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1. General Principles & Basic Science MCQs

Practice Set 525 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 10481

Topic: 1. General Principles & Basic Science
Tranexamic acid (TXA) is widely used in orthopedic surgery to reduce perioperative blood loss. What is the specific mechanism of action of TXA?
. Activates antithrombin III to inhibit factor Xa
. Competitively inhibits the activation of plasminogen to plasmin
. Irreversibly binds and inhibits cyclooxygenase-1 (COX-1)
. Directly inhibits thrombin (Factor IIa)
. Stimulates the release of von Willebrand factor from endothelial cells

Correct Answer & Explanation

. Competitively inhibits the activation of plasminogen to plasmin

Explanation

Tranexamic acid is a synthetic lysine analog that acts as an antifibrinolytic agent. It competitively binds to the lysine-binding sites on plasminogen, thereby preventing its activation to plasmin and subsequent degradation of fibrin clots.

Question 10482

Topic: Biomechanics & Biomaterials

In total joint arthroplasty, the use of modular components (such as a titanium stem with a cobalt-chromium head) can lead to a specific type of electrochemical degradation at the modular junction. What type of corrosion is driven by the contact of two dissimilar metals in an electrolytic solution (synovial fluid)?

. Fretting corrosion
. Crevice corrosion
. Galvanic corrosion
. Pitting corrosion
. Intergranular corrosion

Correct Answer & Explanation

. Galvanic corrosion

Explanation

Galvanic corrosion occurs when two dissimilar metals with different electrochemical potentials (e.g., Titanium and Cobalt-Chromium) are placed in contact within a conductive solution (such as human extracellular fluid). The less noble metal acts as an anode and undergoes accelerated corrosion. Fretting corrosion is mechanically mediated due to micromotion between components.

Question 10483

Topic: Infection, Pharmacology & VTE

A 55-year-old male with chronic osteomyelitis of the tibia develops SIRS criteria. Blood cultures are pending. What is the most critical initial step in his management, specifically related to the orthopedic source?

. Start broad-spectrum antibiotics immediately after cultures are drawn
. Perform a CT scan to identify abscess formation
. Prepare for surgical debridement and removal of infected hardware if present
. Initiate aggressive fluid resuscitation to optimize hemodynamics
. Consult infectious disease for antibiotic guidance

Correct Answer & Explanation

. Prepare for surgical debridement and removal of infected hardware if present

Explanation

While all options are important, source control is paramount in the management of sepsis originating from an orthopedic infection like osteomyelitis, especially when there's an infected hardware or devitalized tissue. Delay in source control is associated with increased mortality. Therefore, preparing for surgical debridement and removal of infected hardware is the most critical initial orthopedic step, often performed concurrently with resuscitation and antibiotic initiation. Antibiotics are crucial but often ineffective without source control in established osteomyelitis. Imaging helps but surgery is the definitive step. Resuscitation and ID consult are part of general sepsis management.

Question 10484

Topic: 1. General Principles & Basic Science

An 80-year-old woman with a chronic hip prosthesis infection presents with lethargy, hypothermia (35.5°C), and a blood pressure of 85/40 mmHg. Her family reports she has been increasingly confused. Which of the following clinical features is particularly concerning for occult sepsis in the elderly?

. Tachycardia >90 bpm
. Hyperthermia >38°C
. Elevated white blood cell count
. Mental status changes and hypothermia
. Localized pain at the prosthetic site

Correct Answer & Explanation

. Mental status changes and hypothermia

Explanation

Elderly patients often present with atypical signs of infection and sepsis. While tachycardia, hyperthermia, and elevated WBC are classic SIRS criteria, elderly patients may manifest hypothermia rather than fever, and mental status changes (delirium, confusion, lethargy) are frequently the earliest and sometimes only signs of systemic infection. Tachycardia and hyperthermia may be blunted. Localized pain is important for identifying the source but not for the systemic septic presentation itself.

Question 10485

Topic: 1. General Principles & Basic Science

What is the primary goal of administering vasopressors (e.g., norepinephrine) in patients with septic shock?

