Diabetic foot = القدم السكرية |
Diabetic foot
Foot infections are the most common problems in persons with diabetes. These individuals are predisposed to foot infections because of a compromised vascular supply secondary to diabetes. Local trauma and/or pressure (often in association with lack of sensation because of neuropathy), in addition to microvascular disease, may result in various diabetic foot infections. For additional information, see Medscape’s Diabetic Microvascular Complications Resource Center. The spectrum of foot infections in diabetes ranges from simple superficial cellulitis to chronic osteomyelitis. Infections in patients with diabetes are difficult to treat because these patients have impaired microvascular circulation, which limits the access of phagocytic cells to the infected area and results in a poor concentration of antibiotics in the infected tissues. For this reason, cellulitis is the most easily treatable and reversible form of foot infections in patients with diabetes. Deep skin and soft tissue infections are also usually curable, but they can be life threatening and result in substantial long-term morbidity. In terms of the infecting microorganisms and the likelihood of successful treatment with antimicrobial therapy, acute osteomyelitis in people with diabetes is essentially the same as in those without diabetes. Chronic osteomyelitis in patients with diabetes mellitus is the most difficult infection to cure. Adequate surgical debridement, in addition to antimicrobial therapy, is necessary to cure chronic osteomyelitis. Patients with diabetes also can have a combined infection involving bone and soft tissue called fetid foot. This extensive, chronic soft tissue and bone infection causes a foul exudate and usually requires extensive surgical debridement and/or amputation. Individuals with diabetes may also have peripheral vascular disease that involves the large vessels, in addition to microvascular and capillary disease that results in peripheral vascular disease with gangrene. Dry gangrene is usually managed with expectant care, and gross infection is usually not present. Wet gangrene usually has an infectious component and requires surgical debridement and/or antimicrobial therapy to control the infection. Except for chronic osteomyelitis, infections in patients with diabetes are caused by the same microorganisms that can infect the extremities of those without diabetes. Gas gangrene is conspicuous because of its low incidence in patients with diabetes, but deep skin and soft tissue infections, which are due to gas-producing organisms, frequently occur in patients with diabetes. In general, people with diabetes have infections that are more severe and take longer to cure than equivalent infections in other people.
Diabetes mellitus is a disorder that primarily affects the microvascular circulation. In the extremities, microvascular disease due to "sugar-coated capillaries" limits the blood supply to the superficial and deep structures. Pressure due to ill-fitting shoes or trauma further compromises the local blood supply at the microvascular level, predisposing the patient to infection. The infection may involve the skin, soft tissues, bone, or all of these tissues. Diabetes also accelerates macrovascular disease, which is evident clinically as accelerating atherosclerosis and/or peripheral vascular disease. Most diabetic foot infections occur in the setting of good dorsalis pedis pulses; this finding indicates that the primary problem in diabetic foot infections is microvascular compromise. Impaired microvascular circulation hinders white cell migration into the area of infection and limits the ability of antibiotics to reach the site of infection in an effective concentration. Diabetic neuropathy may be encountered in conjunction with vasculopathy. This may allow for incidental trauma that goes unrecognized (eg, blistering, penetrating foreign body). In chronic osteomyelitis, a sequestrum and involucrum form; these represent islands of infected bone. Bone fragments that are isolated have no blood supply. Administered antibiotics do not penetrate the devascularized infected bone fragments; they can enter the area of osteomyelitis only via the remaining blood supply. Therefore, antibiotic therapy alone cannot cure patients with chronic osteomyelitis without surgical debridement to remove these isolated infected elements. Surgical debridement is essential to remove the infected bony fragments that the antibiotics cannot reach so that affected areas can be treated with antimicrobial therapy.
PhysicalFindings after physical examination may include the following:
CausesThe microbiologic features of diabetic foot infections vary according to the tissue infected.
