Surgical Technique and the Surgical Treatment of Wound Infection

Surgical Technique and the Surgical Treatment of Wound Infection

4:20 pm Surgical Technique and the Surgical Treatment of Wound Infection Warren Gamer, MD Suturing Technique There will be a slide presentation showi...

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4:20 pm

Surgical Technique and the Surgical Treatment of Wound Infection Warren Gamer, MD Suturing Technique There will be a slide presentation showing how to best place sutures for single-layer skin closure and doublelayer skin closure.

Knots and When to Use Them The best and most secure way to tie sutures is to use two-handed square knots. Many times other knots have advantages. When tying under tension, use a surgeon's knot for the first knot (two throws instead of one) or tie a slip knot with the second throw rather than a square knot. Instrument ties are rapid and use much less suture. Utilize them when the closure is not under tension and multiple knots are being tied. Two-Layer Closures A two-layer closure is beneficial in many circumstances, such as when a device or foreign body is placed beneath the skin and a secure closure is important to prevent exposure, or when a better appearance is important (in the case of a young patient with an incision in an exposed body region). This allows removal of the external suture before cross-hatching or suture tracks can develop. The first suture is buried (inside-out, outside-in) in the tissue, which places the knot in the subcutaneous plane below the dermis. A slowly dissolving absorbable suture such as PDS or Dexon is most often used. A second suture is placed externally (outside-in, insideout) with an external knot. Nylon is the usual choice for this suture. Prolene can be used in hairy regions. In many cases I use an absorbable suture such as Monocryl or fast-absorbing Chromic, eliminating the need for suture removal, which makes patients happy and gives you less work. Dressings I cover all incisions with a light coating of antibiotic ointment and a light dressing of silk tape. Large occlusive dressings are seldom necessary or helpful. When compression is needed, use fluffed Kerlex and a wraparound Kling dressing. Foam tape can tear off epidermis when it is removed and should not be routinely used. Any dressing can be removed at 48 hours and the wound cleaned with soap and water. I tell my patients to remove any dried blood, exudate or other material with soap, water, and a washcloth. Then they should coat the incision with antibiotic ointment twice daily until healed. A dressing is need only to protect clothing from the antibiotic ointment or for wound problems.

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Treatment Skin InjUry A possible complication of skin dissection and elevation is skin necrosis, which can occur as a full- or partial-

thickness injury. Both require treatment for optimal results. Superficial skin loss is more common. The epidermis is a cellular, metabolically active tissue. This means it requires higher levels of blood flow. If the skin is partially devascularized, the result may be loss of epidermis. This is evident as epidermolysis and blister formation. Because the injury is not complete, the skin has the potential to heel by epidermal regeneration. Epidermal cells lining hair follicles and other skin appendages outgrow with the loss of contact inhibition and restore a normal epidermis. During this period the tissues are at risk for bacterial infection. To prevent infection, treat the wound with daily Silvadine gauze dressings. The wound is cleansed daily of all necrotic skin with soap and water, a light coating of Silvadine is applied, and the wound is covered with gauze. In select cases, partial-thickness injuries may be treated with an occlusive dressing such as Duoderm. When effective, these dressing speed the rate of healing. Strategies for care will be discussed. When full-thickness skin loss occurs, there are several options. Specific treatment must be decided based on the patient, procedure, and the presence of underlying devices. In general, the older, sicker, or fragile the patient, the more likely direct surgical intervention is the best option. Surgical closure is also necessary for large wounds or those with critical underlying structures or devices. In these cases the necrotic skin can be excised and the wound reclosed. This protocol decreases the risk of infection and resolves the situation more quickly. In younger patients, in select circumstances without underlying foreign bodies, the wound can be treated with daily dressings and allowed to heal by contraction. This is most useful when the area of skin loss is less than 1 cm in diameter. One to 3-cm wounds in noncritical areas with loose surrounding skin may also heal by contraction in a reasonable time period.

Wound Infection The treatment of a wound infection depends on the specific nature of the infection. Local wound infections seldom need surgical drainage unless there is fluid or pus accumulation. When present, these accumulations should always be drained completely. The presence of a device or foreign body increases the likelihood that antibiotic treatment alone will fail. This means that aggressive surgical treatment with drainage is more likely to be effective. Early initiation of effective antibiotics increases the salvage rates. For optimal results antibiotics should be chosen based on the location of the wound and the pathogens it is exposed to. An initial attempt at percutaneous drainage of infected fluid is usually reasonable. If cellulitis does not resolve within 48 hours or fluid reaccumulates, then a more extensive procedure should be considered. Surgical treatment should include complete drainage and debridement of any necrotic tissue or exudate. If available, pulse-lavage irrigation is an excellent adjunctive method of doing this. If there is a device in the infected space,

