Step 2 CK · Internal Medicine · Infectious Disease

Sepsis & Bacteremia

Name: Sepsis & Bacteremia
Creator: Veli Bakalov, MD

The Hour-1 bundle, septic-shock definition, and when to pull the line

Infectious Disease·Sepsis & Bloodstream Infections·4 min read·9 high-yield points·Reviewed by Veli Bakalov, MD @HemeOncBuddy

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Sepsis-3: sepsis = life-threatening organ dysfunction from a dysregulated response to infection (acute SOFA rise ≥2); infection or bacteremia alone is not sepsis.
Septic shock = vasopressors needed for MAP ≥65 AND lactate >2 mmol/L despite adequate fluids; mortality often exceeds 40%.
qSOFA (any 2 of 3): respiratory rate ≥22, systolic BP ≤100, altered mentation; it predicts poor outcome, but SSC 2021 advises against using it alone as a screening tool (prefer SIRS, NEWS or MEWS), and a lactate ≥4 signals severe hypoperfusion.
Hour-1 bundle: lactate, blood cultures BEFORE antibiotics (≥2 sets, never delaying antibiotics >45 min), broad-spectrum antibiotics, 30 mL/kg crystalloid for hypotension or lactate ≥4, vasopressors to MAP ≥65.
Give 30 mL/kg balanced crystalloid within 3 hours, then judge further fluid with dynamic measures (passive leg raise, pulse pressure variation), not CVP.
Norepinephrine is the first-line vasopressor, then vasopressin, then epinephrine; add IV hydrocortisone (~200 mg/day) for ongoing vasopressor need (norepinephrine or epinephrine ≥0.25 mcg/kg/min for at least 4 hours).
Source control ideally within 6–12 hours: drain abscesses, remove infected devices, debride necrotic tissue, relieve obstruction.
De-escalate to the narrowest effective antibiotic once cultures return, switch IV to oral when stable, and stop if infection is excluded (procalcitonin can help).
CLABSI (line >48 h, no other source; coagulase-negative staph most common): differential time to positivity; remove the catheter for S. aureus, Pseudomonas, Candida, tunnel infection, or instability.

Definitions and recognition

Sepsis is infection plus organ dysfunction. Under Sepsis-3, sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, marked by an acute rise in SOFA score of ≥2. Infection alone, or a positive blood culture (bacteremia), is not sepsis; the organ injury defines it. SOFA scores six systems: respiratory (PaO₂/FiO₂), coagulation (platelets), liver (bilirubin), cardiovascular (MAP and pressors), CNS (GCS), and renal (creatinine or urine output).

Septic shock is the subset of sepsis that needs vasopressors to keep MAP ≥65 mmHg AND has a lactate >2 mmol/L despite adequate fluid resuscitation. Its mortality often exceeds 40 percent, far higher than sepsis without shock.

Sepsis vs septic shock

Feature	Sepsis	Septic shock
Defining feature	Organ dysfunction (SOFA +2)	Pressors needed for MAP ≥65 despite fluids
Lactate	Variable	>2 mmol/L despite fluids
Mortality	Lower	Often >40%

qSOFA: 22, 100, confused. qSOFA flags high-risk infection at the bedside with any 2 of: respiratory rate ≥22, systolic BP ≤100 mmHg, and altered mentation (GCS <15). It needs no labs and flags patients at risk of a poor outcome, but the 2021 Surviving Sepsis Campaign recommends against using qSOFA alone as a single screening tool, compared with SIRS, NEWS or MEWS, and a negative score does not exclude sepsis.

RR ≥22respiratory rate

SBP ≤100systolic BP, mmHg

GCS <15altered mentation

Lactate marks hypoperfusion. Lactate ≥2 mmol/L is concerning, and ≥4 signals severe shock and mandates aggressive resuscitation. Repeat it to track clearance as a resuscitation target.

