The effect of infrarenal aortic reconstruction on glomerular filtration rate and effective renal plasma flow.

Compromised patients with aortic disease are vulnerable to various complications from aortic reconstruction. These complications are related to changes in systemic haemodynamics during aortic cross-clamping, which leads to cardiac stress and alteration in regional blood flow to different organs. One of the most important postoperative complications is renal failure which is associated with a high mortality rate. Circulatory alterations within the kidney must play a role in the pathogenesis of renal dysfunction that may follow infrarenal aortic cross-clamping and reconstruction. To study the effects of abdominal aortic reconstruction on renal function and perfusion, we measured prospectively the glomerular filtration rate (GFR, n = 59), effective renal plasma flow (ERPF, n = 38) and left ventricular ejection fraction (LVEF, n = 38) in patients undergoing elective infrarenal aortic reconstruction. Radionuclide techniques were used. The three parameters were measured at three time points: preoperatively, postoperatively and 6 months after surgery. The LVEF was measured in order to reflect the patient's cardiac status and pre-renal perfusion. We also measured the three parameters in two control groups of patients: a group of patients undergoing major colonic surgery and a group of patients with arterial disease under conservative management. Six months after surgery the GFR had decreased in 67% of aortic reconstruction patients. Overall GFR in the aortic reconstruction group decreased by a mean of 9 ml min-1 (p = 0.007). This was associated with a decrease in the ERPF in 48.5% of patients. The mean decrease in ERPF in the aortic reconstruction group was 74 ml min-1 (p = 0.05). The LVEF was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of suprarenal cross-clamping on abdominal aortic aneurysm repair.

Two hundred five patients who underwent elective abdominal aortic aneurysm repair were divided into two groups: those who underwent infrarenal cross-clamping alone (n = 166) and those who underwent suprarenal cross-clamping alone or combined with infrarenal cross-clamping (n = 39). Mortality was comparable between groups (1.2% for infrarenal cross-clamping vs 2.6% for suprarenal cross-clamping). Transient renal insufficiency was more frequent in the suprarenal group than in the infrarenal group (28% vs 10%), but dialysis rates (3% for suprarenal vs 2% for infrarenal) were similar. Cardiac morbidity was comparable between groups as well. Operating room data reflected the technical challenge of complex aneurysm repairs. The retroperitoneal approach was the preferred exposure in the suprarenal group since better access to the suprarenal aorta may be achieved with this technique. While abdominal aortic aneurysm repairs requiring suprarenal cross-clamping remain a technical challenge, the risks are not formidable and suprarenal cross-clamping should be considered when confronted with difficult periaortic dissection.     

The effects of fenoldopam on renal function in patients undergoing elective aortic surgery

BACKGROUND AND OBJECTIVE: Postoperative renal impairment is a recognized complication of infrarenal aortic cross-clamping. Our hypothesis was that the renal vasodilating and natriuretic effects of fenoldopam mesylate, a selective dopamine (DA1) agonist, would preserve renal function in patients undergoing elective infrarenal aortic cross-clamping. METHODS: A prospective, randomized, double blind controlled clinical trial was performed. Twenty-eight ASA II-III patients undergoing elective aortic surgery requiring infrarenal aortic cross-clamping were studied. According to random allocation, patients received either fenoldopam (0.1 microg kg(-1) min(-1)) or placebo intravenously prior to surgical skin incision until release of the aortic clamp. Plasma creatinine, creatinine clearance, urinary output, fractional excretion of sodium, and free water clearance were measured: (a) prior to admission to hospital; (b) during the period from insertion of the urinary catheter until application of the aortic cross-clamp; (c) during the period of aortic cross-clamping; (d) 0-4 h, and (e) 4-8 h after release of the clamp and on days 1, 2, 3, and 5 postoperatively. RESULTS: Fenoldopam (0.1 microg kg(-1)min(-1)) administration was not associated with haemodynamic instability. On application of the aortic cross-clamp creatinine clearance decreased significantly in the placebo (83 +/- 20 to 42 +/- 29 mL min(-1) (mean +/- SD)) (P < 0.01) but not in the fenoldopam group, and this decrease persisted for at least 8 h after release of the cross-clamp (83 +/- 20 to 54 +/- 33 mL min(-1) (mean +/- SD)) (P < 0.05). Plasma creatinine concentration increased significantly from baseline on the first postoperative day in the placebo group (87 +/- 12 to 103 +/- 28 micromolL(-1) (mean +/- SD)) (P < 0.01) but not in the fenoldopam group. CONCLUSIONS: These findings are consistent with the hypothesis that fenoldopam possesses a renoprotective effect during and after infrarenal aortic cross-clamping.     

