Infections in surgery Flashcards
Most common bacteria involved in osteomyelitis
Staph aureus (also staph epidermis)
Antibiotic of choice used in SSI prophylaxis in joint replacement surgery?
Cefazolin (2g IV for all patients regardless of weight). Can also use cephalothin.
Given within 60mins of surgery.
Vancomycin should be avoided as it is a broad spectrum antibiotic and has activity against MSR staph aureus. May be used if patient has severe penicillin allergy meaning cephalosporins may be a relative contraindication.
Most appropriate prophylactic antibiotic used in colorectal surgery?
Needs to act against enteric gram negative bacteria.
Use IV metronidazole plus either IV cephalothin or IV cephazolin or IV gentamicin.
How long should SSI prophylactic antibiotics be used for?
Up to 24hrs (less if appropriate)
Why would rifampin be used in patients with surgical hardware/foreign bodies?
rifampin is effective against biofilms
Causes of osteomyelitis?
- Hematogenous route of infection (bacteria spread via blood)
- Contagious spread from surrounding tissues and joint
- Direct inoculation e.g. surgery
Why would diabetes increase risk of osteomyelitis?
Diabetes compromises blood supply to the lower extremities which contributes to impaired immunity and skin healing. This promotes the spread of infection. the fact that patients often have peripheral neuropathy also predisposes them to ulceration which increases risk of osteomyelitis.
Outline empiric antibiotic therapy used in osteomyelitis and septic arthritis
Describe the treatment/management of sepsis
Removal of predisposing factors
- stopping or decreasing immunosuppression
Identifying the course of infection and removing it
- e.g. IV cannula, urinary catheter
Supportive measures
- use of fluids, vasopressors, and corticosteroids in septic shock
Antibiotics:
- should be given as soon as the diagnosis is suspected as delays in therapy have been associated with increased mortality rates. Particular once hypotension develops.
- For suspected MRSA use combination antibiotic therapy using vancomycin plus either a broad spectrum carbapenem, extended range penicillin, or a third generation cephaloporin. MRSA infection is more likely acquired in the hospital setting.
- If a community acquired infection, then IV gentamicin is recommended for empiric treatment. This is because rates of community acquired gram -ve pathogens are low.
Describe the National Early Warning Score for sepsis
- Scoring system based on:
- RR
- SpO2
- Whether patient is requiring oxygen
- Systolic blood pressure
- HR
- consciousness
- temperature
Describe investigation plan for a patient presenting with sepsis
- history and general observation of the patient
- blood cultures:
- taken immediately, and before any antibiotic are given
- take peripheral blood cultures
- aerobic and anaerobic (fill aerobic first)
- serum lactate
- is a marker of stress and may be a marker of a worse prognosis
- raised serum lactate may indicate tissue hypoperfusion
- full blood count
- thrombocytopenia of non-haemorrhagic origin may occur in patients who are severely will with sepsis
- lymphocytopenia may also occur
- may have leukocytosis or leukopenia
- CRP
- reasonably sensitive but not specific
- BGL
- may be elevated
- Urea and electrolytes (including creatinine)
- evaluate for renal dysfunction
- identify sodium, potassium, calcium, magnesium, and chloride abnormalities
- clotting screen
- include prothromin time (PT), partial thromboplastin time (PTT), and fibrinogen
- all may be elevated if the patient has established coagulopathy
- blood gas
- either ABG or VBG to assess metabolic status
Investigations to consider:
- urine analysis
- chest x-ray
- cultures from multiple sources
- lumbar puncture
- computed tomography
- ultrasound
- consider amylase and lipase if pancreatitis is suspected
Describe SIRS criteria
2 or more of the following:
⁃ Temp > 38°C or < 36°C
⁃ Tachycardia > 90bpm or ABG CO2 pressure less than 32mmHg
⁃ Tachypnoea > 20 breaths/min
⁃ White cell count > 12000
Describe the pathophysiology of sepsis
Pathophysiology:
- infection/bacteremia/virus/fungi → inflammatory reaction mediated by the released of cytokines and inflammatory mediators → result in vessel dilation and further release of proinflammatory cytokines (esp. TNFa and IL-1) → capillary leakage and generalised oedema and shift of fluid and albumin into the surrounding tissue → intravascular hypovolemia and activation of the extrinsic coagulation cascade → leading to disseminated intravascular coagulation and microvascular thrombosis → results in tissue ischemia (poor perfusion due to hypovolemia and also microvascular thombi) and widespread cellular injury → leads to organ dysfunction
Also get metabolic acidosis due to increase in lactic acid from tissue ischemia
Describe UTI risk factors:
Predisposing/risk factors:
- being female/having a shorter urethra
- having a structural abnormality that increases urinary stasis:
- BPH
- vesicoureteric reflux
- neurogenic bladder
- urinary tract calculi
- pregnancy → hormonal changes during pregnancy
- postmenopause → decreased estrogen = decreased vaginal lactobacilli and an increase in vaginal pH → increased bacterial colonisation
- predisposing health conditions:
- previous UTI
- diabetes mellitus
- immunosuppression
- sexual intercourse → and not urinating afterwards
- hygiene habits e.g. not wiping front to back
- catheter use
Common causative organisms of a UTI
- E.coli (leading cause)
- staphylococcus saprophyticus (2nd leading cause)
- klebsiella pneumoniae (3rd leading cause
In some cases, viruses or fungi may be the causative organism of a UTI. This is rare though.
Complicated vs uncomplicated UTI
Uncomplicated UTIs: aka an infection in non-pregnant, premenopausal women without further risk factors for infection, treatment failure, or serious outcomes
Complicated UTIs: aka a UTI in patients with risk factors for infection, treatment failure, ore serious outcomes. Patients include:
- male sex
- pregnancy
- postmenopause
- childhood and preadolescence
- significant anatomical or functional abnormalities
- immunosuppression
- renal failure
- diabetes
Also includes healthcare associated UTI’s and also recent use of urinary catheter
Describe antibiotic treatment for pyelonephritis
Empiric therapy includes:
- gentamicin IV (4-5mg/kg q8h) and
- ampicillin (2g IV q6h)
If gentamicin is contraindicated:
- ceftriaxone (1g IV daily)
- cefotaxime (1g IV q8h)
*Gentamicin and ampicillin is preferred because:
- gent is active against a greater percentage of enterobacteriaceae and is more rapidly bactericidal.
- ceftriaxone and cefotaxime do not have activity against pseudomonas aeruginosa or enterococci
- gentamicin with ampicillin are less likely to cause c-difficile
Antibiotic of choice for cellutlitis with systemic features
First line therapy:
- flucloxacillin
Penicillin hypersensitivity:
- cefazolin (2g q8h) -> non severe penicillin reactions
- clindamycin -> severe penicillin reactions
MRSA suspected:
- vancomycin
Antibiotic therapy for sepsis and septic shock from a biliary course or GI source
How septic shock causes lactic acidosis
Causes of lactic acidosis
