Renal vasoconstriction and transient declamp hypotension after infrarenal aortic occlusion: role of plasma purine degradation products

To better understand renal and systemic hemodynamics associated with hindquarter ischemia produced by aortic compression, chloralose-anesthetized dogs were given phentolamine while an external clamp maintained infrarenal aortic pressure below 25 mm Hg for 45 minutes. In four sham-operated dogs, infrarenal pressure was maintained; reinforced cannulas, capable of resisting clamp compression, were placed within the aorta and the inferior vena cava. Suprarenal and infrarenal arterial pressure and renal blood flow were continuously monitored. Blood samples taken before clamp application and at 1, 3, 5, and 10 minutes after clamp removal were assayed for adenosine, inosine, xanthine, and hypoxanthine. On clamp removal suprarenal pressure immediately dropped from a preclamp pressure of 114 to 82 mm Hg but returned to preclamp values within 1 minute. Renal blood flow was significantly reduced after clamp release, reaching a nadir of 39% of preclamp flow. This reduction persisted despite a normalization of arterial pressure. Summed plasma purines were significantly elevated 1 minute after clamp removal. Sham-operated dogs showed no significant alterations in arterial pressure, renal blood flow, or plasma purine levels. This study demonstrates a significant non-alpha-adrenergic receptor-mediated reduction in renal blood flow and a coincident increase in purine degradation products after removal of an infrarenal aortic cross-clamp.     

Renal Artery Endarterectomy for Treatment of Renovascular Hypertension Combined with Infrarenal Aortic Reconstruction: Analysis of Surgical Results

From June 1995 to February 2000, 16 patients with renovascular hypertension had bilateral transaortic renal artery endarterectomy (RA TEA) combined with either infrarenal aortic aneurysm repair (8 patients) or infrarenal aortodistal bypass for occlusive disease (8 patients). Aortic clamp level for RA TEA was supraceliac in eight patients and suprarenal in eight patients with a mean clamp time of 19 min (range 14 to 25 min). Perioperative complications occurred in four patients. These included respiratory insufficiency with prolonged intubation (1 patient), prolonged intubation with transient renal failure requiring temporary dialysis (1 patient), acute thrombosis of right limb of aortofemoral bypass graft (1 patient) and major left hemispheric cerebrovascular accident (1 patient). Results from this contemporary patient series demonstrate acceptable perioperative morbidity and mortality when RA TEA for treatment of renovascular hypertension is combined with infrarenal aortic reconstruction. In this setting, either supraceliac or suprarenal aortic clamping for short time periods appears to be well tolerated. Clinical outcome is enhanced by salvage of renal function, decrease in medication requirement, and improvement in blood pressure control.     

The effect of renin-angiotensin system blockade on visceral blood flow during and after thoracic aortic cross-clamping

Surgical procedures necessitating clamping of the thoracic aorta are associated with a high incidence of postoperative renal dysfunction. Plasma renin activity is elevated during and after thoracic aortic occlusion in animals. The pathophysiology of the renal dysfunction may involve the renin-angiotensin system. Blockade of the renin-angiotensin system was studied in a canine model during occlusion of the thoracic aorta. Saralasin, a competitive blocker of angiotensin II, and the converting enzyme inhibitor MK422 were studied. Sixteen animals were separated into three treatment groups: control (five animals), saralasin (five), and MK422 (six). All dogs underwent clamping of the thoracic aorta for 60 minutes. In control animals, plasma renin activity increased from 0.16 +/- 0.04 to 6.41 +/- 1.57 ng/ml/hr at 30 minutes after thoracic aortic occlusion (p less than 0.05). Thirty minutes after cross-clamp release, plasma renin activity remained 10 times greater than baseline, 1.47 +/- 0.20 ng/ml/hr (p less than 0.05). Renal blood flow was measured with 15 micron microspheres before, during, and after thoracic clamping. In control animals, renal cortical blood flow decreased during cross-clamping and remained below baseline after clamp release: baseline, 7.05 +/- 0.98 ml/gm/min (standard error of the mean); 30 min after clamp release, 3.77 +/- 0.43 ml/gm/min (standard error of the mean) (p less than 0.05). In the MK422 group, renal cortical blood flows returned to baseline after cross-clamp release: baseline, 6.38 +/- 0.49 ml/gm/min; 30 minutes after clamp release, 7.30 +/- 1.6 ml/gm/min. Infusion of MK422 after placement of the thoracic aortic cross-clamp resulted in normal renal blood flow after clamp release. This protective effect was not seen with saralasin. The resumption of normal renal cortical blood flow after the administration of the converting enzyme inhibitor MK422 suggests that elevated plasma renin activity may contribute to renal dysfunction after thoracic aortic occlusion.     

