Anesthesiology
Canadian Anesthesiologists’ Society
Last updated: September 2025
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Conducting baseline laboratory investigations before low-risk non-cardiac surgery contributes little value to perioperative care. A focused clinical history and physical examination may reliably identify relevant abnormalities sought by routine laboratory testing before low-risk surgery. In addition, evidence suggests that abnormal results in this setting only rarely influence management and do not improve clinical outcomes. Preoperative testing may add value in the setting of a symptomatic patient or higher-risk surgery, but should not be performed routinely before low-risk surgery on asymptomatic patients.
Sources:
Committee on Standards and Practice Parameters, et al. Practice advisory for preanesthesia evaluation: an updated report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Anesthesiology. Mar 2012;116(3):522-38. PMID: 22273990.
Czoski-Murray C, et al. What is the value of routinely testing full blood count, electrolytes and urea, and pulmonary function tests before elective surgery in patients with no apparent clinical indication and in subgroups of patients with common comorbidities: a systematic review of the clinical and cost-effective literature. Health Technol Assess. Dec 2012;16(50):i-xvi, 1-159. PMID: 23302507.
Keay L, et al. Routine preoperative medical testing for cataract surgery. Cochrane Database Syst Rev. Mar 2012 14;3:CD007293. PMID: 22419323.
Merchant R, et al. Guidelines to the practice of anesthesia–revised edition 2015. Can J Anaesth. Jan 2015 ;62(1):54-67. PMID: 25323121.
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Electrocardiograms (ECGs) performed before elective, non-cardiac, surgeries are frequently abnormal. This is especially true when this test is done in older patients. Despite the frequency of these abnormalities, ECGs do little to improve risk prediction beyond simply asking patients about their health. Serious cardiac events like heart attack are rare following low-risk surgeries; there is little that physicians can do to further lower this risk. A preoperative ECG will therefore not improve outcome but may lead to more testing or treatment that is of little benefit. ECGs used to identify the cause of symptoms (palpitations, chest pain, dyspnea, etc.) remain useful diagnostic tools regardless of whether the patient is having surgery.
Sources:
Liu LL, et al. Preoperative electrocardiogram abnormalities do not predict postoperative cardiac complications in geriatric surgical patients. J Am Geriatr Soc. Jul 2002 ;50(7):1186-91. PMID: 12133011.
Mathis MR, et al. Patient selection for day case-eligible surgery: identifying those at high risk for major complications. Anesthesiology. Dec 2013;119(6):1310-21. PMID: 24108100.
van Klei WA, et al. The value of routine preoperative electrocardiography in predicting myocardial infarction after noncardiac surgery. Ann Surg. Aug 2007;246(2):165-70. PMID: 17667491.
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While chest X-rays (CXRs) remain an important part of surgeon’s evaluation before cancer or thoracic surgeries, it is better if these staging examinations are complete before committing a patient to surgery. CXRs are not indicated in the routine pre–anesthetic assessment. In the absence of symptoms, CXRs yield few diagnoses and many false positives. CXRs do not improve risk prediction or stratification. CXR in the pre-anesthetic evaluation should be reserved for patients with symptoms consistent with acute cardiopulmonary illness (dyspnea, wheeze, productive sputum, etc.).
Sources:
Committee on Standards and Practice Parameters, et al. Practice advisory for preanesthesia evaluation: an updated report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Anesthesiology. Mar 2012;116(3):522-38. PMID: 22273990.
Joo HS, et al. The value of screening preoperative chest x-rays: a systematic review. Can J Anaesth. Jun-Jul 2005;52(6):568-74. PMID: 15983140.
McAlister FA, et al. Incidence of and risk factors for pulmonary complications after nonthoracic surgery. Am J Respir Crit Care Med. Mar 1 2005;171(5):514-7. PMID: 15563632.
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Resting echocardiography has a clear role for resolving diagnostic questions in surgical patients, such as identifying the basis for suspicious systolic murmurs or new dyspnea on exertion. Outside these indications, resting echocardiography does not contribute significant additional prognostic information to usual clinical evaluation. It is not useful as a screening tool to identify surgical patients at risk for cardiac complications.
Sources:
Fleisher LA, et al. 2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. Dec 9 2014;130(24):e278-333. PMID: 25085961.
Halm EA, et al. Echocardiography for assessing cardiac risk in patients having noncardiac surgery. Ann Intern Med. Sep 15 1996;125(6):433-41. PMID: 8779454.
