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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High-YieldID / Surgery / Wards

Intra-Abdominal Infections

Intra-abdominal infections (IAI) range from uncomplicated appendicitis to life-threatening peritonitis and hepatic abscess. Source control (surgery, drainage, or percutaneous intervention) is the cornerstone, antibiotics alone are insufficient for complicated IAI. Empiric coverage must include gram-negatives AND anaerobes. SBP in cirrhotics is a distinct entity requiring paracentesis and rapid antibiotics.

🔍 Overview

Classification

Type	Definition	Examples
Uncomplicated IAI	Infection confined to a single organ, no peritoneal contamination	Uncomplicated appendicitis, uncomplicated cholecystitis, uncomplicated diverticulitis
Complicated IAI (cIAI)	Infection extends beyond the organ into the peritoneal space, abscess, peritonitis, or perforation	Perforated appendicitis, perforated diverticulitis, peritonitis, intra-abdominal abscess, anastomotic leak
Primary peritonitis (SBP)	Peritoneal infection without visceral perforation. Spontaneous. Almost exclusively in cirrhotics with ascites.	Spontaneous bacterial peritonitis in cirrhosis. Usually monomicrobial (E. coli, Klebsiella, Strep pneumo).
Secondary peritonitis	Peritoneal contamination from GI tract perforation or disruption	Perforated ulcer, ruptured appendix, diverticular perforation, anastomotic leak, traumatic bowel injury
Tertiary peritonitis	Persistent/recurrent peritonitis after initially adequate source control	Often nosocomial organisms (Enterococcus, Candida, resistant GNRs). High mortality. ICU population.

Common Intra-Abdominal Infections

Condition	Presentation	Key Management
SBP	Cirrhotic + ascites + fever, abdominal pain, AMS, worsening encephalopathy. May be subtle.	Diagnostic paracentesis: PMN ≥250/mm³ = SBP. Start ceftriaxone 2g IV daily. Albumin 1.5 g/kg day 1, 1 g/kg day 3 (if Cr >1, BUN >30, or bilirubin >4). No source control needed.
Acute cholangitis	Charcot triad: fever + jaundice + RUQ pain. Reynolds pentad adds AMS + hypotension (severe). Biliary obstruction.	Emergency biliary drainage (ERCP or PTC) within 24h for severe cholangitis. Antibiotics: pip-tazo or ceftriaxone + metronidazole. Blood cultures. Fluid resuscitation.
Intra-abdominal abscess	Persistent fever despite antibiotics, localized pain, elevated WBC/CRP. Often post-surgical.	Percutaneous drainage (CT or US-guided) is first-line. Surgery if not drainable percutaneously, multiloculated, or associated with fistula. Antibiotics alone insufficient for large (>3 cm) abscesses.
Perforated viscus	Acute abdomen: sudden severe pain, rigidity, rebound, guarding. Free air on imaging.	Emergent surgery. Broad-spectrum antibiotics immediately. NPO, IV fluids, NG tube. Mortality increases with each hour of delay.
Diverticulitis (complicated)	LLQ pain, fever, perforation/abscess/fistula/stricture.	Small abscess (<3 cm): antibiotics alone. Large abscess: percutaneous drainage + antibiotics. Perforation with diffuse peritonitis: emergent surgery (Hartmann procedure).
Secondary peritonitis	Diffuse abdominal pain and tenderness, fever, sepsis following perforation or leak.	Source control is paramount (surgery to repair perforation, drain contamination). Broad-spectrum antibiotics. Polymicrobial: GNR + anaerobes + sometimes enterococcus.

Microbiology

Community-acquired cIAI: E. coli (most common), Klebsiella, Strep spp., Bacteroides fragilis (key anaerobe). Usually susceptible to standard empiric regimens.
Healthcare-associated/post-surgical: Resistant GNRs (ESBL, Pseudomonas, Acinetobacter), Enterococcus (including VRE), Candida. Broader empiric coverage needed.
SBP: Monomicrobial, E. coli (#1), Klebsiella, Strep pneumoniae. If polymicrobial on culture, suspect secondary peritonitis (perforation).
Biliary: E. coli, Klebsiella, Enterococcus, Bacteroides. Cholangitis may have Enterococcus more frequently than other cIAI.

Polymicrobial culture from ascites = red flag. SBP is monomicrobial. If multiple organisms grow from peritoneal fluid, suspect secondary peritonitis (bowel perforation) and get urgent CT imaging, the patient may need surgery, not just antibiotics.

