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1. General Principles & Basic Science MCQs

Practice Set 526 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 10501

Topic: 1. General Principles & Basic Science

Which of the following best explains why obesity is a significant risk factor for surgical site infections (SSIs) and can complicate sepsis management in orthopedic patients?

. Obese patients have inherently weaker immune systems.
. Increased adipose tissue has poor vascularity, leading to impaired antibiotic delivery and wound healing.
. Obesity causes chronic systemic inflammation, mimicking SIRS.
. Obese patients are more prone to aspiration pneumonia.
. Higher body mass index (BMI) directly increases bacterial virulence.

Correct Answer & Explanation

. Increased adipose tissue has poor vascularity, leading to impaired antibiotic delivery and wound healing.

Explanation

Obesity is a well-recognized risk factor for SSIs. Increased adipose tissue often has poor vascularity and oxygenation, creating an ideal environment for bacterial growth and impairing both the delivery of antibiotics to the surgical site and the wound healing process. This compromised tissue environment makes infections more likely and harder to eradicate, thereby increasing the risk of progression to sepsis. While obesity can be associated with chronic inflammation, impaired immune function (not inherently weaker), and other comorbidities, the vascularity of adipose tissue is a direct mechanical and physiological factor for SSI risk.

Question 10502

Topic: 1. General Principles & Basic Science

Regarding monitoring renal function in sepsis, which biomarker is a more sensitive and earlier indicator of acute kidney injury (AKI) compared to serum creatinine?

. Blood urea nitrogen (BUN)
. Urinary sodium excretion
. Fractional excretion of sodium (FENa)
. Neutrophil gelatinase-associated lipocalin (NGAL)
. Serum potassium

Correct Answer & Explanation

. Neutrophil gelatinase-associated lipocalin (NGAL)

Explanation

Neutrophil gelatinase-associated lipocalin (NGAL) is one of several emerging biomarkers (along with Kidney Injury Molecule-1 (KIM-1), Cystatin C, etc.) that are more sensitive and earlier indicators of acute kidney injury (AKI) compared to serum creatinine. Creatinine takes time to rise as kidney function declines and can be influenced by muscle mass. NGAL rises much earlier in response to kidney tubular injury, making it a valuable tool for early detection and prognostication of AKI in sepsis. BUN, urinary sodium, and FENa are also used but less sensitive as early indicators.

Question 10503

Topic: 1. General Principles & Basic Science

In the initial management of a patient with suspected sepsis following a large orthopedic surgery, how should blood cultures be obtained?

. One set from a peripheral vein and one set from an existing central venous catheter.
. Two sets from different peripheral sites, preferably before antibiotic administration.
. One set from an arterial line and one set from an existing peripheral IV.
. Only from the suspected source of infection (e.g., wound swab).
. Blood cultures are not essential if empiric antibiotics are started promptly.

Correct Answer & Explanation

. Two sets from different peripheral sites, preferably before antibiotic administration.

Explanation

For optimal diagnosis of bacteremia in sepsis, at least two sets of blood cultures (one set typically consists of aerobic and anaerobic bottles) should be drawn from different peripheral venipuncture sites. This helps distinguish true bacteremia from skin contaminants. It is crucial to obtain culturesbeforeinitiating broad-spectrum antibiotics whenever possible, as antibiotic administration can significantly reduce the yield of cultures. Drawing from existing central lines or only from local sources is less reliable for systemic infection.

Question 10504

Topic: 1. General Principles & Basic Science

Which of the following classes of medications should be used with caution, or altogether avoided, in patients with severe sepsis and septic shock due to their potential to exacerbate hypotension or worsen organ perfusion?

