Postoperative hypoxia
- Lack of alveolar ventilation
- Hypoventilation (airway obstruction, opiates)
- Bronchospasm
- Pneumothorax
- Arteriovenous shunting (collapse, atelectasis)
- Lack of alveolar perfusion
- Ventilation-perfusion mismatch (pulmonary embolism)
- Impaired cardiac output
- Decreased alveolar diffusion
- Pneumonia
- Pulmonary oedema
Atelectasis
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Hypoxaemia is often seen during the first 48 hours after most major operations
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Due to a reduction in functional residual capacity
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Significant atelectasis is more often seen
-
The basic mechanisms leading to atelectasis are:
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Increased volume of bronchial secretions
-
Increased viscosity of secretions
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Reduced tidal volume and ability to cough
Clinical features
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Postoperative pyrexia - usually presenting at about 48 hours
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Often accompanied by tachycardia and tachypnoea
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Examination shows reduced air entry, dullness
on percussion and reduced breath sounds
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X-ray shows consolidation and collapse
Treatment
-
Intensive chest physiotherapy
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Nebulised bronchodilators
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Antibiotics for associated infection
Pneumonia
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Nosocomial pneumonia occurs in 1% of all patients admitted to hospital
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Occurs in 15-20% of unventilated ITU patients
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Occurs in 40-60% of ventilated ITU patients
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Organisms involved include
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Gram-negative bacteria (Pseudomonas aeruginosa, Enterobacter)
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Staph. aureus
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Anaerobes
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Haemophilus influenzae
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No evidence that prophylactic antibiotics reduce the risk of pneumonia
Aspiration pneumonitis
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Aspiration of gastric contents results in a chemical pneumonitis
-
Most commonly seen in apical segments of right lower lobe
-
If unrecognised or inadequately treated it can result in a secondary bacterial
infection
-
Secondary infection is usually with gram-negative and anaerobic organisms
Treatment
-
Tilt table head down and suck out pharynx
-
Consider intubation and endotracheal suction
-
Prophylactic antibiotics should be given
-
No evidence that steroids reduce inflammatory response
Bibliography
Johnson J L, Hirsch C S. Aspiration pneumonia: recognising and managing a potentially
growing disorder. Postgrad Med 2003; 113: 99-112. |