🧪 Workup

Diagnostic Approach

Test	When	Key Points
CT abdomen/pelvis with IV contrast	First-line imaging for most cIAI	Gold standard for IAI. Detects abscess, free air, perforation, bowel wall thickening, mesenteric stranding. Sensitivity >95% for abscess. Guides percutaneous drainage.
Diagnostic paracentesis	ALL cirrhotics admitted with ascites	PMN ≥250/mm³ = SBP (start antibiotics immediately). Send: cell count + differential, culture (inoculate blood culture bottles at bedside for best yield), albumin, total protein, glucose, LDH, gram stain.
RUQ ultrasound	Cholecystitis, cholangitis, biliary obstruction	First-line for biliary pathology. Gallstones, GB wall thickening (>3 mm), pericholecystic fluid, sonographic Murphy sign, CBD dilation (>6 mm).
Blood cultures (×2 sets)	All suspected cIAI, SBP, cholangitis	Positive in 30–50% of SBP, higher in cholangitis. Essential for targeted therapy.
CBC, CMP, lipase, lactate	All suspected IAI	Leukocytosis (or leukopenia in severe sepsis). Elevated lactate = tissue hypoperfusion, surgical urgency. LFTs for biliary etiology. Lipase if pancreatitis in differential.
Upright chest X-ray / KUB	Suspected perforation (rapid screening)	Free air under diaphragm = perforation until proven otherwise. Sensitivity ~80% for pneumoperitoneum. CT is more sensitive if clinical suspicion persists with negative X-ray.
MRCP / ERCP	Biliary obstruction, cholangitis	MRCP: non-invasive biliary imaging. ERCP: therapeutic (stone extraction, stent placement) + diagnostic. Emergent ERCP for severe cholangitis.

SBP Diagnostic Criteria

Finding	Interpretation
Ascitic PMN ≥250/mm³	= SBP. Start empiric antibiotics immediately. Do not wait for culture.
Positive ascitic culture + PMN <250	= Bacterascites. May resolve spontaneously. Repeat paracentesis in 48h, if PMN rises to ≥250, treat as SBP.
PMN ≥250 + negative culture	= Culture-negative neutrocytic ascites (CNNA). Still SBP, treat the same. Cultures are negative in ~40% of SBP.
Ascitic fluid total protein >1 g/dL, glucose <50, LDH > serum	Suggests secondary peritonitis (perforation). Get urgent CT. Surgical evaluation.
Polymicrobial ascitic fluid culture	Secondary peritonitis until proven otherwise. CT + surgical consult.

🚨 Management

Principles of Management

Source control + antibiotics. Antibiotics alone are insufficient for complicated IAI with abscess, perforation, or necrosis. Identify and address the source: surgery (repair perforation, resection), percutaneous drainage (abscess), or endoscopic intervention (ERCP for cholangitis).

Empiric Antibiotic Therapy

Scenario	Empiric Regimen	Notes
Community-acquired, mild-moderate cIAI	Ceftriaxone 2g IV daily + Metronidazole 500 mg IV q8h or Ertapenem 1g IV daily	Covers GNRs + anaerobes. Ertapenem is single-agent option. No Pseudomonas or Enterococcus coverage needed for mild community-acquired. SIS/IDSA, 2010
Community-acquired, severe cIAI (sepsis, peritonitis)	Piperacillin-tazobactam 4.5g IV q6h or Meropenem 1g IV q8h	Broader coverage for sicker patients. Pip-tazo covers GNRs + anaerobes + Enterococcus. Meropenem for ESBL risk or penicillin allergy (severe).
Healthcare-associated / post-surgical	Meropenem 1g IV q8h or Pip-tazo + Vancomycin ± Fluconazole/Echinocandin	Broader coverage for resistant organisms (ESBL, Pseudomonas, VRE, Candida). Add vancomycin if MRSA/VRE risk. Add antifungal if Candida risk (prior surgery, TPN, broad-spectrum antibiotics). De-escalate aggressively by culture.
SBP (primary peritonitis)	Ceftriaxone 2g IV daily or Cefotaxime 2g IV q8h	Covers E. coli, Klebsiella, Strep pneumo. Do NOT add anaerobic coverage (SBP is monomicrobial, rarely anaerobic). Add albumin (1.5 g/kg day 1, 1 g/kg day 3), reduces mortality Sort, 1999
Cholangitis	Pip-tazo 4.5g IV q6h or Ceftriaxone + Metronidazole	Covers biliary pathogens (E. coli, Klebsiella, Enterococcus, Bacteroides). Priority: biliary drainage (ERCP) within 24h for severe cholangitis. Add vancomycin if healthcare-associated or concern for resistant Enterococcus.

