45 - Diabetic Foot Infections Flashcards
What does caring for a diabetic foot infection require?
- Requires a multidisciplinary team of healthcare professionals
What health care professionals will be included in the care of a diabetic foot infection?
o Vascular surgeon o Foot and ankle specialist o Internal Medicine o Infectious Disease specialist o Renal o Orthotist o Nutrition o Physical Therapist o Nursing o Social services
This is a HUGE burden on health care
What do you do on initial evaluation of a diabetic foot infection?
o H&P, determine if patient needs hospital admission
o Baseline labs
o Cultures
What will you do for treatment of a diabetic foot infection?
o Antibiotics
o Surgery
What two concerns should you be assessing for in a diabetic foot infection?
MRSA & osteomyelitis
2012 Clinical Practice Guidelines for the “Diagnosis and Treatment of Diabetic Foot Infections”
o Developed by executive committee made up of panel of experts with special interest/expertise in the area of diabetic foot infections
o Multidisciplinary panel representing Internal Medicine, Infectious Disease, Podiatry, Vascular Surgery
o Performed extensive search and review of the literature
o Reviewed and discussed the available evidence
o Made recommendations based on their findings, discussions and overall consensus
How do you diagnose an infection clinically?
- IMPORTANT - Not all wounds/ulcers are infected – NEED to diagnose infection CLINICALLY
- Infection should be diagnosed clinically:
- Presence of purulent secretions
- Presence of at least 2 cardinal signs of inflammation:
Erythema
Edema
Warmth
Induration
Pain or tenderness to the affected extremity
Describe the infection severity scale
- Interchangeable four-level grading system specifically for infection
- Combines the grading systems developed by the International Working Group on the Diabetic Foot (IWGDF) and the Infectious Diseases Society of America (IDSA)
IDSA = uninfected, IWGDF = 1
Wound lacking purulence or any manifestations of inflammation
ISDA = mild, IWGDF = 2
Presence of purulence or more than two manifestations of inflammation (pain, tenderness, erythema, warmth or induration) but any cellulitis/erythema extends less than 2 cm around the ulcer and the infection is limited to the skin or superficial subcutaneous tissues, no other local complications or systemic illness
ISDA = moderate, IWGDF = 3
Infection (as defined previously) in a patient who is systemically well and metabolically stable but that is associated with more than one of the following characteristics
- Cellulitis extending more than 2 cm
- Lymphangitic streaking
- Spread beneath the superficial fascia
- Deep tissue abscess
- Gangrene
- Involvement of muscle, tendon, joint or bone
ISDA = severe, IWGDF = 4
Infection in a patient with signs and symptoms of systemic toxicity (fever, chills and leukocytosis) or metabolic instability (tachycardia, hypotension, confusion, vomiting, acidosis, severe hyperglycemia or azotemia)
The patient should be evaluated in three areas
- Patient as a whole
- Affected limb/foot
- Wound evaluation
Patient as a whole
o What is the patient’s systemic response to infection (fever, chills, HR, blood pressure)?
o What is the patient’s metabolic state?(lab workup – look at it TOGETHER with clinical)
o What is the patient’s social situation, cognitive state?
Affected limb/foot
o Are there any biomechanical manifestations (callus, Charcot deformity, hammertoes)?
o What is the patient’s vascular status to the lower extremity?
o Is there loss of protective sensation?
Wound evaluation
o Measurements
o Is infection present (redness, tracking under skin, probe to bone, discharge, etc.)?
o Radiologic studies (plain radiographs, CT – MRI is NOT appropriate)
o He will not document a certain grade, he will document what he sees – very detailed
Goals of the three level approach to patient evaluation
- Determine the extent/severity of infection (radiographs, MRI, CT, etc., if infected, is hospitalization required?)
- Determine the microbial etiology of the infection
- Determine the cause of the wound/ulcer: Altered foot biomechanics? Improper shoe gear? Improperly fitted bracing?
- Determine any contributing co-morbidities: Underlying vascular disease, Hyperglycemia, Renal disease
**Is hospital admission required? **
KNOW THIS
- Patients with severe infections
- Patients with critical limb ischemia
- Patients with mild or moderate infections with complicating factors
Laboratory data
- Complete Blood Count (CBC)
- Basic Metabolic Panel
- Erythrocyte Sedimentation Rate
- C-Reactive Protein (CRP)
- He has started doing an A1c and blood glucose to evaluate metabolic status
**Cultures – THIS IS IMPORTANT **
KNOW ALL OF THIS
- How should cultures be collected?