when treatment is initiated early and the tissues surrounding an implant are healthy, an attempt can be made to leave the device in place. Fluid accumulation around the device must be kept to a minimum, and a prolonged course ( at least 2 weeks) of antibiotics given. Failure, progressive infection, or continued cellulitis after 48 hours indicates that the device is infected and should be removed. The treatment decision about whether the wound can be closed may be difficult. If treatment for the infection is begun early, the surrounding tissues and patient are healthy, and exposing an implanted device would be a serious problem, then closing the wound after placement of a drain is reasonable. However, this is not the ideal manner of treating the infection and device rescue should not outweigh patient well-being. Drains Open drains and closed-system drains are available. Penrose, red rubber open drains are simple and cheap but they allow bacterial migration into drained space. Open drains are most effective when used in dependent areas. JacksonPratt and Blake closed-system drains limit bacterial ingrowth. However, proper function requires an airtight seal around the drained space or continuous suction.

Monday, March 2, 1998

3:30 pm-5:30 pm Categorical Course: Vascular Imaging Part II (C202) Moderator: Joseph Bonn, MD 3:30 pm Helical Computed Tomography of the Pulmonary and Systemic Vasculature Stephen T. Kee, MD Introduction The development of helical (spiral) computed tomography (CT) has revolutionized the performance of crosssectional imaging. The ability to acquire overlapping images in a short time frame has allowed detailed examination of structures hitherto viewed in a relatively crude fashion. With advanced 3-D reconstruction techniques, CT is seen as a noninvasive replacement for endoscopic procedures, and in particular as a screening tool to detect early colonic or endobronchial carcinomas. Where helical CT has made the most impact, however, is in the imaging of the vasculature. The ability to scan a large area in a short time allows for "capture" of intravenously administered contrast within the arterial tree. Helical CT scans have become the method of choice for imaging aortic pathology, particularly in the work-up of aneurysmal disease, whether for surgical or endovascular repair. The technique is also of benefit in the noninvasive evaluation of peripheral vessel pathology, pulmonary emboli (PE), and pulmonary and peripheral arteriovenous

malformations. This review focuses on the techniques, pitfalls, and benefits of helical CT imaging in the evaluation of the pulmonary and systemic vasculature. Technological Advances The main breakthrough in the development of helical CT is slip-ring technology. Whereas conventional CT scanners could scan for 1 or 2 sec, then rotate back to baseline and scan again, a modern helical CT scanner can scan continuously without having to reset. Using this configuration, the anode and cathode move freely on the scanner gantry, without cable attachments. This development, along with advancements in tube cooling design, allows the scanner to image continuously for up to 40 sec, and acquire a volumetric block of data. These data can then be reconstructed at a variety of different slice thicknesses and overlap 0,2). Helical CT offers a number of advantages in imaging pulmonary disease over conventional CT. Scans to evaluate pulmonary masses that used to take 10 to 15 mins can now be performed in one breath-hold. In these patients contrast dose can also be reduced, as the timing can be more precise, assisting in cost reduction (3). The ability to image the thorax in one breath-hold eliminates respiratory misregistration, avoiding omission of some anatomic levels and/or repeated scanning of others. This prevents lesions, particularly at the lung bases, from escaping detection (4,5). The greatly increased speed of the scanning process, along with more efficient power injectors, allow for the "capture" of contrast in the arterial structures. This allows assessment of the aorta and major branches, as well as the pulmonary arteries. Helical CT scanning now rivals transesophageal echo as the method of choice for detecting and classifying aortic dissection. The technique is now widely utilized to assess atherosclerotic involvement of the carotid bifurcation, the renal arteries, and the major abdominal vessels. Recent work in the evaluation ofPE has suggested that helical CT has a similar accuracy in the detection of central PE to pulmonary angiography (6,7).

Technical Considerations A number of differing terminologies must be mastered in order to gain the maximum performance from the scanner. The table movement during a 360-degree rotation of the CT tube divided by the slice thickness or beam collimation is called the pitch, and usually varies from 1-2-inch increments. The higher the pitch, the greater the area scanned in a certain time, but the in-plane resolution deteriorates with increasing pitch. For optimal resolution in the z-direction a pitch of one should be used. In order to compensate for the "blurring" of the slice edges created by increasing the table movement or pitch, reconstructions of images are performed at an increment of one third to one half of the beam collimation. The anatomic length (2) that is covered is determined by the number of 360-degree rotations (N), the pitch (P), and the collimation (C), 2 = N X P X C (8).

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