Introduction:
Visibility and field drainage are crucial to microvascular performance and efficiency. Traditionally this can be achieved with an assistant manual suctioning by an assistant or a gauze placed under the field, however these may not always be available or adequate. We describe a simple but novel approach to microsurgical drainage, utilizing simple capillary-action rather than suction by way of common implements present on any theatre/microvascular tray: Microsurgical Intraoperative Capillary Outflow System (MICOS).
Methods:
A laboratory experiment was conducted based on intraoperative measurements of fluid rates by connecting an infusion of normal saline into a 5x5x5cm cubic container, with moist packs and raytecs draining the container to recreate the capillary-action drainage system. Alligator clips were secured into the well with tips at a pre-set height where the anastomosis was observed to have gone underwater in the operative model- these clips was connected to an electric circuit and a light, which turned on to indicate when the threshold volume was met. This was run over several infusion rates over 30mins, both with continuous infusions and staggered boluses, measuring outcomes of residual volume in container, volume drained and time until line reached.
Results:
The underwater rate was defined as 5mm as based on the operative model. With continuous rates of 30ml/hr, 40ml/hr the threshold was not reached; at 70ml/hr the threshold was met at 15mins. With 5-minutely bolus rates of 2.5ml (30ml/hr), the threshold was not met; with 5-minutely bolus rates of 3.33ml (40ml/hr) and 4.2ml (50ml/hr) the threshold was met at 21 and 16mins respectively.
Discussion and conclusions:
Compared to the intraoperative measurement of heparinized 32ml per hour, the MICOS comfortably drains equivalent rates. This system represents a simple but accessible microsurgical adjunct, tolerating flow rates present in most clinical scenarios, as validated through our laboratory model.