Renal hemodynamic and functional effect of PEEP ventilation in human renal transplantations.

Abstract

Increased intrathoracic pressure with positive pressure breathing (PPB) induces renal hypoperfusion and excretion function impairment the mechanism of which may be partially related to reflex sympathetic nerve activation. The consequences of renal denervation on PPB-induced renal impairment are unknown. This study was conducted to evaluate the effects of increasing intrathoracic pressure with positive end-expiratory pressure (PEEP) on renal blood flow (RBF, pulsed Doppler implantable microprobes) and function in 12 kidney transplantation recipients during the immediate post-transplantation period. Three sets of measurements were performed during successively zero end-expiratory pressure (ZEEP), 15 cm H2O PEEP, and back to ZEEP. PEEP ventilation was associated with mean arterial pressure (MAP) and cardiac output (CO) decrease (-12%, p < 0.01; -26%, p < 0.01, respectively). RBF remained constant in the three protocol conditions. PEEP ventilation was associated with a decrease in urinary output (8.5 +/- 5.6 versus 12.9 +/- 8.6 ml/min; p < 0.01), urinary sodium concentration (115 +/- 14 versus 121 +/- 12 mmol/L; p < 0.01) sodium excretion rate (1 +/- 0.7 versus 1.6 +/- 1.1 mmol/min; p < 0.01), and creatinine clearance (17.1 +/- 10 versus 23.2 +/- 13.6 ml/min; p < 0.01). PEEP-induced urinary output decrease was correlated to renal perfusion pressure decrease (r = 0.7, p = 0.016). These results suggest that despite denervation and renal blood flow stability, renal handling of water and salt is perfusion pressure-dependent during PEEP in human renal allograft recipients.

Sepsis-Associated Acute Kidney Injury: Macrohemodynamic and Microhemodynamic Alterations in the Renal Circulation

“…In these studies, if the model was associated with a hyperdynamic circulation (high cardiac output), RBF consistently was preserved or increased, and cardiac output was the only significant predictor of RBF in multivariate analysis. 23 Autoregulation of RBF has been shown to be impaired in critical illness 24 and during AKI, 25 so that RBF can vary with cardiac output, which may be normal, increased, or depressed, depending on the global hemodynamic context of a patient or the characteristics of the AKI model chosen. Thus, models using larger animals with hyperdynamic sepsis may be more relevant to human septic shock and the development of SA-AKI.…”

Acute Respiratory Distress Syndrome and Risk of AKI among Critically Ill Patients

“…Several lines of evidence suggest that mechanical ventilation and acute respiratory distress syndrome (ARDS) may have adverse effects on kidney function via three main mechanisms. First, positive-pressure ventilation may reduce cardiac output and increase central venous pressure, thereby diminishing renal blood flow, free water clearance, or the GFR (14)(15)(16)(17). In addition, changes in arterial blood O 2 or CO 2 may influence renal vascular resistance, renal perfusion, or diuresis (18)(19)(20)(21)(22).…”

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“…Kidney blood flow was measured with a pulsed Doppler flowmeter linked to a disposable implantable microprobe previously described and validated. [21][22][23] The implanted method has the advantage of eliminating the uncertainty of flow accuracy related to operator training, patient echogenicity, and potential impact of variant ultrasound incidence angle with the vessel axis. The renal graft artery diameter and section were accurately measured with the pulsed Doppler device.…”

“…Renal blood flow was measured by the pulsed Doppler technique using implantable 8-MHz pulsed Doppler microprobes (3 mm wide, 4 mm long); this technique has been previously published and validated. [21][22][23] Briefly, the piezoelectric crystal, glued on a silicone prism fixing the ultrasonographic incidence angle at 60° was implanted at the end of surgery. At the end of the surgical procedure, the Doppler microprobe was sutured to the adventitia of the graft artery 2 cm downstream from the anastomosis to the external iliac artery.…”