Effect of preoperative aspirin use on mortality in coronary artery bypass grafting patients

Critical Overview on the Benefits and Harms of Aspirin

Aspirin is widely used internationally for a variety of indications, with the most prominent one being that of cardiovascular disease. However, aspirin has also been proposed as a treatment option in a diverse range of conditions such as diabetes mellitus, cancer prevention, and obstetrics. In our overview, we critically appraise the current evidence from recent systematic reviews and meta-analyses covering the benefits of aspirin across these conditions. We also look at evidence that some patients may not derive benefit due to the concept of aspirin resistance. Aspirin is also associated with the potential for significant harm, principally from haemorrhagic adverse events. We critically appraise the threat of haemorrhagic complications, and weigh up these risks against that of any potential benefit.

Decision making after aspirin, clopidogrel and GPIIb/IIIa inhibitor use

The expanding use of antiplatelet agents in patients who undergo coronary bypass grafting raises the problem of balancing the benefit of this treatment and the risk of increased bleeding after surgery. Aspirin and clopidogrel have different mechanisms of actions, but have in common the irreversibility of the inhibition mechanism. Even if platelets half-life is around 10 days, it is not necessary to wait for this period of time. It can be reasonable to discontinue aspirin two to three days and clopidogrel five days before surgery, even if it was recently suggested to reduce the discontinuation interval to two to three days for the clopidogrel as well. GPIIb/IIIa inhibitors have a short acting action. Reasonably, abciximab has to be stopped, when possible, at least 12 hours before surgery, preferably before 24 hours. On the contrary, tirofiban can also be stopped at the moment of skin incision without harmful effects. Very little is known of eptifibatide, but it seems that it is safe to stop it two to four hours before surgery. Patients with acute coronary syndrome do not need to discontinue any antiplatelet treatment.

Peri-operative management of anti-platelet agents

BACKGROUND

Increasing numbers of patients treated with anti-platelet agents are presenting for non-cardiac surgery. We examined the peri-operative management of anti-platelet therapy in patients undergoing elective non-cardiac surgery and the process by which patients received instructions.

METHODS

We interviewed and collected outcome data on 213 consecutive patients aged > or = 45 years presenting for elective non-cardiac surgery at our institution over a 6-week period regarding the peri-operative management of anti-platelet and warfarin therapy.

RESULTS

Anti-platelet therapy was prescribed in 22.5% and warfarin in 5.2% of the study subjects. Aspirin was stopped peri-operatively in 55.3%, while clopidogrel was stopped in the sole patient treated with this. The frequency of anti-platelet agent discontinuation was similar for major and minor surgery. Warfarin was discontinued prior to surgery in all cases. Only 54.2% of those treated with anti-platelet therapy recalled being given instruction regarding pre-operative management of their anti-platelet therapy compared with 90.9% of patients treated with warfarin (P= 0.04). In the absence of instructions, a number of patients made their own decision to stop their aspirin pre-operatively. Post-operatively, only 37% recalled receiving instructions regarding restarting anti-platelet therapy. As a result, three patients failed to do so. In contrast, all those treated with warfarin received clear post-operative instructions.

CONCLUSION

Peri-operative anti-platelet management and communication with patients appears to be sub-optimal. There is a need for standardized processes whereby informed decisions regarding peri-operative anti-platelet therapy are made and communicated clearly to the patients.

Postoperative development of aspirin resistance following coronary artery bypass

BACKGROUND

Aspirin therapy is known to substantially reduce mortality and the rate of ischaemic complications after coronary artery bypass grafting (CABG). Rates of perioperative aspirin resistance cited in the literature are up to 50% and could be influenced by extracorporeal circulation. Thus, aspirin resistance after CABG may have a significant clinical relevance.

MATERIALS AND METHODS

In 59 patients undergoing CABG (on-pump, off-pump and combined procedures) aspirin resistance was investigated by arachidonic acid induced platelet aggregometry. Clinical relevance was assessed with 12-month follow up.

RESULTS

Two types of resistance were observed: A preoperative resistance (despite oral aspirin or in vitro addition) was present in 29% and a postoperative developing type was seen in 49% resulting in only 22% of patients with a 'normal' reaction to aspirin. If patients were already on oral aspirin at admission, the rate of resistance was significantly reduced. Off-pump surgery or pump-times exceeding 120 min had no significant impact on resistance. During the 12-month follow up (98.3%), there were three deaths (one stroke, one intestinal ischaemia, one mediastinitis after postoperative delirium) in patients with the perioperative resistance and none in other patients (P = 0.345). In none of those patients who presented with perioperative aspirin resistance, could this aspirin resistance be demonstrated when tested again after 12 months?

