Laser-assisted demucosalized gastrocystoplasty with autoaugmentation in a canine model

Laser tissue soldering of the gastrointestinal tract: A systematic review LTS of the gastrointestinal tract

Background

Laser Tissue Soldering (LTS) is a promising tissue bonding technique in which a solder is applied between the tissues and then irradiated by laser, causing it to solidify and form links with the tissue.

Methods

A comprehensive systematic review summarizing the state of research of LTS in the gastrointestinal tract.

Results

Most studies were conducted on large animal tissues, using liquid proteinaceous solder, and irradiated by a continuous wave laser at 808 nm. LTS can provide better sealing and burst pressure than conventional methods. The application of LTS on top of or in addition to sutures showed an impressive increase in burst pressures. LTS may decrease the inflammatory and foreign body reaction caused by sutures.

Conclusions

LTS has strong potential to be applied in a clinical setting in leak prevention and in closure of gastrointestinal structures as an adjunct or additional anastomotic technology, decreasing leak rates, morbidity, and mortality.

Laser tissue soldering: applications in the genitourinary system

Within the past 25 years, lasers have transitioned from merely destructive or ablative tools to those with reconstructive uses. It has been shown that the application of laser thermal energy to tissue will result in welding of the approximated areas. Furthermore, the addition of protein solder and chromophores (tissue soldering) has increased wound tensile strength while decreasing peripheral tissue damage. Laboratory studies have demonstrated application of laser tissue soldering to virtually all components of the genitourinary system. Increasing human experience in recent years has reinforced the success of this technique.

Concentrated autologous plasma protein: a biochemically neutral solder for tissue welding

BACKGROUND AND OBJECTIVE

Xenographic or allographic serum protein solders used for laser welding may have immunologic and/or pathogenic complications. The objective of these studies was to develop a safe, autologous solder.

STUDY DESIGN/MATERIALS AND METHODS

Five methods of preparing concentrated autologous plasma protein solder (CAPPS) were evaluated. Next, the CAPPS was evaluated via (1) thermal denaturation studies using differential scanning calorimetry, (2) tissue welding studies to characterize both acute and healing properties.

RESULTS

The optimal concentration method to produce CAPPS rapidly was a dialysis method using chemical (osmotic) forces. The CAPPS showed similar denaturation profiles to serum albumin (SA) solders. Acutely, CAPPS provided comparable breaking strengths to SA solders. At 7 days, there was no significant difference in breaking strength or histology between 50% human SA solder and CAPPS (using a porcine skin model).

CONCLUSIONS

These studies demonstrate that the CAPPS system provides acceptable acute and chronic properties for laser welding.

Hand-assisted demucosalized gastrocystoplasty comparing different tissue closure methods

OBJECTIVES

To perform experiments to determine whether a new tissue sealant (SynthaSeal) could be an alternative for suture closure in minimally invasive bladder autoaugmentation gastrocystoplasty using demucosalized stomach. Alternative methods to suture closure for tissue approximation such as laser tissue welding and fibrin glue have been reported.

METHODS

Minimally invasive autoaugmentation gastrocystoplasty with demucosalized stomach was performed on 14 female mongrel dogs. Two dogs were used to refine the technique. The remaining dogs were assigned to a suture group (n = 6) or a SynthaSeal group (n = 6). Anastomoses were performed using either SynthaSeal or suture. The in vivo bladder volumes and pressures of the groups were measured before and after gastrocystoplasty. The animals were studied on day 14. Samples of the anastomotic area were taken to measure the tensile strength and stress. Histologic analysis was conducted to assess tissue healing. The anastomotic time was recorded for each group.

RESULTS

The tensile strength of the anastomoses in the SynthaSeal group was significantly increased (9.99 +/- 1.14 Newtons) compared with the suture group (5.66 +/- 0.97 Newtons) (P <0.05). The breaking stress comparisons and anastomosis times were equivalent between the two groups. The histologic evaluation revealed minor tissue devitalization and a normal inflammatory response in both groups.

CONCLUSIONS

Minimally invasive gastrocystoplasty using demucosalized stomach can be successfully performed with SynthaSeal tissue sealant. This may provide a reliable alternative to suture closure.