Endogenous renal nitric oxide metabolism following experimental infrarenal aortic cross-clamp-induced ischaemia-reperfusion injury.

BACKGROUND: Abdominal aortic surgery is associated with marked changes in renal haemodynamics. The aim of this study was to investigate the influence of infrarenal cross-clamping on glomerular filtration rate and endogenous renal nitric oxide metabolism. METHODS: Groups of male Wistar rats were subjected to infrarenal aortic cross-clamping followed by reperfusion. Animals were allowed to recover after a left nephrectomy. The glomerular filtration rate of the remaining kidney was measured on the second and seventh day after the procedure before the animal was killed and the remaining kidney harvested. Total nitric oxide synthase (NOS) activity and expression of inducible NOS (iNOS) was determined in renal tissue following 1 h and 7 days of reperfusion. RESULTS: Glomerular filtration rate was impaired on the second and seventh day after operation in all animals subjected to lower torso ischaemia compared with controls (P < 0.05). Renal NOS activity was increased at 1 h and 7 days in animals subjected to infrarenal cross-clamping compared to controls (P < 0.01). iNOS was detected in renal tissue of animals subjected to infrarenal aortic cross-clamping on the seventh day after operation. CONCLUSION: Infrarenal aortic cross-clamping is associated with impairment of renal function in the early postoperative period. There is an increase in endogenous renal nitric oxide metabolism with iNOS expression. Presented in part to the Surgical Research Society, Dublin, Ireland, July 1998     

Transperitoneal versus retroperitoneal suprarenal cross-clamping for repair of abdominal aortic aneurysm with a hostile infrarenal aortic neck

Infrarenal abdominal aortic aneurysms (AAAs) with a hostile infrarenal aortic neck unfit for endovascular aneurysm repair (EVAR) are more likely to require open repair with suprarenal aortic cross-clamping. We compared the results of the transperitoneal versus retroperitoneal approaches for repair of infrarenal AAA requiring suprarenal cross-clamping and the relative frequency of such techniques after incorporating EVAR into our clinical practice. From January 1998 through September 2005, 478 elective infrarenal aortic aneurysms were repaired. There were 160 (33%) open repairs (71% transperitoneal and 29% retroperitoneal) and 318 (67%) endovascular repairs. In 38 cases (24%) suprarenal cross-clamping was performed (47% transperitoneal and 53% retroperitoneal incisions) for a hostile infrarenal neck. A hostile aortic neck was defined as severe angulation (>60 degrees ), short neck (<15 mm), extensive calcification, or circumferential thrombus. The median age was 70 years; 47% were men; 16% had diabetes mellitus, 29% pulmonary disease, 53% coronary artery disease, and 11% renal insufficiency. The median aneurysm size was 6.0 cm. A retrospective analysis was performed to compare 30-day postoperative outcomes between the trans- and retroperitoneal patient cohorts. The results were determined for two time periods to assess whether open repair with suprarenal cross- clamping was being performed more frequently as a result of increased utilization of EVAR in the contemporary period. After 2002, EVAR increased from 60% to 71% (p = 0.04) while open repair declined from 40% to 29% (p = 0.01). The retroperitoneal approach doubled from 19% to 39%, while the transperitoneal approach decreased from 81% to 61% (p = 0.02). Suprarenal cross-clamping increased by 11% after 2002. There was no significant difference in age, sex, aneurysm size, or comorbidities between the trans- and retroperitoneal groups with suprarenal cross-clamping. The 30-day mortality was 2/38 (5%) and occurred only in the transperitoneal group. The transperitoneal approach was associated with significantly greater blood loss and longer suprarenal cross-clamp times (2,400 vs. 1,800 mL and 38.0 vs. 29.5 min; p = 0.03), but there were no significant differences in 30-day postoperative complications. In our 7 years' experience, there has been a gradual increase in the utilization of EVAR for infrarenal AAAs. At the same time, more infrarenal AAAs with hostile aortic necks requiring suprarenal aortic cross-clamping were encountered. In such instances, the retroperitoneal approach is safer, with less perioperative blood loss and shorter suprarenal cross-clamp time. This is likely attributed to better exposure of the suprarenal abdominal aorta, allowing a more secure proximal anastomosis.     

