The effect of whole-body cooling on renal function in post-cardiac arrest patients

Background: To evaluate the incidence of Acute Kidney Injury (AKI) during therapeutic hypothermia (TH) and rewarming in comatose patients resuscitated from Cardiac Arrest (CA). Methods: We have performed a pilot study of consecutive comatose patients resuscitated from CA and admitted to our Intensive Care Unit (ICU) from January 2013 to March 2015. The surface cooling devices used were: 1) Arctic Sun (R) 5000; 2) Blanketrol (R) III. Data obtained at baseline and during TH included: temperature trend and rate, serum creatinine, interleukin 1-beta, interleukin 6 (IL-6), urinary Interleukin-18 (uIL-18), diuretic use, urine output, fluid balance (FB). AKI was defined according to Kidney Diseases Improving Global Outcomes (KDIGO) criteria. Results: Thirty-six patients were treated with TH out of 46 ICU admissions (78%). According to KDIGO classification, 21 (58%) had no evidence of AKI while 15 (41.7%) presented AKI during TH. In particular, the incidence of AKI was 2.8% at 24 h, 33.33% at 48 h and 30.6% at 72 h from the onset of cooling. Slower rewarming (above 600 min) was associated with with a non-significant lower incidence of AKI and with a non-significant lower levels of IL-6 and IL-18u. Only two patients required renal replacement therapy during TH (7.6%). Median cumulative FB was 2441 [437-4043] ml for all patients; 3140 [1421-4347] and 1332 [-131-3772] specifically for AKI and not-AKI patients. Conclusions: The hypothermia treatment, if not well performed, could be a double-edged sword for kidneys: whereas hypothermia may confer protection by reducing metabolism and oxygen consumption, rapid rewarming could nullify benefits leading to a worsening of kidney function and AKI. Additional clinical studies are needed to determine the optimal rewarming rate and strategy.