More proof that robotic surgery is more marketing and less substance.NO STATISTICALLY SIGNIFICANT ONCOLOGIC OR CLINICAL ADVANTAGE compared to laparoscopy. Duh!
https://www.linkedin.com/pulse/robotic-versus-laparoscopic-resection-rectal-cancer-steven
We have know that the robot is more hype for a long time: In Vitro study was the most compelling.
See discussions, stats, and author profiles for this publication at:
http://www.researchgate.net/publication/51546432
Stray Electrical Currents in Laparoscopic
Instruments Used in da Vinci (R) Robot-Assisted
Surgery: An In Vitro Study
ARTICLE in JOURNAL OF ENDOUROLOGY / ENDOUROLOGICAL SOCIETY · AUGUST 2011
Impact Factor: 2.1 · DOI: 10.1089/end.2010.0706 · Source: PubMed
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Stray Electrical Currents in Laparoscopic Instruments
Used in da Vinci Robot-Assisted Surgery: An In Vitro Study
Carlos E. Mendez-Probst, M.D.,1 George Vilos, M.D., FRCSC,2 Andrew Fuller, MBBS,1 Alfonso Fernandez, M.D.,1
Paul Borg, C.Tech.,3 David Galloway, C.E.T.,3 and Stephen E. Pautler, B.Sc., M.D., FRCSC1,4
Abstract
Background and Purpose: The da Vinci surgical system requires the use of electrosurgical instruments. The
re-use of such instruments creates the potential for stray electrical currents from capacitive coupling and/or
insulation failure. We used objective measures to report the prevalence and magnitude of such stray currents.
Materials and Methods: Thirty-seven robotic instruments were tested using an electrosurgical unit (ESU) at pure
coagulation and cut waveforms at four different settings. Conductive gel-coated instruments were tested at 40W,
80W, and maximum ESU output (coagulation 120W, cut 300W). The magnitude of stray currents was measured
by an electrosurgical analyzer.
Results: At coagulation waveform in open air, 86% of instruments leaked a mean of 0.4W. In the presence of gelcoated
instruments, stray currents were detected in all instruments with means (and standard deviation) of 3.4W
( – 2), 4.1W ( – 2.3), and 4.1W ( – 2.3) at 40W, 80W, and 120W, respectively. At cut waveform in open air, none of
the instruments leaked current, while gel-coated instruments leaked a mean of 2.2W ( – 1.3), 2.2W ( – 1.9) and
3.2W ( – 1.9) at 40W, 80W, and 300W, respectively.
Conclusions: All tested instruments in our study demonstrated energy leakage. Stray currents were higher
during coagulation (high voltage) waveforms, and the magnitude was not always proportionate to the ESU
settings. Stray currents have the potential to cause electrical burns. We support the programmed end of life of da
Vinci instruments on the basis of safety. Consideration should be given to alternate energy sources or the
adoption of active electrode monitoring technology to all monopolar instruments.
Introduction
Since the introduction of robot-assisted laparoscopic
prostatectomy in 2000,1 this procedure has been demonstrated
to be feasible, safe, and effective for the surgical
treatment of patients with localized prostatic cancer.Adecade
after its introduction, approximately 85% of all radical prostatectomies
performed in the United States are completed
using robot-assisted technology.2 As of December 2009, there
were a total of 1395 units worldwide.3 Furthermore, the incorporation
of this technology is occurring at an increasing
rate, with two new centers incorporating a robot weekly.4
An electrosurgical unit (ESU) can be set to deliver power
waveforms in watts (W) (power = voltage · current) and the
energy delivered is expressed in joules where 1 joule =1W· 1
second. ESUs can deliver a continuous waveform with a low
peak to peak voltage to cut and an intermittent, modulated
(damped) waveform to coagulate. Power density (PD) is
power delivered in watts divided by the surface area of the
active electrode-tissue interface (PD =W/cm2).
As with any medical device that involves energy delivery,
ESUs have the potential to cause patient complications, with a
reported injury rate from unintended monopolar ESU at 1 to 2
episodes per 1000 procedures.5 During laparoscopic surgery,
thermal injuries are likely under-reported, because they are
frequently unrecognized at the time of the procedure and
only manifest later in the form of catastrophic and potentially
lethal complications.6 Under these circumstances, the associated
significant morbidity and mortality may lead to medicolegal
consequences.7–11
Previous work has identified at least four possible scenarios
in which electrosurgical injury (ESI) can occur including: (1)
inadvertent touching of nontargeted tissue; (2) inadvertent
direct coupling to another instrument; (3) capacitive coupling;
1Division of Urology, Department of Surgery, and 2Department of Obstetrics and Gynaecology, Schulich School of Medicine & Dentistry,
The University of Western Ontario, London, Ontario, Canada.