Low cardiac output abolishes cardiovascular responses to infra-renal aortic cross-clamping in the pig

Background: Previous data suggest that preoperative myo-cardial dysfunction is associated with an altered cardiac response to infra-renal aortic cross-clamping (AXC). This study was designed to further explore how acute reductions in stroke volume and cardiac output influence the systemic, preportal and renal circulatory responses to AXC.
Methods: In chloralose-anesthetized normoventilated pigs, graded increases in pericardial pressure (P_PERICARD) were obtained by local infusions of dextran. Measurements included cardiac output (CO, thermodilution), mean blood pressure proximal to the aortic clamping site (MA_PROX) and ultrasonic flowmetry for portal (Q_PORT) and renal (Q_REN) blood flows. In all animals, measurements were made a) prior to AXC, b) at the end of a 5 min AXC period and, c) 5 min following dec-lamping. These recordings were repeated during control (P_PERICARD 0 cmH₂O) and during stages with increased P_PERICARD (4 and 8 mH₂O, respectively).
Results: Pericardial infusions of dextran produced hemody-namic responses that in magnitude were proportional to P_PERICARD levels. Stroke volume, CO and mean arterial pressure decreased, while systemic vascular resistance (SVR) increased.
Conclusions: AXC-induced systemic, preportal and renal circulatory responses are inhibited during a condition of acutely lowered cardiac output.     

Activation of fibrinolytic pathways is associated with duration of supraceliac aortic cross-clamping

PURPOSE: The cause of the coagulopathy seen with supraceliac aortic cross-clamping (SC AXC) is unclear. SC AXC for 30 minutes results in both clotting factor consumption and activation of fibrinolytic pathways. This study was undertaken to define the hemostatic alterations that occur with longer intervals of SC AXC. METHODS: Seven pigs underwent SC AXC for 60 minutes. Five pigs that underwent infrarenal aortic cross-clamping (IR AXC) for 60 minutes and 11 pigs that underwent SC AXC for 30 minutes served as controls. No heparin was used. Blood samples were drawn at baseline, 5 minutes before release of the aortic clamp, and 5, 30, and 60 minutes after unclamping. Prothrombin time, partial thromboplastin time, platelet count, and fibrinogen concentration were measured as basic tests of hemostatic function. Thrombin-antithrombin complexes were used to detect the presence of intravascular thrombosis. Fibrinolytic pathway activation was assessed with levels of tissue plasminogen activator antigen and tissue plasminogen activator activity, plasminogen activator inhibitor-1 activity, and alpha2-antiplasmin activity. Statistical analysis was performed with the Student t test and repeated measures of analysis of variance. RESULTS: Prothrombin time, partial thromboplastin time, and platelet count did not differ between groups at any time. Fibrinogen concentration decreased 5 minutes (P =.005) and 30 minutes (P =.006) after unclamping in both SC AXC groups, but did not change in the IR AXC group. Thrombin-antithrombin complexes increased in both SC AXC groups, but were not significantly greater than in the IR AXC group. SC AXC for both 30 and 60 minutes produced a significant increase in tissue plasminogen activator antigen during clamping and 5 minutes after clamping. This increase persisted for 30 and 60 minutes after clamp release in the 60-minute SC AXC group. Tissue plasminogen activator activity, however, increased only in the 60-min SC AXC group during clamping (P =.02), and 5 minutes (P =.05) and 30 minutes (P =.06) after unclamping, compared with both control groups. CONCLUSIONS: Thirty and 60 minutes of SC AXC results in similar degrees of intravascular thrombosis and fibrinogen depletion. Although SC AXC for both 30 and 60 minutes leads to activation of fibrinolytic pathways, only 60 minutes of SC AXC actually induces a fibrinolytic state. Fibrinolysis appears to be an important component of the coagulopathy associated with SC AXC, and is related to the duration of aortic clamping. CLINICAL RELEVANCE: The coagulopathy frequently associated with thoracoabdominal aortic aneurysm repair is thought to revolt visceral ischemia-reperfusion. The nature of this coagulopathy is controversial. The current study demonstrates that the major hemostatic alteration associated with supraceliac aortic cross-clamping is activation of fibrinolytic pathways. The magnitude of this fibrinolytic response is directly related to the duration of supraceliac aortic occlusion. Future efforts to treat this coagulopathy may well include judicious use of autofibrinolytic agents.     

