Warm ischemia less than 30 minutes is not necessarily safe during partial nephrectomy: Every minute matters
Section of Urology, University of Chicago Medical Center, Chicago, IL 60637, USA. Urologic Oncology
(Impact Factor: 2.77).
11/2011; 29(6):826-8. DOI: 10.1016/j.urolonc.2011.02.015
At the 11th Annual Meeting of the Society of Urologic Oncology (SUO), an expert panel discussed the importance of warm ischemia time on renal function during partial nephrectomy. The position of this manuscript is that every minute of warm ischemia time has a deleterious effect on renal function outcomes following partial nephrectomy.
The presentation was derived from a review of the published urologic, nephrology, and transplant literature related to warm ischemia time and renal function outcomes.
There exist numerous clinical models to study the effects of warm ischemia on renal function. These include the bilateral kidney, unilateral partial nephrectomy, solitary kidney partial nephrectomy, and transplant kidney model. Each of these models provides evidence for minimizing warm ischemia time to prevent acute renal failure, chronic kidney disease, and end stage renal failure. In the best available model, solitary kidney partial nephrectomy, each minute of warm ischemia was found to be associated with a 6% increased risk of acute renal failure, 7% increased risk of acute-onset end stage renal disease (ESRD), and 4% increased risk of new-onset ESRD while controlling for preoperative renal function, tumor size, and surgical approach.
There is ample evidence, consistent across multiple human kidney models, supporting the potentially deleterious renal effects of warm ischemia during partial nephrectomy. There does not appear to be a known safe threshold of warm ischemia since each minute sequentially contributes to the risk of developing acute kidney injury and renal function decline. Ultimate renal function following PN is dependent on the "3 Qs": quality (renal function prior to surgery), quantity (renal parenchyma preserved during surgery), and quickness (ischemia time).
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- "Expert's comments: Ischemia causes renal damage. The precise amount of ischemia that can be tolerated is controversial and probably depends on the individual . It is recognized that normal kidneys are resilient in withstanding limited warm ischemia and still regain function. "
Available from: Joseph G Lawen
- "There is a growing body of evidence in the urological literature that WIT in partial nephrectomy is detrimental and there should be no reason why these adverse effects associated with WIT would be irrelevant in kidney transplantation
[7,8]. Consistent with a debate in the urologic literature, there may not be a threshold effect and every minute may count
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Most studies have found cold ischemic time to be an important predictor of delayed graft function in kidney transplantation. Relatively less is known about the warm time associated with vascular anastomosis and early outcomes.
A retrospective cohort of 298 consecutive solitary deceased donor kidney recipients from January 2006 to August 2012 was analyzed to examine the association between anastomosis time and delayed graft function (need for dialysis) and length of hospital stay.
Delayed graft function (DGF) was observed in 56 patients (18.8%). The median anastomosis time was 30 minutes (interquartile range 24, 45 minutes). Anastomosis time was independently associated with DGF in a multivariable, binary logistic regression analysis (odds Ratio (OR) 1.037 per minute, 95% CI 1.016, 1.057, P = 0.001). An anastomosis time >29 minutes was also associated with a 3.5 fold higher (OR 3.5, 95% CI 1.6, 7.3, P = 0.001) risk of DGF. Median days in hospital was 9 (interquartile range 7, 14 days). Every 5 minutes of longer anastomosis time (0.20 days per minute, 95% CI 0.13, 0.27, P <0.001) was associated with 1 extra day in hospital in a multivariable linear regression model. An anastomosis time >29 minutes was associated with 3.8 (95% CI 1.6, 6.0, P <0.001) more days in hospital.
Anastomosis time may be an underappreciated but modifiable variable in dictating use of hospital resources. The impact of anastomosis time on longer term outcomes deserves further study.
Available from: Grégory Verhoest
- "Yet, the safe duration of warm ischemia remains controversial. Recent series suggested that acute renal failure would be reduced if no ischemia occurred during the procedure   . In a series comparing 362 patients with warm ischemia to 96 patients with no ischemia on a solitary kidney, patients with warm ischemia were two times more likely to experience acute renal failure, and four times more likely to present CKD stage V . "
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Partial Nephrectomy (PN) in a solitary kidney is at risk of chronic kidney disease (CKD) stage V and/or haemodialysis (HD). Our objective was to determine predictive factors of CKD stage V in this population.
Material & methods:
Data from 300 patients were retrospectively collected from 16 tertiary centres. Clinical and operative parameters, tumor characteristics and renal function before surgery were analyzed. Patients with and without CKD stage V (defined as MDRD<1 5 ml/min) were compared using χ2 and Student-t tests for qualitative and quantitative variables, respectively. Predictive factors of CKD stage V were evaluated with a multivariable analysis using a Cox regression model.
Median age and BMI were 63 years old and 26 kg/m², respectively. Most of the patients (65%) were male with an anatomic solitary kidney (88.3%). Median tumor size was 4 cm and 98% were malignant tumors. Median operative time, blood loss and clamping time were 180 min, 350 ml and 20 min respectively. Renal cooling was used in 19.3% and clamping of the pedicle was performed in 61.6%. Twenty five patients (8.5%) presented post operative CKD stage V at last follow-up and 18 underwent HD (6%) post-operatively because of acute renal insufficiency. There was no difference between CKD stage V and non CKD stage V patients concerning Charlson index, operative time (180 min vs 179 min, p = 0.39), blood loss (475 ml vs 350 ml, p = 0.51), use of renal cooling and type of clamping. Patients with CKD stage V were older (70 vs 63 years old, p = 0.005), had a lower baseline renal function (clearance MDRD 41 vs. 62 ml/min, p<0.0001) and an increased tumor size (p = 0.02). Complications occurred in 91 patients (30%) with 16% of minor (Clavien 1-2) and 14% of major (Clavien > 2) complications, respectively. In multivariable analysis, baseline MDRD, BMI, and the occurrence of a minor complication were independent predictive factors of post operative CKD stage V.
PN in a solitary kidney is at risk of post-operative CKD stage V and HD. Pre-operative altered renal function and post operative complications are the main predictive factors of permanent CKD stage V.
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