# Clinical Cases: Infectious Emergencies

## Case 1: Septic Shock - Early Recognition Saves Lives

### Patient Demographics
- **Age:** 64 years
- **Sex:** Male
- **Occupation:** Retired factory worker

### Chief Complaint
"I feel terrible and can't stop shaking."

### History of Present Illness
A 64-year-old male presents with 2 days of progressive malaise, chills, and productive cough. He developed fever and rigors this morning. His wife reports he has been confused and "not acting right" since waking. He has been urinating frequently over the past week with some burning. He has type 2 diabetes and admits his glucose has been poorly controlled recently.

### Initial Assessment

**ESI Level:** 1 - Septic shock with hypotension

**First Impression:**
- Appearance: Toxic-appearing, rigors, confused
- Work of breathing: Tachypneic
- Circulation: Mottled extremities

**Vital Signs:**
- Heart rate: 118 bpm
- Blood pressure: 82/48 mmHg
- Respiratory rate: 26 breaths/min
- SpO2: 91% on room air
- Temperature: 39.8C (103.6F)
- GCS: 13 (E3V4M6)

### Sepsis-3 Criteria Assessment

**qSOFA Score (Quick SOFA):**
- Altered mental status: YES (+1)
- Respiratory rate ≥22: YES (+1)
- Systolic BP ≤100: YES (+1)
- **Total: 3/3** (high risk for poor outcome)

**SOFA Criteria:**
- Sepsis = Life-threatening organ dysfunction due to infection
- SOFA score ≥2 indicates organ dysfunction

**Septic Shock Definition:**
- Sepsis PLUS
- Vasopressors needed to maintain MAP ≥65 mmHg PLUS
- Lactate >2 mmol/L despite adequate fluid resuscitation

### Primary Survey

**Airway:** Patent, speaking (confused)
**Breathing:** Tachypneic, crackles right base
**Circulation:** Hypotensive, tachycardic, mottled, delayed cap refill (5 seconds)
**Disability:** Confused (oriented to person only), GCS 13
**Exposure:** Warm peripherally (warm shock early), no rashes

### Resuscitation - Sepsis Bundle (Hour-1)

**Immediate Interventions:**
1. Measure lactate: **4.8 mmol/L** (elevated)
2. Obtain blood cultures BEFORE antibiotics
3. Administer broad-spectrum antibiotics
4. Begin fluid resuscitation: 30 mL/kg crystalloid

**Antibiotics (within 1 hour):**
- Piperacillin-tazobactam 4.5g IV (covers respiratory and urinary pathogens)
- Vancomycin 25 mg/kg IV (MRSA coverage given severity)

**Fluid Resuscitation:**
- 30 mL/kg = 2.4L (80kg patient)
- Given over 30-60 minutes
- Reassess after bolus

### Secondary Survey

**SAMPLE History:**
- Symptoms: Fever, chills, cough, urinary symptoms, confusion
- Allergies: Penicillin (rash only - can use piperacillin-tazobactam with monitoring)
- Medications: Metformin, lisinopril, atorvastatin
- PMH: Type 2 diabetes (poorly controlled), hypertension, BPH
- Last Meal: Yesterday (poor appetite)
- Events: Progressive illness over 2 days

**Physical Examination:**

**HEENT:** Dry mucous membranes
**Neck:** No meningismus
**Lungs:** Crackles right lower lobe, dullness to percussion
**Cardiac:** Tachycardic, no murmur
**Abdomen:** Suprapubic tenderness, no guarding
**GU:** Prostate enlarged on rectal exam
**Skin:** Mottled lower extremities, warm
**Neuro:** Confused, no focal deficits

### Diagnostic Testing

**Labs:**
- WBC: 22,400 with 88% neutrophils, 15% bands (bandemia)
- Hgb: 10.2
- Plt: 98,000 (thrombocytopenia - DIC concern)
- BMP: Na 132, K 5.2, Cr 2.4 (baseline 1.1), glucose 342
- Lactate: 4.8 mmol/L
- Procalcitonin: 18.2 ng/mL (markedly elevated)
- Bilirubin: 2.4
- Coags: PT 16.2, INR 1.4

**Urinalysis:**
- Positive leukocyte esterase, positive nitrites
- >100 WBC, bacteria present

**Chest X-ray:** Right lower lobe consolidation

**Likely Sources:**
1. Urinary tract infection → urosepsis (primary)
2. Pneumonia (may be secondary aspiration vs. concurrent)