Renal and splanchnic circulation during infrarenal aortic cross-clamping

The effect of infrarenal cross-clamping of the aorta on regional splanchnic and renal circulations was studied in seven dogs. Regional blood flow was determined with differentially labeled microspheres (9 and 15 micron in diameter) that were injected simultaneously into the left atrium. Blood flow was measured 30 minutes after surgical preparation was completed (stage I), 20 minutes after infrarenal aortic cross-clamping (stage II), and 20 minutes after supplemented sodium nitroprusside infusion (stage III). Infrarenal aortic cross-clamping was accompanied by a slight increase in the cardiac output (CO) without significant changes in mean arterial pressure (MAP). Blood flow through the gut, hepatic artery, and cortical layer of the kidneys, as determined with 15-micron spheres, was not changed. Nonentrapment of 9-micron spheres in the gut and renal cortex was increased substantially. Blood flow through the juxtamedullary layer of the kidneys was increased. Sodium nitroprusside supplementation decreased MAP by 30%; CO values returned to baseline level. Hepatic artery blood flow, compared with both baseline values and values during aortic cross-clamping, increased significantly. Blood flow, determined with 15-micron spheres, through the gut and renal cortex did not change, and nonentrapment of 9-micron spheres decreased to baseline values. The data suggest a certain shift of blood flow to the juxtamedullary layer of the kidneys during aortic cross-clamping and normalization of intrarenal blood flow distribution during supplemented sodium nitroprusside infusion. Controlled vasoplegia with sodium nitroprusside may help modify peripheral circulatory disturbances in the kidneys and splanchnic system during infrarenal aortic cross-clamping.     

Appraisal of cerebrospinal fluid alterations during aortic surgery with intrathecal papaverine administration and cerebrospinal fluid drainage

We have previously described a technique for intrathecal administration of papaverine and cerebrospinal fluid drainage to prevent paraplegia after aortic surgery. Herein we report the cerebrospinal fluid and hemodynamic alterations that occurred in 11 patients who had 30 mg of a specially prepared papaverine hydrochloride 10% dextrose solution injected before aortic cross-clamping and also had cerebrospinal fluid drainage. A mean of 26.6 ml (SD +/- 7.1 ml) was drained before and 34.6 ml (SD +/- 24.1 ml) was drained during aortic cross-clamping. The cerebrospinal fluid pressure increased significantly with anesthetic induction (p less than 0.03), during the period between anesthetic induction and cerebrospinal fluid drainage (p less than 0.005), and with aortic cross-clamping (p less than 0.05). These cerebrospinal fluid pressure alterations were similar to central venous pressure increases with a significant linear correlation between cerebral spinal fluid pressure and central venous pressure before anesthetic induction (r2 = 0.81, p less than 0.005), and both before (r2 = 0.94, p less than 0.005) and after (r2 = 0.74, p less than 0.005) aortic cross-clamping. As expected, cerebrospinal fluid pressure was significantly reduced by cerebrospinal fluid drainage before aortic cross-clamping (p less than 0.001). The administration of intrathecal papaverine had no significant effect on mean arterial pressure, systemic vascular resistance, cerebrospinal fluid pressure, nor the pH of cerebrospinal fluid. Neither were there any complications noted related to the technique. All the patients survived, and no new immediate postoperative paraparesis or paraplegia occurred.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stroke in surgery of the arteriosclerotic descending thoracic aortic aneurysms: influence of cross-clamping technique of the aorta.

