When to intubate in GCS?

GCS ≤ 8 requires intubation for airway protection. The patient cannot protect their own airway at this level of consciousness. Motor score is the most prognostically important component.

What is the best initial fluid for sepsis resuscitation?

Lactated Ringer's (LR) is the preferred resuscitation fluid. The SMART trial (2018) showed balanced crystalloids reduced death, new renal failure, and persistent renal dysfunction compared to normal saline.

When to start vasopressors in septic shock?

Start norepinephrine (first-line vasopressor) if MAP remains < 65 mmHg after initial 30 mL/kg crystalloid resuscitation, or earlier if patient is profoundly hypotensive. Do not delay pressors to complete full fluid resuscitation.

Why can serum uric acid be normal during acute gout?

During acute inflammation, IL-6 increases renal urate excretion and redistributes urate from plasma to tissues. Up to 40% of acute gout flares have normal serum uric acid. Joint aspiration with polarized microscopy is needed for definitive diagnosis.

How do you distinguish lupus flare from infection in SLE?

Key clues: CRP is low/normal in flare but elevated in infection. Complement (C3/C4) drops in flare but is normal/elevated in infection. Procalcitonin is elevated in bacterial infection but normal in flare. Anti-dsDNA rises in flare, stable in infection.

What is the difference between DKA and HHS?

DKA features acidosis (pH 600), hyperosmolality (> 320), and minimal ketosis -typically in Type 2 DM. DKA requires insulin drip; HHS requires aggressive fluid resuscitation first.

When to give tPA in acute ischemic stroke?

IV alteplase (tPA) can be given within 4.5 hours of last known well time in eligible patients. CT head must rule out hemorrhage first. For large vessel occlusion, mechanical thrombectomy can be performed up to 24 hours with favorable imaging.

What antibiotics for community-acquired pneumonia?

Inpatient non-ICU: ceftriaxone + azithromycin. ICU: ceftriaxone + azithromycin (add vancomycin if MRSA risk). Outpatient healthy: amoxicillin. Outpatient with comorbidities: augmentin + azithromycin or respiratory fluoroquinolone. Duration: 5 days if clinically stable for 48 hours.

How to interpret iron studies?

Iron deficiency: low ferritin (< 30), high TIBC, low iron, low transferrin saturation (< 20%). Anemia of chronic disease: normal/high ferritin (acute phase reactant), low TIBC, low iron. A ferritin of 50-100 in an inflamed patient may still represent iron deficiency.

What is the correction rate for hyponatremia?

Correct sodium no more than 8 mEq/L in 24 hours to avoid osmotic demyelination syndrome (ODS). For symptomatic severe hyponatremia with seizures, give 3% hypertonic saline 100-150 mL bolus over 10-20 minutes. If overcorrected, use D5W + DDAVP rescue protocol.

When to start antibiotics in meningitis?

Within 30-60 minutes. Do NOT delay antibiotics for LP or CT. Draw blood cultures, start empiric antibiotics (vancomycin + ceftriaxone ± ampicillin if > 50 or immunocompromised), then perform LP when possible. Dexamethasone should be given before or with the first antibiotic dose.

DOACs vs warfarin in antiphospholipid syndrome?

DOACs are contraindicated in APS. The TRAPS trial (2018) showed rivaroxaban was inferior to warfarin with more thrombotic events in triple-positive APS patients. Warfarin with INR target 2-3 is the standard for APS, indefinitely.

How to manage scleroderma renal crisis?

ACE inhibitors (captopril) are life-saving -start immediately and titrate aggressively. Do NOT hold for rising creatinine. Steroids > 15 mg prednisone per day precipitate scleroderma renal crisis. ARBs are NOT a substitute -evidence is only for ACEi.

What are the 4 pillars of heart failure treatment?

Guideline-directed medical therapy (GDMT) for HFrEF: (1) ARNI or ACEi/ARB, (2) beta-blocker (carvedilol, metoprolol succinate, or bisoprolol), (3) MRA (spironolactone or eplerenone), (4) SGLT2 inhibitor (dapagliflozin or empagliflozin). All four should be initiated and titrated to target doses.

