Lecture 16 - Diabetic Feet Infections Flashcards
Diabetic feet infections normally begin with ______ which is often secondary to ______ or _______
Neuropathic ulceration
Neuropathy or trauma
T/F: Diabetic foot complications are the main reason for diabetes-related hospitalizations and lower extremity amputations.
True
The principal pathogenic factors in diabetic foot disease are:
Sensory neuropathy
Ischemia
Infection
Ulceration is a consequence of…
The loss of awareness of trauma that can cause skin breakdown
What plays a central role in diabetic foot lesions?
Peripheral neuropathy
In order to test for neuropathy, clinicians use an inexpensive nylon monofilament test. It measures a patient’s risk for _______ and should be performed ______.
Ulceration
Annually
Local ulcer care includes:
sharp debridement and proper wound coverage which helps wound healing and removes bacteria
Management of ulcers consists of
Assessing ulcer for infection
local care
mechanical offloading
Name some of the inframalleolar infections common in diabetes patients.
paronychia cellulitis myositis abscesses necrotizing fasciitis septic arthritis tendonitis osteomyelitis Mal perforans foot ulcer
Outline how a breach in skin integrity allows for deeper colonization and infection.
- Infection (ex. in nail bed) or bacteria on skin
- Broken skin = portal of entry
- Organism/infection penetrates muscle
- Organism grows and spreads
- Body responds to bacteria in deeper parts of muscle
What are the risk factors for foot ulceration and infection?
peripheral motor neuropathy peripheral sensory neuropathy peripheral autonomic neuropathy neuro-osteoarthritic deformities or limited joint mobility vascular (arterial) insufficiency hyperglycemia and other metabolic derangements patient disabilities maladaptive patient behaviors health care system failures
peripheral motor neuropathy
abnormal foot anatomy and biomechanics (ex. clawing toes, high arch, etc.), may lead to excess pressure, callus formation, and ulcers
*may see a change in foot architecture from holding foot in awkward position, which puts pressure on areas that shouldn’t have pressure (slide 9)
peripheral sensory neuropathy
lack of protective sensation, leads to unattended minor injuries
peripheral autonomic neuropathy
deficient sweating, leads to drying and cracking skin
*risk for necrotizing fasciitis
neuro-osteoarthritic deformities or limited joint mobility
abnormal anatomy and biomechanics, may lead to excess pressure
vascular (arterial) insufficiency
impaired tissue viability, wound healing, and delivery of neutrophils
hyperglycemia and other metabolic derangements
impaired immunological function and wound healing and excess collagen cross-linking
patient disabilities
reduced vision, limited mobility, and previous amputations
maladaptive patient behaviors
inadequate adherence to precautionary measures and foot inspection and hygiene measures, poor medical care compliance, excessive weight bearing, inappropriate activities, and poor footwear
health care system failures
inadequate patient education and monitoring of glycemic control and foot care
Signs of infection:
Redness Warmth Swelling/induration Tenderness/pain Purulence
Must have 2 or more symptoms according to IDSA DFI
Signs of infection in patients with neuropathy:
Nonpurulent secretions
Friable/discolored granulation tissue
Undermining of wound edges
Foul odor
IDSA Severity of Infection: Grade 1
Uninfected
No signs or symptoms
IDSA Severity of Infection: Grade 2
Mild
local infection only involving the skin and subcutaneous tissue
erythema around ulcer
exclude other cause of inflammation
IDSA Severity of Infection: Grade 3
Moderate
local infection with erythema > 2cm or in deeper than skin and subcutaneous tissue
no systemic inflammatory response signs
IDSA Severity of Infection: Grade 4
Severe
Local infection with signs of SIRS (must have more than 2: fever, elevated resting heart rate, rapid shallow breathing, elevated WBC)
Who to hospitalize:
Patients with severe infection
patients with a moderate infection and complicating features (severe PAD, no home support)
noncompliant patient w/ outpatient treatment
patients with mild infections
T/F: Patients with a moderate infection can be treated as outpatients.
TRUE as long as they are able to adhere to medical therapy and do not have critical limb ischemia or need surgical intervention.
T/F: There is NO evidence-based admission or discharge criteria for patients with DFI.
TRUE
What are the benefits of fo imaging for diabetic feet?
