1

Which cardiac arrhythmias occur following thoracic surgery?

Atrial fibrillation and atrial flutter are the most common, occurring in 10-15% of patients following a lobectomy and in up to 40% following a pneumonectomy.

They usually occur on the 1st-3rd postoperative day and are equally common following open or video-assisted thoracoscopic surgery (VATS).

Atrial fibrillation and flutter are associated with increased morbidity and postoperative length of stay.

The precise aetiology of cardiac arrhythmias following thoracic surgery is unknown but certain pre-operative and intra-operative factors can contribute to their development (Table 1).

2

What are the principles of managing a patient with a postoperative cardiac arrhythmia?

The treatment depends on obtaining a precise diagnosis and the degree of associated haemodynamic compromise.

The aim is to control the ventricular rate, and return to and maintain sinus rhythm.

Electrolyte disturbance, acid-base imbalance and hypoxia should be corrected.

If the above measures fail, pharmacological therapy with anti-arrhythmic medication should be instigated, with digoxin used as first-line therapy.

DC cardioversion should be employed if the patient is acutely compromised.

A cardiology opinion may also be required in certain patients.

There is no evidence that pre-operative anti-arrhythmic therapy is beneficial in reducing the incidence of postoperative atrial fibrillation.

Anticoagulation may be necessary if sinus rhythm is not restored.

3

What is postoperative atelectasis (Figure 1)?

Atelectasis represents collapse of a pulmonary segment or lobe, resulting in a V/Q mismatch and hypoxia.

It is the most common postoperative complication following lung resection and usually occurs 24-48 hours postoperatively in up to 40% of patients, with 5-10% being clinically significant.

Certain patients have an increased risk of developing postoperative atelectasis, including those with:

a)

an inability to cough;

b)

sputum retention;

c)

hypoventilation due to pain, sedation and diaphragmatic splinting;

d)

a pleural effusion, resulting in compression of the underlying lung.

Chest radiological (CXR) features of atelectasis include:

a)

displacement of the hilum;

b)

mediastinal shift towards the side of the collapse;

c)

volume loss of the ipsilateral hemithorax;

d)

elevation of the ipsilateral diaphragm;

e)

crowding of the ribs;

f)

compensatory hyperlucency of the remaining ipsilateral lobes;

g)

silhouetting of the diaphragm or the heart border.

4

What are the principles of managing a patient with atelectasis?

Prevention is the mainstay.

Non-invasive techniques:

a)

regular postoperative physiotherapy;

b)

early mobilisation;

c)

encourage the patient to sit out of bed;

d)

incentive spirometry;

e)

breathing exercises;

f)

nebulisers;

g)

humidified oxygen.

Invasive techniques:

a)

nasotracheal suction;

b)

continuous positive airway pressure (CPAP);

c)

flexible bronchoscopy;

d)

mini-tracheostomy.

5

What is the aetiology of postoperative respiratory failure?

Respiratory failure can be caused by a wide spectrum of underlying pathologies, often in combination, including:

a)

narcotic overdose or inadequate reversal;

b)

bronchospasm;

c)

atelectasis;

d)

pneumonia;

e)

pulmonary oedema, secondary to fluid overload or heart failure;

f)

pre-existent poor underlying lung function (minimal reserve);

g)

pulmonary embolism;

h)

acute respiratory distress syndrome (ARDS).

Respiratory failure can be subclassified as:

a)

Type I – hypoxic (hypoxaemia);

b)

Type II – ventilatory (primarily hypercapnia);

c)

Mixed – combination of hypoxaemia and hypercapnia.

Respiratory failure is the main cause of mortality following thoracic surgery and occurs in 2% of patients, with a 50-100% mortality.

6

What are the principles of management in a patient with postoperative respiratory failure?

Supplemental oxygen by mask or CPAP.

Naloxone for patients with inadequate opioid reversal.

Diuretics for patients with pulmonary oedema.

Broad-spectrum antibiotics.

Anticoagulation for patients with a pulmonary embolus.

Nebulisers for patients with bronchospasm.

Flexible bronchoscopy and suctioning for patients with sputum retention and atelectasis.

Despite the above supportive measures, some patients will also require endotracheal intubation and mechanical ventilatory support.

7

What is acute respiratory distress syndrome (Figure 2)?

Acute respiratory distress syndrome (ARDS) is a very severe form of acute lung injury (ALI) and is defined as an acute condition characterised by bilateral pulmonary infiltrates and severe hypoxia in the absence cardiogenic pulmonary oedema.

The pathogenesis of ARDS includes:

a)

raised pulmonary capillary pressure;

b)

reduced lymphatic drainage;

c)

endothelial damage;

d)

lung hyperinflation;

e)

single-lung ventilation intra-operatively.

ARDS is characterised by increased alveolar-capillary permeability, resulting in an excessive influx of fluid into the alveolar spaces.

It usually presents 2-3 days following an uncomplicated postoperative recovery with dyspnoea and hypoxia.

ARDS is rapid in its progression and more common following a pneumonectomy (5%) compared to a lobectomy (2%).

The radiological features of ARDS include widespread bilateral pulmonary infiltrates.

Most patients are treated with mechanical ventilation and the mortality rate is high (>75%).

8

What are the characteristic features of postoperative pulmonary oedema?

Pulmonary oedema is defined as an accumulation of fluid in the alveoli and lung parenchyma, resulting in impaired gas exchange.

Postoperative pulmonary oedema can be caused by:

a)

excessive peri-operative fluid administration – which may have been used to treat hypotension, intra-operative fluid loss, the hypotensive effect of epidural analgesia or oliguria;

b)

underlying congestive heart failure;

c)

right ventricular dysfunction immediately following a pneumonectomy;

d)

rapid re-expansion of a collapsed lung (Figure 3).

9

What are the characteristic features of postoperative pneumonia (Figure 4)?

Postoperative pneumonia represents a nosocomial infection of the lower respiratory tract.

It is usually caused by bacterial organisms, which originate from the oral cavity, pharynx and hypopharynx, including:

a)

Staphylococcus aureus;

b)

Streptococcus pneumoniae;

c)

Haemophilus influenzae;

d)

Pseudomonas aeruginosa;

e)

Klebsiella spp;

f)

Escherichia coli;

g)

Acinetobacter spp.

The development of postoperative pneumonia is associated with sputum retention and atelectasis.

The CXR usually demonstrates an area of patchy consolidation.

Postoperative pneumonia is treated with:

a)

antibiotic therapy (appropriate to the underlying organism);

b)

supplemental oxygen (if required);

c)

chest physiotherapy.