Elevated Renal Oxygen Extraction During Open Abdominal Aortic Aneurysm Repair Is Related to Postoperative Renal Dysfunction

Renal Hemodynamics, Function, and Oxygenation in Critically Ill Patients and after Major Surgery

This review outlines the available data from the work of our group on renal hemodynamics, function, and oxygenation in patients who are critically ill with acute renal dysfunction, such as those with postoperative AKI, those in early clinical septic shock, in patients undergoing cardiac surgery with cardiopulmonary bypass, or in patients undergoing liver transplantation. We also provide information on renal hemodynamics, function, and oxygenation in patients with chronic renal impairment due to congestive heart failure. This review will argue that, for all of these groups of patients, the common denominator is that renal oxygenation is impaired due to a lower renal oxygen delivery or a pronounced increase in renal oxygen consumption.

Renal Near-Infrared Spectroscopy for Assessment of Renal Oxygenation in Adults Undergoing Cardiac Surgery: A Method Validation Study

OBJECTIVE

To investigate the correlation between invasively measured renal venous oxygen saturation (SrvO₂) and tissue oxygenation (rSO₂) measured with near-infrared spectroscopy (NIRS) in adult patients undergoing cardiac surgery.

DESIGN

Prospective observational study.

SETTING

Single cardiac surgery center at a university hospital.

PARTICIPANTS

Thirteen adult patients with skin- to- kidney distance ≤4 cm undergoing open cardiac surgery with cardiopulmonary bypass (CPB).

INTERVENTIONS

All patients received renal vein catheters for invasive measurement of SrvO₂, and NIRS electrodes for assessment of renal rSO₂ were placed over the kidney using ultrasound guidance. Measurements were made before CPB, during CPB at 3 different flow rates (2.4, 2.7, and 3.0 L/min/m²), and after CPB.

MEASUREMENTS AND MAIN RESULTS

Repeated- measures correlation analyses and Bland-Altman plots were used to study the correlation and agreement between rSO₂ and SrvO₂. For all measurement points, renal rSO₂ correlated with SrvO₂ (r_rm = 0.61, p < 0.001), and the mean difference (bias) between rSO₂ and SrvO₂ was -2.71 ± 7.22 (p = 0.002), with an error of 17.6%. When measurements during CPB and before and after CPB were studied separately, rSO₂ and SrvO₂ were correlated (r_rm = 0.51, p < 0.007 and r_rm = 0.73, p < 0.001, respectively). During CPB, renal rSO₂ predicted SrvO₂ with a bias of -3.41 ± 7.76 (p = 0.009) and an error of 18.8%. Before and after CPB, the mean difference was -1.93 ± 6.60 (p = 0.092), with an error of 16.2%.

CONCLUSIONS

Renal rSO₂ is correlated to and predicts SrvO₂ with a small bias and acceptable agreement. Further studies are needed before renal NIRS can be used as a surrogate marker of renal oxygenation in clinical practice.