Elective Abdominal Aortic Surgery Research Articles

Intraoperative Autotransfusion in Abdominal Aortic Aneurysm Surgery

To determine whether intraoperative autotransfusion reduces the percentage of patients undergoing allogeneic blood transfusion. Using a public domain database (MEDLINE) and a Web-based search engine (PubMed), all intraoperative autotransfusion vs control prospective randomized controlled trials that enrolled patients undergoing elective infrarenal abdominal aortic aneurysm surgery, published between January 1, 1966, and November 30, 2005, were searched. Relevant studies were identified through a manual search of secondary sources including references of initially identified articles. Data on detailed inclusion criteria, autotransfusion system type, and incidence of allogeneic blood transfusion were abstracted from each study. Sensitivity analyses were performed by excluding individual trials one at a time and recalculating the pooled risk ratio estimates for the remaining studies. Our search identified 4 randomized controlled trials including data for 292 patients. Pooled analysis demonstrated a statistically significant 37% reduction in risk of allogeneic blood transfusion with intraoperative autotransfusion compared with control (risk ratio, 0.63; 95% confidence interval, 0.41-0.95; P = .03) in a random-effects model. There was statistically significant trial heterogeneity of results (P = .02) but no evidence of statistically significant publication bias (P = .497). Two of 4 sensitivity analyses demonstrated statistically nonsignificant results favoring intraoperative autotransfusion. Based on a meta-analysis of available randomized controlled trials, intraoperative autotransfusion reduces risk of allogeneic blood transfusion in elective infrarenal abdominal aortic aneurysm surgery.

Temporary Worsening of Renal Function After Aortic Surgery Is Associated With Higher Long-Term Mortality

Little is known about acute changes in renal function in the postoperative period and the outcome of patients undergoing major vascular surgery. Specifically, data are scarce for patients in whom renal function temporarily decreases and returns to baseline at 3 days after surgery. Retrospective cohort study. 1,324 patients who underwent elective open abdominal aortic aneurysm surgery in a single center. Renal function (creatinine clearance was measured preoperatively and on days 1, 2, and 3 after surgery. Patients were divided into 3 groups: group 1, improved or unchanged (change in creatinine clearance, +/-10% of function compared with baseline); group 2, temporary worsening (worsening > 10% at day 1 or 2, then complete recovery within 10% of baseline at day 3); and group 3, persistent worsening (>10% decrease compared with baseline). All-cause mortality. 30-day mortality rates were 1.3%, 5.0%, and 12.6% in groups 1 to 3, respectively. Adjusted for baseline characteristics and postoperative complications, 30-day mortality was the greatest in patients with persistent worsening of renal function (hazard ratio [HR], 7.3; 95% confidence interval [CI], 2.7 to 19.8), followed by those with temporary worsening (HR, 3.7; 95% CI, 1.4 to 9.9). During 6.0 +/- 3.4 years of follow-up, 348 patients (36.5%) died. Risk of late mortality was 1.7 (95% CI, 1.3 to 2.3) in the persistent-worsening group followed by those with temporary worsening (HR, 1.5; 95% CI, 1.2 to 1.4). No steady state was achieved to assess renal function. Although renal function may recover completely after aortic surgery, temporary worsening of renal function was associated with greater long-term mortality.

Estimation of physiologic ability and surgical stress (E-PASS) as a predictor of immediate outcome after elective abdominal aortic aneurysm surgery

Background The Estimation of Physiologic Ability and Surgical Stress (E-PASS) score was designed on the premise that the balance between the patient’s physiologic reserve capacity and the surgical stress inflicted at operation was important in the occurrence of postoperative complications. The aim of this study was to assess its value in predicting mortality and morbidity after open elective abdominal aortic aneurysm (AAA) repair. Methods E-PASS data items were collected prospectively in a group of 204 patients undergoing elective open AAA repair over a 6-year period. The operative morbidity and mortality rates were compared with the preoperative risk score (PRS), surgical stress score (SSS) and comprehensive risk score (CRS) of E-PASS. The group comprised 180 (88%) males and the median age was 73 (range 44 to 86) years. Results There were 13 (6%) deaths and 121 (59%) experienced a postoperative complication. As the PRS, SSS and CRS increased, the incidence of postoperative morbidity and mortality significantly increased ( P < .0001). Overall mean CRS was .52 (±.27). Mean CRS in the groups of patients who survived and died were .49 (±.24) and .98 (±26), respectively. PRS, SSS, and CRS all had extremely good predictive power for both mortality and morbidity as demonstrated by high areas under the receiver operator curve (range .799 to .953). CRS also showed a strong statistically significant association with the severity of postoperative complication ( P < .0001) and length of hospital stay ( P < .0001). Conclusions The E-PASS model appears to be a promising method of predicting death and the development of postoperative complications in patients undergoing elective open AAA surgery. It requires further validation in arterial surgery at different geographical locations.

