Clinical approach

1. Persistent or recurrent infection from the illness that caused the prior admission
2. A new infection, possibly healthcare-associated after hospitalization
3. A non-infectious cause of the previous severe breathlessness, now with systemic symptoms

Immediate assessment

• ABCDE assessment and calculate NEWS2
• Temperature, pulse, respiratory rate, BP, SpO₂, mental status, capillary refill, urine output
• Examine:
  • Chest: crackles, wheeze, reduced breath sounds, signs of pleural effusion
  • Heart: JVP, edema, new murmur, signs of heart failure
  • Abdomen and renal angle tenderness
  • Skin, IV access sites, wounds, pressure sores
  • Neurologic state, rash, focal infection signs

Investigations and why they are needed

1. Baseline and sepsis investigations

• CBC with differential and platelet count: leukocytosis/leukopenia, anemia, thrombocytopenia.
• CRP and possibly procalcitonin: support inflammation/infection and help trend response, but do not diagnose sepsis alone.
• RFT, electrolytes, glucose, LFT, serum albumin: dehydration, acute kidney injury, electrolyte cause of weakness, hepatic dysfunction, and organ involvement.
• Serum lactate: tissue hypoperfusion and severity assessment in suspected sepsis.
• ABG or VBG with oxygen saturation: hypoxemia, hypercapnia, acidosis.
• Coagulation profile: especially if septic, very unwell, liver dysfunction, or thrombocytopenia.

2. Microbiological tests

• Two sets of blood cultures from separate sites
• Urinalysis and urine culture
• Sputum Gram stain and culture/sensitivity, if productive cough or abnormal chest imaging
• Respiratory viral PCR: SARS-CoV-2, influenza, RSV as locally indicated
• Consider Legionella and pneumococcal urinary antigen if moderate to severe pneumonia
• If chronic cough, weight loss, night sweats, persistent infiltrates, diabetes, or high TB prevalence:
  • Sputum AFB smear/culture
  • NAAT/CBNAAT for tuberculosis
• If line-associated infection is possible, culture from line and peripheral blood as per local protocol.

3. Respiratory and cardiac evaluation

• Chest X-ray, comparison with prior film: persistent or new consolidation, edema, pleural effusion, cavitation, mass.
• Bedside lung ultrasound: consolidation, pleural effusion, pulmonary edema, pneumothorax.
• HRCT chest if X-ray is non-diagnostic or there is suspected abscess, empyema, bronchiectasis, malignancy, interstitial disease, or unresolved pneumonia.
• ECG: arrhythmia, ischemia, right-heart strain.
• Troponin and BNP/NT-proBNP if heart failure, ischemia, myocarditis, or demand injury is possible.
• Echocardiography if clinical heart failure, new murmur, persistent fever with bacteremia, or suspected infective endocarditis.
• CT pulmonary angiography if pulmonary embolism is likely: sudden/recurrent dyspnea, pleuritic pain, hemoptysis, tachycardia, unilateral leg swelling, or recent immobilization/hospitalization. D-dimer is useful only when pretest probability is low/intermediate.

4. Tests guided by local epidemiology and examination

• Peripheral smear/rapid antigen test for malaria, if relevant exposure or endemic setting
• Dengue, enteric fever, leptospirosis tests only if clinical and epidemiological features support them
• HbA1c and HIV testing, with consent, if recurrent or unusually severe infection
• Stool tests only if diarrhea
• Autoimmune panel only if imaging and clinical findings suggest inflammatory lung disease or vasculitis

Differential diagnosis

Most likely and urgent

1. Sepsis due to persistent, recurrent, or new bacterial infection
   • Recent pneumonia may not have resolved.
   • Possible resistant or healthcare-associated organism after recent hospitalization.
   • Search for non-pulmonary sources: UTI/pyelonephritis, catheter-related infection, biliary infection, skin/soft-tissue infection.
   • Rigors are particularly concerning for bacteremia.
2. Recurrent or complicated pneumonia
   • Inadequate initial resolution, aspiration pneumonia, post-obstructive pneumonia.
   • Complications: parapneumonic effusion, empyema, lung abscess, bronchiectasis.
   • May explain prior severe breathlessness plus current constitutional symptoms.
3. Tuberculosis
   • Consider especially with persistent fever, anorexia, weight loss, night sweats, cough, hemoptysis, upper-zone infiltrates/cavities, or residence in a high-prevalence area.
   • Can coexist with or be mistaken for nonresolving bacterial pneumonia.
4. Acute decompensated heart failure
   • The prior severe breathlessness could have been pulmonary edema rather than infection.
   • Weakness and appetite loss may occur with poor cardiac output; fever/rigors would suggest a concurrent infection or less commonly endocarditis.
5. Infective endocarditis
   • Consider with persistent fever/rigors, positive blood cultures, new murmur, embolic features, previous valve disease, indwelling line, or recent invasive procedures.
   • It can precipitate heart failure and breathlessness.
6. Pulmonary embolism
   • Recent admission and reduced mobility are risk factors.
   • Usually does not cause rigors, so it is less likely to explain the whole syndrome alone, but it must not be missed if dyspnea recurs or there is pleuritic chest pain/tachycardia.

