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Title: Tissue fusion for bowel anastomosis
Author: Arya, Shobhit
ISNI:       0000 0004 7232 6237
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2016
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Anastomosis is the critical step in restoring gastrointestinal continuity following bowel resection and has traditionally been accomplished using suture and stapling techniques. However, both technologies can be associated with complications and are particularly difficult to perform in the laparoscopic environment. As a result there has been an increasing interest in developing novel tools and techniques which would permit safe and reliable intestinal anastomoses to be performed whilst minimising potential complications. In recent years, advanced bipolar radiofrequency (RF) energy powered devices, developed to enable more consistent vascular haemostasis, have been proposed as an alternative method for anastomotic construction and is the basis for the research presented. This thesis investigates: (i) the parameters required to form bowel seals with sufficient mechanical strength to withstand physiological pressures; (ii) methods for monitoring the viability of seals and (iii) the ability to construct functional radiofrequency induced small bowel anastomoses. The role of varying electrical parameters and compressive pressures has been investigated and characterised both in vitro and in vivo. Mucosa-to-mucosa and serosa-to-serosa small bowel seals were formed using both commercial and prototype applicator devices powered by a research based electrical generator and bespoke programmable algorithms. The mechanical strength of bowel seals was assessed through ex vivo burst pressure measurements. This demonstrated seals to be capable of withstanding physiological luminal pressures (>25mmHg) before rupturing. Tissue effects of fusion have been examined microscopically through histological assessment. The viability of fused tissue in vivo was determined utilising a multispectral imaging (MSI) system, which measured tissue oxygenation in the peri-fusion areas and allowed for the calculation of relative concentrations of oxy- and deoxyhaemoglobin and hence, overall bowel oxygen saturation (SaO2). The results of these monitoring tools have suggested that the tissue remains viable in the short term using a specific combination of electrical and mechanical parameters. These ex vivo and acute in vivo findings were applied to construct a series of chronic porcine anastomoses, where animals were recovered for a median of seven days, to compare the macro- and microscopic effects of the novel and gold standard techniques. Fifteen small bowel anastomoses were formed using a commercial and prototype radiofrequency sealer in individual animals. In addition five hand-sewn end-to-end and five stapled side-to-side anastomoses were also constructed in individual animals. Three animals in the radiofrequency anastomosis group were terminated early due to clinical evidence of anastomotic leak. Microscopically, the fused bowel showed evidence of healing at the mucosal and sub-mucosal collagen levels, which was comparable to findings using the gold standard methods. The studies performed demonstrate a method for the formation and assessment of radiofrequency induced bowel fusion and confirm its potential to be ultimately used for both bowel resection and anastomosis.
Supervisor: Hanna, George Sponsor: National Institute for Health Research
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral