NU657 Unit 10 Case Study, Legionella Pneumonia Example

A Hotel Stay, Three Days of Diarrhea and a Sodium of 128: A Comprehensive Case Study of Severe Legionella Pneumonia Across Nine ICU Days in a 64-Year-Old Man

[Student Name]

Purdue University Global

NU657: AGACNP Critical Care Management Clinical

Unit 10 Comprehensive Case Study

[Instructor Name]

[Date]

The patient is composite; values, doses and dates are bracketed.

Timeline

1. [Day 1]: emergency department at [11:00]; ICU admission at [15:30]; urinary antigen positive at [22:10].

2. [Day 2]: intubated at [04:40] for worsening hypoxemia.

3. [Day 3]: creatinine peaks; creatine kinase peaks.

4. [Day 4]: first positive delirium screen during a sedation pause.

5. [Day 6]: extubated after a spontaneous breathing trial.

6. [Day 8]: delirium screen negative for [48] hours.

7. [Day 9]: transferred to a medical floor.

Presentation and the ICU Decision

Mr. [G.] is a [64]-year-old retired plumber with hypertension and type 2 diabetes who smokes [20] cigarettes a day. He returned [five] days before admission from a [four]-night stay at a conference hotel. He developed fever, dry cough and muscle aches, then [three] days of watery diarrhea, and his wife brought him in because he had become confused.

In the emergency department: temperature [39.8] C, respiratory rate [32], pressure [96/58] after [two] liters of fluid, saturation [88] percent on room air, PaO2 [72] mmHg on [40] percent oxygen by venturi mask, giving a ratio of [180]. Chest radiograph: consolidation in the right lower and middle lobes and the left lower lobe. Blood urea nitrogen [31] mg/dL, sodium [128] mEq/L, creatinine [1.8] mg/dL, platelets [142,000].

The decision was whether he needed the ICU. The ATS/IDSA guideline defines severe community-acquired pneumonia by two major criteria, septic shock needing vasopressors or respiratory failure needing mechanical ventilation, or by three or more minor criteria, and recommends direct admission to intensive care for these patients (Metlay et al., 2019). He had no major criterion at [15:00], but he had five minor ones: respiratory rate of 30 or more, a ratio of 250 or less, multilobar infiltrates, confusion, and a urea nitrogen of 20 or more. Counting the criteria turned an impression that he was sick into a documented reason for an ICU bed, before either major criterion arrived.

Decision: ICU admission. Result: he met a major criterion within [14] hours, when he was intubated, which supports the decision.

Diagnostics

The guideline recommends blood and sputum cultures and urinary antigen testing for Legionella in severe pneumonia (Metlay et al., 2019). The hotel stay, diarrhea, confusion, high fever and low sodium together raised the suspicion of Legionella, a combination that reviews of the disease describe as suggestive though not specific (Cunha et al., 2016). The Legionella urinary antigen was positive at [22:10]. The test detects Legionella pneumophila serogroup [1], the most common cause, but can miss other serogroups and species, so a sputum culture on selective media was also sent, and later grew L. pneumophila serogroup [1].

Creatine kinase was [4,900] U/L on arrival and rose to [11,200] on [day 3]. Legionella is known to cause muscle breakdown, which became important for his kidneys.

Antimicrobial Therapy

Decision: ceftriaxone with azithromycin from the emergency department, the combination the guideline recommends for severe pneumonia without risk factors for resistant organisms (Metlay et al., 2019). Once the antigen was positive and a respiratory viral panel was negative, the question became whether to narrow.

On [day 3], with the sputum culture growing Legionella and no other organism, and blood cultures negative, ceftriaxone was stopped and azithromycin continued alone at [500] mg daily. A fluoroquinolone was considered, since both drug classes treat Legionella, but azithromycin had already been started and was working, and his corrected QT interval of [438] milliseconds allowed it. The planned total course was [ten] days because of the severity of his illness.

Result: fever resolved on [day 4], and oxygen requirements improved from [day 4] onward.

Respiratory Failure and Intubation

At [03:30] on [day 2], his oxygen requirement on high-flow nasal oxygen rose to [70] percent, his respiratory rate stayed above [35], and he was tiring. He was intubated at [04:40]. His PaO2 to FiO2 ratio after intubation was [128] with bilateral infiltrates, and his echocardiogram showed normal left ventricular function, so he met criteria for moderate ARDS. Tidal volume was set at [6] mL/kg of predicted body weight, [420] mL for his height of [175] cm, with plateau pressure kept below [30] and PEEP set from the lower PEEP table. The ratio never fell below [110], and prone positioning was not needed.

