Hospital-acquired and ventilator-associated pneumonia: Clinical sciences

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Introduction0:00–0:51

Pneumonia is a lung infection that results in inflammation of one or both lungs. Most often, it is caused by bacteria like Streptococcus pneumoniae; or viruses, such as influenza; but rarely, pneumonia can be caused by fungi as well.
Now, based on the setting in which pneumonia develops, we can subdivide it into two main types: community-acquired pneumonia, or CAP for short, which is when a person develops pneumonia outside of a hospital or within 48 hours after hospital admission; and hospital-acquired pneumonia, or HAP, which develops after 48 hours from hospital admission.
Finally, there’s a special subtype of HAP called ventilator-acquired pneumonia, or VAP, which refers to pneumonia that occurs in patients on mechanical ventilation, 48 hours after endotracheal intubation.

History & Physical, Labs, Microbiology, Pulse oximetry, Imaging0:51–5:10

Now, when a patient presents with signs and symptoms suggestive of HAP or VAP, the first step is to obtain a focused history and physical examination and order labs such as CBC and procalcitonin.
You should also use pulse oximetry to check oxygen saturation levels, and collect a blood sample for cultures. Finally, don’t forget to obtain imaging, such as chest x-ray or point-of-care lung ultrasound.
Alright, first, let’s talk about the diagnosis and acute management of patients with HAP. Let's start with History.
These patients usually report a fever, productive cough, pleuritic chest pain, and shortness of breath. Keep in mind that these symptoms develop at least 48 hours after admission.
Now, the physical examination typically reveals elevated temperature, tachypnea, and tachycardia, as well as rales, and decreased breath sounds.
When it comes to labs, they are likely to show elevated WBC count and procalcitonin levels, while pulse oximetry can reveal a drop in oxygen saturation.
Finally, a chest X-ray usually reveals a new lung infiltrate, consolidation, or effusion.Now, if a patient presents with these findings, you can diagnose HAP and start acute management.
This means that you need to provide continuous monitoring of the heart rate, blood pressure, and oxygen saturation. Also, if needed, be sure to provide supplemental oxygen to keep the oxygen saturation above 92%.
The next step is to find the causative organism through microbiological testing. This involves collecting sputum samples, usually by sputum induction.
To do this, the patient should first inhale a saline mist, which will trigger a reflexive cough to release sputum from the lower airways.
Sputum samples are then sent to the laboratory for gram staining and cultures. Additionally, if you suspect MRSA infection, sputum and nasopharyngeal swab samples can be sent for multiplex PCR studies.
Alright, let’s switch gears and talk about the diagnosis and acute management of patients with VAP. Patients with suspected VAP are typically sedated and intubated, so you won’t be able to get the history from them.
So, discuss with other hospital staff and look through the medical chart for information like the time of intubation or a history of purulent secretions.
The physical examination usually reveals signs like fever, tachycardia, rales, and decreased breath sounds. Keep in mind that these signs develop 48 hours after intubation.
Similarly to HAP, labs usually show elevated WBCs and procalcitonin, while oxygen saturation might be low. However, unlike HAP, the imaging of choice for VAP is a point-of-care lung ultrasound because it’s ideal for patients who can’t be easily transported.
Common findings include subpleural consolidation, liver-like echogenicity of the lung, and dynamic air bronchograms. Okay, if a patient presents with these findings, you can diagnose VAP, and you should start acute management immediately.
Just like before, you will need to provide continuous monitoring of their heart rate, blood pressure, and oxygen saturation.
Additionally, be sure to regularly assess ventilatory parameters and adjust the ventilator settings to maximize oxygenation.
Once the acute management is started, your next step is to look for the causative organism through microbiological testing.
Remember that patients with VAP are intubated, therefore the induced sputum technique is not possible. Alternative techniques to collect sputum include bronchoalveolar lavage, or BAL for short, and mini-BAL.
In BAL, a bronchoscope is inserted through the trachea into the lungs to reach a terminal segment of the affected lung lobe, inject sterile saline, and then suction a sample.
On the other hand, in mini-BAL, a telescoping catheter is inserted through the endotracheal tube into the lower airways to obtain a sample.
Regardless of the collection technique, you will send the sputum samples to the laboratory for gram staining, cultures, and possibly multiplex PCR studies if MRSA is suspected.

