Surgical outcomes
Operation time significantly decreased with increasing case volume:
cases in group 1 had a significantly longer operation time compared to
group 2 and group 3 (both p <0.001). Operation time in
the newly added group 3 was similar to group 2 (p =1.00)
(Figure 2 ).
In 50 patients a grade 3-4 (severe) adverse event occurred at any time
during follow-up of whom 31 patients (19.4%) had a grade 3-4 adverse
event that occurred intraoperatively or within the initial 42
postoperative days. No grade 5 event (death related to surgery)
occurred. The number of severe adverse events was highest in group 1 but
did not significantly differ between the three groups: 13 patients
(21.3%) in group 1, 10 (9.6%) patients in group 2, and 8 (13.1%)
patients in group 3 (p =0.11)(see Table 1 ). When
comparing the three groups separately, the proportion of severe adverse
events in group 3 was not significantly different from group 1 and group
2, but severe adverse events were significantly lower in group 2
compared to group 1 (p =0.04).
One case was converted to conventional laparoscopy because technical
issues hindered robot-assisted surgery (i.e. clashing robotic arms). No
intraoperative surgical adverse events necessitated a direct conversion
to laparotomy or laparoscopy. Table 2 provides an detailed
overview of all intraoperative and postoperative grade 3-5 adverse
events within 42 days after surgery, of which multiple adverse events
could occur in one patient. In total 36 severe adverse events occurred
within 42 days in 31 patients: 28 grade 3 events in 23 patients and
eight grade 4 events in eight patients. Six patients underwent
laparotomy as a secondary procedure to manage their grade 4 adverse
event: three with ureter injury, two with postoperative hypovolemic
shock due to intraabdominal haemorrhage, and one with perforation of the
sigmoid. One patient with a grade 4 event needed surgical intervention
for a severe cervical bleeding but no laparotomy. The eighth patient
with a grade 4 event had an obstructed airway caused by a
pneumomediastinum. This was detected directly after detubation and
managed by reintubation and ICU admission where laryngoscopy excluded an
airway injury.
Regarding the distribution of severe adverse events across the three
groups, a shift from intraoperative to postoperative adverse events was
observed: in group 1 four intraoperative events occurred compared to
zero in group 3. This shift is inherent to the shift from severe
urological injuries to postoperative symptomatic lymphoceles (seeSupplementary Table S1 ). Subgroups of adverse events were too
small to perform reliable statistical analysis on.