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EmergencyID / Ortho

Septic Arthritis

Septic arthritis is a joint emergency, delay in drainage and antibiotics leads to irreversible cartilage destruction within 24–48 hours. The knee is the most commonly affected joint. Synovial fluid WBC >50,000 with >90% PMNs is the diagnostic hallmark. Aspirate before antibiotics when possible, but never delay empiric treatment for a toxic-appearing patient.

🔍 Overview

Key Concepts

Definition: Bacterial infection within a joint space, a true orthopedic/medical emergency requiring urgent drainage and IV antibiotics
Incidence: 2–10 per 100,000/year; higher in RA, prosthetic joints, immunosuppression, IV drug use
Most common joint: Knee (50%), followed by hip, shoulder, ankle, wrist
Route: Hematogenous spread (most common), direct inoculation (trauma, injection, surgery), contiguous spread from adjacent osteomyelitis
Irreversible cartilage damage begins within 24–48 hours if untreated, this is why urgent drainage is essential

Microbiology

Population	Most Common Organisms	Key Notes
Adults (non-gonococcal)	Staphylococcus aureus (60–70%), Streptococcus spp. (15–20%)	MRSA prevalence increasing, consider empiric vancomycin. GNRs in elderly, immunocompromised, IVDU.
Young sexually active adults	Neisseria gonorrhoeae	Most common cause in sexually active young adults. Migratory polyarthralgia → mono/oligoarthritis + tenosynovitis + skin lesions (pustular). Blood/synovial cultures often negative, send NAAT.
Children <5 years	S. aureus, Kingella kingae, Group A Strep	Kingella often culture-negative, request PCR/16S rRNA. H. influenzae now rare (vaccination).
IVDU	S. aureus, Pseudomonas, Serratia	Unusual joints (sacroiliac, sternoclavicular). Consider GNR coverage.
Prosthetic joint	S. aureus, coagulase-negative Staph, Cutibacterium acnes	Early (<3 months): aggressive organisms. Late (>12 months): low-virulence organisms (CoNS, C. acnes). Hold cultures ≥14 days for slow-growers.
Animal/human bites	Pasteurella multocida (cat), Eikenella corrodens (human), polymicrobial	Amoxicillin-clavulanate for bite wounds near joints. If joint penetrated, treat as septic arthritis.

Risk Factors

Pre-existing joint disease: Rheumatoid arthritis (RA), osteoarthritis, gout, crystal arthropathy, RA has 10x increased risk
Prosthetic joint, foreign material = biofilm risk
Immunosuppression: Diabetes, HIV, corticosteroids, biologics (TNF inhibitors), malignancy
Skin breakdown: Psoriasis, eczema, cellulitis, skin ulcers overlying joints
Recent joint procedure: Arthrocentesis, injection, arthroscopy, surgery
IVDU, hematogenous seeding; unusual joint locations
Age >80

Septic arthritis and crystal arthropathy can coexist. Finding crystals on synovial fluid does NOT rule out infection. If clinical suspicion is high, treat empirically until cultures finalize, gout and septic arthritis overlap in 5% of cases.

🧪 Workup

Synovial Fluid Analysis, The Key Diagnostic Test

Arthrocentesis is mandatory for any acute monoarthritis with effusion. Aspirate BEFORE starting antibiotics when possible (but do not delay antibiotics if patient is septic).

Parameter	Normal	Non-inflammatory	Inflammatory (Gout/RA)	Septic
Appearance	Clear, colorless	Clear, yellow	Translucent–opaque, yellow	Opaque, purulent
WBC (/μL)	<200	200–2,000	2,000–50,000	>50,000 (often >100K)
PMN %	<25%	<25%	50–70%	>90%
Gram stain	Negative	Negative	Negative	Positive in 50–75%
Culture	Negative	Negative	Negative	Positive in 70–90%
Crystals	None	None	MSU (gout) or CPPD	Usually none (but coexistence possible)

WBC >50,000 with >90% PMNs = septic until proven otherwise. However, partially-treated infections and prosthetic joint infections may have lower WBC counts. A WBC of 25,000–50,000 does NOT rule out infection, clinical context matters.

