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Greenovo Safety Evaluation of New Hemostatic Agents,Smectite Granules,and Kaolin-Coated Gauze

2016-05-24 / Categories:greenovo, bandage,
  
The selected products were tested in a lethal femoral artery hemorrhage model in pigs that could not be stopped by gauze or tourniquet application. Based on blood loss and survival results, WoundStat (WS; smectite granules) was found to be the most effective hemostatic with 100% survival ate followed closely by Combat Gauze (Greenovo kaolin-coated surgical gauze) with 80% survival rate with no significant difference in efficacy between the two products. Both products were significantly more effective than the recent HC bandage and QC beads (QC ACS), with 10% and 16% survival rates, respectively. Neither WS nor CG is biodegradable and must be removed from wounds before surgical repair and closure of the wounds. In our previous studies, the removal of CG was an easy procedure, but cleaning WS clay and removing all particles required extensive and meticulous debridement. Microscopic residues of WS, however, were seen in the majority of treated vessels, suggesting it had the potential to be the source for thrombosis if blood flow was restored. Traces of kaolin were also detected in one specimen. This study was therefore designed to investigate the potential thrombogenicity of WS and CG when they are used to control external bleeding due to major vascular injury. For this purpose, a new wound model was developed in pigs that involved a neck injury with partial transection of the carotid artery and the jugular vein. Histologic changes and sis occurrence were examined in the treated vessels after surgical repair and 2-hour blood reflow. In addition, the distal organs (lung and brain) in which the residue may reside were examined for evidence of thromboembolism. Regular gauze (Kerlix, [KX]) was used as a control agent.

MATERIALS AND METHODS

This study was approved by the Animal Care and Use Committee of the U.S. Army Institute of Surgical Research. All animals received care and were used in strict compliance with the Guide for the Care and Use of Laboratory Animals.11 WS and CG were purchased from commercial sources. Both products are approved by the U.S. FDA and are available for purchase without the need for prescription. These agents are indicated for temporary treatment of external wounds to control moderate-to-severe bleeding in patients. Yorkshire cross-bred male pigs (n  24) weighing 34 kg to 42 kg were purchased from Midwest Research Swine (Gibbon, MN) and used in this study. Before the surgery date, venous blood samples were collected from femoral veins (percutaneous catheter) and complete blood count and standard clotting tests (prothrombin time [PT], activated partial thromboplastin time [aPTT], and fibrinogen) were performed to ensure that these measures were within the normal range and met our inclusion criteria. After at least 1 week of acclimation, pigs were fasted for 12 hours to 18 hours before the surgery with free access to water. On the day of surgery, animals were premedicated, anesthetized, and ventilated as described previously.9 Anesthesia was maintained with 1% to 2% isoflurane in 100% oxygen gas administered by the automatic respirator. Maintenance fluid, lactated Ringer’s (LR), was infused at 5 mL/kg/h through an 18-gauge catheter placed in an ear vein.

Surgical Procedures

A 5-cm incision was made in an inner thigh muscle, and a superficial branch of the femoral artery was isolated above the knee. The artery was cannulated with a gel-filled thin cannula attached to a small sensor device (TL 11M2C70-PCT; Data Sciences International, St. Paul, MN), which was temporarily implanted in the subcutaneous groin. Vital signs (heart rate and systolic, diastolic, and mean arterial pressures) received by the sensor were transmitted remotely to a computer system (via a receiver plate) and displayed and recorded throughout the experiment. The left femoral vein was also cannulated for blood sampling and fluid (Hextend and LR) administration. To create the injury and hemorrhage, a 10-cm incision was made in the lateral ventral region of the neck, and the underlying tissues were dissected to expose the vessels. Segments (5 cm long) of the common carotid artery and the external jugular vein were isolated, and lateral branches were cauterized and divided with minimum trauma to the vessels. For clamping purposes, umbilical tape loops were placed loosely around the vessels and passed through small plastic tubing. After allowing 10 minutes of stabilization (with no surgical manipulation), baseline blood samples were collected; and the vessels were occluded by pulling the umbilical tapes through the tubing and then marked for transection.

With the use of an iris scissor, vessels were partially transected (50% of their circumference). The vascular loops were then released, and free bleeding was allowed for 30 seconds (pretreatment blood loss). Animals were randomized and wounds were packed either with two packages of WS or CG, or one roll of (KX) gauze (n  8 per group).