Does the Level of Assistant Experience Impact Operative Outcomes for Robot-Assisted Partial Nephrectomy?

Abstract

Purpose:

A skilled assistant surgeon is presumed necessary during robot-assisted partial nephrectomy (RAPN) to minimize warm ischemia time (WIT) and to facilitate complex renorrhaphy. Studies observing impact of resident participation have focused on robotic prostatectomies, showing no impact on core surgical outcomes. Herein, we evaluated the level of experience of the bedside assistant and its impact on perioperative outcomes in RAPN.

Materials and Methods:

All RAPN cases in our healthcare system from January 2011 to December 2013 were retrospectively reviewed. The cases were divided into teaching and nonteaching hospitals. There were 18 fellowship-trained attending surgeons. At teaching hospitals, surgeries were performed by an attending physician and postgraduate year (PGY)-2 or PGY-3 resident at bedside; at nonteaching hospitals, surgeries were performed by two attending surgeons. We compared age, gender, body mass index, Charlson comorbidity index, operative difficulty by R.E.N.A.L. nephrometry score, and operative outcomes (WIT, estimated blood loss, operative time (OT), positive margin rate, length of stay (LOS), postoperative glomerular filtration rate, and readmission rate).

Results:

Of the 170 patients captured, 162 had R.E.N.A.L. nephrometry score and WIT: 112 from teaching hospitals and 50 from nonteaching hospitals. Patient characteristics were equivalent between both cohorts with the exception of the R.E.N.A.L. score, which was higher (6.3 vs 5.7, p = 0.046) in the teaching hospitals cohort. Regarding operative outcomes, we noted an overall increase in LOS by 1 day (p = 0.001) and OT by 16 minutes (p = 0.011) in the teaching hospitals.

Conclusion:

We observed that increased LOS was the only clinically relevant measure negatively impacted by resident physician involvement during RAPN.

Introduction

Partial nephrectomy is now the standard for the treatment of T1a renal-cell carcinoma. It achieves similar oncologic outcomes as radical nephrectomy while preserving functional renal parenchyma.¹ In recent years, robot-assisted partial nephrectomy (RAPN) has been adopted as the preferred technique at high-volume centers.² Its rapid adoption has often necessitated two experienced surgeons to be present, because the console surgeon is situated remotely from the bedside assistant. The requirement of a bedside assistant to necessitate moderate to advanced laparoscopic experience was previously shown for robot-assisted radical prostatectomy (RARP).³ Thus, one might assume that a demanding skill set is of even greater importance with RAPN, particularly during hilar vessel clamping, when some of the most complex aspects of the procedure are performed under warm ischemia time (WIT). Precise and accurate surgical assistance is not only critical for minimizing WIT for preservation of optimal postoperative renal function but also to allow for maximal observation during tumor resection and assuring gross negative margins. In addition, during WIT, renorrhaphy is performed, requiring experienced assistance to provide observation to ensure a water tight and hemostatic closure.

The impact of experience level of the assistant in RARP has been studied, particularly analyzing the effect of resident participation. For example, at our institution, we studied 162 RARP cases, in which trainees (residents and/or fellows) participated, demonstrating no negative impact on positive margin rate, slightly increased estimated blood loss (EBL) but no difference in transfusion rates, and slightly longer operative time (OT).⁴

Significant attention has been previously dedicated toward developing and validating training curricula with simulators as well as live operative experience.^{5

–21} Herein, we evaluated whether the level of experience of the bedside assistant has an effect on several operative and postoperative metrics in RAPN.

