Master Surgery
for USMLE Step 2 CK

Core Concepts

Surgical practice emphasizes a systematic approach to patient care, from pre-operative assessment and risk stratification through intra-operative execution and post-operative management of complications. Core principles include prompt recognition and management of surgical emergencies, infection control, fluid/electrolyte balance, acid-base disorders, and appropriate pain management. Understanding shock pathophysiology and resuscitation, wound healing, and surgical nutrition is critical.

• **Pre-operative Care**: Risk assessment (e.g., ASA classification, RCRI for cardiac risk), informed consent, NPO status, DVT/PE prophylaxis (heparin, SCDs), pre-op antibiotics (1 hr prior to incision).
• **Shock**: Inadequate tissue perfusion leading to cellular dysfunction. Recognize types: Hypovolemic (hemorrhage, dehydration), Cardiogenic (MI, arrhythmia), Obstructive (tamponade, tension pneumothorax, PE), Distributive (sepsis, anaphylaxis, neurogenic). Initial management: ABCs, IV fluids (crystalloids), identify/treat underlying cause.
• **Surgical Infection**: Source control (drainage, debridement), empiric broad-spectrum antibiotics, fluid resuscitation. Common post-op infections: UTI, wound infection, pneumonia, C. difficile.
• **Wound Healing**: Stages (inflammation, proliferation, remodeling). Factors affecting healing: nutrition, blood supply, infection, foreign bodies, systemic disease (diabetes). Wound closure types: primary, secondary (granulation), tertiary (delayed primary).
• **Post-operative Complications**: Fever (Wind-Water-Wound-Walk-Wonder drugs), atelectasis, DVT/PE, ileus, anastomotic leak, acute kidney injury, CVA/MI. Early ambulation, pain control, DVT prophylaxis, and pulmonary hygiene are vital.
• **Fluid/Electrolyte/Acid-Base**: Post-op fluid management (crystalloids), monitoring electrolytes (Na, K, Cl, HCO3), recognizing metabolic acidosis (sepsis, ischemia) or alkalosis (vomiting, NG suction).

Clinical Presentation

• **Acute Abdomen**: Abdominal pain (sudden, severe, progressive), nausea, vomiting, change in bowel habits, distension, guarding, rigidity, rebound tenderness. Fever, tachycardia, hypotension may indicate advanced disease or sepsis.
• **Trauma**: Depends on mechanism. Signs of hemorrhage (tachycardia, hypotension, pallor), altered mental status, visible injuries (lacerations, deformities), specific findings (e.g., tracheal deviation in tension pneumothorax, pulsatile mass in AAA).
• **Lump/Mass**: Palpable mass, associated pain or tenderness, skin changes (erythema, ulceration), size/consistency changes, regional lymphadenopathy, constitutional symptoms (weight loss, fatigue) suggesting malignancy.
• **Vascular Issues**:
  • **Acute Limb Ischemia**: Sudden onset of 6 P's: Pain, Pallor, Pulselessness, Paresthesia, Paralysis, Poikilothermia.
  • **DVT**: Unilateral leg swelling, pain, erythema, warmth.
  • **Peripheral Artery Disease (PAD)**: Intermittent claudication, rest pain, non-healing ulcers.
• **GI Bleed**: Hematemesis, melena, hematochezia, associated with orthostasis, tachycardia, pallor.

Diagnosis (Gold Standard)

Diagnosis in surgery relies on a combination of clinical assessment, imaging, and sometimes invasive procedures. For most abdominal pathologies, CT with IV contrast is often the most informative. Biopsy remains the gold standard for definitive diagnosis of malignancy.

• **Acute Abdomen**: CT scan (abdomen/pelvis with IV/oral contrast), upright CXR (for free air under diaphragm), focused abdominal sonography for trauma (FAST) for free fluid.
• **Trauma**: Primary/secondary survey, X-rays (C-spine, chest, pelvis), FAST exam, CT scan (head, C-spine, chest, abdomen/pelvis) as indicated. Angiography for vascular injury.
• **Lump/Mass**: Biopsy (fine-needle aspiration, core needle biopsy, excisional biopsy) is the gold standard for tissue diagnosis. Imaging (ultrasound, CT, MRI) guides biopsy and assesses extent.
• **Vascular**:
  • **Acute Limb Ischemia/PAD**: Angiography (CT or catheter-based) is gold standard; duplex ultrasound for screening.
  • **DVT**: Duplex ultrasound.
  • **AAA**: CT angiography is gold standard for planning repair; ultrasound for screening/monitoring.
• **GI Bleed**: Endoscopy (EGD for UGI, colonoscopy for LGI). Angiography for massive, refractory bleeding.

Management (First Line)

First-line management prioritizes stabilization, resuscitation, and addressing the life-threatening cause. This typically involves immediate ABCs, fluid resuscitation, and prompt surgical intervention for emergencies. Specific conditions require targeted medical or surgical treatments.

• **Resuscitation**: ABCs (Airway, Breathing, Circulation), large-bore IV access, crystalloids (lactated Ringer's or normal saline), blood products for hemorrhage.
• **Acute Abdomen (Surgical)**: Emergency surgical exploration (laparotomy/laparoscopy) for peritonitis, perforation, obstruction, ischemia, or intractable pain. Appendectomy for appendicitis, cholecystectomy for acute cholecystitis.
• **Trauma**: Hemorrhage control (direct pressure, tourniquet, surgical exploration), airway management (intubation), ventilation, chest tube for pneumo/hemothorax, pelvic stabilization. Definitive repair of injuries.
• **Sepsis/Septic Shock**: IV fluid resuscitation, empiric broad-spectrum antibiotics, source control (drainage, debridement), vasopressors (norepinephrine) if refractory hypotension.
• **Acute Limb Ischemia**: Immediate vascular surgery consult for revascularization (embolectomy, bypass). Anticoagulation (heparin).
• **DVT**: Anticoagulation (heparin, then warfarin/DOACs). IVC filter if contraindication to anticoagulation.
• **GI Bleed**: Endoscopic hemostasis (clipping, cautery, epinephrine injection). IV proton pump inhibitors (PPIs) for UGI bleed. Surgical intervention for refractory bleeding.