New burst test method for comparing strengths of blood vessel repairs

Biomechanical comparison of microvascular anastomoses prepared by various suturing techniques

INTRODUCTION

The biomechanical properties of small vessels and microvascular anastomoses have not been studied completely yet. However, in case of vascular injury and various microsurgical reconstructive procedures a safe anastomosis is essential. Quick and reliable tests are needed to test various anastomoses in research and in teaching courses as well for quality control and proper feedback. We aimed to compare selected biomechanical properties of the simple interrupted, the continuous suture and the modified Lauritzen's sleeve-technique.

MATERIALS AND METHODS

Sixty femoral arteries from chicken thigh biopreparates and 12 abdominal aortas from rats were used in this study. In case of the pressure resistance test the groups were: the simple interrupted, the continuous suture and the modified Lauritzen's sleeve-technique. The tensile-strength, elongation and elasticity measurement groups were the simple interrupted and continuous sutures with 8 and 12 stitches. Furthermore the suture materials in various conditions (simple thread, knotted threads, stitch with intact and damaged threads) were also compared. The tensile-strength and the pressure probe devices were custom made in cooperation with the Faculty of Informatics.

RESULTS

The average diameter of the chicken femoral arteries was 3.25±0.38 mm. The sleeve-technique showed the biggest pressure drop (56±16.41 mmHg), however, it was the fastest method. The tensile-strength of simple interrupted suture was 4.55±0.7 Newton (N), being lower than of the intact vessel (6.8 ± 1.4 N). The tensile-strength did not differ significantly between the 12-stitch simple interrupted and continuous sutures, however, the latter was stronger. The anastomoses made on thread model were significantly stronger than the ones on vessels.

CONCLUSION

The main variables were the number of stitches and the strength of the vessel. The pressure drop was not correlated with the stitch number. One incorrect stitch can dramatically increase the leakage. Although the sleeve-technique is quick to be performed, it cannot withstand high pressure. The suture material itself is far stronger then the vessel. The vessel tensile strength was decreased in the anastomoses. For the given vessel diameter more than 8 stitches should be used.

Simulation training improves resident performance in hand-sewn vascular and bowel anastomoses

BACKGROUND

Surgical training has recently emphasized simulation-based training of core surgical skills and tasks such as bowel and vascular anastomoses. This may increase efficiency of training within the operating room. Objective data regarding the effectiveness of instruction or monitoring progress in simulating vascular and bowel anastomoses are lacking. The aim of this study is to provide subjective and objective assessments of simulation-based training among residents in hand-sewn vascular and bowel anastomoses.

METHODS

Residents received vascular and bowel anastomoses training. Each resident fashioned anastomoses on both cadaveric saphenous veins and small bowel. The residents repeated the anastomoses 1 week later. Performances were assessed subjectively and objectively by questionnaire, operative time, objective structured assessment of technical skills (OSATS) score, and leak pressures of the finished anastomosis.

RESULTS

Of 14 residents, 12 felt more confident with bowel anastomoses after the laboratory session, and 10 were more confident with vascular anastomoses. For vascular anastomoses, the operating time decreased (15.4 vs 14.2 minutes, p = 0.3), OSATS scores improved (14.9 vs 15.6, p = 0.15), and leak pressures improved (38.9 vs 71.8psi, p = 0.001) from the first to the second workshop. For bowel anastomoses, the operating time decreased (23 vs 18 minutes, p < 0.001), OSATS scores improved (12.9 vs 14.4, p < 0.001), and leak pressures improved (17.7 vs 26.9psi, p < 0.001).

DISCUSSION

After simulation-based training, residents performed vascular and bowel anastomoses more adeptly, quickly, and with a higher quality end product. Laboratory training can effectively improve residents' ability to perform anastomoses, which may result in increased efficiency of teaching in the operating room.

