Anesth. mgmt: Asthma
Clinical - Respiratory/Pulmonary
If intraoperative wheezing should develop, nonbronchospastic causes of wheezing (mechanical obstruction of the endotracheal tube, endo- bronchial intubation, pulmonary aspiration, pulmonary embolism, pulmonary oedema, tension pneumothorax, and negative pressure inspiration) must be ruled out.
The first step is to deepen the level of anaesthesia via the i.v. or inhalational route or both. Administration of 100% oxygen should be instituted to prevent hypoxemia. Beta 2-agonists via metered dose inhaler should be administered through the airway. It is important to consider the fact that delivery of aerosolized agents during mechanical ventilation is not adequate, being estimated that as little as 1% to 3% of a dose of nebulized medication actually reaches the lungs of a patient on positive pressure ventilation. The amount of aerosol reaching the lungs could be improved by means of an increase in respiratory time, a reduction of respiratory rate, an increase in the volume of nebulizer fill, and positioning of the nebulizer between the Y-piece and catheter mount or on the inspiratory limb of the ventilator circuit Y-piece when jet nebulizers are used. Epinephrine, either subcutaneously or intravenously, can help in severely bronchospastic patients. Corticosteroids can be utilized, but their onset of action takes place within 4 to 8 h of administration.
Leukotriene receptor antagonists and mast cell inhibitors have no use in acute bronchospasm. Intravenous aminophylline can be started, but side effects such as tachycardia and hypertension may limit its usefulness. As a result, methylxantines are no longer recommended for acute exacerbations. A smooth, slow emergence minimizes the risk of bronchospasm. Deep extubation can be attempted. if no airway difficulties were encountered during induction. If deep extubation is contraindicated, the patient may be taken to the postanesthesia care unit intubated and opioids administered to facilitate tolerance to the endotracheal tube.
When the patient is awake and possesses appropriate airway reflexes, extubation can occur. Intravenous lidocaine may be of use in preventing bronchospasm with extubation.