The administration of anesthesia has long been regarded as a medical intervention without immediate diagnostic or curative benefit. Rather, it has been described as an assistive service allowing surgical procedures to take place. With time, the increasingly complex task of providing anesthesia resulted in the need for specialists, who were often surgeons in the early years of the speciality. Expanding knowledge of human physiology and pharmacology, advances in airway, respiratory and hemodynamic management and the advent of regional anesthesia revolutionized perioperative medicine and transformed the field of anesthesiology. The evolution of surgery progressed in parallel, with innovations in anesthesia allowing for procedures to increase in length, complexity and invasiveness, and to be extended to increasingly morbidity-ridden patient populations. Anesthesiologists’ responsibilities quickly expanded to include the maintenance of vital organ functions, and consequently comprehensive medical care of the patient during, before and after surgical procedures, including the care for critically ill. Moreover, preoperative medical evaluation became an important constituent of anesthetic management, as it allowed for the stratification of overall surgical risk. The development of the American Society of Anesthesiologists Classification system to predict perioperative risk is only one of the most visible contributions. Along with these developments, the field of anesthesiology has been shifting from a surgery-enabling service to a comprehensive perioperative science.

Following is a discussion of relevant literature regarding various aspects of anesthetic care and their influence of perioperative outcomes. The concept of anesthesia related perioperative outcomes research is introduced, followed by examples in various clinical settings. A special focus on orthopedic surgical patients is presented, as the majority of available evidence concerns itself with this particular population.

As much of our knowledge in the field of anesthesiology’s impact on outcomes is derived from large population-based dataset research, it is necessary to understand basic concepts related to this type of analyses. Many end points of interest occur rather infrequently, thus necessitating large patient samples to conduct valid analyses and derive meaningful conclusions [1]. Methodological advances have allowed for the use of extremely large datasets encompassing information from vast numbers of patients, hospitals and regions, representing “real world practice”, thus allowing researchers to overcome the constraints of single-institutional studies usually performed in academic settings. The latter have been criticized in the past, partially because of the limited external validity of the data generated by these studies. Further, randomized controlled trials conducted in such settings are often constrained by unrealistic inclusion and exclusion criteria.

Although associated with many advantages, the analysis of large database constructs has a number of limitations. It must be noted that commonly used databases for clinical research have not been designed for such purposes and lack pertinent clinical detail. In this context, sampling of data with the correct scope, sufficient granularity and integrity requires thoughtful planning, rigorous execution, coordination and time. Frequently, many data contributing centers deliver data of variable quality, thus making analysis and interpretation challenging. In addition, statistical analysis of such datasets – often exceeding millions of discharge entries – is disproportionately more complex than traditional statistical data handling, as computational technology, knowledge and advanced methodology is necessary. Finally, while associations can be established between interventions and outcomes, clear causalities cannot. This is in part due to the issue of residual cofounding, as many data points were collected for administrative purposes and lack important clinical covariates. Readers need to evaluate results of such studies accordingly, realizing their value and their limitations [2].

The choice of anesthetic technique and its impact on outcomes has been on the forefront of anesthesia related outcome research in recent years. In this context, studies evaluating the use of general versus regional anesthesia have shown how the choice of anesthetic approach can impact on numerous perioperative outcomes measures. General anesthesia is defined by a state similar to deep unconsciousness, frequently necessitating securing of the airway and mechanical ventilation due to loss of protective reflexes and respiratory drive. Regional anesthesia comprises blockade of nerve conduction utilizing local anesthetics, either centrally at the level of the spinal cord or at more peripheral locations, at the level of nerve bundles or singular nerves. Advantages of regional anesthesia include the preservation of higher central nervous system functions such as those affecting the respiratory system, while negating the need for invasive procedures including intubation and ventilation. Not all types of surgery lend themselves equally well to regional anesthetic approaches. It has become widely utilized particularly in procedures involving the extremities and lower part of the trunk, either as the sole anesthetic or in combination with sedation or general anesthesia. Basic and clinical science have suggested numerous benefits of regional anesthesia: better and longer-lasting analgesia with less need for systemically administered analgesics, higher patient comfort with lower incidence of postoperative nausea and vomiting, and improved distal tissue perfusion through sympatholysis. The following is a discussion of the literature as it pertains to the choice of anesthetic technique and perioperative outcomes for a number of different procedures. As much of the literature focuses on orthopedic patients, data regarding this population is featured more prominently below.

Orthopedic surgery is a prime target for comparative outcomes research, as it concerns a large and increasing collective of patients, many of whom are advanced in age and suffer from a number of comorbidities.