Effects of enoxaparin and unfractionated heparin on platelet activity and reactivity during carotid endarterectomy.

The aim of this study was to determine platelet activity and reactivity and the effects of unfractionated heparin (UFH) and enoxaparin on platelet function during carotid eversion endarterectomy under local anesthesia. Twenty symptomatic patients undergoing carotid endarterectomy were randomly assigned to either 5,000 units of UFH or body weight-adjusted enoxaparin (0.5 mg/kg body weight) as an intraoperative intravenous bolus. The activity of platelets was assessed by measuring the expression of CD62p and CD41 with flow cytometry. Additionally, platelet-leukocyte aggregates (PLAs) were enumerated. The reactivity of platelets was evaluated by measuring the expression of the same antigens after stimulation. In addition, platelet reactivity was also analyzed using a PFA-100 analyzer. A significant increase in platelet activity was observed during surgery for CD41 and CD62p (p = .002 and < .001, respectively). The number of PLAs showed no significant changes during surgery. Yet there was a significant difference between patients treated with UFH and patients treated with enoxaparin. No difference for platelet activity or reactivity for patients receiving either UFH or enoxaparin prior to cross-clamping of the carotid arteries was seen. The formation of PLAs after endarterectomy was significantly higher in the UFH group; thus, PLAs are probably a useful surrogate parameter for measuring platelet activity.

Safety and efficacy of intravenous enoxaparin for carotid endarterectomy: a prospective randomized pilot trial.

OBJECTIVE: This prospective, randomized, single-center, open-label pilot study evaluated the safety and efficacy in carotid surgery of a single intraoperative bolus of body weight-adjusted enoxaparin compared with unfractionated heparin. METHODS: Symptomatic and asymptomatic patients with high-grade internal carotid artery stenosis were included. The primary objective was to evaluate perioperative efficacy (incidence of thromboembolic ischemic stroke). The secondary objective was to evaluate safety, including avoidance of hematoma at the site of surgery, gastrointestinal bleeding, rate of blood transfusions, and occurrence of heparin-induced thrombocytopenia. RESULTS: From July 2005 to June 2006, 338 consecutive patients undergoing carotid endarterectomy were enrolled; of these, 115 patients did not fulfill inclusion criteria, and 63 patients refused to participate. The remaining 160 patients were assigned in a 3:1 randomization to receive enoxaparin (0.5 mg/kg) or unfractionated heparin (5000 IU) intraoperatively as an intravenous bolus (120 and 40 patients, respectively). The mean patient age was 70.3 years (range, 43.3-94.7 years), and 54 were women. Internal carotid artery stenosis was asymptomatic in 55% and symptomatic in 45%. The difference in baseline characteristics between these groups was not significant. The rate of cerebral embolic events was 0.8% in the enoxaparin group (n = 1) and 2.5% in the unfractionated heparin group (n = 1). The rate of severe bleeding complications was 1.7% in the enoxaparin group (n = 2) and 5% in the unfractionated heparin group (n = 2; P > .05). No case of heparin-induced thrombocytopenia was observed. CONCLUSION: This pilot study found no difference between enoxaparin and unfractionated heparin during carotid endarterectomy in perioperative bleeding or embolic events. A large multicenter trial seems to be warranted.

Diagnostic accuracy of sigmoidoscopy compared with histology for ischemic colitis after aortic aneurysm repair.

Clinically relevant rates of ischemic colitis (IC) causing diarrhea, systemic involvement, colon necrosis, and, ultimately, death by multiple organ failure affect only a small proportion of patients after aortic reconstructions, with reported incidences of 2.7 to 3.3%. The key to treating and saving patients with this complication remains early detection and consequent treatment. The aim of this retrospective analysis of prospectively collected data was to compare the diagnostic accuracy of colonoscopy for detecting postoperative IC compared with histology and to evaluate the interobserver difference of two experienced surgeons. One hundred patients with infrarenal aortic aneurysms, operated on electively from March 2001 to December 2003, who had on postoperative days 3 to 6 a sigmoidoscopy by two independent surgeons and a histologic sample of the sigmoid mucosa, were included in the study. Patients with previous colon resection or inflammatory bowel disease were excluded from the study. All patients gave written informed consent. The study was approved by the Institutional Review Board. Histologic examination of the sigmoid mucosa revealed IC in 13 patients. The combined sensitivity of both investigators for detecting IC by sigmoidoscopy compared with histology was 84%, the specificity was 92.0%, the positive predictive value was 61.1%, the negative predictive value was 97.6%, and the diagnostic accuracy was 91.0%. There was no statistically significant difference between investigator 1 and investigator 2 (p=1.0) and between both investigators and histology (p=.380). Histology remains the gold standard for detecting IC after aortic surgery. Sigmoidoscopy, however, is a valid diagnostic tool allowing immediate clinical decision making with a negative predictive value of more than 94% and a diagnostic accuracy of 92%.

Aspirin resistance among long-term aspirin users after carotid endarterectomy and controls: flow cytometric measurement of aspirin-induced platelet inhibition.

