COVER STORY
only eight patients so far, they’ve already detected two early flap failures. One case involved a complicated surgery to reconstruct the patient’s jaw using muscle and bone from his leg. Such surgeries usually take about eight hours, but that one stretched to more than 14 hours because of other medical Method that measures GLUCOSE AND LACTATE levels in problems. In that case, the lactate/glucose tissues helps improve reconstructive surgery outcomes ratio continued to climb even after the flap was reconnected in its new location. “They expected a large amount of blood TISSUE RECONSTRUCTION is commonly published (Anal. Bioanal. Chem., DOI: to wash through the tissue and for the needed to repair damage after certain types 10.1007/s00216-013-6770-z). level to come back to normal,” Rogers told of surgery, such as breast reconstruction To use the method, surgeons insert a C&EN. “We didn’t see any change.” after a mastectomy. Other examples with microdialysis probe into the flap before When the surgeons checked the flap, significant implications for quality of life they detach the tissue from its original they saw that the blood vessels were coninclude facial reconstruction after cancer location. Rogers, who is in the operating gested and the flap was tense and pale, typisurgery or trauma surgery. room during the procedure, electrochemical signs of a blood clot. When the surgeons The tissue for such rebuilding efforts cally measures glucose and lactate in the reopened the tissue, they found that it was usually comes from another part of the microdialysis fluid. riddled with blood clots. They cleared the patient’s body, such as the abdomen or “We were insistent about putting the clots using a clot-busting drug and successan arm or a leg. In a procedure fully reattached the blood vessels. called free-flap surgery, surgeons Rogers continued to monitor remove skin, muscle, and somethe patient for 10 hours in the times bone, with the accompanyintensive care unit. During that ing blood vessels, from one place time, the flap didn’t fail, but the and reconnect them in another. lactate/glucose ratio increased But the operations are not greatly. The flap failed a secalways successful. Up to about ond time a few days later, after 9% of free flaps fail on the first they had ceased microdialysis attempt. The failure rate can be monitoring. It was successfully even higher for second attempts. salvaged again, only to permaPart of the problem is that the nently fail about a week after conventional ways of detectsurgery. Brennan later detering failure—checking the color, mined that the patient had an temperature, and texture of the tissue—are probe into the flap early,” Boutelle KEEPING TABS underlying disorder that caused A microdialysis subjective, and signs of a healthy or unsaid. That way, the surgical team blood clot formation and vessel probe (inserted healthy flap are hard to discern. The probknows the patient’s basal levels destruction. at left) monitors lem is particularly true for so-called buried of the markers, and the patient “This is a fantastic technique tissue removed flaps that are totally hidden from view. acts as his or her own control, he from a patient’s that, unlike conventional microforearm for use Martyn G. Boutelle and coworkers at explained. dialysis, tells us what is going on in a free-flap Imperial College London are developing a in the flap in real time,” Brennan reconstructive method to give surgeons accurate informaAFTER THE FLAP is detached said. Conventional microdialysis surgery. tion about flap health in real time, during from its blood supply, the only can take more than an hour to the operation and recovery. Boutelle’s blood available is what remains in collect a sample and additional team, especially postdoc Michelle L. Rogthe flap vasculature. Glucose levels time to analyze it and return the ers, has developed a technique called reveal whether this blood can still feed the results. The rapid sampling method “has rapid-sampling microdialysis for monitorcells. High lactate wlevels signal that cells huge potential for future care of our paing molecules key to tissue survival. In mihave depleted oxygen in the blood and have tients and for understanding the changes crodialysis, small molecules such as blood resorted to anaerobic respiration, which that occur at a metabolic level during the sugars from the extracellular space in the will occur naturally the longer the flap is harvesting and rejoining of free flaps.” tissue diffuse across a membrane into a isolated from a blood supply. The technique is still in its early days as a fluid stream, which carries them away for The lactate/glucose ratio is more inforsurgical tool. “It relies a lot on the goodwill analysis. mative than measurement of either molof the clinical teams,” Boutelle said. It’s got In collaboration with Peter A. Brennan, ecule alone. The ratio typically climbs durto be the lead surgeon’s project as well, he a head and neck surgeon at Queen Alexing surgery as cells deplete glucose and proadded, to make sure everybody else is on andra Hospital, in Portsmouth, England, duce lactate. Too high a ratio can warn of board. Moving forward, the team plans to the team has applied the technology in the critical depletion of nutrients in the blood, monitor a larger cohort of patients to prove operating room. At Pittcon, Boutelle deor ischemia, leading to tissue damage. that the method can make a difference in scribed their work, which was also recently Although the researchers have monitored clinical outcomes.—CELIA ARNAUD MARTYN BOUTELLE
MICRODIALYSIS UNDER THE KNIFE
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APRIL 15, 2013
