I. INTRODUCTION

A postanesthesia care unit (PACU) is a specialized intensive care ward that serves the brief, yet intense medical needs of patients after a surgical procedure. Such requirements arise from the dual physiologic insult of surgery and anesthesia on the human body. There are occasional needs to deliver emergent cardiovascular and respiratory support postoperatively to patients, and PACUs are equipped to provide the same level of intensive care that a surgical intensive care unit is capable of. Further, because of continual traffic between the operating suite and the PACU, the two are usually located near one another within a hospital.

II. HISTORY

As early as 1801, some British hospitals had areas dedicated to the care of patients recovering from operations and also those who were severely ill. Soon after the discovery of the anesthetic properties of ether, which opened the door to a considerable growth in surgery, Florence Nightingale suggested in 1863 that postoperative patients in the U.S. be cared for in a specialized ward. Apparently, however, such units did not become commonplace in the hospitals of the developed world until the first half of the 20th century. These units did not receive “intensive care unit” status until the later decades of the 20th century.

III. VULNERABILITIES OF THE POST-OP PATIENT

The trauma of an operation and the residual effects of anesthetic drugs alter human physiology in predictable ways. Surgery typically begets bleeding and inflammation. Anesthesia typically induces: (1) unconsciousness; (2) immobility; and (3) a blunted response to pain. Emergence from these anesthetic effects is a time of instability, characterized by upper airway obstruction, delirium, pain, nausea/vomiting, hypothermia, and autonomic lability.

In multiple studies over the past few decades, the two most common life-threatening postoperative complications affecting patients have been respiratory insufficiency and cardiovascular instability. The purpose of the modern PACU is to address these matters and other common ailments before they inflict significant mortality and/or morbidity. Further, modern PACU discharge criteria emphasize respiratory and cardiac stability as a prerequisite to PACU discharge (see PACU Discharge Criteria in this chapter).

Several retrospective, single-center studies have examined the prevalence and types of postoperative complications in the recovery room. The first study published in the era of pulse oximetry examined 18,000 anesthetics and found that the three most common post-op complications were: (1) nausea/vomiting (42% of complications); (2) need for upper airway support (29%); and (3) hypotension (13%). Fourteen years later, another study of over a thousand patients found a similar 23% overall rate of post-op complications. However, the distribution of complications differed a bit. The three most common types were: (1) need for upper airway support
(40% of complications); (2) nausea/vomiting (31%); and tachycardia (13%). Most recently, a study of over a thousand patients in Qatar found a much lower overall rate of post-op complications in the PACU (4%). Of these complications, the three most common were: (1) desaturation (40% of complications); (2) hypo- or hyperthermia (25%); and (3) postoperative nausea and vomiting (PONV; 15%). The discrepancies in complication prevalence and distribution can be attributed, at least in part, to marked heterogeneity between the studies related to, among other things: (1) case mix (e.g., rate of ENT and gynecologic surgeries known to be high risk for PONV); (2) provider level of expertise; and (3) data collection (i.e., lack of universal criteria for defining various complications).

The analysis of national adverse event databases is probably more relevant. In 1989, Zeitlin published a review of the recovery room cases found in the American Society of Anesthesiologists (ASA) closed claims database. Such cases represented 7% of the over 1,100 incidents in the database. Most of these occurred in the era before pulse oximeters became widely used. Not surprisingly, respiratory incidents comprised the majority of the cases (49 of the 84), whereas cardiovascular incidents represented a minority (9 of 84). In 2002, Kluger et al published a similar analysis of the Anaesthetic Incident Monitoring Study (AIMS) database in Australia. Of the over 8,000 total cases, 5% occurred in the recovery room. The three most common cases were: (1) respiratory/airway issues (43%); (2) cardiovascular problems (24%); and (3) drug errors (11%).

A. Respiratory

Respiratory insufficiency in the PACU is usually partially secondary to residual anesthetic effects. All of the medications given intraoperatively to enable tolerance of airway manipulation and surgical stimulation can undermine normal respiratory function postoperatively. Opioids and hypnotics depress respiratory drive, airway reflexes, and airway patency. Central nervous system depressants also put patients at risk of laryngospasm. Residual neuromuscular blockade contributes to upper airway obstruction and hypoventilation. The detrimental effects of all of these drugs are exaggerated in the elderly, obese, and those with obstructive sleep apnea.

B. Cardiovascular

Common cardiovascular problems in the PACU include hypotension, hypertension, or tachycardia.