The effect of mannitol and dopamine on the renal response to thoracic aortic cross-clamping

Postoperative renal failure and insufficiency are important complications of operations that require thoracic aortic cross-clamping. Successful application of pharmacologic methods to protect renal function would be clinically useful. The ability of mannitol and dopamine to prevent renal dysfunction in a canine model of thoracic aortic cross-clamping was studied. Twenty animals were divided into four equal groups, and all underwent thoracic aortic cross-clamping for 60 minutes. An intra-aortic infusion of saline (control), mannitol, dopamine, or mannitol plus dopamine was started before, and continued during, the period of aortic occlusion. Glomerular filtration rate was significantly depressed 60 minutes after clamp release, and although there was some recovery in treated animals 150 minutes after clamp release, it remained significantly decreased (52% to 73% of baseline values, p less than 0.01). Renal blood flow was significantly reduced 60 minutes after clamp release, and there was no recovery in any group at 150 minutes (38% to 56% of baseline values, p less than 0.01). No significant differences in osmolar clearance or fractional excretion of sodium were evident between groups. These data reveal that the profound reductions in glomerular filtration and renal blood flow induced by thoracic aortic cross-clamping were not attenuated by mannitol or dopamine and suggest that efforts to protect renal function should be directed toward improving renal blood flow in the post-clamp period.     

SIGMOlD AND GASTRIC TONOMETRY DURING INFRARENAL AORTIC ANEURYSM REPAIR

Background: The value of the sigmoid tonometer in predicting sigmoid ischaemia and postoperative enteric organism infection has been reported but the value of tonometric measurements has been challenged. The purpose of this study was to examine the use of tonometric measurements in a series of patients undergoing infrarenal aortic aneurysm repair. Methods: We assessed the results obtained when sigmoid (n= 11) and gastric (n = 8) tonometry were performed in patients undergoing infrarenal aortic aneurysm repair (n= 11). We measured blood flow ultrasonically (n = 6) in the inferior mesenteric artery (IMA) and IMA stump pressures. Sigmoid and gastric tonometry were measured prior to clamping of the infrarenal aorta, during cross clamping and after clamp release at 1, 4, 16 and 20 h. Ultrasonic flow was measured before clamping. Stump pressures in the IMA were measured before, during and after clamping. Results: The IMA was chronically occluded in five patients. The IMA flow was 37.5 ± 8.7 mL/min (mean ± s.e.). The mean IMA stump pressures before, during and after clamping were 64 ± 13, 48 ± 8 and 69 ± 10 mmHg, respectively, and did not differ significantly. Mean systematic arterial pressures at these times were 89 ± 7, 95 ± 5 and 86 ± 8 mmHg. These did not differ significantly or when compared with IMA stump pressure. The gradient between systemic arterial pressure and IMA stump pressure did not vary significantly at any of these times. Sigmoid and gastric intramucosal pH (pHi) did not differ significantly at any of the above times. Both sigmoid and gastric pHi dropped on clamp application but 4 h afterwards had returned to baseline levels. Systemic arterial pH reflected significant ischaemia during clamping and shortly after release of the clamp (P= 0.008). Conclusions: Tonometry may reflect systemic events as much as regional ischaemia. Useful tonometry results may depend on the development of a trend rather than individual measurements. The routine use of tonometry to detect intestinal ischaemia may not be cost-effective in aortic surgery.     

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.     