. To improve cardiac contractility
. To decrease systemic vascular resistance
. To achieve a mean arterial pressure (MAP) of at least 65 mmHg
. To reduce heart rate and myocardial oxygen demand
. To increase urine output directly

Correct Answer & Explanation

. To achieve a mean arterial pressure (MAP) of at least 65 mmHg

Explanation

The primary goal of vasopressor therapy in septic shock is to restore and maintain adequate mean arterial pressure (MAP) to ensure sufficient organ perfusion. Current guidelines recommend targeting a MAP of at least 65 mmHg. While vasopressors can have some effects on cardiac contractility or heart rate depending on the agent, their main role in septic shock is to increase systemic vascular resistance to combat the distributive shock characterized by vasodilation. Urine output improves indirectly as renal perfusion is restored.

Question 10486

Topic: Infection, Pharmacology & VTE

A 62-year-old male develops septic arthritis of his knee following an arthroscopic procedure. He is hypotensive and tachycardic. Blood cultures are positive for methicillin-resistant Staphylococcus aureus (MRSA). Which antibiotic regimen would be most appropriate for empiric coverage of MRSA in severe sepsis, pending sensitivities?

. Ceftriaxone
. Piperacillin-tazobactam
. Vancomycin
. Ciprofloxacin
. Ampicillin-sulbactam

Correct Answer & Explanation

. Vancomycin

Explanation

Vancomycin is the drug of choice for empiric coverage of MRSA in severe infections, including septic arthritis leading to sepsis. The other options either lack MRSA coverage (Ceftriaxone, Piperacillin-tazobactam, Ciprofloxacin, Ampicillin-sulbactam) or are not the primary choice for confirmed or highly suspected MRSA.

Question 10487

Topic: 1. General Principles & Basic Science

Which of the following statements about Disseminated Intravascular Coagulation (DIC) in the context of severe sepsis is true?

. DIC in sepsis primarily involves excessive bleeding due to platelet dysfunction.
. DIC is characterized by systemic activation of coagulation leading to microvascular thrombosis and consumption of clotting factors.
. Patients with DIC invariably present with significant external hemorrhage.
. Treatment for sepsis-induced DIC primarily involves aggressive anticoagulation.
. Elevated fibrinogen levels are a hallmark of DIC.

Correct Answer & Explanation

. DIC is characterized by systemic activation of coagulation leading to microvascular thrombosis and consumption of clotting factors.

Explanation

Sepsis-induced DIC is a life-threatening complication characterized by widespread activation of the coagulation system, leading to the formation of microvascular thrombi. This consumes clotting factors and platelets, ultimately resulting in both thrombotic manifestations (organ dysfunction due to microthrombi) and bleeding complications (due to consumption coagulopathy). Elevated fibrinogen is typically an acute phase reactant, but in DIC, fibrinogen levels oftendecreaseas it's consumed. Aggressive anticoagulation is generally not the primary treatment, and therapy focuses on treating the underlying sepsis and supportive measures.

Question 10488

Topic: Physiology & Rehabilitation

A 35-year-old male with a severe crush injury to his lower extremity develops rhabdomyolysis and subsequent acute kidney injury (AKI). He then becomes febrile, tachycardic, and hypotensive. Which of the following is the most likely initial trigger for his systemic inflammatory response syndrome (SIRS) that could progress to sepsis?

. Direct bacterial infection of the muscle tissue
. Endogenous release of damage-associated molecular patterns (DAMPs) from necrotic muscle
. Fluid overload causing pulmonary edema
. Hyperkalemia from muscle breakdown
. Exogenous endotoxin contamination from the trauma scene

Correct Answer & Explanation

. Endogenous release of damage-associated molecular patterns (DAMPs) from necrotic muscle

Explanation

In severe trauma, particularly crush injuries leading to rhabdomyolysis, the massive necrosis of muscle cells releases intracellular components, known as damage-associated molecular patterns (DAMPs), into the circulation. These DAMPs (e.g., HMGB1, ATP, uric acid) activate innate immune cells, triggering a sterile systemic inflammatory response (SIRS) that can mimic or contribute to sepsis, even without an overt bacterial infection. While direct infection (option A) is possible, the 'sterile inflammation' from DAMPs is a key early trigger in severe trauma. The other options are either complications (fluid overload, hyperkalemia) or less common initial triggers.

