Do Illuminated Foot Pedals Improve the Speed and Accuracy of Pedal Activation During Endoscopic Procedures?

Abstract

Purpose:

Endourologic procedures such as percutaneous nephrolithotomy (PCNL) employ the use of foot pedals in low-light operating room (OR) settings. These pedals can be especially difficult to locate or distinguish when several pedals are present during a single operation. Improper instrument activation in the OR has led to serious complications ranging from unintentional electrocautery to patient burns and even an intraoperative explosion. This study evaluates the impact of color-coded illumination on speed and efficiency of foot pedal activation.

Materials and Methods:

During a simulated PCNL procedure, the foot pedals for a C-arm, laser, and ultrasonic lithotripter (USL) were placed in random positions. Ten participants performed pedal activation in a randomized sequence. Objective outcomes included time to instrument activation, number of attempted pedal presses, number of incomplete pedal presses, and number of incorrect pedal presses. Subjective preferences for pedal illumination were also determined. Data were analyzed using Mann–Whitney U, Wilcoxon signed-rank, and Chi-square tests with p < 0.05 indicating statistical significance.

Results:

Illuminated foot pedals were associated with decreases in the average activation time for all instruments collectively (3.95 seconds vs 6.49 seconds; p = 0.017) and individually (C-arm: 3.07 seconds vs 4.21 seconds; p = 0.006; laser: 13.04 seconds vs 15.18 seconds; p < 0.001; USL: 3.28 seconds vs 4.91 seconds; p < 0.001) compared with nonilluminated pedals. Illuminated pedals were associated with fewer attempted pedal presses (33.5 vs 39.5; p = 0.007) and incomplete pedal presses (1.5 vs 8.5; p = 0.002). The number of incorrect pedal presses decreased with illumination, but this did not reach statistical significance (0 vs 0.5; p = 0.08). Participants reported that illumination simplified pedal activation and recommended its use (p < 0.01).

Conclusion:

Color-coded illumination improved the speed and efficiency of foot pedal activation during simulated PCNL. Participants subjectively preferred using illuminated foot pedals for endourologic procedures and felt that they improved safety and efficiency.

Introduction

Foot pedals are widely employed during urologic procedures such as percutaneous nephrolithotomy (PCNL), ureteroscopic laser lithotripsy, and various transurethral procedures. Although foot pedals allow hands-free instrument activation, their utilization is associated with limitations and potential risks. In a survey of 241 urologists, over 40% of the respondents were not content with the conventional diathermic or ultrasonic foot pedals. Reasons included frequently losing contact with the foot pedal, the need to look down at the pedal, and pressing the wrong pedal unintentionally.¹ Problems with instrument activation have been associated with complications in nonurologic procedures as well, such as tubal ligation and cranial burr hole placement.^2,3 The low-light operating room (OR) settings associated with many endoscopic procedures, overhanging drapes, and the multitude of wires and tubing on the floor add additional complexity to correct foot pedal activation.

Equipment-related errors are common and previous studies have proposed a comprehensive assessment of their effect on surgical performance.^4
–6 Various complications can result from improper instrument activation, including accidental cautery to unintended structures and even patient burns.^3,7,8 Furthermore, catastrophic events, such as fires and fatal intraoperative explosions, have been reported.² A limited number of studies have attempted to improve the ease of operation and ergonomic comfort of foot pedals by introducing completely new designs.^9,10 However, these new designs require modifications of surgeon practice patterns, take time to develop familiarity, and require hospitals to purchase new systems. A simpler and potentially more effective method to improve efficiency in pedal activation could be through pedal illumination. The effects of illumination on speed and accuracy of pedal activation have not been previously evaluated. The purpose of this study was to perform a prospective, randomized, controlled trial to quantitatively evaluate the impact of color-coded illumination upon foot pedal activation in a simulated OR setting.