The effects of fenoldopam on renal blood flow and tubular function during aortic cross-clamping in anaesthetized dogs

Postoperative renal impairment is a recognized complication of infrarenal aortic cross-clamping. Fenoldopam, a selective dopamine agonist, may increase renal blood flow and decrease tubular oxygen consumption. The objective of this study was to quantify the effects of fenoldopam (0.1 microg kg-1 min-1) on renal blood flow and renal tubular function in anaesthetized dogs that have undergone aortic cross clamping. Eight labrador dogs were selected to receive either saline or fenoldopam (0.1 microg kg-1 min-1) intravenously. Arterial pressure, heart rate, renal blood flow, urinary output, fractional excretion of sodium, creatinine clearance and lithium clearance were measured (a) prior to infusions of saline or fenoldopam (b) 1 h after commencing the infusion (c) during a 90-min period of infrarenal aortic cross-clamping with concurrent infusion of fenoldopam or saline and (d) for 1 h after simultaneous aortic declamping and discontinuation of the infusions. There was no haemodynamic instability upon commencing the infusion of fenoldopam (0.1 microg kg-1 min-1). Creatinine clearance (2.03 +/- 0.5-2.45 +/- 0.3 mL min-1 kg-1 (mean +/- SD)), urine output (0.23 +/- 0.16-0.35 +/- 0.23 mL min-1 (mean +/- SD)), and fractional excretion of sodium (0.7 +/- 0.52-1.3 +/- 0.73% (mean +/- SD)) increased (P < 0.05), following commencement of the fenoldopam infusion. Fractional excretion of sodium (1.2 +/- 0.7% (mean +/- SD)) and urine output (0. 36 +/- 0.21 mL min-1 (mean +/- SD)) were maintained during the aortic cross-clamp period (P < 0.05). Renal blood flow increased when the fenoldopam infusion was commenced (145 +/- 43.3-161 +/- 39. 2 mL min-1 (mean +/- SD)) and remained greater than baseline during the aortic cross-clamping period (152 +/- 44 mL min-1 (mean +/- SD)), although these increases did not reach statistical significance. The most striking abnormalities observed by electron microscopy were marked disruption of the microvillus brush border in proximal tubules, vacuolation and separation of epithelial cells on basolateral infolds. The changes were similar in the two groups. In conclusion fenoldopam (0.1 microg kg-1 min-1) may have renoprotective effects which persist during infrarenal aortic cross clamping.     

Contemporary results of juxtarenal aneurysm repair

OBJECTIVE: The increasing use of aortic endografts predictably will add to the complexity of open abdominal aortic aneurysm (AAA) repair and, therefore, the proportion of surgically treated infrarenal AAAs that are juxtarenal in location (JRA) will grow. This study reviews a single-center experience with JRAs. METHODS: Between June 1994 and December 2000, 138 patients underwent elective repair of a JRA, comprising 16.1% of 859 consecutive asymptomatic and intact symptomatic nonruptured infrarenal AAAs repaired over the same period. All patients with JRA needed proximal suprarenal clamping (SRC) or supravisceral (SVC) clamping. Patient demographics, selected risk factors, and operative details were recorded. Univariate analyses of selected risk factors for an adverse perioperative event were assessed, and multivariate analyses were performed with linear and logistic regression with backwards selection. RESULTS: SRC was used in 95 patients (69%), and 43 patients (31%) underwent SVC. The mortality rate was 5.1% (7/138) for JRA repair, and 2.8% (20/720) for infrarenal AAA repair (P =.03). The mortality rate was significantly greater for those patients who received SVC compared with SRC (11.6% versus 2.1%; P =.02). Multivariate analysis identified SVC position as the only independent predictor of mortality (odds ratio [OR], 6.1; 95% CI, 1.1 to 32.9; P =.035). Transient renal insufficiency occurred in 39 patients (28.3%), but only eight patients (5.8%) needed dialysis. Patients who had SVC had a significantly greater rate of renal insufficiency than those who received SRC (41.9% versus 22.1%; P =.02). Multivariate analysis showed SVC position (OR, 3.3; 95% CI, 1.4 to 7.8; P =.008), diabetes (OR, 3.7; 95% CI, 1.1 to 12.9; P =.04), and preoperative renal insufficiency (OR, 5.8; 95% CI, 2.2 to 15.4; P <.001) were independent predictors of postoperative renal insufficiency. Renal ischemia during proximal clamping cannot alone explain renal complications because clamp time was shorter in patients with SVC (24.9 +/- 2.4 minutes versus 32.2 +/- 1.5 minutes; P =.009). CONCLUSION: JRA repair can be accomplished with a low mortality rate, but a more proximal clamp position may adversely affect outcome in these patients. Postoperative renal insufficiency is related to diabetes, preoperative renal insufficiency, and SVC position. These results suggest SRC is safer than SVC for proximal aortic clamp control of JRAs. Although clamp level must be tailored to patient anatomy, outcome may be improved if the clamp level can be kept distal to the superior mesenteric artery origin.     