Transfusion requirements and outcomes in patients undergoing abdominal aortic surgery using intra-operative cell salvage

Intraoperative cell salvage (ICS) is the recovery, anticoagulation, filtration and reinfusion of blood lost during surgery. The aim of this study is to determine the safety and efficacy of ICS in emergency and elective abdominal aortic surgery. This study reviews volumes of blood loss, blood salvaged with ICS, allogenic blood requirements, and clinical outcomes in patients undergoing abdominal aortic surgery using ICS. Seventy-nine patients undergoing abdominal aortic surgery are included. Supplemental allogenic blood was not required in 45/79 (57%) of all patients. Transfusion with allogenic blood was not necessary in 41/63 (66%) of elective abdominal aortic aneurysm repairs. ICS was associated with no major complications. ICS is a safe procedure and substantially reduces the need for blood transfusion in patients undergoing abdominal aortic surgery. It may substantially alleviate shortages of allogenic blood and should be part of the armamentarium of vascular units.

Acute Renal Injury and Dysfunction Following Elective Abdominal Aortic Surgery

To evaluate the incidence of kidney injury and acute renal dysfunction (ARD) and associated risk factors in open abdominal aortic surgery. 69 patients undergoing elective infrarenal aortic repair were included in a prospective study. Anaesthesia and haemodynamic management were standardised targeting a mean arterial pressure (MAP) of 70-90 mmHg, pulmonary artery occlusion pressure of 12-14 mmHg and cardiac index >or=2.4 l/min/m(2). Urinary albumin-creatinine and N-acetyl-B-D-glucosaminidase-creatinine ratios were measured as indicators of kidney injury. The definition of ARD was based on the RIFLE criteria. Kidney injury was found in most patients. ARD developed in 22% of the patients, and acute renal failure in 4%. The patients with ARD were older, and had lower plasma creatinine and estimated GFR before surgery. ARD was associated with intraoperative hypotension (MAP <60 mmHg >15 min), low cardiac index (<2.4 l/min/m(2)), rhabdomyolysis, and early reoperation. Intraoperative hypotension and postoperative low cardiac output were independent risk factors for ARD in multivariate analysis. Kidney injury occurs in most patients undergoing infrarenal aortic surgery, but only 22% develop acute renal dysfunction. Hypotension and low cardiac output are risk factors that could be avoided by optimizing perioperative management.

Early Postoperative Feeding after Elective Abdominal Aortic Aneurysm Surgery

Early Postoperative Feeding after Elective Abdominal Aortic Aneurysm Surgery

Epidural Pain Relief Versus Systemic Opioid-Based Pain Relief for Abdominal Aortic Surgery