CONCLUSIONS

Aspirin resistance is a transient phenomenon present in the majority of patients undergoing CABG. The three deaths in the resistant group may - although not statistically significant - indicate the possibility of a worse outcome for patients with aspirin resistance.

Risk and management of upper gastrointestinal bleeding associated with prolonged dual-antiplatelet therapy after percutaneous coronary intervention

Prolonged dual-antiplatelet therapy with aspirin and clopidogrel is mandatory after drug-eluting stent implantation because of the potential increased risk of late stent thrombosis. The concern regarding prolonged antiplatelet therapy is the increased risk of bleeding. Gastrointestinal bleeding is the most common site of bleeding and presents a serious threat to patients due to the competing risks of gastrointestinal hemorrhage and stent thrombosis. Currently, there are no guidelines and little evidence on how best to manage these patients who are at high risk of morbidity and mortality from both the bleeding itself and the consequences of achieving optimum hemostasis by interruption of antiplatelet therapy. Managing gastrointestinal bleeding in a patient who has undergone recent percutaneous coronary intervention requires balancing the risk of stent thrombosis against further catastrophic bleeding. Close combined management between gastroenterologist and cardiologist is advocated to optimize patient outcomes.

The Role of Aspirin in Cardiovascular Disease Prevention in Women

Cardiovascular disease is the nation's number one killer of women. Through its actions on platelet inhibition, aspirin is an effective agent for primary and secondary cardiovascular disease prevention and for use with cardiac interventions. However, the evidence for aspirin's effectiveness in women differs by age and indication compared to men. As primary prevention, low dose aspirin is recommended for women over age 65 to reduce the risk of myocardial infarction and stroke while younger women at high risk for stroke may benefit from aspirin. Aspirin has benefits in other selected patient groups, including diabetics and patients presenting with ST segment elevation myocardial infarction (STEMI), non-ST segment elevation myocardial infarction acute coronary syndrome (NSTEMI/ACS), peripheral arterial disease, stroke, coronary artery bypass graft (CABG), and percutaneous coronary intervention (PCI). Alternative platelet therapy using dipyridamole or clopidogrel, alone or with aspirin, provides some improved efficacy for reduction in recurrent events for NSTEMI, ASC and PCI, although bleeding risks may be greater. However, dual antiplatelet therapy is not currently recommended for primary prevention in even high risk subjects. Despite the evidence base and guidelines, the use of aspirin in women remains suboptimal and warrants improved provider and patient awareness.

Appropriate use of drug-eluting stents: balancing the reduction in restenosis with the concern of late thrombosis

Restenosis is a serious occurrence that can lead not only to recurrent angina and repeat revascularisation but also to acute coronary syndromes. Drug-eluting stents revolutionised interventional cardiology owing to their pronounced ability to reduce restenosis compared with bare-metal stents. Attention has now shifted to safety of these devices because of evidence suggesting an association with late stent thrombosis. Findings of randomised clinical trials have not shown that drug-eluting stents result in excess mortality after 4-5 years of follow-up. Current recommendations are that individuals with a drug-eluting stent should receive at least 12 months of uninterrupted dual antiplatelet treatment; patients must understand the importance of this long-term regimen. Patients' assessment should focus on bleeding abnormalities, pre-existing disorders that need anticoagulation treatment, and possible future surgical procedures, since these factors could all contraindicate use of drug-eluting stents. Many people will do well with a bare-metal stent, whereas for individuals with a high likelihood of restenosis and late thrombosis, medical management or surgical revascularisation might be preferred options.

Aspirin in coronary artery bypass surgery: new aspects of and alternatives for an old antithrombotic agent

