Monday, December 4, 2023
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The success of trauma systems and practice protocols has convinced trauma surgeons of the value of evidence-based surgery. The importance of proper evaluation before using new methodologies can be highlighted by the recent experience with military antishock trousers, in which enormous resources were spent on a modality that was later proved to be ineffective.
At the 90th Clinical Congress of the American College of Surgeons in New Orleans, Louisiana, this past October, the Committee on Emerging Surgical Technology organized a session entitled "Cutting-Edge Trauma Surgery -- What's Proven, What's Not?" to update the audience on advances in hemostasis, closure of the abdomen, noninvasive monitoring of resuscitation, and advances in thoracic trauma. Dr. George Velmahos from Los Angeles, California, moderated the session.
Hasan Alam, MD, FACS, from Bethesda, Maryland, described 3 new products for local hemostasis being actively evaluated by the US Department of Defense, 2 of which have already been used in Iraq. The military is especially interested in hemostasis, as hemorrhage is the number 1 cause of death in penetrating trauma, both in battlefield and civilian injuries.[1]
A dressing that uses positively charged chitosan molecules (Hemcon), which are derived from shrimp, is currently available as 4-in x 4-in pads. The molecules absorb negatively charged red blood cells (RBCs). As the cells are absorbed by the bandage, they create a hemostatic plug over the wound.
Chitosan has been shown to have good early efficacy. In a porcine model of liver and femoral artery injury, chitosan increased survivability by 70%.[2] In other porcine studies, however, it was found to have an almost 100% failure rate after 2 hours, as the RBCs overrun the chitosan molecules.[2,3] Hemcon received US Food and Drug Administration (FDA) approval in 2002. Army medics have used Hemcon in the field during Operation Iraqi Freedom, successfully controlling hemorrhage in soldiers long enough to transport them to forward surgical teams.
The following are advantages of chitosan:
The following are disadvantages of chitosan:
Zeolite (QuickClot) is an FDA-approved agent carried by individual marines deployed in Iraq, according to Dr. Alam. This material, which has the consistency of kitty litter, is poured onto the wound. It causes absorption of water, concentrating clotting factors and promoting coagulation. In a swine groin injury model, it improved survivability by 100% over controls.[4,5]
Zeolite is particularly useful at sites where dressings or temporary tourniquets cannot be applied (eg, the groin). It does, however, produce an exothermic reaction, generating temperatures up to 60°C. The intensity of this reaction is correlated to the amount of blood in the wound at the time of application. Hydrating the zeolite preparation decreased the amount of heat generated but dropped its efficacy down to only 60%.[6]
The following are advantages of zeolite:
The following are disadvantages:
A dressing of dry fibrin sealant (American Red Cross dressing) is also produced in a 4-in x 4-in configuration. It is extremely effective, with animal injury models showing improved survival in grade 5 liver injuries and efficacy that rivals primary repair with sutures in an aortic injury punch model.[7] This dressing is derived from blood products, and up to 40 U of blood are required to deliver the components for 1 batch. Recombinant DNA technology may aid in its development, but presently its cost is prohibitive. It is also difficult to apply and is not yet FDA-approved.
Thomas Scalea, MD, FACS, from Baltimore, Maryland, described his center's recent experiences with recombinant factor VIIa (rFVIIa). rFVIIa triggers coagulation by combining with exposed tissue factor. Furthermore, it amplifies coagulation by interacting with activated platelets. Finally, it reduces fibrinolysis by inhibition of plasmin. rFVIIa has been used in cardiac surgery, liver transplantation, trauma, and hemolytic uremic syndrome.[8-10] A recent randomized, prospective trial in patients undergoing radical prostatectomy showed that patients treated with rFVIIa preoperatively had a significant reduction in blood loss, transfusion need, and operative time.[11]
At the University of Maryland Medical System (UMMS), Baltimore, patients have received rFVIIa since 2001 for indications that have included acute traumatic hemorrhage, severe traumatic brain injury, warfarin reversal, factor VII deficiency, and coagulopathy in the intensive care unit (ICU). In a series of 80 patients treated with rFVIIa at UMMS, those with active bleeding were treated with 100 mcg; patients with factor deficiency, warfarin reversal, and traumatic brain injury received 50-mcg doses. Survival rates were 54% in patients with factor VII deficiency, 43% in patients with hemorrhagic shock, 25% in brain-injured patients, and 75% in ICU patients with coagulopathy. The overall survival rate was 45%.[12] The cost of the drug was about $6500 at UMMS.
Nonresponders to therapy had lower platelet counts and much higher base deficits. Responders used much less blood products after receiving rFVIIa. In all patients, prothrombin time normalized at least briefly.[12] Dr. Scalea remarked that treatment should be initiated promptly, as rFVIIa was more effective in patients who had received 15 U of packed RBC vs those who had received 26 U. He and his colleagues also found that patients with prothrombin times > 17 seconds and Revised Trauma Scores > 5 were not likely to respond.