- When should cultures be obtained?
- Why tissue culture/biopsy over swab cultures?
How should cultures be collected?
o Whenever possible, cultures of deep tissue by means of curettage or biopsy is preferred over swab cultures***
o Cultures should be sent to laboratory in sterile container properly labeled as to the specimen/tissue type and anatomic location from which the specimen was obtained.
o Needle aspiration – Useful for obtaining purulent samples
When should cultures be obtained?
o When wound is determined to be infected based on clinical assessment
o Cultures should be obtained to IDENTIFY organism causing clinical infection NOT to DIAGNOSE infection
o Whenever possible, obtain cultures prior to initiation of antibiotics
o If patient is stable but not responding to current therapy, stop antibiotics for short period of time (48-72 hrs) then re-culture – VERY IMPORTANT due to false negative result***
Why tissue culture/biopsy over swab cultures?
o Generally provide more accurate culture result vs. swab
o Swab cultures yield a greater range of organisms but may not identify deeper organisms/flora
o Swab specimens yield fewer anaerobes
- If anaerobic swab is performed make certain it is properly collected (i.e. use swab designed for anaerobic collection)
- Note: Unless bacterial count is high, anaerobic organisms could be lost during collection process with exposure to room air
Necessity of avoiding antibiotics in uninfected wounds
o Use of antibiotics for the purposes of prophylaxis against infection or for the enhancement of wound healing is NOT supported
o Do NOT put them on antibiotics unless an infection is presence
o Overuse encourages resistance – this is all it accomplishes, which can be dangerous
o Either frank resistance or an increase in the minimum inhibitory concentration (MIC) – He always picks the one with the lowest MIC
o Vancomycin Resistant S aureus
o Arise of multi-drug resistant gram-negative organisms
o Unnecessary financial burden
o Drug related adverse effects
Antibiotic selection for initial emperical therapy
o Based on severity & available microbiological data (likely etiologic organism)
o Agents targeted for aerobic gram-positive cocci may be sufficient in mild infections
o Severe infections should be covered with broad-spectrum agents
o Cover for gram-positive cocci
o MRSA coverage based on prevalence (“Escalation and De-escalation theory”)
o You can start vancomycin prophylactically, but stop it if it comes back negative for MRSA
Antibiotic selection for definitive antibiotic therapy
o Based on several factors o Severity of infection o Culture results o Mild infections – 1 to 2 weeks of therapy o Moderate to severe infections – 2 to 4 weeks o Depends on other factors o Adequacy of debridement o Soft tissue coverage o Wound vascularity
NOTE: Because diabetics have such bad vascular status, they will likely fail oral antibiotics due to the lack of circulation
Considerations for surgical intervention
o Presence of deep abscess o Extensive bone or joint involvement o Crepitus o Necrosis or gangrene o Necrotizing fasciitis o NOTE: When considering surgery, patients should be evaluated for adequate vascular status/need for revascularization and consider vascular surgery consult when indicated
Osteomyelitis
- Challenging complication to treat
- Presence of osteomyelitis increases likelihood of surgical intervention including amputation
- Increases the duration of antibiotic therapy
- Hinders healing of overlying tissue
- S. aureus – Most common and most virulent gram positive organism
- Pseudomonas – Most resistant gram negative organism
- Fungi – Rare pathogens in cases of osteomyelitis
Diagnosis of osteomyelitis includes…
- Clinical
- Laboratory
- Imaging
- Bone biopsy
Clinical diagnosis of osteomyelitis
o Probe to bone (“if it probes to bone, it is osteomyelitis until proven otherwise)
o Overlying ulcer >2 cm²
o Ulcers of long duration (> 4 - 6weeks )
Laboratory markers of osteomyelitis
o Leukocytosis – Infrequent in diabetic foot osteomyelitis
o Elevated C-reactive protein
o Elevated ESR (NOTE: there is controversy in the literature as to reliability)
Imaging for osteomyelitis
Plain radiographs
- Poor sensitivity in early stages
- Infection can precede radiologic changes by up to 4 weeks
- May be difficult to distinguish from Charcot
MRI