OBJECTIVE: The risk of stroke caused by dislodgment of loose atheromatous plaque or mural emboli is increased by cross-clamping of the aorta. Some patients undergo descending thoracic aortic aneurysm repair with proximal aortic cross-clamping between the left common carotid artery and the left subclavian artery. The objective of this study was to determine the influence of proximal aortic cross-clamping in arteriosclerotic aneurysm or dissecting aneurysm repair. METHODS: Between May 1984 and May 2003, 81 patients underwent elective surgery for distal arch or descending aortic aneurysm repair with proximal aortic cross-clamping between the left common carotid artery and the left subclavian artery. To evaluate the influence of the proximal aortic cross-clamping, patients were divided into two groups: patients who had undergone arteriosclerotic aneurysm repair (group I, n=25) and patients who had undergone dissecting aneurysm repair (group II, n=56). RESULTS: Eight (9.9%) of the 81 patients had a stroke. Six strokes occurred in operations for arteriosclerotic aneurysm repair group I and two strokes occurred in operations for dissecting aneurysm repair group II (24 vs 3.6%; p=0.009). In-hospital mortality rates were 12% in group I and 8.9% in group II (p=0.70). Major postoperative complications included renal failure requiring hemodialysis (in 4.2% of the patients in group I and in 8.3% of the patients in group II, p=0.99) and pulmonary complication (in 20% of the patients in group I and in 16% of the patients in group II, p=0.67). CONCLUSION: Cross-clamping between head vessels should be avoided if at all possible when operating on patients who have arteriosclerotic descending thoracic aneurysms.     

Cardiovascular and catecholamine responses during endovascular and conventional abdominal aortic aneurysm repair.

OBJECTIVES: To compare changes in plasma catecholamines, acid-base status and cardiovascular dynamics in patients undergoing endovascular or conventional infrarenal abdominal aortic aneurysm (AAA) repair under standard general anaesthesia. DESIGN: Prospective cohort study. MATERIALS: 30 patients scheduled for elective infrarenal AAA repair. METHODS: Plasma epinephrine and norepinephrine concentrations, acid-base status and cardiovascular measurement were compared before surgery, and 5 min after aortic clamping and clamp release (conventional group) or occlusion and release (endovascular group) in patients undergoing endovascular (n = 15) or conventional AAA repair (n = 15). RESULTS: Arterial pH (p < 0.005) and base deficit (p < 0.05) increased, and plasma bicarbonate decreased (p < 0.005) during aortic cross-clamping in the conventional group. pH decreased further (p < 0.005), and base deficit and pCO2 increased (both p < 0.005) after clamp release. These changes were significantly greater than during endovascular repair, in whom within-group changes were not statistically significant. Values were similar in the two groups 30 min after reperfusion. Plasma epinephrine concentrations increased during conventional surgery (p < 0.05) and were greater than in the endovascular group (p < 0.05). Plasma norepinephrine concentrations increased during surgery in both groups but the changes were not statistically significant. CONCLUSIONS: Plasma catecholamine concentrations, changes in cardiovascular variables and acid-base status were increased during conventional compared with endovascular AAA repair.     

Monitoring of end-tidal carbon dioxide partial pressure changes during infrarenal aortic cross-clamping: a non-invasive method to predict unclamping hypotension

BACKGROUND: To assess the variations in end-tidal CO2 in response to aortic cross-clamping and the relationship with systolic arterial pressure (SAP) changes induced by unclamping. METHODS: Thirty-three patients undergoing infrarenal aortic abdominal aneurysm repair by aorto-aortic prothetic bypass were prospectively studied. All patients were anesthetized with i.v. midazolam (0.05 mg x kg(-1)), thiopentone (3-5 mg x kg(-1)), fentanyl (5 microg x kg(-1)), pancuronium (0.1 mg x kg(-1)) and the maintainance of anesthesia used was 1-1.5% end-tidal isoflurane and i.v. fentanyl. The perioperative management was standardized. End-tidal CO2 and SAP were measured 5 min before (Pre-XAA), 15 min after infrarenal aortic cross-clamping (XAA), 5 min before (Pre-UXAA) and immediately after unclamping (UXAA). RESULTS: A total of 16 (48.5%) from 33 patients presented decrease in SAP following aortic unclamping, and 13 out of these patients had arterial hypotension defined as SAP<90 mmHg. End-tidal CO2 variation (PreXAA-PreUXAA) induced by aortic clamping was correlated with SAP variation (PreUXAA-UXAA) induced by unclamping (r=0.763; P=0.0001). An end-tidal CO2 reduction above 15% after aortic cross-clamping was found to have a 100% sensitivity to detect a SAP decrease greater than 20% after unclamping, with a 100% specificity and a negative predictive value of 1.0. Complete aortic occlusion duration was not correlated to SAP unclamping variation (deltaSAP). Intraoperative characteristics (fluid loading, hematocrits, urinary output) were comparable, although blood loss was higher in patients experiencing deltaSAP>20%. CONCLUSIONS: End-tidal CO2 variation monitoring during aortic cross-clamping may provide a reliable and non-invasive method to predict unclamping hypotension. When the aortic clamp was released, systolic hypotension (>20%) occurred in those subjects who had a decrease in end-tidal CO2 greater than 15% during aortic cross-clamping.     