3Department of Biomedical Engineering, St Joseph’s Hospital, London, Ontario, Canada.
4Division of Surgical Oncology, Department of Oncology, Schulich School of Medicine & Dentistry, The University of Western Ontario,
London, Ontario, Canada.
JOURNAL OF ENDOUROLOGY
Volume 25, Number 9, September 2011
ª Mary Ann Liebert, Inc.
Pp. ---–---
DOI: 10.1089/end.2010.0706
1
and (4) insulation failure of the instrument. Insulation failure
has been demonstrated to occur in up to 19% of standard
laparoscopic instruments12; however, little information exists
to ascertain whether this problem occurs in robotic laparoscopic
instruments that require use of monopolar electrosurgery
and a finite reuse of electrosurgical instruments, both of
which provide opportunities for stray electrical currents from
capacitive coupling and/or insulation failure.
In this study, we report the prevalence and magnitude of
such stray currents measured in da Vinci (Intuitive Surgical,
Sunnyvale, CA) instruments that had reached the end of their
duty cycle.
Materials and Methods
All da Vinci robotic laparoscopic instruments that reached
the end of their service cycle at our institution during the
study period were collected (January 2009–October 2010).
Before any testing, instruments were visually inspected for
macroscopic insulation defects. The instruments were then
tested in open air with a Force 2 (Valleylab, Boulder, Colorado)
electrosurgical generator at pure coagulation and cut
waveforms in open circuit at four different settings. To simulate
the wet intra-abdominal environment, the instrument
was then thinly coated with conductive gel (Sigma gel, Parker,
Fairfield, NJ) throughout the length of the instrument with the
exception of a 1-cm gap adjacent to the instrument tip to avoid
current flow from the tip of the instrument and the arm interface
box. It was then sequentially tested at 40W, 80W, and
maximum ESU output (coag 120W, cut 300W). The magnitude
of stray currents was measured by an electrosurgical
analyzer (454A Dynatec Nevada).
Statistical analysis was performed using Graph Pad Prism 4
software (GraphPad Software Inc, San Diego, CA). Data were
analyzed using one-way analysis of variance with the Bonferroni
multiple comparison test.
Results
During the study period (January to October 2010), 37 da
Vinci robotic instruments were tested including 9 monopolar
scissors (MCS), 1 Maryland bipolar forceps (MBF), 1 monopolar
hook (MH), 6 plasma kinetic dissecting forceps (PKDF),
eight ProGrasp forceps (PF), and 12 large needle drivers
(LND). In this experiment, all available instruments were
tested, although some are not designed to deliver energy. On
visual inspection, none of the instrument insulation covers
demonstrated evidence of cracks or loss of insulator integrity.
Testing using the coagulation waveform (Table 1) in open
air showed that 70% of instruments leaked a mean of 0.38W.
The maximum leakage (0.7W) was encountered in the Pro-
Grasp forceps. In the presence of gel-coated instruments, stray
currents in the form of electrical arcing (Fig. 1) were detected
in 81% of the instruments at 40W. The mean energy detected
was 3.4W; the minimum energy was 1.5W in a PF, and the
maximum 7.7W occurred in a PKDF at 80W. Stray currents
were detected in 100% of the instruments, and the mean
leaked current was 4.1W. Using full coagulation power
(120W), the mean leak was 4.1W. The minimum leakage of
1.9W was found in a MCS and maximum of 10.5W in a PKDF.
When comparing the intensity of the leaked energy between
the dry state and the wet tests, there was a statistically significant
difference (P = 0.001). This difference was not significant
when comparing between the 40W, 80W and maximum
coagulation.
At cut waveform (Table 2) in open air, none of the instruments
leaked current. When coated with gel, arcing occurred
at 40W, the mean leaked energy was 2.2W, with the minimum
recorded energy of 0.6W in a MH and maximum of 4.3W in a
LND. At 80W, the mean energy leak was 2.2W, with the
minimum of 0.8Win aMHand maximum of 8.2Win a PKDF.
When using the maximum output (300W), the mean leaked
energy was 3.2W—a minimum of 1.6W, a maximum of
8.2W—again in the MH and PKDF instruments, respectively.
There was a statistically significant difference in the energy
leaked when comparing the dry test vs the wet tests
(P = 0.001), but not between the different current settings in
the wet group.
When comparing the coagulation and cut waveform
groups, we found no significant difference at 40W. A significantly
higher energy leak, however, was found in 80W coagulation
vs dry, 40W and 80W cut (P = 0.001). This difference
persisted when comparing the maximum coagulation vs the
dry, 40W and 80W cut (P = 0.001). No difference was found in
either group when comparing against maximum cut.
