In this article a pharmacist with advanced training and experience in infectious diseases discusses five things pharmacists should know about ventilator associated pneumonia (VAP)
Authored By: Lucia Rose, PharmD, BCIDP
Article Posted 1 December 2022
It was the fall of 2009; I was a proud PGY-1 resident at UMass Medical Center rounding with a large team in the ICU. The presenting fellow systematically reviewed each patient and at the beginning of each case, stated “head of the bed is elevated at 30 degrees.” This was language I had never heard in pharmacy school. I wondered what was the significance of this statement and why was he spending just as much time on the antibiotic regimen (i.e., my time to shine) as he was on head position and oral hygiene? Of course, I quickly learned that this was all in place to prevent the dreaded, ventilator associated pneumonia (aka VAP).
Let’s start by simply defining this disease: VAP is pneumonia that occurs in patients that have been on mechanical ventilation for more than 48 hours. It is associated with increased morbidity, mortality, length of stay (LOS), and healthcare cost. Approximately 5-15% of patients requiring mechanical ventilation will develop VAP during their hospitalization. Clinical, microbiologic, and radiologic evidence should be used to make the diagnosis, however, subjectivity can lead to potential for misdiagnosis and subsequent unnecessary antibiotic therapy. ICU collaboration with infectious diseases and/or an antibiotic stewardship program (ASP) can assist in management as patients with VAP are vulnerable to receiving broad spectrum antibiotics for prolonged durations.
Ideally, respiratory tract sampling should be obtained prior to antibiotic initiation, however, if a delay is expected, prompt empiric antimicrobial therapy targeting Gram-positive and Gram-negative bacteria is recommended. The specific method of obtaining a respiratory culture is controversial as some experts favor invasive versus noninvasive sampling. While invasive sampling such as bronchoscopy is more sensitive and specific for identifying a true pathogen, some patients are unable to undergo this procedure. Additionally, although quantitative cultures are more accurate, they are more costly and time consuming compared to semiquantitative or qualitative cultures.
While prevention strategies for VAP are recommended, they will not be the focus of this article as these interventions are not generally managed by pharmacists. For more information on prevention, please review the comprehensive approach that has been proposed and listed in the IDSA/SHEA guidelines.
Here are things pharmacists should know about ventilator associated pneumonia, as explored through five important questions…
Question #1: What is the difference between tracheobronchitis and VAP?
While distinguishing these two syndromes in clinical practice can be a major challenge, a key point is that patients with tracheobronchitis DO NOT have radiologic signs of pneumonia.
Identification of new or progressive infiltrates or air bronchograms are critical for the diagnosis of VAP since fever and respiratory distress are relatively common in intubated patients. Patients with tracheobronchitis may still have positive sputum cultures, fever, and respiratory distress; all of which often trigger antibiotic initiation in an ICU setting. Although tracheobronchitis can increase LOS and time on the ventilator, increased mortality has not been shown.
Most importantly, antibiotics are generally not recommended in patients diagnosed with tracheobronchitis.
Question #2: Which bacteria should be targeted when initiating empiric therapy?
Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacterales are the most commonly recovered bacteria in patients with VAP. Per IDSA/ATS guidelines, the necessity to cover MRSA depends on if the patient has a risk factor for multidrug resistant pathogens, if MRSA rates in the ICU are >10-20% of S. aureus, or if MRSA rates are unknown. Based on large surveillance data, most regions in the United States have MRSA rates above 30%, therefore, most hospital guidelines in this country likely include an anti-MRSA agent as part of empiric therapy for VAP.
Question #3: What empiric antibiotic regimens are appropriate for VAP?
The ATS/IDSA guidelines recommend linezolid or vancomycin PLUS an antipseudomonal beta-lactam. For patients with serious IgE mediated beta-lactam allergies, aztreonam can be considered, however rates of resistance among Gram negative rods (GNR) are higher than beta-lactams and caution should be taken if using this agent.
Although double antipseudomonal coverage is recommended in the guidelines, it is based on a low level of evidence and the need for this is controversial. A second agent may be needed only if resistance is >10% to the primary GN agent. Hospital antibiograms and antimicrobial stewardship programs should dictate the need for this practice. If a second Gram-negative agent is chosen, aminoglycosides retain better susceptibilities against most GNR and have less collateral damage compared to fluoroquinolones.
To note, use of an ICU specific antibiogram should be utilized when choosing an empiric treatment regimen for VAP, when data are available and reliable.
Question #4: Can MRSA nasal swabs be reliably used to de-escalate anti-MRSA therapy?
Although evidence suggests safe de-escalation of anti-MRSA therapy based on negative MRSA nasal screening, data specific for VAP is lacking. However, if a patient has a negative MRSA nasal screen and MRSA is NOT recovered from respiratory samples, anti-MRSA therapy can likely be discontinued.
Additionally, MRSA recovered in patients with diagnosed VAP may represent upper airway colonization and not actual lower lung causative pathogens. For this reason, some hospital VAP empiric treatments may exclude anti-MRSA therapy particularly if institutional data is supportive of this.
Question #5: How long should VAP be treated?
Generally, a 7-day course is recommended, however in select patients who recover quickly, a 5-day course may be sufficient.
The REGARD-VAP trial is ongoing and will hopefully address whether a shorter duration (3-5 days) is non-inferior to 8 days or longer.
Readers may be interested in this resource for determining reasonable durations of therapy for antimicrobial therapy.
Useful references
ABOUT THE AUTHOR
Dr. Lucia Rose earned her BS in General Science from Pennsylvania State University in State College, PA and her Doctor of Pharmacy Degree from Massachusetts College of Pharmacy in Worcester, MA. She completed a PGY-1 Pharmacy Practice residency at University of Massachusetts Medical Center and a PGY-2 Infectious Diseases Pharmacotherapy Residency at The Brooklyn Hospital Center.
Post terminal training Dr. Rose practiced for 10 years as an infectious diseases pharmacist in the academic clinical setting then more recently transitioned to industry in May of 2021. She is now a medical science director at Paratek pharmaceuticals for the Mid-Atlantic region. She lives in Philadelphia PA with her husband and two children.
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