BACKGROUND: Epidural analgesia offers greater pain relief when compared with systemic opioid-based medications, but its effect on morbidity and mortality is unclear. OBJECTIVES: To assess the benefits and harms of postoperative epidural analgesia in comparison with postoperative systemic opioid-based pain relief for adult patients who underwent elective abdominal aortic surgery. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via OVID (The Cochrane Library, Issue 3, 2004); OVID MEDLINE (1966 to July 2004); and EMBASE (1980 to June 2004). We assessed non-English language reports and contacted researchers in the field. We did not seek unpublished data. SELECTION CRITERIA: We included all randomized, controlled trials comparing postoperative epidural analgesia and postoperative systemic opioid-based analgesia for adult patients who underwent elective open abdominal aortic surgery. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial quality and extracted data. We contacted study authors for additional information and data. MAIN RESULTS: Thirteen studies involving 1224 patients met our inclusion criteria; 597 patients received epidural analgesia and 627 received systemic opioid analgesia. The epidural analgesia group showed significantly lower visual analog scale scores for pain on movement (up to postoperative day 3), regardless of the site of the epidural catheter and epidural formulation. Postoperative duration of tracheal intubation and mechanical ventilation were significantly shorter by about 20% in the epidural analgesia group. The overall incidence of cardiovascular complication; myocardial infarction; acute respiratory failure (defined as an extended need for mechanical ventilation); gastrointestinal complication; and renal insufficiency was significantly lower in the epidural analgesia group, especially in trials that used thoracic epidural analgesia. REVIEWERS’ CONCLUSIONS: Epidural analgesia provides better pain relief (especially during movement) for up to three postoperative days. It reduces the duration of postoperative tracheal intubation by approximately 20%. The occurrence of prolonged postoperative mechanical ventilation, overall cardiac complication, myocardial infarction, gastric complication, and renal complication was also reduced by epidural analgesia, especially thoracic. However, current evidence does not confirm the beneficial effect of epidural analgesia on postoperative mortality and other types of complications. CITATION: Nishimori M, Ballantyne JC, Low JHS. Epidural pain relief versus systemic opioid-based pain relief for abdominal aortic surgery (Cochrane Reviews). In: The Cochrane Library, Issue 3, 2006. Reproduced with permission.

Incidence, risk factors and prognosis of changes in serum creatinine early after aortic abdominal surgery

To determine the incidence, risk factors, and prognostic implications of serum creatinine changes following major vascular surgery. Observational study. University hospital. Cohort of 599 consecutive patients undergoing elective abdominal aortic surgery. Review of prospectively collected data from 1993 to 2004. The receiver-operator characteristic (ROC) curve analysis was used to detect the best threshold for postoperative elevation in serum creatinine (Delta Creat) in relation to major complications. A cut-off value of +0.5 mg/dl was selected to define renal dysfunction (RD(0.5) group, n=91; no RD(0.5), n=508) that was associated with higher mortality (7.7% in RD(0.5) group vs 1.4% in no RD(0.5) group, P<0.05), rate of admission to the ICU (34% vs 13%, P<0.05), and incidence of cardiovascular (9% vs 4%, P<0.05), respiratory (21% vs 7%, P<0.05), surgical (24% vs 10%, P<0.05), and septic complications (9% vs 3%, P<0.05). After multivariate analysis with logistic regression, renal dysfunction was independently related to low preoperative creatinine clearance [<40 ml/min; odds ratio (OR) 1.5, 95% confidence interval (CI) 1.1-3.9], prolonged renal ischemic time (>40 min; OR, 3.8, 95% CI, 1.9-7.2), blood transfusion (>5 units; OR, 1.9, 95% CI 1.2-6.1), and rhabdomyolysis (OR, 3.6, 95% CI 1.7-7.9). Postoperative RD(0.5) (Delta Creat >0.5 mg/dl) occurs in 15% of vascular patients and carries a bad prognosis. Preoperative renal insufficiency and factors related to the complexity of surgery are the main predictors of renal dysfunction.