Lets you know if there is a secondary complication
- helps better define soft tissues purulent collections
- can identify soft tissue findings (bony abnormalities, foreign bodies, calcified arteries or soft tissue gas)
- can aid in finding pathological bone findings (ie osteomyelitis-slide 14)
Ulcer Risk Factors: General or systemic (image on slide 16)
uncontrolled hyperglycemia duration of diabetes peripheral vascular disease blindness or visual loss chronic renal disease older age
Local issues
peripheral neuropathy structural foot deformity trauma and improperly fitted shoes callus history of prior ulcer amputation prolonged elevated pressures limited joint mobility
Risk Factors for infection
wound depth to bone wound duration >30 days recurrent foot wound traumatic wound etiology peripheral vascular disease
What does ulcer evaluation entail?
classification based on extent and depth of ulcer + presence of infection or ischemia
How do clinicians assess diabetic patients with Diabetic foot ulcers for ischemia?
ankle-brachial index and toe pressure measurements
Texas Ulcer Classification (study images on slides 20-27)
Grade 0: Pre- or postulcerative (stages A to D)
Grade 1: Full-thickness ulcer not involving tendon, capsule or bone (stages A to D)
Grade 2: Tendon or capsular involvement without bone palpable (Stages A to D)
Grade 3: Probes to bone (Stages A to D)
Texas Ulcer Classification Staging
A: noninfected
B: Infected
C: Ischemic
D:Infected and ischemic
Wound/Ischemia/Foot Infection (WIFI) System
proposed by Society for Vascular Surgery
goal: provide a more quantitative assessment of peripheral artery disease (PAD) as a predictor and contributor to lower extremity pathology
scoring (none/mild/moderate/severe) using specified criteria similar to Texas system
WIFI Wound Scoring
0: no ulcer and no gangrene
1: Small ulcer and no gangrene
2: Deep ulcer or gangrene limited to toes
3: Extensive ulcer or extensive gangrene
WIFI Ischemia Scoring
Toe pressure/TCPO2
0: > 60 mmHg
1: 40 to 59
2: 30 to 39
3: <30
WIFI Foot Infection Scoring
0: noninfected
1. Mild (<2 cm cellulitis)
2. Moderate (> 2 cm cellulitis/purulence)
3. Severe (systemic response/sepsis)
Infection management
- clinical diagnosis, especially if see signs of infection
- treat based on severity
- Obtain tissue samples for culture and sensitivity via wounder curettage (ideally after debridement and before abx)
Rules for DFI treatment
Don’t treat uninfected wound
Tailor to culture data
no evidence fo subclinical colonization impairing wound healing
Antibiotic Use Principles
Empiric therapy: starts based on clinical evaluation
Tailoring Therapy: change abx in response to clinical data
Convert from IV to PO: minimizes complications and saves money
Use the shortest effective duration of therapy
Monitor Pharmacokinetics: Vancomycin trough and dose adjusting
The most common infecting organisms in western nations are
staphylococci
streptococci
(skin-dwelling bacteria)
T/F: Second organisms to cause infection are often aerobic gram-negative bacilli and anaerobes.
TRUE
The most common pathogens in acute, previously untreated, superficial infected foot wounds DM patients are aerobic gram-positive bacteria like
Staphylococcus aureus and beta-hemolytic streptococci
What pathogen(s) is/are likely to cause infection in patients who recently received abx or who have deep limb-threatening infection or chronic wounds?
aerobic gram-positive or aerobic gram-negative (E. coli, Proteus sp., Klebsiella sp.) and anerobic organisms
NEVER obligate anaerobes as the sole identified species
Signs of systemic toxicity from pathogens
extensive local inflammation
necrosis
malodorous drainage or
gangrene
How may Staphylococus aureus and Streptococcus* contribute to foot infections?
cellulitis without an open skin wound*
infected ulcer and abx naïve*
chronic infected ulcer previously treated with abx therapy*
long duration non-healing wounds
fetid foot (extensive necrosis, gangrene or malodorous)*
**If a patient has a history of _____ infection or colonization within one year, they are at an _____ risk of reinfection, especially due to the pathogen _______. Failing to empirically cover it can pose an unacceptable risk of treatment. Clinicians can use an ______ to determine the strain of bacteria present.