. Crystalloid fluids
. Beta-blockers
. Broad-spectrum antibiotics
. Insulin
. Opioid analgesics

Correct Answer & Explanation

. Beta-blockers

Explanation

Beta-blockers can depress myocardial contractility and blunt the compensatory tachycardia response, potentially worsening hypotension and further compromising organ perfusion in patients with severe sepsis and septic shock who are often already hypovolemic and have high sympathetic drive. While they might be continued for specific indications in stable patients, their use requires careful consideration and often down-titration or temporary cessation in shock states. The other options are generally either beneficial (fluids, antibiotics, insulin for hyperglycemia) or have less profound hemodynamic effects (opioids if titrated carefully).

Question 10505

Topic: 1. General Principles & Basic Science

What is the recommended target glucose range for critically ill patients with sepsis once initial stabilization is achieved?

. 80-110 mg/dL (4.4-6.1 mmol/L)
. 110-140 mg/dL (6.1-7.8 mmol/L)
. 140-180 mg/dL (7.8-10.0 mmol/L)
. 180-220 mg/dL (10.0-12.2 mmol/L)
. No specific target, just avoid hypoglycemia

Correct Answer & Explanation

. 140-180 mg/dL (7.8-10.0 mmol/L)

Explanation

Current Surviving Sepsis Campaign guidelines recommend targeting a blood glucose level of <180 mg/dL (10.0 mmol/L) for critically ill patients with sepsis. While previous guidelines advocated for stricter control (e.g., 80-110 mg/dL), studies showed that aggressive tight glucose control increased the risk of hypoglycemia without improving mortality. Therefore, maintaining glucose between 140-180 mg/dL is considered a safer and more pragmatic approach.

Question 10506

Topic: 1. General Principles & Basic Science

Which of the following is a characteristic feature of the hyperdynamic phase of septic shock?

. Low cardiac output, high systemic vascular resistance
. Low cardiac output, low systemic vascular resistance
. High cardiac output, high systemic vascular resistance
. High cardiac output, low systemic vascular resistance
. Normal cardiac output, normal systemic vascular resistance

Correct Answer & Explanation

. High cardiac output, low systemic vascular resistance

Explanation

The hyperdynamic phase of septic shock is characterized by a high cardiac output (initially compensatory, driven by catecholamines and fluid resuscitation) coupled with profoundly low systemic vascular resistance (due to widespread vasodilation). This leads to a wide pulse pressure and warm extremities (warm shock). As shock progresses and myocardial dysfunction ensues, cardiac output may fall, leading to a hypodynamic phase, but the initial phase is typically hyperdynamic.

Question 10507

Topic: Infection, Pharmacology & VTE

Regarding DVT prophylaxis in an orthopedic patient with severe sepsis, which statement is most appropriate?

. DVT prophylaxis should be withheld due to the risk of bleeding in DIC.
. Mechanical prophylaxis (e.g., intermittent pneumatic compression devices) is contraindicated in septic patients.
. Pharmacological prophylaxis (e.g., LMWH) should be initiated unless contraindications exist.
. All septic patients require placement of an inferior vena cava (IVC) filter.
. Only patients undergoing major orthopedic surgery require DVT prophylaxis in sepsis.

Correct Answer & Explanation

. Pharmacological prophylaxis (e.g., LMWH) should be initiated unless contraindications exist.

Explanation

Patients with severe sepsis are at high risk for venous thromboembolism (VTE). Pharmacological prophylaxis with low molecular weight heparin (LMWH) or unfractionated heparin (UFH) is recommended unless contraindications (e.g., active bleeding, severe thrombocytopenia) exist. If pharmacological agents are contraindicated, mechanical prophylaxis (intermittent pneumatic compression devices) should be used. Withholding prophylaxis due to DIC is not universal; careful risk-benefit assessment is needed. IVC filters are reserved for specific situations. All critically ill septic patients require DVT prophylaxis, not just those with major orthopedic surgery.

Question 10508

Topic: Infection, Pharmacology & VTE

What is the primary role of echocardiography in the management of septic shock?

. To diagnose the source of infection (e.g., endocarditis).
. To assess cardiac function, fluid responsiveness, and differentiate shock types.
. To evaluate for pulmonary embolism.
. To guide placement of central venous catheters.
. To measure central venous pressure (CVP) non-invasively.

