Page 38 - Read Online

Parra et al. Mini-invasive Surg 2024;8:16 https://dx.doi.org/10.20517/2574-1225.2024.01 Page 9 of 13

much renal mass as possible with the shortest possible arterial clamping time. The exact amount of time at
which the consequences of renal ischemia become irreparable is still a controversial issue in the field. The
majority are of the opinion that irreparable damage occurs after around 25 to 35 min when warm ischemia
[18]
is applied . New research suggests that when the length of warm ischemia is over 35 min, the kidneys only
recuperate to approximately 82% of the level forecasted by the degree of nephron-mass preservation,
[19]
consistent with some loss in function related to ischemia . Our series shows that ischemia was necessary
only in 52.7% of the patients and in those patients in whom arterial clamping was performed, the mean time
was eight (IQR 0-18) min. After the analysis performed in our series, we found that there are clinically
significant differences when correlating R.E.N.A.L score with ischemia time, so a higher R.E.N.A.L with the
consequent complexity of the tumor has meant the need to carry out a longer ischemia time.

In the literature, we can find some examples of this paradigm change that has occurred. Thompson et al.
evaluated solitary kidneys experiencing PN with the use of warm ischemia and concluded that longer WIT
relates to renal failure, some of them even requiring renal replacement therapy . Subsequently, when
[15]
Thompson et al. reanalyzed their cohort , including subjective estimation of conserved parenchymal
[15]
volume as a covariate, only the percent of parenchyma conserved and preoperative GFR remained essential
predictors of new-onset CKD, leaving aside the WIT . Thompson et al. conclude, in a recent publication,
[11]
that in the scenery of SRM and restricted durations of warm ischemia, the outcomes observed for on-clamp
and off-clamp methods were similar, and reconsider the function of ischemia as a risk factor for developing
[20]
CKD .

The standard approach to reduce ischemic injury has been the induction of hypothermia, called cold
ischemia. Renal energy spending is decreased by superficial cooling with ice which also partially improves
the hostile impact of warm ischemia and reperfusion injury . Since the induction of cold ischemia is still
[21]
technically difficult with minimally invasive techniques, numerous surgical approaches have been proposed
to reduce the duration of warm ischemia. We can reduce global renal ischemia time considerably by
premature unclamping of the main renal artery, which is carried out after a first continuous suture has been
[22]
made . Since clamping of the principal artery implies the highest ischemic offense, this can be diminished
[23]
by selective clamping of only the appropriate segmental arteries . Specifically, zero-ischemia PN signifies
superselective clamping of tumor-specific artery branches, which are carefully dissected and superselectively
clamped with clips . Off-clamp LPN or robot-assisted PN (RAPN) are technically demanding approaches.
[24]
Also, some authors questioned off-clamp LPN/RAPN as potentially negatively impacting the perioperative
outcomes of the surgery, increasing blood loss, worsening the vision of the operative field, and supporting
the probability of complications and positive surgical margins .
[25]
As we can see in our series, one of the most commonly used strategies is the absence of arterial clamping
(52.7%). This is probably related to the experience of the surgeons and it could generate a bias since its
implementation requires a long learning curve. Another possible bias is the fact that the mean R.E.N.A.L.
score was 6, so most of the tumors were easy to approach from a technical point of view. In spite of this, as
we have already mentioned, there is a relationship with significant results in a longer ischemia time in those
cases with a higher renal score.

Xiong et al. have recently reported the histologic changes in healthy renal parenchyma caused by ischemia
time, consisting of measuring changes of preserved renal parenchyma from 65 patients who first underwent
PN and subsequently required a RN 2.4 years later on average . The authors evaluated if the ischemia
[26]
duration or type of ischemia conveyed differences in advanced histologic changes with a CKD score (0-12),
indicating a glomerular/tubular/interstitial/vascular status summary. Particularly, comparison of