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Discussion: Vasospasm of the Flap Pedicle The Effect of 11 of the Most Often Used Vasodilating Drugs. Comparative Study in a Rat Model

585e V of a microvascular pedicle is one of the often noted explanations for flap compromise. Many drugs have been applied topically and administered parenterally as spasmolytic agents for the microvasculature in spasm with proven and anecdotal success.1–4 However, to the best of our knowledge, there appears to be a lack of any direct comparison of the efficacy of such drugs in a single study. We congratulate the authors on undertaking the enormous task of evaluating a multitude of these drugs in a combined head-tohead comparison. The authors studied not only the ability of the agents to reduce vasospasm duration, but also their overall efficacy as compared with a control group. This article brilliantly details the study, which aimed to perform this assessment of 11 commonly used spasmolytic drugs. By doing so, a somewhat dormant question in the field of microsurgery regarding pharmacologic treatment of vasospasm is revived. The authors used the groin island flap model in the rat,5 whose pedicle—the superficial epigastric vasculature—was manipulated in a standardized way to create a spasmogenic action. A longitudinal traction force was applied on the pedicle using a 15-g weight to induce vasospasm. Presumably, this model was first well established in the authors’ hands as a reproducible inducer of microvascular vasospasm. In addition, commendably, all flap dissections were performed by a single surgeon to reduce variability in surgical design, and the experimental conditions such as light, temperature, and sterility, all remained constant. Laser Doppler imaging was used to assess fluctuations in flap perfusion after the weight was applied for 5 minutes to induce vasospasm. Each drug was applied either continuously topically, beginning with weight application and ending 2 minutes after removal of the weight, or parenterally as a single dose at the beginning of weight application. Perfusion curves were recorded for a total of 30 minutes after the weight was removed. These perfusion curves were analyzed for each drug to determine vasospasm duration (a surrogate for the interval during which the flap was not perfused) and time to hyperperfusion (indicating the flap reperfusion speed). This allowed for an individual spasmolytic efficacy assessment of each drug compared with a control (traction-induced vasospasm without drug application) and direct comparisons between drugs. In addition, by using two separate time measurements, the authors were able to delineate the difference between vasospasm duration and time to hyperperfusion. In this way, the high shape variability of the perfusion curves was also corrected, as some curves had similar vasospasm duration but different time to hyperperfusion, and vice versa. Using two time parameters increased the validity of the outcomes because, by having multiple data points per drug, further differentiation between them could be performed. Another excellent element of the study was the use of an automated delineation algorithm. This provided smoother perfusion curves by removing the irregularity of the curve associated with background noise detected by the Doppler device, thereby reducing potential errors in the analysis of the curves. Although there was no