Ultrasonography Guided Pneumoperitoneum for Laparoscopic Surgery in Morbidly Obese Patients

Ultrasonography Guided Pneumoperitoneum for Laparoscopic Surgery in Morbidly Obese Patients: A Single-blinded Randomized Control Study (USP TRIAL)

Bariatric Surgery for morbid obesity is indicated when BMI > 40 kg/m2 without comorbidities or BMI > 35 kg/m2 with co-morbidities. Different surgeries performed for obesity are classified as restrictive, malabsorptive, and hybrid procedures.

Because laparoscopic surgery has increased the interest and growth of bariatric surgery, soaring demand for laparoscopic bariatric surgery from patients has boosted the boom in bariatric surgery worldwide.

Achieving pneumoperitoneum is the initial and one of the most crucial steps in any laparoscopic surgery, giving the surgeon working space to operate on a particular organ/organ system. Usually, pneumoperitoneum is achieved either by a closed technique with a veress needle or an open technique with many variations like finger assisted or the conventional open technique.

Given the excess amount of subcutaneous fat in morbidly obese patients, putting a veress needle to achieve pneumoperitoneum successfully is particularly challenging which takes a toll on the operating surgeon when he/she is trying to locate the midline one can either overshoot to cause omental emphysema or undershoot getting lost in the subcutaneous fat. It is usually done in the supra umbilical area. Sometimes, due to previous surgical scars other sites are preferred.

Sonography is routinely used by radiologists with negligible radiation exposure. Anesthesiologists in the operating room have used it for many assisted procedures like central line insertion / giving nerve blocks. It can also be used in obese patients undergoing metabolic surgery to assist in creating pneumoperitoneum by a veress needle.

Advantages of Intraoperative ultrasonography in this particular study :

1. To quantify the thickness of subcutaneous fat
2. To visualise the linea alba and guide the veress needle safely into the peritoneal cavity
3. Real-time visualisation of the pneumoperitoneum created
4. Avoid complications like omental emphysema, bowel or vascular injury

All patients above the age of 18 years with morbid obesity planned for Laparoscopic bariatric surgery will be considered for inclusion in the study. The patient will be explained about the study and asked to sign an informed consent form. The patient's eligibility for the study will be checked by a competent radiologist through pre-operative ultrasonography. All patients will undergo metabolic surgery by a single competent surgeon per the standard operating protocol under general anaesthesia. A single dose of prophylactic antibiotic will be administered 30 minutes before the incision, the patient will be well strapped, and the port sites will be measured and marked. In group A, Ultrasonography will be used to locate the midline precisely and for subsequent puncturing with a Veress needle to enter the peritoneal cavity and the pneumoperitoneum created under real-time vision. In group B, the veress needle is inserted blindly, as regularly done in any other laparoscopic surgery, and the successful pneumoperitoneum is confirmed by percussion on the abdomen. Time taken and the number of attempts for achieving pneumoperitoneum and complications, if any, in both groups will be recorded by an independent assessor.

Sample size calculation :

There are no similar studies done before to assess the role of Ultrasonography in achieving pneumoperitoneum. Hence, the sample size was calculated for a pilot study, as per the recommendation of Sim J and Lewis M, considering precision, proportion, and efficiency. The trial was planned through a study of a continuous variable in two independent, Blind vs. USG guided Veress needle insertions to determine if the two study groups differ in the time taken to start pneumoperitoneum successfully.

The study used for calculating sample size :

Total sample size: 20 in each arm Blinding: Single blinded where only the patient is blinded

Inclusion Criteria:

• All patients in the age group of 18 -65 years undergoing laparoscopic bariatric surgery with weight >100 kg
• Subcutaneous fat thickness of more than 5 cm as determined by pre-operative ultrasonography
• BMI > 40 kg/m2

Exclusion Criteria:

• Patients who don't give consent and do not understand the nature of the study
• Patients undergoing a re-do surgery