Materials and Methods

After obtaining approval from our institutional review board, we retrospectively reviewed all RAPN patients at Kaiser Permanente Southern California (KPSC) from January 2011 through December 2013. Age, gender, body mass index (BMI), Charlson comorbidity index (CCI), WIT, EBL, OT (defined as incision to close in minutes), length of stay (LOS), 90-day readmission rate, change in estimated glomerular filtration rate (eGFR), and positive margin rates were recorded through retrospective chart review for all patients. R.E.N.A.L. nephrometry score²² was calculated by reviewing the preoperative CT or MRI by four urologists (G.A.A., P.S.K., P.A.E., and P.B.) who did not participate in the operations. There were three robots within our healthcare system: two robots at teaching hospitals and one at a nonteaching hospital. There were 18 attending robotic surgeons, all of whom had robotic training and had performed at least 100 robotic cases. All cases were operated on by these robotically credentialed attending physicians at one of the three hospitals. These cases were stratified into teaching and nonteaching hospitals.

At the nonteaching hospitals, all cases were operated on by two attending surgeons: one as the console surgeon and the other as the bedside assistant. Both the console surgeon and bedside assistant were robotically credentialed attending physicians. At the teaching hospitals, all cases involved one attending physician and one postgraduate year (PGY)-6 resident at a single robot console and a PGY-2 or PGY-3 resident at the bedside as an assistant. At the time of our study, the PGY-6 residents had prior experience with laparoscopic surgery as well as bedside assist in both RARP and RAPN since the beginning of their PGY-5. The PGY-6 resident would start with exposing Gerota's fascia and the renal mass, gradually advancing to more technically advanced portions of the RAPN such as dissection of the renal hilum, the renorrhaphy, and finally excision of the mass under WIT at the discretion of the supervising attending. The PGY-2/PGY-3 residents have limited prior experience in laparoscopy, mostly with laparoscopic appendectomies and cholecystectomies during their general surgery internship year, with their laparoscopic training in urology as robotic bedside assistant. We compared the patient preoperative characteristics between the teaching and nonteaching hospitals (age at diagnosis, sex, R.E.N.A.L. nephrometry score, BMI, and CCI).

The two cohorts were then matched by R.E.N.A.L. nephrometry score. The median WIT, EBL, OT, LOS, change in eGFR at 90 days postoperatively, 90-day readmission rate, and positive margin rate were compared using the Wilcoxon two-sample test, Fisher's exact test, and chi-squared test.

Results

Of the 170 patients who underwent RAPN during this study period, 162 had a calculated R.E.N.A.L. nephrometry score and recorded WIT. There were eight cases without data and were excluded from our analysis. There were 112 total cases from teaching hospitals and 50 from nonteaching hospitals. The mean R.E.N.A.L. nephrometry score was significantly higher for teaching hospitals than for the nonteaching hospitals (6.3 vs 5.7, p = 0.046). There was no significant difference between baseline preoperative characteristics between cohorts (Table 1).

Table 1.

Preoperative Patient Characteristics

	Teaching hospital (N = 112)	Nonteaching hospital (N = 50)	Total (N = 162)	p
Age at diagnosis				0.123
Mean (SD)	55.3 (13.44)	58.7 (12.0)	56.4 (13.07)
Sex (%)				0.321
Male	67 (59.8)	34 (68)	101 (62.3)
R.E.N.A.L. nephrometry score				0.046
Mean (SD)	6.3 (1.90)	5.7 (1.74)	6.1 (1.87)
BMI				0.737
Mean (SD)	31.1 (6.31)	30.7 (5.55)	31.0 (6.07)
Charlson score (%)				0.936
0	47 (42)	20 (40)	67 (41.4)
1	31 (27.7)	16 (32)	47 (29)
2	13 (11.6)	6 (12)	19 (11.7)
3	13 (11.6)	6 (12)	19 (11.7)
4	6 (5.4)	2 (4)	8 (4.9)
5	2 (1.8)	0 (0)	2 (1.2)

BMI = body mass index.