MRSA
Increased
Staphylococcus aureus
Antibiogram
T/F: P. aeruginosa is prevalent in diabetic foot infections in warm climates.
TRUE
What factors increase the risk of infection caused by P. aeruginosa?
macerated ulcers
foot soaking
exposure to water or moist environments
Mild Infection Treatment
outpatient oral antimicrobial therapy
- empiric therapy against skin flora (i.e streptococci and S. aureus)
- agents against methicillin-resistant S. aureus (MRSA) if they have a purulent infection and are at risk
Moderate Infection Treatment
empiric therapy of deep ulcers that extend to the fascia that work against the activity of Streptococci, S. aureus, and MRSA (if at risk)
- can use oral regimen
- if have an extensive infection in deep tissue can treat with empiric parenteral therapy
Single-drug regimens for mild/moderate treatment against streptococci and staphylococci
cephalexin
dicloxacillin
amoxicillin-clavulanate or clindamycin
What medications can be used to treat MRSA?*
*must know at least one for the exam
Trimethoprim-sulfamethoxazole PLUS amoxicillin-clavulanate
-OR-
Clindamycin PLUS Ciprofloxacin/levofloxacin/moxifloxacin
Moderate/Severe treatment agents
Beta-lactam: Ampicillin-sulbactam, piperacillin-tazobactam
Carbapenems: Impenem-cilastatin, meropenem, ertapenem
fluoroquinolones: moxifloxacin
Other: metronidazole (IV) plus one fo the following: ceftriaxone, ceftazidime, cefepime, ciprofloxacin, levofloxacin, aztreonam
PLUS one of the following if need MRSA coverage:
Vancomycin (use for cephalosporin and penicillin-resistant organisms)
Linezolid
Daptomycin
- Assume MRSA for severely infected persons
Severe Infection Treatment
if limb-threatening DFI or systemic toxicity treat w/ broad-spectrum parenteral abx therapy
surgical debridement
empiric therapy against streptococci, MRSA, aerobic gram-negative bacilli, and anaerobes
How is agent selection determined and what are the problems with it?
-Based on clinical trials
Problems:
- lack of standardization
- no single drug or combination is superior
- while the FDA has approved drugs for one symptom (i.e abx for complicated skin/skin infections) but not for accompanying ones such as osteomyelitis
Should topical antimicrobials be used to treat DFI? Why or why not?
Uncertain.
Antiseptics like povidone-iodine are not recommended for open wounds due to cytotoxic effects
No published data for agents such as silver, neomycin, polymyxin B, gentamycin, or muciprocin for DFI
No evidence to recommend silver-containing dressings
Surgical intervention should be considered in what classification(s) of DFIs?
moderate and severe
Examples of surgical intervention include:
debridement
abscess drainage
opening of infected compartments
major amputation
What are the indications of amputation?
extensive gangrene
long, unsuccessful course of therapy
life-threatening soft tissue infection
extensive osteomyelitis
T/F: DFIs constitute a significant cause of morbidity and mortality.
TRUE
T/F: You can treat clinically uninfected ulcers.
FALSE. Only treat if infected.
T/F: Mild/moderate infections can be treated PO without hospital admittance.
TRUE
T/F: Empiric therapy should always cover for staphylococcus and MRSA.
FALSE. Always cover for staphylococcus, but only for MRSA if the infection is severe or the patient has a history of MRSA (infection or colonization)
How can a multidisciplinary team help patients with DFIs and who should make up the team?
Teams help reduce the likelihood and extent of lower extremity amputations; The team should be composed of experienced medical, surgical or nursing providers that use specified evidence-based procedure. An optimal example would be a foot specialist, vascular surgeon, and wound care specialist with access to ID specialists or microbiologists and other disciplines (diabetes, pharmacy, etc.)
If not practical, providers should use telemedicine consultations from experts or form consulting relationships to ensure prompt evaluation and treatment
What does the multidisciplinary approach look like?
Primary care: gatekeeper, yearly monofilament exam, patients 50 y.o. should have ankle-brachial index (ABI) testing
Infectious Disease if patient has a complicated infection
Podiatry: proper footwear per ADA recommendations, insoles for patients with peripheral neuropathy with or without deformity, see patients with PAD and neuropathy, history of diabetic foot ulceration or amputations
orthopedic surgery: when amputation is necessary