Mechanisms of renal hemodynamic impairment during infrarenal aortic cross-clamping.

Infrarenal aortic cross-clamping is associated with impairment of renal hemodynamics due to vasoconstriction, the mechanism of which remains under debate. To assess the renal effect of two potent renal vasodilators (enalapril, a converting enzyme inhibitor, and nicardipine, a calcium antagonist), 24 patients scheduled for reconstructive aortic surgery were randomly allocated to one of three treatment groups (n = 8 each) and received either a placebo, nicardipine, or enalapril. Anesthesia consisted of flunitrazepam, fentanyl, pancuronium, and, occasionally, droperidol. Although aortic cross-clamping was associated with no change in mean arterial blood pressure, decreased cardiac output and increased systemic vascular resistance occurred in control patients (33% and 43%, respectively, both P less than 0.05 versus baseline) and nicardipine-treated patients (51.7% and 67.7%, respectively, both P less than 0.05 versus baseline); however, changes in cardiac output and systemic vascular resistance failed to reach significance in enalapril-treated patients. Glomerular filtration rate (technetium 99-diethylenetriaminepentacetic acid clearance) and effective renal plasma flow (iodo-Hippuran 131 clearance) decreased for the duration of aortic cross-clamping in control patients (42.9% and 18.5%, respectively, both P less than 0.05 versus baseline) and enalapril-treated patients (34.0% and 38.1%, respectively, both P less than 0.05 versus baseline), but no change was observed in nicardipine-treated patients. These results suggest that the reninangiotensin system is not an important determinant of the renal vasoconstriction associated with aortic cross-clamping. In contrast, renal dysfunction may be alleviated by the dihydropyridine derivative nicardipine, which probably acts at the level of the preglomerular resistance vessels.     

A prolonged spinal cord ischaemia model in pigs. Passive shunting offers stable central haemodynamics during aortic occlusion.

OBJECTIVES: to evaluate the effect of a modified aortic shunt on central haemodynamic variables during experimental thoracic aortic occlusion in a prolonged spinal cord ischaemia model. MATERIAL AND METHODS: central haemodynamic variables were evaluated during aortic cross-clamping. In the shunt group (n=11), after the placement of proximal and distal aortic clamps, distal aortic perfusion was restored through an aortoiliac shunt via the left subclavian artery. In the no-shunt group (n=11), spinal cord ischaemia was achieved with only proximal aortic cross-clamping. The clamping time was 60 minutes in the shunt group and 30 minutes in the no-shunt group. RESULTS: in the no-shunt group, all animals needed inotropic support, vasodilators and buffers during the experiment. None of these drugs were needed in the shunt group. In the no-shunt group, cross-clamping caused a significant increase in mean arterial pressure and heart rate compared to baseline values. These variables were stable in the shunt group during aortic occlusion. In the reperfusion period cardiac output, heart rate and arterial pCO(2)were significantly higher in the no-shunt than in the shunt group. CONCLUSION: the present experimental spinal cord ischaemia model, using double aortic cross-clamping with shunt, offers improved central haemodynamics. This enables the study of prolonged selective spinal cord ischaemia without interaction from vasoactive drugs or systemic reperfusion.     