Contrary to popular belief, Dr. Scalea said, factor VIIa does not "clot off everything." In the UMMS series of 80 patients, none of the survivors experienced deep venous thrombosis, vascular graft thrombosis, myocardial infarction, or stroke. Three patients with mesenteric injuries developed bowel infarctions; all died subsequently.[12]
There is a possibility that the use of rFVIIa may increase the incidence of multiple organ failure (MOF).[13] Emerging data from Europe suggest that even though factor VIIa did reduce transfusion requirements in severely injured patients, it did not decrease the incidence of MOF, ICU length of stay, or even mortality.
It appears that factor VIIa may work best in patients with acute hemorrhage, if given before systemic tissue hypoperfusion and microvascular thrombosis set the stage for MOF.
The principal of damage-control surgery and the practice of leaving the abdomen open have saved many lives, as they help to get the patients off the operating table (a continuing stress phase) and into the ICU (resuscitative phase) before the "triangle of death" -- hypothermia, coagulopathy, and acidosis -- sets in.
Michael Chang, MD, FACS, of Winston-Salem, North Carolina, explained that in trauma patients, bowel edema due to ischemia-reperfusion injury, retroperitoneal swelling due to hematomas, and pelvic fractures are among the reasons why the abdomen is left open. In general surgery patients, indications include dirty wounds and ruptured abdominal aortic aneurysms. "Leaving the abdomen open is never a sign of weakness," he said.
The open abdomen also helps to prevent abdominal compartment syndrome, which is associated with cardiovascular collapse due to decreased preload and increased afterload, pulmonary failure due to decreased compliance and compression atelectasis, and renal failure due to the increased renal venous compression pressures in the abdominal cavity.
Whenever abdominal compartment syndrome is considered, abdominal perfusion pressure (mean arterial pressure minus intra-abdominal pressure) must be taken into account. In an average individual, an abdominal perfusion pressure of approximately 50 mm Hg is required for adequate perfusion of the viscera. Thus, in hypotensive patients, compartment syndrome can develop with just marginally high intra-abdominal pressure (eg, 15-20 mm Hg). While patients are in an inflammatory stage requiring massive resuscitation, and have or are suspected to have a high intra-abdominal pressure, their abdomens should be left open. Once the patient enters a compensatory anti-inflammatory state, fluid is mobilized; the need for a larger intra-abdominal volume is decreased; and the abdomen can be closed.
Surgeons can choose from among temporary and semipermanent options for closing the open abdomen. Temporary options include (1) Bogota bag closure[14] with drains beneath, (2) antibiotic suture with polyglactic acid (Vicryl) or permanent mesh with drains on top, (3) genitourinary fluid bag closure, and (4) towel clip closure (does not decrease intra-abdominal pressure).
Dr. Chang also described a method of temporarily closing the abdomen, called the vacuum pack system,[15] in which a bowel bag is laid out, perforated, and then placed over the solid and hollow viscera enclosing them beneath the fascia. At the facial level, towels are placed, above which drains are inserted and then an occlusive, plastic drape is applied. This approach allows for quantifiable fluid loss and release of intra-abdominal pressure. It can be quickly used, as no suturing is involved. This is usually used as a temporizing measure until the fascia is closed in 7-9 days.
Semipermanent options include Vicryl mesh with a split-thickness skin graft; reconstruction is eventually required.
Options for permanent closure include 2 methods.
A variation of the temporary vacuum pack system described above can be used for delayed primary closure. This approach avoids the ventral hernia associated with mesh in a semipermanent closure. Miller and colleagues,[16] at Wake Forest University, Winston-Salem, indicate that this method is used when the patient has been resuscitated over the course of several days with the vacuum pack open-abdomen dressing and is in a state of fluid mobilization. In the vacuum-assisted facial closure (VAFC) technique, a similar bowel bag is perforated and placed over the viscera, but at the facial level a VAC sponge is placed with its suction catheter on top. The skin is then approximated with running sutures and the occlusive dressing is applied. Every 3-5 days, the sponges are narrowed and the edges of the abdominal wall are brought closer together as the bowel becomes less edematous, until the fascia can be closed. In Dr. Chang's series, time to closure was 9-21 days and no delayed fistulas developed.
Bioprosthetic grafts for closure include Alloderm (acellular human tissue matrix, derived from cadaver skin) and Surgisys (acellular pig intestinal mucosa). These products are sutured to the facial edges and lay down matrices that may be neovascularized and populated with fibroblasts. This host integration allows them to perform like native tissue and to be used in infected wounds. The team at Wake Forest has been using Alloderm with a VAC dressing in order to close large, complicated abdominal wounds. The Alloderm develops a layer of granulation tissue, with the VAC system accelerating the healing process.