Materials and Methods

The experimental setup was similar to that of a clinical PCNL. The equipment routinely activated through foot pedal depression was collected. This included a GE OEC 9900 portable C-arm (General Electric, Fairfield, CT), Dornier Medilas H Solvo holmium laser lithotripsy power source with a 270 μm laser fiber (Dornier MedTech, Munich, Germany), and a Storz Calcuson ultrasonic generator with a 3.0 mm oscillating tip ultrasonic lithotripter (USL) probe (Karl Storz, Tuttlingen, Germany). The foot pedals of these machines were placed in three different positions underneath a draped operating table (Fig. 1). The overhead lights were turned off to recreate the conventional low-light setting employed during endourologic procedures (Fig. 2). In the control setup, foot pedals were covered with waterproof plastic bags that are routinely used in our institution to insulate the pedals against fluid damage. For the experimental setup, colored glow sticks were attached to the distal and lateral margins of the foot pedals using plastic tape and each pedal was then covered with a waterproof bag (Fig. 3). The instruments were color coded as follows: orange for the C-arm, yellow for the laser, and green for the USL. The cost of a 50-count package of glow sticks was $21.59, including sales tax.

FIG. 1.

Layout of pedal positions underneath the operating table during a simulated PCNL. Each instrument pedal (C-arm, laser, and USL) was randomized to a different position for each trial. Glow sticks were attached to the distal and lateral margins of each pedal for the experimental condition. USL = ultrasonic lithotripter.

FIG. 2.

Operating room with (A) room lights on and (B) low-light setting used during the experiment. Illuminated foot pedals are in place beneath the draped table.

FIG. 3.

Color-coded pedal illumination for (A) C-arm in orange, (B) laser in yellow, and (C) USL in green.

Five attending and five fellow/resident physicians from the Urology Department in a single academic institution participated in the study. Each participant performed the experiment with and without foot pedal illumination. Each subject was instructed to stand in front of the draped table and to only look down at the foot pedals when verbally prompted to activate the foot pedal of an instrument. C-arm activation was considered successful at the time a single fluoroscopic image was captured. Laser activation was considered successful after the subject activated the laser lithotripter, fired the laser once, and then returned the laser to standby mode. The foot pedal for this instrument allowed for independent laser activation and deactivation by the surgeon. Successful USL activation was measured once the ultrasound probe was triggered. The order of illuminated vs control lighting conditions, the sequence of instruments activated, and the orientation and location of each pedal were randomized for each subject. In addition, the orientation and location of each pedal was changed after each activation to avoid recall bias. This was also intended to simulate the entropy that is incorporated into the system during an actual case when pedals slide on the floor and the location of each respective pedal may not always be constant.

The recorded endpoints included time from verbal prompt to activation, number of attempted pedal presses, number of incomplete pedal presses, and number of incorrect pedal presses. An attempted pedal press was defined as an attempt to step on the correct pedal but the pedal was missed. An incomplete pedal press was defined as depression of the correct pedal without instrument activation. An incorrect pedal press was defined as depression and/or activation of the wrong foot pedal. We then used these endpoints to quantify improvements in accuracy and efficiency. Accuracy was defined as the complete activation of the appropriate instrument when prompted. An improvement in efficiency was defined as an improvement in activation time.

A total of 360 instrument activations were conducted with 18 prompts for each of the 10 participants with and without color-coded pedal illumination. The participants were directed to activate the pedal by voice command. Pedal activation times were recorded by stopwatch. At the completion of the experiment, each participant completed a survey assessing his or her preference for conventional vs illuminated pedals (Appendix 1).

To estimate the time saved during clinical cases, foot pedal activation during 10 ureteroscopic laser lithotripsies and 10 PCNLs were prospectively determined at a tertiary academic institution. Potential cost savings were estimated by multiplying the time saved in minutes by the industry standard of $66 per minute of OR costs.¹¹ Data were analyzed using Mann–Whitney U, Wilcoxon signed-rank, and Chi-square tests with p < 0.05 indicating statistical significance.

