Carbon Dioxide Pneumothorax Following Retroperitoneal Laparoscopic Partial Nephrectomy

A Case Report and Literature Review

Qiongfang Wu; Hong Zhang


BMC Anesthesiol. 2018;18(202) 

In This Article

Discussion and Conclusion

Large or symptomatic pneumothorax usually necessitates thoracocentesis or chest tube placement. But capno-thorax may warrant a different treatment. Table 1 summarized cases which reported moderate to large symptomatic capno-thorax while implemented conservative treatments. Different from these described above, in our case, the type of surgery route was retroperitoneal. The symptom was more severe (SpO2 30%) and happened after gas deflation and before extubation. The patient was awake at first but fell into unconsciousness later. It's more urgent and hard for us to diagnose and decide whether it was suitable to adopt an invasive method. Fortunately, the severe condition didn't last for a long time. We also retrieved some cases in whom capno-thorax occurred in retroperitoneal urological surgeries. But most of these happened intraoperatively and implemented thoracocentesis or chest tube placement,[8–11] or had confirmed diaphragm injury and recovered after converting to open surgery.[12] Although study showed CO2 absorption during laparoscopy did not depend on the route of surgery,[13,14] for retroperitoneal route, the restriction on working space and field of view may increase the risk of inadvertent organ damage.

Causes for Pneumothorax

Pneumothorax during laparoscopic procedures has been reported and the possible causes are:[3,8–14] First, barotrauma and rupture of bullae during mechanical ventilation or during central venous line placement may contribute to air pneumothorax. Second, unrecognized congenital defect such as diaphragmatic defects[15] or pleuroperitoneal fistulas could predispose patients to pneumothorax. Third, increased operative duration is likely to compel more CO2 absorption. Study showed that PetCO2 greater than 50 mmHg and operative time greater than 200 min were risk factors for pneumothorax.[16] Fourth, higher insufflation pressure likely leads to a large amount of CO2absorption. Several cases have been reported to get pneumothorax during laparoscopic surgeries with an insufflation pressure of 12–15 mmHg[2,17,18] whereas insufflation pressure under 12 mmHg might still cause pneumothorax;[19] furthermore, rapid insufflation would allow the intracavitary pressure to increase suddenly, contributing to pneumothorax[11] because retroperitoneal space is not a true cavity and has lower compliance than the abdominal cavity. Fifth, it is also possible for CO2 to dissect into the pleural space along the vena cava or aorta.[16] Finally, pleural injury due to errant trocar placement or diaphragmatic injury possibly accounts for pneumothorax.[4,20]

In our case, the symptomatic pneumothorax was unanticipated as the procedure and anesthesia practice was uneventful. The patient was young and healthy. Operating duration and intraoperative PetCO2 were also acceptable. But the diaphragmatic defect cannot be excluded. Though operation on the lower pole of the kidney is less likely to injure diaphragm, the procedure to explore the lost suture might injure it unconsciously. Besides, CO2 could also dissect into the pleural space along the vena cava. All these possible reasons suggest not air but CO2 pneumothorax.

Clinical Manifestations and Diagnosis

Pneumothorax could bring out pulmonary atelectasis, elevate inspiratory airway pressure, PetCO2 as well as PaCO2 and decrease breath sounds and blood pressure. Hypotension occurs due to the decreased venous return and cardiac output. However, in this case, these changes were not obvious during procedure but appeared after the termination of mechanical ventilation. Possible reasons are that respiratory depression after the cessation of mechanical ventilation combined with pneumothorax exaggerated the clinical manifestation.

Chest computer tomography scan is the gold standard for diagnosis of pneumothorax.[21,22] Chest X-ray is usually as the initial tool to detect the potential cases. All the cases list above was diagnosed by Chest X-ray. However, it has been demonstrated that point-of-care transthoracic ultrasound, a cheaper, nonradiative and timely tool, is more accurate than chest X-ray with 81% sensitivity and 100% specificity.[23,24] Anterior absent lung sliding plus A lines plus lung point indicated pneumothorax.[23] If lung is totally collapsed, lung point isn't visualized; lung point on the mid axillary line differentiates large and small pneumothorax, coinciding with a cut-off set at 15% of lung collapse,[25] and could guide decision-making in treatments. This technique is extremely important for anesthesiologists to practice in the operating room. However, we didn't perform ultrasound scan because of inexperience.

Practice Taken to Alleviate Carbon Dioxide Pneumothorax

The treatment can vary depending on the causes and severity of the pneumothorax. FiO2 should be increased and N2O supply should be stopped. CO2insufflation could be reduced or discontinued. Endotracheal intubation, hyperventilation and higher positive end-expiratory pressure should be maintained.[26]

Traditionally, a chest tube could be placed if a large pneumothorax or consequent cardiovascular or respiratory collapse is diagnosed. But capno-thorax may warrant a different treatment strategy. The solubility of CO2 is 20 times more than nitrogen and has an increased diffusion coefficient compared to air, which is composed mostly of nitrogen and oxygen. Higher solubility of a gas means more molecules can diffuse across a membrane in a given time. Experimental and clinical evidence demonstrated that resolution of capno-thorax can be more rapid than air pneumothorax, and usually complete re-expansion of the compressed lung could be achieved within several hours,[15,27–29] even within 30–60 min.[30]We didn't implement thoracentesis or place a chest tube but provided oxygen supply and intensive care because it is found that the probability of pneumothorax caused by CO2 is higher than that by air, patient's condition was getting better and the source of CO2 was no longer feeding the retroperitoneum. The woman returned to normal state within 1 h although chest pain disappeared completely the next day.

In conclusion, pneumothorax, although rare, is a serious complication of laparoscopic nephrectomy. Anesthesiologists, when facing this crisis, should recognize pneumothorax right away. Point-of-care transthoracic ultrasound should be recommended to diagnose. Different from air pneumothorax, CO2pneumothorax, even with a large volume, can be resolved spontaneously without invasive management.