Stephen M. Cohn, MD, FACS, from San Antonio, Texas, discussed the potential of near-infrared spectroscopy (NIR) as a noninvasive technique for determining a patient's resuscitation needs. NIR measures the oxygen-saturation state of tissue (percentage of StO2) by evaluating the absorption of infrared light.
In initial animal studies, NIR findings were closely correlated with heart rate, blood pressure, and blood loss.[17] Some studies have also shown it to be superior to invasive sampling measurements, such as mixed venous oxygen saturation (SVO2), base deficit, and lactate.[18] The ability of NIR to determine the severity of shock and the degree of resuscitation in humans is still being studied. As a first step, a thenar oxygen saturation of 86% ± 6 has been identified as a normal range for humans in a nonrandomized observational study.[19] NIR has also been valuable in evaluating compartment syndrome in animal models and in human patients.[20]
This technology has tremendous potential as a noninvasive, continuous monitoring device for hypoperfusion, but larger clinical studies are needed to validate its usefulness.
Peter Rhee, MD, FACS, from Los Angeles, California, described the application of damage-control principles to the thoracic cavity. The thoracic cavity is a low-pressure environment with abundant tissue thromboplastin, which explains why most nongreat vessel hemorrhage stops on its own. Even in penetrating trauma, urgent thoracotomy is required in only 15% to 20% of cases. Most patients can be managed with a chest tube. It is important, however, that blood loss via chest tubes is quantified and retransfused as much as possible.
The most important determinate for the necessity of an operation is whether th patient is still bleeding. If, initially, the patient puts out 1500 cc of blood from the chest tube, the patient is a surgical candidate. If, however, the bleeding stops after 1500 cc and all the evacuated blood is clotted and dark blue, then perhaps one can wait. On the other hand, Dr. Rhee said that if the patient bled 1200 cc initially and bright red blood continues to pour from the chest tubes, the operating room is the only option.
To avoid the previously described triangle of death, bleeding must be controlled. With damage-control thoracotomy, once bleeding is controlled, the chest wall need not be closed. If the patient is unstable, skin closure will suffice.
Various strategies can be applied for hemorrhage control, including use of zeolite, if available, and factor VIIa. Surgical maneuvers to control major bleeding include hilar cross-clamping and lung torsion (twisting the entire lung and hilum after taking down the inferior pulmonary ligament).
Staplers should be used if a pneumonectomy must be performed. Such radical operations have terrible long-term results, however, primarily because the decision is made after much time has been spent on the table. An alternative is to just clamp the hilum and come back the next day, Dr. Rhee said. Also, he said, many of these patients die of right heart failure; therefore, unlike typical trauma patients, patients with major pulmonary operations must be kept somewhat volume-depleted.
Studies show that as the complexity of the thoracic operation increases, so does mortality.[21] Lung-sparing techniques have improved outcomes vs anatomic resection. One such technique, tractotomy, is especially useful in penetrating trauma. Staplers are fired on 2 sides of the penetrating trauma tract, isolating it. The tract is then opened, and bleeding vessels are sutured or otherwise controlled with an argon beam or even fibrin glue.
The use of seat belts has dramatically changed the epidemiology of intrathoracic aortic injuries, allowing far more patients to present to the emergency department in stable condition. As a result, it has become possible to use endovascular stents in traumatic aortic injuries. Riyad Karmy-Jones, MD, FACS, from Seattle, Washington, stated that patients undergoing open repair for such injuries had mortality rates of 5% to 28%, as compared with 6% to 10% with endovascular repair. Length of stay in endovascular stent-graft (ESVG) placement patients can be dramatically shorter in patients with isolated injuries, but overall, the length of stay shows no difference, as it is related more to injury severity than to type of repair.
Because there is no aortic cross-clamping with EVSG, the risk of paralysis is markedly reduced. Paralysis occurs at a rate of 3% to 26% in some series in patients treated with open repair, but this rate falls to 0% in patients treated with endografts. Overall, use of EVSG is associated with a marked reduction in risks of paralysis, morbidity, and mortality in patients with isolated chest injuries.
Technical considerations for placement of an EVSG include femoral diameter, left subclavian artery position, distance to insertion site, and most importantly the angle of the aortic arch. This curvature can cause foreshortening of the graft and is the most significant problem with graft placement. In the United States, only a few centers have dedicated thoracic aortic grafts; most centers are compelled to use abdominal aortic graft extenders. These nonanatomic grafts are not only more technically difficult to use but also are prone to leaks and migration. European series with dedicated thoracic aortic endovascular stents have shown excellent results.
The future of EVSG in thoracic trauma remains bright, as more and more surgeons become adept at this technique and thoracic aortic grafts become available.
