How To Detect And Treat Infected Wounds

Author(s): 
By John S. Steinberg, DPM, Khurram Khan, DPM, and Jonah Mullens

In clinical practice, two of the most common types of infected wounds podiatrists see are ulcerations and postoperative incision sites. In order to resolve these infections and ultimately close these wounds, one must have a strong understanding of the etiology of infected ulcerations and post-op infections, how to assess these wounds and how to select appropriate treatment options. With this in mind, let’s start by discussing pedal ulcerations. Pedal ulcerations provide a portal for pathogen entry and therefore can lead to the development of infection in the deep soft tissues and bone.1,2 If the infective process is not addressed, it can threaten preservation of the limb and life. Early detection of an infected ulceration is imperative to a good clinical outcome. Performing a thorough examination and using appropriate diagnostic modalities are essential when it comes to differentiating between a local soft tissue or osseous infection versus an ascending and/or systemic infection. Doing so will help you determine the appropriate medical and/or surgical intervention.3 Before you begin the examination, it’s important to obtain a thorough patient history as well as a focused history of the wound. Specifically, it’s essential to document any history of recent trauma, delay in treatment, prior infections or immune deficiencies that would place the patient at an increased risk for infection. Inspection of the wound and the periphery should reveal any erythema, lymphangitis, drainage, exposed deep tissues or necrosis. Inspecting the wound will also give you clues as to the etiology of the wound site. For example, you may identify hyperkeratotic or macerated tissues to the wound periphery or perhaps note the functional position and nature of the foot type. During the examination of the wound, one should also be able to recognize induration, fluctuance (underlying abscess), crepitus (soft tissue emphysema), increased skin temperature, tenderness, bulla, edge undermining or odor. Hypotension, tachycardia, elevated temperature and altered mental status can be the first clues in determining the severity of a systemic infection and possible progression into septicemia.

Pertinent Diagnostic Pointers For Infected Ulcers

Serological testing may include but is not limited to glucose levels, hemoglobin A1c, CBC with differential, sedimentation rate, renal (electrolytes, blood urea nitrogen (BUN), creatinine) and hepatic profiles.4 One may submit deep wound tissue cultures and blood cultures with sensitivities for the standard aerobic and anaerobic assessment as well as fungi and acid-fast bacilli tests.5 When it comes to soft tissue wound cultures, the best way to obtain them is via curettage of the base of a cleaned lesion. Superficial swabs should be avoided.6 In general, swab cultures only collect the surface contaminating organisms. Tissue biopsy and culture, fluid aspiration cultures and a possible bone biopsy are better alternatives for culturing the infecting organism. A bone culture is indicated when one suspects osteomyelitis. It is usually performed in conjunction with a bone biopsy, which is considered the gold standard for diagnosis.5,7,8 Differentiating between colonized and contaminated wounds in the lower extremity can be a significant clinical challenge. The Agency for Health Care Policy and Research (AHCPR) Clinical Practice Guideline defines the difference as the concentration of organisms in the wound. An infected wound contains a larger number of microorganisms than a contaminated wound and is generally considered infected when the number of organisms per gram of tissue exceeds 106.9 However, even in the face of a bacterium count of 105 organisms per gram of tissue, one cannot call it an infection until clinical signs and symptoms have manifested in the wound base and peripheral tissues. Problem wound sites are often further complicated by the presence of ischemia and a decreased autoimmune response. Also keep in mind that leukocytosis may mask the evidence of a diabetic infection. This can occur with many other chronic disease states as well. Therefore, when it comes to assessing infection, the overall clinical impression is of primary importance. Culture results are certainly important, but they are viewed as only one aspect of the patients’ total presentation.10,11 Radiographs and other imaging studies all have different benefits as well as deficiencies in assessing the degree of potential infection. Some of the studies that are available include Technetium bone scans, gallium, indium and Tc-99m HMPAO labeled leukocyte scans.12 Therefore, one must analyze multiple signs, symptoms and findings in order to identify the presence or absence of infection, and the degree of risk to the patient.13

Key Treatment Considerations For Infected Ulcerations

Most diabetic foot infections are polymicrobial so one should initiate broad-spectrum and/or mixed antibiotic coverage empirically while awaiting the culture results.14 Treatment may require a combination of intravenous and/or oral therapeutic agents.15 When it comes to modifying the treatment course, it is usually based primarily upon the patient’s clinical response. However, one should also consider culture results and, when necessary, repeat cultures in the overall therapeutic management of the diabetic foot infection. In regard to osteomyelitis, one would commonly treat this for four to six weeks with culture directed antibiosis following the definitive soft tissue and bone resection.5 In cases of methicillin resistant Staph aureus (MRSA) or vancomycin resistant enterococcus (VRE), one must treat infected wounds more aggressively from a surgical and medical perspective. These organism types are now much more prevalent than they were a few years ago. While MRSA and VRE were once found only in nosocomial infections, they now manifest commonly in community-acquired infections as well. In many institutions, there is a decreased threshold toward early aggressive treatment of Staph aureus infections with drugs such as vancomycin and linezolid.

