Nosocomial infections in the ICU

Unsurprisingly, this topic appears frequently in the exam. For instance, a broad approach to the topic was interrogated in Question 10 from the first paper of 2002: "Outline the aetiology, clinical manifestations and possible preventative measures for nosocomial infections in Intensive Care."

An ideal reference for the time-rich candidate would be Oh's Manual: Chapter 70  (pp. 724),  "Nosocomial  infections" by James  Hatcher  and  Rishi  H-P  Dhillon. The time-poor reader would probably find their last minute panic better served by this excellent LITFL summary article.

A good article reporting on the epidemiology of nosocomial infection in American ICUs is also available, as well as a detailed paper on preventative measures.

Taken together, these references have been boiled down into a point-form list.

Epidemiology

• Variable prevalence: 3-12%
• ICU differs from the rest of the hospital: we get more pneumonias and blood stream infections, whereas the prevalence of UTIs is roughly the same throughout the wards.
• Hospital acquired infections can add up to 2 weeks of additional ICU stay

Predisposing factors

The following risk factors for nosocomial infections have been identified:

Patient factors	Environmental factors	Organism factors
Critical illness Malnutrition Immunosuppression Open surgical wounds Invasive devices Multiple invasive procedures Prolonged ICU stay Mechanical ventilation Blood transfusion	New or inexprienced staff Poor staff-patient ratio Inadequate infection control Changes in protocols	Surface survival Drug resistance Biofilm formation Adhesive properties Prevalence, colonisation rate

Common organisms

So common are they, tat virtually all of them have at some stage merited a whole CICM fellowship question dedicated to them. Links to relevant sections are offered below.

• MRSA
• Coagulase-negative Staphylococcus (CVC-associated becateraemia)
• VRE
• Pseudomonas
• Acinetobacter
• Stenotrophomonas
• Klebsiella
• Candida (albicans and non-albicans)
• C.difficile

Clinical manifestations

• Broadly speaking, these depend on where the infection is.
• Fever
• Inflammatory marker elevation
• Shock and metabolic acidosis
• Purulent discharge (pulmonary, urinary, or nasal)
• Positive CSF gram stain and culture, decreased level of consciousness

Aetiology of nosocomial infection in ICU:

• Pneumonia: VAP or HAP
• Central line associated bacteraemia
• UTI due to indwelling catheters
• Sinusitis due to nasogastric tubes
• Acalculous cholecystitis due to parenteral nutrition
• Pressure area infections
• Meningitis or ventriculitis due to EVD infection
• C.difficile infections due to broad-spectrum antibiotic use
• Surgical site infections

Preventative measures

Non-specific measures

• Scrupulous handwashing
• Barrier precautions, gloves gowns and masks
• Surveillance for MROs
• Isolation precautions

Specific measures

• Regular oral hygiene
• Regular pressure area care
• Minimisation of the duration of ventilation
• Preventative strategies for VAP (eg. upright positioning)
• Preventative strategies for central line contamination
• Early removal of central lines
• Rationalisation of antibiotics to prevent C.difficile infection
• Control of hyperglycaemia
• Rationalisation of immunosuppressive therapies
• Perioperative antibiotics to prevent wound infection in high-risk patients

Administrative dodgyness

For the bureaucrat within, prevalence statistics and data collection methodology are an opportunity for gentle statistical massage, or just some good old-fashioned bullshit. For instance, it is possible to decrease the apparent rate of VAP by a number of grossly Machiavellian methods. These strategies would be an excellent answer to a hypothetical CICM question:

You are the director of a Level 3 ICU. Hospital governance has pointed out that your unit has a high prevalence of VAP, and asked that you address this issue. However, you have neither the interest nor the time.

Describe your approach to rapidly covering up the true prevalence of VAP in your unit.

• Interpret clinical signs as strictly as possible (eg. demand certain PaO₂/FiO₂ ratio thresholds).
• Interpret chest Xrays as strictly as possible (eg. reject all slightly rotated films).
• Demand consensus between two staff specialist when identifying a VAP (like herding cats).
• Permit staff specialists to "veto" a diagnosis of VAP ("Naaw, relax - thats just oedema").
• Require ridiculous confirmatory tests (eg. only a BAL will do).
• Set an arbitrary (high) quantitative growth threshold for the organisms.
• Exclude certain organisms from the definition ("That's just normal respiratory flora")
• Transfer all patients in need of prolonged mechanical ventilation to another ICU.
• Expand your surveillance to include uncomplicated elective post-op patients.