Oroxylin a, but not vasopressin, ameliorates cardiac dysfunction of endotoxemic rats

The mortality in septic patients with myocardial dysfunction is higher than those without it. Beneficial effects of flavonoid oroxylin A (Oro-A) on endotoxemic hearts were evaluated and compared with that of arginine vasopressin (AVP) which is used to reverse hypotension in septic patients. Endotoxemia in rats was induced by one-injection of lipopolysaccharides (LPS, 10 mg/kg, i.p.), and hearts were isolated 5-hrs or 16-hrs later. Isolated hearts with constant-pressure or constant-flow mode were examined by Langendorff technique. Rate and force of contractions of isolated atrial and ventricular strips were examined by tissue myography. Isolated endotoxemic hearts were characterized by decreased or increased coronary flow (CF) in LPS-treated-for-5hr and LPS-treated-for-16-hr groups, respectively, with decreased inotropy in both groups. Oro-A-perfusion ameliorated while AVP-perfusion worsened the decreased CF and inotropy in both preparations. Oro-A and AVP, however, did not affect diminished force or rate of contraction of atrial and ventricular strips of endotoxemic hearts. Oro-A-induced CF increase was not affected following coronary endothelium-denudation with saponin. These results suggest that Oro-A ameliorates LPS-depressed cardiac functions by increasing CF, leading to positive inotropy. In contrast, AVP aggravates cardiac dysfunction by decreasing CF. Oro-A is a potentially useful candidate for treating endotoxemia complicated with myocardial dysfunction.

Rabbit aneurysm model mediated by the application of elastase

The concentrations and application methods of elastase in the rabbit aneurysm model were optimized to control the initiation of aneurysms and to cause rupture in a stepwise, controlled fashion. The common carotid artery of male Japanese albino rabbits was exposed. No aneurysm was generated if the adventitia was not dissected. After gentle removal of the adventitia, a two-fold dilution series of elastase was applied to the lesion and observed over a period of 2 hours. Various stages of aneurysmal lesions, from spindle-shaped enlargement to rupture, were produced in proportion to the elastase concentration. Application of elastase stock solution (5 U/mg of type I porcine pancreatic elastase) resulted in rupture within 30 minutes in all six animals. Elastase 1:2 solutions caused oozing in all animals, but subsequent rupture in only three of six animals. Histological examination found serious destruction of the internal elastic lamina and media, with expansion of the very thin wall. Elastase 1:4 to 1:16 solutions caused spindle-like distention of the entire artery and the development of tortuosity at the lesion. Elastase 1:32 or weaker solutions caused only localized dilatations. Overall, the destruction of the tunica media became less severe with decreased elastase concentration. Furthermore, the bursting pressure of the aneurysms decreased with increasing elastase concentrations. In particular, aneurysms produced by the elastase 1:2 solution ruptured at less than 150 mmHg, whereas aneurysms induced by the elastase 1:4 or weaker solutions did not rupture within the physiological range of blood pressure. The present aneurysm model requires shorter preparation time and enables accurate control of aneurysm development and rupture.

Vessel Sealing Using a Pulsed Bipolar System and Open Forceps

We evaluated the vessel-sealing ability of one application of a pulsed plasma kinetic (PK) electrosurgical device on skeletonized vessels up to 7 mm in diameter to withstand sustained pressure of 300 mm Hg using bench and animal models. Forty-six porcine specimens and 66 abattoir vessels (112 total) were pressure tested after sealing with a pulsed PK system. Of these, 108 (96%) met the criterion of 300 mm Hg pressure held for 10 seconds without leaking. The PK system open forceps effectively closes vessels and maintains closure at a pressure level sufficient for clinical use. The device is more effective than clips, sutures, and staples.

A comparison by burst testing of three types of vascular anastomosis

A new in vivo test for burst strength of arterial anastomoses was tested in 40 rats. Twelve had a severed right femoral artery reanastomosed by the traditional nine-suture technique. In a second group of 12, a modified telescoping sleeve method of reanastomosis was used. In a third group of 12, a laser-assisted anastomosis using four stay sutures was performed. Four rats had sham procedures. Immediately after reanastomosis three vessels from each group plus all four sham surgical vessels were subjected to burst testing. These tests were performed again on the repaired vessels at 1 week, 1 month, and 2 months. All the vessels were patent at burst testing. All repairs held at all times to greater than 160 mm mean arterial pressure. The four-suture telescopic anastomosis technique was consistently strongest over time, but all techniques showed adequate strength at all time intervals.