.90	0.4570
Insurance type
Private insurance	Reference
Medicare	0.98	0.85, 1.13	0.7852
Medicaid	1.56	1.09, 2.23	0.0158
Other	0.80	0.59, 1.09	0.1655
Patient income based on ZIP code
Under $35,000	Reference
$35,000 to $45,000	1.28	1.06, 1.55	0.0112
More than $45,000	1.77	1.39, 2.25	<0.0001
Comorbidities
None	Reference
One or more	1.34	1.16, 1.55	<0.0001
Hospital teaching status
Rural	Reference
Urban nonteaching	0.62	0.30, 1.28	0.1974
Urban teaching	0.51	0.23, 1.13	0.0980
Hospital bed size
Small	Reference
Medium	0.84	0.35, 2.03	0.7041
Large	1.35	0.61, 2.99	0.4597
RP type
Open RP	Reference
Laparoscopic RP	1.27	0.80, 1.99	0.3108
Robot-assisted RP	1.70	1.23, 2.35	0.0012
Annual RP volume
Low volume	Reference
Medium volume	1.31	0.76, 2.24	0.3289
High volume	0.63	0.33, 1.20	0.1601

OR=odds ratio; CI=confidence interval; RP=radical prostatectomy.

In multivariate logistic regression analysis, robotic procedures were associated with higher inpatient costs compared with open procedures (robotic: OR=1.70, 95% CI: 1.23, 2.35, P<0.01). Compared with open prostatectomy, laparoscopic procedures cost $1695 more and robotic procedures $1344 more (Table 5).

Table 5.

Linear Model Predicting Factors That Influence Inpatient Costs in RP patients, 2008–2009

Factors	Estimate	P-value
Intercept	$7932.22	<0.0001
Age	$38.46	<0.0001
Positioning complications
One or more	$7721.51	<0.0001
None	Reference
Race
White	Reference
Hispanic	$1118.35	<0.0001
Other	$1045.62	<0.0001
Insurance type
Private insurance	Reference
Medicare	−$113.59	0.3287
Medicaid	$723.47	0.0277
Other	−$519.63	0.0099
Patient income based on ZIP code
Under $35,000	Reference
$35,000 to $45,000	$500.39	<0.0001
More than $45,000	$1309.39	<0.0001
Comorbidities
None	Reference
One or more	$837.60	<0.0001
Hospital teaching status
Rural	Reference
Urban nonteaching	−$1039.87	<0.0001
Urban teaching	−$731.61	0.0002
Hospital bed size
Small	Reference
Medium	−$252.68	0.1074
Large	$345.31	0.0092
Robotic procedure
Yes	$1344.12	<0.0001
No	Reference
Laparoscopic procedure
Yes	$1694.69	<0.0001
No	Reference
Annual RP volume
Low volume	Reference
Medium volume	$1653.96	<0.0001
High volume	−$290.71	0.0085

RP=radical prostatectomy.

Prolonged length of stay, at or above the 90th percentile of LOS, was 4 days. The strongest predictor of prolonged LOS was having a positioning complication, with nearly three times the odds of having a prolonged LOS compared with persons who did not have a complication (OR=2.99, 95% CI: 1.91, 4.68, P<0.01) (Table 6). Comorbidities were significantly associated with increased odds of prolonged LOS (OR=1.94, 95% CI: 1.75, 2.14, P<0.01). Furthermore, Medicaid and Medicare patients both had increased odds of prolonged LOS compared with patients with private insurance (Medicare: OR=1.20, 95% CI: 1.08, 1.34, P<0.01; Medicaid OR=1.80, 95% CI: 1.42, 2.28, P<0.01).

Table 6.

