Perioperative Optimisation – Fasting and Medications

April 24, 2014

Proper perioperative management aims to minimize complications in the operating and recovery rooms, to reduce postoperative pain, and to accelerate convalesence. Routinely used medications have many potential interactions with drugs used during anaesthesia, but most are safer to be continued. Many medications must be continued through the perioperative period and resumed during convalesence. This is increasingly important for our ageing population.

Common drugs that have been associated with withdrawal symptoms when discontinued preoperatively include beta-blockers, selective serotonin reuptake inhibitors (SSRIs), clonidine, statins, and corticosteroids. When fasting the last dose can be taken with a sip of clear liquid up to 2 hours prior to the procedure.

Herbal medications should be stopped at least 7 days before surgery, owing to the uncertainly over their actual contents.

44% of surgical patients are on medications prior to surgery.[1] Cardiac medications are the largest proportion (41%). Almost 50% of drugs were omitted on the day of surgery, and on the first day after the operation 33% of the medications were withheld – mostly inappropriately. Reasons included Fasting (49%), Failure of the admitting doctor to prescribe (29%), Drug withheld on order of medical staff (10%), Drug unavailable in pharmacy or not delivered to the ward (1%), Gastrointestinal tract operation with prolonged ileus (3%), and Unknown (8%).


  • Asthma/ COAD: continue regular doses (usually ‘preventers’). Give a dose of reliever (salbutamol) before coming to the holding bay
  • Postoperative analgesia: Judicious use of narcotics and diligent monitoring for respiratory depression is important in patients with respiratory compromise.
  • Smoking. Counsel patients on the effects of smoking and urge them to stop
  • Long-term steroid therapy: increase the dose on the day of surgery (hydrocortisone 100 mg q8h for 24 h), then decrease the dose by 50% every day until back to the usual.


  • Ischaemic Heart Disease: very important to continue medications, to reduce cardiac ‘strain’ and angina/ heart attack risk. Stopping B-blockers increases cardiac risk. Mangano et al showed that for patients who have or are at high risk for coronary artery disease and undergo noncardiac surgery, treatment with atenolol during hospitalization can reduce mortality and the incidence of cardiac complications for at least 2 years after the surgery.[2]
  • Antihypertensives: Administer all on the day of surgery. Diuretics possibly should not be administered on the day of surgery (because of the potential adverse interaction of volume depletion, potassium derangement, and anaesthetic agents).
  • ACE inhibitors possibly should be discontinued the day before surgery because the renin-angiotensin-aldosterone system (RAAS) is involved in maintaining normal blood pressure. Hemodynamic instability has been described during anaesthesia.[3, 4, 5]
  • For patients unable to take oral medications, parenteral alternatives must be used.
  • Perioperative management of pain, anxiety, hypoxia, and hypothermia with rewarming are key to maintaining normotension and minimising cardiac strain.
  • Congestive heart failure: Preoperative CHF is the strongest predictor of postoperative pulmonary oedema (1-6% of patients), which has a mortality rate of 15-20%. Specialised management is warranted for major surgery.
  • Heart valve prostheses: anticoagulation management is important. Usually heparin (stopped 6-12 hours preop) will be substituted for warfarin (stopped 3-5 days prior). Both are usually restarted 6-24 hours postop. Specialised management is warranted for major surgery.
  • Arrhythmia: patients on long-term therapy for supraventricular tachycardia should receive their usual medication.


  • Diabetes: higher risk of infections and cardiac complications. Long-acting Insulin is usually still required, at half usual dose. 4-hrly BSL’s are required. Short-acting insulin (e.g. Actrapid) is stopped. Tablets are usually discontinued. Normal doses are resumed once eating normally.
  • Thyroid: continue usual medication, although stopping is of little consequence (long half life).
  • Contraceptive Pill and HRT: these are ideally stopped 4-6 weeks prior to major surgery, and restarted 2 weeks after recovery to reduce the risk of DVT/ PTE (combined effects of hormones and the hypercoagulable state, which accompanies surgical stress and postoperative immobility).
  • Hydrocortisone/ Steroids: usually require increased doses to help the body respond to the stress of surgery (for 2-3 days for major surgery) – see ‘Breathing’ above.


  • Continue anti-acid medications to reduce stomach acid and aspiration risk. Aspiration has a high morbidity and mortality.
  • Fasting: 6 hours for food, 4 hours for liquids, 2 hours for water/ tablets. Patients fasted prematurely should be given water/ liquids (and regular analgesia) after consultation with anaesthetist/ surgeon.


  • Analgesia: continue regular medications (including long-acting). These can be tapered over the following 1-2 weeks as the patient recovers from surgery.
  • Antidepressants: continue. SSRI’s may interact with tramadol.
  • Benzodiazepines: tolerance develops within weeks – continue
  • Epilepsy: continue usual medications to avoid seizure risk
  • Mood stabilisers: Lithium, Neurolepts – continue
  • Parkinsons: continue usual medications to avoid ‘freezing’. May be problematic pre- and/ or post-op as dosing often 2-hourly. (Exception DBS surgery: withheld under neurologist instruction)


  • DVT Prophylaxis: see separate protocols
  • Thinners for AF/ cardiac stents/ valves/ stenoses: see separate notes


  • Methotrexate, cyclophosphamide, others: best discontinued on advice of the Rheumatologist (balancing potential interactions, infection and renal problems, with flare-up of condition)

Primary References: and

Articles referred to in the text:

1.Kluger MT, Gale S, Plummer JL, Owen H. Peri-operative drug prescribing pattern and manufacturers’ guidelines. An audit. Anaesthesia. Jun 1991;46(6):456-9. [Medline].

2.Mangano DT, Layug EL, Wallace A, Tateo I. Effect of atenolol on mortality and cardiovascular morbidity after noncardiac surgery. Multicenter Study of Perioperative Ischemia Research Group. N Engl J Med. Dec 5 1996;335(23):1713-20.

3.Selby DG, Richards JD, Marshman JM. ACE inhibitors [letter]. Anaesth Intensive Care. feb/1989;17:110-1. [Full Text].

4.Miller ED, Ackerly JA, Peach MJ. Blood pressure support during general anesthesia in renin-dependent state in the rat. Anesthesiology. 1978;48:404-8.

5.Kataja JH, Kaukinen S, Viinamäki OV, Metsä-Ketelä TJ, Vapaatalo H. Hemodynamic and hormonal changes in patients pretreated with captopril for surgery of the abdominal aorta. J Cardiothorac Anesth. Aug 1989;3(4):425-32. [Medline].

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Posted in Blog by Douglas Fahlbusch