The EBL was only statistically different for cases with a R.E.N.A.L. nephrometry score of 4 (teaching hospitals = 70 mL; nonteaching hospitals = 200 mL, p = 0.036). Nevertheless, the EBL of the entire cohort did not differ significantly between the two cohorts (135 mL vs 150 mL, respectively, p = 0.573). The LOS was statistically longer by at least 1 day in the teaching hospitals vs the nonteaching hospitals in all nephrometry score categories and the total cohort (Table 2). The total OT, but not WIT, was marginally longer in the teaching hospitals when the entire cohort was analyzed (229 minutes vs 213 minutes, respectively, p = 0.011). Finally, there was a trend toward a lower positive margin rate in teaching hospitals than in the nonteaching hospitals (3.6% vs 10%, p = 0.079) (Table 2).

Table 2.

Comparison of Select Intraoperative and Postoperative Outcomes for Robot-Assisted Partial Nephrectomy Patients at Teaching vs Nonteaching Hospitals Separated by Preoperative R.E.N.A.L Nephrometry Scores

	Teaching hospital (N = 112)		Nonteaching hospital (N = 50)
	n	Median	n	Median	p
Warm ischemic time
4	24	18.0	14	20.5	0.439
5	19	21.0	8	18.0	0.456
6	25	21.0	5	15.0	0.099
7	12	21.5	6	22.0	1.000
8, 9, 10, 11	30	26.5	3	26.0	0.825
Total	110	21.0	36	20.5	0.276
EBL
4	24	70.0	16	200.0	0.036
5	20	100.0	8	50.0	0.105
6	25	100.0	9	100.0	0.905
7	12	150.0	5	100.0	0.957
8, 9, 10, 11	31	200.0	7	250.0	0.595
Total	112	135.0	45	150.0	0.573
Length of stay
4	24	3.0	16	2.0	0.003
5	20	4.0	9	2.0	0.001
6	25	3.0	8	2.5	0.029
7	12	3.5	6	2.0	0.017
8, 9, 10, 11	31	3.0	7	2.0	0.001
Total	112	3.0	46	2.0	0.001
Operative time (minutes)
4	24	212.5	16	214.0	0.989
5	20	213.0	9	204.0	0.211
6	25	228.0	8	213.0	0.172
7	11	229.0	6	213.0	0.393
8, 9, 10, 11	31	258.0	7	225.0	0.105
Total	111	229.0	46	213.0	0.011
Change in eGFR
4	23	−1.40	16	−2.15	0.896
5	18	−0.86	9	−5.52	0.366
6	25	−4.99	10	−6.36	0.898
7	12	0.00	5	−6.30	0.914
8, 9, 10, 11	29	−4.62	6	−7.93	0.742
Total	107	−4.50	46	−5.46	0.690

90-day readmission	n	readmit	%	n	Readmit	%	p
4	24	3	12.5	17	2	11.8	1.000
5	20	1	5.0	9	1	11.1	0.532
6	25	1	4.0	11	4	36.4	0.023
7	12	0	0.0	6	1	16.7	0.333
8, 9, 10, 11	31	4	12.9	7	1	14.29	1.000
Total	112	9	8.04	50	9	18.00	0.062
Positive margin rate (%)		4 (3.6)			5 (10)		0.079

EBL = estimated blood loss; eGFR = estimated glomerular filtration rate.

Discussion

Robotic surgery presents a new paradigm in surgical workflow. Although traditional open surgery allows an experienced surgeon to operate together with an assistant, the robotic platform necessitates the physical separation of the console surgeon and the assistant surgeon. Furthermore, the two surgeons have different surgical exposures: console surgeon has a three-dimensional view with wristed movements, whereas the assistant surgeon has a two-dimensional view with rigid instruments. The impact of this change in the literature has mostly focused on resident education, validation of training programs and simulators, or comparison of perioperative measures and outcomes between cases involving residents and a historical cohort.^{4