Question 10489

Topic: 1. General Principles & Basic Science

Which of the following laboratory findings is most suggestive of severe sepsis with significant end-organ dysfunction?

. WBC count of 15,000/µL
. Serum creatinine of 0.9 mg/dL
. Platelet count of 180,000/µL
. Bilirubin of 4.2 mg/dL with INR of 1.8
. Glucose of 120 mg/dL

Correct Answer & Explanation

. Bilirubin of 4.2 mg/dL with INR of 1.8

Explanation

Elevated bilirubin (hyperbilirubinemia) and prolonged INR (International Normalized Ratio), indicating impaired liver synthetic function, are clear markers of liver dysfunction, which is a common and serious manifestation of end-organ damage in severe sepsis. The other options (WBC, creatinine, platelets, glucose) are either within normal limits or only suggest SIRS/inflammation without indicating significant organ dysfunction.

Question 10490

Topic: 1. General Principles & Basic Science

In an orthopedic patient experiencing septic shock, what is the recommended target central venous pressure (CVP) after initial fluid resuscitation, particularly if spontaneous ventilation is present?

. 2-6 mmHg
. 6-8 mmHg
. 8-12 mmHg
. 12-15 mmHg
. 15-18 mmHg

Correct Answer & Explanation

. 8-12 mmHg

Explanation

The Surviving Sepsis Campaign guidelines recommend targeting a CVP of 8-12 mmHg in spontaneously breathing patients after initial fluid resuscitation to optimize preload and cardiac output. In mechanically ventilated patients, the target is slightly higher (12-15 mmHg) due to the effects of positive pressure ventilation on intrathoracic pressure. Options A and B are too low, and options D and E are potentially too high, risking fluid overload and complications without further benefit.

Question 10491

Topic: Infection, Pharmacology & VTE

What is the leading cause of mortality in patients with severe sepsis and septic shock, particularly in those with orthopedic origins?

. Cardiac arrhythmias
. Uncontrolled bleeding
. Multiple Organ Dysfunction Syndrome (MODS)
. Anaphylaxis to antibiotics
. Deep vein thrombosis (DVT) with pulmonary embolism (PE)

Correct Answer & Explanation

. Multiple Organ Dysfunction Syndrome (MODS)

Explanation

Multiple Organ Dysfunction Syndrome (MODS) is the leading cause of mortality in patients with severe sepsis and septic shock. Sepsis is characterized by a dysregulated host response to infection, leading to widespread inflammation, microvascular dysfunction, and subsequent failure of two or more organ systems (e.g., respiratory, renal, cardiovascular, hepatic, neurologic, hematologic). While other complications can occur, MODS is the ultimate pathway to death in the majority of these cases.

Question 10492

Topic: Infection, Pharmacology & VTE

Which component of the systemic inflammatory response in sepsis is responsible for the widespread vasodilation and increased vascular permeability leading to distributive shock?

. Increased erythrocyte production
. Overproduction of anti-inflammatory cytokines (e.g., IL-10)
. Release of nitric oxide (NO) and other vasodilatory mediators from activated endothelial cells
. Decreased systemic vascular resistance due to direct bacterial cytotoxicity
. Increased cardiac output leading to relative hypovolemia

Correct Answer & Explanation

. Release of nitric oxide (NO) and other vasodilatory mediators from activated endothelial cells

Explanation

The widespread vasodilation and increased vascular permeability characteristic of distributive shock in sepsis are primarily mediated by the release of potent vasodilatory substances. Nitric oxide (NO), prostaglandins, and other inflammatory mediators (like bradykinin, histamine, C3a, C5a) released from activated endothelial cells, macrophages, and other immune cells play a central role. This leads to a profound drop in systemic vascular resistance and leakage of fluid from the intravascular space, contributing to hypoperfusion.