Acute Kidney Injury

Decision: identify the cause. His creatinine rose from [1.8] on arrival to a peak of [3.1] on [day 3]. His baseline was [1.1] mg/dL in his primary care records, so the peak was [2.8] times baseline, KDIGO stage 2 by creatinine (Khwaja, 2012). Urine output never fell below [0.5] mL/kg per hour for more than [six] hours.

Three causes competed. Sepsis with hypotension was present on [day 1]. Rhabdomyolysis was present, with a creatine kinase peaking at [11,200] and dark urine positive for blood without red cells. Contrast was not a factor, since no contrast study was done. The study attributes the injury mainly to sepsis with a contribution from muscle breakdown, and treatment addressed both: fluids to maintain urine output, avoidance of nephrotoxins, and daily creatine kinase. He did not need dialysis, and his creatinine returned to [1.3] by [day 8].

Delirium

Decision: prevent and treat delirium with the ICU Liberation bundle. On [day 4], during a daily sedation pause, his CAM-ICU was positive; he was agitated and could not follow a sequence of commands. The team applied the ABCDEF bundle: daily awakening and breathing trials, analgesia first, choice of sedation that avoids benzodiazepines, delirium screening, early mobility and family engagement. In a collaborative of more than fifteen thousand adults, higher compliance with the bundle was associated with lower mortality and fewer days of delirium and coma (Pun et al., 2019).

His propofol was reduced to the lowest dose that allowed safe ventilation, and dexmedetomidine was used for agitation from [day 5]. His wife visited daily, bringing his glasses and hearing aids. Physical therapy began sitting him on the edge of the bed on [day 5]. Result: the screen was positive for [four] days and negative from [day 7], and he remembered little of the ICU stay.

Liberation and Transfer

He passed a spontaneous breathing trial on [day 6] and was extubated to [four] liters by nasal cannula. He walked [30] meters with a walker on [day 8]. He was transferred to a medical floor on [day 9], on oxygen at [two] liters, to complete his antibiotics and begin rehabilitation.

Public Health and Lessons

Legionnaires' disease is reportable, and the case was reported to the county health department on [day 2]. The hotel was already under investigation after a second guest from the same conference was admitted elsewhere.

Three lessons follow from the case. First, counting the severity criteria made the ICU decision early and defensible. Second, a travel history and a low sodium in a patient with pneumonia should prompt a Legionella test early rather than late, because the choice of antibiotic depends on it. Third, kidney injury in a patient with Legionella deserves a creatine kinase, because rhabdomyolysis changes how closely the kidneys and fluids need to be watched.

References

Cunha, B. A., Burillo, A., & Bouza, E. (2016). Legionnaires' disease. The Lancet, 387(10016), 376-385. https://doi.org/10.1016/S0140-6736(15)60078-2

Khwaja, A. (2012). KDIGO clinical practice guidelines for acute kidney injury. Nephron Clinical Practice, 120(4), c179-c184. https://doi.org/10.1159/000339789

Metlay, J. P., Waterer, G. W., Long, A. C., Anzueto, A., Brozek, J., Crothers, K., Cooley, L. A., Dean, N. C., Fine, M. J., Flanders, S. A., Griffin, M. R., Metersky, M. L., Musher, D. M., Restrepo, M. I., & Whitney, C. G. (2019). Diagnosis and treatment of adults with community-acquired pneumonia: An official clinical practice guideline of the American Thoracic Society and Infectious Diseases Society of America. American Journal of Respiratory and Critical Care Medicine, 200(7), e45-e67. https://doi.org/10.1164/rccm.201908-1581ST

Pun, B. T., Balas, M. C., Barnes-Daly, M. A., Thompson, J. L., Aldrich, J. M., Barr, J., Byrum, D., Carson, S. S., Devlin, J. W., Engel, H. J., Esbrook, C. L., Hargett, K. D., Harmon, L., Hielsberg, C., Jackson, J. C., Kelly, T. L., Kumar, V., Millner, L., Morse, A., . . . Ely, E. W. (2019). Caring for critically ill patients with the ABCDEF bundle: Results of the ICU Liberation Collaborative in over 15,000 adults. Critical Care Medicine, 47(1), 3-14. https://doi.org/10.1097/CCM.0000000000003482