### Response to Initial Resuscitation

**After 2L crystalloid:**
- BP: 88/54 (still hypotensive)
- MAP: 65 (borderline)
- Lactate: 4.2 (minimally improved)
- Mental status: Unchanged

**Persistent Hypotension = SEPTIC SHOCK**

### Vasopressor Initiation

**Norepinephrine:**
- First-line vasopressor for septic shock
- Started at 0.1 mcg/kg/min via central line
- Titrated to MAP ≥65 mmHg
- Required: 0.25 mcg/kg/min

**Additional Fluids:**
- Continue cautious fluid resuscitation
- Assess fluid responsiveness (passive leg raise, pulse pressure variation)

### Ongoing Management

**Source Control:**
- Foley catheter placed (urinary source)
- CT scan deferred initially due to instability
- Urology consulted for possible prostatic abscess

**Additional Interventions:**
- Stress-dose steroids: Hydrocortisone 50mg IV q6h (for refractory shock)
- Glucose management
- DVT prophylaxis when stable
- Stress ulcer prophylaxis

### Clinical Course

| Time | MAP | Lactate | Vasopressor | Mental Status |
|------|-----|---------|-------------|---------------|
| 0 hr | 52 | 4.8 | None | Confused |
| 2 hr | 68 | 4.2 | Norepi 0.25 | Confused |
| 6 hr | 72 | 2.8 | Norepi 0.15 | Improving |
| 12 hr | 75 | 1.8 | Norepi 0.05 | Alert |
| 24 hr | 78 | 1.2 | Weaning | Baseline |

**Culture Results:**
- Blood cultures: E. coli (pan-sensitive)
- Urine culture: E. coli >100,000 CFU/mL

**Antibiotic Adjustment:**
- De-escalated to ceftriaxone monotherapy (narrowed based on sensitivities)

### Disposition
- ICU admission
- Vasopressors weaned by 36 hours
- Transferred to floor day 3
- Completed 7-day course of antibiotics
- AKI resolved (Cr 1.3 at discharge)
- Discharged day 7
- Follow-up for diabetes optimization and BPH management

### Teaching Points

1. **Hour-1 bundle saves lives:** Lactate, cultures, antibiotics, fluids - all within 1 hour
2. **Don't delay antibiotics:** Each hour delay increases mortality; give before source is identified
3. **30 mL/kg crystalloid:** Initial resuscitation volume; reassess and continue if needed
4. **MAP goal ≥65 mmHg:** Norepinephrine is first-line vasopressor
5. **Lactate clearance:** Repeat at 2-6 hours; goal >10% decrease
6. **Source control:** Identify and treat the source (drain abscess, remove catheter, etc.)
7. **De-escalate antibiotics:** Narrow based on culture results

### Clinical Image
![Sepsis Bundle Flowchart](case_01_image.jpg)

**Image Description:** Flowchart depicting the Hour-1 Sepsis Bundle components including measurement of lactate, blood cultures, broad-spectrum antibiotics, and crystalloid resuscitation for hypotension or lactate ≥4 mmol/L.

**Attribution:** Image adapted from Surviving Sepsis Campaign guidelines. Educational use. Source: https://www.sccm.org/SurvivingSepsisCampaign/Guidelines

---

## Case 2: Necrotizing Fasciitis - The Rapidly Progressive Infection

### Patient Demographics
- **Age:** 52 years
- **Sex:** Male
- **Occupation:** Construction worker

### Chief Complaint
"My leg is killing me and getting worse by the minute."

### History of Present Illness
A 52-year-old male presents with severe left lower leg pain that began 24 hours ago. He reports a minor scrape on his shin 3 days ago while at work. Yesterday he noticed redness around the wound and today the pain has become excruciating - "worse than anything I've ever felt." He has diabetes and admits to poor glucose control. His wife notes the redness has been "spreading fast" and his skin looks "weird."

### Initial Assessment

**ESI Level:** 1 - Suspected necrotizing soft tissue infection

**First Impression:**
- Appearance: Writhing in pain, appears toxic
- Work of breathing: Tachypneic
- Circulation: Tachycardic, diaphoretic

**Vital Signs:**
- Heart rate: 128 bpm
- Blood pressure: 98/62 mmHg
- Respiratory rate: 24 breaths/min
- SpO2: 96% on room air
- Temperature: 39.2C (102.6F)
- GCS: 15

### Key Clinical Feature: Pain Out of Proportion

**Classic Finding:**
- Patient describes 10/10 pain
- On exam: Minimal erythema visible
- **Pain SIGNIFICANTLY exceeds apparent physical findings** - RED FLAG for necrotizing fasciitis