Results

Foot pedal illumination decreased the time of activation for all instruments collectively and individually (Table 1). Trials with illuminated pedals demonstrated a 39.1% decrease in the average activation time for all instruments combined (median 3.95 seconds vs 6.49 seconds; p = 0.017). Individually, illumination decreased pedal activation time for the C-arm by 27.1% (median 3.07 seconds vs 4.21 seconds; p = 0.006), the laser by 14.1% (median 13.04 seconds vs 15.18 seconds; p < 0.001), and the USL by 33.2% (median 3.28 seconds vs 4.91 seconds; p < 0.001). Median activation times are demonstrated in Figure 4. Illuminated pedals were also associated with fewer attempted pedal presses (median 33.5 vs 39.5; p = 0.007) and incomplete pedal presses (median 1.5 vs 8.5; p = 0.002). The number of incorrect pedal presses decreased with illumination, but this did not reach statistical significance (median 0 vs 0.5; p = 0.08) (Table 1). However, it should be noted that there were no incorrect pedal presses with illumination, whereas five participants stepped on the incorrect pedal during the control setup without illumination.

FIG. 4.

Median activation times with and without pedal illumination of each instrument employed in the simulated PCNL (p < 0.01 for all). PCNL = percutaneous nephrolithotomy.

Table 1.

Primary Outcome Results Comparing Performance With and Without Illumination

	Control	Illumination	p
Activation time
Average	6.49 seconds (IQR 10.47)	3.95 seconds (IQR 8.42)	0.017
C-arm	4.21 seconds (IQR 3.01)	3.07 seconds (IQR 1.34)	0.006
Laser	15.18 seconds (IQR 5.41)	13.04 seconds (IQR 3.53)	0.00001
USL	4.91 seconds (IQR 3.51)	3.28 seconds (IQR 3.51)	0.00001
Attempted pedal presses	39.5 (IQR 3.75)	33.5 (IQR 4.00)	0.007
Incomplete pedal presses	8.5 (IQR 3.5)	1.5 (IQR 2.8)	0.002
Incorrect pedal presses	0.5 (IQR 1.0)	0 (IQR 0)	0.08

Activation times and pedal presses are presented as median values (IQR).

Boldface indicates significant reduction in average and individual activation times, attempted pedal presses, and incomplete pedal presses.

IQR = interquartile range; USL = ultrasonic lithotripter.

In the subjective survey of participant preferences (Appendix 1), all participants (100%) reported that illumination made the pedals easier to use and would recommend their use in regular practice (p < 0.01). Nine of the 10 (90%) participants felt they made fewer mistakes, whereas one participant felt that illumination did not help or hinder the surgeon (p < 0.01). Furthermore, 9 out of 10 (90%) felt that foot pedal illumination improved their efficiency, whereas one participant felt that illumination neither improved nor impaired efficiency (p < 0.01). Finally, 9 out of 10 (90%) felt a greater sense of safety when activating foot pedals and one participant felt that pedal illumination's effect on safety improvement was neutral (p < 0.01). The subjective ratings by participants are summarized in Table 2.

Table 2.

Results from the Questionnaire Given After Each Participant Completed Their Trial

	Yes	Neutral	Significance (p)
Made fewer mistakes	9	1	<0.01
Increased efficiency	9	1	<0.01
Increased safety	9	1	<0.01
Makes pedals easier to use	10	0	<0.01
Would recommend in regular practice	10	0	<0.01

In an observational review of 10 ureteroscopic cases and 10 PCNLs at our institution, there was a mean of 21.1 C-arm activations and 134.0 laser activations during ureteroscopic cases and a mean of 80.7 C-arm activations, 65.3 laser activations, and 45.4 USL activations during PCNL (Table 3). Multiplying the potential time savings (5.18 minutes ureteroscopy and 4.99 minutes PCNL) by $66 per minute¹¹ resulted in a potential cost savings of $341.88 and $329.34 for the average ureteroscopic and PCNL case, respectively (Table 4).

Table 3.