Table 1. Mean Current Leakage:
Coagulation (All Instruments)
Energy settings Leak mean ( – SD) 95% CI
Dry 40W 0.38 (0.25) 0.30–0.47
Wet 40W 3.4 (2) 2.7–4.1
Wet 80W 4.1 (2.3) 3.3–4.9
Wet 120W 4.1 (2.3) 3.3–4.9
SD= standard deviation; CI = confidence interval.
FIG. 1. Stray current with electric arcing.
Table 2. Mean Current Leakage:
Cutting (All Instruments)
Energy settings Leak mean ( – SD) 95% CI
Dry 40W 0 (0) 0
Wet 40W 2.2 (1.3) 1.8–2.7
Wet 80W 2.2 (1.9) 1.6–2.9
Wet 300W 3.2 (1.9) 2.6–3.9
SD = standard deviation; CI = confidence interval.
2 MENDEZ-PROBST ET AL.
Compared by instrument group, the highest mean leakage
was in the PKDF (mean 3.6W, one > 8W), followed by LND
(2.8W), PF (2.4W), MBF (2.4W, single instrument), MCS
(1.5W), and MH (1.1W, single instrument).
Discussion
Electrosurgical devices were pioneered by Cushing during
the 1920s. Since then, the technology has evolved and become
the most commonly used surgical energy device worldwide.13
Monopolar electrosurgery during endoscopic surgery, including
laparoscopic procedures, is associated with unique inherent
risks and complications from inadvertent direct and/or
capacitative coupling or insulation failure of the instruments.
A capacitor is defined as two conductors separated by an
insulator.14 Because of the high frequency, radiofrequency
(RF) currents necessary for electrosurgery, the active electrode
(scissors, forceps, hook, etc.) broadcasts energy outside intact
insulation, just like a radio transmitter. Any nearby conductor
(tissue, metal trocar cannula, telescope, suction-irrigation
cannula) may behave as an antenna and pick up broadcasted
stray energy.
During laparoscopic surgery, multiple instruments are inserted
through abdominal wall ports. When monopolar current
is conducted through one of these instruments,
capacitively coupled currents are invariably generated to all
nearby conductors and, in particular, to patient tissue and
organs. Capacitance then allows currents to pass to nontargeted
tissue through intact insulation. Capacitors and their
associated capacitative coupled stray current pathways are
always present during endoscopic surgery.14–18 As a rule,
these stray currents are dissipated safely back to the ESU
through the patient’s abdominal wall when metal cannulae
are used as ports, but may cause visceral burns in the presence
of plastic or hybrid cannulae.14 When stray currents flow
through a small tissue area, the current density can become
extremely high and severe burns may result. It has been estimated
that power densities of 7.5W/cm2 have the potential
to burn.14 These capacitance currents can be demonstrated by
various techniques and can even be visualized in a darkened
environment as a bluish line along the interface of the insulated
active electrode and nearby conductors. This visible effect
is referred to as a corona discharge.
Within a short period ( < 10 seconds), sufficient heat from
capacitance may build up from the corona discharge at the
interface of the active electrode and nearby conductor to burn
the insulation of the electrode, resulting in direct contact
(arcing, sparking, shorting) of the electrode to the adjacent
conductor. Each spark reaches temperatures of 700C to
1000C, and sparks are delivered at 30,000 per second in the
coagulation mode. Under sparking conditions, thermal injury
to tissue is instantaneous, inevitable, and severe. This is especially
true in hollow organs, such as bowel, where a single
spark can destroy the mucosa, which may lead to delayed
perforation 3 to 15 days postoperatively.
Our experimental data show that 100% of the reusable robotic
laparoscopic instruments used with the da Vinci platform
leak electric energy at the end of their life cycle. Previous
studies have reported prevalence of insulation defects in
laparoscopic instruments at a lower rate of 19% to 39%.12,18
These series, however, did not test robotic instruments.
Espada and associates19 reported on 81 robotic and 299 laparoscopic
instruments that were visually and electrically tested.