Additional Workup

Test	Rationale
Synovial fluid Gram stain & culture	Gold standard. Positive in ~70–90% for non-gonococcal. Only ~25% positive for gonococcal. Send in blood culture bottles to improve yield.
Synovial fluid crystal analysis	Rule out gout (negatively birefringent MSU) and pseudogout (weakly positive CPPD). Remember: crystals + infection can coexist.
Blood cultures (×2 sets)	Positive in 40–50% of non-gonococcal septic arthritis. Essential for tailoring therapy.
CBC, CRP, ESR	WBC, CRP elevated in most cases. CRP >100 mg/L has high sensitivity. ESR less specific. Useful for monitoring treatment response.
Gonococcal NAAT	Urethral/cervical/pharyngeal/rectal NAAT if disseminated gonococcal infection (DGI) suspected. Synovial fluid NAAT increasingly available.
X-ray (affected joint)	Often normal early. Soft tissue swelling, joint effusion. Late: joint space narrowing, erosions, periosteal reaction. Baseline for comparison.
Ultrasound	Detect effusion (especially hip, difficult to examine clinically). Guide arthrocentesis. Rapidly available at bedside.
MRI	Best imaging for complications: adjacent osteomyelitis, soft tissue abscess, synovial enhancement. Order if poor response to treatment.

Kocher Criteria (Pediatric Hip, Septic vs Transient Synovitis)

Criteria	Points
Non-weight-bearing on affected side	1
Fever >38.5°C	1
WBC >12,000/μL	1
ESR >40 mm/hr	1

0 criteria: <0.2% risk • 1: 3% • 2: 40% • 3: 93% • 4: 99% probability of septic arthritis. CRP >20 mg/L added as 5th criterion in modified Kocher.

🚨 Management

Two Pillars: Drainage + Antibiotics

Both drainage AND antibiotics are required. Antibiotics alone are insufficient, purulent material destroys cartilage via proteolytic enzymes. Source control is mandatory.

Drainage Options

Method	When to Use	Key Points
Serial arthrocentesis (needle aspiration)	First-line for most accessible joints (knee, ankle, wrist, elbow)	Aspirate to dryness daily until effusion resolves. Monitor WBC trend, should decrease with effective treatment. Simple, bedside, repeatable.
Arthroscopic washout	Failed serial aspiration, loculated collection, shoulder	Better visualization, more thorough lavage. Can break adhesions/loculations. Preferred for shoulder (difficult to aspirate completely).
Open arthrotomy	Hip (always), failed arthroscopy, prosthetic joint, pediatric	Hip joint is deep and difficult to drain percutaneously, open surgical drainage is standard for septic hip. Also needed if hardware present or tissue necrosis.

Septic hip = surgical emergency. The hip joint cannot be adequately drained by needle aspiration, consult orthopedics immediately for open washout. In children, a septic hip can compromise femoral head blood supply and cause avascular necrosis.

Empiric Antibiotic Therapy

Scenario	Empiric Regimen	Duration	Notes
Native joint (typical)	Vancomycin 15–20 mg/kg IV q8–12h	2–4 weeks total (IV → PO step-down)	Covers MRSA + MSSA. Add ceftriaxone 2g IV daily if GNR suspected (elderly, immunocompromised, IVDU). De-escalate by culture.
GNR risk factors (elderly, IVDU, immunocompromised)	Vancomycin + Ceftriaxone 2g IV daily or Cefepime 2g IV q8h	2–4 weeks	Cefepime if Pseudomonas risk (IVDU, recent hospitalization). Narrow by culture & sensitivity.
Disseminated gonococcal infection	Ceftriaxone 1g IV daily	7–14 days (switch to PO after improvement)	Treat until clinically improved (usually 24–48h IV) then step down to PO cefixime or azithromycin. Treat concomitant chlamydia (azithromycin 1g or doxycycline). Test + treat sexual partners.
Prosthetic joint infection (acute)	Vancomycin + Cefepime or Meropenem	6 weeks IV + chronic suppressive PO	ID + Orthopedics co-management. Options: DAIR (debridement, antibiotics, implant retention) if early (<30 days) and stable implant. Otherwise: 1-stage or 2-stage exchange arthroplasty.