Question 10493

Topic: 1. General Principles & Basic Science

A 40-year-old male with a severely infected prosthetic joint develops sepsis. Blood cultures are positive for a multidrug-resistant organism. When considering the 'sepsis bundle,' which intervention, if delayed beyond the first hour, has the most significant impact on patient mortality?

. Administration of broad-spectrum antibiotics
. Measurement of lactate level
. Initiation of fluid resuscitation
. Application of vasopressors for hypotension
. Source control (e.g., surgical removal of prosthetic joint)

Correct Answer & Explanation

. Administration of broad-spectrum antibiotics

Explanation

While all listed interventions are crucial components of the sepsis bundle, numerous studies have consistently shown that the timely administration of appropriate broad-spectrum antibiotics within the first hour of recognition of septic shock (or even severe sepsis) is the single most important intervention impacting mortality. Delays significantly increase mortality rates. While source control is paramount, it often takes more than an hour to execute surgically, but prompt antibiotics are initiated while surgical planning occurs. Lactate measurement, fluid resuscitation, and vasopressors are also time-sensitive but antibiotic administration is often highlighted as the most critical 'hour-1' intervention.

Question 10494

Topic: 1. General Principles & Basic Science

In the context of diagnosing sepsis in an orthopedic patient, which finding, in conjunction with suspected infection, would automatically qualify a patient as having sepsis according to the Sepsis-3 definition?

. Two or more SIRS criteria
. A new or increased requirement for oxygen supplementation
. A SOFA score increase of 2 points or more from baseline
. Elevated white blood cell count
. Positive blood cultures

Correct Answer & Explanation

. A SOFA score increase of 2 points or more from baseline

Explanation

The Sepsis-3 definition (2016) redefined sepsis as 'life-threatening organ dysfunction caused by a dysregulated host response to infection.' Clinically, this is operationalized by an increase of 2 points or more in the SOFA (Sequential Organ Failure Assessment) score from baseline, in the presence of suspected or confirmed infection. SIRS criteria are no longer central to the definition of sepsis itself but can be useful as screening tools. A new or increased oxygen requirement or elevated WBC count are signs of organ dysfunction or inflammation, but the SOFA score quantifies this across multiple systems for the definition. Positive blood cultures confirm infection but don't define the 'dysregulated host response' or organ dysfunction.

Question 10495

Topic: 1. General Principles & Basic Science

Which of the following agents is the first-line vasopressor recommended for patients with septic shock who remain hypotensive despite adequate fluid resuscitation?

. Dopamine
. Vasopressin
. Epinephrine
. Norepinephrine
. Phenylephrine

Correct Answer & Explanation

. Norepinephrine

Explanation

Norepinephrine (Levophed) is consistently recommended as the first-line vasopressor for septic shock in current guidelines (Surviving Sepsis Campaign). It primarily acts as an alpha-agonist, causing vasoconstriction and increasing systemic vascular resistance, with some beta-1 agonism for cardiac support. Dopamine is associated with more arrhythmias and is generally not preferred. Vasopressin can be added as a second agent. Epinephrine is often considered second-line or in specific circumstances. Phenylephrine is a pure alpha-agonist and can be used but is not typically first-line.

Question 10496

Topic: 1. General Principles & Basic Science

Which of the following is an expected metabolic derangement in severe sepsis due to tissue hypoperfusion and mitochondrial dysfunction?

. Metabolic alkalosis
. Hyperglycemia followed by hypoglycemia
. Hypernatremia
. Lactic acidosis
. Hypocalcemia

Correct Answer & Explanation

. Lactic acidosis

Explanation

Lactic acidosis is a hallmark of tissue hypoperfusion and impaired cellular oxygen utilization in severe sepsis and septic shock. The shift from aerobic to anaerobic metabolism, along with mitochondrial dysfunction, leads to increased lactate production. While other metabolic derangements can occur, lactic acidosis is the most direct and diagnostically significant indicator of anaerobic metabolism and poor perfusion in sepsis.

Question 10497

Topic: 1. General Principles & Basic Science

In an orthopedic patient with severe sepsis, which of the following scenarios would prompt consideration for administering corticosteroids (e.g., hydrocortisone)?