The success of coronary artery bypass graft surgery (CABG) depends mainly on the patency of the graft vessels. Aortocoronary vein graft disease is comprised of three distinct but interrelated pathological processes: thrombosis, intimal hyperplasia and atherosclerosis. Early thrombosis is a major cause of vein graft attrition during the first month after CABG, while during the remainder of the first year, intimal hyperplasia forms a template for subsequent atherogenesis, which thereafter predominates. Platelets play a crucial role in the pathophysiology of graft thrombosis and aspirin is the primary antiplatelet drug that has been shown to improve vein graft patency within the first year after CABG. Nevertheless, a significant number of grafts still occlude in the early postoperative period despite 'appropriate' aspirin treatment. Moreover, laboratory investigations showed that the expected inhibition of platelet function is not always achieved. This has been called 'aspirin nonresponse' or 'aspirin resistance', although a uniform definition is lacking. The finding that a considerable number of patients show an impaired antiplatelet effect of aspirin after CABG brought new insight into the discussion concerning poor patency rates of bypass grafts: the early period after CABG shows a coincidence of an increased risk for bypass thrombosis (amongst others, due to platelet activation and endothelial cell disruption of the graft) and an increased prevalence of aspirin resistance. Hitherto, the underlying mechanisms of aspirin resistance are uncertain and largely hypothetical; amongst others, increased platelet turnover, enhanced platelet reactivity, systemic inflammation, and drug-drug interaction are discussed. Up to now available data concerning the clinical outcome of aspirin resistant CABG patients are limited, and there is evidence that platelets of patients with graft thrombosis are more likely to be resistant to aspirin compared with patients without thrombotic events. Many publications concerning aspirin resistance are available today, but reports addressing this topic in CABG patients are sparse. This review summarises recent insights into the antiplatelet treatment after CABG and describes the clinical benefit, but also the therapeutic failure of the well-established drug aspirin. Moreover, possible pharmacological approaches to improve antithrombotic therapy in aspirin nonresponders among CABG patients are discussed.

Perioperative use of cardiac medical therapy among patients undergoing coronary artery bypass graft surgery: a systematic review

BACKGROUND

The use of perioperative cardiac medical therapy among patients undergoing coronary artery bypass graft surgery (CABG) has not been closely examined.

OBJECTIVES

The objective of this study was to systematically review the medical literature examining the effects of perioperative cardiac medical therapy on clinical outcomes among patients undergoing CABG.

METHODS

Using the Medline database and online clinical trial databases, we reviewed all randomized controlled trials (RCTs) and observational studies examining the effect of perioperative angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, antilipid agents (including statins), aspirin, beta-blockers, and calcium-channel blockers on clinical outcomes.

RESULTS

Our review identified 27 studies (6 RCTs, 21 observational studies), involving >700,000 patients, that examined the impact of perioperative medical therapy on clinical outcomes after CABG. Although studies provide conflicting results, the literature suggests that perioperative aspirin use may decrease inhospital mortality and myocardial infarction, whereas perioperative angiotensin-converting enzyme inhibitor use does not appear to be beneficial. Perioperative statin use reduces all-cause mortality at 30 days and cardiac death at 60 days and 1 year post-CABG but does not appear to reduce myocardial infarction or congestive heart failure rates. Multiple studies have demonstrated that pre- and postoperative beta-blockers are associated with a decrease in atrial fibrillation. In addition, beta-blockers may reduce inhospital and 30-day mortality, although these results are not consistent across all studies. Calcium-channel blockers do not appear to improve inhospital or 30-day mortality. No studies examined the perioperative use of angiotensin II receptor blockers or nonstatin antilipid agents among CABG patients.

CONCLUSIONS

The perioperative use of cardiac medical therapy among CABG patients remains understudied. Given their proven benefits among patients with cardiovascular disease and their potential to improve outcomes among CABG patients, further studies, particularly large RCTs, are needed.

Does the Use of Preoperative Aspirin Increase the Risk of Bleeding in Patients Undergoing Coronary Artery Bypass Grafting Surgery? Systematic Review and Meta-Analysis

BACKGROUND

The traditional recommendation has been to stop Aspirin seven to 10 days prior to coronary artery bypass surgery to reduce the potential risk of bleeding. A few reports have shown that Aspirin did not increase the risk of bleeding and may be beneficial to be continued until the time of surgery. The objective of this review was to evaluate the effect of preoperative Aspirin on bleeding in patients undergoing elective bypass surgery.

METHODS

A meta-analysis of 10 randomized and nonrandomized studies reporting comparisons between Aspirin and control was undertaken. The primary outcome was the total amount of postoperative chest tube drainage. Secondary outcomes were the number of units of packed red blood cell transfusion, platelet transfusion, fresh frozen plasma transfusion, and number of patients reexplored for bleeding.

RESULTS

Ten studies, involving 1748 patients, met the inclusion criteria for this review of whom 913 were in the Aspirin group and 835 were in the control group. Pooling the results of all studies showed a significant increase in blood loss and transfusion of red blood cells and fresh frozen plasma in the Aspirin group (p < 0.05). There was no significant difference between the two groups in the rate of platelet transfusion, or the incidence of reexploration (p > 0.05). Included studies were heterogeneous and of low methodological quality.

