The Effect of Permissive Hypercapnia on Postoperative Nausea and Vomiting in Patients Undergoing Gynecological Laparoscopic Surgery: A Prospective Randomized Controlled Trial
This prospective randomized controlled trial demonstrates that a permissive hypercapnia ventilation strategy (PaCO2 45–55 mmHg) significantly reduces the incidence of postoperative nausea and vomiting and improves intraoperative regional cerebral oxygen saturation in patients undergoing gynecological laparoscopic surgery compared to conventional normocapnic ventilation.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
After surgery, many patients wake up feeling sick to their stomach or vomiting. This is a common and distressing problem, especially for women undergoing laparoscopic procedures on the reproductive organs. These surgeries use a special technique where the abdomen is inflated with carbon dioxide gas to give the surgeon room to work. While this gas is essential for the operation, it is absorbed into the bloodstream and can upset the body's delicate balance. Doctors have long tried to prevent this nausea by giving patients anti-sickness drugs before the operation, but these medications do not always work. The question remains: can the way doctors manage breathing during the surgery itself help prevent the sickness that follows?
A team of researchers at the First Affiliated Hospital of Dalian Medical University in China decided to test a specific idea about breathing. During general anesthesia, patients are connected to a machine that breathes for them. Usually, doctors adjust this machine to keep the level of carbon dioxide in the patient's blood within a standard, normal range. However, the researchers wondered if allowing that carbon dioxide level to rise slightly higher than normal might actually be beneficial. This approach, known as permissive hypercapnia, accepts a mild increase in carbon dioxide rather than forcing the breathing machine to work harder to keep levels low. The team wanted to see if this strategy could reduce the frequency of nausea and vomiting after gynecological laparoscopic surgery.
To find the answer, the researchers recruited 88 women aged 18 to 64 who were scheduled for these specific surgeries. All the women were non-smokers and in generally good health. Before the operation began, the researchers randomly assigned each woman to one of two groups. The first group received the standard care, where the breathing machine was carefully adjusted to keep their carbon dioxide levels between 34 and 45 millimeters of mercury. The second group received the new strategy, where the machine was set to allow their carbon dioxide levels to rise and stay between 45 and 55 millimeters of mercury. Both groups received the same anesthesia drugs and the same anti-sickness medication before the surgery started, ensuring that the only major difference was how their breathing was managed during the operation.
The results showed a clear difference between the two groups. In the group that received the standard, normal carbon dioxide levels, more than 70 percent of the women experienced nausea, retching, or vomiting within 24 hours after the surgery. In contrast, the group that was allowed to have slightly higher carbon dioxide levels saw a much lower rate of these symptoms, with only about 39 percent of the women affected. The women in the higher carbon dioxide group also reported fewer total episodes of nausea and vomiting over the day following the operation. While the need for extra rescue medication to stop vomiting was similar in both groups, the overall burden of sickness was significantly lighter for those who received the permissive hypercapnia strategy.
The researchers also monitored the oxygen levels in the women's brains during the surgery. They found that while the brain oxygen levels were similar at the start, the group with the higher carbon dioxide levels had significantly better oxygen saturation in their brains later in the procedure, specifically 60 minutes after the gas was introduced into the abdomen and again at the end of the surgery. Carbon dioxide is known to widen blood vessels, which can increase blood flow. The researchers suggest that this increased blood flow may have delivered more oxygen to the brain, and this improved state of the brain might be the reason why these patients felt less sick afterward. However, the study did not prove exactly how this connection works, only that the two things happened at the same time.
This study provides strong evidence that adjusting the breathing strategy during surgery can change how a patient feels after waking up. By allowing a controlled, mild increase in carbon dioxide, doctors were able to significantly lower the risk of postoperative nausea and vomiting for women undergoing gynecological laparoscopic surgery. The findings also highlight a link between this breathing strategy and better oxygen levels in the brain during the operation. While the exact biological mechanism remains a subject for future investigation, the results offer a promising, non-drug method to improve recovery for patients facing these common surgeries.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.