### Primary Survey

**Airway:** Patent
**Breathing:** Tachypneic, clear lungs
**Circulation:** Tachycardic, hypotensive
**Disability:** Alert, in severe distress
**Exposure:** Left lower leg examination critical

### Lower Extremity Examination

**Left Lower Leg:**
- Wound: Small healing scrape over anterior shin
- Erythema: Expanding margins (wife marked border 2 hours ago - now 4cm beyond)
- Skin changes: Dusky/gray discoloration, tense edema
- Bullae: Early hemorrhagic bullae forming
- Crepitus: Present on palpation (subcutaneous gas!)
- Temperature: Paradoxically cool in center, warm periphery
- Sensation: Decreased over affected area (nerve involvement)

**LRINEC Score (Laboratory Risk Indicator for Necrotizing Fasciitis):**
| Variable | Points | This Patient |
|----------|--------|--------------|
| CRP ≥150 mg/L | 4 | 4 |
| WBC 15-25 | 1 | 1 |
| Hgb <13.5 | 1 | 1 |
| Na <135 | 2 | 2 |
| Cr >1.6 | 2 | 2 |
| Glucose >180 | 1 | 1 |
| **Total** | | **11** (>8 = strongly predictive) |

### Diagnosis - Clinical, Not Radiographic

**Necrotizing Fasciitis - Clinical Criteria:**
- Pain out of proportion to exam ✓
- Rapidly progressive ✓
- Systemic toxicity ✓
- Skin changes (dusky, bullae) ✓
- Crepitus (gas in tissue) ✓

**DO NOT DELAY FOR IMAGING** - This is a clinical and surgical diagnosis

### Immediate Management

**Resuscitation:**
1. Two large-bore IVs
2. Aggressive fluid resuscitation
3. Blood cultures obtained
4. Lactate: 6.2 mmol/L

**Antibiotics (Broad-Spectrum, High-Dose):**
- Vancomycin 25 mg/kg IV (MRSA, strep)
- Piperacillin-tazobactam 4.5g IV (broad coverage)
- Clindamycin 900mg IV (toxin suppression - critical for strep)

**Emergency Surgical Consultation:**
- Called immediately
- Patient taken to OR within 90 minutes of ED arrival

### Secondary Survey

**SAMPLE History:**
- Symptoms: Severe leg pain, fever, spreading redness
- Allergies: None
- Medications: Metformin, glipizide
- PMH: Type 2 diabetes (poorly controlled, HbA1c 10.2%), peripheral vascular disease
- Last Meal: Breakfast today
- Events: Minor trauma 3 days ago

**Risk Factors for Necrotizing Fasciitis:**
- Diabetes mellitus ✓
- Peripheral vascular disease ✓
- Immunosuppression ✓
- Trauma/wound ✓
- Obesity
- IVDU

### Diagnostic Testing

**Labs:**
- WBC: 24,800 with left shift
- Na: 131 mEq/L
- Cr: 2.1
- Glucose: 382 mg/dL
- Lactate: 6.2 mmol/L
- CRP: 312 mg/L
- Procalcitonin: 22.4 ng/mL
- CK: 1,840 IU/L (muscle involvement)

**Blood Gas:** pH 7.28, metabolic acidosis

**Imaging (obtained rapidly, did NOT delay surgery):**
- X-ray: Subcutaneous gas visible
- CT (if stable): Gas tracking along fascial planes

### Operative Findings

**Surgical Exploration:**
- Incision revealed grayish, necrotic fascia
- "Dishwater" purulent fluid
- Easy separation of tissue planes (fascial necrosis)
- Thrombosed vessels
- Extensive debridement required
- Muscle involvement (myonecrosis) present

**Extent:**
- Radical debridement from mid-thigh to ankle
- Multiple return trips to OR for serial debridement

**Tissue Cultures:** Group A Streptococcus (Strep pyogenes)

### Microbiology of Necrotizing Fasciitis

| Type | Organisms | Clinical Setting |
|------|-----------|------------------|
| Type I (polymicrobial) | Mixed aerobic/anaerobic | Diabetes, surgery |
| **Type II (monomicrobial)** | **Group A Strep, Staph aureus** | **Healthy adults, minor trauma** |
| Type III | Vibrio, Clostridium | Water exposure, IVDU |

This patient: Type II - Group A Streptococcal necrotizing fasciitis ("flesh-eating bacteria")

### Post-Operative Management

**ICU Care:**
- Mechanical ventilation (24 hours)
- Vasopressors (norepinephrine)
- Serial debridements (OR x4)
- Wound VAC placement
- Nutrition support