IV-to-PO Transition & Duration

Switch to PO when: Clinical improvement (less pain, decreased effusion, defervesced), declining CRP, known organism with oral susceptibility, GI tract functioning
OVIVA trial evidence supports early PO step-down for bone and joint infections with equivalent outcomes to prolonged IV therapy OVIVA, 2019
Total duration (native joint): S. aureus: 4 weeks minimum. Streptococcus: 2–3 weeks. GNRs: 3–4 weeks. Gonococcal: 7–14 days.
Monitor: CRP trending down (best marker), clinical exam (pain, ROM, effusion), repeat aspiration if not improving
Ortho follow-up: Functional rehabilitation after infection clears, early PT to prevent joint stiffness and contracture

💊 Medications

Key Antibiotics for Septic Arthritis

Drug (Brand)	Mechanism	Dosing	Key Considerations
Vancomycin (Vancocin)	Glycopeptide, inhibits cell wall synthesis by binding D-Ala-D-Ala	15–20 mg/kg IV q8–12h Target AUC/MIC 400–600	Empiric MRSA coverage. Monitor trough or AUC. Nephrotoxic, monitor SCr. Red man syndrome with rapid infusion (rate-related, not allergy). Good synovial fluid penetration.
Ceftriaxone (Rocephin)	3rd-gen cephalosporin, inhibits PBPs	2g IV q24h	GNR coverage + gonococcal coverage. Once-daily dosing (long half-life). Do not use in neonates with bilirubin issues. Good bone/joint penetration.
Cefazolin (Ancef)	1st-gen cephalosporin	2g IV q8h	Step-down from vancomycin once MSSA confirmed. Excellent bone penetration. Can transition to PO cephalexin or dicloxacillin.
Nafcillin/Oxacillin	Anti-staphylococcal penicillin	2g IV q4h	Gold standard for MSSA. Excellent bone/joint penetration. Interstitial nephritis risk. Alternative: cefazolin (easier dosing).
Cefepime (Maxipime)	4th-gen cephalosporin	2g IV q8h	Pseudomonas coverage + GNR. Use when Pseudomonas risk (IVDU, nosocomial). CNS toxicity at high doses/renal impairment.
TMP-SMX (Bactrim)	Folate synthesis inhibitor	DS 1–2 tabs PO BID	Oral MRSA step-down option. Good bioavailability. Monitor K⁺ (hyperkalemia risk). Not for strep coverage (unreliable).

📋 On Rounds

What synovial fluid findings diagnose septic arthritis?

WBC >50,000/μL with >90% PMNs is the classic finding. Gram stain positive in 50–75%. Synovial fluid culture positive in 70–90%. However, partially-treated infections may have lower counts. Any WBC >25,000 with clinical suspicion warrants empiric treatment pending cultures. Crystals do NOT exclude infection.

Why does a septic hip always require open surgical drainage?

The hip is a deep ball-and-socket joint that cannot be adequately drained by needle aspiration. Increased intra-articular pressure from purulent effusion can compress the retinacular blood supply to the femoral head, causing avascular necrosis. In children, the femoral head blood supply is especially vulnerable. Open arthrotomy allows thorough washout, debridement, and pressure decompression.

How do you distinguish gonococcal from non-gonococcal septic arthritis?