Correct Answer & Explanation

. To assess cardiac function, fluid responsiveness, and differentiate shock types.

Explanation

Echocardiography (transthoracic or transesophageal) is an invaluable tool in the management of septic shock. It allows for rapid, non-invasive assessment of cardiac function (contractility, ejection fraction), volume status, and fluid responsiveness. It can help differentiate between different types of shock (e.g., distributive, cardiogenic, obstructive) when the cause is unclear, and can guide fluid and vasopressor therapy. While it can sometimes identify endocarditis (a source), its primary role in general shock management is hemodynamic assessment. It's not the primary tool for PE, CVC guidance, or CVP measurement.

Question 10509

Topic: Infection, Pharmacology & VTE

A 58-year-old male with a history of recurrent osteomyelitis in his left foot develops sepsis. Blood cultures grow Pseudomonas aeruginosa. What is the most appropriate initial empiric antibiotic regimen, knowing the high prevalence of resistant strains and potential for sepsis?

. Oral Ciprofloxacin monotherapy
. Intravenous Ceftriaxone
. Intravenous Piperacillin-tazobactam or a Carbapenem (e.g., Meropenem)
. Intravenous Vancomycin
. Oral Amoxicillin-Clavulanate

Correct Answer & Explanation

. Intravenous Piperacillin-tazobactam or a Carbapenem (e.g., Meropenem)

Explanation

Pseudomonas aeruginosa is a common pathogen in osteomyelitis, especially in patients with a history of recurrent infections or diabetes. It is often resistant to many common antibiotics. For severe infections and sepsis involving Pseudomonas, antipseudomonal beta-lactams like Piperacillin-tazobactam or Carbapenems (e.g., Meropenem, Imipenem) are typically first-line, often in combination with an aminoglycoside or fluoroquinolone if severe. Oral ciprofloxacin monotherapy is insufficient for severe sepsis. Ceftriaxone lacks robust antipseudomonal activity. Vancomycin covers Gram-positives, not Pseudomonas. Amoxicillin-Clavulanate is not active against Pseudomonas.

Question 10510

Topic: 1. General Principles & Basic Science
When assessing a patient for sepsis in the emergency department, the quick SOFA (qSOFA) score is a rapid bedside tool. Which of the following parameters are included in the qSOFA score?
. Temperature, heart rate, respiratory rate
. Glasgow Coma Scale, blood pressure, serum creatinine
. Respiratory rate, altered mental status, systolic blood pressure
. Lactate, platelet count, bilirubin
. PaO2/FiO2 ratio, mean arterial pressure, urine output

Correct Answer & Explanation

. Respiratory rate, altered mental status, systolic blood pressure

Explanation

The qSOFA (quick SOFA) score is a simplified bedside prompt to identify patients at higher risk of poor outcomes from sepsis. It consists of three criteria: altered mental status (GCS <15), systolic blood pressure ≤100 mmHg, and respiratory rate ≥22 breaths per minute. A score of 2 or more positive criteria is associated with increased mortality and prolonged ICU stay, prompting further investigation for sepsis and organ dysfunction. The other options contain elements of the full SOFA or SIRS criteria, but not the specific qSOFA components.

Question 10511

Topic: 1. General Principles & Basic Science

A patient with severe sepsis is receiving broad-spectrum antibiotics. After 72 hours, his clinical condition has not improved, and he remains febrile with persistent organ dysfunction. Blood cultures are repeatedly negative. What is the most important next step in management?

. Discontinue antibiotics as cultures are negative.
. Add antifungal agents empirically.
. Perform a thorough search for undrained collections or persistent foci of infection.
. Switch to narrower-spectrum antibiotics to reduce resistance.
. Increase the dose of current antibiotics.

Correct Answer & Explanation

. Perform a thorough search for undrained collections or persistent foci of infection.

