Monitoring Renal Oximetry in Donors Undergoing Normothermic Regional Perfusion After Circulatory Determination of Death

Regional tissue oxygen saturation (rSO2) monitoring through near-infrared spectroscopy (NIRS) has been reported as a non-invasive strategy to estimate the adequacy of matching between oxygen delivery (DO2) and oxygen consumption. The rSO2 monitoring is also reliable in non-pulsatile blood flow states, such as during veno-arterial extracorporeal life support (ECLS). Renal rSO2 has been specifically advocated as a useful monitoring tool in neonatal and pediatric patients on ECLS,1 and could also be applied in adults, provided that the depth of the kidney is consistent with the reliability of the measurement.2,3 Renal rSO2 may be used as a surrogate of the level of renal oxygenation,2 potentially predicting risk of developing acute kidney injury.3 We monitored continuously the periprocedural renal rSO2 through multi-wavelength sensors and NIRS technology (O3 Regional Oximeter, Masimo Corporation, Irvine, CA) in two controlled donors after circulatory determination of death undergoing abdominal normothermic regional perfusion (A-NRP) (Figures 1 and 2).4Figure 1.: A: Bilateral renal rSO2 in cDCD donor 1. Green numbers and horizontal lines: baseline values; light blue lines: trend; light blue numbers: last measured values. B: Captions and markings added to image A. Vertical dotted green line: initiation of WLST; dotted white lines: 20-minute long NNT, initiating with final asystole (any evidence of cardiac electrical activity, including sporadic QRS complexes, interrupts NNT according to the country-specific laws).4 Vertical dotted red line: A-NRP initiation. Between NNT and A-NRP few minutes are required to insert cannulae, connect the circuit, and inflate aortic balloon.4 Vertical dotted light blue line: CPS administration, initiating SCS. Squared arrows: at NRP initiation, slow and moderate increase in rSO2 was observed bilaterally; transesophageal ultrasound revealed too low aortic balloon. After repositioning, rSO2 abruptly increased, even if achieving target EBF* was complicated by drainage insufficiency (white arrows). Refractory drainage insufficiency during the second half of NRP procedure, with persistently low EBF, was associated with bilateral renal rSO2 below baseline levels. C. Timing and monitoring associated with major events in Donor 1. SpO2 below 70–75% and SBP below 70 mm Hg are identified as initiating fWIT. Numbers between parentheses refer to the delta from baseline value in percentage. *60% of predicted EBF to provide a Cardiac Index of 2.4.4 A-NRP, abdominal normothermic regional perfusion; aWIT, asystolic warm ischemia time; cDCD, controlled donor after circulatory determination of death; CPS, cold preservation solution; EBF, extracorporeal blood flow; fWIT, functional warm ischemia time; MAP, mean arterial pressure; NNT, no-touch time; rSO2, regional tissue oxygen saturation; SBP, systolic blood pressure; SCS, static cold storage; SpO2, peripheral oxygen saturation; WLST, withdrawal of life-sustaining treatments.Figure 2.: A: Bilateral renal rSO2 in cDCD donor 2. Green numbers and horizontal lines: baseline values; light blue lines: trend; light blue numbers: last measured values. B: Captions and markings added to image A. Vertical dotted green line: initiation of WLST; dotted white lines: 20-minute long NNT. Vertical dotted red line: NRP initiation. Vertical dotted light blue line: CPS administration. White arrows, oxygenation of the CPS was associated with bilateral renal rSO2 below baseline level. C: Timing and monitoring associated with major events in donor 2. Numbers between parentheses refer to the delta from baseline value in percentage. *60% of predicted EBF to provide a Cardiac Index of 2.4.4 ▵Controlled increment and decrement of the EBF was performed under controlled conditions after NRP stabilization to monitor the impact on other parameters. A-NRP, abdominal normothermic regional perfusion; aWIT, asystolic warm ischemia time; cDCD, controlled donor after circulatory determination of death; CPS, cold preservation solution; EBF, extracorporeal blood flow; fWIT, functional warm ischemia time; MAP, mean arterial pressure; NNT, no-touch time; rSO2, regional tissue oxygen saturation; SBP, systolic blood pressure; SCS, static cold storage; SpO2, peripheral oxygen saturation; WLST, withdrawal of life-sustaining treatments.The sensors were placed bilaterally in paravertebral/scapular line location under ultrasonographic guidance, to accurately overly the site of minimal renal depth, to improve signal reliability in reflecting cortical rSO2 (Figure 3A–C),2,3 rather than blindly positioning the sensors on the flanks, unlikely reaching renal tissue.5 This posterior positioning is not affected by laparotomy, even if this is extended to the flanks, and when median sternotomy is performed, to implement multi-organ recovery and a careful donor risk assessment.Figure 3.: Positioning of oximetry sensors for renal regional tissue oxygen saturation. A and B: Ultrasonographic localisations of the kidneys, and measurement to locate point of minimal renal depth. C: The sensors overlying kidneys (O3 Regional Oximeter, Masimo Corporation, Irvine, CA).The trend in renal rSO2 could be used to provide informations on the appropriateness of DO2 in the phase preceding the withdrawal of life-sustaining treatments (WLST) and to collect data on the variable impact of hypotension and desaturation monitored through peripheral pulse oximetry. The rSO2 signal remained available during the late phase of WLST and during the asystolic phase when pulse oximetry signal was lost. These data could be particularly significant if the agonal period is protracted, or if a prolonged no-touch time is required (Figure 3, D and E). Moreover, renal rSO2 could be useful during reperfusion, as a supplementary tool to early detect complications impacting on DO2, and during in-situ cold preservation induction. Additional data on rSO2, on the technique used to monitor renal rSO2, and on A-NRP4 are included in supplementary file 1, Supplemental Digital Content 1, https://links.lww.com/ASAIO/B125.