Assessment of gut mucosal perfusion and colonic tissue blood flow during abdominal aortic surgery with gastric tonometry and laser Doppler flowmetry

The objective of this study was to investigate the effect of infrarenal aortic cross-clamping and unclamping on gut mucosal perfusion by gastric tonometry and on sigmoid colonic tissue blood flow by laser Doppler flowmetry during abdominal aortic surgery. This was a prospective before-and-after intervention comparison study in a university hospital of 8 male patients, aged 57-87, undergoing elective infrarenal abdominal aortic surgery. Each patient was pretreated with ranitidine. Following general anesthesia, a nasogastric tonometer was inserted into the stomach. The balloon of the tonometer was filled with 2.5 mL of normal saline for gas tension and pH analysis. This process was repeated before and after aortic cross-clamping and unclamping. Gastric mucosal pHi was calculated with the Henderson-Hasselbalch equation from the arterial Hco3- and the tonometrically measured mucosal Pco2. A laser Doppler flow probe was placed in contact with the serosa of the sigmoid colon against the mesentery after the abdomen was opened. Sigmoid colonic tissue blood flow (SCBF) was assessed by the laser Doppler flowmeter. Gastric mucosal pHi by gastric tonometry and colonic tissue blood flow by laser Doppler flowmetry were measured before and after aortic cross-clamping and unclamping. Gastric mucosal pHi decreased significantly 30 minutes after aortic cross-clamping (7.37 +/-0.07) (p < 0.01), 60 minutes after aortic cross-clamping (7.39 +/-0.08) (p < 0.05), and 30 minutes after aortic unclamping (7.37 +/-0.08) (p < 0.01), compared with pHi before aortic cross-clamping (7.50 +/-0.06). Gastric mucosal pHi increased to the original level 60 minutes after aortic unclamping (7.46 +/-0.08). Since a gastric mucosal pH above 7.35 is considered normal, these mean values of pHi were clinically insignificant. However, gastric mucosal pHi decreased below 7.32 in 5 patients during abdominal aortic surgery. Gastric mucosal pHi decreased further to 7.30 in 1 patient following aortic cross-clamping and below 7.30 in 3 patients 30 minutes after aortic unclamping. SCBF decreased significantly after aortic cross-clamping (28.1 +/-4.8 mL/min/100 g) compared with the value before aortic cross-clamping (51.9 +/-11.3 mL/min/100 g) (p < 0.01). Following aortic unclamping, SCBF returned to 41.7 +/-7.4 mL/min/100 g. It is concluded that transient episodes of significant intestinal mucosal ischemia may have been encountered occasionally in patients undergoing abdominal aortic surgery, but a sigmoid colonic tissue blood flow of 41.7 +/-7.4 mL/min/100 g was sufficient to prevent postoperative ischemic colitis regardless of whether there was ligation or no ligation of inferior mesenteric artery among the studied population since none of the patients developed clinically significant ischemic colitis.     

Reference values of gastric intramucosal pH in children

To determine the reference values of gastric intramucosal pH (pHi) by tonometry in paediatric patients, we studied 17 children (nine males, eight females) with no systemic or gastrointestinal disease, aged six months to 12 years undergoing minor reconstructive surgery. Following anaesthetic induction a sigmoid tonometry catheter was inserted (Tonometrics, Inc.) into the stomach of the patients under direct vision. All children were normoventilated and were haemodynamically stable. After an equilibration period of 30 min, gastric pHi was calculated by applying the Henderson-Hasselbalch equation on the Pco ₂ obtained with the tonometer and the bicarbonate from the arterial blood gas analysis. The mean gastric pHi in our patients was 7.35±0.06 (sd ). The normal pHi in the general population is estimated to be 7.31–7.40, with a confidence interval of 99%. No correlation was found between pHi and arterial pH, bicarbonate or base excess. Under conditions of normal ventilation and haemodynamic stability, healthy children during general anaesthesia have gastric intramucosal values similar to those of adults.     

