The post-anesthesia care unit (PACU) provides close observation during recovery from anesthesia and surgery. Residual anesthetic effects, surgical stress, and postoperative complications disrupt normal physiological function, requiring systematic monitoring to ensure recovery is proceeding smoothly and to identify and treat any side effects. The American Society of Anesthesiologists (ASA) recommends assessing respiratory and cardiovascular function, neuromuscular recovery, mental status, temperature, pain, nausea and vomiting, fluid balance, and surgical bleeding. PACU monitoring should include standardized components for completeness, but clinicians should also pay attention to patient characteristics, anesthetic technique, and surgical complexity [1].
Respiratory monitoring is a primary concern because residual anesthetics, opioids, and neuromuscular blocking agents can compromise natural ventilation and airway protection. Assessment includes airway patency, respiratory rate, breathing pattern, and peripheral oxygen saturation (SpO₂). Pulse oximetry facilitates detection of hypoxemia but does not directly measure ventilation. Supplemental oxygen may maintain satisfactory SpO₂ despite hypoventilation, potentially masking respiratory depression. Capnography provides additional information about ventilation and may be particularly valuable in patients at increased risk of opioid-induced respiratory depression. Clinical assessment remains essential because normal respiratory rates or oxygen saturation values do not necessarily indicate adequate ventilation [1,4].
Cardiovascular monitoring in PACU includes regularly measuring blood pressure and heart rate, with electrocardiographic monitoring available according to clinical requirements. Hypotension may reflect residual anesthetic-induced vasodilation, hypovolemia, or postoperative bleeding, whereas hypertension may accompany pain or agitation. Persistent hemodynamic instability can compromise organ perfusion and contribute to complications such as acute kidney injury. Consequently, cardiovascular measurements should be interpreted alongside fluid balance, blood loss, and baseline physiological status [1,2].
Neurologic and neuromuscular monitoring evaluates recovery of consciousness, responsiveness, and muscle function. Delayed emergence may indicate residual sedative effects or other postoperative abnormalities, while agitation and confusion warrant assessment for potential complications, including delirium. Patients receiving nondepolarizing neuromuscular blocking agents require evaluation for residual weakness, which may impair respiratory mechanics and airway protection despite apparent wakefulness. Objective neuromuscular assessment can supplement clinical examination when appropriate [1,2].
Temperature is also a relevant vital sign in PACU monitoring. Residual hypothermia may cause shivering and discomfort, while elevated temperature can reflect surgical inflammation or occasionally more serious complications. Maintaining normothermia is therefore an important recovery objective [1,2].
Pain and postoperative nausea and vomiting (PONV) require regular assessment because both are common after anesthesia and surgery and influence recovery quality and discharge readiness. Pain intensity and response to analgesia should be evaluated alongside sedation and respiratory status, particularly following opioid administration. PONV can cause significant discomfort, dehydration, and aspiration risk, potentially prolonging PACU observation [1,2].
Fluid balance and surgical site monitoring complement physiological measurements. Assessment of hydration, intravenous fluid administration, operative blood loss, and surgical drainage helps identify hypovolemia or ongoing bleeding. Urine output and voiding should be evaluated selectively according to patient risk and procedural requirements [1,2].
Recovery scoring systems provide structured assessments of discharge readiness to support PACU monitoring and care. The Modified Aldrete Score evaluates activity, respiration, circulation, consciousness, and oxygen saturation. The White Fast-Track Score additionally incorporates pain and emesis, while the SAMPE checklist includes bleeding and motor function [1,3].
Emerging wireless monitors and wearable biosensors may improve detection of physiological deterioration through continuous surveillance. However, measurement accuracy, artifacts, and alarm fatigue remain important limitations [4]. Ultimately, effective PACU monitoring integrates physiological trends, clinical examination, and standardized recovery assessment to support early recognition of complications and safe postoperative transitions.