MedCompanion

Sepsis (Unknown Source)

Sepsis & Nonfocal

Source: IDMP View on spectrum chart →
Patient + scenario modifiers
Patient
Clinical scenario / source

Annotations only — chart still shows the full chemistry of each drug.

1. Clinical Syndrome

Sepsis (Sepsis-3: SOFA ↑≥2 from baseline with suspected infection) or septic shock (vasopressor requirement to maintain MAP ≥65 + lactate >2 despite fluid resuscitation) without a clear identified source. Healthcare-associated risk factors (recent hospitalization, prior MDRO, indwelling devices) widen empiric coverage — toggle the Recent hospitalization modifier to escalate. Excludes neutropenic fever (separate empirics — see Neutropenic Fever) and sepsis with an obvious source already identified (treat as that syndrome at sepsis severity).

2. Pathogens

Consider the patient: Age, comorbidities (DM, cirrhosis, CKD), immune status (asplenia, neutropenia, HIV, transplant, biologics), exposures (IVDU, indwelling devices, recent procedures), prior antimicrobials (≤90 days raises MDRO risk), past infections (prior MRSA, ESBL, Pseudomonas).

Consider the case: Severity (SOFA, qSOFA, vasopressor requirement, lactate), microbiologic data (Gram stains from potential sources, urine, blood, CSF, joint fluid). Identify the likely source within the first hour — UTI, pneumonia, intra-abdominal, skin, line, CNS — and pivot to source-specific empirics.

Less common

3. Empiric Therapy

TierFirst choiceAlternativesDurationComments
Admitted to ward
  • 2 g · q24h · IV · source-dependent
  • 4.5 g · q6h (extended infusion) · IV
Source-dependent — typically 7–10 days once narrowedStable patient, no MDRO risk factors. Add MRSA coverage per triggers. Source identification + cultures within 1 h of recognition.
Admitted to ICU
  • 25–30 mg/kg load then 15–20 mg/kg · q8–12h · IV

    Target AUC 400–600. Adjust per pharmacy.

  • 4.5 g · q6h (extended infusion) · IV
  • 25–30 mg/kg load · as above · IV
  • 2 g · q8h · IV

    Alternative β-lactam if pip-tazo contraindicated; note ACORN trial nuance on cefepime AKI signal.

Reassess at 48 h; de-escalate aggressively once source/cultures knownSeptic shock or significant illness — empirically cover MRSA + Pseudomonas. Surviving Sepsis: antibiotics within 1 hour of septic shock recognition.
ICU — Pseudomonas risk
  • 25–30 mg/kg load · AUC-guided · IV
  • 2 g · q8h · IV
  • Tobramycin 5–7 mg/kg · q24h · IV

    Or gentamicin. Single anti-pseudomonal agent + aminoglycoside provides double GN coverage in suspected Pseudomonas.

  • load + AUC · — · IV
  • 1 g · q8h (extended infusion) · IV

    If ESBL risk or true PCN allergy.

Reassess at 48 h; narrow to single agent once susceptibilities backStructural lung disease, neutropenia, recent IV abx, prior Pseudomonas isolate, septic shock with risk factors.

Add coverage if:

MRSA coverage
  • Prior MRSA isolate
  • IV drug use
  • Hemodialysis or indwelling line
  • Recent hospitalization
  • Septic shock

Add:

  • 25–30 mg/kg load then 15–20 mg/kg · AUC-guided · IV

    Linezolid alternative if AKI or vanco failure.

Replace with linezolid if vanco intolerant or AKI.

Pseudomonas coverage
  • Recent IV antibiotics ≤90 days
  • Structural lung disease (bronchiectasis, severe COPD, CF)
  • Neutropenia
  • Indwelling device / recent hospitalization
  • Prior Pseudomonas isolate

Add:

  • 2 g · q8h · IV

    Or pip-tazo, or meropenem if ESBL risk.

Replaces ceftriaxone in the base regimen.

Anaerobe coverage
  • Suspected intra-abdominal source
  • Suspected biliary source
  • Suspected aspiration source

Add:

  • 500 mg · q8h · IV

    Not needed if pip-tazo or carbapenem already in regimen.

4. Directed Therapy

Narrow within 48 h based on cultures and source identification:

  • GN bacteremia: ceftriaxone or per susceptibilities; ESBL → ertapenem or meropenem
  • MSSA bacteremia: cefazolin (link to S. aureus bacteremia syndrome)
  • MRSA: continue vancomycin or daptomycin
  • Negative cultures + clinical improvement: de-escalate to source-directed agent and complete the shortest reasonable course
  • No source after 48–72 h reassessment: consider non-bacterial mimics (PE, MI, adrenal insufficiency, drug fever, malignancy)

5. Monitoring

Resolution: lactate clearance (q2–4 h initially), MAP ≥65, urine output, mental status, fever curve, decreasing WBC. Repeat blood cultures if persistent fever or for S. aureus / Candida.

Toxicity: vancomycin AUC + Cr daily; aminoglycoside trough + audiometry; cefepime mental status (neurotoxicity in renal impairment); pip-tazo-vanco AKI risk.

Pearls

Surviving Sepsis 1-hour bundle: lactate, blood cultures BEFORE antibiotics if possible, broad-spectrum antibiotics within 1h of septic shock recognition, fluid resuscitation, vasopressors if persistently hypotensive. Don't miss the source — examine the back/skin for nec fasc, pelvic exam, line sites. Consider adrenal insufficiency (especially HIV/etomidate use). De-escalate aggressively — every day of broad-spectrum is a future C. diff or MDRO.

References