Perioperative mucosal pH and splanchnic endotoxin concentration in orthotopic liver transplantation

Although impairment of splanchnic perfusion may induce mucosal hypoxia and endotoxaemia during orthotopic liver transplantation (OLT), little is known about the changes in mucosal oxygenation during and after the procedure. To study the effects of liver surgery itself on mucosal pH (pHi) and the response of pHi to acute changes in portal flow, we measured gastric pHi during six liver resections using tonometry: in two patients, after clamping of the hepatoduodenal ligament, pHi decreased within 30 min and recovered promptly after reperfusion. We then investigated gastric and sigmoid pHi (pHig, pHis) during the perioperative phase in 18 OLT. Median pHi values were low before surgery (pHig 7.28 (first/third quartiles 7.22/7.34); pHis 7.27 (7.12/7.36)). Although global oxygen delivery and haemodynamic variables remained constant and veno-venous bypass (VVB) was used to maintain portal flow, pHi declined during the anhepatic phase (pHig 7.19 (7.13/7.23), P < 0.01; pHis 7.13 (7.06/7.24), P < 0.05). After reperfusion of the graft, pHi recovered and did not differ from baseline values by the end of OLT. After operation pHig increased further, reaching the highest values 30 h after ICU admission (7.34 (7.26/7.38)). In the intraoperative period, no significant endotoxaemia was observed either in portal or systemic blood. The maximum reduction in pHi was related neither to the duration of VVB and OLT nor to the number of red cell units transfused. pHi after reperfusion did not correlate with graft viability or dysfunction of the lung or kidney. We conclude that pHi indicates mucosal ischaemia during OLT which is not necessarily associated with endotoxaemia, and intraoperative pHi monitoring does not appear to be a valuable predictor of postoperative graft failure and organ dysfunction.      

Laser Doppler flowmetry in evaluation of colonic blood flow during aortic reconstruction

Intraoperative laser Doppler flowmetry (LDF) was used to measure blood perfusion in terminal ileum and sigmoid colon in eight patients operated on for aorto-iliac occlusive disease (AIO) and eight patients for abdominal aortic aneurysm (AAA). The aim of the study was to evaluate the influence of clamping the inferior mesenteric artery (IMA) on intestinal perfusion. LDF-measured sigmoid colon flow was also compared with the postoperative clinical course, to define a limit below which risk of ischaemic colitis is high and revascularisation should be considered. Neither clamping of the IMA nor aortic reconstruction affected perfusion in the terminal ileum in any group. Sigmoid colon perfusion in the AAA-group showed a slight, not significant reduction after reconstruction (P = 0.09). AIO patients showed significant flow reduction in the sigmoid colon when the IMA was clamped (P less than 0.05), returning to the initial value after aortic reconstruction with end-to-side proximal anastomosis and preservation of IMA. AAA patients, operated with end-to-end proximal anastomosis and ligation of IMA, had significantly lower sigmoid colon perfusion after aortic reconstruction than AIO patients (P less than 0.05). Thirteen patients had sigmoid colon flux values greater than 5 RFU (Relative Flux Units) after reconstruction, and had no complications. Three aneurysm patients had flux values less than 3.3 RFU, and developed symptoms of ischaemic colitis. We conclude that LDF can be easily applied to the evaluation of colonic blood flow during aortic surgery. Flux values less than 4 RFU may indicate a risk of ischaemic colitis, and justify revascularisation of the colon.     

Continuous fiberoptic PCO2 monitoring indicates poorer gastric perfusion during supraceliac aortic clamping than conventional gastric tonometry in humans: A pilot study

Objective: To compare two monitors of gastric perfusion intraoperatively—continuous fiberoptic carbon dioxide partial pressure (PCO₂) sensor and conventional gastric tonometer. Design: Prospective, unblinded study. Setting: University teaching hospital. Participants: Adult patients undergoing major abdominal surgery. Interventions: A fiberoptic probe (Biomedical Sensors, Pfizer, High Wycombe, England) capable of continuous PCO₂ measurement and adapted to fit into the saline-filled balloon of a tonometric orogastric tube (Tonometrics, Instrumentarium Corp, Helsinki, Finland) was placed in the patients. The fiberoptic probe was attached to a Paratrend 7 machine (Biomedical Sensors, Pfizer) providing continuous intragastric PCO₂ data. A second tonometric orogastric tube was passed and used according to the manufacturer's instructions, yielding intermittent PCO₂ values. Measurements and Main Results: Twelve patients provided 79 data pairs: 33 without aortic clamp, 23 infraceliac aortic clamp, and 23 supraceliac aortic clamp. Data are presented as mean ± SD, and analysis of variance was used for comparison (p < 0.01); bias and precision were also calculated. Intramusosal PCO₂ and PCO₂ gradient were significantly higher, and intramucosal pH was significantly lower from continuous fiberoptic measurement in the supraceliac clamp group. In the no-clamp and infraceliac clamp groups, the differences between the 2 methods of measurement were not significant. Conclusion: Conventional gastric tonometry overestimated perfusion during conditions of compromised gastric blood flow (supraceliac aortic clamp).     

