In general, the practice of anesthesiology and implementation of anesthetics have changed significantly since the days of the copper kettle and drop ether. Notable milestones in the 20th century included halogenated volatile anesthetics, intravenous induction drugs, carbon dioxide absorbents, continuous capnography, and pulse oximetry, as well as the evolution and expansion of regional anesthetic practices. Anesthesiologists have enabled surgeons and acute care specialists to perform ever-more complex surgical procedures while maintaining comfort, compassion, and dignity.

The serendipitous timing of the rise in surgical and nonsurgical procedures, coupled with the space age information arms race, heralded a rapid expansion of technology, computerization, and governmental funding, fueling substantial advancements in academic medicine and the biological sciences (Anesthesiology 2021;135:963-74). The rapid increase in medical knowledge and evolution of surgical practices enabled more significant volumes of those with extreme age, general dysfunction, and morbidity to undergo complex surgical procedures. In conjunction with this expansion of both surgical and anesthetic expertise, the 1980s also saw the formation of the Anesthesia Patient Safety Foundation, the ASA committees on Standards of Care and Patient Safety and Risk Management, and the society’s Closed Claims Project (Anesthesiology 2021;135:963-74). As such, death rates related to anesthesia decreased by 97% compared to the late 1940s, and adverse events from anesthetics now occur in approximately 0.82 in 100,000 inpatient surgical patients (Anesthesiology 2009;110:759-65). While the practice of anesthesiology is considered safe, the risks associated with complex surgery in a critically ill, obese, and frail patient population continue to drive progress to decrease perioperative morbidity and mortality.

By 2030, one in five Americans is projected to be 65 or older, owing to the aging baby boomer and Generation X demographic. From 2011 to 2017, Gill et al. evaluated 1,193 major surgeries for adults aged 65 years or older in the continental United States, finding that the presence of frailty or dementia among elderly patients was associated with significantly elevated one-year mortality risk: one-year mortality among non-frail patients was 6.0% (95% CI, 2.6%-9.4%) versus 27.8% (95% CI, 21.2%-34.3%) for frail patients, and one-year mortality among patients without dementia was 11.6% (95% CI, 8.8%-14.4%) versus 32.7% (95% CI, 24.3%-41.0%) for patients with dementia (JAMA Surg 2022;157:e225155).

In addition to age, frailty, and dementia, major adverse cardiac events (MACE) are some of the most common complications occurring in the perioperative period. Patients with significant cardiac disease undergoing vascular or major surgery may have up to a 10% risk of morbidity and mortality (Mo Med 2016;113:320-4). When evaluating the 2014 American College of Cardiology/American Heart Association guidelines on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery, it was found that the 30-day postoperative mortality rate was significantly higher in patients with nonischemic heart failure (HF) (9.3%), ischemic HF (9.2%), and atrial fibrillation (AF) (6.4%) than in those with coronary artery disease (CAD) (2.9%). HF alone increases perioperative mortality three- to fivefold, and when further differentiated into compensated versus decompensated, the numbers are staggering, with 5%-7% versus 20%-30% risk of mortality (Circulation 2014;130:2215-45).

Postoperative pulmonary complications (PPC) encompass a wide variety of pathologies, including atelectasis, pleural effusion, pneumonia, aspiration pneumonitis, respiratory failure, and acute respiratory distress syndrome, which also have a significant effect on postoperative morbidity and mortality. The vast heterogeneity in PPC makes a precise definition challenging. As a result, the reported incidence of PPC is unclear, ranging from 2%-40% (Perioperative Medicine Managing for Outcome. 2nd ed, 2021). However, when a patient does develop a PPC, 30-day perioperative mortality is significantly increased. Pulmonary management is particularly relevant when caring for obese patients. Among adults in the U.S., the prevalence of obesity (BMI>30) and severe obesity (BMI >40) was approximately 42.4% and 9.2%, respectively. Silber et al. evaluated 2,045 severely or morbidly obese patients between 65 and 80 years old, finding that compared to nonobese patients, obese patients were at increased risk for wound infection, renal dysfunction, respiratory events, 30-day readmission, and longer length of stay (Ann Surg 2012;256:79-86).

In addition to patient-related factors, perioperative mortality depends on surgery-related factors, most notably surgical site (intracranial, intrathoracic, intraperitoneal, and suprainguinal vascular) and the urgency of surgical intervention. For example, the mortality rate for patients in the Society of Thoracic Surgeons database is approximately 2.3% for CABG, 3.4% for isolated valve procedures, and 6.8% for valve procedures combined with CABG (Hensley’s Practical Approach to Cardiothoracic Anesthesia. 6th ed, 2019). Additionally, urgent and emergency surgeries are associated with significantly higher mortality risk compared to elective surgery: after controlling preoperative risk factors, patients undergoing urgent surgery demonstrated increased 30-day mortality with an odds ratio of 2.32 (95% CI, 2.00-2.68), while emergency surgery patients demonstrated 30-day mortality with an OR of 2.91 (95% CI, 2.48-3.41) compared to elective surgery (JAMA Surg 2017;152:768-74). Reducing the burden of emergency surgery via improved access to care and health literacy will likely result in significant health care cost reductions and positive clinical outcomes (Ann Surg 2015;262:260-6).

With this information in mind, risk stratification tools have become more available to the anesthesia care team to differentiate patients at increased risk of complications, which may benefit from further optimization or alteration in surgical planning or timing. Tools such as the Revised Cardiac Risk Index and various NSQIP Surgical Risk Calculators from the American College of Surgeons have all grown in popularity. The former is a simple and well-validated tool using six predictors of risk. The latter is a web-based, easily accessible preoperative tool that considers the type of surgery (ICD-10 code), the patient’s functional status (best level of self-care demonstrated by the patient within 30 days before surgery), the ASA Physical Status Classification, and the presence or absence of sepsis. Derivations of this algorithm, such as the Respiratory Failure Risk Tool and the Pneumonia Risk Tool, also consider whether there is an emergency, the patient’s age, smoking status, and if the patient has chronic obstructive pulmonary disease.

Beyond differentiating patients at increased risk of complications, evidence-based enhanced recovery after surgery (ERAS) programs identify essential clinical practices (antibiotics, multimodal pain, fluid management, temperature management) that are associated with favorable clinical outcomes (Ann Surg 2023;277:101-8). Some of these practices (antibiotics) are now the standard of care and included within government quality initiatives linked to reimbursements. Other practices – such as fluid management – have more nuances and are challenging to implement. Additionally, not every patient coming for elective surgery is appropriate for ERAS. As risk stratification tools identify low-risk versus high-risk patients, postoperative courses will vary.

The 21st century has witnessed significant changes in the practice of anesthesiology. However, present-day anesthesiologists face unique challenges in caring for surgical patients, including new procedural areas. The field’s dedication to patient safety offers opportunities to address these challenges. Innovation and research will advance perioperative management. Despite new technology, a vigilant anesthesiologist will remain essential to delivering safe, effective perioperative patient care.