Vascular viewpoint

Question: In patients with clinically stable coronary artery disease, who are scheduled for elective abdominal aortic or infrainguinal vascular surgery, does prophylactic coronary artery revascularization prior to vascular surgery reduce long-term mortality? Population: Patients met inclusion criteria if they were undergoing elective vascular surgery and a cardiologist considered them at increased risk for perioperative cardiac complications based on clinical risk factors or the presence of ischemia on nuclear stress imaging. After coronary angiography, patients were considered eligible for randomization if they had a &lt;70% stenosis in one or more major coronary artery that was suitable for revascularization. Patients with unstable angina, stenosis of the left main coronary artery of &gt;50%, left ventricular ejection fraction &lt;20%, or severe aortic stenosis were excluded from the trial. Design and methods: During 1997-2003 from 18 Veterans Administration centers in the USA, 5859 patients were screened, of which 80% were initially excluded because of insufficient cardiac risk or no evidence of ischemia on nuclear imaging ( n = 2280), urgent vascular surgery ( n = 1025), severe coexisting comorbidities ( n = 731), or refusal to participate or enrolment in other studies ( n = 633). Of the remaining 1190 patients who underwent coronary angiography, 680 (57%) were excluded for the following reasons: non-occlusive or non-operable coronary artery disease 363 (53%) and 215 (32%), respectively; and exclusions (e.g. left main coronary artery disease) 15%. A randomized design was used to assign 510 patients (98% men) to a strategy of preoperative coronary artery revascularization ( n = 258), or no revascularization ( n = 252), before vascular surgery. Of the participants, 74% had more than three of the Eagle clinical criteria, or more than two of the variables of the Revised Cardiac Risk Index, or a moderate to large reversible defect on imaging (71% of the 65% participants who received nuclear stress tests). Also, 33% of participants had three-vessel coronary artery disease. The choice of coronary revascularization, either percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG), was left to the discretion of the study centers. The primary outcome was long-term all-cause mortality. Secondary outcomes were perioperative mortality or myocardial infarction, stroke, limb loss, or dialysis. The analysis followed the intention-to-treat principle. Results: Median follow-up was 2.7 years and follow-up was 100% complete. Long-term all-cause mortality did not differ between the two groups: 67 (26%) patients in the non-revascularization group and 70 (27%) patients in the revascularization group died (RRR 4%; 95% CI - 32 to 30). There was also no difference in perioperative mortality ( p = 0.87), myocardial infarction ( p = 0.37), stroke ( p = 0.59), limb loss ( p = 0.11), and dialysis ( p = 0.97). Conclusions: In patients with clinically stable coronary artery disease, who are scheduled for elective abdominal aortic or infrainguinal vascular surgery, prophylactic coronary artery revascularization using PCI or CABG prior to surgery did not reduce long-term all-cause mortality.

Dynamic preoperative assessment of cardiac reserve in elective aortic surgery.

Myocardial infarction accounts for over 50 per cent of mortality following elective abdominal aortic surgery. Previous history of ischaemic heart disease and abnormal ECGs, common in vascular patients, are unreliable parameters for predicting myocardial response to stress. Exercise ECGs are often valueless, as claudication may mask myocardial insufficiency. Myocardial performance was studied preoperatively in 29 consecutive patients undergoing elective aortic bifurcation grafting, using a Swann-Ganz catheter to measure the rise in pulmonary artery wedge pressure (PAWP) produced by rapid intravenous infusion of plasma (200-400 ml). A Frank-Starling Curve was obtained by plotting LVSWI against PAWP. Two important values were obtained: (a) 'Upslope' or gradient of the ascending portion of the curve. Low values identify patients most at risk from cardiac complications. Six patients who suffered from postoperative cardiac complications had a mean 'upslope' value of 1.568 +/- 0.681 (1 s.e.m.), whereas the 23 who did not, had a mean value of 7.094 +/- 0.745 (1 s.e.m.), a significant difference (P less than 0.001); (b) 'PAWPmax', the ventricular filling pressure above which work output dropped. Infusion beyond this may precipitate pulmonary oedema. PAWP was observed at levels greater than PAWPmax in all 6 patients who developed either pulmonary oedema or myocardial infarction. The myocardial performance curve can reliably identify high risk patients and permit control of intravenous therapy within individual safety limits, thereby preventing pulmonary oedema.

Risk factors and prevalence of perioperative cognitive dysfunction in abdominal aneurysm patients

