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.