A Closer Look At Contributing Factors To Postoperative Wound Infections

Despite the advances in sterile technique and instrumentation, up to 84 percent of surgically “prepped” feet culture positive for bacteria just prior to skin incision. It is no surprise then that infection of postoperative wounds in elective surgery occurs consistently in 1 to 2 percent of all cases. As with traumatic or chronic wounds, surgical wounds can be influenced by many factors. Malnutrition, dehydration and anemia can increase the risk for surgical wound infection and other complications.4 Malnutrition is indicated by inadequate systemic and local supply of protein, vitamin C, zinc and copper. These elements are required by fibroblasts for the synthesis of collagen. Zinc also plays an important role in wound epithelialization. One may attribute a decrease in serum albumin and transferrin to protein-calorie malnutrition. Wound healing in the elderly population is altered by several factors. One will often note less than optimal circulation/perfusion for wound healing in this group. The reduced liver function alters the synthesis of clotting factor and there is also a slower inflammatory response. Even in the minimally invasive surgical wound created under controlled circumstances, the collagen is less pliable and the scar is less elastic among elderly patients. Obesity and smoking can also cause delayed wound healing in the surgical patient. Smoking reportedly slows and often impairs bone healing, resulting in motion across an orthopaedic surgical site and motion at the skin edges/wound. Also keep in mind that localized edema can cause excessive pressure in the postoperative wound and hinder wound healing. We should note that prevention is the key to lowering the threat of postoperative infections. Surgeons and assisting staff must pay close attention to sterile technique. Whenever possible, one should cover exposed surfaces (such as the forefoot) with a sterile drape, dressing or a surgical glove if the exposure of the surfaces is not necessary for the procedure being performed. Administering appropriate preoperative antibiotics 30 to 60 minutes prior to the procedure can have a very positive influence on lowering infection rates.

Essential Insights On Diagnostic Signs And Culturing

Body temperature fluctuation and increased white blood cell count with shifts to the left (presence of band cells) are reliable indicators of postoperative infection. In the initial assessment of postoperative wounds, one should check for drainage, fluctuance, erythema or odor. Fluctuance of a surgical wound often indicates hematoma, seroma or perhaps an abscess. In addition, the presence of pain that is out of proportion to the procedure performed can be a significant warning sign of an infection. If any or all of these warning signs are present during the postoperative period, the surgeon must decide on a course of action. Generally, one may remove a few sutures/staples in order to facilitate drainage of the wound site and subsequent irrigation and exploration of the site. If one suspects a significant infection, then a return to the operating room will most likely be necessary in order to open, debride and further explore the wound site as needed. Inspecting and culturing the wound exudate can also provide valuable information on infection. Staphylococcal infections possess odorless golden pus whereas streptococcal infections exhibit serous to serosanguineous drainage with possible non-blanching erythema/petichiae and red streaking (lymphangitis). Infected wounds require immediate action from the health care team. Obtaining a quick gram stain from the wound site facilitates early empiric antibiotic therapy and one can adjust the choice of antibiotic accordingly after receiving the results of the deep tissue or bone cultures. When the patient has an infected postoperative wound, you should perform formal incision and drainage with possible debridement of all necrotic tissue, foreign debris, hematoma and dead space. One would normally leave these wounds open to facilitate management and eventually consider delayed closure once the clinical signs of infection have resolved. Some have proposed that if a wound generates three negative cultures, then it is deemed ready for closure. In general, this is clinically challenging because all open wounds have a high predilection for sub-clinical bacterial contamination, which would continually yield positive cultures despite the fact that no infection is present. Robson, et. al., found that wounds with delayed closure that contain 105 or less bacteria progressed to uncomplicated wound healing whereas none of the wounds with >105 organisms per gram of tissue healed successfully.16