Continuous fiberoptic PCO2 monitoring indicates poorer gastric perfusion during supraceliac aortic clamping than conventional gastric tonometry in humans: a pilot study

OBJECTIVE: To compare two monitors of gastric perfusion intraoperatively--continuous fiberoptic carbon dioxide partial pressure (PCO2) sensor and conventional gastric tonometer. DESIGN: Prospective, unblinded study. SETTING: University teaching hospital. PARTICIPANTS: Adult patients undergoing major abdominal surgery. INTERVENTIONS: A fiberoptic probe (Biomedical Sensors, Pfizer, High Wycombe, England) capable of continuous PCO2 measurement and adapted to fit into the saline-filled balloon of a tonometric orogastric tube (Tonometrics, Instrumentarium Corp, Helsinki, Finland) was placed in the patients. The fiberoptic probe was attached to a Paratrend 7 machine (Biomedical Sensors, Pfizer) providing continuous intragastric PCO2 data. A second tonometric orogastric tube was passed and used according to the manufacturer's instructions, yielding intermittent PCO2 values. MEASUREMENTS AND MAIN RESULTS: Twelve patients provided 79 data pairs: 33 without aortic clamp, 23 infraceliac aortic clamp, and 23 supraceliac aortic clamp. Data are presented as mean +/- SD, and analysis of variance was used for comparison (p < 0.01); bias and precision were also calculated. Intramusosal PCO2 and PCO2 gradient were significantly higher, and intramucosal pH was significantly lower from continuous fiberoptic measurement in the supraceliac clamp group. In the no-clamp and infraceliac clamp groups, the differences between the 2 methods of measurement were not significant. CONCLUSION: Conventional gastric tonometry overestimated perfusion during conditions of compromised gastric blood flow (supraceliac aortic clamp).     

Intra-mucosal acidosis as a predictor of cardiac outcome following abdominal aortic aneurysm surgery.

OBJECTIVE: To assess if sigmoid ischaemia is a prognostic indicator of early and late post-operative cardiac morbidity and mortality. MATERIALS AND METHODS: Patients undergoing elective abdominal aortic aneurysm repair (AAAR) were included in the study. Demographic details and risk factors for heart disease were recorded. Sigmoid pHi was measured at the time of surgery using a silicone tonometer and perioperative morbidity and mortality were recorded in all patients. Seven years following surgery the patients and their general practitioners were contacted to determine the patient's health. RESULTS: Thirty-eight patients were included in the study. Within the follow-up period, 22 (58%) had died. Eight patients died of cardiac failure or myocardial infarction. The pHi in patients with cardiac related deaths [6.99 (6.84-7.10)] was significantly lower than those with non-cardiac related deaths [7.11 (7.04-7.21), p<0.05]. Similarly, patients who suffered acute cardiac events (within 30 days following AAA repair) had lower pHi [7.01 (6.88-7.12)] compared to those who did not [7.09 (6.90-7.19), p<0.05]. CONCLUSION: The results show that sigmoid ischaemia is more frequent amongst patients that develop cardiac events after AAAR and is associated with a worse long term outcome. This suggests that global hypoperfusion as a result of an under performing heart may be partly responsible for the sigmoid ischaemia in patients following AAAR. Therefore, low sigmoid pHi may predict an increased risk of cardiac complications in these patients.     

