Philippe Goater

Bilateral asymptomatic pneumothorax in early post-operative period.

Sir, Bilateral asymptomatic pneumothorax in the early post-operative period remains a possible and often challenging anaesthetic concern. We believe that recalling such complication is pedagogical.[1] A 58-year-old, 176-cm, 62-kg, American Society of Anaesthesiologists physical status I man underwent conservative mandibulectomy. Pre-operative evaluation showed chronic obstructive pulmonary disease related to active smoking of 63-packet years of cigarettes. Tomodensitometry assessment had shown bullous emphysema with numerous blebs at the apices. After establishing routine monitoring, general anaesthesia was induced using propofol, remifentanil and cisatracurium. Nasotracheal intubation was easily performed. Anaesthesia was maintained using desflurane (3–4%) in N2O-O2 mixture (50–50), sufentanil and cisatracurium. Mechanical ventilation (MV) was performed using a tidal volume of 7 ml/kg, respiratory rate 12/min, I: E ratio 1:2, peak inspiratory pressure (PIP) of 12–14 cm H2O, and expired CO2 (PETCO2) of 30–35 mm Hg. Surgery was performed in the supine position. At the end of the procedure, tracheotomy was performed, and a nasogastric tube was inserted for post-operative enteral feeding. In the post-anaesthesia care unit, the patient was spontaneously ventilating, conscious, calm and pain-free. Transcutaneous oxygen saturation was 98% with O2 4 L/min, arterial blood pressure was 140/70 mm Hg, and heart rate 75 beats/min. Bilateral pneumothorax was diagnosed on chest X-ray, performed to confirm adequate nasogastric tube positioning [Figure 1]. Two chest tubes were inserted. Tracheo-bronchial endoscopy excluded a tracheal injury. The drains were removed 4 days later without further complications. Figure 1 Chest X-ray showing bilateral pneumothorax Many risk factors for intraoperative pneumothoraces were identified. During MV, pneumothorax can develop as a result of increasing of PIP caused by bronchial spasm.[1] Pneumothoraces have been reported as a complication of high-frequency jet ventilation.[2] Tracheal injury during mediastinal or neck surgery has been associated with pneumothorax.[3] Carbon dioxide pneumothoraces have been reported during laparoscopic surgery.[4] N2O has been known for a long time to diffuse into body cavities increasing the volume of pneumothorax.[5] In patients with bullous emphysema, N2O may increase the volume of bullae increasing the risk of rupture. In patients with bullous emphysema, MV may increase intrinsic positive end-expiratory pressure through gas trapping, resulting in bullous expansion and rupture. Coughing may be a precipitant factor of bullous rupture during MV or when the patient recovers consciousness.[2] Barlow et al., investigated 100 patients undergoing tracheotomy and reported a 2% incidence of pneumothoraces, but did not advocate routine chest X-ray following this procedure.[6] Pneumothorax is often diagnosed in a patient with subcutaneous or mediastinal emphysema, oxygen desaturation, circulatory disturbance, or MV impairment with increase of peak pressure.[1,3,4] However, it is likely to go unnoticed post-operatively in a sedated, pain-free patient receiving supplemental oxygen, as in this case. Several risk factors were found in the reported patient including, heavy smoking, bullous emphysema, neck surgery, tracheotomy, MV and using of N2O. Indeed, N2O must be avoided in the presence of bullous emphysema. Diagnosis was made on chest X-ray requested for another purpose. Whether chest X-ray must be ordered as a routine during post-operative care in a patient with known risk factors needs to be discussed and agreed to at a local level.

Adducted vocal cords relieved by neuromuscular blocking drug: a cause of impaired mechanical ventilation when using a Laryngeal Mask Airway: two photographically documented cases

Two cases of vocal cord closure, which was responsible for acute intraoperative impairment of mechanical ventilation in two patients with entropy-controlled depth of anesthesia, are reported. Administration of low-dose neuromuscular blocking drug was associated with immediate vocal cord relaxation and restoration of efficient mechanical ventilation.