What is the management of post-operative desaturation (decreased oxygen saturation)?

Management of Post-Operative Desaturation

Immediately verify pulse oximeter accuracy and oxygen delivery system function, then escalate oxygen therapy to achieve target SpO2 of 94-98% (or 88-92% if COPD/hypercapnia risk) while urgently assessing for life-threatening causes. 1, 2

Immediate Technical Verification

Before assuming true hypoxemia, confirm:

• Pulse oximeter is correctly placed with adequate waveform 1
• Oxygen delivery device and flow rate match prescribed therapy 1
• Oxygen cylinder contains oxygen and is not empty 1
• Tubing is connected to oxygen wall outlet, not compressed air 1

Oxygen Therapy Escalation

For Patients WITHOUT Risk of Hypercapnic Respiratory Failure

Target SpO2: 94-98% 1, 2

• If SpO2 <85%: Start reservoir mask at 15 L/min immediately, then titrate down once stabilized 1
• If SpO2 85-93%: Use nasal cannula at 2-6 L/min or simple face mask at 5-10 L/min 1

For Patients WITH Risk of Hypercapnic Respiratory Failure (COPD, obesity hypoventilation)

Target SpO2: 88-92% 1, 2

• Start with 24% Venturi mask at 2-3 L/min or 28% Venturi mask at 4 L/min 1
• Alternative: Nasal cannula at 1-2 L/min 1

Critical Clinical Assessment

Perform urgent evaluation of:

• Respiratory rate (tachypnea >30 breaths/min requires immediate escalation even if SpO2 adequate) 1
• Heart rate (tachycardia with breathlessness indicates potential cardiopulmonary emergency) 1
• Blood pressure (systolic <90 mmHg indicates critical illness) 1
• Mental status (confusion/agitation may indicate hypoxemia or hypercapnia) 1
• Calculate NEWS or equivalent physiological track-and-trigger score 1

Arterial Blood Gas Analysis

Obtain ABG within 60 minutes if: 1

• Patient is critically ill
• Unexpected or inappropriate fall in SpO2 below 94%
• Risk factors for hypercapnia present
• Considering non-invasive ventilation

Use arterial sample (not capillary) for critically ill patients or those with shock/hypotension 1

Life-Threatening Causes to Evaluate

Systematically assess for:

• Disconnection or malfunction of oxygen delivery system 1
• Pulmonary edema 1
• Pneumonia or aspiration 1
• Pulmonary embolism 1
• Bronchospasm 1
• Upper airway obstruction 1
• Residual anesthetic effects or opioid-induced respiratory depression 2

Special Post-Operative Considerations

Obese Patients and OSA

• Reinstate home CPAP immediately on return to ward if oxygen saturation cannot be maintained with supplemental oxygen alone 3
• Supplemental oxygen can be given via CPAP machine or nasal specula under CPAP mask 3
• Insert nasopharyngeal airway before emergence in confirmed OSA to mitigate partial airway obstruction 3
• Observe unstimulated for signs of hypoventilation, apnea, or hypopnea with desaturation before PACU discharge 3

Pain Management Impact

• Utilize multimodal analgesia and regional techniques to reduce systemic opioid requirements 2
• Avoid continuous background infusions with patient-controlled opioids 2
• Consider reduced opioid dosing in OSA patients with vigilance for delayed respiratory depression 2

High-Risk Populations

Age, BMI, and current smoking are significant risk factors for desaturation 4 Sleep apnea syndrome and postoperative opioid administration significantly increase bradypnea risk 4

Monitoring After Oxygen Adjustment

• Observe oxygen saturation for at least 5 minutes after starting or increasing oxygen therapy 1
• Recheck at 1 hour if stable 1
• Use continuous pulse oximetry for critically ill patients 1
• Continue monitoring for at least 8 hours postoperatively in non-ICU patients 4
• Most desaturation events occur after termination of oxygen administration 4

Escalation Criteria

Urgent clinical review required if: 1, 2

• Patient requires oxygen restarted at higher concentration than before to maintain same target saturation
• Persistent hypoxemia despite appropriate oxygen therapy
• pH <7.35 with PCO2 >6.0 kPa (respiratory acidosis) - consider non-invasive ventilation
• Respiratory rate remains >30/min despite oxygen
• Signs of respiratory fatigue or increased work of breathing

Advanced Respiratory Support

• Initiate CPAP or non-invasive positive pressure ventilation for SpO2 <90% despite supplemental oxygen 2
• Continue preoperative CPAP/BiPAP for patients who were using these modalities before surgery 2
• If patient cannot maintain adequate oxygenation despite NIV or high-flow oxygen, mechanical ventilation may be required 5

Common Pitfalls to Avoid

• Do not provide high-flow oxygen empirically without targeted saturation goals 5
• Avoid oxygen therapy alone without checking for hypercapnia in patients with underlying respiratory disease 5
• Do not delay escalation to NIV or mechanical ventilation if signs of respiratory fatigue or persistent hypoxemia 5
• Transient asymptomatic desaturation does not require correction if patient is otherwise stable and recovering 1
• Do not discharge high-risk patients from OSA to unmonitored settings until no longer at risk of respiratory depression 2

Discharge Criteria

Patient is safe to return to ward only when: 3

• Routine discharge criteria are met
• Respiratory rate is normal with no periods of hypopnea or apnea for at least one hour
• Arterial oxygen saturation returns to pre-operative values with or without oxygen supplementation
• Patient can maintain adequate oxygen saturation on room air before discontinuing supplemental oxygen 2