Insulation failures were detected in 72.8% and 35.1% of
robotic and laparoscopic instruments, respectively. The same
group also reported two complications potentially associated
with stray current in robotic instruments.20
Our series is novel in that it presents not only a qualitative
test of stray current, but also an attempt to quantitate the
amount of energy leaked. The threshold for tissue burn injury
from ESI has been reported at 7.5W/cm,2 and a full thickness
transmural burn to bowel occurs at approximately 8W.14
The higher stray currents measured in our in vitro experimental
model are likely accounted for by microscopic defects
in the instrument’s insulation. This is supported by previous
publications in which the majority of defects were invisible to
the naked eye.18 With a sensitivity of only 10%, visually
screening instruments to predict insulation failure has a limited
role. This finding mandates other forms of testing, because
these smaller defects are actually the most hazardous;
the energy leaking because of its higher current density may
cause sparks of up to 1000C and fires in the presence of
flammable gases.13
Insulation failure most likely occurs intraoperatively, during
instrument handling and reprocessing,21 and/or repetitive
and prolonged use of coagulation current.22 Other risk
factors for insulation damage include the use of 5-mm instruments
through 10-mm ports and the reuse of disposable
instruments.23 Because our testing involved only full life cycle
robotic instruments, we cannot identify at which point
the insulation damage may have occurred. Fortunately, the
finding of stray current from the used instruments at our institution
has not translated into any recognized complications.
There are several possible explanations for this,
including the insulation may have failed only at testing and
not during active life use, the insulation failed during active
use but because of safety measures, no complications occurred,
and finally, because of the low amount of leaked energy
(highest mean 4.1W), there was a subclinical burn injury
only. It is unlikely that the instruments had de novo insulation
defects, although only similar testing of randomly selected
newly minted instruments would exclude this possibility.
Nonetheless, we believe that these findings are clinically
relevant. The fact that these instruments were at the end of
their life cycle and leaked energy supports the concept of
disposal of the instruments at this point to avoid unsafe ESU
use, as per the manufacturer’s recommendation. Secondly,
surgeons must be aware that ESI can occur with robotic instruments
and vigilance for intraoperative and postoperative
complications is paramount. Although large series evaluating
outcomes after robot-assisted laparoscopic surgery have
demonstrated extremely low rates of ESI, we propose that
such injuries are likely to be both under-recognized and
under-reported. Review of the United States Food and Drug
Administration Manufacturer and User Facility Device Experience
and Medical Product Safety Network databases revealed
24 such cases.24 ESI does not universally result in
perforation and may account to some extent for more commonly
seen complications such as ileus after robot-assisted
surgery.
Although static testing may be useful in detecting faulty
instruments between use cycles, damage can always occur
after sterilization or during active use. The extrapolation of
our data in the context of active use instruments advocates for
DA VINCI INSTRUMENT STRAY ELECTRICAL CURRENTS 3
the adoption of other safety features, such as the use of alternate
energy sources (bipolar RF, ultrasonic, lasers, etc.) or
application of active electrode monitoring system, which
prevents capacitive coupling and dynamically monitors current
flowing through the circuit ; it automatically deactivates
the ESU when an insulation failure occurs or excessive capacitive
coupling occurs.
A limitation of this current study is the relatively small
number of instruments and instrument types tested in an
in vitro setting. We were limited by the availability of instruments.
We have included all robotic instruments in our analysis,
despite the fact that some of the instruments (PF and LND)
are not routinely used to deliver energy during surgery. A
comparative group of new instruments is lacking, however.
We propose that leakage from such instruments remains clinically
relevant, given the recognized potential for capacitive
coupling. A future phase of testing is planned to include newly
minted robotic instruments and at various life points in an
effort to document the chronology of damage and to further
our understanding of which procedures and instruments increase
insulation damage and may need premature replacement
independent of their recommended number of uses.
Conclusions
The finding of stray current in robotic laparoscopic instruments
at the end of their life cycle appears universal. In
some cases, these currents exceed the energy threshold needed
to cause thermal damage. Stray currents were higher
during coagulation waveforms, and the magnitude was not
always proportionally related to ESU settings. Such stray
currents can cause electrical burns to patients and/or operating
room personnel. Static testing of each instrument should
be performed before patient use, and the use of alternate energy
sources or active electrode monitoring devices is recommended
to prevent patient injury in the event of
insulation failure. Further research is needed to determine
possible risk factors and time points for insulation damage.
Disclosure Statement
No competing financial interests exist.
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Address correspondence to:
Dr. Stephen E. Pautler
Division of Urology
St Joseph’s Hospital
268 Grosvenor Street
London, Ontario, N6A 4V2
Canada
E-mail:
Stephen.Pautler@sjhc.london.on.ca
4 MENDEZ-PROBST ET AL.
Abbreviations Used
ESI¼electrosurgical injury
ESU¼electrosurgical unit
LND¼large needle drivers
MBF¼Maryland bipolar foreceps
MCS¼monopolar scissors
MH¼monopolar hook
PD¼power density
PF¼ProGrasp foreceps
PKDF¼plasma kinetic dissecting foreceps
RF¼radiofrequency
W¼watt
DA VINCI INSTRUMENT STRAY ELECTRICAL CURRENTS 5
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