A 50-year-old man with motor neurone disease presents to hospital with respiratory distress following two (2) days of fever and malaise. He is alert and anxious, and an arterial blood gas performed on oxygen (8L/min semi-rigid mask) revealed PaO2 45 mmHg, PaCO2 65 mmHg, pH 7.36 and HCO3 36 mmol/L. He has used a motorised wheelchair for three (3) years but continues to work as an accountant. His attentive wife states that they have discussed mechanical ventilation and are keen for him to receive full Intensive Care support.
• On day 7 of his admission he become febrile, develops a leukocytosis and a chest x-ray shows a new infiltrate in his left lower lobe. Discuss the investigation and management of this problem.
Unfortunately nosocomial pneumonia is a common sequelae of mechanical ventilation after 7 days. A standard approach should be considered, which must include some culturing of secretions (tracheal aspirates, or more invasive eg. bronchoscopic lavage or protected brush). Gram stain may provide quantitative information of potential pathogens, as may quantitative cultures. Antibiotics should be introduced if bacterial aetiology suspected, and should be appropriate to local factors (including usual bacterial sensitivities, previous antibiotic use and unit protocols) but should include cover for MRSA and resistant gram negatives for a specified period of time (eg. 3 days and review). Plan for review of antibiotics should be discussed. Differential diagnosis includes other causes of WCC/temperature elevation (eg. line sepsis, UTI, sinus infection, pulmonary embolus, myocardial infarction etc.) and other causes of infiltrates (eg. collapse/atelectasis, pulmonary oedema and pulmonary embolus) and each may require specific investigation and treatment depending on other clinical information. This event provides another opportunity to revisit the direction of management when necessary discussion regarding developments occurs with wife and family.
This motor neuron disease patient has VAP, by the standard definition (any pneumonia which develops after 48 hrs on a ventilator can be called VAP).
A summary of ventilator-associated pneumonia is available in the Required Reading section.
Thus, a structured answer would look like this:
Exclusion of other sources of fever
- Culture of the urine and a U/A
- Examination of the abdomen, ultrasound of the gallbladder
- Examination ± CT of the sinuses
- Attention to central venous catheters
Investigations of VAP
- Tracheal aspirate culture, BAL sample or PSB (protected specimen brush) - its all the same, it seems the method of sampling really does not influence survival.
- Blood cultures should be collected, but one does so with the knowledge that the organism cultured from the blood may not represent the organism causing the VAP.
- Broad spectrum antibiotics until a pathogen is isolated - which should include cover for multiresistant organisms
- Mechanical ventilation with small amount of PEEP, so as not to cause shunting of blood though the pus-filld lung
- Suctioning of the secretions to improve clearance
- Upright (45°) positioning to prevent further VAP
- Strategies such as chlorhexidine mouthwashes and selective digestive tract decontamination are controversial
Ruíz, Mauricio, et al. "Noninvasive versus invasive microbial investigation in ventilator-associated pneumonia: evaluation of outcome." American journal of respiratory and critical care medicine 162.1 (2000): 119-125.
Luna, Carlos M., et al. "Blood cultures have limited value in predicting severity of illness and as a diagnostic tool in ventilator-associated pneumonia." CHEST Journal 116.4 (1999): 1075-1084.
Kollef, Marin H., and Suzanne Ward. "The influence of mini-BAL cultures on patient outcomes implications for the antibiotic management of ventilator-associated pneumonia." CHEST Journal 113.2 (1998): 412-420.
Craven, Donald E., and Karin I. Hjalmarson. "Ventilator-associated tracheobronchitis and pneumonia: thinking outside the box." Clinical Infectious Diseases 51.Supplement 1 (2010): S59-S66.