Explanation

If a patient with severe sepsis fails to improve after 48-72 hours of appropriate broad-spectrum antibiotics, and especially if cultures are negative, the most critical step is to thoroughly search for undrained collections, occult foci of infection, or non-infectious causes of SIRS. Persistence of infection despite antibiotics often indicates an abscess, empyema, infected hardware, or necrotic tissue requiring surgical or percutaneous drainage/debridement (source control). Simply discontinuing or changing antibiotics without identifying the source is premature and potentially harmful. Adding antifungals might be considered later if fungal infection is suspected, but source control is paramount first.

Question 10512

Topic: Infection, Pharmacology & VTE

A 72-year-old patient with well-controlled type 2 diabetes and a history of penicillin allergy (rash) is scheduled for an elective total knee arthroplasty. According to prophylactic antibiotic guidelines and general principles, which of the following antibiotic regimens is the most appropriate prophylactic choice to prevent periprosthetic joint infection?

. Vancomycin alone, given penicillin allergy.
. Cefazolin, as the rash is not a severe allergy and provides excellent coverage.
. Clindamycin alone, providing good gram-positive coverage and safe for penicillin allergy.
. Vancomycin plus Gentamicin, for broad-spectrum coverage.
. Daptomycin, due to its efficacy against resistant organisms.

Correct Answer & Explanation

. Vancomycin alone, given penicillin allergy.

Explanation

For patients with a history of penicillin allergy, especially non-severe reactions like a rash, a cephalosporin such as cefazolin might still be considered due to its excellent efficacy and narrow spectrum. However, for a board-level question and especially in the context of prophylaxis for arthroplasty where the consequence of infection is severe, Vancomycin is the safest and most commonly recommended alternative in patients with a stated penicillin allergy, particularly for a 'rash' which could still represent a Type I hypersensitivity. Cefazolin carries a low but present cross-reactivity risk. Clindamycin is an alternative but often preferred for patients with severe beta-lactam allergies (anaphylaxis) or if methicillin-resistant S. aureus (MRSA) coverage is specifically desired and Vancomycin cannot be used; it has less robust data than cefazolin or vancomycin. Daptomycin is generally reserved for treating established infections rather than prophylaxis. Gentamicin is not typically used for routine prophylaxis in TKA due to potential nephrotoxicity and narrow spectrum for skin flora.

Question 10513

Topic: Infection, Pharmacology & VTE

A 60-year-old patient with poorly controlled diabetes and a history of chronic osteomyelitis of the distal tibia is scheduled for a debridement and external fixation. According to the general principles for prophylactic antibiotic use, which of the following is an additional significant indication for administering prophylactic antibiotics in this patient, beyond the surgical procedure itself?

. His history of chronic osteomyelitis, requiring long-term suppression.
. Anticipated duration of external fixation exceeding 6 weeks.
. Poorly controlled diabetes, categorizing him as a high-risk patient.
. Age exceeding 60 years, increasing general surgical risk.
. The specific location of the infection (distal tibia) being prone to recurrence.

Correct Answer & Explanation

. Poorly controlled diabetes, categorizing him as a high-risk patient.

Explanation

The general principles for prophylactic antibiotic use specifically state: '(4) Patients with high-risk factors for infection, such as advanced age, malnutrition, diabetes, granulocytopenia; or those undergoing steroid, immunosuppressant, or anticancer drug therapy, and those with immune dysfunction requiring surgery.' Poorly controlled diabetes significantly impairs immune function and microvascular circulation, placing the patient at a much higher risk for surgical site infection. While chronic osteomyelitis is a concern, the question asks for anadditionalindication forprophylacticuse, distinct from the treatment of his existing infection. His diabetes is a direct 'high-risk factor' for infection prophylaxis.

Question 10514

Topic: Infection, Pharmacology & VTE

A 3-year-old child presents with a high fever, refusal to bear weight on the right leg, and extreme pain with passive range of motion of the right hip. Inflammatory markers (ESR, CRP) are significantly elevated. Which of the following is the most appropriate immediate diagnostic and therapeutic step?

