Effective pain control after surgery is a key part of ERAS programs, helping patients recover more comfortably and quickly. However, pain remains a common issue in the post-anesthesia care unit (PACU), with studies reporting that 7.3% to 26.9% of patients experience pain during this period. Notably, about 1.42% of patients suffer from moderate to severe pain, which can negatively impact recovery and patient satisfaction [3] . If not properly managed, acute pain in the PACU can raise the likelihood of patients experiencing long-term or chronic postoperative pain [4] . In the PACU, tools like the Visual Analog Scale (VAS), Numeric Rating Scale (NRS), and the Wong-Baker Facial Pain Scale are often used to evaluate pain, but these methods rely heavily on patient self-report and are subjective. More objective alternatives include measuring the pupillary light reflex latency just before extubation [5] , as well as using the APA5 acute pain scale within 15 minutes post-extubation, which assesses indicators such as facial expressions, body movements, verbal reactions, heart rate, and blood pressure [6] .

Effective postoperative pain control relies on perioperative multimodal analgesia, with individualized pain management strategies playing a critical role in reducing postoperative inflammatory responses, alleviating anxiety, improving sleep quality, and minimizing complications. Although opioids remain the cornerstone of postoperative analgesia, concerns about their adverse effects have accelerated the shift toward opioid-sparing and even opioid-free analgesic regimens, along with the integration of nonpharmacological interventions as complementary approaches.

Central sensitization and peripheral sensitization are two principal mechanisms underlying postoperative pain. Opioids are primarily effective in preventing central sensitization. In contrast, nonsteroidal anti-inflammatory drugs (NSAIDs) and COX-2 selective inhibitors mitigate peripheral sensitization by inhibiting prostaglandin synthesis and reducing local inflammation. Regional anesthesia also contributes by blocking the activation of peripheral C and A-delta fibers. Together, these strategies help prevent peripheral pain amplification.

A recent study demonstrated that the use of regional anesthesia significantly reduces the risk of developing chronic postoperative pain (odds ratio 0.46; 95% confidence interval: 0.28 - 0.78; p = 0.004) [7] . Therefore, evidence-based non-opioid analgesic techniques—such as NSAIDs, epidural analgesia, ultrasound-guided regional nerve blocks, and local anesthetic infiltration—are strongly recommended components of postoperative pain protocols.

In addition, emerging complementary therapies from traditional Chinese medicine have shown promise in enhancing postoperative pain relief. Techniques such as local cold application, cheek acupuncture, and transcutaneous electrical nerve stimulation (TENS) have been identified as effective adjuncts within multimodal analgesia frameworks [8] [9] . Furthermore, preliminary studies suggest that aromatherapy [10] and music therapy [11] may provide additional benefits in optimizing postoperative pain control.

Managing postoperative nausea and vomiting (PONV) is a key component of ERAS protocols. As early as 2016, the American Society for Enhanced Recovery recommended that all surgical patients receive PONV prevention measures during the perioperative period [12] . While the overall incidence of PONV ranges from 20% to 40%, it occurs in about 9.6% of patients in the PACU [13] . Effective prevention not only shortens PACU stay but also helps reduce medical supply costs and eases the burden on healthcare staff [14] . Several factors increase a patient’s risk of developing PONV, including being female, younger in age, a non-smoker, undergoing procedures such as cholecystectomy, laparoscopic, gynecological, or bariatric surgery, having a history of PONV or motion sickness, receiving inhaled anesthetics, and using opioids after surgery. Screening for PONV risk before surgery and creating individualized anesthesia plans and backup strategies for high-risk patients can help reduce the likelihood of PONV in the PACU.

For patients who develop PONV in the PACU, several rescue strategies are available:

1) Preoperative assessment of postoperative nausea and vomiting (PONV) risk is essential. For patients identified as low risk, prophylactic antiemetic therapy is generally not required during surgery. If intervention is deemed necessary, dexamethasone or a 5-hydroxytryptamine (5-HT₃) receptor antagonist is recommended as the first-line agent.

2) In high-risk patients, if prophylaxis with dexamethasone or a 5-HT₃ receptor antagonist has already been administered intraoperatively, and PONV still occurs, a rescue antiemetic with a different mechanism of action should be used. Recommended options include droperidol, diphenhydramine, promethazine, or metoclopramide. In addition, complementary therapies such as acupuncture and acupressure may be employed to enhance antiemetic efficacy [15] .

3) If antiemetics have already been administered intraoperatively and in the PACU, but the patient continues to experience PONV, low-dose propofol or peppermint aromatherapy may be considered. Studies have shown that sub-hypnotic doses of propofol exert a brief antiemetic effect, with a median effective plasma concentration of approximately 0.343 mg/L [16] .

4) If neuromuscular blockade reversal is required, sugammadex is the recommended agent [17] .