Noninvasive assessment of left ventricular pressure–area relationship using transesophageal echocardiography and tonometry during cardiac and abdominal aortic surgery

Purpose The purpose of this study was to noninvasively evaluate intraoperative left ventricular (LV) performance by an online pressure–area relationship using transesophageal echocardiography (TEE) and tonometry.Methods In study 1, LV pressure with a micromanometer catheter, LV cross-sectional area with TEE, direct radial pressure, and tonometric arterial pressure were simultaneously recorded in 5 patients (10 measurements) undergoing cardiac surgery. End-systolic elastance (Ees) was determined from pressure–area loops during inferior vena caval (IVC) occlusion. In study 2, in 16 patients undergoing repair of abdominal aortic aneurysm, LV performance (Ees; effective arterial load, Ea, and LV end-diastolic area, LV-EDA) was examined by noninvasive assessment of pressure–area loops using TEE and tonometry at aortic cross-clamping and unclamping.Results Ees by tonometric arterial pressure closely correlated with Ees by LV pressure (r = 0.92) in study 1. Ees at aortic clamping were not significantly different from those at unclamping. The clamping increased LV-EDA and Ea by approximately 13% and 44%, and the unclamping significantly decreased by 9% and 22%, respectively.Conclusion Our results demonstrated that online tonometric arterial pressure and LV area measured by automated border detection (ABD) of TEE might be used to calculate Ees to estimate LV contractility and allow the estimation of LV performance during aortic clamping and unclamping.     

Inferior Mesenteric Artery Stump Pressure: A Reliable Index for Safe IMA Ligation During Abdominal Aortic Aneurysmectomy

Fifty-two patients undergoing nonemergent abdominal aortic aneurysmectomy were prospectively studied to determine when the inferior mesenteric artery (IMA) could be ligated without subsequent development of ischemic colitis. Cannulation of the severed distal IMA for blood pressure measurement (IMA stump pressure) before and after aortic reconstruction was attempted in all and possible in 39 individuals. In 13 the IMA was thrombosed precluding pressure measurement. Prereconstruction and postreconstruction mean IMA stump and systemic arterial blood pressure measurements were computed and mean IMA/systemic pressure ratios were calculated. All patients underwent postoperative colonoscopy. One patient developed postoperative ischemic colitis. Her postreconstruction ratio was 0.37 and her postreconstruction mean IMA blood pressure was 33 mmHg, the only individual with a ratio and pressure less than 0.40 and 40 mmHg, respectively. Internal iliac arterial pulsations could not be restored in two patients. Although postresection indices were less than preresection indices in both, postresection indices were greater than 0.40 and 40 mmHg. In this study, if the IMA was thrombosed or if postresection pressures and ratios measured greater than 40 mmHg and 0.40 respectively, ischemic colitis did not develop following abdominal aortic aneurysmectomy. This simple test may prove useful in identifying patients at risk for developing postoperative ischemic colitis or if IMA revascularization is required.     

Can gastric intramucosal pH (pHi) predict outcome of paediatric cardiac surgery?

In forty-two children undergoing cardiac surgery using hypothermic cardiopulmonary bypass (CPB), a gastric tonometer was used intraoperatively to estimate pHi, reflection of splanchnic perfusion. PHi monitoring was used to predict early postoperative complications. Intramucosal acidosis appeared after removal of the aortic clamp and remained after weaning of CPB. Fifteen children (group C) developed early postoperative life-threatening complications. Twenty-seven children (group NC) had no major complications. Retrospective data analysis showed a decrease of pHi during hypothermic CPB in the two groups but at completion of surgery, pHi was significantly lower in the group C (7.13 +/- 0.04 vs 7.31 +/- 0.001, P < 0.001). Bypass and aortic clamp times were also longer in group C and intraoperative core temperature lower. Continuous automated tonometer gas analysis appeared more accurate for the monitoring of acute haemodynamic and respiratory changes and should probably improve the predictive value of tonometry in the future. Tonometry is highly sensitive and represents an interesting and minimally invasive monitoring for critically ill children.     

Ischaemic skeletal muscle increases serum ischaemia modified albumin.