- Imaging modality of choice (very helpful for surgical planning of excision border)
- Sensitivity reported in literature to be 90% - 100%
- High positive and negative predictive values
Bone biopsy
o Gold Standard diagnostic test
o Should be taken aseptically through non-ulcerated area or intraoperatively
o Sent for histology and microbiology
o Ideally performed prior to initiation of antibiotics (beware of false negative results)
Treatment of osteomyelitis - antibiotics alone vs surgical debridement/resection
o Four scenarios for consideration of non-surgical management
o No acceptable surgical target (resection would lead to unacceptable loss of function)
o Vascular disease for which reconstruction is not an option but patient wants to refrain from amputation
o Infection restricted to forefoot with minimal soft tissue loss
o Risk outweighs benefit
Combined surgical resection and antibiotic therapy
o If resection is performed obtain specimen from surgical margin for microbiology and pathology
o Determines if residual infection is present and will also help distinguish acute vs. chronic process and therefore determine length & route of antibiotic therapy
Treatment principles for diabetic foot infections
** KNOW THIS ***
Eradicate bacterial load with incision and drainage and debridement
o This step must be done regardless of vascular supply
o Must remove ALL Non-Viable Bone and Soft tissue. Worry about closure of wound when infection eradicated
o **Do NOT CLOSE an infected wound **
Start with empirical antibiotics and focus therapy based on reliable deep cultures
o Length of antibiotics depends on severity of infection, response of infection to treatment (typically 2 to 8 weeks)
o Oral
o Intravenous (In-patient or out-patient (via PICC line, central line))
o Antibiotic beads
Closure of wounds
Treatment of non-limb threatening infections
- Debride necrotic tissue
- Start with broad spectrum antibiotic
- Deep culture should be taken
- Adjust antibiotic according to culture and patient response
- Local wound care and plan for closure
Treatment of limb/life threatening infections
EMERGENT SURGERY REQUIRED
- Admission to hospital
- Incision and drainage of abscess and debridement of all necrotic soft tissue and bone
- May require surgical debridement every 48 hours until necrotic tissue is eradicated
- Start with broad spectrum antibiotic
- Deep culture should be taken
- Adjust antibiotic according to culture and patient response
- Assess for vascular disease
- Optimize medical and nutritional status
- Local wound care and plan for final closure when infection is eradicated
CASE STUDY I
- 1 week history of swelling and drainage after utilizing a medicated corn pad
- Worsening symptoms of pain in 5th toe and swelling and drainage
Labs
o WBC – normal
o Temp – 98 F
o X-rays – negative for gas or bone destruction
Diagnosis and treatment for CASE STUDY I
Diagnosis: non-limb threatening infection
Treatment: I&D in the office, culture , local wound care
o Treatment
o Debride superficial abscess
o Oral antibiotic
o Culture of purulence
o MSSA – Methicillin Sensitive Staph Aureus
o Local wound care
CASE STUDY II
- 5 day history of swelling, drainage and erythema in the 1st inner space after stepping on a roofing nail at work
- Worsening symptoms of malaise and pain in forefoot
Labs
o WBC -17.00
o Temp – 100 F
o X-rays – negative for gas or bone destruction
Diagnosis and treatment for CASE STUDY III
Diagnosis: deep abscess
o Admitted to hospital o IV Unasyn o I&D performed that day o Deep cultures taken o 2 weeks of IV antibiotics o You continue to debride until you see HEALTHY, BLEEDING TISSUE ***
CASE STUDY III
- Patient with increased malodor and pain in the arch over the last 2 days.
- Presented to Emergency room
- Worsening symptoms of malaise and pain in midfoot. Extreme malodor from ulcer
Labs o WBC -25.00 o Temp – 102 F o Vitals not stable o X-rays – positive for gas
Diagnosis and treatment for CASE STUDY III
Diagnosis: sepsis, limb/life threatening wound, need to go to OR emergently
o Blood cultures positive for Staph Aureaus
o Patient in sepsis
o This moves very rapidly, so you will need to emergently take patient to OR
o Will need to go back to OR to debride numerous times to remove more necrotic tissue
o Can put wound VAC on the wound to get good granulation tissue
o Skin graft will be needed to cover