Descriptive Data of Observational Review of Number of Foot Pedal Activations During 10 Ureteroscopic and 10 Percutaneous Nephrolithotomy Surgeries

	C-arm	Laser	USL
Mean (SD) presses for URS cases	21.1 (26.3)	134 (94.7)	—
Mean (SD) presses for PCNL cases	80.7 (48.6)	65.3 (38.0)	45.4 (38.6)

Data are presented as mean listed with standard deviation (SD).

PCNL = percutaneous nephrolithotomy; URS = ureteroscopic.

Table 4.

Potential Cost Savings with Foot Pedal Illumination for the Mean Number of Activations for 10 Ureteroscopic and 10 Percutaneous Nephrolithotomy Surgeries

	C-arm		Laser		USL
	Steps	Time saved	Steps	Time saved	Steps	Time saved	Total time saved (seconds)	Total time saved (min)	Cost savings
URS	21.1	24.1	134	286.7	—	—	310.8	5.18	$341.88
PCNL	80.7	92.0	62.3	133.2	45.4	74.0	299.2	4.99	$329.34

Time saved was calculated based upon study findings (1.14 seconds for the C-arm, 2.14 seconds for the laser, 1.63 seconds for the USL) and cost savings were calculated based upon a cost of $66 per minute in the OR.¹¹

Of the three colors used in this study, four participants indicated that green made the pedal easiest to identify, but two participants did not report an advantage for any color. Two participants reported a preference for orange and yellow, and four participants preferred colors not employed in the study, including red and blue. Three participants did not report a color preference for any pedal.

Discussion

During intricate surgical procedures, inappropriate pedal activation may lead to serious complications. Van Veelen et al. reported that 75% of the surgeons surveyed occasionally hit the wrong pedal switch during an operation.¹⁰ There have been reports of surgical complications, both nonfatal and fatal that have arisen from inadvertent foot pedal activation.^2,7,8 For example, activation of the coagulation pedal instead of the cutting pedal near the ureteral orifice during a transurethral bladder tumor resection can result in ureteral strictures.⁷ Furthermore, the ignition of OR fires is another potentially catastrophic event that has occurred with improper instrument activation.^3,8,12 In addition, there have been case reports in which OR fires and fatal intraoperative explosions were attributed to problems with electrocautery foot pedal activation.^2,3 These examples highlight the importance of accurate and efficient foot pedal activation. Although adverse events may not always arise from incorrect instrument activation, precise pedal activation could improve OR safety and efficiency.

Data in this study demonstrate that intraoperative pedal illumination could reduce inadvertent pedal activation and provide another form of safety in the OR. Although the benefit of better visualization seems intuitive, this study objectively demonstrates that pedal illumination can improve efficiency. The use of illuminated foot pedals improved efficiency through a statistically significant reduction in average activation time for all instruments. Foot pedal illumination also improved instrument activation through a significant reduction in attempted and incomplete pedal presses. Although statistical significance could not be established for a reduction in the number of incorrect pedal presses, there were zero incorrect pedal presses with illumination during our study.

Intraoperative distraction has been shown in observational studies to be associated with lower safety checklist scores. Several studies have highlighted equipment-related interruption as a frequent cause of intraoperative distraction.^13,14 Distractions and poor communication have been linked to increased surgical errors, operative time, and higher perceived workload for physicians.^{15

–22} For example, a surgeon's focus can be taken away from the surgical field during PCNL while looking for the foot pedal in the dark space below the table. It is possible that the surgeon could inadvertently shift their hand position resulting in torque on the sheath. This could result in damage to the kidney or collecting system. Our data show that foot pedal illumination decreases the time a surgeon is distracted from the surgical field by decreasing the time required to activate a foot pedal while also increasing the accuracy of activation. Therefore, foot pedal illumination streamlines OR tasks and minimizes interruptions, which could improve patient safety and minimize distractions and stress for the surgeon.