CONCLUSION

Aspirin is associated with increased chest tube drainage and may be associated with a greater requirement for blood products. High-quality prospective studies are warranted to reassess the effect of Aspirin on important postoperative outcomes.

Discontinuation of perioperative antiplatelet and anticoagulant therapy in stroke patients

Growing evidence suggests that perioperative withdrawal of ASA for secondary stroke prevention increases thromboembolic risk without the associated benefit of decreased bleeding complications. ASA maintenance is acceptable in many procedures, including invasive ones. Many procedures, in particular ophthalmologic, dermatologic, and dental surgeries, also are safe while continuing oral AC. Warfarin has been continued successfully even in some surgeries that have high bleeding risk. When the risk is too high, temporary bridging therapy with LWMH is safe in many populations. Although the exact thromboembolic risks associated with temporary cessation of AP and AC are unknown and likely low, morbidity and mortality associated with thromboembolism are high. Further studies investigating the risks and benefits of maintaining AP and AC during procedures, particularly invasive ones, are needed. Meanwhile, it is critical that physicians understand the risks and benefits of perioperative AP and AC and the variety of procedures in which these agents can be safely continued.

Balancing the benefit and risk of oral antiplatelet agents in coronary artery bypass surgery

Concern about possible hemorrhagic complications arising from use of oral antiplatelet agents in immediate proximity to coronary artery bypass graft (CABG) surgery leads many clinicians to avoid or discontinue these agents preoperatively. Recent evidence suggests that aspirin and clopidogrel can be used with relative safety in the preoperative period; dual antiplatelet therapy in the 5 days immediately preceding CABG surgery results in a moderate and variable increase in the risk of procedural bleeding. This modest hemorrhagic risk may be acceptable, given the clinical benefits of sustained antiplatelet therapy in preventing graft occlusion and ischemic complications pre- and post-CABG. Because the bleeding risk with aspirin is dose dependent, use of a low dose is preferred post-CABG.

Antithrombotic therapy in cardiac surgery

PURPOSE

To review the perioperative management of antithrombotic therapy in cardiac surgery, including the management of cardiopulmonary bypass (CPB) and off-pump surgery.

METHODS

A review of the relevant English literature over the period 1975-2005 was undertaken, in addition to a review of international practices in antithrombotic therapy in cardiac surgery.

PRINCIPAL FINDINGS

Cardiopulmonary bypass is required in most procedures and makes anticoagulation mandatory. Anticoagulation is, usually, achieved with unfractionnated heparin (UFH). Unfractionated heparin is monitored by point-of-care (POC) testing, such as the activated clotting time or the determination of heparin concentration. The target values of both tests remain empirical, with no clearly validated thresholds. The target value needs to be adjusted according to the POC test, given significant variations between devices and activators. After CABG, the need for antiplatelet therapy is well demonstrated, in order to limit the risk of postoperative death or ischemic events, and improve venous graft patency. Immediately after valvular surgery, antithrombotic therapy should take into account the specific risk carried by each patient and by each prosthetic device. The risk of venous thromboembolism, though poorly defined, is also present in the postoperative period and may require additional attention. Given the frequent exposure to UFH, occurrence of heparin-induced thrombocytopenia is not infrequent in these patients and requires careful individual management.

CONCLUSIONS

Antithrombotic therapy is an essential component of cardiac surgery. Yet, with the exception of antiplatelet agents in CABG patients, antithrombotic therapy is often based on the clinical experience of medical teams more than on an evidence-based assessment of the literature.

Thrombosis and Coagulation: Operative Management of the Anticoagulated Patient

The surgical management of the anticoagulated patient requires an understanding of the fundamentals of blood thrombosis, the mechanisms that enable anticoagulants to work, and the indications for anticoagulation. As percutaneous cardiac and peripheral procedures become increasingly sophisticated, we can expect to encounter more patients on aspirin and clopidogrel. Management strategies will require continued appraisal of available literature for evidence-based surgical practice. This article summarizes how coagulation takes place and explains the role of certain agents that alter coagulation, such as aspirin, clopidogrel, warfarin, heparin and low-molecular-weight heparin. The article also discusses thrombosis risks involving patients with nonvalvular atrial fibrillation, patients with mechanical heart valves and patients with a history of deep vein thrombosis.

Clopidogrel and Bleeding After Coronary Artery Bypass Graft Surgery

BACKGROUND

There is evidence that clopidogrel (with or without aspirin) confers superior outcomes in patients with coronary artery disease. The purpose of this study is to review the effect of preoperative clopidogrel administration on clinical outcome, bleeding complications and resource utilization after coronary artery bypass graft surgery.