Laboratory StudiesCellulitis
Skin and soft tissue infections
Acute osteomyelitis
Chronic osteomyelitis
Imaging StudiesCellulitis: Image studies are not applicable. Deep skin and soft tissue infections
Acute osteomyelitis
Chronic osteomyelitis
Other TestsPatients with diabetic foot infections and peripheral vascular disease may benefit from vascular surgical evaluation to bypass large-vessel occlusive disease. However, large-vessel bypass does not cure the microvascular component of diabetic foot infections. ProceduresAspiration of a sample from the leading edge of the erythematous border in a patient with cellulitis is usually not necessary, but a sample may be aspirated if the likely organism must be identified on initial presentation. However, the yield is low, likely to be less than 5%. Samples from deep skin and soft tissue infections may be aspirated. Gram stains and/or cultures may be used to identify the organism. Aside from blood culturing, radiography, and nuclear imaging studies, bone biopsy is not necessary in acute osteomyelitis because the pathogens are predictable. Bone biopsy performed under aseptic conditions in the operating room is the preferred way to identify the causative pathogen in chronic osteomyelitis. Because surgical debridement is critical in treating chronic osteomyelitis, bone biopsy specimens are usually not obtained during the surgical debridement procedure. Histologic FindingsInvolucrum and/or sequestrum may be present in the cortical bone in cases of chronic osteomyelitis. Subperiosteal elevation and/or infection may involve the cortex in acute osteomyelitis. StagingStaging is applicable only in cases of chronic osteomyelitis that require surgery
Medical CareImmobilization is important in acute or chronic osteomyelitis. Surgical CareChronic osteomyelitis cannot be cured without adequate surgical debridement. ConsultationsAppropriate consultation with a surgeon should be obtained for debridement and/or amputation in chronic osteomyelitis. A general or vascular surgeon should be consulted for the debridement or decompression of compartment syndromes in patients with deep skin and soft tissue infections. An infectious disease specialist should be consulted in the treatment of all patients with diabetic foot infections to optimize the antimicrobial therapy. DietDietary modifications are not applicable except to optimize diabetes control. ActivityThe patient may participate in activities as tolerated. However, weight-bearing may be contraindicated. MedicationIn patients with diabetes, cellulitis is generally caused by group A and group B streptococci and, occasionally, S aureus. Cellulitis may be treated with single antibiotics that have the appropriate spectrum or with combination therapy that covers the appropriate organisms. AntibioticsAppropriate monotherapy for cellulitis includes cefazolin or clindamycin. Although gram-negative organisms are the unusual causes of cellulitis, even in diabetes, if they are suspected, a fluoroquinolone (eg, levofloxacin) may be used in conjunction with clindamycin. In patients with diabetes, deep skin and severe soft tissue infections are usually due to mixed aerobic and anaerobic organisms. These infections may be treated with monotherapy involving meropenem or piperacillin and tazobactam. Alternatively, clindamycin plus levofloxacin or metronidazole may be used. Acute osteomyelitis, which usually is due to S aureus, may be treated with cefazolin, clindamycin, and an antistaphylococcal penicillin (eg, nafcillin). In chronic osteomyelitis, coverage must be directed against S aureus, group A and group B streptococci, aerobic gram-negative bacilli (excluding P aeruginosa), and B fragilis. Monotherapy for chronic osteomyelitis may include ampicillin and sulbactam, piperacillin and tazobactam, or meropenem. In chronic osteomyelitis, antimicrobial therapy without adequate debridement does not eliminate the infection. Combination therapy for diabetic foot infections involves levofloxacin plus clindamycin. Meropenem (Merrem)Bactericidal broad-spectrum carbapenem antibiotic that inhibits cell-wall synthesis. Effective against most gram-positive and gram-negative bacteria. Has slightly increased activity against gram-negative species and slightly decreased activity against staphylococci and streptococci compared with imipenem. Structurally similar to beta-lactam antibiotics, but not related to beta-lactam drugs in terms of hypersensitivity. Carbapenems and monobactams do not cross-react in patients who are allergic to penicillin, even those who have an anaphylactic reaction to penicillin. Adult1 g IV q8h Pediatric40 mg/kg IV q8h Probenecid may inhibit renal excretion, increasing levels Documented hypersensitivity PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsPseudomembranous colitis and thrombocytopenia (immediately discontinue) Ampicillin and sulbactam (Unasyn)Drug combination of a beta-lactamase inhibitor with ampicillin. Covers skin, enteric flora, and anaerobes. Not ideal for nosocomial pathogens. Adult1.5-3 g (1 g ampicillin and 0.5 g sulbactam to 2 g ampicillin and 1 g sulbactam) IV q6h; not to exceed 4 g/d sulbactam or 8 g/d ampicillin Pediatric<3 months: Not established Probenecid and disulfiram elevate ampicillin levels; allopurinol decreases