–21} Bedaiwy et al compared an attending-only cohort with a cohort with resident involvement for robot-assisted sacrocoplopexy¹⁸ and were not able to demonstrate any appreciable difference between operative measures or patient outcomes. Wang and colleagues compared lymph node counts from RARP and robot-assisted pelvic lymph node dissections for prostate cancer between academic and community hospitals¹⁹ and demonstrated higher lymph node counts in academic hospitals vs all community hospitals—which included high-volume centers. Moreover, Lee and colleagues demonstrated that in their cohort of RARPs,²⁰ the only measure that was significantly different between the attending-only cohort and training cohort was a longer OT—with EBL, positive margin rate, LOS, and long-term functional outcomes being equivalent. Finally, Padavano et al reviewed their operative and patient outcomes for 153 RARPs at their teaching community hospitals²¹ and found them to be comparable with academic university programs. The degree of resident involvement or the structures of the operative teams in these studies were not specifically addressed.

Our study sought to determine what, if any, influence the experience of the assistant has on select perioperative and postoperative measures for patients who underwent RAPN in our healthcare system. One of the challenges with comparing any surgical cohort is the heterogeneity of the human anatomy, which could introduce bias. R.E.N.A.L. nephrometry score presents a unique opportunity to adjust for any variations in the surgical anatomy, which has previously been validated.²² To our knowledge, there have been no previous studies demonstrating the effect of a resident physician on RAPN adjusted for nephrometry scores.

We observed that only LOS and OT were associated with resident physicians at the robotic console and/or at bedside under the supervision of an attending surgeon for RAPN. There was no negative impact on WIT, EBL, change in eGFR at 90 days postoperatively, or positive margin rate. Importantly, we have shown that resident involvement during WIT, the most critical portion of the surgery that requires complex surgical steps under time pressure, showed no difference compared with a cohort with attending physicians only. Similar to what has been reported previously for RARP, the OT and LOS were longer in the teaching hospital group. Whether these findings are distinctly attributable to resident involvement is not known. Although surgical teaching can lengthen the OT, we attribute this also to not using a dual teaching console, thereby requiring the attending surgeon to frequently switch with the PGY-6 resident at the console. Furthermore, we do not consider a small increase in OT with no difference in WIT as clinically significant. Finally, we attribute the small disparity in LOS to be secondary to clinical pathway structures established at these centers, but further analysis is warranted.

There are several limitations to our study. The retrospective nature of this study has its inherent weaknesses associated with this design. It is also limited by the analysis of a large cohort of heterogeneous attending and resident surgeon groups. All attending surgeons have received specialized training in robotic surgery and have performed at a minimum of 100 robotic surgeries before the start of our study. It is presumed that all attending surgeons included in this study operated evenly at all three hospitals, with the only variable being the presence of resident physicians in the teaching hospitals. We believe this may reflect more of a real clinical scenario, where a robotic surgery program involves numerous surgeons and assistants. We also acknowledge that we could neither adjust nor specify which steps of the surgery the PGY-6 resident at the console performed during each RAPN at the teaching hospitals. Nevertheless, it is the philosophy and tradition of our teaching program that the PGY-6 resident performs at least 50% of the critical steps of all major cases. Finally, we did not account for the possibility of differences in robotic ancillary staff teams among the hospitals and their postoperative care clinical workflows. Nonetheless, we believe this is the first study demonstrating no clinically significant negative effect of resident involvement in RAPN, a highly complex robotic surgery, when adjusting for nephrometry scores. At nonteaching facilities, midlevel providers such as physician assistants and nurse practitioners may be trained to assist during RAPN, thereby increasing utilization of attending surgeons and decreasing cost. Comparing the attending surgeons' and resident surgeons' hourly salaries ($167 vs $18)^23,24 over a typical robotic partial nephrectomy (∼4 hours) yields a difference of $596 per case. This is without taking into consideration the additional earning potential of the attending urologist not acting as bedside assistant.

Conclusion

RAPN with resident involvement had no effect on WIT and EBL when adjusted for nephrometry scores. The OT and LOS were slightly longer. The findings of this study may help training and nontraining robotic surgical programs alike better assess and utilize their resources.

Footnotes

Author Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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