OBJECTIVES: Ischaemia modified albumin (IMA) has been used as a marker of myocardial ischaemia but little is known about its production during ischaemia of other tissues. The clinical models of patients with intermittent claudication and major arterial surgery were used to investigate IMA production from ischaemic skeletal muscle. DESIGN: Prospective clinical study. MATERIALS AND METHODS: IMA was measured pre-operatively, at end ischaemia, and 5 min, 4, 24, 48, 72 and 144 h post-surgery in patients undergoing (a) revascularisation for intermittent claudication (IC, n=15), (b) abdominal aortic aneurysm repair (AAA, n=12) and controls (n=16). RESULTS: The median pre-operative IMA concentration in IC patients was significantly higher than the AAA group (88.3 versus 83.5 U/ml, p=0.036) and controls (88.3 versus 80.3 U/ml, p=0.031). IMA concentrations increased significantly during arterial clamping in both IC and AAA groups (88.3 versus 120.0 U/ml, p=0.001; 83.5 versus 118.8 U/ml, p=0.002, respectively) consistent with increased skeletal muscle ischaemia. In contrast, there was only a mild perioperative increase in the controls (80.3 versus 91.6 U/ml, p=0.012). CONCLUSIONS: Patients with intermittent claudication have significantly elevated IMA and skeletal muscle ischaemia during arterial surgery results in significantly increased circulating IMA. When IMA is used to detect myocardial ischaemia, ischaemic skeletal muscle must be excluded.     

Critical Analysis of Outcome Determinants Affecting Repair of Intact Aneurysms Involving the Visceral Aorta

Visceral (mesenteric and/or renal) ischemia/reperfusion phenomena likely contribute to the greater operative risk associated with pararenal and lower thoracoabdominal aortic aneurysm (TAA) repair. To differentiate the relative adverse effects of aortic clamp level, visceral ischemic duration, and various pre- and perioperative factors shared with infrarenal aneurysm patients, a comparative analysis of early and late outcomes after open repair of intact infrarenal and visceral aortic aneurysms was undertaken. A retrospective review of our university experience from 1993-1999/2002 revealed 549 patients (mean age 70 ± 8 years, 11% female) undergoing open repair of intact, degenerative aneurysms of the infrarenal (n = 391, 71%), juxtarenal (n = 78, 14%), suprarenal (n = 35, 7%), and type IV (n = 40, 7%) and type III (n = 5, 1%) TAA segments. All pararenal aneurysms required suprarenal (SR) or supravisceral (SV, above celiac or superior mesenteric artery) clamp placement. Concomitant renal reconstruction was done in 30% of visceral aortic and 3% of open infrarenal aneurysm repairs. Thirty-day adverse outcomes [death, renal failure (creatinine 2 × baseline or new dialysis), visceral (bowel, hepatic, renal, spinal cord, multiple organ dysfunction), and nonvisceral (cardiac, pulmonary, procedural) complications] were analyzed relative to patient and operative factors using univariate comparisons and multivariate stepwise logistic regression. Perioperative mortality rates varied significantly between aneurysm locations (infrarenal 2.1%, juxtarenal 2.6%, suprarenal 11.4%, TAA 13.3%; p < 0.01) and for clamp locations (infrarenal 2.1%, SR 3.0%, SV 10.8 %; p < 0.01) but were not different between juxtarenal (1.8% vs. 4.4 %) and SR (9.1% vs. 12.5%) aneurysms requiring SR or SV clamping, respectively. Visceral ischemic time (VIT) during SR or SV clamping, and not clamp location, was the only independent predictor of operative mortality [odds ratio (OR) = 10.8, 95% confidence interval (CI) 4-29]. Sensitivity analyses revealed VIT > 32 min to be the strongest predictor of early death. Visceral complication or renal failure affected 34% and 23% of visceral aortic (5% dialysis) and 7% and 5% (1% dialysis) of infrarenal repairs, respectively. VIT > 32 min, SV clamp placement, diabetes, and inflammatory aneurysm repair were each predictive of visceral complications and/or renal failure. Five-year survival rate was similar after visceral aortic (70%) and infrarenal (75%) repairs but negatively impacted only in patients with prior infrarenal abdominal aortic aneurysm repair and recurrent aneurysms (OR = 2.8, 95% CI 1.2-6.9). The high incidence of early adverse outcomes following repair of pararenal and lower thoracoabdominal aneurysms is primarily associated with excessive periods of renal and/or gut ischemia during visceral aortic clamp placement. However, nearly equivalent early and late survival was seen for visceral aortic and infrarenal repairs when VIT < 32 min was achieved.Presented at the Twenty-eighth Annual Meeting of the Southern Association for Vascular Surgery, Rio Grande, Puerto Rico, January 14-17, 2004.     