Delirium is a sudden-onset mental disturbance marked by shifting levels of awareness and attention, confusion about time and place, memory loss, sensory misperceptions, and disordered thought processes [18] . It typically arises when the brain is unable to cope with physiological stressors or underlying triggers [19] . Research on patients undergoing non-cardiac surgery reported a 38% overall rate of delirium in the PACU, rising to 62% in elderly patients. Older age and cancer were recognized as significant risk factors for developing delirium [20] . Postoperative delirium has been linked to longer hospital stays, impaired functional recovery, cognitive deterioration, an increased risk of long-term dementia, and higher mortality rates. Timely recognition of patients at risk can greatly reduce the occurrence of delirium after surgery. It is estimated that around 40% of postoperative delirium cases are both reversible and preventable in clinical practice [21] .

Strategies to prevent postoperative delirium include:

1) Keeping the PACU environment calm and quiet;

2) Patiently communicating with patients and placing a clock where they can easily see it to help with orientation;

3) Playing recordings of a mother’s voice for children in the PACU [22] ; when feasible, allowing family members to visit early can support bedside care;

4) Encouraging early activity and oral intake while in the PACU;

5) Removing invasive or non-invasive monitoring as soon as respiratory and circulatory stability is ensured;

6) Training PACU nurses to be more aware of delirium, aiding in its early detection and management [23] ;

7) The European Society of Anaesthesiology and Intensive Care Medicine (ESAIC) does not recommend the use of dexmedetomidine or other pharmacologic agents for the prevention of postoperative delirium (POD). However, dexmedetomidine may be used for the treatment of POD, particularly in patients undergoing cardiac surgery [24] . Although dexmedetomidine shows therapeutic potential in managing postoperative delirium, its use requires caution due to associated adverse effects, such as sinus bradycardia and hypotension. In ICU patients requiring mechanical ventilation for more than 24 hours, early intravenous sedation with dexmedetomidine at a dose of 1 µg/kg/h (without a loading dose, and with maintenance titrated based on clinical response) may be associated with an increased 90-day mortality risk in patients aged ≤ 65 years, although the underlying mechanisms remain unclear [25] .

Delayed emergence from general anesthesia is defined as the failure to regain consciousness within 60 minutes after anesthetic discontinuation, during which the patient remains unresponsive to verbal cues or physical stimulation [26] . Thanks to advances in anesthetic drugs, improved monitoring technologies, and the growing emphasis on low-opioid anesthesia, the rate of delayed emergence has significantly declined. Effective prevention hinges on identifying high-risk patients early and taking proactive measures. Common risk factors include advanced age, young age, male sex, obesity, preexisting cognitive impairment, excessive intraoperative opioid use, history of alcohol use, respiratory dysfunction, hypothermia, prolonged anesthesia duration, and excessive fluid administration [27] .

When multiple risk factors are present, anesthesiologists should tailor an optimized anesthetic strategy, employ appropriate monitoring tools, and maintain physiological homeostasis to reduce the risk of delayed recovery. In addition, studies in traditional Chinese medicine suggest that applying transcutaneous electrical stimulation to specific acupoints starting 20 minutes before anesthesia induction and continuing until the end of surgery [28] , or administering higenamine—an extract from Aconitum—via intravenous infusion prior to induction [29] , may help lower the risk of delayed emergence following surgery.

Perioperative hypothermia occurs in 4% to 70% of patients, with rates as high as 20% to 28% in the post-anesthesia care unit (PACU) [38] [39] . This condition is associated with a higher risk of surgical site infections, cardiac ischemic events, coagulation abnormalities, and delayed recovery.

Evidence from a prospective clinical study suggests that preoperative warming for just 15 minutes can significantly improve intraoperative core temperature and reduce the likelihood of unintended hypothermia [40] . In the PACU, active warming techniques—such as forced-air warming systems, fluid warmers, and adjusting room temperature—can be employed to maintain normothermia.

Complementary methods, including moxibustion, herbal plasters, and acupoint transcutaneous electrical stimulation, may also help regulate circulation and energy flow, thereby supporting temperature recovery [41] .

Postoperative thirst is one of the most intense, common, and often overlooked subjective discomforts experienced by patients in the perioperative period [42] . Lee et al. reported that the incidence of postoperative thirst can reach up to 79.6%, with moderate to severe thirst affecting 53.2% to 69.8% of patients [43] . Compared to men, women tend to experience more persistent thirst discomfort over time following fluid restriction [44] . Notably, thirst has been shown to increase pain sensitivity [45] , which may exacerbate anxiety and hinder recovery after surgery.

In PACU patients, postoperative thirst can be relieved by moistening the lips with cotton swabs, setting drinking intervals (e.g., every 15 minutes), and using oropharyngeal moisturizing sprays. Early oral hydration may be initiated as needed once patients are fully awake, stable, and have regained muscle strength and protective reflexes [46] . To reduce risks like reflux and aspiration, total fluid intake during the PACU stay should not exceed 0.5 ml/kg [47] . Small-volume early hydration also helps shorten postoperative ileus and promotes faster gastrointestinal recovery [48] . Therefore, PACU staff should actively address postoperative thirst rather than overlook this discomfort.