Postoperative Pulmonary Complications (PPCs)

Definition

Incidence and Morbidity

Types of PPCs

1. Atelectasis - Most common; collapse of alveoli, especially in dependent lung zones after general anesthesia
2. Pneumonia - Hospital-acquired or ventilator-associated; greatest mortality risk
3. Respiratory failure - Defined as mechanical ventilation >48 hours postoperatively or unplanned re-intubation
4. ARDS - Diffuse alveolar damage; triggered by sepsis, aspiration, massive transfusion, or direct lung injury
5. Bronchospasm - Especially in asthmatics or smokers; intraoperative or early postoperative
6. COPD exacerbation - Acute worsening in patients with underlying obstructive disease
7. Aspiration pneumonitis/pneumonia - Chemical injury or bacterial infection from aspiration of gastric contents
8. Respiratory arrest - Related to sleep-disordered breathing/OSA, narcotic overdose, or residual neuromuscular blockade
9. Pleural effusion / pulmonary embolism - Less commonly classified, but significant PPCs in surgical context

Risk Factors

Patient-Related Risk Factors (with Odds Ratios)

Procedure-Related Risk Factors

Preoperative Assessment

• Clinically: ASA classification, history of dyspnea, exercise tolerance (≥2 flights of stairs without stopping = acceptable risk), body habitus, current pulmonary medications
• SpO2 on room air: Baseline hypoxemia (SpO2 <90% or PaO2 <60 mmHg) defines a high-risk group
• ARISCAT score: A validated risk scoring tool using 7 variables (SpO2, respiratory infection, anemia, surgical site, duration, emergency, age) to stratify risk as low (<26), intermediate (26-44), or high (≥45)
• PFTs: Useful in patients with known COPD, asthma, or IPF; NOT routinely indicated for all surgical patients; not a threshold tool to deny surgery
• 6-minute walk test / CPET: For patients with dyspnea and normal echocardiogram/PFTs
• ABG: Not routinely useful; relevant only for new/worsening symptoms or suspected OHS with elevated bicarbonate
• Chest X-ray: Not routine; reserved for symptomatic patients

Prevention and Risk Reduction

Preoperative Measures

• Smoking cessation: Even 8 weeks before surgery significantly reduces risk
• Optimization of chronic lung disease: Maximize bronchodilators, corticosteroids for COPD/asthma; continue all pulmonary medications except theophylline through the perioperative period
• Inspiratory muscle training (IMT): Reduces PPCs, especially in high-risk patients
• Weight reduction where appropriate
• Patient education: About deep breathing exercises, incentive spirometry, coughing techniques
• Delay elective surgery if acute respiratory infection is present

Intraoperative Measures

• Lung-protective ventilation: Low tidal volumes (<10 mL/kg), PEEP ≥5 cmH2O, plateau pressure <30 cmH2O; a landmark study (Ladha et al., ~70,000 patients) showed this significantly reduced PPCs (Miller's Anesthesia, p. 9316)
• Regional/neuraxial anesthesia preferred over general anesthesia where feasible
• Avoid long-acting neuromuscular blocking agents (NMBAs); ensure adequate reversal with sugammadex/neostigmine before extubation
• Minimize duration of anesthesia
• Aspiration precautions: Rapid sequence induction in at-risk patients; avoid Trendelenburg positioning prolonged beyond necessity
• Laparoscopic approach preferred over open where possible (reduces splinting and atelectasis)

Postoperative Measures

Specific PPC Management

Atelectasis

• Incentive spirometry, deep breathing, early ambulation
• Chest physiotherapy, mucolytics
• Bronchoscopy for lobar atelectasis with mucus plugging

Postoperative Pneumonia

• Sputum culture and targeted antibiotics
• Chest physiotherapy
• Adequate hydration; consider bronchoscopy if not responding

Respiratory Failure / ARDS

• ICU admission; mechanical ventilation with lung-protective settings (Vt 6 mL/kg ideal body weight, PEEP titration)
• Prone positioning for severe ARDS (P/F ratio <150)
• Neuromuscular blockade in early severe ARDS
• Daily sedation interruption and spontaneous breathing trials for weaning

Bronchospasm

• Beta-2 agonists (salbutamol nebulization)
• IV magnesium sulphate in refractory cases
• Short course systemic corticosteroids

Summary

• Murray & Nadel's Textbook of Respiratory Medicine, 2-Vol (pp. 822-826)
• Miller's Anesthesia 10e (pp. 3959-3962, 9315-9316)
• Harrison's Principles of Internal Medicine 22e (Table 492-6)
• Fischer's Mastery of Surgery 8e (pp. 271-272)
• Ladha et al. - lung-protective ventilation in 70,000 patients (cited in Miller's Anesthesia)
• Huang et al., BMJ 2026 - non-drug interventions for PPCs after abdominal surgery