Sigmoid intramural pH for prediction of ischemic colitis during aortic surgery. A comparison with risk factors and inferior mesenteric artery stump pressures

We compared intramural pH (pHI) measured through a silicone balloon placed in the lumen of the sigmoid colon with risk factor analysis and inferior mesenteric artery (IMA) stump pressures as predictors of ischemic colitis in 34 patients undergoing elective or emergency operations on the abdominal aorta. All patients had preoperative and postoperative flexible sigmoidoscopy, IMA stump pressure measurements, and serial measurements of pHI. Logistic regression analysis showed that aortic aneurysm, age, and stenosis of the superior mesenteric artery were the only risk factors that bore a statistical relationship to ischemic colitis. Ligation of a patent IMA did not increase the likelihood of ischemic colitis. The IMA stump pressure criteria for predicting ischemic colitis were absent in nine of the ten patients in whom ischemic colitis developed and were present in five of the 24 in whom it did not develop. Intraoperative pHI dropped below 6.86 in all three patients in whom severe ischemic colitis developed. Mild colitis developed in seven patients whose minimum pH was 6.99 +/- 0.12 (mean +/- SD). No colitis developed in the remaining 24, whose minimum pH was 7.21 +/- 0.13. Thus, stump pressure is not a reliable means of predicting ischemic colitis. Aortic aneurysm, age, and superior mesenteric artery stenosis were significant risk factors. The average minimum intraoperative pHI and its duration were the best predictors for the development of ischemic colitis.     

Utility of sigmoid intramucosal pH in the early diagnosis of ischemic colitis after aorta surgery

A 62-year-old man with grade III ischemia of the legs and occlusion of an aortofemoral shunt underwent axillofemoral bypass and bilateral profundoplasty. During surgery, an aneurysm in the aortic origin of the right common iliac artery ruptured, requiring ligation of the inferior vena cava, the iliac veins and the right common iliac artery. Upon transfer of the patient to the recovery unit, the sigmoid intramucosal pH (pHi) was 6.83 (arterial pH 7.35), the regional CO2 pressure (PrCO2) was 100 mmHg (arterial PCO2 35.2 mmHg), and the lactic acid concentration was 3.6 mmol/L. Ischemic colitis was suspected and colonoscopy confirmed the presence of severe rectal and moderate sigmoid inflammation. An extended sigmoidectomy was performed with colostomy. The patient died from multiorgan failure 48 hours after surgery. Ischemic colitis is a severe complication of aortic surgery. Sigmoid pHi monitoring is non-invasive and highly useful for the early diagnosis of ischemic colitis.     

A comparison among portal lactate, intramucosal sigmoid Ph, and deltaCO2 (PaCO2 - regional Pco2) as indices of complications in patients undergoing abdominal aortic aneurysm surgery

Our aim in this observational, prospective, noncontrolled study was to detect, in 29 patients who underwent abdominal aortic aneurysm (AAA) surgery, correlations between the incidence of postoperative organ failure and intraoperative changes in arterial and portal blood lactate; changes in intramucosal sigmoid pH (pHi); differences between sigmoid Pco(2) and arterial Pco(2) (DeltaCO(2)); and hemoglobin (Hb). Hb, arterial blood lactate concentrations, pHi, and DeltaCO(2) (air tonometry) were recorded at the start of anesthesia (T0), before aorta clamping (T1), 30 minutes after clamping (T2), and at the end of surgery (T3). Portal venous lactate concentrations were recorded at T1 and T2. Patients were stratified into two groups: group A patients had no postoperative organ failure, and group B patients had one or more organ failures. As compared with group A (n = 16), group B patients (n = 13) had a lower pHi value at T2 and T3 and a higher DeltaCO(2) at T3. A pHi value of <7.15 was a predictor of organ failure, with a sensitivity of 92.3%, a specificity of 68.8%, and positive and negative predictive values of 70.6% and 91.7%, respectively, whereas a DeltaCO(2) value of >28 mm Hg predicted later organ failure with a sensitivity of 92.3%, a specificity of 62.5%, and positive and negative predictive values of 66.6% and 90.9%, respectively. Portal venous lactate concentrations were larger in group B at T2 (P < 0.001), and an increase >or=5 g/dL predicted later postoperative organ failure with a sensitivity of 92.3%, a specificity of 100%, and positive and negative predictive values of 100% and 94.1%, respectively. The comparison of the receiving operator characteristic curves to test the discrimination of each variable and the logistic regression analysis revealed that the increase in portal lactate was the best predictor for the development of postoperative organ failure. Hb concentration was significantly smaller in group B at T0 (13.8 +/- 1.0 g/dL versus 12.2 +/- 2.2 g/dL) and T2 (10.9 +/- 1.2 g/dL versus 9.1 +/- 1.9 g/dL). In conclusion, both pHi and DeltaCO(2) are reasonably sensitive prognostic indices of organ failures after AAA surgery, but they are less specific and accurate than portal venous lactate.     