. Any patient with a SOFA score >2
. Patients with refractory septic shock despite adequate fluids and high-dose vasopressors
. All patients with confirmed gram-negative bacteremia
. Patients with a history of chronic steroid use before developing sepsis
. As a primary treatment to reduce inflammation in all sepsis cases

Correct Answer & Explanation

. Patients with refractory septic shock despite adequate fluids and high-dose vasopressors

Explanation

Corticosteroids (specifically hydrocortisone) are recommended for adult patients with septic shock who remain hypotensive despite adequate fluid resuscitation and requiring vasopressors, particularly if high-dose vasopressors are needed. This is based on evidence suggesting it can reduce vasopressor requirements and potentially improve outcomes in this specific subgroup, likely by addressing adrenal insufficiency. It is not recommended for all sepsis patients or those with only elevated SOFA scores, or as a primary anti-inflammatory treatment in general sepsis.

Question 10498

Topic: 1. General Principles & Basic Science

When should intravenous albumin be considered in the fluid resuscitation of a patient with septic shock?

. As the sole resuscitation fluid from the outset.
. Only if the serum albumin level is below 2.0 g/dL.
. When patients require substantial amounts of crystalloids for resuscitation.
. To prevent stress ulcers in all critically ill patients.
. Never, as it has no proven benefit in septic shock.

Correct Answer & Explanation

. When patients require substantial amounts of crystalloids for resuscitation.

Explanation

The Surviving Sepsis Campaign guidelines suggest using albumin in addition to crystalloids when patients require substantial amounts of crystalloids for resuscitation, especially if patients are still hypovolemic or hypotensive despite initial crystalloid boluses. It is not typically used as the sole resuscitation fluid initially, nor is its use strictly tied to a specific low serum albumin level (though hypoalbuminemia is common in sepsis). It does not prevent stress ulcers. Some studies show a benefit in reducing the amount of crystalloid needed and potentially improving outcomes, but it's not a first-line agent.

Question 10499

Topic: 1. General Principles & Basic Science
Which of the following interventions is part of the 'early goal-directed therapy' (EGDT) strategy for sepsis, as initially described by Rivers et al.?
. Maintaining a central venous oxygen saturation (ScvO2) ≥70%
. Administering a continuous insulin infusion to achieve strict glucose control (80-110 mg/dL)
. Routine use of activated protein C for all severe sepsis patients
. Transfusion of packed red blood cells to achieve a hemoglobin target of 10-12 g/dL
. Placement of a pulmonary artery catheter in all patients

Correct Answer & Explanation

. Maintaining a central venous oxygen saturation (ScvO2) ≥70%

Explanation

Early goal-directed therapy (EGDT), as originally described by Rivers et al., focused on optimizing preload, afterload, and contractility to achieve specific physiological targets within the first 6 hours. One of the key targets was maintaining a central venous oxygen saturation (ScvO2) of ≥70% (or mixed venous oxygen saturation, SvO2, ≥65%). While strict glucose control and activated protein C were once considered, they are no longer routinely recommended. Hemoglobin target is generally lower (7-9 g/dL), and pulmonary artery catheters are not routinely used.

Question 10500

Topic: 1. General Principles & Basic Science
A patient with a traumatic amputated limb develops severe sepsis. Which of the following is an example of an appropriate 'source control' measure in this context?
. Administering high-dose vasopressors
. Irrigation and debridement of the stump, possibly with re-amputation or definitive closure
. Initiating continuous veno-venous hemodiafiltration (CVVHDF)
. Performing a bronchoscopy to rule out pneumonia
. Starting empirical antifungal therapy

Correct Answer & Explanation

. Irrigation and debridement of the stump, possibly with re-amputation or definitive closure

Explanation

Source control refers to measures to eliminate the source of infection. In a patient with severe sepsis from an infected traumatic amputated limb, this would involve surgical intervention such as irrigation and debridement of infected or necrotic tissue in the stump, potentially further amputation to healthy tissue, or definitive closure. The other options are supportive measures (vasopressors, CVVHDF), diagnostic procedures (bronchoscopy), or specific antimicrobial therapies (antifungals) but not source control itself for a surgical infection.

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