Assessing risk for MDR pathogens5:10–5:43

Alright, after acute management, the next steps are very similar for HAP and VAP. You should first assess if there are any risk factors for a multidrug resistant, or MDR pathogen.
One of the most important risk factors is use of IV antibiotics in the preceding 90 days. Additional risk factors specific to VAP include a hospital stay of 5 or more days, acute renal replacement therapy, or ARDS prior to VAP, as well as septic shock at the time of VAP.
Now, let’s focus on individuals that are at risk for infection with MDR pathogens. These patients have one or more risk factors and require an IV empiric antibiotic dual-therapy.

Empiric treatment5:43–8:30

Typically, this includes a combination of an antipseudomonal beta-lactam, such as piperacillin-tazobactam or cefepime; and a non-beta-lactam, such as a respiratory fluoroquinolone, like levofloxacin, or an aminoglycoside, like gentamicin.
In HAP, additional coverage for MRSA with vancomycin or linezolid depends on if the hospital has a prevalence of MRSA, or if the prevalence is unknown, or if patients have high risk of mortality or had IV antibiotics in the preceding 90 days.
In the case of VAP, MRSA coverage is required only if there's high or unknown prevalence. On the other hand, treatment for patients without risk factors for infection with MDR pathogens involves IV antibiotic monotherapy, usually with piperacillin-tazobactam, cefepime, a respiratory fluoroquinolone, like levofloxacin, or a carbapenem.Alright, after the empiric treatment has started, you should follow up and assess the microbiological testing ordered earlier.
If testing results are positive and reveal the causative pathogen, you can tailor antibiotics to maximize coverage against it and eliminate unnecessary drugs.
Next, wait 48 hours and evaluate the patient’s response to tailored antibiotics by assessing their overall clinical status, obtaining new imaging for comparison, or following procalcitonin levels.
Procalcitonin levels serve as a good biomarker during the treatment of bacterial infection because the levels rise with the initial infection and drop with resolution.
Now, if your patient is improving and showing adequate response, complete the course of IV antibiotics. However, if they’re not showing adequate response, you need to assess them for pneumonia-related complications, like the development of an empyema or septic shock, or even consider an alternative diagnosis.
Alright, let’s go back to microbiological testing. Sometimes, the results might come back negative.
In this case, you should assess the patient’s response to empiric antibiotics 48 hours after starting them. This is where PCT is especially useful because, if it drops, it means the infection is resolving and your empiric antibiotic therapy is effective.
So, if the patient is improving and showing adequate response, complete the current course of antibiotics for 7 days. On the other hand, if there’s inadequate response to therapy, you should consider pneumonia-related complications or some alternative diagnosis.Alright, as a quick recap… HAP refers to pneumonia that develops after 48 hours from hospital admission, while VAP refers to pneumonia that develops in patients on mechanical ventilation, 48 hours after endotracheal intubation.

Review8:30–10:09

To make a diagnosis, you’ll need to obtain H&P, order labs, such as CBC and procalcitonin; check pulse oximetry; collect blood samples for culturing and staining; and obtain imaging.
Once you make the diagnosis, collect sputum samples for gram stain and culture, as well as possibly PCR if MRSA is suspected.
Then evaluate the patient’s risk for infection with MDR pathogens. Patients with 1 or more risk factors require IV empiric antibiotic dual-therapy with an antipseudomonal beta-lactam and a non-beta-lactam, as well as MRSA coverage if there's high or unknown prevalence.
Those with no risk factors are treated with IV antibiotic monotherapy. If microbiological testing results are positive, tailor antibiotics and wait 48 hours to evaluate the patient's response.
Patients that improve should complete their course of antibiotics, while those that don’t improve should be evaluated for pneumonia-related complications or an alternative diagnosis.
On the other hand, if microbiological testing results are negative, continue empiric antibiotics and evaluate the patient’s response after 48 hours.
If the patient improves, complete the current course of antibiotics for 7 days. But, if they don’t improve, consider pneumonia-related complications or some alternative diagnosis.