Anæsthesia in Chest Surgery, with Special Reference to Controlled Respiration and Cyclopropane: (Section of Anæsthetics).
Problems in chest surgery: Cases with prolonged toxaemia or amyloid disease require an anaesthetic agent of low toxicity. When sputum or blood are present in the tracheobronchial tree the anaesthesia should abolish reflex distrubances and excessive sputum be removed by suction. The technique should permit the use of a high oxygen atmosphere; controlled respiration with cyclopropane or ether fulfil these requirements. Open pneumothorax is present when a wound of the chest wall allows air to pass in and out of the pleural cavity. The lung on the affected side collapses and the mediastinum moves over and partly compresses the other lung.The dangers of an open pneumothorax: (1) Paradoxical respiration-the lung on the affected side partially inflates on expiration and collapses on inspiration. Part of the air entering the good lung has been shuttled back from the lung on the affected side and is therefore vitiated. Full expansion of the sound lung is handicapped by the initial displacement of the mediastinum which increases on inspiration. The circulation becomes embarrassed.(2) Vicious circle coughing. During a paroxysm of coughing dyspnoea will occur. This accentuates paradoxical respiration and starts a vicious circle. Death from asphyxia may result.Special duties of the anaesthetist: (1) To carry out or supervise continuous circulatory resuscitation. During a thoracotomy a drip blood transfusion maintains normal blood-pressure and pulse-rate.(2) To maintain effcient respiration.Positive pressure anaesthesia: Risk of impacting secretions in smaller bronchi with subsequent atelectasis; eventual risk of CO(2) poisoning without premonitory signs.Controlled respiration: (1) How it is produced. (2) Its uses in chest surgery.Controlled respiration means that the anaesthetist, having abolished the active respiratory efforts of the patient, maintains an efficient tidal exchange by rhythmic squeezing of the breathing bag. This may be done mechanically by Crafoord's modification of Frenkner's spiropulsator or by hand.Active respiration will cease (i) if the patient's CO(2) is lowered sufficiently by hyperventilation, (ii) if the patient's respiratory centre is depressed sufficiently by sedative and anaesthetic drugs, and (iii) by a combination of (i) and (ii) of less degree.The author uses the second method, depressing the respiratory centre with omnoponscopolamine, pentothal sodium, and then cyclopropane. The CO(2) absorption method is essential for this technique, and this and controlled respiration should be mastered by the anaesthetist with a familiar agent and used at first only in uncomplicated cases.The significance of cardiac arrhythmias occuring with cyclopropane is discussed.The place of the other available anaesthetic agents is discussed particularly on the advisability of using local anaesthesia for the drainage of empyema or lung abscess.Pharyngeal airway or endotracheal tube? Anaesthesia may be maintained with a pharyngeal airway in many cases but intubation must be used when tracheobronchial suction may be necessary and when there may be difficulty in maintaining an unobstructed airway.A one-lung anaesthesia is ideal for pneumonectomy. This may be obtained by endotracheal anaesthesia after bronchial tamponage of the affected side (Crafoord, v. fig. 6b) or by an endobronchial intubation of the sound side (v. figs. 9b and 9c). Endobronchial placing of the breathing tube may be performed "blind". Before deciding on blind bronchial intubation, the anaesthetist must examine X-ray films for any abnormality deviating the trachea or bronchi. Though the right bronchus may be easily intubated blindly as a rule, there is the risk of occluding the orifice of the upper lobe bronchus (fig. 9d) when the patient will become cyanosed. If the tube bevel is facing its orifice the risk of occlusion will be decreased (fig. 9c).Greater accuracy in placing the tube can be effected by inserting it under direct vision. Instruments for performing this manoeuvre are described.In lobectomy for bronchiectasis the anaesthetist must try to prevent the spread of infection to other parts. Ideally, the bronchus of the affected lobe should be plugged with ribbon gauze (Crafoord, v. fig. 6c) or a suction catheter with a baby balloon on it placed in the affected bronchus. In the presence of a large bronchopleural fistula controlled respiration cannot be established during operation. As the surgeon is rarely able to plug the fistula, if pneumonectomy is to be performed intubation for a one-lung anaesthesia is the best method. During other procedures it is essential to maintain quiet respiration.In war casualties it is almost always possible, with the technique described, to leave the lung on the affected side fully expanded and thus frequently to restore normal respiratory physiology. Co-operation between surgeon and anaesthetist is essential.
Nosworthy
M D
MD