Probability of Prolonged Length of Stay

Factors	OR	95% CI	P-value
Mean age	1.02	1.01, 1.03	<0.0001
Positioning complications
One or more	2.99	1.91, 4.68	<0.0001
None	Reference
Race
White	Reference
Black	1.95	1.67, 2.27	<0.0001
Hispanic	1.50	1.20, 1.86	0.0003
Asian Pacific Islander	1.53	1.12, 2.09	0.00071
Native American	1.57	1.03, 2.40	0.0356
Other	1.52	1.03, 2.24	0.0339
Insurance type
Private insurance	Reference
Medicare	1.20	1.08, 1.34	0.0008
Medicaid	1.80	1.42, 2.28	<0.0001
Other	1.08	0.88, 1.32	0.4650
Patient income based on ZIP code
Under $35,000	Reference
$35,000 to $45,000	1.20	1.08, 1.34	0.4688
More than $45,000	1.80	1.42, 2.28	0.1004
Comorbidities
None	Reference
One or more	1.94	1.75, 2.14	<0.0001
Hospital teaching status
Rural	Reference
Urban nonteaching	0.79	0.58, 1.07	0.1204
Urban teaching	0.57	0.43, 0.76	<0.0001
Hospital bed size
Small	Reference
Medium	1.14	0.76, 1.72	0.5332
Large	1.09	0.76, 1.55	0.6501
RP type
Open RP	Reference
Laparoscopic RP	0.76	0.55, 1.05	0.09511
Robot-assisted RP	0.40	0.32, 0.49	<0.0001
Annual RP volume
Low volume	Reference
Medium volume	0.79	0.64, 0.97	0.0242
High volume	0.57	0.43, 0.76	<0.0001

OR=odds ratio; CI=confidence interval; RP=radical prostatectomy.

Higher annual hospital RP volume was associated with a decreased likelihood of prolonged LOS when compared with lower volume facilities (high: OR=0.57, 95% CI: 0.43, 0.76, P<0.01; medium: OR=0.79, 95% CI: 0.64, 0.97, P<0.05). Hospital teaching status reduced the odds of prolonged LOS, with urban teaching facilities having almost 43% and urban nonteaching having 21% decreased odds of prolonged LOS compared with rural hospitals (Table 6).

Robotic procedures were associated with an almost 60% decreased likelihood of prolonged LOS compared with ORP (OR=0.40, 95% CI: 0.32, 0.49, P<0.01). Laparoscopic procedures were not significantly associated with prolonged inpatient LOS (Table 6).

Discussion

This study is one of the first to assess positioning-related complications in a national population-based database. We found a very low incidence of complications relating to the prolonged steep Trendelenburg and lithotomy positioning used during RARP, with no difference in these complications between robotic and ORP. We did find, however, an almost 300% increased odds of a positioning complication from LRP compared with ORP. Our results suggest positioning complications increase both costs and LOS.

We hypothesized that positioning complications would be more common during RARP because of the longer operative time in steep Trendelenburg and low lithotomy positions. The longer operative time has been shown previously, with one single institution study finding associations between positioning complications and longer operative times in robotic urologic surgeries.^17
–19 Our findings were contradictory to our hypothesis, however, which may be because of our inability to adjust for operative time. The longer times in previous studies may be because of the learning curve associated with RARP and surgeon experience with robotics, for which we could also not adjust because the NIS does provide this level of surgical detail.²⁰ More recent studies have cited shorter or equivalent average operative times for RARP compared with LRP.^21
–23

Second, our study indicates that although both RARP and LRP are more expensive than ORP, RARP costs are lower than LRP costs in this database. This is contradictory to previous studies that have indicated that RARP is costlier than both LRP and ORP.^23

–26 These two findings suggest that RARP costs may have declined in the past few years. Possible explanations include shorter operative times from greater surgeon experience, increased dissemination and adoption of the technology, or centralization of RARP to higher-volume facilities, leading to an overall decline in cost per case.^24,27 This study's cost of RARP may theoretically reflect a point at which RARP either is less costly or not significantly different in cost compared with LRP. The cost information in NIS, however, does not include the costs associated with initial purchase and maintenance of the robot, thus possibly presenting an underinflated cost to the patient, thereby biasing our findings to a lower cost. While this study indicates that RARP is associated with higher costs, the robotic procedure was not identified as the primary driver of high costs in our multivariate analysis; the occurrence of positioning complications and presence of comorbidities are the strongest predictors of increased inpatient costs when adjusting for hospital factors, patient factors, and positioning complications (Table 4).

