Nitrous oxide insufflation does not increase the incidence of gas embolism during laparoscopic cholecystectomy : Detection by transoesophageal echocardiography

Abstract EN

ckground: Laparoscopic cholecystectomy is the operation of choice for gall bladder diseases.

Carbon dioxide (CO2) is the standard insufflation gas although it produces pain, hypercarbia and acidosis.

These side effects could be avoided if nitrous oxide (N2O) replaces CO2- Gas embolism is a rare but potentially fatal complication of pneumoperitoneum.

As N20 is less soluble in blood, it is theoretically more precipitating of gas embolism (GE) than C02.

Transesophageal echocardiography (TEE) is the most sensitive tool to discover sub-clinical GE events.

The aim of this study was to compare C02 and N20 pneumoperitoneum during laparoscopic cholecystectomy regarding GE events.

Moreover, we aimed at defining which stage of the procedure precipitates more GE.

Methods: In a prospective randomized clinical trial, 24 patients with ASA score I or II were scheduled for laparoscopic cholecystectomies, which were performed by the same surgeon.

They were divided into two equal groups where either C02 or N20 was used for pneumoperitoneum.

Standard general anesthesia was used in all cases.

TEE probe was introduced to monitor GE events.

The procedure was divided into four operative stages (Tl=insufflation, T2=dissection of cystic duct & artery, T3=gall bladder bed dissection and T4=extraction & desufflation).

For each stage, the number and score (from 1-3) of gas embolism episodes were recorded.

In addition, we recorded heart rate (HR), mean arterial blood pressure (MAP), saturation of oxygen (Sa02) and end-tidal C02 (ET CO2) immediately after induction (base line), during insufflation, and every 10 minutes of the procedure.

Results: Both C02 and N20 groups were comparable regarding sex, age, ASA score, duration of each operative stage and the total operative time.

There were no statistically significant differences between the two groups regarding HR, MABP or Sa02.

However, C02 group showed higher intraoperative levels of ET C02- All operations exhibited GE events with a mean of 5.58 (±3.39) and a range of 1-14 events.

The mean number of GE events per ten minutes was 1.50 (±1.90) ranging from 0-8 regardless of the groups.

Comparing the two groups, the number of GE events per ten minutes showed no significant differences except for T3 and the whole operation, which showed slight increase in the C02 group.

The score of GE events were not significantly different between the two groups except for Tl and the whole operation, which exhibited more scores in C02 group.

Most of the GE events (94.1%) were associated with positive gas flow.

The stage of insufflation (Tl) showed significantly higher number of GE events compared to any of the other stages.

Conclusions: During laparoscopic cholecystectomy, as insufflating gas does not increase the incidence of GE events compared to C02- On the contrary, N20 exhibits slightly less GE events in some of the operative stages.

The stage of insufflation predisposes to more GE events than the rest of the operation.

Most of the GE events are associated with some rate of gas flow into the peritoneal cavity whatever the type of gas is.

Therefore, surgeons and anesthetists should be more cautious whenever there is active gas flow into the peritoneal cavity for fear of GE.