Perioperative delirium is common in high-risk surgery and is associated with age, education, preoperative cognitive functioning, pre-existing medical conditions, and postoperative complications. We investigated these factors as well as lifestyle and demographic variables by using cognitive measures that were more sensitive than those used in previous studies. Extensive medical and demographic data were collected on 102 patients between 41 and 88 years of age to identify comorbidities and lifestyle considerations preoperatively. Elective abdominal aortic aneurysm surgery was performed under combined general/epidural anesthesia with postoperative epidural analgesia. A battery of sensitive, cognitive measures was administered preoperatively, at the time of discharge from hospital, and 3 months postoperatively. Symptoms of delirium were assessed during the first 6 postoperative days using Diagnostic and Statistical Manual of Mental Disorders-4th Edition criteria. Intraoperative and postoperative data, including medications, vital signs, conduct of the surgery and anesthesia, complications, and details of pain control, were collected. Delirium occurred in 33% of the patients during the first 6 days after surgery. Longer duration of delirium was related to lower education, preoperative depression, and greater preoperative psychoactive medication use. Characteristics of the surgery and hospital stay were unrelated to the development of delirium. Patients who were diagnosed with delirium had lower cognitive scores during each of the three assessment periods, even when controlling for age and education. Logistic regression analysis indicated that the most powerful preoperative predictors of delirium were number of pack years smoked (P = .001), mental status scores (P = .003), and number of psychoactive medications (P = .005). A significant proportion of patients undergoing elective abdominal aortic aneurysm repair are susceptible to the development of delirium and are at risk for cognitive dysfunction after surgery. Our findings have implications for promoting long-term lifestyle changes, including smoking cessation and improved management of mental health as risk-reduction strategies.

Effect of Bicarbonated Ringer's Solution on the Acid-base Balance in Patients Undergoing Abdominal Aortic Aneurysm Repair

The present study was designed to assess whether prophylactic use of bicarbonated Ringer's solution ameliorates metabolic acidosis in patients undergoing aortic surgery. Twenty patients undergoing elective infrarenal aortic aneurysm repair were randomly assigned to receive either bicarbonated Ringer's solution or acetated Ringer's solution. The pH, PaCO(2), and base excess (BE) were measured before surgical incision (T0), 5 min before reperfusion (T1), 5 min after reperfusion (T2), and 30 min after reperfusion (T3). Data were compared between the two groups. Both pH and BE initially showed a slight decrease in both groups during clamping. After unclamping of the aorta, an additional decrease in pH was observed in both groups (T0 to T2, and T3). There were no significant differences in pH between the groups throughout the study period. Aortic cross-clamping leads to the development of metabolic acidosis, with a decrease in pH and BE. The effect of administration of bicarbonated infusion fluid during elective abdominal aortic surgery had not significant compared with that of acetated Ringer's solution with respect to acid-base homeostasis.

Blood loss and transfusion in elective abdominal aortic aneurysm surgery.

Intraoperative blood loss and transfusion are known determinants of mortality and morbidity of elective abdominal aortic aneurysm (AAA) repair. The present study analysed the pattern of blood loss and transfusion and evaluated the risk factors of blood loss during open repair of infrarenal AAA. Blood loss, transfusion and fluid replacement during elective open repair operation for patients with infrarenal AAA were correlated to demographic data, operative findings and procedural information. A total of 129 patients with a mean age of 71 years was analysed. The mean blood loss was 1000 +/- 887 mL (200-6000 mL). Blood transfusion, with a mean transfusion volume of 400 +/- 591 mL (0-3000 mL), was required in 46% of patients. Univariate analysis showed that bodyweight, renal impairment, low haemoglobin and platelet counts, iliac artery involvement, large aneurysm, bifurcated graft, large graft diameter, prolonged aortic clamp time and long operation time were associated with a higher blood loss. A haemoglobin level of <10.5 g/dL (relative risk (RR): 4.6), platelet count <130 x 10(9)/L (RR: 3.9), aortic clamp time >50 min (RR: 15), total operation time >200 min (RR: 11) and type of graft (RR: 3.5) were identified as independent determinants of blood loss on multivariate analysis. Intraoperative blood loss in elective infrarenal aneurysm surgery is influenced by patients' haematological parameters, distal involvement of aneurysm and degree of difficulty of operation.

Randomized study comparing the effects of hydroxyethyl starch solution with Gelofusine on pulmonary function in patients undergoing abdominal aortic aneurysm surgery