METHODS

Patient data were prospectively collected from 919 patients who had isolated coronary surgery during the period 2000 to 2003. Outcome comparisons were studied, firstly between patients who received preoperative clopidogrel with those who did not, and secondly between patients on clopidogrel only, aspirin only, both or neither medications.

RESULTS

Twenty-four patients (2.6%) were on clopidogrel only, 598 (65.1%) were on aspirin only, 61 (6.6%) were on both, and 236 (25.7%) were on neither. Clopidogrel (n = 85) versus no clopidogrel (n = 834): there were no significant differences in the off-pump patients. In the on-pump patients, the clopidogrel group had significantly increased bleeding (p = 0.02), blood transfused (p = 0.01), intensive care (p = 0.03), and hospital stays (p = 0.03). There were no significant differences in surgical reexploration, perioperative myocardial infarction, intraoperative balloon pump use, inotropic support or 30-day mortality. Clopidogrel versus aspirin versus both versus neither: patients on both clopidogrel and aspirin had significantly more postoperative bleeding than patients on aspirin alone or on neither medication.

CONCLUSIONS

The preoperative use of clopidogrel in patients undergoing coronary artery bypass graft surgery showed limited clinical benefits; however, its use significantly increased the risk of bleeding, blood transfusion, and resource utilization.

Preoperative Aspirin Therapy Is Associated With Improved Postoperative Outcomes in Patients Undergoing Coronary Artery Bypass Grafting

Background— Aspirin is beneficial in the setting of atherosclerotic cardiovascular disease. There are limited data evaluating preoperative aspirin administration preceding coronary artery bypass grafting and associated postoperative outcomes.

Methods and Results— Using prospectively collected data from 1636 consecutive patients undergoing first-time isolated coronary artery bypass surgery at our institution from January 2000 through December 2002, we evaluated the association between aspirin usage within the 5 days preceding coronary bypass surgery and risk of adverse in-hospital postoperative events. A logistic regression model, which included propensity scores, was used to adjust for remaining differences between groups. Overall, there were 36 deaths (2.2%) and 48 adverse cerebrovascular events (2.9%) in the postoperative hospitalization period. Patients receiving preoperative aspirin (n=1316) had significantly lower postoperative in-hospital mortality compared with those not receiving preoperative aspirin [1.7% versus 4.4%; adjusted odds ratio (OR), 0.34; 95% CI, 0.15 to 0.75; P =0.007]. Rates of postoperative cerebrovascular events were similar between groups (2.7% versus 3.8%; adjusted OR, 0.67; 95% CI, 0.32 to 1.50; P =0.31). Preoperative aspirin therapy was not associated with an increased risk of reoperation for bleeding (3.5% versus 3.4%; P =0.96) or requirement for postoperative blood product transfusion (adjusted OR, 1.17; 95% CI, 0.88 to 1.54; P =0.28).

Conclusions— Aspirin usage within the 5 days preceding coronary artery bypass surgery is associated with a lower risk of postoperative in-hospital mortality and appears to be safe without an associated increased risk of reoperation for bleeding or need for blood product transfusion.

Cardiac surgery in patients on antiplatelet and antithrombotic agents

The widespread application of antithrombotic agents carries significant potential for inducing excessive peri-operative hemorrhage during cardiac surgery. Specific surgical and medical strategies can be employed to attenuate this bleeding. These antithrombotic agents and anti-hemorrhagic measures will be reviewed in depth.

Aspirin decreases vascular endothelial growth factor release during myocardial ischemia

BACKGROUND

Vascular Endothelial Growth Factor (VEGF) is an important angiogenesis factor involved in pathophysiology of cardiovascular diseases. Controlling this factor's level in the serum might have significant prognostic outcomes.

METHODS

Twenty-four patients undergoing coronary artery bypass grafting were prospectively categorized into two groups according to aspirin administration before surgery. Vascular Endothelial Growth Factor levels were compared and correlated and adjusted with platelets count between two groups in the serum, before and after the surgery. Serum creatine kinase (CK) levels were determined before and after the operation in parallel to other clinical data.