Source Control by Condition

Condition	Source Control	Timing
Perforated viscus	Emergent surgery (repair, resection, washout)	ASAP, minutes to hours. Mortality increases with delay.
Acute cholangitis	ERCP with stone extraction/stent ± sphincterotomy	Within 24h (urgent). Emergent if severe sepsis/shock.
Acute cholecystitis	Cholecystectomy (lap chole) or percutaneous cholecystostomy if too sick for surgery	Within 72h preferred (early cholecystectomy). Perc chole if unstable/high surgical risk.
Intra-abdominal abscess	Percutaneous CT-guided drainage (first-line). Surgery if not amenable.	Within 24–48h of identification. Small (<3 cm) may resolve with antibiotics alone.
SBP	None, antibiotics only (no perforation)	Antibiotics immediately upon diagnosis (PMN ≥250)
Complicated diverticulitis with abscess	Small abscess (<3 cm): antibiotics. Larger: perc drain. Diffuse peritonitis: surgery.	Abscess drain within 24–48h. Surgery emergent if free perforation.

Duration of Therapy

Adequate source control achieved: 4 days (96 hours) of antibiotics is sufficient for most cIAI STOP-IT, 2015
Inadequate source control: Continue antibiotics until source control achieved + clinical improvement. No fixed duration.
SBP: 5 days of ceftriaxone (or until PMN <250 on repeat paracentesis at 48h)
Cholangitis: 4–7 days after successful biliary drainage
Bacteremia: If concurrent bacteremia, treat per BSI guidelines (typically 7–14 days from first negative culture)

STOP-IT trial: In cIAI with adequate source control, 4 days of antibiotics had similar outcomes to traditional longer courses (median 8 days). Shorter is better when the source is controlled, reduces resistance, C. diff risk, and cost.

💊 Medications

Key Antibiotics for Intra-Abdominal Infections

Drug (Brand)	Spectrum	Dosing	Key Considerations
Piperacillin-Tazobactam (Zosyn)	GNRs + anaerobes + Enterococcus + Pseudomonas	4.5g IV q6h (or 3.375g q6h extended infusion)	Workhorse for cIAI. Broad-spectrum single agent. Extended infusion (over 4h) improves PK. Does NOT cover ESBL-producers or MRSA.
Meropenem (Merrem)	Broadest: GNRs (incl ESBL) + anaerobes + Pseudomonas	1g IV q8h (2g q8h for CNS infections)	Reserve for healthcare-associated or ESBL risk. Does NOT cover MRSA or VRE. Seizure risk (lower than imipenem). Excellent penetration.
Ceftriaxone (Rocephin)	GNRs (not Pseudomonas)	2g IV q24h	Community-acquired cIAI backbone. Must pair with metronidazole for anaerobic coverage. SBP monotherapy. Once-daily dosing.
Metronidazole (Flagyl)	Anaerobes (Bacteroides fragilis)	500 mg IV/PO q8h	Anaerobic coverage when using non-anaerobic-active GNR agents (ceftriaxone, fluoroquinolones). Excellent oral bioavailability. Disulfiram reaction with alcohol. Metallic taste.
Ertapenem (Invanz)	GNRs (incl ESBL) + anaerobes. NOT Pseudomonas.	1g IV q24h	Once-daily carbapenem for community-acquired cIAI. DOES cover ESBL. Does NOT cover Pseudomonas, Acinetobacter, or Enterococcus. Good for step-down OPAT.
Ciprofloxacin (Cipro)	GNRs (incl Pseudomonas)	400 mg IV q12h or 500 mg PO BID	Alternative for penicillin/cephalosporin allergy. Pair with metronidazole. Rising resistance limits empiric use. Check local antibiogram. FDA black box warnings (tendon, neuropathy).

📋 On Rounds

What is the diagnostic threshold for SBP and what should you do immediately?

Ascitic fluid PMN ≥250/mm³ = SBP. Start ceftriaxone 2g IV daily immediately, do not wait for cultures (40% will be culture-negative). Add IV albumin (1.5 g/kg day 1, 1 g/kg day 3) if Cr >1, BUN >30, or bilirubin >4, reduces hepatorenal syndrome and mortality (Sort trial). Treat for 5 days. No source control needed.

Why is source control more important than antibiotics in complicated IAI?