ampicillin effects and has additive effect on ampicillin rash; may decrease effect of oral contraceptives Documented hypersensitivity PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsAdjust dose in renal failure; evaluate rash and differentiate from hypersensitivity reaction Piperacillin and tazobactam (Zosyn)Antipseudomonal penicillin plus a beta-lactamase inhibitor. Inhibits biosynthesis of cell wall mucopeptide and is effective during the active multiplication stage. Adult4 g IV q8h Pediatric75 mg/kg IV q6h Tetracyclines may decrease piperacillin effects; high concentrations of piperacillin may physically inactivate aminoglycosides if administered in the same IV line; synergistic effects with concurrent aminoglycosides; probenecid may increase penicillin levels; high-dose parenteral penicillins may increase risk of bleeding Documented hypersensitivity; do not use oral penicillin in severe pneumonia, bacteremia, pericarditis, emphysema, meningitis, and purulent or septic arthritis during the acute stage PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsAssess CBC count before therapy and at least weekly during therapy; during therapy, monitor AST and ALT for liver function abnormality; caution in hepatic insufficiency; perform urinalysis and determine BUN and creatinine levels during therapy (adjust dose if elevated); monitor blood levels (possible neurotoxic reaction) Cefazolin (Kefzol, Ancef, Zolicef)First-generation semisynthetic cephalosporin that arrests bacterial cell-wall synthesis, inhibiting bacterial growth. Primarily active against skin flora, including S aureus. Adult 1 g IV q8h Pediatric25-100 mg/kg/d IV/IM divided q6-8h depending on severity of infection; not to exceed 6 g/d Probenecid prolongs effect; coadministration with aminoglycosides may increase renal toxicity; may yield false-positive urine-dip results for glucose Documented hypersensitivity PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsAdjust dose in severe renal insufficiency (high doses may cause CNS toxicity); superinfections and promotion of nonsusceptible organisms may occur with prolonged or repeated therapy Clindamycin (Cleocin)Lincosamide for the treatment of serious skin and soft tissue staphylococcal infections. Adult150-300 mg/dose PO q8h; not to exceed 1.8 g/d Pediatric8-20 mg/kg/d PO as hydrochloride or 8-25 mg/kg/d as palmitate divided tid/qid Increases duration of neuromuscular blockade induced by tubocurarine and pancuronium; erythromycin may antagonize effects; antidiarrheals may delay absorption Documented hypersensitivity; regional enteritis, ulcerative colitis, hepatic impairment, and antibiotic-associated colitis PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsAdjust dose in severe hepatic dysfunction; no adjustment necessary in renal insufficiency; associated with severe and possibly fatal colitis by allowing overgrowth of Clostridium difficile Levofloxacin (Levaquin)Used to treat complicated and uncomplicated skin and skin structure infections. Fluoroquinolones should be used empirically in patients likely to develop exacerbation due to resistant organisms to other antibiotics. This is the L stereoisomer of the D/L parent compound ofloxacin, the D form being inactive. Good monotherapy with extended coverage against Pseudomonas species, as well as excellent activity against pneumococci. Agent acts by inhibition of DNA gyrase activity. PO form has bioavailability that reportedly is 99%. Adult500 mg PO/IV q24h Pediatric<18 years: Not recommended
Antacids, iron salts, and zinc salts may reduce serum levels; administer antacids 2-4 h before or after fluoroquinolone use; cimetidine may interfere with metabolism of fluoroquinolones; reduces therapeutic effects of phenytoin; probenecid may increase serum concentrations; may increase toxicity of theophylline, caffeine, cyclosporine, and digoxin (monitor digoxin levels); may increase effects of anticoagulants (monitor PT) Documented hypersensitivity PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus PrecautionsPeriodically evaluate organ (eg, renal, hepatic, hematopoietic) function in prolonged therapy; adjust dose in renal impairment; superinfections may occur with prolonged or repeated antibiotic therapy Metronidazole (Flagyl, Protostat)Imidazole ring-based antibiotic active against various anaerobic bacteria and protozoa. Used in combination with other antimicrobial agents. Not used for C difficile enterocolitis. Adult1 g IV q24h or 250-500 mg PO q6-8h PediatricAdminister as in adults May increase toxicity of anticoagulants, lithium, and phenytoin; cimetidine may increase toxicity; disulfiram reaction possible with alcohol ingestion Documented hypersensitivity PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsAdjust dose in hepatic disease; monitor for seizures and peripheral neuropathy Nafcillin (Unipen, Nafcil, Nallpen)Initial therapy for suspected penicillin G–resistant streptococcal or staphylococcal infections. Initially, use parenteral therapy in severe infections; change to PO therapy as condition warrants. Because of thrombophlebitis, particularly in elderly patients, use parenteral administration only for a short term (1-2 d); change to PO route as clinically indicated. Adult1-2 g IV q4h Pediatric<4 kg (neonates): 10 mg/kg