Prolonged ischaemia during partial nephrectomy: impact of warm vs cold.

Objective: To evaluate the impact of prolonged ischaemia during partial nephrectomy (PN), which remains understudied despite its potential clinical relevance.

Patients and methods: Of 1371 patients managed with on-clamp PN (2011-2014), 759 (55%) had imaging and assessment of serum creatinine levels before and after PN within the appropriate timeframes necessary for inclusion. This timeframe was chosen to allow for a robust analysis of both warm and cold ischaemia. Recovery from ischaemia (Rec_ischaemia) was defined as ipsilateral glomerular filtration rate (GFR) preserved, normalized by percentage of parenchymal volume preserved (PPVP), and would be 100% if all nephrons recovered completely from ischaemia. Pearson correlation and multivariable linear regression models were used to assess associations between Rec_ischaemia and ischaemia type and duration.

Results: Of 759 patients, 525 (69%) were managed with warm ischaemia. The median warm/cold ischaemia times were 22 and 30 min, respectively. Overall, the median percent ipsilateral GFR preserved, PPVP and Rec_ischaemia were 79%, 83% and 96%, respectively. Segmented regression analysis demonstrated substantially greater decline in Rec_ischaemia, beginning at approximately 30 min for warm ischaemia, which was not observed for hypothermia. Prolonged ischaemia (defined as >30 min) occurred in 197 patients (26%; 88 warm/109 cold). For limited ischaemia (≤30 min), hypothermia was often used for tumours with increased tumour size and complexity (P < 0.01), while for prolonged ischaemia, the warm/cold subgroups had similar patient and tumour characteristics. For limited ischaemia and prolonged hypothermia, median Rec_ischaemia remained >95%, independent of ischaemia time. Differences in Rec_ischaemia between the warm and cold cohorts became significant only after 30 min (P < 0.05). On multivariable analysis, prolonged warm ischaemia was associated with reduced Rec_ischaemia (P = 0.02), which fell 3.9% for every additional 10 min beyond 30 min.

Conclusions: Our data suggest that Rec_ischaemia begins to decline significantly after 30 min during PN, although hypothermia was protective. Avoidance of prolonged warm ischaemia should be prioritized in patients with solitary kidneys and/or significant pre-existing chronic kidney disease.