BACKGROUND: Numerous studies have indicated that some patient subpopulations do not respond to the antithrombotic effects of aspirin. The objective of this study was to evaluate aspirin-induced inhibition of platelet cyclooxygenase (COX) using a flow cytometric technique in long-term aspirin users after carotid endarterectomy (CEA) and controls with newly diagnosed carotid stenosis not taking aspirin and to compare these results with platelet function analyzer measurements. METHODS: The study included 86 patients with a history of CEA on long-term aspirin therapy (100 mg daily) and 29 age-matched patients with newly diagnosed carotid artery stenosis not taking aspirin. Platelet-rich plasma diluted with phosphate-buffered saline was incubated with arachidonic acid (ARA) at a final concentration of 80 micromol/L. After staining with phycoerythrin-labeled anti-P-selectin (CD62p) antibody, platelet CD62p-antigen expression was measured on a flow cytometer. RESULTS: Flow cytometric measurement of ARA-induced platelet activation showed an inhibition of ARA-induced platelet stimulation in all patients on aspirin therapy, whereas all but two controls (95%) showed expected platelet reactivity. In contrast, results of the platelet function analyzer measurements were normal in 16% of aspirin-treated patients. CONCLUSIONS: Flow cytometric measurement of CD62p expression on platelets after incubation with ARA proved to be a practicable tool to monitor aspirin-induced inhibition of platelet COX. Results in patients on long-term low-dose aspirin therapy show that the inability of aspirin to inhibit platelet COX for both symptomatic and asymptomatic patients with high-grade internal carotid artery stenosis is a very rare event. So-called aspirin resistance detected quite frequently by platelet function analyzer measurement is most likely from COX-independent mechanisms.

Prevalence of patients continuing to smoke after vascular interventions.

INTRODUCTION: Smoking is one of the most important risk factors for the development and progression of atherosclerosis. Smoking cessation is an obligatory element in the management of vascular problems and in patients scheduled for vascular interventions. The aim of this study was to assess the prevalence of patients smoking before and after vascular surgical procedures and to evaluate the requirements for inpatient programs for smoking cessation and nicotine replacement therapy. METHODS: 500 patients admitted for vascular interventions were included in this prospective study. Smoking status was evaluated both objectively and subjectively. All patients underwent measurements of exhaled breath carbon monoxide to quantify nicotine dependency and all answered a standardized Fagerström questionnaire both on admission and after surgery to identify current smokers. RESULTS: Of 500 vascular patients included in the study, only 70 (14 %) never had smoked, 243 (49 %) had given up smoking before admission and 161 (32 %) were current smokers. Of the current smokers, 64 (40 %) did not smoke during hospitalization but 97 (60 %) continued to smoke in hospital. Of these 97 patients, 78 (80 %) were men and 19 women; their mean age was 61 +/- 4 years (range 40-84). Four patients had surgery for infrarenal aortic aneurysm, 40 underwent carotid endarterectomy and 53 had peripheral arterial occlusive disease (PAD). There was no difference between abstinent patients and continuing smokers in previous cigarette consumption or Fagerström score, a predictor for long-term smoking behavior. Patients with carotid artery stenosis were significantly more abstinent while hospitalized (P = 0.006); patients with PAD, however, were more likely to continue smoking as inpatients (P = 0.004). Sixty-five percent of continuing smokers stated that they would stop smoking in hospital if counseling and nicotine replacement therapy were provided. With regard to their predominant location of atherosclerosis, patients with PAD were less willing than those with carotid stenosis to abstain from smoking while hospitalized (53 % vs 88 %, respectively; P < 0.001). CONCLUSION: A substantial proportion of patients admitted for vascular surgery are smokers. More than half of these continue to smoke in the hospital, an environment where smoking is prohibited by law. Counseling, nicotine replacement therapy and smoking-cessation programs are urgently needed for vascular surgical inpatients.

Replanting the inferior mesentery artery during infrarenal aortic aneurysm repair: influence on postoperative colon ischemia.

BACKGROUND: Replanting the inferior mesentery artery (IMA) to prevent ischemic colitis (IC) has been discussed for many years; yet, to our knowledge, no prospective studies have been conducted to compare the incidence of histologically proven IC in patients with and without IMA revascularization. The aim of this prospective study, with histologic evaluation of the sigmoid colon mucosa, was to assess the influence of replanting the IMA on IC and mortality. METHODS: From January 1999 to December 2003, 160 consecutive patients who were operated on for a symptomatic (n = 21) or asymptomatic (n = 139) infrarenal aortic aneurysm were prospectively assessed and randomly assigned either to replanting or ligating the IMA. Sigmoidoscopy with biopsy was performed on day 4 or 5 after surgery; an autopsy was performed on patients not surviving to day 5 after surgery. All patients gave written informed consent. RESULTS: Of the 160 randomized patients, 128 had a confirmed patent IMA and formed the basis of this study. Their age was 70 +/- 8 years (men, 70 +/- 8 years; women, 73 +/- 7 years). The IMA was replanted in 67 patients (52%) and ligated in 61 (48%) intraoperatively. IC developed in six patients with a replanted IMA and in 10 with a ligated IMA (relative risk [RR], 0.55; 95% confidence interval [CI], 0.21 to 1.41; chi2 = 1.62; P = .203). Blood loss in the two cohorts did not differ significantly (P = .788); however, patients with IC had a significantly higher blood loss compared with the cohort without IC (P = .012) and were older (P = .017). Age, sex distribution, clamping time, the use of tube or bifurcated grafts, and intraoperative hypotension did not differ between patients with ligated or replanted IMA. CONCLUSION: Although replanting the IMA did not confer a statistically significant reduction of perioperative morbidity or mortality in this study, it appears that older patients and patients with increased intraoperative blood loss might benefit from IMA replantation, because this maneuver does not increase perioperative morbidity or substantially increase operation time.