RESULTS

Vascular Endothelial Growth Factor levels were significantly lower in patients of the aspirin group compared to those of the non-aspirin group; 94+/-61 vs. 241+/-118 pg/ml, p=0.0003, respectively, this-despite an absence of difference in the platelet count between the groups. These titers decreased postoperatively in both groups, 94+/-61 to 10+/-9 pg/ml, p=0.001 in aspirin group and from 241+/-118 to 84+/-54 pg/ml, p=0.001 in control group. Serum creatine kinase levels were higher in the non-aspirin group, 214+/-83 u/l compared to 70+/-32 u/l in the aspirin group. Creatine kinase levels increased significantly postoperatively in both groups; however, the aspirin group had a significantly lower creatine kinase levels compared to non-aspirin group, 107+/-51 vs. 401+/-127 u/l, respectively, p=<0.0001. A significant correlation was seen between VEGF levels and platelets count in both groups, r=0.5.

CONCLUSIONS

Aspirin treated patients have lower Vascular Endothelial Growth Factor titer levels in the perioperative course. This difference between the aspirin and the non-aspirin group is not accounted for by the platelets count.

Reexploration for bleeding after coronary artery bypass surgery: risk factors, outcomes, and the effect of time delay

BACKGROUND

We aimed to identify risk factors for reexploration for bleeding after surgical revascularization in our practice. We also looked at the impact of resternotomy and the effect of time delay on mortality and other in-hospital outcomes.

METHODS

In all, 2,898 consecutive patients undergoing coronary artery bypass grafting between April 1999 and March 2002 were retrospectively analyzed from our cardiac surgery registry. Multivariate logistic regression analysis was used to identify risk factors for reexploration for bleeding. To assess the effect of preoperative aspirin and heparin, reexploration patients were propensity matched with unique patients not requiring reexploration. We carried out a casenote review to ascertain the timing and causes for bleeding in patients undergoing resternotomy.

RESULTS

Eighty-nine patients (3.1%) underwent reexploration for bleeding. Multivariate analysis revealed smaller body mass index (p = 0.003), nonelective surgery (p = 0.022), 5 or more distal anastomoses (p = 0.035), and increased age (p = 0.041) to have increased risks. Propensity-matched analysis showed that preoperative use of aspirin (p = 0.004) and heparin (p = 0.001) were associated with increased risk in the on-pump coronary surgery group only. Patients requiring resternotomy had a significantly greater need for inotropic agents (p < 0.001), and longer intensive care unit stay (p < 0.001) and postoperative stay (p < 0.001) than their propensity-matched controls. However, there was no significant difference in the mortality rate. Adverse outcomes were significantly higher when patients waited more than 12 hours after return to the intensive care unit for resternotomy.

CONCLUSIONS

Risk factors for reexploration for bleeding after coronary artery bypass grafting include older age, smaller body mass index, nonelective cases, and 5 or more distal anastomoses. Preoperative aspirin and heparin were risk factors for the on-pump coronary artery surgery group. Patients needing reexploration are at higher risk of complications if the time to reexploration is prolonged. Policies that promote early return to the operating theater for reexploration should be encouraged.

[Non-opioid analgesics for perioperative pain therapy. Risks and rational basis for use]

Non-opioid analgesics play a central role in the management of postoperative pain. In this review, the pharmacology, the analgesic efficacy and the side-effects of non-opioid analgesics are summarized. First, the pharmacology of diclofenac, acetyl salicylic acid, dipyrone, acetaminophen and the COX-2 inhibitors is described. Second, the analgesic efficacy of non-opioid analgesics is analyzed for moderate pain (e.g. ambulatory surgery) and for moderate to severe pain (e.g. abdominal surgery-in combination with opioids). There is limited evidence for an additive analgesic effect of two non-opioid analgesics. Third, the major side-effects of non-opioid analgesics are discussed in relation to the pathophysiology, the frequency and the clinical relevance of these effects. In particular, side-effects on the gastrointestinal tract (ulcus formation), on coagulation (bleeding and thrombosis), on the renal (renal insufficiency), the pulmonary (bronchospasm) and the hematopoetic systems (agranulocytosis) are described. Recommendations for the clinical use of non-opioid analgesics for perioperative pain therapy are given.