. Order a plain radiograph of the hip and femur.
. Start oral antibiotics and observe for improvement.
. Perform an MRI of the hip to identify synovitis.
. Aspirate the hip joint immediately and initiate empiric intravenous antibiotics.
. Refer to physical therapy for range of motion exercises.

Correct Answer & Explanation

. Aspirate the hip joint immediately and initiate empiric intravenous antibiotics.

Explanation

The presentation (high fever, refusal to bear weight, severe pain with passive ROM, elevated inflammatory markers) in a child is highly suspicious for septic arthritis of the hip, which is an orthopedic emergency. Delayed diagnosis and treatment can lead to rapid articular cartilage destruction, avascular necrosis, and growth disturbances. Therefore,immediatehip joint aspiration (to obtain fluid for culture and cell count) and initiation of empiric intravenous antibiotics are crucial. Radiographs are often normal early on. MRI can be helpful but should not delay aspiration and antibiotics. Oral antibiotics are insufficient. Physical therapy is contraindicated in acute septic arthritis.

Question 10515

Topic: Surgical Anatomy & Approaches

A 50-year-old female presents with progressive weakness and muscle atrophy in the deltoid and biceps after a motor vehicle accident that caused a clavicle fracture. Examination reveals diminished sensation over the lateral aspect of the shoulder. Which nerve root or peripheral nerve is most likely involved?

. C5 nerve root.
. C6 nerve root.
. C7 nerve root.
. Axillary nerve.
. Musculocutaneous nerve.

Correct Answer & Explanation

. C5 nerve root.

Explanation

Weakness of the deltoid and biceps, along with sensory loss over the lateral aspect of the shoulder, points to involvement of the C5 nerve root. The deltoid is primarily innervated by the axillary nerve (C5-C6), and the biceps by the musculocutaneous nerve (C5-C7). Both of these nerves derive significant input from C5. A clavicle fracture can cause brachial plexus injury, and C5 is a common component involved. The axillary nerve is a peripheral nerve, but the question asks about nerve root or peripheral nerve and C5 is the root level providing the most prominent motor and sensory deficits described.

Question 10516

Topic: Infection, Pharmacology & VTE

A 55-year-old male presents with severe foot pain, erythema, swelling, and warmth, primarily affecting the first metatarsophalangeal (MTP) joint. He has a history of poorly controlled hypertension and kidney stones. Aspiration of the joint reveals negatively birefringent needle-shaped crystals. What is the most likely diagnosis?

. Septic arthritis.
. Pseudogout.
. Rheumatoid arthritis.
. Gout.
. Cellulitis.

Correct Answer & Explanation

. Gout.

Explanation

The clinical presentation (acute, severe pain, erythema, swelling of the first MTP joint - 'podagra'), patient history (hypertension, kidney stones, often associated with hyperuricemia), and synovial fluid analysis showing negatively birefringent needle-shaped crystals are pathognomonic for gout. Septic arthritis would show a high WBC count and positive cultures. Pseudogout (CPPD) shows positively birefringent rhomboid-shaped crystals. Rheumatoid arthritis is typically polyarticular and chronic. Cellulitis would not have crystals on aspiration.

Question 10517

Topic: 1. General Principles & Basic Science

A 72-year-old male with a history of chronic kidney disease and heart failure is scheduled for a hip fracture repair. According to the general principles, which of the following is the most critical consideration for preventing postoperative acute renal failure, referencing the provided mechanisms?

. Strict avoidance of all NSAIDs.
. Meticulous maintenance of euvolemia and stable hemodynamics throughout the perioperative period.
. Aggressive use of loop diuretics to prevent fluid overload.
. Preoperative dialysis to normalize kidney function.
. Administration of high-dose vitamin D postoperatively.