Characterization of renal parenchymal perfusion during experimental infrarenal aortic clamping and declamping with enhanced thermodiffusion electrodes

Despite multiple previous experimental and clinical investigations, it has not been fully clarified until now whether infrarenal aortic cross-clamping (IRAC) induces a significant disturbance of renal parenchymal perfusion. Most renal cortical flow data collected thus far have been heterogenous because of inherent limitations of available measurement technology. The enhanced thermal diffusion (TD) electrode is a newly developed and previously validated prototype device that allows continuous quantification of parenchymal kidney perfusion after local probe implantation. We monitored renal perfusion during experimental IRAC with TD for the first time, thereby also evaluating the potential applicability of the method in clinical aortic surgery. IRAC (20 min) followed by sudden declamping was performed in pigs under general anesthesia (n = 14). Renal cortical blood flow (RCBF) was continuously quantified by TD, total aortic flow (TABF) and renal artery flow (RABF) were measured by ultrasonic flow probes, and parameters of systemic circulation were determined by Swan-Ganz catheter. Our results showed that kidney perfusion can be continuously quantified using TD electrodes during experimental aortic surgery in a porcine model. IRAC does not lead to a significant impairment of RCBF in young pigs as measured by TD. Renal perfusion appears to be predominantly pressure driven. Consequently, abrubt aortic declamping can bring about prolonged renal ischemia. Transfer of the TD method to RCBF monitoring during clinical aortic surgery appears to be feasible and should be investigated in selected cases.     

Dopexamine hydrochloride does not modify hemodynamic response or tissue oxygenation or gut permeability during abdominal aortic surgery

PURPOSE: To assess the effects of intraoperative infusion of dopexamine (a DA-1 and B2 adrenoreceptor agonist) on hemodynamic function, tissue oxygen delivery and consumption, splanchnic perfusion and gut permeability following aortic cross- clamp and release. METHODS: In a randomised double blind controlled trial 24 patients scheduled for elective infrarenal abdominal aortic aneurysm repair were studied in two centres and were assigned to one of two treatment groups. Group I received a dopexamine infusion starting at 0.5 microg x kg(-1) x min(-1) increased to 2 microg x kg(-1) x min(-1) maintaining a stable heart rate; Group II received a placebo infusion titrated in the same volumes following induction of anesthesia. Measured and derived hemodynamic data, tissue oxygen delivery and extraction and gut permeability were recorded at set time points throughout the procedure. RESULTS: Dopexamine infusion (0.5 -2 microg x kg x min(-1)) was associated with enhanced hemodynamic function (MAP 65 +/- 5.5 vs 92 +/- 5.7 mm Hg, P = <0.05) only during the period of aortic cross clamping. However, during the most part of infrarenal abdominal aortic surgery, dopexamine did not reduce systemic vascular resistance index, mean arterial pressure nor oxygen extraction compared with the control group. The lactulose/ rhamnose permeation ratio was elevated above normal in both groups (0.22 and 0.29 in groups I and II respectively). CONCLUSIONS: Dopexamine infusion (0.5 -2 microg x kg(-1) x min(-1)) did not enhance hemodynamic function and tissue oxygenation values during elective infrarenal abdominal aortic aneurysm repair.     

Winner of the ESVS Prize 1988. Effects of prostaglandin E1 (PGE1) on experimental renal ischaemia

