A 23-year-old man comes to the emergency department with an open wound on his right hand. He states that he got into a bar fight about an hour ago. He appears heavily intoxicated and does not remember the whole situation, but he does recall lying on the ground in front of the bar after the fight. He does not recall any history of injuries but does remember a tetanus shot he received 6 years ago. His temperature is 37°C (98.6°F), pulse is 77/min, and blood pressure is 132/78 mm Hg. Examination shows a soft, nontender abdomen. His joints have no bony deformities and display full range of motion. There is a 4-cm (1.6-in) lesion on his hand with the skin attached only on the ulnar side. The wound, which appears to be partly covered with soil and dirt, is irrigated and debrided by the hospital staff. Minimal erythema and no purulence is observed in the area surrounding the wound. What is the most appropriate next step in management?

Application of moist sterile dressing + tetanus vaccine

Apposition of wound edges under tension + rifampin

Surgical treatment with skin flap + ciprofloxacin

Surgical treatment with skin graft + tetanus vaccine

Tension-free apposition of wound edges + sterile dressing

A 56-year-old previously healthy woman with no other past medical history is post-operative day one from an open reduction and internal fixation of a fractured right radius and ulna after a motor vehicle accident. What is one of the primary ways of preventing postoperative pneumonia in this patient?

In-hospital intravenous antibiotics

Three days after undergoing coronary bypass surgery, a 67-year-old man becomes unresponsive and hypotensive. He is intubated, mechanically ventilated, and a central line is inserted. Vasopressin and noradrenaline infusions are begun. A Foley catheter is placed. Six days later, he has high unrelenting fevers. He is currently receiving noradrenaline via an infusion pump. His temperature is 39.6°C (102.3°F), pulse is 113/min, and blood pressure is 90/50 mm Hg. Examination shows a sternal wound with surrounding erythema; there is no discharge from the wound. Crackles are heard at both lung bases. Cardiac examination shows an S3 gallop. Abdominal examination shows no abnormalities. A Foley catheter is present. His hemoglobin concentration is 10.8 g/dL, leukocyte count is 21,700/mm3, and platelet count is 165,000/mm3. Samples for blood culture are drawn simultaneously from the central line and peripheral IV line. Blood cultures from the central line show coagulase-negative cocci in clusters on the 8th postoperative day, and those from the peripheral venous line show coagulase-negative cocci in clusters on the 10th postoperative day. Which of the following is the most likely diagnosis in this patient?

Central line-associated blood stream infection

Catheter-associated urinary tract infection

Ventilator-associated pneumonia

A 38-year-old female presents to the emergency room with fevers, fatigue, and anorexia for over a month. Past medical history includes mild mitral valve prolapse. She underwent an uncomplicated tooth extraction approximately 6 weeks ago. Her vital signs include a temperature of 100.8 F, pulse of 83, blood pressure of 110/77, and SpO2 of 97% on room air. On exam, you note a grade III/VI holosystolic murmur at the apex radiating to the axilla as well as several red, painful nodules on her fingers. Which of the following is the next best course of action?

Obtain blood cultures x3 sites over 1 hour and start empiric antibiotics

Blood cultures are not needed. Start empiric antibiotics

Start anticoagulation with heparin

Consult cardiothoracic surgery for mitral valve replacement

Obtain blood cultures x3 sites over 24 hours and start antibiotics after culture results are available

A 32-year-old woman is supposed to undergo tooth extraction surgery. Physical examination is unremarkable, and she has a blood pressure of 126/84 mm Hg and regular pulse of 72/min. She takes no medications. Which of the following cardiac conditions would warrant antibiotic prophylaxis to prevent infective endocarditis in this patient?

Past history of infective endocarditis

Hypertrophic obstructive cardiomyopathy (HOCM)

Ventricular septal defect (VSD)

Implantable cardioverter defibrillator (ICD)

Three days after being admitted to the hospital because of a fall from the roof of a two-story building, a 27-year-old man is being monitored in the intensive care unit. On arrival, the patient was somnolent and not oriented to person, place, or time. A CT scan of the head showed an epidural hemorrhage that was 45 cm3 in size and a midline shift of 7 mm. Emergency surgery was performed with craniotomy and hematoma evacuation on the day of admission. Perioperatively, a bleeding vessel was identified and ligated. Postoperatively, the patient was transferred to the intensive care unit and placed on a ventilator. His temperature is 37°C (98.6°F), pulse is 67/min, and blood pressure is 117/78 mm Hg. The ventilator is set at a FiO2 of 55%, tidal volume of 520 mL, and positive end-expiratory pressure of 5.0 cm H2O. In addition to intravenous administration of fluids, which of the following is the most appropriate next step in managing this patient's nutrition?