The Hour-1 bundle

Sequence and speed decide survival. The Surviving Sepsis Hour-1 bundle packs the highest-yield steps into the first hour:

Lactate + blood culturesCultures before antibiotics
Broad-spectrum antibioticsWithin the first hour
30 mL/kg crystalloidIf hypotensive or lactate ≥4
Vasopressors to MAP ≥65Norepinephrine first, during or after fluids

Sepsis Hour-1 bundle

Cultures first, then antibiotics fast. Obtain at least 2 sets of blood cultures plus source cultures (urine, sputum, wound) before antibiotics, but never delay antibiotics beyond about 45 minutes to get them. Early appropriate antibiotics are among the strongest survival levers in sepsis. Empiric coverage is broad and matched to the likely source, typically an antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, or a carbapenem) plus vancomycin when MRSA is a concern.

Resuscitation and supportive care

30 mL/kg crystalloid up front. Give 30 mL/kg of balanced crystalloid such as lactated Ringer within the first 3 hours for sepsis-induced hypotension or lactate ≥4. Then reassess volume responsiveness with dynamic measures (passive leg raise, pulse pressure variation) rather than fixed CVP targets, because excess fluid floods the lungs.

Norepinephrine is the first-line pressor. When fluids fail to restore MAP ≥65, start norepinephrine, whose balanced α effect (with some β1 support) makes it the initial agent in septic shock. Add vasopressin, then epinephrine, if needed.

Vasoactive drugs in septic shock

Agent	Action	Role
Norepinephrine	α1 > β1: vasoconstriction plus modest inotropy	First-line
Vasopressin	V1 vasoconstriction	Second; spares norepinephrine
Epinephrine	α and β agonist	Third-line add-on
Dobutamine	β1 inotrope	Add for cardiac dysfunction with persistent hypoperfusion
Dopamine	Dose-dependent dopamine, β, α effects	Avoid: more arrhythmias

Goal for all: MAP ≥65 mmHg.

Steroids for refractory shock. For septic shock that remains vasopressor-dependent despite adequate fluids and norepinephrine, add IV hydrocortisone (typically 200 mg/day); the SSC threshold is norepinephrine or epinephrine at 0.25 mcg/kg/min or more for at least 4 hours after starting. Glucose control (insulin once glucose reaches about 180 mg/dL) and lung-protective ventilation for ARDS (low tidal volumes, about 6 mL/kg of predicted body weight) round out supportive care.

Source control and stewardship

Find and control the source. Antibiotics cannot sterilize an undrained collection or infected hardware. Drain abscesses, remove infected catheters or devices, debride necrotic tissue, and relieve obstruction (e.g., an obstructing stone with pyelonephritis) as soon as feasible, ideally within 6–12 hours.

De-escalate once cultures return. Reassess daily: narrow broad-spectrum antibiotics to the identified organism and sensitivities, switch IV to oral when stable, and stop antibiotics if infection is excluded. Procalcitonin trends can support discontinuation.

Bacteremia and central-line infections

CLABSI is bacteremia with a central line in place >48 hours and no other source, commonly from S. epidermidis, S. aureus, gram-negative rods, or Candida. Paired cultures drawn through the catheter and from a peripheral vein show differential time to positivity, with the catheter sample turning positive first. Remove the catheter for S. aureus, Pseudomonas, Candida, tunnel infection, or hemodynamic instability.

Coagulase-negative staph is the most common CLABSI organism, but S. aureus, Pseudomonas, and Candida always mean pull the line.

Prevention relies on chlorhexidine skin preparation, full barrier precautions at insertion, avoiding the femoral site, and daily review so unneeded lines come out.

Reading a positive blood culture

Isolate	Meaning	Next step
S. aureus	Never a contaminant	Remove lines, repeat cultures to document clearance, echocardiogram, prolonged IV therapy
Coagulase-negative staph in one set	Often a skin contaminant	Repeat cultures; treat if multiple sets or a line or prosthesis is involved
Candida	Never a contaminant	Remove lines, echinocandin, dilated eye exam
Streptococcus gallolyticus (bovis)	Colon cancer association	Colonoscopy and echocardiogram