A persisting incidence of acute renal failure has been observed after operative treatment of thoracoabdominal aortic aneurysm, ruptured abdominal aortic aneurysm and renal artery occlusive disease in patients with preoperative impairment of renal function. Because preservation of kidney function can play an important role in the outcome of these patients, the effects of prostaglandin E1 (PGE1) to prevent ischaemic renal failure were studied in an experimental model. Twenty dogs were exposed to 3 h warm ischaemia by clamping of the supra- and infrarenal aorta and both renal arteries. In 10 dogs PGE1 was given intravenously (100 ng/kg/min) for 15 min before clamping. Ten dogs treated with normal saline served as controls. Glomerular filtration rate, renal plasma flow, plasma creatinine, blood urea nitrogen, urine volume, free water clearance and renovascular resistance were calculated before and after renal ischaemia for both groups. The dogs were followed-up for 2 weeks and radionuclide studies with Tc-99m-MAG3, I-131-OIH and In-113m-DTPA were performed on the third postoperative day to calculate global and split renal clearance, tracer extraction fraction and mean transport time. After renal ischemia 9 dogs of the control group and 3 dogs of the PGE1-group developed acute renal failure (P less than 0.05 due to Fisher's exact text). PGE1 infusion significantly attenuated the postischaemic fall in glomerular filtration rate and renal concentrating ability as well as the postischaemic increase of plasma creatinine and blood urea nitrogen induced by 3 h warm renal ischaemia (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Renal perfusion with venous blood extends the permissible suprarenal clamp time in abdominal aortic surgery

OBJECTIVE: Suprarenal clamping in abdominal aortic surgery is associated with a significant risk of postoperative renal failure, general morbidity, and mortality. Arterial access for temporary shunting in these patients is difficult, and arterial perfusion techniques are typically complex. This study evaluated if renal perfusion with venous blood using a minimal pump setup and intermediate-level heparinization prevents a decline in postoperative renal function in patients requiring suprarenal clamping for aortic reconstructive surgery. METHODS: Renal perfusion was achieved using a roller pump supplied with venous blood from a central venous catheter under medium-level heparinization to feed two perfusion balloon catheters. The calculated glomerular filtration rate was observed for 10 postoperative days and compared with the rate in patients with suprarenal clamping without renal perfusion. RESULTS: From 2001 to 2007, 158 patients underwent surgical reconstruction involving the pararenal aorta through a midline abdominal incision. Renal perfusion was started in 2006 and was always attempted if suprarenal clamping was anticipated preoperatively. Twenty-six patients received renal perfusion, and 132 also requiring suprarenal clamping did not. Of the latter, 109 were included in the control group. Five patients died 相似文献   

Suprarenal aortic cross-clamping in elective abdominal aortic aneurysm surgery.

INTRODUCTION: this retrospective study was undertaken to evaluate whether suprarenal aortic cross-clamping increased the perioperative mortality and morbidity as compared to infrarenal clamping, in order to create the rationale for a more extensive application of this apparently more traumatic manoeuvre. MATERIALS AND METHODS: in a series of 734 elective aortic substitutions for abdominal aneurysm (AA), performed consecutively from January 1992 to June 1999, aortic cross-clamping was performed at a suprarenal level in 56 juxtarenal aneurysms, i.e. aneurysms extending to the lower edge of the renal arteries (8%, Group 1), and at an infrarenal level in 634 subrenal aneurysms (92%, Group 2). When analysing preoperative data, the diameter of aneurysms was larger in Group 1 than in Group 2 (p<0. 005). No significant differences were found between the two groups as regards age, sex, postinfarction cardiomyopathy, chronic obstructive pulmonary disease, chronic renal insufficiency and ASA classification of operative risks. RESULTS: the average time of renal exclusion in the juxtarenal aneurysms was 20 min (range 12-35 min). There is no difference between the two groups as regards the time of aortic clamping (mean 50 vs. 60 min) or the need for homologous blood transfusion (7% vs. 11% of patients). Perioperative (30 days) mortality did not differ: 3.6% vs. 1.9% (n.s.); nor did the incidence of acute myocardial infarction (3.6% vs. 2.3%). Renal function deteriorated in 8 (14%) vs. 0 (0%) (p<0.001) and 1 patient (2%) required permanent dialysis, as compared to 0% in Group 2. The incidence of ischaemic colitis was also significantly higher in Group 1 (7%) than in Group 2 (2%, p<0.01). CONCLUSION: this data shows that suprarenal clamping, which is necessary for the radical treatment of juxtarenal aortic aneurysms, can be performed with a low risk.     

Extraperitoneal laparoscopic aortic control with endovascular visualization of a stent-graft combination.

