Bone and joint infections US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Bone and joint infections. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Bone and joint infections US Medical PG Question 1: A 42-year-old man with a history of gout and hypertension presents to his family physician with a complaint of increased left knee pain over the past 2 days. He also reports swelling and redness of the left knee and is unable to bear weight on that side. He denies any prior surgery or inciting trauma to the knee. His temperature is 97.0°F (36.1°C), blood pressure is 137/98 mm Hg, pulse is 80/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical examination reveals a left knee that is erythematous, swollen, warm-to-touch, and extremely tender to palpation and with attempted flexion/extension movement. His left knee range of motion is markedly reduced compared to the contralateral side. Joint aspiration of the left knee is performed with synovial fluid analysis showing turbid fluid with a leukocyte count of 95,000/mm^3, 88% neutrophils, and a low glucose. Gram stain of the synovial fluid is negative. Results from synovial fluid culture are pending. Which of the following is the best treatment regimen for this patient?
- A. Ceftriaxone
- B. Piperacillin-tazobactam
- C. Vancomycin and ceftazidime (Correct Answer)
- D. Indomethacin and colchicine
- E. Acetaminophen and ibuprofen
Bone and joint infections Explanation: ***Vancomycin and ceftazidime***
- The patient presents with **acute monoarticular arthritis** with signs of **septic arthritis**, including a highly inflammatory synovial fluid (95,000 WBCs/mm^3, 88% neutrophils, low glucose) and inability to bear weight [1].
- **Empiric broad-spectrum antibiotic coverage** is crucial before culture results, typically involving an agent effective against **Gram-positive bacteria** (e.g., vancomycin for MRSA) and an agent against **Gram-negative bacteria** (e.g., ceftazidime for *Pseudomonas* or other resistant gram-negatives), especially in patients with comorbidities like gout [1].
*Ceftriaxone*
- Ceftriaxone is a **third-generation cephalosporin** that provides good coverage for many Gram-negative bacteria and some Gram-positive bacteria.
- However, it **does not cover *Pseudomonas aeruginosa* or methicillin-resistant *Staphylococcus aureus* (MRSA)**, which are important pathogens to consider in septic arthritis, especially without a definitive causative organism.
*Piperacillin-tazobactam*
- Piperacillin-tazobactam is a **broad-spectrum antibiotic** with good coverage for Gram-positive, Gram-negative (including *Pseudomonas*), and anaerobic bacteria.
- While it offers good broad coverage, it also **does not reliably cover MRSA**, which is a significant concern in empirical treatment of septic arthritis given its prevalence.
*Indomethacin and colchicine*
- This regimen is specific for the treatment of **acute gout flares** by reducing inflammation.
- While the patient has a history of gout, the **highly elevated leukocyte count** with a predominance of neutrophils and low glucose in the synovial fluid strongly indicate **septic arthritis**, which is a medical emergency requiring antibiotic treatment [1].
*Acetaminophen and ibuprofen*
- These medications provide **analgesia and anti-inflammatory effects** for pain relief.
- They are **insufficient as primary treatment** for septic arthritis, which necessitates urgent antimicrobial therapy to prevent joint destruction and systemic complications.
Bone and joint infections US Medical PG Question 2: A 3-year-old patient is brought to the emergency department by her mother due to inability to walk. The child has been limping recently and as of this morning, has refused to walk. Any attempts to make the child walk or bear weight result in crying. She was recently treated for impetigo and currently takes a vitamin D supplement. Physical exam is remarkable for an anxious appearing toddler with knee swelling, erythema, and limited range of motion due to pain. Her mother denies any recent trauma to the child's affected knee. Temperature is 103°F (39.4°C), pulse is 132/min, blood pressure is 90/50 mmHg, respirations are 18/min, and oxygen saturation is 99% on room air. Which of the following is the best initial step in management?
- A. MRI
- B. Ultrasound
- C. Synovial fluid analysis (Correct Answer)
- D. Broad spectrum antibiotics
- E. Radiograph
Bone and joint infections Explanation: ***Synovial fluid analysis***
- The patient's presentation with **fever**, **joint pain**, inability to bear weight, and **swelling/erythema** of the knee is highly suggestive of **septic arthritis**.
- **Arthrocentesis** and subsequent **synovial fluid analysis** (cell count with differential, Gram stain, culture) is the definitive diagnostic test to confirm septic arthritis and identify the causative organism.
*MRI*
- While MRI can visualize soft tissue and bone, it is generally reserved for cases where the diagnosis is unclear or to evaluate for complications such as **osteomyelitis** or abscess formation, after initial diagnostic steps.
- It is not the **initial diagnostic step** for suspected septic arthritis, which requires prompt identification of the pathogen to guide antibiotic therapy.
*Ultrasound*
- **Ultrasound** can identify joint effusion, but it cannot differentiate between septic arthritis and other causes of joint effusion.
- It may be used to guide arthrocentesis if the effusion is difficult to aspirate.
*Broad spectrum antibiotics*
- Although **broad-spectrum antibiotics** are indicated for **presumed septic arthritis**, they should be administered *after* obtaining fluid for culture.
- Starting antibiotics before collecting cultures can lead to **false-negative culture results**, hindering identification of the causative organism and appropriate antibiotic selection.
*Radiograph*
- **Radiographs** can rule out fracture or dislocation and may show signs of soft tissue swelling or effusion, but they are not sensitive enough to diagnose early septic arthritis.
- They also cannot differentiate septic arthritis from other inflammatory arthropathies or sterile effusions.
