The phase of early recovery is of particular interest to anesthesiologists and nurses involved in post-anesthesia care. This phase can be broadly defined as the time required for patients to sufficiently recover from anesthesia enabling discharge from PACU to the surgical ward [2]. The time can be further subdivided to immediate and early. The immediate phase is typically the first 15 min after cessation of anesthesia when emergence occurs and the predominant focus is on safety. The physiological recovery domain predominates including airway, consciousness, hemodynamic stability, temperature, and treatment of pain and nausea. After this, the early phase generally focuses on criteria to define readiness for PACU discharge. However, there is little agreement on which are the optimal criteria [7]. The American Society of Anesthesiologists, for example, recommend that minimal requirements for discharge are defined for each PACU, but do not endorse a specific set of criteria [8].

Making discharge decisions based on post-anesthesia recovery scores is a common practice in PACUs and, of the different scoring systems described in the literature, the Aldrete score is arguably the most popular [9]. This scoring system involves the assessment of five parameters (respiration, oxygen saturation, blood pressure, level of consciousness, and activity) scored at three levels [10]. Patients are considered ready to be discharged to the ward when a score of 9 is achieved (of 10 maximal possible). The time to achieve readiness for PACU discharge based on Aldrete scores is often used as a measure of recovery in studies comparing different anesthetic regimens [11–13]. A common criticism to the Aldrete scoring system is that its measurement properties (e.g., validity, reliability) were not broadly studied [9].

Most of the research evaluating the effectiveness of ERPs focuses on the phase of intermediate recovery, which comprises the period spent in the surgical ward from PACU discharge until readiness for hospital discharge [2]. The focus in this phase is physiological stability, return of organ function and patient mobility, resolution of pain and nausea, and cognitive recovery. Hospital length of stay (LOS) is the outcome most frequently reported in ERP studies [3], essentially presuming that patients leave the hospital as soon as they achieve discharge criteria and are able to manage independently at home. The validity of LOS as a measure of recovery, however, is debatable as length of hospitalization can be influenced by fixed protocols or social circumstances (health care system, hospital culture, surgeon’s preferences, patient’s expectations, and availability of post-discharge support). Research shows that patients often leave the hospital 1–3 days after achieving minimal requirements for discharge [14–16]. For this reason, several authors advocate that, although still relevant as an audit measure for organizational purposes, LOS should not be taken as an index of recovery [2, 3, 15].

Considering the limitations involved in the assessment of LOS, an alternative measure of intermediate recovery may be obtained by assessing the time to achieve standardized hospital discharge criteria (“time to readiness for discharge”) [15]. The main advantage of this measure is that multiple factors related to in-hospital recovery are taken into account (e.g., pain, mobility, gastrointestinal function), without the influence of non-clinical factors that affect LOS. In colorectal surgery, minimal criteria for hospital discharge were suggested by consensus (Table 16.1) [17] and a subsequent study supported the validity and reliability of these criteria when measuring intermediate recovery [15]. Although these discharge criteria may be applicable to other gastrointestinal surgeries, further research is warranted to define procedure specific requirements for hospital discharge. A potential problem with this approach is that some criteria may be subjective rather than objective, leading to performance bias if the treating medical and nursing team has a strong early discharge philosophy.

The focus in the late recovery period changes from acute impact of surgery to the return to normality (i.e., return to preoperative health state or improvement). Although clinicians may consider that patients are “sufficiently” recovered when they are ready for hospital discharge, for patients, recovery is only achieved when they are able to “perform activities as they performed before surgery” [18]. Recovery to preoperative health extends way beyond hospital stay. Elderly patients undergoing major abdominal surgery, for example, may take up to 3 months to recover their ability to self-care and up to 6 months to return to preoperative levels of strength and conditioning [4]. In spite of the relevance of monitoring recovery after hospital discharge, late recovery outcomes are rarely reported in ERP research [3].

As late recovery implies return to normal health, this phase should be measured in relation the patient’s preoperative (baseline) levels of symptoms, functional status and well-being. In the literature, measures of late recovery often take the form of patient-reported outcomes (PROs; reports coming directly from the patient, generally in the form of questionnaires) [3]. The main advantage of using PROs to measure recovery is that they allow a broad assessment of health status across various domains of health (e.g., pain, fatigue, organ function, physical function). PROs are also relatively inexpensive and easy to administer. A potential disadvantage is that changes in PRO scores may be confounded by postoperative cognitive decline [1], recall bias (i.e., inaccurate recollection of events), and response shift (i.e., change in patients’ standards and values in relation to their health status over time) [19]. Multidimensional questionnaires of generic health status (e.g., Short-Form 36 [20]) and recovery-related health status (e.g., Quality of Recovery Score [21] and Postoperative Quality of Life [22]) had their validity supported in the context of late recovery. The validity of questionnaires specifically focused on postoperative fatigue (Identity–Consequence Fatigue Questionnaire) [23] and physical activity (CHAMPS) [24] has also been supported in the literature.