IM bid Associated with warfarin resistance when administered concurrently; effects may decrease with bacteriostatic action of tetracycline derivatives Documented hypersensitivity PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsTo optimize therapy, determine causative organisms and susceptibility; treatment is >10 d to eliminate infection and prevent sequelae (eg, endocarditis, rheumatic fever); obtain cultures after treatment to confirm that infection is eradicated Moxifloxacin (Avelox)Inhibits A subunits of DNA gyrase, inhibiting bacterial DNA replication and transcription. Adult400 mg IV/PO qd Pediatric<18 years: Not recommended Antacids and electrolyte supplements reduce absorption; loop diuretics, probenecid, and cimetidine increase serum levels; NSAIDs enhance CNS-stimulating effect; may increase toxicity of theophylline, caffeine, cyclosporine, and digoxin (monitor digoxin levels); may increase effects of anticoagulants (monitor PT) Documented hypersensitivity; Q-T prolongation or concurrent administration of drugs that cause Q-T prolongation PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus PrecautionsPeriodically evaluate organ (eg, renal, hepatic, hematopoietic) function in prolonged therapy; adjust dose in renal impairment; superinfections may occur with prolonged or repeated antibiotic therapy; may induce seizures in CNS disorder Tigecycline (Tygacil)A glycylcycline antibiotic that is structurally similar to tetracycline antibiotics. Inhibits bacterial protein translation by binding to 30S ribosomal subunit and blocks entry of amino-acyl tRNA molecules in ribosome A site. Indicated for complicated skin and skin structure infections caused by E coli, E faecalis (vancomycin-susceptible isolates only), S aureus (methicillin-susceptible and -resistant isolates), S agalactiae, S anginosus grp (includes S anginosus, S intermedius, S constellatus), S pyogenes, and B fragilis. AdultInfuse each dose over 30-60 min Pediatric<18 years: Not established Coadministration decreases warfarin clearance and increases warfarin Cmax and AUC (monitor aPTT and INR); coadministration of antibiotics with oral contraceptives may decrease contraceptive effect Documented hypersensitivity PregnancyD - Fetal risk shown in humans; use only if benefits outweigh risk to fetus PrecautionsCaution in severe hepatic impairment (reduce dose); may adversely effect tooth development; may permit clostridia overgrowth, resulting in antibiotic-associated colitis; may have adverse effects similar to tetracyclines (eg, photosensitivity, pseudotumor cerebri, pancreatitis, antianabolic action) Ertapenem (Invanz)Bactericidal activity results from inhibition of cell wall synthesis and is mediated through ertapenem binding to penicillin binding proteins. Stable against hydrolysis by various beta-lactamases, including penicillinases, cephalosporinases, and extended spectrum beta-lactamases. Hydrolyzed by metallo-beta-lactamases. Adult1 g qd for 14 d if IV and 7 d if IM; infuse over 30 min if IV Pediatric<3 months: Not established Probenecid may reduce renal clearance of ertapenem and increase half-life but benefit is minimum and does not justify coadministration Documented hypersensitivity to drug or amide type anesthetics PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsPseudomembranous colitis may occur; seizures and CNS adverse reactions may occur; when using with lidocaine to administer intramuscularly, avoid inadvertent injection into blood vessel; decrease dose in renal failure; serious and occasionally fatal hypersensitivity reactions may occur with beta lactams, caution with previous hypersensitivity reactions to penicillin, cephalosporins, other beta lactams, or other allergens; do not mix or coinfuse in same IV line as other medications; do not mix with dextrose-containing diluents Minocycline (Dynacin, Minocin)Treats infections caused by susceptible gram-negative and gram-positive organisms, in addition to infections caused by susceptible Chlamydia, Rickettsia, and Mycoplasma. Adult100 mg PO bid for 5-7 d Pediatric<8 years: Not recommended Bioavailability decreases with antacids containing aluminum, calcium, magnesium, iron, or bismuth subsalicylate; can decrease effects of oral contraceptives, causing breakthrough bleeding and increased risk of pregnancy; tetracyclines can increase hypoprothrombinemic effects of anticoagulants Documented hypersensitivity; severe hepatic dysfunction PregnancyD - Fetal risk shown in humans; use only if benefits outweigh risk to fetus PrecautionsPhotosensitivity may occur with prolonged exposure to sunlight or tanning equipment; reduce dose in renal impairment; consider drug serum level determinations in prolonged therapy; tetracycline use during tooth development (last one-half of pregnancy through age 8 y) can cause permanent discoloration of teeth; Fanconilike syndrome may occur with outdated tetracyclines; hepatitis or lupuslike syndromes may occur Daptomycin (Cubicin)First of new antibiotic class called cyclic lipopeptides. Binds to bacterial membranes and causes rapid membrane potential depolarization, thereby inhibiting protein, DNA, and RNA synthesis, and ultimately causing cell death. AdultCrCl >30 mL/min: 4 mg/kg IV q24h infused over 30 min Pediatric<18 years: Not established |