Preoperative Preparation

ANAESTHESIA WITH CONCURRENT RESPIRATORY DISEASES

MODERTOR BY- DR SUCHIT KHANDUJADR GIAN CHAUHAN JR ANAESTHESIA

Preoperative PreparationGeneral assessment-This involves history, examination and investigation.History.Ask about symptoms of wheezeCough Sputum production, Haemoptysis Chest painExercise tolerance, Orthopnoea and paroxysmal nocturnal dypsnoeaDiagnosis of chronic chest complaints such as asthma or bronchiectasis is often known.

Present medication and allergies are noted, and a history of smoking sought.

Previous anaesthetic records may be available and can help in planning care.Examination.Inspect for Cyanosis

Dyspnoea

Respiratory rate

Asymmetry of chest wall movement

Scars, cough and sputum colour.

Percussion and auscultation of chest may suggest Areas of collapse and consolidation,

Pleural effusions,

Pulmonary oedema or infection.

Cor pulmonale may be evident as peripheral oedema and raised jugular venous pressure

Enlarged lymph nodes in the neck may suggest lung cancer.

Investigations.Leucocytosis may indicate active infection, and polycythaemia chronic hypoxaemia.ABG should be performed in patients who are dyspnoeic with minimal exertion and the results interpreted in relation to PIO2.Preoperative hypoxia or carbon dioxide retention indicates the possibility of postoperative respiratory failure. May require a period of assisted ventilation on the Intensive Care Unit.

Pulmonary function tests, provide baseline pre-operative measurements.Chest clinic has charts to compare these results against those predicted for the patients age, sex and weight.The results are also compared against the patient's previous records to assess current disease control.

FEV1.0 (Forced Expiratory Volume in 1 second) and FVC (Forced Vital Capacity) are commonly measured. A reduction in the FEV1.0:FVC ratio indicates obstructive airways disease. (The normal is 0.75 (75%) or more). A reduction in FVC occurs in restrictive lung disease.An FEV1.0 or FVC less than 70% of predicted, or an FEV1.0:FVC ratio less than 65%, is associated with an increased risk of pulmonary complications.

Chest X-rays may confirm effusions, collapse and consolidation, active infection, pulmonary oedema, or the hyperinflated lung fields of emphysema.ECG may indicate P-pulmonale, a right ventricular strain pattern (dominant R waves in the septal leads) or right bundle branch block.

In patients with poor respiratory function premedication (if used) must not cause respiratory depression. Opiates and benzodiazepines can both do thisAre best avoided if possible, or used with caution. Humidified oxygen may be administered.Anticholinergic drugs (e.g. atropine) may dry airway secretions and may be helpful before ketamine .

Specific Respiratory ProblemsCoryza (common cold)Typically, children experience six to eight URIs per yearMay be even more frequent among young children attending nursery school or day care 30%40% of URIs are caused by rhinoviruses;Other virusesincluding coronavirus, respiratory syncytial virus, and parainfluenza viruscontribute significantly to the etiology of the disease.Patients may present with undiagnosed infections including croup (laryngotracheobronchitis), influenza, bronchiolitis, herpes simplex, pneumonia, epiglottitis, and strep throat.Most viral URIs are self-limitingMay produce airway hyperreactivity that persists for several weeks after infection. Viral invasion of the respiratory mucosa may render the airway sensitive to secretions or potentially irritant anesthetic gases.Viral invasion of the respiratory mucosa may render the airway sensitive to secretions or potentially irritant anesthetic gases.Bronchial hyperreactivity resulting from viral infections may be neurally mediated. Atropine, for example, has been shown to block airway hyperreactivity.Viral infections increase the response of airway smooth muscle to tachykinins . De Soto et al. (9) found that children with symptoms of a URI had a significant increase in the risk of postoperative arterial oxygen desaturation and laryngospasm.

Independent risk factors for adverse respiratory events in children with active URIs includeUse of an ETT in a child 10 pack years) with some symptoms.Mainstay of treatment of COPD is bronchodilation both for maintenance and for exacerbations.-agonists and anticholinergics (ipratropium bromide and tiotropium bromide) are used; the latter are proposed to have an additional effect of relieving air trapping.

Long term inhaled steroids are usually only indicated in patients with severe COPD and repeated exacerbations or who have co-existent asthma.Oral steroids are beneficial in the treatment of exacerbations.

Preoperative assessment History and examinationEstablish exercise tolerance, particularly hills and stairsEnquire about frequency of exacerbations, hospital admissions and previous requirements for invasive and non-invasive ventilation.A smoking history is vital

Cough and particularly sputum production has been shown to be an independent risk factor for postoperative pulmonary complications in COPD.Clear history regarding co-morbid conditions is vital.Symptoms and signs of active infection should be sought including green or purulent sputum, increased dyspnoea, wheeze and signs of consolidation. Nutritional status should be assessedPatients with both high and low BMI have increased risk.

InvestigationsChest X-ray is useful to exclude active infection and occult malignancyThe presence of extensive bullous disease highlights the potential risk of pneumothorax.ECG may reveal right heart disease (right ventricular hypertrophy or strain).Spirometry is used to clarify diagnosis and assess severity

GOLD Classification of COPD (based on post bronchodilator FEV1)Stage I: Mild FEV1/FVC