Kristensen SD, 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 (ESA). Eur Heart J. Sep 14 2014 ;35(35):2383-431. PMID: 25086026.
Wijeysundera DN, et al. Association of echocardiography before major elective non-cardiac surgery with postoperative survival and length of hospital stay: population based cohort study. BMJ. Jun 30 2011;342:d3695. PMID: 21724560.
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Stress testing can help resolve diagnostic uncertainty in surgical patients, such as determining whether individuals with chest discomfort and vascular risk factors have undiagnosed coronary artery disease. It can also help identify patients at elevated risk for cardiac complications after major vascular surgery. Nonetheless, asymptomatic individuals with good functional capacity have a very low risk of cardiac complications after low-to-intermediate non-cardiac surgery. Stress testing in such individuals is not useful for delineating expected perioperative risk and guiding clinical care.
Sources:
Etchells E, et al. Semiquantitative dipyridamole myocardial stress perfusion imaging for cardiac risk assessment before noncardiac vascular surgery: a meta-analysis. J Vasc Surg. Sept 2002;36(3):534-40. PMID: 12218978.
Fleisher LA, et al. 2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. Dec 9 2014;130(24):e278-333. PMID: 25085961.
Kristensen SD, 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 (ESA). Eur Heart J. Sept 14 2014 ;35(35):2383-431. PMID: 25086026.
Sgura FA, et al. Supine exercise capacity identifies patients at low risk for perioperative cardiovascular events and predicts long-term survival. Am J Med. Mar 2000;108(4):334-6. PMID: 11014727.
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Anesthetic gases possess significant global warming potential (GWP) and contribute approximately 5% of the harmful greenhouse gas emissions of a typical hospital. However, not all anesthetic gases are equally harmful. The anesthetic gas desflurane has the highest GWP at twenty times more than that of sevoflurane. In addition, when both are delivered at equal fresh gas flows, desflurane has approximately 50 times the impact of sevoflurane due to its lower potency. Patient care can be provided safely and efficiently without desflurane; anesthetic alternatives such as sevoflurane, intravenous anesthesia or regional techniques should be considered, depending on clinical and geographical context. The restriction of the use of desflurane is supported by the Canadian Anesthesia Society, American Society of Anesthesiologists and World Federation of Societies of Anaesthesiologists.
The elimination of desflurane is an effective change that aligns with the Choosing Wisely environmental practice recommendations.
Sources:
Bansal T, et al. A comparative study of desflurane versus sevoflurane in obese patients: Effect on recovery profile. Anaesthesiolo Clin Pharmacol. Oct-Dec 2020; 36(4):541-545. PMID: 33840938.
Campbell M, et al. Atmospheric science, anaesthesia, and the environment BJA Education, Aug 15 2015;(4):173–179.
Eckelman MJ, et al. Life cycle environmental emissions and health damages from the Canadian healthcare system: An economic-environmental-epidemiological analysis. PLoS Med. Jul 31 2018;15(7):e1002623. PMID: 30063712.
Gadani H, et al. Anesthetic gases and global warming: Potentials, prevention and future of anesthesia. Anesth Essays Res. Jan-Jun 2011;5(1):5-10. PMID: 25885293.
Hanna M, et al. A long way to go: minimizing the carbon footprint form anesthetic gases. Can J Anesth/J Can Anesth 2019;66:838–839. PMID: 30877589.
Özelsel TJ, et al. Re-defining the 3R’s (reduce, refine, and replace) of sustainability to minimize the environmental impact of inhalational anesthetic agents. Can J Anaesth. Mar 2019;66(3):249-254. English. Epub Dec 17 2018. PMID:30560410.
Shelton, C, et al. Desflurane in modern anaesthetic practice: walking on thin ice(caps)? British Journal of Anaesthesia, 2020; 125(6):852e856. PMID: 33039121.
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Nitrous oxide is an important greenhouse gas in the atmosphere and a significant contributor to stratospheric ozone layer depletion. The use of nitrous oxide as a general anesthetic offers no clinical benefit to the patient and has been clearly demonstrated to increase postoperative nausea and vomiting.
