Background

Intraoperative pneumothorax is rare but can be a potentially fatal complication. Pneumothorax in intubated patients with normal lungs is uncommon. Steep Trendelenburg position has been shown to affect respiratory parameters significantly (Takahata et al. 2007). However, a direct correlation between the development of intraoperative pneumothorax and prolonged steep Trendelenburg position has not been established in the literature to the best of our knowledge. We detected this correlation intraoperatively in a patient with no diagnosed underlying lung pathology under general anaesthesia. We emphasise on keeping a high index of suspicion for the development of pneumothorax in prolonged surgeries in steep Trendelenburg positions even in the absence of other significant risk factors.

Case presentation

A 53-year-old female, 156 cm, 54 kg, diagnosed as a case of recurrent umbilical hernia with cystocele and rectocele was planned for vaginal hysterectomy along with open mesh repair for umbilical hernia.

In preanaesthetic evaluation, there were no comorbidities and the patient had a normal physical examination. Routine laboratory investigations were within normal limits. However, a chest x-ray showed a few fibrotic patches in the right mid and left upper lung fields for which no active intervention was required. In the operation theatre (OT), standard monitors were attached, general anaesthesia was given as per standard institutional protocol, and endotracheal intubation was done with an endotracheal tube (ETT) size 7. No attempt at central venous access was taken at any stage. The gynaecologist then proceeded with vaginal hysterectomy surgery with the patient in lithotomy with a steep Trendelenburg position. Approximately 90 min after the surgery started, the Ppeak increased to 36 cmH2O with a decrease in SpO2 to 94%. The rest of the parameters were within normal limits. Upon auscultation, the breath sound of the right lung decreased significantly. Endotracheal suction was done to rule out any secretions and ETT was withdrawn back by up to 2 cm with auscultation. However, the breath sound of the right lung was still decreased. Fio2 was increased to 70% and spo2 gradually improved to 100%. Surgery was interrupted and the patient was brought to a propped-up position for about 15 min. There was 1 episode of drop in BP up to 82/56 mmHg. The surgery was continued again with peak airway pressures of around 32–34 cmH2O whole throughout. The total duration of surgery was about 5 h 30 min.

During extubation, the patient developed laboured breathing, decreased air entry to bilateral lung (right >  > left), and Ppeak was 38 cm H2O. ABG was sent at this point and the results indicated a pH, PaCO2, and PaO2 of 7.09, 72 mmHg, and of 103 mmHg, respectively. Suspicion of pneumothorax was there but it could not be confirmed using ultrasound (USG) as the USG machine of operation theatre complex was non-functional. The patient was not extubated and shifted to ICU. USG was done in ICU which revealed absent lung sliding and the presence of a barcode sign on the right side. Chest x-ray (chest AP view) was performed immediately which confirmed the presence of pneumothorax in the right lung (Fig. 1).

Fig. 1
figure 1

Chest x-ray AP view shows pneumothorax(arrows) in the right lung

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Intercostal Tube drainage (ICTD) was inserted, and a gush of air came out stat. After ICTD insertion, the Ppeak was decreased to 24 cmH2O and the breath sound of the right lung showed a favourable change. The ETCO2 was 38 mmHg, and spo2 was 99% and the ABG findings after an hour improved.

Chest x-ray was repeated after 6 h which showed satisfactory lung expansion and air entry was bilateral equal (Fig. 2).

Fig. 2
figure 2

Chest x-ray AP view shows the improved pneumothorax in the right lung

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The patient was extubated the next morning with ICTD in situ and was maintaining satisfactory oxygen saturation on room air. The patient was discharged to gynae HDU on postoperative day 3.

ICTD was removed on postoperative day 5 and the patient was discharged under satisfactory condition on day 8.

Discussion

Pneumothorax is a rare but potentially dangerous complication, especially during general anaesthesia. The presence of nonspecific changes in haemodynamic and respiratory parameters makes diagnosis quite challenging during the intraoperative period. Moreover, there are high chances of small pneumothorax developing into tension pneumothorax under positive pressure ventilation. Surgical manipulation of areas close to the parietal pleura, including intrathoracic surgeries, as well as central venous line placement are some of the known risk factors for intraoperative pneumothorax (Bacon et al. 2005). In addition, pneumoperitoneum during laparoscopy is a significant risk factor for the development of pneumothorax with a reported incidence of 0.01–0.4% (Phillips and Falk 2011). Rarely, a difficult airway can be a culprit. Masking of signs under general anaesthesia makes recognition difficult and some cases are only identified postoperatively (Chen et al. 2005).

Pneumothorax is frequently related to some underlying lung pathology like chronic obstructive pulmonary disease (COPD) and asthma. To overcome severe bronchial obstruction high airway pressures are required. Correlations between high peak airway pressure and the development of pneumothorax have also been found (Woodring 1985).

Published reports reveal that prolonged steep Trendelenburg positioning increases the risk of postoperative morbidity in patients undergoing robotic surgery for gynaecologic malignancy and urologic procedures (Maerz et al. 2017). Peak and mean inspiratory pressures are increased by pneumoperitoneum and exacerbated after Trendelenburg positioning (Souki et al. 2018). Peak airway pressure (PAP) is generally recognised as the most important risk factor for barotrauma. Although authors dispute the exact level of the safe upper limit, the higher it is, the more likely it is that barotrauma will occur. There is no unique PAP that assures the lack of barotrauma risk. However, it is reasonable to concentrate our efforts on reducing PAP as much as possible (Haake et al. 1987).

In the present case, there was a delay in the diagnosis of pneumothorax intraoperatively as there were no inciting factors for pneumothorax, though there was a presence of nonspecific changes in patient haemodynamic and respiratory parameters. A retrospective analysis of the case made us think that there could be a possibility of some underlying lung pathology or an anatomical defect that might have got unnoticed, superimposed by prolonged steep Trendelenburg position causing raised airway pressures, all of that jeopardising the pulmonary compliance and could have been the reason for alveolar rupture and development of pneumothorax towards the end of the surgery. This case is rare in the sense that to the best of our knowledge, there is no study which shows the incidence of pneumothorax at pressures less than 40 cmH2O (Haake et al. 1987) and in our patient at no point of time the airway pressures went beyond 36 cmH2O. Moreover, in the majority of studies, there was either pneumoperitoneum or some kind of instrumentation that led to pneumothorax which was not in our case.

Ethical statement

Written informed consent was obtained from the patient for publication of this case report.

Conclusions

Anaesthesiologists should always be aware of the risk of intraoperative respiratory complications in the steep Trendelenburg position. Thorough preoperative evaluation to rule out lung pathology and a high index of suspicion should be kept in mind for the possibility of pneumothorax in prolonged surgeries in steep Trendelenburg position.