Biological efficacy of low versus medium dose aspirin after coronary surgery: results from a randomized trial [NCT00262275].

BACKGROUND: The beneficial effect of aspirin after coronary surgery is established; however, a recent study reported the inability of low doses (100 mg) to inhibit postoperative platelet function. We conducted a double-blind randomised trial to establish the efficacy of low dose aspirin and to compare it against medium dose aspirin. METHODS: Patients undergoing coronary surgery were invited to participate and consenting patients were randomised to 100 mg or 325 mg of aspirin daily for 5 days. Our primary outcome was the difference in platelet aggregation (day 5 - baseline) using 1 microg/ml of collagen. Secondary outcomes were differences in EC50 of collagen, ADP and epinephrine (assessed using the technique of Born). RESULTS: From September 2002 to April 2004, 72 patients were randomised; 3 patients discontinued, leaving 35 and 34 in the low and medium dose aspirin arms respectively. The mean aggregation (using 1.1 microg/ml of collagen) was reduced in both the medium and low dose aspirin arms by 37% and 36% respectively. The baseline adjusted difference (low - medium) was 6% (95% CI -3 to 14; p = 0.19). The directions of the results for the differences in EC50 (low - medium) were consistent for collagen, ADP and epinephrine at -0.07 (-0.53 to 0.40), -0.08 (-0.28 to 0.11) and -4.41 (-10.56 to 1.72) respectively, but none were statistically significant. CONCLUSION: Contrary to recent findings, low dose aspirin is effective and medium dose aspirin did not prove superior for inhibiting platelet aggregation after coronary surgery.

Relationship of shuttle walk test and lung cancer surgical outcome.

OBJECTIVE: Surgery remains the treatment of choice in patients with potentially resectable lung carcinoma. Both the British Thoracic Society and American Chest Physician guidelines for the selection of patients with lung cancer surgery suggest the use of a shuttle walk test to predict outcome in patients with borderline lung function. The guidelines suggest that if the patient is unable to walk 250 m during a shuttle walk test, they are high risk for surgery. However, there is no published evidence to support this recommendation. Therefore, we undertook a prospective study to examine the relationship between shuttle walk test and surgical outcome in 139 patients undergoing assessment for possible lung cancer surgery. METHODS: The shuttle walk test was performed in 139 potentially resectable patients, recruited over a 2 year period, prior to surgery. One hundred and eleven patients underwent surgery. Outcome of surgery, including duration of hospital stay, complication and mortality rates was recorded. Student's t-test was used to compare the shuttle walk distance in patients with good and poor outcome from surgery. RESULTS: Mean age of patients undergoing surgery was 69 years (42-85). Mean shuttle walk distance was 395 m (145-780), with a mean oxygen desaturation of 4% (0-14) during the test. Sixty nine patients had a good surgical outcome and 34 had a poor outcome. The shuttle walk distance was not statistically different in the two outcome groups. CONCLUSION: Shuttle walk distance should not be used to predict poor surgical outcome in lung cancer patients, contrary to current recommendations. It is therefore advisable to perform a formal cardiopulmonary exercise test if at all possible. The usefulness of a shuttle walk test might be improved. It could be compared to a predicted value, as for a formal cardiopulmonary exercise test.

Clopidogrel did not inhibit platelet function early after coronary bypass surgery: A prospective randomized trial.

OBJECTIVE: Although the beneficial effect of aspirin prescription after coronary surgery has been established, the efficacy of clopidogrel has never been compared with that of aspirin in the critical early postoperative period. We therefore conducted a prospective, double-blind, randomized controlled trial to compare the efficacies of these antiplatelet regimens. METHODS: Patients undergoing elective primary coronary artery bypass surgery were invited to participate. After the operation, patients were randomized to receive 100 mg aspirin, 325 mg aspirin, or 75 mg clopidogrel tablets daily for 5 days. Our primary outcome measure was platelet aggregation on day 5, expressed as percentage of baseline. Assessment of platelet aggregation was undertaken with the technique of Born. RESULTS: From September 2002 to July 2003, a total of 54 patients were randomized into the study. There were 2 self-withdrawals and 2 protocol violations, leaving 50 patients for analysis, 34 in the aspirin group and 16 in the clopidogrel arm. Compared with baseline, the mean percentage aggregations with collagen on day 5 were 56% for aspirin and 99% for clopidogrel. The mean difference between the two arms was 42% (95% confidence interval 27%-56%) in favor of aspirin. At the same time point, the effective concentration to inhibit 50% aggregation in the samples from patients randomly assigned to receive clopidogrel were not raised for our entire panel of agonists (changes of -0.04 microg/L for collagen, -0.01 micromol/L for epinephrine, and -0.02 micromol/L for adenosine diphosphate). CONCLUSION: Clopidogrel, unlike aspirin, did not inhibit platelet aggregation in the first 5 postoperative days and therefore should not be used as a sole antiplatelet agent early after coronary surgery.