Other important possibilities

1. Viral infection or post-viral illness, including COVID-19 or influenza
2. Anemia, especially severe anemia, causing weakness and breathlessness
3. Electrolyte disorder, acute kidney injury, hypoglycemia, thyroid disease, or adrenal insufficiency
4. Malignancy with post-obstructive pneumonia, particularly if chest imaging fails to clear or there is weight loss/hemoptysis
5. Drug-related adverse effect, including antibiotic-associated diarrhea/dehydration or medication-induced renal/electrolyte disturbance

Working impression

Possible sepsis due to unresolved/recurrent lower respiratory tract infection or another occult infection, in a patient recently hospitalized with severe dyspnea.

Acute febrile systemic illness: generalized weakness + shivering/rigors + anorexia for 1 week.

Revised priority investigations

At bedside

• Temperature chart
• Pulse, BP, respiratory rate, SpO₂, mental status, urine output
• Look for dehydration, pallor, icterus, rash, lymph nodes
• Full examination for infection source:
  • Chest examination, even if no dyspnea
  • Urinary symptoms and renal-angle tenderness
  • Abdominal tenderness/hepatosplenomegaly
  • Skin/wounds/IV-line sites
  • Heart murmur or peripheral signs of endocarditis
  • Joint, spine, dental, ENT examination

First-line laboratory tests

1. CBC with differential, platelet count, peripheral smear
   • Leukocytosis/leukopenia, anemia, thrombocytopenia
   • Smear can suggest malaria, hemolysis, hematologic malignancy.
2. CRP, ESR, and procalcitonin if available
   • Supports infection/inflammation and gives a baseline for trend.
3. Renal function, electrolytes, glucose, liver function tests, albumin
   • Dehydration, AKI, electrolyte cause of weakness, hepatitis, sepsis-related organ dysfunction.
4. Serum lactate
   • Especially if tachycardia, hypotension, altered sensorium, cold peripheries, oliguria, or clinical concern for sepsis.
5. Urine routine/microscopy and urine culture
   • UTI or pyelonephritis can present with fever/rigors and weakness even without prominent urinary symptoms.
6. Two sets of blood cultures from separate peripheral venipuncture sites
   • Take before antibiotics if this does not delay urgent treatment.
   • Particularly important with true rigors, high fever, hypotension, or a murmur.
7. Blood gas only if low SpO₂, abnormal respiratory rate, shock, acidosis, or altered sensorium.

Infection tests guided by history and local prevalence

• SARS-CoV-2/influenza testing if respiratory symptoms or local circulation
• Malaria rapid test and peripheral smear if endemic-area residence/travel, cyclical fever, thrombocytopenia, or splenomegaly
• Dengue testing if compatible epidemiology, myalgia, rash, leukopenia/thrombocytopenia
• Typhoid testing or blood culture if prolonged fever with abdominal symptoms or relevant exposure
• TB testing if chronic cough, weight loss, night sweats, contact history, persistent abnormal chest X-ray
• HIV test, with consent, if severe/recurrent/unusual infection or unexplained weight loss

Imaging and cardiac tests

• Chest X-ray: reasonable despite no current dyspnea because of the severe respiratory admission one month ago. It can show unresolved pneumonia, pleural effusion, TB, mass, or residual edema.
• ECG: if fever is accompanied by tachycardia, palpitations, chest symptoms, or electrolyte abnormalities.
• Echocardiography: not routine initially, but indicated if blood cultures are positive, there is a new murmur, persistent fever, embolic signs, or concern for infective endocarditis.
• Ultrasound abdomen if abdominal findings, abnormal LFTs, suspected renal/biliary infection, or splenomegaly.
• CT chest/CT pulmonary angiography is not first-line now unless she develops recurrent dyspnea, hypoxia, pleuritic chest pain, hemoptysis, or an abnormal chest X-ray.

Differential diagnosis, now ranked

1. Acute bacterial infection with possible bacteremia/sepsis

• UTI/pyelonephritis
• Persistent or recurrent pneumonia, including healthcare-associated infection
• Biliary or intra-abdominal infection
• Skin/soft tissue or IV-line-associated infection
• Infective endocarditis

2. Viral febrile illness

3. Malaria or other endemic febrile illness

4. Persistent or occult pulmonary infection

• Non-resolving pneumonia
• Lung abscess
• Pleural infection
• Tuberculosis

5. Infective endocarditis

6. Anemia or metabolic illness contributing to weakness

• Severe anemia
• Hyponatremia/hypokalemia
• Acute kidney injury/uremia
• Hypoglycemia or uncontrolled diabetes
• Thyroid disease
• Liver disease

7. Drug-related illness

Practical working diagnosis

Acute febrile illness with rigors and constitutional symptoms, with possible bacteremia/sepsis. Source not yet identified. Prior respiratory hospitalization requires exclusion of unresolved pulmonary infection and infective endocarditis.