In addition, anesthesia care providers should advocate for the decommissioning of centralized nitrous oxide distribution systems. These systems are costly to install and maintain. Central systems leak at many points along the distribution path such as at pipeline fittings, valves, wall outlets and manifolds, greatly increasing nitrous oxide purchasing costs, greenhouse gas emissions and potentially impacting air quality in health care facilities. Canadian hospitals have consistently demonstrated leakage rates of up to 99% PRIOR to the point of care. Centralized nitrous oxide distribution systems are both environmentally and economically inefficient and should be eliminated.
Sources:
Canadian Anesthesiologists’ Society. Position Statement. Greening the OR: CAS Position Statement on Reducing Harmful Emissions, Waste and Costs. [Internet] 2024 Dec [cited 2025 Aug 22].
Canadian Coalition for Green Health Care. Nitrous Oxide Toolkit Central Supply System Deactivation Guideline. [Internet]. 2025 July [cited 2025 Aug 22].
Dobson GR, et al. Guidelines to the Practice of Anesthesia-Revised Edition 2025. Can J 2025 Jan;72(1):15-63. English. Epub 2025 Feb 3. PMID: 39900856.
Leslie K, et al. Risk factors for severe postoperative nausea and vomiting in a randomized trial of nitrous oxide-based vs nitrous oxide-free anaesthesia. Br J Anaesth. 2008 Oct;101(4):498-505. Epub 2008 Aug 5. PMID: 18682411.
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The Canadian Anesthesiologists’ Society (CAS) established its Choosing Wisely Canada (CWC) top 5 recommendations by engaging a small team of expert Canadian anesthesiologists to develop research methodology and carry out a survey to establish the CAS top five recommendations. The survey was based on similar work done by the American Society of Anesthesiologists who identified an evidence-based list of activities to question within anesthesiology as Five Things Physicians and Patients Should Question: American Society of Anesthesiologists. The CAS team defined a short list of twelve tests and procedures in perioperative care and asked members of the CAS to consider each and answer questions about their frequency of use, impact on quality of the care for patients, cost of the investigation, evidence to support the investigation and potential to avoid ordering the investigation. Five recommendations were selected through survey data collection and analysis by the CAS research team in conjunction with a professional survey consultant and expert consensus. The top five were presented at the CAS Annual Meeting in June 2015 and will be published in the Canadian Journal of Anesthesia.
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Choosing Wisely Canada’s climate-conscious recommendations are developed by clinician societies to improve planetary health without compromising patient care. These recommendations highlight everyday practices we can reduce or eliminate to minimize environmental harm. Visit our climate page to explore all the recommendations and learn more.
Sources:
Committee on Standards and Practice Parameters, et al. Practice advisory for preanesthesia evaluation: an updated report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Anesthesiology. Mar 2012;116(3):522-38. PMID: 22273990.
Czoski-Murray C, et al. What is the value of routinely testing full blood count, electrolytes and urea, and pulmonary function tests before elective surgery in patients with no apparent clinical indication and in subgroups of patients with common comorbidities: a systematic review of the clinical and cost-effective literature. Health Technol Assess. Dec 2012;16(50):i-xvi, 1-159. PMID: 23302507.
Keay L, et al. Routine preoperative medical testing for cataract surgery. Cochrane Database Syst Rev. Mar 2012 14;3:CD007293. PMID: 22419323.
Merchant R, et al. Guidelines to the practice of anesthesia–revised edition 2015. Can J Anaesth. Jan 2015 ;62(1):54-67. PMID: 25323121.
Liu LL, et al. Preoperative electrocardiogram abnormalities do not predict postoperative cardiac complications in geriatric surgical patients. J Am Geriatr Soc. Jul 2002 ;50(7):1186-91. PMID: 12133011.
Mathis MR, et al. Patient selection for day case-eligible surgery: identifying those at high risk for major complications. Anesthesiology. Dec 2013;119(6):1310-21. PMID: 24108100.
van Klei WA, et al. The value of routine preoperative electrocardiography in predicting myocardial infarction after noncardiac surgery. Ann Surg. Aug 2007;246(2):165-70. PMID: 17667491.
Committee on Standards and Practice Parameters, et al. Practice advisory for preanesthesia evaluation: an updated report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Anesthesiology. Mar 2012;116(3):522-38. PMID: 22273990.
Joo HS, et al. The value of screening preoperative chest x-rays: a systematic review. Can J Anaesth. Jun-Jul 2005;52(6):568-74. PMID: 15983140.
McAlister FA, et al. Incidence of and risk factors for pulmonary complications after nonthoracic surgery. Am J Respir Crit Care Med. Mar 1 2005;171(5):514-7. PMID: 15563632.
