Aspirin


 [This monograph covers aspirin as a single antiplatelet or aspirin in combination with dipyridamole. 

For patients taking Aspirin and Clopidogrel / Prasugrel / Ticagrelor – see Dual Antiplatelet Therapy (DAPT) monograph

For patients taking aspirin for analgesia – see Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) including Cyclo-oxygenase-2 (COX-2) Selective Inhibitors (Oral) monograph]

  Issues for Surgery


For prevention of cardiovascular events – risk of major adverse cardiovascular events (MACE) if omitted.

Risk of bleeding and/or complications of bleeding if continued.


  Advice in the Perioperative period


Elective Surgery

Cardiac Surgery
Multi-disciplinary Team to evaluate if benefit outweighs risk of bleeding and decide if aspirin should be continued or stopped pre-operatively1.

Non-cardiac Surgery
High dose (>150mg): Consider reducing to low dose for 7 days pre-operatively (bleeding risk is lower with 75mg-150mg doses and antithrombotic impact is comparable to higher doses2).

Low dose (≤150mg): Continue

EXCEPT:

  • procedures associated with high risk of bleeding or complications of bleeding (e.g. spinal surgery, some ophthalmological and neurosurgical procedures3)
  • individuals who refuse blood transfusion for religious reasons (e.g. Jehovah’s Witness1)

In these circumstances consideration should be given to stopping 7 days pre-operatively.

Emergency Surgery

If patient has received doses of aspirin in past 7 days be aware of potential for increased surgical bleeding.

Patient Undergoing Surgery Associated with Unacceptably High Risk of Bleeding

  • consider withholding aspirin and delaying surgery for 3 days to allow partial restoration of platelet function (see Further Information)
  • if this is not possible consider platelet transfusion to indirectly reverse the effects of aspirin by increasing the total circulating pool of platelets1.

Perioperative Considerations

Neuraxial (Spinal/Epidural) Anaesthesia or Lumbar Puncture
Aspirin, when given in isolation does not increase the risk of spinal epidural haematoma and is not a contraindication to neuraxial anaesthesia4. However, concomitant use of low molecular weight heparin (LMWH) may have an additive bleeding risk, therefore pre-operative thromboprophylaxis should be prescribed with caution in patients taking aspirin who are likely to receive neuraxial anaesthesia4.

Post-operative Advice

If stopped pre-operatively, restart as soon as possible post-operatively once haemostasis secure.


  Interaction(s) with Common Anaesthetic Agents


None5, 6.


  Interaction(s) with other Common Medicines used in the Perioperative Period


Non-Steroidal Anti-inflammatory Drugs (NSAIDs)

NSAIDs may have an additive effect on the risk of bleeding (including gastrointestinal bleeding) when given with aspirin5; consider gastroprotection if other risk factors for gastrointestinal bleeding are present6.

Concomitant administration of standard NSAIDs, which are non-selective reversible cyclooxygenase (COX)-1 inhibitors (e.g. naproxen, ibuprofen), may lead to impaired efficacy of aspirin through competition for binding sites7. The Commission on Human Medicines advises there may be a small increased risk of thrombotic events with non-selective NSAIDs, particularly when used at high doses and for long-term treatment6.

Low Molecular Weight Heparin (LMWH) / Unfractionated Heparin (UFH)

LMWHs and UFH are predicted to increase the risk of bleeding events when given with aspirin; manufacturer advises use with caution5.


  Further Information


Mode of Action

Aspirin exerts its antiplatelet effect by inhibiting cyclo-oxygenase (COX) thus preventing prostaglandin-mediated production of thromboxane A2, which is responsible for platelet activation and aggregation. The irreversible inhibition of cyclo-oxygenase means the pharmacological effects persist until platelets are regenerated. After discontinuation of aspirin intake platelet function can be expected to increase by 10-15% a day as a result of new platelet formation2. Within 3-4 days more than 30% of irreversibly inhibited platelets will be replaced; in patients with a normal platelet count this is usually sufficient to return haemostasis to normal4.

Risk of Major Adverse Cardiovascular Events (MACE)

Non-adherence or withdrawal of aspirin in non-surgical patients is associated with a three-fold increase in MACE; this rises to an 89-fold increased incidence in patients with coronary artery stents8. This increased incidence is thought to be due to rebound increases in thromboxane A2 activity leading to increased platelet aggregation2. Patients with diabetes, acute coronary syndrome or undergoing cardiac surgery are associated with high platelet reactivity2. The time between aspirin withdrawal and adverse event was found to be 8.5 days for acute coronary syndrome and 14.3 days for cerebrovascular events9. It is possible that the risk of discontinuation is further increased in the perioperative period as surgery promotes an inflammatory state that increases platelet reactivity10.

Risk of Bleeding

Pre-operative aspirin continuation increases the baseline rate of bleeding by fifty percent in a large meta-analysis of pooled data from several underpowered studies9. However, whilst the prevalence of bleeding was higher in patients who continued aspirin the severity of bleeding and bleeding associated mortality was not increased, apart from in a study of patients undergoing transurethral resection of the prostate (TURP)9. With recent changes in surgical technique, and the use of isotonic saline rather than glycine irrigation, bleeding complications from TURP may now be lower than in 2005 when this meta-analysis was conducted.


  References


  1. Ferraris V, Saha S, Oestreich J et al. 2012 Update to The Society of Thoracic Surgeons Guideline on Use of Antiplatelet Drugs in Patients Having Cardiac and Noncardiac Operations. Ann Thorac Surg. 2012; 94:1761–81
  2. Koenig-Oberhuber V & Filipovic M. New antiplatelet drugs and new oral anticoagulants. British Journal of Anaesthesia. 2016; 117 (s2):ii74-ii84
  3. Kristensen S, Knuuti J, Saraste A. et al. 2014 ESC/ESA Guidelines on non-cardiac surgery: cardiovascular assessment and management: The Joint Task Force on non-cardiac surgery: cardiovascular assessment and management of the European Society of Cardiology (ESC) and the European Society of Anaesthesiology. European Heart Journal. 2014; 35:2383–2431
  4. Gogarten W, Vandermeulen R, Van Aken H et al. Regional anaesthesia and antithrombotic agents: recommendations of the European Society of Anaesthesiology Eur J Anaesthesiol. 2010; 27:999–1015
  5. Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 18th August 2019]
  6. Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. http://www.medicinescomplete.com [Accessed on 18th August 2019]
  7. Hall R & Mazer CD. Antiplatelet Drugs: A Review of Their Pharmacology and Management in the Perioperative Period, Anesth Analg. 2011; 112:292-318
  8. Biondi-Zoccai G, Lotrionte M, Agostoni P et al. A systematic review and meta-analysis on the hazards of discontinuing or not adhering to aspirin among 50,279 patients at risk for coronary artery disease. European Heart Journal. 2006;27(22): 2667–2674
  9. Burger W, Chemnitius J, Kneissl G et al. Low-dose aspirin for secondary cardiovascular prevention - Cardiovascular risks after its perioperative withdrawal versus bleeding risks with its continuation - Review and meta-analysis. Journal of Internal Medicine. 2005;257(5):399–414
  10. Gerstein N, Schulman P, Gerstein W et al. Should more patients continue aspirin therapy perioperatively? Clinical impact of aspirin withdrawal syndrome. Annals of Surgery. 2012;255(5):811–819