Relationship between preoperative patency of the inferior mesenteric artery and subsequent occurrence of type II endoleak in patients undergoing endovascular repair of abdominal aortic aneurysms

OBJECTIVES: The purpose of this study was (1) to find out whether preoperative inferior mesenteric artery (IMA) patency (on radiographic imaging) predicts IMA-related endoleaks after endovascular repair of infrarenal abdominal aortic aneurysms, (2) to determine feasibility of measuring aneurysm sac pressures in patients with endoleaks, and (3) to report early evidence of effective endovascular obliteration of IMA endoleaks. METHODS: We studied 76 consecutive cases of infrarenal aortic aneurysms that were repaired with an endovascular approach (March 1998-April 1999). RESULTS: There were 13 (17%) endoleaks persistent 30 days after the procedure. Eleven (85%) of these 13 were IMA-related endoleaks, which were documented with selective superior mesenteric artery angiography. The preoperative finding (on computed tomographic scan) of a patent IMA does not always predict an IMA-related endoleak, but results in a statistically and clinically significant higher ratio of patients with IMA-related endoleaks in the immediate postoperative period (24% versus 3%, P <.035). In eight of the 11 patients with persistent IMA-related endoleaks, measurement of intra-aneurysm sac pressures was possible, and six of these patients had systemic pressures within the excluded aneurysm sac. Nine (82%) of 11 IMA-related endoleaks were successfully obliterated by means of selective IMA embolization. CONCLUSIONS: Many endoleaks are caused by a patent IMA, and this can result in persistence of systemic pressure within the aneurysm sac. The preoperative finding (on computed tomographic scan) of a patent IMA is a predictor of increased rates of IMA endoleaks, and IMA endoleaks can be successfully obliterated through endovascular procedures, after endovascular abdominal aortic aneurysm repair.     

Aortic stump closure with a titanium permanent clamp: A useful emergency method

Successful aortic stump closure in a patient with Behçet's disease was accomplished with a permanent titanium clamp. In May 1990, a saccular infrarenal abdominal aortic aneurysm was detected in this patient, and prosthetic graft replacement was carried out. One year later, this graft was removed because of perigraft fluid collection; the aortic stump was sutured closed, and a right axillobifemoral bypass was done. In November 1994, the patient was admitted to the hospital because of an aortoenteric fistula. An emergency operation was performed, and the aortic stump was managed successfully with a permanent clamp. In patients with Behçet's disease, use of a permanent clamp may offer an alternative to traditional methods for closing blown-out aortic stumps. (J Vasc Surg 1998;27:772-5.)     

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.     

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.     

Laparoscopic end-to-end aortobifemoral bypass with reimplantation of the inferior mesenteric artery

Background: Colic ischemia is a serious complication that can occur after abdominal aortic surgery. It has been described in two patients after laparoscopic aortic surgery. The goal of the current experiment was to determine the feasibility of inferior mesenteric artery (IMA) reimplantation during laparoscopic aortobifemoral bypass (LAFB). Methods: Six piglets were submitted to the laparoscopic approach according to the ``apron' technique previously described. The infrarenal aorta was clamped and an LAFB was performed using a dacron graft. The IMA was reimplanted in the body of the graft with a running 5-0 polypropylene suture. Results: Mean operation and dissection times were 282.5 min (range, 270–310 min) and 123 min (range, 110–140 min), respectively, with a mean blood loss of 108 ml (range, 80–150 ml). Aortic clamping and anastomotic times were 123 min (range, 110–135 min) and 33 min (range, 24–45 min), respectively. The IMA reimplantation took 55 min (range, 45–70 min). At autopsy, all anastomoses were patent with no stenosis nor leak. Conclusion: Laparoscopic IMA reimplantation during laparoscopic aortobifemoral bypass is feasible. Received: 10 July 1998/Accepted: 15 November 1998