Surgery results in bleeding, nonhematologic volume losses (e.g., evaporative and interstitial), and inflammation. Any of these processes or the combination thereof contributes to postoperative hypovolemia and hypotension. Residual anesthetics such as opioids and hypnotics can also lower arteriolar and venous tone, resulting in decreased preload and afterload.

When postoperative pain control is inadequate, nociceptive signaling from the surgical site can trigger sympathetically mediated tachycardia and hypertension. Although hypotension is more immediately life threatening, tachycardia and hypertension are associated with increased risk of ICU admission and mortality. The mechanism of mortality may be related to the metabolic burden placed on the heart in this transient hyperdynamic state. For instance, it is known that most perioperative myocardial infarctions occur 24 to 48 hours postoperatively and likely arise from supply-demand mismatch rather than plaque rupture events.

IV. PACU STANDARDS AND GUIDELINES

The ASA publishes and regularly updates practice standards that define the minimum expectations of care in the postanesthetic period. The standards are, at times, vague (e.g., standard #1 below) and can certainly be
exceeded at a clinician’s discretion. From the standpoint of these standards, “anesthesia” refers to any combination of general, regional, and monitored anesthesia care. The ASA’s five minimum expectations for postanesthetic care are summarized below (Anesthesiologists Approved by the House of Delegates on Oct 12, 1998 and last ammended on Oct 21, 2009):

A. A patient who receives anesthesia should receive appropriate postanesthesia care.

B. During transport to the PACU, a patient should be accompanied and constantly evaluated and supported by a member of the anesthesia team knowledgeable about the patient’s condition.

C. Upon arrival in the PACU, the anesthesia team member should reevaluate the patient and provide a verbal report to the accepting PACU nurse.

D. The patient should be evaluated continually while in the PACU.

E. A physician should be responsible for discharge of the patient from the PACU.

In contrast to standards, guidelines provide “suggestions” rather than “requirements” for care. The Practice Guidelines for Postanesthetic Care are developed by the ASA Taskforce on Postanesthetic Care. They integrate current scientific literature and the opinion of groups of experts, including, separately, the (1) members of the ASA Taskforce (a group of anesthesiologists and epidemiologists); (2) PACU consultants; and (3) ASA members at large.

The guidelines encourage vigilance in the PACU for the common postoperative complications and appropriate treatment when such complications arise. Specifically, the guidelines recommend regular monitoring for and support of the following:

1. Respiratory function

a. Airway patency, respiratory rate, and oxygen saturation

2. Cardiovascular function

a. Pulse, blood pressure, and/or electrocardiographic monitoring

b. Euvolemia judged by hemodynamics and the balance of fluid intake and output (including the output of urine and surgical drains)

3. Neurologic function

a. Mental status and neuromuscular function

4. Miscellaneous

a. Normothermia, pain control, shivering control, and nausea/vomiting prevention/treatment

V. PACU ADMISSION CRITERIA

In accordance with the ASA Standards, at our institution, any patient who receives a general or regional anesthetic is transported to the PACU. Patients receiving conscious sedation can either be brought to the PACU or delivered to stage 2 recovery (see Phases of Postanesthetic Recovery in this chapter) at the discretion of the anesthesiologist.

A. Phases of Postanesthetic Recovery

Postanesthetic recovery for ambulatory surgery patients is often divided into three phases: early, intermediate, and late.

1. Phase I (Early): from the discontinuation of the anesthetic until the return of protective airway reflexes and baseline cardiovascular and respiratory function (i.e., when patient meets PACU discharge criteria described below). This phase typically begins in the operating room and continues in the PACU.

2. Phase 2 (Intermediate): starts when the patient meets PACU discharge criteria. This phase occurs in a step-down unit or ambulatory surgery unit (ASU) and ends when the patient is ready to be safely discharged home. Notably, all ambulatory surgery patients
discharged home should be accompanied by an adult, per ASA Guidelines.

3. Phase 3 (Late): continues at home until the patient returns to their preoperative psychomotor state. For ambulatory surgery patients, this often takes 1 to 3 days.

For hospitalized inpatients, phases 2 and 3 both occur on an inpatient ward. Because of the speed with which newer anesthetics are eliminated by the body, patients can sometimes bypass phase 1 and proceed straight from the operating room to phase 2, thus liberating PACU personnel and efficiently decreasing resource utilization. This practice is sometimes called “fast-tracking.” Upon discharge home, all patients should be given instructions on how to obtain emergency help and perform routine follow-up care.