Third, RARP is associated with shorter hospital stays compared with LRP and ORP, a finding that is well-supported in the literature.^24,28 While laparoscopic procedures were not associated with increased LOS, the mean LOS for laparoscopic patients was shorter than ORP, but slightly longer than RARP, further supporting the fact that patients undergoing RARP recover more quickly. Patients with positioning complications experienced almost three times the odds of incurring a longer LOS compared with patients with no position-related complications, suggesting that akin to increased costs, they are one of the primary drivers of increased LOS. Complications, including positioning ones, are known to be associated with increased LOS because patients often need additional recovery time in an inpatient setting.^29
–31

Finally, ocular complications during nonocular surgery have been well described, usually reported in association with prolonged prone or Trendelenburg positioning.^32

–36 Risk factors associated with vision loss include male sex, obesity, prolonged anesthesia time, duration of surgery, intraoperative blood loss, pre- or intraoperative anemia, and colloid as percent of nonblood replacement.^32,33,35,36 Etiologies of perioperative vision loss include ischemic optic neuropathy, retinal vascular occlusion, and cortical blindness, all of which can have profound and permanent visual consequences.³²

In our study, ocular complications were more common in nonrobotic (0.22%) compared with robot-assisted prostatectomy (0.17%, P=0.110). When comparing visually threatening ocular complications, this difference widened, with nonrobotic vs robot-assisted complication rates of 0.15% and 0.07%, respectively. In contrast, nonvisually threatening ocular complications were more common in robot-assisted (0.10%) compared with nonrobotic prostatectomy (0.07%). Delineating ocular complications into vision threatening and nonvision threatening serves to highlight those complications likely to cause permanent damage to the visual system. It also allows us to consider separately those complications previously reported in association with surgical positioning. Some of these eye-related complications could have been because of improper ocular protection during general anesthesia and not resultant from the RARP itself.

Despite steep Trendelenburg positioning, vision-threatening ocular complications were more common in nonrobotic prostatectomy. Inability to control for the risk factors listed above limits our ability to identify which, if any, were associated with the observed increased risk. The large national sample size, however, increases the generalizability of this finding and is therefore meaningful.

Other limitations of the study include the use of administrative claims data, which may lack detailed clinical information (i.e., operative time) or consist of ICD-9CM miscoding errors. Furthermore, complications have been shown in the literature to be underreported in the final discharge disposition, which may mean that our study potentially reported an underestimate of these positioning complications in this population.^37,38 This should not alter the generalizability of our results, but as with all retrospective analyses, we are only able to determine associations between RARP and positioning complications, and not causation.

Another limitation was the lack of certain patient, provider, and hospital information, such as tumor characteristics, surgeon volume for the entire sample, surgeon learning curve, operative time, and experience level of the staff.³⁹ Similarly, NIS is limited to the inpatient hospital setting, which does not permit the investigation of outpatient complications. In addition, NIS does not include professional fees, which leads to an underestimation of the total hospital costs.⁴⁰

Conclusions

This study analyzes positioning complications in a national dataset for a major cancer operation that is undergoing diffusion and expansion. We found no significant difference in the incidence of positioning complications between RARP and ORP. Because NIS provides national estimates, the conclusions regarding predictors and the impact of steep Trendelenburg positioning-related complications may be applicable to a broad range of patients undergoing RP. Although not great in number, these complications significantly impact total inpatient hospital costs and LOS. Future population-based studies are needed to monitor these positioning complications in light of the increasing use of robotic minimally invasive procedures in urology. In addition, increased use of RARP may assist in decreasing positioning complications and continue to improve outcomes for prostate cancer patients.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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