Collecting And Measuring Wound Exudate Biochemical Mediators In Surgical Wounds

The On-Q pain buster system has been developed for precise delivery of anesthetic at the surgical site. But researchers can modify this device to analyze discharge from a wound. To begin this analysis, the surgeon inserts the On-Q system into the subcutaneous layer just prior to wound closure.

After securing the On-Q to the skin with surgi strip and clear tape, the device is filled with normal saline, local anesthetic or study medication. A three-way stop cock is then incorporated into this system to allow aspiration of wound exudate at specified time points at a given time. Point one, milliliter of exudate can be aspirated using a syringe process and stored for future use or analyzed.

Hi, my name is Brendan Cavallo from the Department of Anesthesiology at Stanford University Medical Center. Today we'll be showing you a procedure for collecting and measuring wound exudate and biochemical mediators from surgical wound. We'll be using this procedure to study site specific nociceptive and inflammatory mediators from surgical wounds at regular time intervals as specified by the study protocol for following cesarean delivery.

Okay, so now let's get started. The surgical team begins the procedure by inserting the On-Q pain buster pain relief system into the subcutaneous layer just prior to wound closure. The on Q is then secured to the skin with surgi strip and clear tape dressing.

The on Q is filled with up to 100 milliliters of normal saline, local anesthetic or study medication. The system continuously delivers normal saline or local anesthetic subcutaneously into the wound at a rate of two milliliters per hour. This continuous delivery prevents the catheter from clotting and improves the reliability of the system to produce exudate samples.

Next, a three-way stop cock is incorporated into this system to allow aspiration of wound exudate at specified time points at time points specified by the protocol. We draw one milliliter of wound exudate into a polyethylene cup containing 30 microliters of proteinase inhibitor. In this case, collect exudate at one six and 24 hours after cesarean delivery.

At the same time, intervals collect 10 milliliters of blood into a green top blood collection tube containing lithium heparin. The blood specimen is then centrifuged at 3000 RPM for 10 minutes. The serum supinate is then added to 300 microliters of proteinase inhibitor.

The wound exudate is also centrifuge and the supinate removed the wound and serum samples are then placed in a standard micro centrifuge tube and stored at negative 20 degrees Celsius. When all collections are processed, the levels of biochemical mediators in both the serum and wound exudate are measured. So we've just shown you how to measure and collect wound biochemical mediators from a cesarean section wound.

But for that matter you can apply this to any other surgical wound. Although we found this technique very reliable for producing wound exudate in approximately 5%of patients, there may be some difficulty aspirating wound exudate. Techniques we utilize to improve the situation is to either change a patient's position from sitting to lying or vice versa.

We also gently push on the abdomen and the wound. You can use a one cc normal saline flush, and occasionally we have to withdraw the catheter one to two centimeters so we can produce wound exudate. So that's it.

Thanks for watching and good luck with your studies.