Beneficial effect of aspirin on renal function post-cardiopulmonary bypass

Urine thromboxane, plasma creatinine, and creatinine clearance were determined perioperatively in 20 patients undergoing coronary bypass surgery. Ten patients took aspirin until the day of surgery, and 10 discontinued aspirin at least one week before surgery. A significant increase in urine thromboxane following establishment of cardiopulmonary bypass was observed only in the control group. Plasma creatinine increased in the control group on the 1st postoperative day (from 81.9 +/- 13.2 to 97.6 +/- 13.2 micromol.L(-1), p = 0.02) and decreased next day to the preoperative level (82.7 +/- 9 micromol.L(-1), p = 0.03). In the aspirin group, creatinine remained unchanged on the 1st postoperative day (89.4 +/- 14.2 vs. 87.2 +/- 7.7 micromol.L(-1), p = 0.6), and increased significantly on the 2nd day (101.4 +/- 8.5 micromol.L(-1), p = 0.01). The aspirin group had higher creatinine levels (p < 0.0001) and lower creatinine clearance (60.2 +/- 16.5 vs. 82 +/- 25.7 mL.min(-1), p < 0.0001) than the control group on the 2nd postoperative day. A significant positive correlation was seen between urine thromboxane and creatinine on day 2 in both groups (r = 0.6). Aspirin administrated before coronary surgery may have a beneficial effect on renal function, probably mediated by its antiplatelet activity and thromboxane inhibition.

Antiplatelet therapy in aneurysmal subarachnoid hemorrhage: a systematic review

BACKGROUND AND PURPOSE

Observational studies suggest that platelet inhibitors reduce the risk of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage and thereby have a beneficial effect on clinical outcome. Robust evidence, however, is lacking. We performed a systematic meta-analysis to determine whether antiplatelet therapy has a beneficial effect after SAH.

METHODS

We searched Medline and the Cochrane Library to identify all randomized controlled trials of antiplatelet drugs versus control and calculated relative risks with corresponding 95% confidence intervals (CIs) for poor outcome (dependence or death), the occurrence of DCI, and the occurrence of any intracranial hemorrhage.

RESULTS

We included 5 trials totaling 699 patients. The overall relative risk for poor outcome was 0.87 (95% CI, 0.65 to 1.17); for the occurrence of DCI (reported in 3 of the 5 studies), 0.65 (95% CI, 0.47 to 0.89); and for the occurrence of intracranial hemorrhage, 1.19 (reported in 4 of the 5 studies) (95% CI, 0.76 to 1.85).

CONCLUSIONS

Our data indicate that antiplatelet drugs reduce the risk of DCI in patients with subarachnoid hemorrhage. A randomized clinical trial is warranted to assess the effect on overall outcome.

Antiplatelet therapy in peripheral arterial disease. Consensus statement

OBJECTIVES

Antiplatelet agents are commonly prescribed to reduce the risk of myocardial infarction, stroke and graft occlusion in patients with peripheral arterial disease (PAD). The objective was to summarise current evidence and provide recommendations on the use of antiplatelet agents in PAD.

METHODS

A consensus group was assembled including 20 specialists from a variety of fields involved in the management of patients with PAD. Data was circulated in a systematic manner prior to a main consensus meeting held in November 2001. The document subsequently produced was circulated within the group to ensure agreement in the interpretation and presentation of its findings.

RESULTS

Consensus recommendations are provided in 7 common or contentious scenarios in PAD. The recommendations are graded to reflect the evidence available and interpretations of the group. Although the document provides recommendations, it is stressed that they must be interpreted in the light of individual patient circumstances.

CONCLUSION

Antiplatelet agents have an important role in the management of patient with PAD. Although this document provides consensus recommendations, the optimum treatment in many scenarios remains unclear due to a lack of focussed clinical trials in PAD.

Effect of preoperative aspirin use in off-pump coronary artery bypass operations

BACKGROUND

The effect of preoperative aspirin use until the day of operation on mortality rate and bleeding risks in patients who had on-pump coronary artery bypass operation has been well documented. However, the effect of aspirin use in patients undergoing off-pump coronary artery bypass operation (OPCAB) with regard to postoperative blood loss and morbidity has not been studied. We aimed to determine the effects of continuing aspirin therapy preoperatively.

METHODS

We performed a retrospective study of 340 patients who had first-time OPCAB between January 1998 and September 2001. A propensity score for receiving aspirin until the day of operation was constructed from core patient characteristics. All aspirin users (n = 170) were matched with unique 170 nonaspirin users by identical propensity score. The primary outcome measures were in-hospital mortality rate and hemorrhage-related outcomes (postoperative blood loss in the intensive care unit, reexploration for bleeding, and blood product requirements). Secondary outcome measures were stroke, myocardial infarction, gastrointestinal bleeding, and sternal wound infections.

RESULTS

There were no differences in patient characteristics between aspirin users and nonaspirin users. The average postoperative blood loss (845 mL versus 775 mL; p = 0.157) and the rate of reexploration for bleeding (3.5% versus 3.5%; p > 0.99) were similar in aspirin users and nonaspirin users. We found no significant difference between blood product requirements for the two groups. Similarly, we found no significant difference in the incidence of the secondary outcomes.