**Antibiotic Duration:**
- Continued IV antibiotics until source control achieved
- De-escalated to penicillin + clindamycin based on sensitivities
- Total course: 14 days

**IVIG Consideration:**
- Considered for streptococcal toxic shock syndrome
- Given 1g/kg

### Outcome

**Hospital Course:**
- ICU: 5 days
- Total hospitalization: 28 days
- Required skin grafting
- Extensive rehabilitation

**Limb Salvage:** Successful (avoided amputation)

### Teaching Points

1. **Pain out of proportion is the key finding:** Disproportionate pain with minimal skin findings = necrotizing fasciitis until proven otherwise
2. **Clinical diagnosis, surgical emergency:** Do NOT delay for imaging
3. **Time is tissue:** Mortality increases 7-9% for each hour of surgical delay
4. **Clindamycin is essential:** Suppresses toxin production (especially for streptococcal)
5. **Serial debridements:** One operation is rarely sufficient
6. **LRINEC score:** Can support diagnosis but don't rely on it to rule out
7. **Mortality remains high:** 20-40% despite optimal treatment
8. **Crepitus is late finding:** Absence of crepitus doesn't rule out necrotizing fasciitis

### Clinical Image
![CT showing Gas in Soft Tissue - Necrotizing Fasciitis](case_02_image.jpg)

**Image Description:** CT scan of the lower extremity demonstrating gas tracking along the fascial planes (arrows), consistent with necrotizing fasciitis. Subcutaneous gas appears as dark (low density) areas within the soft tissue.

**Attribution:** Image from Radiopaedia.org, Case courtesy of Dr. Henry Knipe. Licensed under CC BY-NC-SA 3.0. Source: https://radiopaedia.org/cases/necrotizing-fasciitis-4

---

## Case 3: Bacterial Meningitis - The Adult with Headache and Fever

### Patient Demographics
- **Age:** 45 years
- **Sex:** Female
- **Occupation:** Elementary school teacher

### Chief Complaint
"I have the worst headache of my life and I can't stand the light."

### History of Present Illness
A 45-year-old female presents with 24 hours of progressively worsening headache, now 10/10 severity. She developed fever, neck stiffness, and photophobia overnight. Her husband reports she has been increasingly confused over the past few hours. She had a mild upper respiratory infection last week that seemed to resolve. No recent travel or sick contacts with similar symptoms.

### Initial Assessment

**ESI Level:** 1 - Suspected bacterial meningitis

**First Impression:**
- Appearance: Ill-appearing, eyes closed, minimal movement
- Work of breathing: Normal
- Circulation: Flushed

**Vital Signs:**
- Heart rate: 108 bpm
- Blood pressure: 138/82 mmHg
- Respiratory rate: 18 breaths/min
- SpO2: 97% on room air
- Temperature: 39.4C (102.9F)
- GCS: 13 (E3V4M6)

### Classic Triad of Meningitis

| Feature | Present |
|---------|---------|
| Fever | Yes (39.4C) |
| Neck stiffness | Yes |
| Altered mental status | Yes (GCS 13) |

**Note:** Classic triad present in only 44% of adults with bacterial meningitis

### Primary Survey

**Airway:** Patent
**Breathing:** Normal
**Circulation:** Tachycardic, well-perfused
**Disability:** Confused, photophobic, meningeal signs present
**Exposure:** No rash (important - no petechiae)

### Meningeal Signs Examination

**Nuchal Rigidity:** Present - passive neck flexion causes resistance and pain

**Kernig Sign:** Positive - resistance/pain with knee extension when hip flexed

**Brudzinski Sign:** Positive - passive neck flexion causes hip/knee flexion

**Jolt Accentuation:** Positive - horizontal head rotation worsens headache

### Critical Decision Point: CT Before LP?

**Indications for CT Before LP:**
- Immunocompromised state
- History of CNS disease
- New-onset seizure
- Papilledema
- **Altered level of consciousness** ✓
- Focal neurologic deficit

**This Patient:** Has altered mental status → CT before LP indicated

**CRITICAL:** Do NOT delay antibiotics for CT or LP

### Management Timeline

**Time 0 (arrival):**
- Clinical assessment: Suspected bacterial meningitis
- Blood cultures obtained

**Time 15 minutes:**
- Dexamethasone 0.15 mg/kg IV (give BEFORE or WITH first antibiotic dose)
- Ceftriaxone 2g IV
- Vancomycin 25 mg/kg IV
- Acyclovir 10 mg/kg IV (HSV coverage given altered mental status)