Restoring blood flow to ischaemic tissue can cause lung damage with pulmonary oedema. Hydroxyethyl starch (HES) solution, when used for volume replacement, may modify and reduce the degree of ischaemia-reperfusion injury. We compared the effects of HES solution with those of Gelofusine solution on pulmonary function, microvascular permeability and neutrophil activation in patients undergoing elective infrarenal abdominal aortic aneurysm surgery. Forty patients were randomized into two groups. The anaesthetic technique was standardized. Lung function was assessed with the PO(2)/FI(O(2)) ratio, respiratory compliance, chest x-ray and a score for lung injury. Microvascular permeability was determined by measuring microalbuminuria. Neutrophil activation was determined by measurement of plasma elastase. Four hours after surgery, the median (quartile values) PO(2)/FI(O(2)) ratio was 40.3 (37.8, 53.1) kPa for the HES-treated patients compared with 33.9 (31.2, 40.9) kPa for the Gelofusine-treated patients (P<0.01, Mann-Whitney test). The respiratory compliance was 80 (73.5, 80) ml cm(-1) H(2)O in the HES-treated patients compared with 60.1 (50.8, 73.3) ml cm(-1) H(2)O in the Gelofusine-treated patients (P<0.01, Mann-Whitney test). The lung injury score 4 h after surgery was less for the patients treated with HES compared with the patients treated with Gelofusine (0.33 vs 0.71, P=0.01, Wilcoxon rank sum test). Mean (SD) plasma elastase was less in the HES-treated patients on the first postoperative day (1.96 (0.17) vs 2.08 (0.24), P<0.05). The log mean microalbuminuria was less in the HES-treated patients (0.41 vs 0.91 mg mmol(-1), P<0.05). This difference in microvascular permeability was associated with different volumes of colloid required to maintain stable cardiovascular measurements in the two groups of patients studied (3000 vs 3500 ml, P<0.01, Mann-Whitney test). Compared with Gelofusine, the perioperative pulmonary function of patients treated with HES after abdominal aortic aneurysm surgery was better.

The value of preoperative pharmacologic stress testing before vascular surgery using ACC/AHA guidelines: a prospective, randomized trial

Objective To evaluate the validity of preoperative cardiac stress testing using clinical predictors from the American College of Cardiology/American Heart Association Guidelines on Perioperative Evaluation before Noncardiac Surgery in patients undergoing vascular surgery. Design Prospective, randomized pilot study. Setting Academic medical center. Participants Patients undergoing elective abdominal aortic, infrainguinal, and carotid vascular surgery. Interventions After stratification by American College of Cardiology/American Heart Association (ACC/AHA) Guideline parameters, 99 patients were randomized to preoperative cardiac stress testing or to no stress testing and followed for up to 12 months postoperatively for adverse cardiac outcomes. Measurements and main results Before hospital discharge of 46 patients who underwent preoperative stress testing, 7 (15%) had inducible ischemia with no adverse postoperative cardiac outcomes, whereas only 1 (3%) of 39 patients (85%) with no ischemia had a nonfatal adverse cardiac outcome ( p = not significant). Of 53 patients without preoperative stress testing, only 2 (4%) had a nonfatal adverse postoperative cardiac outcome. There were no cardiac deaths. At 12-month follow-up in 79 (80%) patients, there was 1 nonfatal adverse cardiac outcome (no stress test) and 1 cardiac death (abnormal stress test), reflecting a 1% 12-month cardiac morbidity and mortality. Conclusion In this small prospective, randomized study evaluating the validity of preoperative cardiac stress testing using ACC/AHA Guidelines before major vascular surgery, preoperative cardiac stress testing offered no incremental value for determining postoperative adverse cardiac outcomes. Larger randomized clinical trials are needed to confirm these findings.

Incidence and circumstances of serum creatinine increase after abdominal aortic surgery.

To evaluate the incidence and the circumstances of a moderate increase in serum creatinine early after elective abdominal aortic surgery. Prospective clinical observational study. Surgical intensive care unit in a university hospital. Two hundred and fifteen consecutive adult patients operated on for infra-renal abdominal aortic surgery during 1 year. A moderate increase in plasma creatinine of 20% from preoperative value (renal dysfunction, RD) was systematically recorded during the first 3 days following surgery. Organ dysfunctions (cardiac, pulmonary, haematological, and neurological) were assessed. Forty-three patients (20%) experienced a postoperative RD; six of these required dialysis. RD was associated with other organ dysfunctions in 60.5% patients. Mortality rate was significantly higher for patients who had a RD, than patients without RD (9.3% vs 1.2%, P<0.02). Mean ICU stay of patients with RD was significantly longer (7.9+/-5.6 days vs 5.0+/-1.8 days, P<0.01). However, patients with RD but without other organ dysfunctions had a mortality rate of 0% and did not have a significantly longer stay in ICU than patients without any organ dysfunctions (5.2+/-2.1 days vs 4.6+/-1.2 days, P=0.09). Our results suggest that a postoperative 20%-increase in plasma creatinine after abdominal aortic surgery is not rare and occurs frequently with other organ dysfunction.