OBJECTIVES: to demonstrate the feasibility of minimally invasive approaches to the aorta using retroperitoneal laparoscopy and to clamp the aorta to give views for perfemoral aortic angioscopy. METHODS: using retroperitoneal laparoscopy facilitated by balloon dissection the authors developed a new approach to the infrarenal abdominal aorta, in six pigs, to allow control of aortic blood flow. Aortic stent-grafts were then deployed via femoral arteriotomy, and after flushing the blood from the aorta, the stent-grafts were visualized by angioscopy. RESULTS: accurate positioning and patency of the stent-grafts was ascertained by direct vision angioscopy in all cases. CONCLUSIONS: this series shows that extraperitoneal laparoscopic aortic dissection is feasible and direct endovascular visualization of the aortic lumen can be performed. This may find a role as an adjunct to endovascular techniques such as endovascular stent-graft placement, by aortic angioscopy following minimally-invasive aortic clamping.     

Technical and operative factors in infrarenal aortic reconstruction and their effect on the glomerular filtration rate in the immediate postoperative period and 6 months later

Renal failure is an important cause of postoperative morbidity and mortality in infrarenal aortic reconstruction. Several mechanisms for this postoperative renal dysfunction have been suggested. However, biochemical testing of renal function is insensitive since it shows only gross renal changes. This study examined prospectively the effects of the technical and operative factors on renal function using radionuclide tests. The authors measured the total Glomerular Filtration Rate (GFR) using 51Cr-EDTA clearance in 59 patients undergoing elective infrarenal aortic reconstruction. We also examined the individual kidneys using 99mTc-DTPA renography and 99mTc-DMSA renal scanning. Renal scanning gives the percentage of function of each kidney, while renography gives a graphic assessment of individual renal perfusion and clearance. All tests were carried out preoperatively, 2 weeks postoperatively and 6 months later. Twelve technical factors including aortic cross clamping time, type of aortic anastomosis, forced diuresis, division of left renal vein and various others were recorded to study their effect on the GFR and the individual kidney function. The effect on renal function of these operative factors has not previously been described. GFR showed no change in the immediate postoperative period. Six months later GFR decreased, the mean decrease was 9 ml/min. (P = 0.007 Wilcoxon rank). Some of our patients showed an increased GFR, a phenomenon that was recognised recently. None of the factors studied, except division of the left renal vein, had any effect on the changes in the GFR in the immediate postoperative period or 6 months later.     

Influence of mannitol and dopamine on renal function during elective infrarenal aortic clamping in man

The impact of elective infrarenal aortic clamping on parameters of renal function was evaluated in 27 extracellular fluid volume expanded patients. Significant transient decreases (p less than 0.05) in glomerular filtration rate were observed in all three groups either in the early or late post-clamp release period, despite maintenance of hemodynamic stability. This study documents transient decreases in glomerular filtration rate which occurred following release of the infrarenal aortic cross-clamp. No clinically important benefit from the use of mannitol and dopamine over extracellular fluid volume expansion with saline alone was demonstrated in the prevention of the changes in renal function associated with aortic cross-clamping.     

Suprarenal clamping is a safe method of aortic control when infrarenal clamping is not desirable

We evaluated the safety of suprarenal aortic clamping in patients with abdominal aortic aneurysm (AAA) treated by open aortic replacement by retrospectively reviewing all patients who underwent elective AAA replacement at a university hospital from 1993 until 2003. We reviewed 249 patient charts and divided them into three groups according to the clamp location during aortic replacement: group 1, infrarenal clamp group (n = 185); group 2, suprarenal clamp group (n = 52); and group 3, supraceliac clamp group (n = 12). Groups 1 and 2 were compared with respect to risk factors, intraoperative events, and postoperative events. Statistical analysis was done using Wilcoxon's rank-sum test, chi-squared test, and Fisher's exact test. Risk factors were comparable in groups 1 and 2 except for weight, which was higher in group 1. Intraoperative urine output, hypotensive episodes, and use of renal protective drugs were comparable in the two groups. Operation time, blood loss, and use of IV fluids were all significantly higher in group 2, while total aortic clamp time was higher in group 1. Postoperative events were comparable except for postoperative peak creatinine, intensive care unit length of stay, and postoperative length of stay, which were higher in group 2; however, discharge creatinine was comparable without a significant difference. Suprarenal clamping is a safe method of aortic control during open AAA replacement surgery. The selection of clamping site should be individualized according to the intraoperative anatomy. Supraceliac clamping is not necessarily the preferable method of aortic control when the infrarenal location is not suitable for clamping.     