Laser tissue welding: a biotechnological advance for the future

Laser tissue welding as well as other alternative methods of closure will play a more important role in surgical specialties as laparoscopic, endoscopic, and microsurgical techniques continue to develop. Laser tissue welding uses laser energy to anastomose tissues and is ideally suited for applications in which suturing and stapling is difficult. Recent advances have led to a better understanding of the mechanisms of tissue welding. Additionally, technical achievements including the introduction of protein solders and temperature-controlled feedback systems have led to the acceptance of laser tissue welding in clinical medicine. In this article, we describe the history and development of laser tissue welding and review the current and potential applications of this technology.

Differential scanning calorimetry of albumin solders: interspecies differences and fatty acid binding effects on protein denaturation

BACKGROUND AND OBJECTIVE

Understanding albumin solder denaturation is important for laser tissue soldering. Human (HSA), bovine (BSA), porcine (PSA), and canine (CSA) albumin both fatty acid containing (FAC) and fatty acid free (FAF) were evaluated by using differential scanning calorimetry (DSC).

STUDY DESIGN/MATERIALS AND METHODS

DSC was used to measure difference thermograms to determine the irreversible thermal denaturation profile for 50% albumin solutions. The denaturation transition's onset, end and peak temperatures, and enthalpy were measured.

RESULTS

All FAC species, except BSA, exhibited twin peaked endotherms. Single endotherms were observed for all FAF species and BSA-FAC. Onset and end temperatures were significantly [P < 0.001] lower for all FAF species (except BSA's end temperature). There was a 30% decrease in the denaturation enthalpy between FAF and FAC groups.

CONCLUSION

FAF albumin solders were found to denature at significantly lower temperatures, while also having a 30% reduction in enthalpy when compared with their FAC counterparts.

Welding characteristics of different albumin species with and without fatty acids

BACKGROUND AND OBJECTIVE

Albumin solders from different species have been used for laser tissue welding without a complete understanding of possible differences between them. The breaking strength of four different species of serum albumin (human, bovine, porcine, and canine), both fatty acid containing (FAC) and fatty acid free (FAF), was determined to evaluate the welding ability of each type of albumin. STUYDY DESIGN/MATERIALS AND METHODS: Acute breaking strengths were determined on canine small bowel by using 50% albumin (FAF and FAC) from human, bovine (BSA), porcine, and canine species.

RESULTS

BSA-FAC and BSA-FAF had a significantly higher (P < 0.05) breaking strength than all other groups; furthermore, BSA-FAC was significantly higher (P < 0.05) than BSA-FAF. There was no significant difference in breaking strength when FAF albumin was compared with FAC albumin from humans, pigs, or dogs.

CONCLUSION

These experimental results show that species-specific and fatty acid-specific differences exist when these albumin solders are used for laser tissue welding. This finding suggests that modifications in albumin could be used to improve results through decreased thermal damage and increased weld strength.

Lessons learned from laser tissue soldering and fibrin glue pyeloplasty in an in vivo porcine model

PURPOSE

We compared sutured pyeloplasty to 2 newer techniques of tissue anastomosis, including laser soldered pyeloplasty using a diode laser with 50% albumin solder mixed with indocyanine green and fibrin glue.

MATERIALS AND METHODS

We performed 53 pyeloplasties in 50 pigs using suture, laser or fibrin glue. In the immediate group anastomotic leak pressure was measured immediately postoperatively, and then animals were euthanized. At 1, 3 and 4 weeks postoperatively a pressure flow study at 10 cc per minute in cm. H2O was performed, and tissue was sent for histological and collagen content analysis.

RESULTS

In the immediate studies laser soldering achieved a significantly higher mean anastomotic leak pressure (50.5 +/- 15.1 cm. H2O) than sutured (17.3 +/- 5.4) or fibrin glued (3.5 +/- 1.5) repairs. In the 1, 2 and 4-week studies animals in the sutured pyeloplasty group had no complications, and all pressure flow studies except 1 were normal. However, in the laser soldered groups we observed 8 urinomas in 19 animals, and most occurred during the first part of our study. This complication was prevented by stopping urine flow at the anastomotic site at laser irradiation and by improving application of the solder. Of the 11 animals in which pressure flow studies were performed only 2 were obstructed. Of the 7 chronic fibrin glue group 4 animals had urinomas and 2 had unobstructed pressure flow studies. Histological studies and immunohistochemical staining for collagen showed no differences in collagen distribution among the 3 procedures.

CONCLUSIONS

Laser soldering and fibrin glue pyeloplasties are not superior in the long-term compared to sutured pyeloplasty. Fibrin glue in our animal model had the highest failure rate. Further improvements in the technical aspect of laser tissue welding need to be made to benefit from its theoretical advantages in minimally invasive surgery.