**Time 45 minutes:**
- CT head: No mass effect, no contraindication to LP

**Time 60 minutes:**
- Lumbar puncture performed

### Secondary Survey

**SAMPLE History:**
- Symptoms: Headache, fever, neck stiffness, photophobia, confusion
- Allergies: None
- Medications: Metformin, lisinopril
- PMH: Type 2 diabetes, hypertension, no immunosuppression
- Last Meal: Yesterday evening
- Events: URI last week, then progressive symptoms

**Physical Examination:**

**HEENT:**
- Photophobia present
- No papilledema on fundoscopy
- Ears: No otitis media

**Neurological:**
- Oriented to person only
- No focal motor deficits
- Cranial nerves intact
- Meningeal signs positive

**Skin:**
- No petechiae or purpura (would suggest meningococcemia)

### Diagnostic Testing

**Lumbar Puncture Results:**
| Parameter | Result | Normal | Interpretation |
|-----------|--------|--------|----------------|
| Opening pressure | 32 cm H2O | <20 | Elevated |
| WBC | 2,850/μL | <5 | Markedly elevated |
| Differential | 92% neutrophils | <5% | Neutrophil predominant |
| Protein | 248 mg/dL | <45 | Elevated |
| Glucose | 22 mg/dL | 40-70 | Low |
| CSF:serum glucose | 0.22 | >0.6 | Very low ratio |
| Gram stain | Gram-positive diplococci | - | Pneumococcus |

**Labs:**
- WBC: 18,400 with left shift
- BMP: Normal except glucose 142
- Procalcitonin: 8.4 ng/mL

**CSF Interpretation:**
- High WBC with neutrophil predominance + low glucose + high protein = BACTERIAL MENINGITIS

### Diagnosis

**Acute Bacterial Meningitis** - Streptococcus pneumoniae (based on Gram stain)

### Antibiotic Adjustment

**Based on Gram Stain (Gram-positive diplococci = pneumococcus):**
- Continue ceftriaxone + vancomycin (until sensitivities)
- Continue dexamethasone (proven benefit for pneumococcal meningitis)
- Discontinue acyclovir (not HSV)

**Culture Results (48 hours):**
- CSF culture: Streptococcus pneumoniae (penicillin MIC 0.06 = sensitive)
- Blood cultures: S. pneumoniae

**Antibiotic De-escalation:**
- Discontinued vancomycin (sensitive to ceftriaxone)
- Continued ceftriaxone 2g IV q12h x 10-14 days

### Dexamethasone in Meningitis

**Evidence:** Reduces mortality and neurological sequelae in pneumococcal meningitis

**Dosing:** 0.15 mg/kg (max 10mg) q6h x 4 days

**Timing:** Must be given BEFORE or WITH first antibiotic dose

**When to use:** All suspected bacterial meningitis (adult); primarily benefits pneumococcal

### Clinical Course

**Day 1-2:** Continued antibiotics, steroids, supportive care; remained in ICU

**Day 3:** Mental status improving, GCS 15

**Day 5:** Transferred to floor

**Day 10:** Completed antibiotics, hearing evaluation (normal)

**Disposition:** Discharged day 12

### Teaching Points

1. **Give antibiotics immediately:** Don't delay for LP or CT; mortality increases with delays
2. **Dexamethasone timing critical:** Before or with first antibiotic dose; reduces mortality in pneumococcal meningitis
3. **CT before LP only if indicated:** Altered mental status, focal findings, immunocompromised, papilledema
4. **Classic triad uncommon:** All three (fever, neck stiffness, AMS) present in <50%
5. **CSF findings:** High WBC (neutrophils), low glucose (ratio <0.4), high protein = bacterial
6. **Empiric coverage:** Ceftriaxone + vancomycin ± ampicillin (if >50 or immunocompromised for Listeria)
7. **Hearing loss:** Common sequela; all patients need audiometry before discharge
8. **Chemoprophylaxis:** Close contacts need prophylaxis for meningococcal meningitis

### Clinical Image
![CSF Analysis in Bacterial Meningitis](case_03_image.jpg)

**Image Description:** Cerebrospinal fluid samples comparing normal clear CSF with turbid/cloudy CSF characteristic of bacterial meningitis due to elevated white blood cells and protein.

**Attribution:** Image from Wikimedia Commons, Cerebrospinal fluid in meningitis. Licensed under CC BY-SA 3.0. Source: https://commons.wikimedia.org/wiki/File:Csf-samples-702x336.jpg