01Core principlesThe concepts and mechanisms needed to understand the subject.
The post-anaesthesia care unit is an active treatment area, not a waiting room. Anaesthetic drug effects, airway instrumentation, surgical blood loss, pain and physiological stress overlap during emergence. Problems evolve quickly, so trained staff, monitoring, equipment and immediate access to an anaesthetist are fundamental. The anaesthetist retains responsibility until an agreed handover and discharge process transfers care.
Handover should link what happened to what could happen next. Relevant information includes pre-existing disease, allergies, airway assessment and difficulty, procedure and position, regional or general technique, neuromuscular blocker and reversal, opioids and other sedatives, vascular access, fluids, blood loss, urine output, temperature, antimicrobial prophylaxis and any intra-operative instability. The receiving practitioner should understand the expected course and precise escalation plan.
Airway and ventilatory complications are common priorities. Residual anaesthesia, opioids, obstruction, laryngospasm and incomplete neuromuscular recovery can coexist. Supplemental oxygen can preserve saturation despite poor ventilation, making clinical assessment and waveform capnography especially valuable. Quantitative neuromuscular monitoring supports diagnosis when weakness is suspected but does not replace airway support.
Discharge is a clinical decision supported by written local criteria. A score can standardise assessment but cannot override a concerning trajectory or a destination unable to meet the patient’s needs. Transfer also needs appropriate escort, oxygen, monitoring, equipment and a receiving team prepared for ongoing risks such as opioid toxicity, bleeding or recurrence of airway obstruction.
Key points
- Keep one-to-one trained recovery care until the patient controls the airway, has stable respiration and circulation, and can communicate appropriately; instability requires direct anaesthetic review.
- Continue ECG, pulse oximetry, blood pressure and waveform capnography after general anaesthesia as indicated; capnography continues while an artificial airway remains and until verbal responsiveness is re-established.
- Do not discharge to a routine ward until consciousness, airway reflexes, breathing, oxygenation and circulation are satisfactory and pain, nausea, vomiting and temperature are acceptably controlled.
- Receive a structured verbal and written handover covering airway difficulty, anaesthetic technique, analgesia, antiemetics, fluids, blood loss, antimicrobials, complications and the postoperative plan.
- Record trends rather than isolated values: conscious level, airway, respiratory rate and adequacy, oxygen and saturation, pulse and rhythm, blood pressure, pain, nausea, temperature and administered treatments.
- Children, obstetric patients, critical illness and patients needing level 2 or 3 care require specialist recovery, staffing and destination criteria beyond this routine adult pathway.
02Mechanisms and patternsImportant relationships and how to distinguish them.
Snoring, tracheal tug, paradoxical movement or poor air entry may improve with repositioning and airway manoeuvres; stridor or silent obstruction is more urgent.
Reduced respiratory effort, shallow breaths, rising carbon dioxide and drowsiness can precede desaturation, particularly when oxygen is being administered.
Poor cough, weak grip, difficulty swallowing or incomplete quantitative neuromuscular recovery increases aspiration and respiratory risk.
Hypotension with tachycardia, pallor, cool skin, reduced urine output or increasing blood loss suggests hypovolaemia or haemorrhage until assessed.
Consider residual anaesthetic or opioid effect, hypothermia, glucose or electrolyte disturbance, hypercapnia, hypoxaemia and neurological events.
Agitation can reflect pain, hypoxaemia, hypercapnia, urinary retention, drug effect or delirium; physical restraint alone misses reversible causes.
03Interpreting evidenceInformation, measurements and their limitations.
Consider the information, its meaning and its limitations before deciding what follows.
- 01
Continuous waveform capnography - Why
- Confirm ventilation and detect obstruction, apnoea or circuit disconnection while an artificial airway remains or verbal response is absent.
- Interpretation and limitations
- Loss or change of waveform requires immediate patient and equipment assessment; supplemental oxygen can delay an oximetry warning.
- 02
Quantitative train-of-four assessment - Why
- Evaluate suspected residual neuromuscular blockade after a non-depolarising blocker.
- Interpretation and limitations
- A ratio below the accepted recovery threshold supports residual weakness; airway protection and ventilation remain the immediate clinical priorities.
- 03
Arterial or venous blood gas - Why
- Define ventilation, oxygenation, acid-base state, haemoglobin, glucose and selected electrolytes in unexplained deterioration.
- Interpretation and limitations
- Use the result with the clinical picture: hypercapnia may explain drowsiness, while a falling haemoglobin can support but cannot alone exclude acute bleeding.
- 04
Core temperature - Why
- Identify perioperative hypothermia or unexpected fever that can delay recovery and increase complications.
- Interpretation and limitations
- Active warming and investigation depend on severity, trajectory and context; shivering also raises oxygen demand.
- 05
Anaesthetic and fluid record - Why
- Reconstruct drug timing, airway events, blood loss, fluid balance, reversal and complications.
