Bundling and Unbundling the Laparoscopic Electrosurgery Cord With the Camera Cord

• Histologic thermal injury to umbilical port site skin [ Time Frame: 1 day ] [ Designated as safety issue: Yes ]
  Shave biopsy of skin at the umbilical port site after elective laparoscopic cholecystectomy will be performed. The primary outcome is histologic evidence of burn at these port sites.
  
  

• Histologic evidence of burn at the epigastric port site skin. [ Time Frame: 1 day ] [ Designated as safety issue: Yes ]
  Shave biopsy of skin at the epigastric port site after elective laparoscopic cholecystectomy will be performed. The secondary outcome is histologic evidence of burn at this port site.
  
  
• Histologic evidence of thermal injury at medial assistant port site [ Time Frame: 1 day ] [ Designated as safety issue: Yes ]
  Shave biopsy of skin at the medial assistant port site after elective laparoscopic cholecystectomy will be performed. The primary outcome is histologic evidence of burn at these port sites.
  
  

We hypothesize that the unbundling of camera and active electrode cords will reduce the incidence of capacitive coupling thermal injuries to the skin adjacent to the camera port site in comparison to bundled active electrodes/camera cords during laparoscopic cholecystectomy operations.

SPECIFIC AIMS:

1. Compare incidence of skin burns by histology at the camera port site (umbilical port site) with bundled active electrode/camera cords to unbundled active electrode/camera cords.
2. Compare incidence of skin burns by histology at the active electrode port site (epigastric port site) with bundled active electrode/camera cords to unbundled active electrode/camera cords.
3. Compare incidence of skin burns by histology at the assistant port site with bundled active electrode/camera cords to unbundled active electrode/camera cords.

OUTCOME MEASURE:

Histologic evidence of thermal injury at the skin biopsy sites of the active electrode port, the camera port and the medial assistant port.

POPULATION TO BE ENROLLED:

Subjects undergoing elective cholecystectomy will be recruited in pre-operative clinic. All subjects will be 18 years and older.

STUDY DESIGN AND METHODS:

Written informed consent will be obtained in all subjects prior to enrollment. Subjects will be randomized on the day of surgery to undergo the laparoscopic cholecystectomy operation with either the bundled or unbundled camera and active electrode cords. The randomization process will occur by a random number generator. A total of 84 subjects will be recruited; 42 subjects per group. Shave skin biopsies will be performed at the lower edge of the incisions of the active electrode port, the camera port and the medial assistant port. The incisions and skin will be otherwise opened and closed in the routine clinical manner. The biopsy specimens will be analyzed for thermal injury by a blinded pathologist.

The incidence of skin burns created bundled or unbundled camera and active electrode cords will be compared individually at all three port sites by a blinded pathologist for histologic evidence of thermal injury.

Statistical analysis using a chi-squared test will be comparing the incidence of thermal injury at the each biopsy site for subjects with and without bundled cords. The primary outcome variable is thermal injury of skin at the umbilical trocar site, which is the camera trocar.

Baseline demographic information will be recorded on all patients: age, gender, BMI, operating room time, pre-op diagnosis, gallbladder histology, blood loss, and need to convert to open surgery.

SAMPLE SIZE CALCULATION:

The incidence of skin burns at the umbilical trocar site with bundled cords was 55% (11/20) in our previous study. Our prior benchtop research found that bundled cords resulted in an increase of temperature of 38.2°C at the tip of the telescope in comparison to a 15.7°C increase in temperature with separated cords. This finding suggests that 41% (15.7/38.2) of the heat is produced when the camera cord is unbundled from the active electrode cord in comparison to when the cords are bundled. This data is used to estimate that the unbundled cord group will have an incidence of thermal injury of 23% (0.41 x 55%).

Power 80% A sample size calculation comparing proportions was performed which compared 0.55 (bundled cords) incidence of thermal injury versus 0.23 (unbundled cords) incidence of thermal injury. A sample size of 36 per group has the power (1-β) 0.80 to detect a difference assuming α=0.05. We estimate a 15% dropout rate (this would be individuals who between their consent in pre-operative clinic and their operation decide to withdraw from the study). A 15% dropout rate is conservative in light of our prior experience recruiting similar patients when 0% (0/40) of individuals dropped out. Total sample size is estimated to be 72 (36 for each of two groups) plus 11 (15% dropout) for a total of 84 subjects.

STATISTICAL ANALYSIS:

The incidence of thermal injury to the skin (dichotomous variable) in the groups that had unbundled or bundled camera/active electrode cords will be compared using the Fischer's exact chi squared test.