Correct Answer & Explanation

. Meticulous maintenance of euvolemia and stable hemodynamics throughout the perioperative period.

Explanation

In a patient with pre-existing comorbidities like chronic kidney disease and heart failure, 'renal ischemia' is a major contributor to acute renal failure. Therefore, meticulous maintenance of euvolemia (avoiding both dehydration and fluid overload) and stable hemodynamics (maintaining adequate blood pressure and perfusion) throughout the perioperative period is paramount to prevent further renal injury from hypoperfusion or congestion. Aggressive diuresis could worsen hypovolemia. NSAIDs should indeed be avoided, but maintaining hemodynamics is more encompassing. Preoperative dialysis might be necessary if the patient is uremic but is not a routine preventive measure for all CKD patients. Vitamin D is not relevant to acute renal failure prevention.

Question 10518

Topic: Surgical Anatomy & Approaches

A 35-year-old male presents with sudden onset excruciating left hip pain after a high-energy motor vehicle collision. He is found with his left hip flexed, adducted, and internally rotated. Pulses are palpable distally. Which of the following is the most critical immediate management step?

. Order an MRI of the hip.
. Administer strong analgesics and arrange for emergent closed reduction.
. Prepare for open reduction and internal fixation.
. Perform an arthrocentesis of the hip joint.
. Immobilize the hip in the deformed position and await elective surgery.

Correct Answer & Explanation

. Administer strong analgesics and arrange for emergent closed reduction.

Explanation

The patient's presentation is classic for a posterior hip dislocation. This is an orthopedic emergency due to the high risk of avascular necrosis (AVN) of the femoral head and sciatic nerve injury. The most critical immediate step after assessing neurovascular status and administering analgesia is emergent closed reduction, ideally within 6 hours, to minimize the risk of AVN. Delay can significantly increase the risk of complications. MRI is useful after reduction to assess for occult fractures or soft tissue injuries, but not before emergent reduction. Open reduction is considered if closed reduction fails. Arthrocentesis is not indicated. Immobilizing in the deformed position will exacerbate complications.

Question 10519

Topic: Infection, Pharmacology & VTE

Which of the following imaging modalities is most sensitive for detecting early osteomyelitis?

. Plain radiographs.
. CT scan.
. MRI.
. Bone scintigraphy (technetium-99m).
. Ultrasound.

Correct Answer & Explanation

. MRI.

Explanation

MRI is generally considered the most sensitive imaging modality for detecting early osteomyelitis, often demonstrating changes within 24-48 hours of infection onset. It provides excellent soft tissue contrast, allowing visualization of marrow edema, abscess formation, and soft tissue involvement. Plain radiographs may take 7-10 days to show changes. CT scans are good for bony detail but less sensitive for early marrow changes. Bone scintigraphy is sensitive but not very specific for infection versus other bone activity. Ultrasound can detect soft tissue abscesses but is not ideal for bone marrow changes.

Question 10520

Topic: Infection, Pharmacology & VTE

A patient undergoing total hip arthroplasty for osteoarthritis is at highest risk for which of the following complications in the immediate postoperative period?

. Periprosthetic fracture.
. Avascular necrosis of the femoral head.
. Heterotopic ossification.
. Deep vein thrombosis (DVT) and pulmonary embolism (PE).
. Loosening of the prosthetic components.

Correct Answer & Explanation

. Deep vein thrombosis (DVT) and pulmonary embolism (PE).

Explanation

Patients undergoing major orthopedic surgery, especially total hip arthroplasty, are at highest risk for deep vein thrombosis (DVT) and subsequent pulmonary embolism (PE) in the immediate postoperative period. Prophylactic anticoagulation is standard to mitigate this risk. Periprosthetic fracture, avascular necrosis (of the patient's remaining bone, not a complication of the replaced head), heterotopic ossification, and loosening are also potential complications, but DVT/PE represents the most critical and life-threatening immediate postoperative risk requiring strict preventative protocols.

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