A Guide To Treating Infected Post-Op Wounds

One should be especially cautious when treating the postoperative wounds of patients who are immunocompromised, have rheumatoid arthritis or have a history of chronic steroid therapy. Patients with vascular disease are more prone to wound complications. Proper preoperative vascular screening is indicated for patients with ankle/arm indices less than 0.6 and particularly in those with non-palpable extremity pulses. Hypoxia decreases the body’s resistance to infection, impairs fibroblast division and collagen production.5 If one suspects a resultant wound complication from vascular compromise, you may see necrotic tissue and excessive drainage, which will ultimately increase the risk of a wound infection. Surgical debridement is a key component in managing grossly infected or necrotic wounds, and includes the removal of all non-viable tissue from the surgical wound as well as the surrounding wound borders.17 Removing necrotic tissue on a regular basis can expedite wound healing and has been shown to increase the probability of attaining full secondary closure. Less frequent surgical debridement can have a negative impact upon the rate of wound healing and may secondarily increase the risk of infection as open wounds provide a portal of entry for bacteria, fungi and yeast. One should repeat debridement of the ulcer or infected postoperative wound site as needed if new necrotic or infectious tissues continue to form. (Also see “Other Key Considerations On Debridement” below.) Medical therapy for postoperative wounds should be guided by culture and sensitivity results. When confronted by non-limb threatening infections, one should aim treatment at Staph and Strep. Most diabetic foot infections of postoperative wounds are polymicrobial so one should initiate broad-spectrum and/or mixed antibiotic coverage empirically. When it comes to modifying the treatment course, this is primarily based upon the patient’s clinical response. However, one should consider culture results and, when needed, repeat cultures in the overall therapeutic management of infected post-op wounds in the diabetic foot. Infection with suspected gas-producing, anaerobic bacteria often necessitates emergency hospital admission and immediate surgical intervention. Osteomyelitis requires bone and possible joint resection or partial amputation of the foot.

Other Key Considerations On Debridement

While surgical debridement plays an important role in managing infected wounds, other forms of debridement may have some benefit in reducing the risks associated with a wound infection. Irrigation is another form of mechanical debridement and is commonly utilized at the time of surgery and during dressing changes. Flush irrigation under pressure (> 8 psi) appears to be more effective in reducing the bacterial count than low-pressure flush or scrubbing with a saline soaked sponge.18 Additionally, pulse lavage systems can be very efficacious in removing foreign debris. As per the surgeons’ preference, one may use 2 to 4 liters or more of sterile saline or an antibiotic flush for larger wound irrigation in conjunction with surgical debridement or wound excision in the operating room. Alternatively, one may use a 60 cc. syringe with an 18-gauge needle or a 19-gauge angiocath in order to provide pressure irrigation when pulse lavage is not available in the operating room or is not practical for daily dressing changes.18 A new technology involves aggressive surgical debridement via a high pressure stream of saline that creates its own vacuum and removes non-viable tissue from the wound. This device called the Versajet offers different angled and sized treatment wands to manage a variety of wounds, and was recently approved by the FDA.

Final Notes

In general, if one institutes early aggressive surgical and medical management for infected wound sites, it will facilitate successful outcomes and preservation of limb and function in a majority of these cases. Dr. Steinberg is an Assistant Professor in the Department of Orthopaedics/Podiatry at the University of Texas Health Science Center. Dr. Khan is Chief Resident in the Department of Orthopaedics/Podiatry at the University of Texas Health Science Center. Mr. Mullens is a fourth-year podiatry student at the California School of Podiatric Medicine at Samuel Merritt College. CE Exam #121 Choose the single best response to each question listed below: 1. When it comes to obtaining soft tissue wound cultures … a) swab cultures are highly recommended as they collect the surface contaminating organisms. b) the best way to obtain them is via curettage of the base of a cleaned lesion. c) they are usually performed in conjunction with a bone biopsy. d) none of the above. 2. A bone culture… a) is indicated when one suspects osteomyelitis. b) is usually reserved for severely infected ulcers. c) is usually performed in conjunction with a bone biopsy. d) a and c e) all of the above 3. An infected wound … a) contains a larger number of microorganisms than a contaminated wound. b) is generally considered infected when the number of organisms per gram of tissue exceeds 106. c) is generally considered infected when the number of organisms per gram of tissue exceeds 104. d) a and b e) a and c 4. One would commonly treat osteomyelitis … a) for eight to 10 weeks with culture directed antibiosis following the definitive soft tissue and bone resection. b) for two months with culture directed antibiosis following the definitive soft tissue and bone resection. c) for four to six weeks with culture directed antibiosis following the definitive soft tissue and bone resection. d) none of the above 5. Which of the following can increase the risk of surgical wound infection? a) malnutrition b) anemia c) dehydration d) all of the above e) none of the above 6. In regard to post-op wound healing in elderly patients, which of the following statements is false? a) Collagen is more pliable. b) They may have less than optimal circulation/perfusion, which can have an adverse effect. c) They have a slower inflammatory response. d) All of the above e) None of the above 7. Which of the following statements about streptococcal infections is false? a) These infections tend to have serous to serosanguineous drainage. b) One may notice red steaking (lymphangitis) with these infections. c) These infections tend to have odorless, golden pus. d) One may notice non-blanching erythema/petichiae with these infections. e) All of the above 8. __________ debridement is a key component of managing grossly infected or necrotic wounds. a) Enzymatic b) Mechanical c) Surgical d) Autolytic e) None of the above 9. Flush irrigation under pressure (> 8 psi) appears to be … a) less effective in reducing the bacterial count than low-pressure flush or scrubbing with a saline soaked sponge. b) more effective in reducing the bacterial count than low-pressure flush or scrubbing with a saline soaked sponge. c) equally effective to using low-pressure flush or scrubbing with a saline soaked sponge in reducing the bacterial count. d) None of the above Instructions for Submitting Exams Fill out the postage-paid card that appears on the following page or log on to www.podiatrytoday.com and respond electronically. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam. Responses will be accepted up to 12 months from the publication date.
 

