Effects of halothane and isoflurane on transient renal dysfunction associated with infrarenal aortic cross-clamping

Discrepancies between transcutaneous and estimated glomerular filtration rates in rats with chronic kidney disease

Accurate assessment of the glomerular filtration rate (GFR) is crucial for researching kidney disease in rats. Although validation of methods that assess GFR is crucial, large-scale comparisons between different methods are lacking. Both transcutaneous GFR (tGFR) and a newly developed estimated GFR (eGFR) equation by our group provide a low-invasive approach enabling repeated measurements. The tGFR is a single bolus method using FITC-labeled sinistrin to measure GFR based on half-life of the transcutaneous signal, whilst the eGFR is based on urinary sinistrin clearance. Here, we retrospectively compared tGFR, using both 1- and 3- compartment models (tGFR_1c and tGFR_3c, respectively) to the eGFR in a historic cohort of 43 healthy male rats and 84 male rats with various models of chronic kidney disease. The eGFR was on average considerably lower than tGFR-1c and tGFR-3c (mean differences 855 and 216 μL/min, respectively) and only 20 and 47% of measurements were within 30% of each other, respectively. The relative difference between eGFR and tGFR was highest in rats with the lowest GFR. Possible explanations for the divergence are problems inherent to tGFR, such as technical issues with signal measurement, description of the signal kinetics, and translation of half-life to tGFR, which depends on distribution volume. The unknown impact of isoflurane anesthesia used in determining mGFR remains a limiting factor. Thus, our study shows that there is a severe disagreement between GFR measured by tGFR and eGFR, stressing the need for more rigorous validation of the tGFR and possible adjustments to the underlying technique.

A porcine model of systemic and renal haemodynamic responses to infrarenal aortic cross-clamping

OBJECTIVES

cross-clamping of the infrarenal aorta is associated with complex haemodynamic disturbances. Several experimental models of aortic cross-clamping (AXC) have been described with heterogeneous results. The main purpose of this study was to establish an animal model in which infrarenal AXC could reproduce similar systemic and renal haemodynamic changes to those observed in humans.

METHODS

eleven anaesthetised pigs underwent AXC just below the renal arteries. Renal blood flow was measured using clearance of (131)I hippuran. Systemic and renal parameters were collected at 3 consecutive 30-min periods.

RESULTS

AXC did not alter the extraction fraction of (131)I hippuran but was accompanied by significant (13%) decrease in cardiac index (p = 0.005) and a 23% increase in mean arterial pressure (p = 0.005). AXC induced significant 135% increase in renal vascular resistance (p = 0.012) and a 35% decrease in renal blood flow (p = 0.016). This worsened after removal of the aortic clamp, whereas systemic variables returned to baseline levels.

CONCLUSIONS

this AXC animal model reproduces the changes observed in humans. It provides a reliable animal model which allows to investigate the underlying mechanisms of renal vasoconstriction and the effect of new drugs.

Risk factors for acute postoperative renal failure in thoracic or thoracoabdominal aortic surgery: a prospective study

Acute postoperative renal failure is a common complication of thoracic aorta, thoracoabdominal aorta, or aortic arch surgery. To identify variables associated with acute postoperative renal failure, we prospectively studied 475 consecutive patients undergoing thoracoabdominal aortic surgery over a 12-yr period, including those requiring emergent surgery. One hundred twenty-one (25%) patients developed acute postoperative renal failure, and 39 (8%) required hemodialysis. Using multivariate analysis, acute postoperative renal failure was significantly associated with the following variables: age >50 yr (odds ratio [OR] 2.90 [95% confidence interval 1.52-5.53]), preoperative serum creatinine >120 micromol/L (OR 2.76 [1.70-4.48]), duration of left kidney ischemia >30 min (OR 2.01 [1.27-3.17]), packed red cells administration >5 units (OR 2.04 [1.24-3.37]), and Cell-Saver administration >5 units (OR 2.31 [1.34-1.96]). Reimplantation of visceral, renal arteries and the Adamkievicz artery; duration of visceral, spinal, and right kidney ischemia; requirement for fresh frozen plasma; administration of aprotinin; extracorporeal circulation; and procedures with circulatory arrest and profound hypothermia were not predictive of postoperative renal failure. In addition, age >50 yr (OR 5.59 [1.31-23.91]), requirement for packed red blood cells >5 unit (OR 3.91 [1.58-9.67]), and preoperative serum creatinine concentration >120 micromol/L (OR 2.26 [1.13-4.53]) were independent factors for acute renal failure requiring hemodialysis. In conclusion, acute renal failure is often observed after thoracic aortic surgery. Numerous predictive factors must be considered when evaluating the etiology of this complication.

IMPLICATIONS

Acute postoperative renal insufficiency is a common complication of thoracic aortic surgery. This study found that age >50 yr, preoperative renal dysfunction, duration of renal ischemia, and amount of blood transfusion are significant predictors of this complication.