Gonococcal: Young, sexually active. Classic triad: migratory polyarthralgia → tenosynovitis + dermatitis (pustular/vesicular skin lesions) + mono/oligoarthritis. Synovial fluid cultures often NEGATIVE (<25%). Diagnosis: GC NAAT from urethra/cervix/pharynx/rectum + synovial NAAT. Non-gonococcal: Older, comorbidities. Acute monoarthritis. Synovial cultures positive 70–90%. S. aureus predominates.

Can gout and septic arthritis coexist? How do you manage this?

Yes, crystals + infection coexist in ~5% of cases. Finding MSU or CPPD crystals does NOT rule out septic arthritis. If clinical suspicion remains (fever, WBC >50K, risk factors), treat empirically with antibiotics AND drainage until cultures return. A common pitfall is attributing a hot joint to gout alone and missing concomitant infection.

What are the Kocher criteria and when are they used?

The Kocher criteria distinguish septic arthritis from transient synovitis in pediatric hip pain: (1) non-weight-bearing, (2) fever >38.5°C, (3) WBC >12,000, (4) ESR >40. With 0 criteria: <0.2% risk; 4 criteria: 99% risk. CRP >20 added as modified 5th criterion. ≥2 criteria warrant aspiration under sedation/US guidance.

📣 Sample Presentation

One-Liner

"Mr. Davis is a 68-year-old man with diabetes and rheumatoid arthritis on methotrexate presenting with 2 days of acute right knee swelling, pain, and inability to bear weight, with fever to 39.1°C. Arthrocentesis showed WBC 78,000 with 95% PMNs and positive Gram stain for gram-positive cocci in clusters, consistent with septic arthritis."

Key Points to Cover on Rounds

Septic arthritis of right knee, synovial fluid WBC 78,000, >95% PMNs, Gram stain with GPC in clusters (likely S. aureus). Started vancomycin empirically, awaiting final culture and sensitivities. Serial arthrocentesis performed, aspirated 45 mL of purulent fluid. Blood cultures ×2 sent. CRP 185. Orthopedics consulted, will reassess for arthroscopic washout if not improving with serial aspiration. Held methotrexate given active infection. Plan to narrow antibiotics by culture. Target 4-week course if S. aureus confirmed. Early PT once infection controlled.

⚡ Summary

Summary

Diagnosis

Arthrocentesis: WBC >50K, >90% PMNs. Gram stain + culture. Blood cultures. Crystals don't rule out infection.

Empiric Therapy

Vancomycin (± ceftriaxone if GNR risk). DGI: ceftriaxone 1g IV daily. De-escalate by culture.

Drainage

Serial aspiration (knee/ankle/wrist). Hip = open arthrotomy always. Arthroscopy if loculated or failing.

Duration

S. aureus: 4 weeks. Strep: 2–3 weeks. GNRs: 3–4 weeks. DGI: 7–14 days. IV → PO step-down supported.

Gonococcal

Young + triad (polyarthralgia, tenosynovitis, pustules). Culture often negative. NAAT from GU/pharynx/rectal. Treat chlamydia too.

Don't Miss

Crystals + infection coexist. Septic hip = surgical emergency. Prosthetic joint = ID + Ortho + long course. RA patients: 10x risk.

📄 One Pager

Septic Arthritis, Quick Reference Card

Print this page (Ctrl/Cmd + P) for a condensed reference card.

SEPTIC ARTHRITIS, AT A GLANCE

📋 Diagnose: Aspirate every acute monoarthritis. WBC >50K + >90% PMNs = septic. Gram stain + culture.
🧪 Labs: Blood cultures ×2, CRP, ESR. GC NAAT if young/sexually active. X-ray baseline.
💉 Drain: Serial aspiration (knee/ankle). Hip = open arthrotomy ALWAYS. Arthroscopy if failing.
💊 Treat: Vancomycin empirically (± ceftriaxone/cefepime for GNR). DGI: ceftriaxone 1g daily.
⏱️ Duration: Staph 4 wk, Strep 2–3 wk, GNR 3–4 wk, GC 7–14d. IV → PO when improving.
⚠️ Pitfalls: Crystals don't rule out infection. Prosthetic joint = ID + Ortho. RA = 10x risk.