Question 1c

Created on Tue, 06/02/2015 - 14:02
Last updated on Sun, 09/06/2015 - 06:46
Pass rate: 66%
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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.

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College Answer

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.

Discussion

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

Management:

  • 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

References

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.