Editors' ChoiceSurgery

Eureka!!! Sewing to Moonbeams

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Science Translational Medicine  14 Sep 2011:
Vol. 3, Issue 100, pp. 100ec151
DOI: 10.1126/scitranslmed.3003170

All vascular and cardiac surgeons must master the art and science of sewing blood vessels together to create the connections known as anastomoses. The technical ability to sew very small and diseased blood vessels is a limiting factor for effective treatment in the operating room. Many a surgeon, after a difficult anastamosis, has been overheard to complain that “it was like sewing a fart to a moonbeam.” For nearly 100 years, no notable advances in this technique have been made….until now.

In this report, Chang and colleagues used a new, FDA-approved technology to reconstruct blood vessels less than 1 mm in diameter without trauma to the tissue. At one temperature, these nanoparticle-based polymers form a gel and act to prop open the blood vessel while the surgeon uses commercially available adhesives to seal and stabilize the vessel. When the anastomosis is finished, the temperature is lowered to liquefy the nanogel, allowing blood to flow normally through the artery.

The thermoreversible poloxamer 407 (P407) is a triblock of the nanoparticles polyethylene oxide (PEO) and polypropylene oxide (PPO). These poloxamers have been used clinically to treat sickle cell crisis and traumatic brain injury and for the delivery of numerous drugs. The authors took advantage of their unique phase-transition properties, which can be manipulated by altering the concentration of the polaxamer and the environmental temperature: The constituent PEO and PPO nanoparticles remained water soluble and fluid at lower temperature, but formed a cohesive gel at higher temperatures. With increasing concentrations, P407 showed a corresponding increase in the elastic modulus and a decrease in the phase transition temperature.

Chang and colleagues showed that the polymer works in vivo in a rat. There was a remarkable decrease in inflammation, an increase in the surgeon’s ability to keep the vessel open, and a significantly decreased operative time compared with traditional hand sewing. Furthermore, the nanogel method caused less damage to the inner layer of the blood vessel, and the vessels remained healthy and viable for up to one year.

This surgical advance has the potential to progress rapidly to the bedside, because all the components are already FDA approved. Nevertheless, don’t hang your hat on this technology quite yet. There are still some questions that need to be addressed: Will this work in larger blood vessels and at higher blood pressures? Are there any long-term detrimental effects on the blood vessels? Is there more bleeding with this technique? As a surgeon scientist, however, I did look out the window tonight and think I may have seen a shadow on a moonbeam that wasn’t there before.

E. I. Chang et al., Vascular anastomosis using controlled phase transitions in poloxamer gels. Nat. Med. 17, 1147–1152 (2011). [Abstract]

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