Fleisher LA, et al. 2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. Dec 9 2014;130(24):e278-333. PMID: 25085961.
Halm EA, et al. Echocardiography for assessing cardiac risk in patients having noncardiac surgery. Ann Intern Med. Sep 15 1996;125(6):433-41. PMID: 8779454.
Kristensen SD, 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 (ESA). Eur Heart J. Sep 14 2014 ;35(35):2383-431. PMID: 25086026.
Wijeysundera DN, et al. Association of echocardiography before major elective non-cardiac surgery with postoperative survival and length of hospital stay: population based cohort study. BMJ. Jun 30 2011;342:d3695. PMID: 21724560.
Etchells E, et al. Semiquantitative dipyridamole myocardial stress perfusion imaging for cardiac risk assessment before noncardiac vascular surgery: a meta-analysis. J Vasc Surg. Sept 2002;36(3):534-40. PMID: 12218978.
Fleisher LA, et al. 2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation. Dec 9 2014;130(24):e278-333. PMID: 25085961.
Kristensen SD, 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 (ESA). Eur Heart J. Sept 14 2014 ;35(35):2383-431. PMID: 25086026.
Sgura FA, et al. Supine exercise capacity identifies patients at low risk for perioperative cardiovascular events and predicts long-term survival. Am J Med. Mar 2000;108(4):334-6. PMID: 11014727.
Bansal T, et al. A comparative study of desflurane versus sevoflurane in obese patients: Effect on recovery profile. Anaesthesiolo Clin Pharmacol. Oct-Dec 2020; 36(4):541-545. PMID: 33840938.
Campbell M, et al. Atmospheric science, anaesthesia, and the environment BJA Education, Aug 15 2015;(4):173–179.
Eckelman MJ, et al. Life cycle environmental emissions and health damages from the Canadian healthcare system: An economic-environmental-epidemiological analysis. PLoS Med. Jul 31 2018;15(7):e1002623. PMID: 30063712.
Gadani H, et al. Anesthetic gases and global warming: Potentials, prevention and future of anesthesia. Anesth Essays Res. Jan-Jun 2011;5(1):5-10. PMID: 25885293.
Hanna M, et al. A long way to go: minimizing the carbon footprint form anesthetic gases. Can J Anesth/J Can Anesth 2019;66:838–839. PMID: 30877589.
Özelsel TJ, et al. Re-defining the 3R’s (reduce, refine, and replace) of sustainability to minimize the environmental impact of inhalational anesthetic agents. Can J Anaesth. Mar 2019;66(3):249-254. English. Epub Dec 17 2018. PMID:30560410.
Shelton, C, et al. Desflurane in modern anaesthetic practice: walking on thin ice(caps)? British Journal of Anaesthesia, 2020; 125(6):852e856. PMID: 33039121.
Canadian Anesthesiologists’ Society. Position Statement. Greening the OR: CAS Position Statement on Reducing Harmful Emissions, Waste and Costs. [Internet] 2024 Dec [cited 2025 Aug 22].
Canadian Coalition for Green Health Care. Nitrous Oxide Toolkit Central Supply System Deactivation Guideline. [Internet]. 2025 July [cited 2025 Aug 22].
Dobson GR, et al. Guidelines to the Practice of Anesthesia-Revised Edition 2025. Can J 2025 Jan;72(1):15-63. English. Epub 2025 Feb 3. PMID: 39900856.
Leslie K, et al. Risk factors for severe postoperative nausea and vomiting in a randomized trial of nitrous oxide-based vs nitrous oxide-free anaesthesia. Br J Anaesth. 2008 Oct;101(4):498-505. Epub 2008 Aug 5. PMID: 18682411.
About Choosing Wisely Canada
Choosing Wisely Canada is the national voice for reducing unnecessary tests and treatments in health care. One of its important functions is to help clinicians and patients engage in conversations that lead to smart and effective care choices.
Web: choosingwiselycanada.org
Email: info@choosingwiselycanada.org
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Chest X-rays Before Surgery
When you need them and when you don’t.
Common Tests, Treatments, and Procedures You May Think You Need
Let’s think again.
ECG (Electrocardiogram)
When you need it and when you don’t.
Echocardiogram Before Surgery
When you need one and when you don’t.
Heart Tests Before Surgery
When you need an imaging test and when you don’t.
Lab Tests Before Surgery
When you need them and when you don’t.