Lazaroid reduces production of IL-8 and IL-1 receptor antagonist in ischemic spinal cord injury

BACKGROUND: 21-aminosteroids (lazaroids) have demonstrated the protective effect against cerebral ischemic injury through the inhibition of lipid peroxidation. We examined whether lazaroids affected the production of proinflammatory and antiinflammatory cytokines in ischemic spinal cord injury model. MATERIALS: Anesthetized New Zealand white rabbits underwent a 20-minute infrarenal aortic cross-clamping (AXC) with pretreatment of either an intravenous 3 mg/kg lazaroid U74389G (group L; n = 10) or the same volume saline (group P; n = 10). Sham operation group (group S; n = 6) underwent only exposure of the aorta. Plasma concentrations of interleukin (IL)-8, -1beta, -1 receptor antagonist (IL-1ra) and tumor necrosis factor (TNF)-alpha were measured at four time points. Functional assessment with Tarlov score at 24 and 48 hours after pretreatment, pathologic assessment of the spinal cord, and measurements of cytokine levels in the spinal cord were performed. RESULTS: The maximum elevation of plasma IL-8 and -1ra levels occurred at 1 hour after declamping in four measurement points. Plasma IL-8 and -1ra levels in group L were significantly lower than those in group P (*p < 0.05). Plasma TNFalpha peaked at 5 minutes after declamping, but decreased afterwards. Plasma TNFalpha levels were not different among three groups. Spinal IL-8 levels in group L (0.98 +/- 0.34 ng/g tissue) were lower than those in group P (7.26 +/- 2.26 ng/g tissue)(*p < 0.05). Spinal IL-1ra and TNFalpha were not significantly different. Tarlov score and pathologic assessment were better in group L. CONCLUSIONS: Lazaroid U-74389G reduced the production of systemic IL-8 and -1ra and spinal IL-8 when AXC caused spinal cord injury. These results indicate that lazaroids may attenuate ischemic endothelial cell injury or activation of leukocytes.     

Phlebotomy reverses the hemodynamic consequences of thoracic aortic cross-clamping: relationships between central venous pressure and cerebrospinal fluid pressure

In dogs (n = 11) anesthetized with sodium pentobarbital (to an isoelectric EEG), the authors investigated the influence of thoracic aortic cross-clamping (AXC) on systemic hemodynamics and cerebrospinal fluid pressure (CSFP) with concurrent measurement of total brain flow (tCBF) and regional (cervical, thoracic, and lumbar) spinal cord blood flow (SCBF). The effect of phlebotomy (to control the hemodynamic consequences of AXC) on tCBF and SCBF was assessed. Radioactive microspheres were injected at four time periods in each animal: 1) at baseline; 2) with application of the AXC; 3) after phlebotomy, to reduce the proximal mean arterial pressure (MAPp) to baseline values; and 4) 2 min after removal of the AXC (mean AXC time 68 +/- 6 min). With application of the AXC, the MAPp, central venous pressure (CVP), and CSFP significantly increased (104 +/- 6 to 156 +/- 6 mmHg, 3.4 +/- 0.4 to 5.2 +/- 0.7 mmHg, and 3.3 +/- 0.7 to 5.2 +/- 0.8 mmHg, respectively), while distal mean aortic pressure (MAPd) significantly decreased (98 +/- 6 to 14 +/- 1 1 mmHg). Phlebotomy (24 +/- 3 ml.kg-1) significantly decreased MAPp (to 106 +/- 6 mmHg), CVP (to 1.6 +/- 0.6 mmHg), and CSFP (to 1.2 +/- 1.1 mmHg). The CSFP changed in parallel with the changes in CVP, a result suggesting that the alterations in CSFP depended on cardiac preload. The spinal cord perfusion pressure (SCPP; SCPP = MAPd - CSFP) was unchanged after phlebotomy, since both MAPd and CSFP decreased. The tCBF and cervical SCBF were unchanged when MAPp increased by 50% with application of the AXC; this indicated that autoregulation was intact.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Effect of intra-aortic magnesium on renal function during and after abdominal aortic surgery: a pilot study

BACKGROUND: Infrarenal aortic cross-clamping causes renal vasoconstriction. Magnesium may protect against renal deterioration through its vasodilatory properties. METHODS: Thirty patients with normal preoperative renal function undergoing infrarenal aortic cross-clamping for elective aortic surgery received magnesium (4 mmol) or saline into the aorta immediately after aortic cross-clamping and again just before unclamping in a double-blind fashion. Pulmonary artery occlusion pressure was maintained 215 mmHg. Five patients with magnesium were excluded due to need for intravenous nitroglycerine because of myocardial ischaemia during the study. RESULTS: Postoperative creatinine clearance remained unchanged in both groups. Urinary N-acetyl-beta-D-glucosaminidase excretion increased before and decreased after aortic cross-clamping in both groups. The concentrations of glutathione peroxidase in serum were identical between the two groups. CONCLUSIONS: These data indicate that intra-aortic magnesium had no effect on renal function during or after aortic cross-clamping.     