Prediction of cardiac risk prior to elective abdominal aortic surgery: role of multiple gated acquisition scan.

Debate continues regarding the value of cardiac testing before major vascular surgery. Studies looking at whether a low radioisotope left ventricular ejection fraction (LVEF) could reliably predict postoperative cardiac events have produced conflicting results. Technetium-99m multiple gated acquisition (MUGA) scanning was employed in 122 patients undergoing elective abdominal aortic aneurysm surgery to estimate the resting LVEF and to detect regional or global myocardial wall motion abnormalities (WMAs). Adverse cardiac outcomes were predicted using logistic regression analysis. Among this group of patients, 20 did not proceed to surgery for a variety of reasons, and 102 underwent surgical repair. More than half of the patients (55%) had a history of cardiac disease. The mean +/- SD LVEF was 55.5% +/- 11.1%. Altogether, 31 patients had WMAs, and 21 had both WMAs and an abnormal LVEF (< or = 50%). Altogether, 20 cardiac complications were encountered in 17 patients (17%). Logistic regression analysis identified four significant predictors of cardiac complications: history of cardiac disease [odds ratio (OR) 10.43; 95% confidence interval (CI) 1.3 and 80.5], the presence of WMAs (OR 10.1, CI 1.4 and 74.6), additional procedures (OR 12.1, CI 1.4 and 103.0), and reoperation during the postoperative period (OR 6.4, CI 1.4 and 30.4). This is the largest reported British series of cardiac testing using MUGA scans prior to abdominal aortic reconstruction. Only the presence of WMAs (not the resting LVEF) was useful for predicting postoperative cardiac events. A history of cardiac disease, additional procedures, and reoperation during the postoperative period also place a patient at high risk for cardiac complications. A normal LVEF is by no means reassuring that a patient is at low risk of suffering an adverse cardiac outcome.

Complete rectal obstruction due to ischaemia following elective abdominal aortic aneurysm surgery

Ischaemic rectal stricture formation is a rare but documented complication of aortic aneurysm surgery. We report the first case of acute large bowel obstruction secondary to this rare complication.

Validation of two risk models for perioperative mortality in patients undergoing elective abdominal aortic aneurysm surgery.

The authors validated 2 clinical risk models for perioperative mortality in patients scheduled for elective open abdominal aortic aneurysm surgery (AAA surgery). They studied 361 patients who underwent elective AAA surgery between 1991 and 1999 (validation population). Two clinical risk models were validated. The first was developed in 238 patients from Leiden University Hospital (Leiden risk model). The Leiden risk model was modified to provide predictions for the validation population based on 6 predictors including age, gender, a history of previous myocardial infarction, congestive heart failure, renal disease, and pulmonary disease. The second was a recently published simpler risk model developed in 820 patients in the UK Small Aneurysm Trial (UK risk model) and included 3 predictors (age and renal and pulmonary comorbidity). Logistic regression was used to quantify the relationship between predictors and outcome (mortality within 30 days of surgery). Validation further included the concordance statistic (c-statistic) for discriminative ability and the Hosmer-Lemeshow test for model reliability. The perioperative mortality in the validation population was 6.6% (24/361). Predictors had similar odds ratios, with particularly strong effects of congestive heart failure, pulmonary disease, and renal impairment. The Leiden risk model had reasonable good ability (c-statistic 0.72) and showed adequate calibration (chi(2)=3.3, p=0.97). It could particularly identify a low-risk group. The UK risk model did not perform well (c-statistic 0.60), showing statistically significant lack of fit (chi(2)=64.9, p<0.001). This study showed similar predictive ability of previously identified predictors for perioperative mortality. The Leiden risk model could identify a low-risk group, while the UK risk model showed a relatively poor performance. The current study supports the use of the Leiden model for preoperative risk assessment.

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.