Antibiotics cannot sterilize undrained collections or dead tissue. Abscesses have low blood flow and low antibiotic penetration. Necrotic tissue and pus are incubators for ongoing bacterial growth. Without source control, antibiotics will fail, the patient will remain septic despite broadest-spectrum coverage. Source control (drain abscess, repair perforation, remove necrotic tissue) is the definitive treatment; antibiotics are adjunctive.

How does the STOP-IT trial change antibiotic duration for IAI?

The STOP-IT trial (2015) showed that 4 days (96 hours) of antibiotics after adequate source control is equivalent to traditional longer courses (median 8 days) for complicated IAI. No difference in surgical site infection, recurrent IAI, or death. Shorter courses reduce antibiotic exposure, C. diff risk, resistance emergence, and cost. Key requirement: adequate source control must be achieved first.

What does polymicrobial growth from ascitic fluid tell you?

Polymicrobial ascitic fluid culture suggests secondary peritonitis (bowel perforation or surgical leak), not SBP. SBP is almost always monomicrobial. Additional clues: ascitic protein >1 g/dL, glucose <50 mg/dL, LDH > serum upper limit. This is a surgical emergency, get urgent CT abdomen and surgical consultation. The patient needs source control, not just antibiotics.

What is Charcot's triad and Reynolds' pentad?

Charcot triad (cholangitis): (1) fever/chills, (2) jaundice, (3) RUQ pain. Present in ~50–70% of cholangitis. Reynolds pentad adds: (4) altered mental status, (5) hypotension/shock. Reynolds pentad indicates severe/suppurative cholangitis with sepsis, requires emergent biliary drainage (ERCP). Do not wait for imaging to start antibiotics if Reynolds pentad is present.

📣 Sample Presentation

One-Liner

"Mr. Thompson is a 58-year-old man with decompensated cirrhosis (Child-Pugh C) admitted with fever, diffuse abdominal pain, and worsening hepatic encephalopathy. Diagnostic paracentesis showed PMN 820/mm³, consistent with spontaneous bacterial peritonitis."

Key Points to Cover on Rounds

SBP diagnosed by ascitic PMN 820, started ceftriaxone 2g IV daily. Ascitic fluid culture sent in blood culture bottles at bedside. Blood cultures ×2 drawn. IV albumin 1.5 g/kg given (Cr 1.4, BUN 38) per Sort trial protocol, day 3 albumin 1 g/kg planned. BMP monitoring for hepatorenal syndrome. Lactulose continued for encephalopathy. Repeat paracentesis planned at 48h to confirm ≥25% PMN decrease. Will complete 5-day course. SBP prophylaxis (ciprofloxacin or TMP-SMX) to be started after treatment for secondary prevention.

⚡ Summary

Summary

Source Control

Cornerstone of cIAI. Surgery, percutaneous drainage, or ERCP. Antibiotics alone insufficient for undrained collections.

Empiric Therapy

Mild CA: ceftriaxone + metronidazole. Severe: pip-tazo or meropenem. HA: meropenem ± vancomycin ± antifungal.

SBP

PMN ≥250 = SBP. Ceftriaxone + albumin (if renal/liver criteria met). 5 days. Prophylaxis after first episode.

Cholangitis

Charcot triad + Reynolds pentad. ERCP within 24h (emergent if severe). Pip-tazo or ceftriaxone + metronidazole.

Duration

STOP-IT: 4 days after adequate source control. SBP: 5 days. Cholangitis: 4–7 days post-drainage.

Red Flags

Polymicrobial ascites = secondary peritonitis (surgery). Free air = perforation (emergent OR). Lactate rising = inadequate source control.

📄 One Pager

Intra-Abdominal Infections, Quick Reference Card

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

INTRA-ABDOMINAL INFECTIONS, AT A GLANCE

🔑 Principle: Source control + antibiotics. Antibiotics alone fail without drainage/surgery.
💊 Mild CA-cIAI: Ceftriaxone + metronidazole, or ertapenem. Severe: pip-tazo or meropenem.
🔬 SBP: PMN ≥250 = treat. Ceftriaxone 2g daily × 5d + albumin. Polymicrobial = secondary peritonitis.
🟡 Cholangitis: Charcot triad → ERCP within 24h. Reynolds pentad = emergent drainage.
⏱️ Duration: STOP-IT: 4 days after adequate source control. Shorter is better.
⚠️ Escalate: HA/post-surgical: meropenem ± vancomycin ± antifungal. De-escalate by culture.