CONCLUSIONS

Preoperative aspirin did not increase bleeding-related complications, mortality rate, or other morbidities in patients who had off-pump coronary artery operation.

Increased blood product use among coronary artery bypass patients prescribed preoperative aspirin and clopidogrel

BACKGROUND

The administration of antiplatelet drugs before coronary artery bypass graft surgery (CABG) is associated with an increased risk of major hemorrhage and related surgical reexploration. Little is known about the relative effect of combined clopidogrel and aspirin on blood product use around the time of CABG. We evaluated the associated risk between the combined use of aspirin and clopidogrel and the transfusion of blood products perioperatively.

METHODS

We retrospectively studied a cohort of 659 individuals who underwent a first CABG, without concomitant valvular or aortic surgery, at a single large Canadian cardiac surgical centre between January 2000 and April 2002. The four study exposure groups were those prescribed aspirin (n = 105), clopidogrel (n = 11), the combination of both (n = 46), or neither drug (n = 497), within 7 days prior to CABG. The primary study outcome was the excessive transfusion of blood products during CABG and up to the second post-operative day, defined as > or = 2 units of packed red blood cells (PRBC), > or = 2 units of fresh frozen plasma, > or = 5 units of cryoprecipitate or > or = 5 units of platelets. Secondary outcomes included the mean number of transfused units of each type of blood product.

RESULTS

A greater mean number of units of PRBC were transfused among those who received clopidogrel alone (2.9) or in combination with aspirin (2.4), compared to those on aspirin alone (1.9) or neither antiplatelet drug (1.4) (P = 0.001). A similar trend was seen for the respective mean number of transfused units of platelets (3.6, 3.7, 1.3 and 1.0; P < 0.001) and fresh frozen plasma (2.5, 3.1, 2.3, 1.6; P = 0.01). Compared to non-users, the associated risk of excessive blood product transfusion was highest among recipients of aspirin and clopidogrel together (adjusted OR 2.2, 95% CI 1.1-4.3). No significant association was seen among lone users of aspirin (adjusted OR 1.0, 95% CI 0.6-1.6) or clopidogrel (adjusted OR 0.7, 95% CI 0.2-2.5), compared to non-users.

CONCLUSIONS

While combined use of aspirin and clopidogrel shortly before CABG surgery may increase the associated risk of excess transfusion of blood products perioperatively, several study limitations prevent any confident conclusions from being drawn. Beyond challenging these findings, future research might focus on the value of both intraoperative monitoring of platelet function, and the effectiveness of antifibrinolytic agents, at reducing the risk of postoperative bleeding.

The effect of clopidogrel in combination with aspirin when given before coronary artery bypass grafting

OBJECTIVES

This study was designed to evaluate the effect of preoperative clopidogrel on coronary artery bypass graft surgery (CABG) outcomes.

BACKGROUND

Clopidogrel in combination with aspirin, given before percutaneous coronary intervention, has become the standard for stent thrombosis prevention. Some premedicated patients, however, are found to have surgical disease on angiography, and irreversible platelet inhibition becomes a concern for upcoming CABG.

METHODS

We prospectively studied 224 consecutive patients undergoing nonemergent first-time CABG, and compared those with preoperative clopidogrel exposure within seven days (n = 59) to those without exposure (n = 165).

RESULTS

The groups were comparable in age, gender, body surface area, preoperative hematocrit, preoperative prothrombin time and prior myocardial infarction. The clopidogrel group had higher 24-h mean chest tube output (1,224 ml vs. 840 ml, p = 0.001), and more transfusions of red blood cells (2.51 U vs. 1.74 U, p = 0.036), platelets (0.86 U vs. 0.24 U, p = 0.001) and fresh frozen plasma (0.68 U vs. 0.24 U, p = 0.015). Moreover, reoperation for bleeding was 10-fold higher in the clopidogrel group (6.8% vs. 0.6%, p = 0.018). The clopidogrel group also had less extubation within 8 h (54.2% vs. 75.8%, p = 0.002) and a trend towards less hospital discharge within five days (33.9% vs. 46.7%, p = 0.094).

CONCLUSIONS

Clopidogrel in combination with aspirin before CABG is associated with higher postoperative bleeding and morbidity. These findings raise concern regarding the routine administration of clopidogrel before anticipated coronary stent implantation.