Heparinization in aortic surgery

A prospective study was conducted on 35 patients (25 males and 10 females) undergoing elective reconstructive aortic surgery to examine the heparin activity after a bolus dose of sodium heparin (100 U/kg) given five minutes prior to aortic cross clamping. Recording of heparin activity were made 15 minutes later, on release of the aortic clamp, at abdominal wound closure and hourly thereafter until minimal activity was reached. In 10 patients, protamine was used to reverse anticoagulation. These results were related to clinical parameters of age, renal function, plasma cholesterol, blood pressure, position of the aortic clamp and blood loss. High peak levels of heparin activity were more likely in patients with impaired renal function or high plasma cholesterol concentrations. Heparin activity was prolonged at therapeutic levels in patients with renal impairment, and in this group of patients the use of protamine was significantly increased as was the requirement for blood replacement.     

缺血预处理对脊髓缺血损伤细胞内Ca2+变化的影响

目的　观察缺血预处理对脊髓缺血损伤细胞内 Ca2 变化的影响。　方法　将 44只健康新西兰大白兔随机分为三组 :缺血组 2 0只 ,缺血预处理组 2 0只 ,假手术组 4只。缺血组于左肾动脉下夹闭腹主动脉 40分钟后开放灌注 ;缺血预处理组夹闭腹主动脉 5分钟 ,开放 15分钟 ,再次夹闭 40分钟后开放再灌注 ;假手术组动物手术操作同缺血组 ,但不夹闭腹主动脉。分别于夹闭 40分钟后即刻、开放再灌注 2小时、8小时、2 4小时和 72小时各时相点测定脊髓组织 Ca2 含量 ,并评定、记录动物后肢神经功能。　结果　缺血预处理组脊髓组织 Ca2 显著低于缺血组各时相值 ;再灌注 8小时后神经功能评分缺血预处理组明显高于缺血组 (P<0 .0 1)。　结论　缺血预处理具有降低神经元胞浆游离 Ca2 浓度 ,防止Ca2 超载 ,稳定细胞内环境的能力 ,对主动脉阻断所致的脊髓缺血损伤有良好的保护作用。其表现为明显降低瘫痪发生率 ,增加术后神经评分     

Aortic clamping during elective operations for infrarenal disease: The influence of clamping time on renal function

OBJECTIVE: Aortic clamping proximal to the renal arteries is sometimes necessitated during infrarenal and juxtarenal aortic surgery and may be associated with an increased risk of renal ischemia and its consequences. The aim of the study was to estimate this risk and possibly identify a "safe" duration of renal ischemia. METHODS: Medical records were retrospectively reviewed for 60 consecutive patients (from 1987 to 1994) with abdominal aortic aneurysm (n = 43) and occlusive disease (n = 17) confined to the infrarenal or juxtarenal aorta who underwent infrarenal aortic reconstruction with temporary suprarenal clamping. The data obtained included risk factors, preoperative and postoperative serum creatinine level, blood urea nitrogen (BUN) value, proteinuria before surgery, and suprarenal clamping times. RESULTS: The mean age of the patients was 64.4 years (+/- 11.4 years), and 74% were men. Concomitant cardiac disease was present in 41% of the patients, and 9% had diabetes. The preoperative creatinine level was 1.21 mg/dL (+/- 0.54 mg/dL), and the BUN value was 16.6 mg/dL (+/- 7.8 mg/dL). During surgery, blood flow to the renal arteries was interrupted for 32.0 minutes (+/- 17 minutes). None of the surviving patients needed dialysis or had signs of acute renal failure after the operations, but transient azotemia (rise in creatinine level) occurred in 23% of the patients. Risk factors for this condition were high preoperative creatinine values and hypotension during surgery, but the main determinant was total renal ischemia time. Odds ratios for such transient renal dysfunction showed as much as a 10-fold risk when suprarenal aortic clamping was greater than 50 minutes as compared with 30 minutes or less. CONCLUSION: Postoperative renal function impairment is rare in this group of patients. If suprarenal clamp duration (renal ischemia time) is brief, patients with normal preoperative creatinine levels exhibit no increase or a marginal increase in BUN or creatinine levels after surgery. Accordingly, suprarenal aortic clamping less than 50 minutes in this patient group appears safe and well tolerated.