- Interpretation and limitations
- The record narrows causes of delayed emergence or instability and shows which effects may outlast recovery observation.
04Applied reasoningWorked examples connecting principles to decisions.
01Worked case: obstructed recoveryDrowsiness with recurrent airway obstructionAn adult in PACU snores, has paradoxical chest movement and becomes less responsive after opioid analgesia.+
- 1Call for help, open the airway with positioning and jaw support, give oxygen and assess airflow, respiratory effort, waveform capnography, saturation and circulation.
- 2Use an airway adjunct and assisted ventilation if required; verify effectiveness from chest movement, capnography, airway pressure and leak rather than assuming a selected mode delivers an adequate breath.
- 3Review anaesthetic and opioid exposure, residual neuromuscular block, temperature and metabolic causes; titrate reversal only when the relevant cause is identified and continue airway support.
- 4Keep the patient in an appropriately staffed monitored area after improvement because obstruction or drug effect may recur, and revise the ward analgesia and observation plan. Continue ECG, pulse oximetry, blood-pressure measurement and waveform capnography through recovery until the artificial airway has been removed and the patient responds verbally.
02PACU deteriorationHypotension after abdominal surgeryBlood pressure falls with tachycardia and increasing abdominal drain output.+
- 1Call the anaesthetist and surgical team, give oxygen, reassess airway and breathing, obtain large-bore intravenous access and repeat observations frequently.
- 2Look for external and concealed blood loss, review intra-operative events and fluids, send urgent blood tests and crossmatch, and activate major haemorrhage support when indicated.
- 3Give balanced resuscitation guided by response while arranging definitive haemostasis; do not discharge or transfer to an inadequately monitored destination.
03Transfer decisionDischarge from PACUThe patient appears awake after an uncomplicated general anaesthetic.+
- 1Confirm clear airway and protective reflexes, satisfactory ventilation and oxygenation, stable cardiovascular observations and an appropriate conscious state.
- 2Ensure pain, nausea, vomiting and temperature are acceptably controlled, surgical concerns are addressed and prescribed observations and oxygen can be delivered at the destination.
- 3Document the discharge criteria, hand over remaining risks and treatments, and provide the monitoring, escort and equipment required during transfer.
05Relevant medicines and safetySpecific regimens and precautions where medicines are relevant.
Titrated naloxone
Use small intravenous increments according to the local emergency protocol when opioid effect causes inadequate ventilation.Many opioids outlast naloxone; abrupt reversal can provoke severe pain and sympathetic stress, so observe for recurrence.
Neuromuscular-block reversal
Select and dose reversal according to the blocker, elapsed time and quantitative train-of-four findings.Reversal does not treat obstruction from other causes, and clinical recovery should be confirmed before airway support is withdrawn.
Supplemental oxygen
Titrate delivery to the patient’s target saturation while assessing ventilation separately.A normal saturation on oxygen does not prove adequate ventilation; assess respiratory effort and carbon dioxide waveform where indicated.
06Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.
- Observe airway patency, respiratory effort and conscious level continuously during early recovery, with immediate capability to provide airway manoeuvres and ventilation.
- Use pulse oximetry, ECG and repeated or continuous blood pressure monitoring according to the anaesthetic and clinical risk; continue capnography while an artificial airway remains and until verbal response returns.
- Measure and trend pain, nausea and vomiting, temperature, wound and drain loss, fluid administration and urine output where relevant.
- Maintain one-to-one care until the patient can maintain the airway and has stable cardiorespiratory observations and appropriate communication.
- Match transfer monitoring and escort to current risk, including oxygen, capnography or higher-acuity care when physiological support remains necessary.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Oxygenation differs from ventilation
Pulse oximetry can remain reassuring during carbon dioxide retention, so airway movement and capnography matter when responsiveness is impaired.
Handover predicts deterioration
Knowing that reversal was incomplete or blood loss accelerated changes the significance of weak breathing or hypotension.
Scores support judgement
A discharge score cannot make an unstable trend safe or create monitoring capability at the destination.
Transport remains anaesthesia care
Monitoring and skilled escort continue through transfer because disconnection, obstruction and haemodynamic change can occur en route.
Population boundaries matter
Paediatric, obstetric and critical-care recovery use different staffing, physiology and escalation arrangements and need their own protocols.
08Common pitfallsFrequent interpretation and management errors.
- 01
Calling an oxygen saturation normal without examining respiratory effort or carbon dioxide in a drowsy patient.
- 02
Removing airway support because a ventilator setting is selected without confirming effective movement and capnography.
- 03
Treating agitation only with sedation before checking pain, oxygenation, ventilation, bladder and metabolic causes.
- 04
Using a numerical discharge score to override continuing hypotension, airway obstruction or an unsuitable ward destination.
- 05
Sending a patient before a structured handover communicates airway difficulty, drug exposure, blood loss and ongoing risks.
- 06
Assuming delayed emergence is benign without checking reversible and neurological causes.