 

References:

References 1. Veves A, Murray H, Young MJ, Boulton AJM. The risk of ulceration in diabetic patients with high foot pressures: a prospective study. Diabetologia 35:660, 1992. 2. Young MJ, Breddy JL, Veves A, Boulton AMJ. The prediction of diabetic neuropathic foot ulceration using vibratory perception thresholds: a prospective study. Diabetes Care 17:557-560, 1994. 3. Steed DL, et al. [and diabetic ulcer study group]. Clinical evaluation of recombinant human platelet derived growth factor for the treatment of lower extremity diabetic ulcers. J Vasc Surg, 21:71-81, 1995. 4. Brand, P, Yancey P. Pain: The Gift Nobody Wants. Harper Collins 1993. 5. Reiber GE, Vileikyte L, Boyko EJ, del Aguila M, Smith DG, Lavery LA, Boulton AJ. Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care. 1999 Jan;22(1):157-62. 6. Frykberg RG, Armstrong DG, Giurini J, Edwards A, Kravette M, Kravitz S, Ross C, Stavosky J, Stuck R, Vanore J. Diabetic foot disorders: a clinical practice guideline. American College of Foot and Ankle Surgeons. J Foot Ankle Surg. 2000;39(5 Suppl):S1-60. Review. 7. Grayson ML. Diabetic foot infections: antimicrobial therapy. Infect Dis Clin N.A. 9:143-161, 1995. 8. Hamer ML, Robson MC, Krizek TJ, et al. Quantitative bacterial analysis of comparative wound irrigations. Ann Surg 181:819-822, 1975. 9. Suntken G, Starr B, Ermer-Seltun J, Hopkins L, Preftakes D. Implementation of a comprehensive skin care program across care settings using the AHCPR pressure ulcer prevention and treatment guidelines. Ostomy Wound Manage. 1996 Mar;42(2):20-2, 24-6, 28-30 passim. 10. Thomson FJ, Veves A, Ashe A, Knowles EA, Gem J, Walker MG, Hirst P, Boulton A, A team approach to diabetic foot care - the Manchester experience. The Foot 2:75-82,1991. 11. Kozak GP, Campbell DR, Frykberg RG, Habershaw GM, (eds). Management of Diabetic Foot Problems. WB Saunders, Philadelphia, 1995. 12. Armstrong DG, Lavery LA, Stern S, Harkless LB. Is prophylactic diabetic foot surgery dangerous? J Foot Ankle Surg 35:585-589, 1996. 13. Diabetes Control and Complications Trial Research Group. DCCT protocol. Springfield, Virginia: U.S. Department of Commerce, National Technical Information Service, 1988 (publication no PB88-116462-AS). 14. Reiber GE, Vileikyte L, Boyko EJ, del Aguila M, Smith DG, Lavery LA, Boulton AJ.Causal pathways for incident lower-extremity ulcers in patients with diabetes from two settings. Diabetes Care. 1999 Jan;22(1):157-62. 15. Grayson ML. Diabetic foot infections: antimicrobial therapy. Infect Dis Clin N.A. 9:143-161, 1995. 16. Robson MC, Stenberg BD, Heggers JP. Wound Healing Alterations Caused by Infection. Clinics In Plastic Surgery 17: 451-465, 1990. 17. Armstrong DG, Harkless LB. Outcomes of Preventative Care in a Diabetic Foot Specialty Clinic. J Foot Ankle Surg 37:460-466, 1998. 18. Gross A, Cutright DE, Bhaskar SN. Effectiveness of pulsating water jet lavage in treatment of contaminated crushed wounds. Am J Surg 124:373-377, 1972.

 

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