Enteral feeding via nasogastric tube

Enteral feeding using a percutaneous endoscopic gastrostomy (PEG) tube

Twelve days after undergoing total pancreatectomy for chronic pancreatitis, a 62-year-old woman notices oozing from her abdominal wound. She first noticed fluid draining 8 hours ago. Her postoperative course has been complicated by persistent hypotension requiring intravenous fluids and decreased ability to tolerate food. She has type 1 diabetes mellitus and glaucoma. The patient smoked one pack of cigarettes daily for 30 years, but quit 2 years ago. She drank a pint of vodka every day starting at age 20 and quit when she was 35 years old. Her current medications include subcutaneous insulin and timolol eye drops. She appears comfortable. Her temperature is 37°C (98.6°F), pulse is 95/min, and blood pressure is 104/78 mm Hg. The abdomen is soft and mildly tender to palpation. There is a 12-cm vertical wound beginning in the epigastrium and extending caudally. 25 mL of a viscous, dark green substance is draining from the middle of the wound. There is a small amount of dried fluid on the patient's hospital gown. The wound edges are nonerythematous. There is no pus draining from the wound. Laboratory studies show: Hematocrit 38% Leukocyte count 8,000/mm3 Serum Na+ 135 mEq/L Cl- 100 mEq/L K+ 3.4 mEq/L HCO3- 23 mEq/L Urea nitrogen 13 mg/dL Creatinine 1.1 mg/dL Glucose 190 mg/dL Which of the following is the most appropriate next step in management?

Total parenteral nutrition and ostomy pouch

Surgical exploration of the abdomen

Wound debridement and irrigation

Oral food intake and intravenous fluid administration

Recognition and management of SSIs for USMLE Step 3: High-Yield Surgery Lessons

SSI Classification - Bugs on the Prowl

Surgical site infection (SSI) depth by tissue layer

Superficial Incisional SSI:
- Involves skin & subcutaneous tissue.
- Occurs within 30 days of surgery.
- Bugs: S. aureus, Coag-neg Staph, Streptococcus.
Deep Incisional SSI:
- Involves deep soft tissues (fascia & muscle).
- Occurs within 30-90 days (if implant present).
- Bugs: As above + gram-negatives (e.g., E. coli).
Organ/Space SSI:
- Involves any organ/space opened during surgery.
- Occurs within 30-90 days (if implant present).
- Bugs: Specific to the organ (e.g., anaerobes like Bacteroides fragilis in abdominal surgery).

⭐ Most SSIs are caused by the patient's own endogenous flora. Staphylococcus aureus is the #1 culprit overall.

Risk & Prevention - Fortress Against Infection

Patient Factors: Smoking, obesity (BMI > 30), malnutrition (albumin < 3.5), uncontrolled diabetes (HbA1c > 7%), immunosuppression, and nasal S. aureus carriage.
Procedural Factors: Higher wound contamination class, prolonged surgery duration, poor hemostasis (hematoma), and emergency procedures.
Prevention Bundle:
- Pre-op: Glucose control (<180 mg/dL), chlorhexidine showers, hair clipping (no razors), and prophylactic antibiotics within 60 minutes before incision.
- Intra-op: Maintain normothermia, use aseptic technique.
- Post-op: Sterile dressing for 24-48 hours.

⭐ For prophylaxis, Cefazolin is the workhorse. Use Vancomycin or Clindamycin for severe β-lactam allergies. Redose for surgeries >4 hours or with major blood loss (>1500 mL).

Diagnosis & Workup - The Infection Detective

Clinical Picture: Based on signs appearing 5-7 days post-op.
- Local: New pain, erythema, swelling, warmth, or purulent drainage.
- Systemic: Fever (>38°C / 100.4°F), tachycardia, leukocytosis (↑ WBC).
Diagnostic Steps:
- Wound Assessment: Gently probe incision with a sterile swab.
- Microbiology: Obtain wound culture & Gram stain before antibiotics. Blood cultures if systemic signs are present.
- Imaging: Use Ultrasound or CT to detect deep collections or abscesses.

⭐ Infections within 24-48 hours are rare but aggressive; suspect Group A Strep or Clostridium perfringens.

Surgical site infection with wound dehiscence and drainage

Management Strategy - The Clean-Up Crew

Source Control is Paramount: Open the wound, drain purulence, and remove sutures/staples.
Obtain Cultures: Always collect wound cultures before starting antibiotics to guide therapy.
Healing by Secondary Intention: Most opened wounds are packed and allowed to heal from the base up.
📌 Mnemonic (I-C-A): Incise & Drain → Culture → Antibiotics.

⭐ Exam Favorite: Failure of a post-op fever to resolve after 48-72 hours despite empiric antibiotics strongly suggests a collection (abscess) requiring urgent source control, typically surgical drainage.

High‑Yield Points - ⚡ Biggest Takeaways

Most SSIs manifest 5-7 days post-op; suspect Group A Strep or Clostridium if within 48 hours.

Key signs include localized pain, erythema, warmth, and purulent drainage from the incision.

Diagnosis is primarily clinical; wound cultures are for guiding, not delaying, therapy.

Management cornerstone is source control: open the wound, drain abscesses, and debride nonviable tissue.

Use systemic antibiotics only for significant cellulitis (>5 cm) or systemic signs of infection.

Staphylococcus aureus is the most common pathogen responsible for SSIs.

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