Minimizing distractions and optimizing surgical devices can also decrease OR times and subsequently reduce costs. Hospital costs for the OR have been estimated to be $66 per minute in the United States.¹¹ The decrease in activation time by 1.14 seconds for the C-arm, 2.14 seconds for the laser, and 1.63 seconds for the USL with illuminated foot pedals represents the time saved for each pedal activation. Based upon the time saved in our study and the review of the cases at our institution, foot pedal illumination could potentially save ∼5 minutes and over $300 dollars for complex stone cases seen in an academic institution. In addition to time spent activating a pedal, delays in the transition between relocating pedal position and returning to the task at hand may further impact total OR time. Also, the surgeon's attention being removed from the case could result in potential collecting system injuries, increased bleeding, additional laboratory and hematologic costs (e.g., transfusions and hemostatic agents), and much greater costs associated with longer hospital stays. This suggests that the use of illuminated foot pedals may be a way to reduce OR time and complications, which would ultimately reduce the cost of surgery.

Illumination on surgical instruments has been shown to improve surgical outcomes in other disciplines as well. It has been employed on retractors as well as novel instruments such as those developed for robot-assisted laparoscopic hysterectomy.^23,24 Illumination was found to improve both the accuracy, with which the instrument was used, and the efficiency, with which the procedure was completed. Attaching lights to enhance the visibility of foot pedals provides a cost-effective means of improving conventional pedals that does not require a change in technique or purchasing new capital equipment. Although this study utilized inexpensive disposable glow sticks as prototype lighting, the development of a reusable light source could potentially lower costs further. This study's use of foot pedal illumination illustrates a new approach to improving the use of foot pedals.

To assess the effectiveness of the illuminated foot pedal in the OR, this study included both objective and subjective measurements. Survey results from the participants after operating pedals under experimental conditions were positive, with all participants recommending their use in regular practice. However, the role of specific color coding is more difficult to interpret. Participants' preferences to specific colors for each instrument were widely variable and three participants reported preference of colors not used in the study, such as red and blue. The same participants also did not prefer using orange due to its similarity with yellow. This implies that using contrasting colors such as red, blue, and yellow may provide greater differentiation.

Despite significant results, there are limitations in this study. First, even with enhanced visibility of the pedals, surgeons would still have to briefly look away from the surgical field to see the pedals before activating them. An ideal mechanism would allow the surgeon to accurately activate the instrument without looking at the pedals at all.^10,25 This would, however, represent a major departure from current surgical technique and would therefore be less likely to be accepted by surgeons. Furthermore, an additional limitation is that this study was conducted in the OR using simulated PCNL conditions as a benchtop study. A prospective study during clinical cases might better recreate all of the variables that are encountered in the OR. However, this benchtop model allowed us to control and measure outcomes in a manner that would not be possible in an actual surgery. Although faster instrument activation time in this study may reflect increased ease in locating the illuminated pedals, future studies may benefit from using other endpoints that directly assess improvement in surgeon accuracy and efficiency. Decreases in the length of time to locate the pedal or to return to a primary task may provide additional ways to evaluate the benefit of pedal illumination.

Conclusion

This study suggests that illumination of foot pedals could improve speed and efficiency, lower costs, and decrease incorrect instrument pedal activations to zero. Furthermore, the participants in this study reported high satisfaction with foot pedal illumination. This is a cost-effective method to improve both efficiency and patient safety in the OR while also reducing costs associated with surgical time.

Footnotes

Author Disclosure Statement

Dr. D. Duane Baldwin is consultant for Bard, consultant for Olympus, consultant for Boston Scientific, study participant for ClearGuide Medical, study participant for Lumenis, chief medical officer for StepLite, and chief medical officer for DARRT, LLC.

Abbreviations Used

Appendix 1.

Survey Questions Distributed to the Participants After Completion of Experiment

Did color-coded illumination on pedals…	No	Neutral	Yes
Decrease mistakes?
Increase overall efficiency?
Add a sense of security?
Make pedals easier to use?
Would you recommend its use in regular practice?
Which color made it easiest to identify the correct pedal?
Which colors do you prefer for:
C-arm?
Laser?
USL?

USL = ultrasonic lithotripter.

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