Prediction of the minimum amount of anti-adhesive agent required for entire intra-abdominal cavity using fluorescent dye

Abstract

Purpose: Studies on the appropriate amount of anti-adhesive agents for preventing postoperative adhesion are lacking. This animal study aimed to investigate the distribution of an anti-adhesive agent in the abdominal cavity and estimate the necessary amount to cover the entire cavity.

Methods: Fluorescent dye Flamma-552 was conjugated to Guardix-sol to create Guardix-Flamma, which was laparoscopically applied to the abdominal cavity of two 10-kg pigs in different amounts: 15 mL for G1 and 35 mL for G2. After 24 hours, the distribution of Guardix-Flamma was examined under the near-infrared mode of the laparoscope, and the thickness was measured in tissues from the omentum, small, and large intestine by immunohistochemistry.

Results: The average area of the abdominal cavity in 10 kg pigs was 2,755 cm2. Guardix-Flamma fluorescence was detected in the greater omentum, ascites in the pelvis, and right quadrant area in G1, whereas in G2, it was detected everywhere. On average, the total thickness of G1 and G2 were 12.68 ± 9.80 μm and 18.16 ± 15.57 μm, respectively. Guardix-Flamma thickness applied to the omentum, small, and large intestines of G2 were 1.31-, 1.45-, and 1.49-times thicker than those of G1, respectively, and were all statistically significant (P < 0.05).

Conclusion: The entire abdominal cavity of the 10 kg pig was not evenly covered with 15 mL of Guardix. Although 35 mL of Guardix is sufficient to cover the same area with an average thickness of 18 µm, further studies should evaluate the minimum thickness required for an effective anti-adhesive function.

Keywords: Adhesion; Animal experimentation; Carboxymethylcellulose sodium; Fluorescent dyes; Hyaluronic acid.

Fig. 1

Experimental day 1: application of different amounts of Guardix-Flamma solution in the intra-abdominal cavity through laparoscopic procedure and confirmation with different camera modes. The arrow indicates where the green fluorescence signal was observed in NIR mode. LUQ, left upper quadrant; LLQ, left lower quadrant; RLQ, right lower quadrant; RUQ, right upper quadrant; G1, pig 1; G2, pig 2; RGB, red green blue; NIR, near-infrared.

Fig. 2

Experimental day 2: verification of fluorescence of Guardix-Flamma under laparoscopic NIR camera. The arrow indicates where the green fluorescence signal was observed in NIR mode. LUQ, left upper quadrant; LLQ, left lower quadrant; RLQ, right lower quadrant; RUQ, right upper quadrant; G1, pig 1; G2, pig 2; RGB, red green blue; NIR, near-infrared.

Fig. 3

Measurement of the area in the intra-abdominal cavity. G1, pig 1; G2, pig 2.

Fig. 4

Measurement of Guardix-Flamma thickness using confocal microscopy. G1, pig 1; G2, pig 2.

Fig. 5

Comparison of Guardix-Flamma thickness between G1 (pig 1) and G2 (pig 2). Student t-test; *P<0.05, **P<0.01.