Surgical treatment of thoracoabdominal aortic aneurysm after repairs of descending thoracic or infrarenal abdominal aortic aneurysm.

OBJECTIVE: The outcome of thoracoabdominal aortic aneurysm repair after operations for descending thoracic or infrarenal abdominal aortic aneurysm was investigated. METHODS: Between May 1982 and July 2000, 102 patients underwent thoracoabdominal aortic aneurysm repair. Of these patients, 36 had previously undergone operations for descending thoracic or abdominal aortic aneurysm. To evaluate the influence of previous descending thoracic or infrarenal abdominal aortic aneurysm repair on the results of TAAA replacement, patients were divided into two groups: one group of patients who had previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group I, n=36) and one group of patients who had not previously undergone descending thoracic or infrarenal abdominal aortic aneurysm repair (group II, n=66). RESULTS: Patients with previous descending thoracic or infrarenal abdominal aortic aneurysm repair had more chronic dissection and extensive thoracoabdominal aortic aneurysm. The distal aortic perfusion time and total aortic clamp time were both longer in group I. The total selective visceral and renal perfusion time and operation time did not differ significantly between the two groups. In 30-day mortality rates were 5.5% in group I and 13% in group II. Major postoperative complications included paraplegia in 14% of patients in group I and 3.1% in group II, renal failure requiring hemodialysis in 22% of patients in group I and 19% of patients in group II, respiratory failure in 36% of patients in group I and 30% of patients in group II, postoperative hemorrhage in 11% of patients in group I and 16% of patients in group II. CONCLUSION: The presence of a previous descending thoracic or infrarenal abdominal aortic aneurysm did not adversely affect the outcome of thoracoabdominal aortic aneurysm repair.     

Does choice of the anesthetic influence renal function during infrarenal aortic surgery?

Reconstructive infrarenal aortic surgery is associated with impairment of renal function owing to vasoconstriction during and after aortic cross-clamping. To assess the influence of anesthetic technique on renal hemodynamics during aortic surgery, 34 patients received one of four anesthetics: isoflurane (n = 10), halothane (n = 9), droperidol (n = 8), and flunitrazepam (n = 7). Supplemental anesthesia consisted of midazolam, fentanyl, nitrous oxide in oxygen (50%), and pancuronium. Before aortic cross-clamping, effective renal plasma flow (ERPF) (131iodohippuran clearance) and glomerular filtration rate (GFR) (99technetium-DTPA clearance) were low in the halothane and flunitrazepam groups (118.4 +/- 25.6 and 170 +/- 35 mL/min for ERPF; 19.7 +/- 5.2 and 26.9 +/- 5.8 mL/min for GFR, respectively) and better preserved in the isoflurane group (253.4 +/- 51.5 and 44.9 +/- 8.4 mL/min, respectively; P less than 0.05 between isoflurane and halothane groups) or in the droperidol group as regards GFR (75.4 +/- 9.4 mL/min, P less than 0.05). During clamping, both renal variables were not markedly affected in any group except in the droperidol group in whom GFR significantly decreased from preclamp value. The GFR was then significantly higher in the isoflurane group (49.5 +/- 9.2 mL/min) than in the halothane and flunitrazepam groups (14.8 +/- 3.7 and 26.5 +/- 10.1 mL/min, respectively; P less than 0.05). After aortic declamping, ERPF and GFR increased markedly in the halothane group, and there was no significant difference between the groups. These results suggest that renal hemodynamics are less altered with droperidol-fentanyl anesthesia during abdominal surgery but not during aortic cross-clamping.(ABSTRACT TRUNCATED AT 250 WORDS)