Bone and joint infections US Medical PG Question 3: A 33-year-old man with a history of IV drug and alcohol abuse presents to the emergency department with back pain. He states that his symptoms started 3 days ago and have been gradually worsening. His temperature is 102°F (38.9°C), blood pressure is 127/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for tenderness over the mid thoracic spine. Laboratory values are only notable for a leukocytosis and an elevated ESR and CRP. Which of the following is the most likely diagnosis?
- A. Degenerative spine disease
- B. Herniated nucleus pulposus
- C. Musculoskeletal strain
- D. Osteomyelitis (Correct Answer)
- E. Spinal epidural hematoma
Bone and joint infections Explanation: ***Osteomyelitis***
- The patient's history of **IV drug abuse** is a major risk factor for **hematogenous osteomyelitis**, especially vertebral osteomyelitis.
- The presence of **fever**, **localized spinal tenderness**, **leukocytosis**, and elevated **ESR** and **CRP** are classic signs of infection.
*Degenerative spine disease*
- This condition typically presents with **chronic pain** and insidious onset, not acute fever and inflammatory markers.
- While it can cause back pain, it is not associated with systemic signs of infection or a rapid worsening course like in this case.
*Herniated nucleus pulposus*
- Primarily causes **radicular pain** and neurological deficits due to nerve compression, often without systemic symptoms.
- There are no signs of infection, fever, or elevated inflammatory markers associated with a simple herniated disc.
*Musculoskeletal strain*
- This would present with localized pain, but rarely with **fever**, **leukocytosis**, and markedly elevated inflammatory markers.
- It is typically a self-limiting condition with symptoms that would not progressively worsen over three days with systemic signs of infection.
*Spinal epidural hematoma*
- This is characterized by sudden, severe back pain and often rapid onset neurological deficits, particularly in patients on anticoagulants or with coagulopathies.
- It would not typically present with **fever** and elevated inflammatory markers suggestive of an infection.
Bone and joint infections US Medical PG Question 4: A 62-year-old man comes to the physician because of increasing pain in his right leg for 2 months. The pain persists throughout the day and is not relieved by rest. He tried taking acetaminophen, but it provided no relief from his symptoms. There is no family history of serious illness. He does not smoke. He occasionally drinks a beer. Vital signs are within normal limits. On examination, the right tibia is bowing anteriorly; range of motion is limited by pain. An x-ray of the right leg shows a deformed tibia with multiple lesions of increased and decreased density and a thickened cortical bone. Laboratory studies show markedly elevated serum alkaline phosphatase and normal calcium and phosphate levels. This patient is most likely to develop which of the following complications?
- A. Osteosarcoma
- B. Renal insufficiency
- C. Impaired hearing
- D. Pancytopenia
- E. High-output cardiac failure (Correct Answer)
Bone and joint infections Explanation: ***High-output cardiac failure***
- The patient's presentation with **bone pain**, **tibia bowing**, mixed **lytic and blastic lesions** on X-ray, and markedly **elevated alkaline phosphatase** with normal calcium and phosphate is classic for **Paget's disease of bone**.
- **Paget's disease** involves increased bone turnover, leading to highly vascularized bone. This increased vascularity can create **arteriovenous shunts**, expanding the vascular bed and increasing cardiac output, eventually leading to **high-output cardiac failure**.
- While this complication is **rare** (<3% of cases) and typically occurs only in **extensive polyostotic disease** (>35% skeletal involvement), it is the **most characteristic cardiovascular complication** and represents the direct pathophysiologic consequence of increased bone vascularity.
*Osteosarcoma*
- While **osteosarcoma** is a serious complication of Paget's disease occurring in approximately **1% of cases**, it is also relatively rare.
- Among the listed options, high-output cardiac failure represents the more **direct vascular consequence** of Paget's disease pathophysiology, making it the intended answer for this question about disease mechanisms.
*Renal insufficiency*
- **Hypercalcemia** can lead to nephrocalcinosis and renal insufficiency, but this patient has **normal calcium levels**, making renal insufficiency due to calcium abnormalities unlikely.
- Immobilized Paget's patients can develop hypercalcemia and renal issues, but this is not typical in ambulatory patients.
*Impaired hearing*
- **Impaired hearing** can occur in Paget's disease when the **skull is affected** (in 30-50% of skull cases), leading to **compression of cranial nerve VIII** or ossicular involvement.
- However, this patient's presentation involves **long bone disease** (tibia), and the question focuses on systemic complications of increased bone vascularity rather than localized cranial involvement.
*Pancytopenia*
- **Pancytopenia** is not a typical complication of Paget's disease.
- While severe widespread disease can rarely lead to bone marrow compromise, this is not a recognized primary complication and would not be the most likely outcome.
Bone and joint infections US Medical PG Question 5: A 6-year-old girl is brought to the physician for intermittent fevers and painful swelling of the left ankle for 2 weeks. She has no history of trauma to the ankle. She has a history of sickle cell disease. Current medications include hydroxyurea and acetaminophen for pain. Her temperature is 38.4°C (101.2°F) and pulse is 112/min. Examination shows a tender, swollen, and erythematous left ankle with point tenderness over the medial malleolus. A bone biopsy culture confirms the diagnosis. Which of the following is the most likely causal organism?
- A. Coccidioides immitis
- B. Pseudomonas aeruginosa
- C. Escherichia coli
- D. Streptococcus pneumoniae
- E. Salmonella enterica (Correct Answer)
Bone and joint infections Explanation: ***Salmonella enterica***
- Patients with **sickle cell disease** are particularly susceptible to **osteomyelitis** caused by *Salmonella* species due to impaired splenic function and increased gut permeability.
- The presentation of **fever**, **painful swelling**, and **point tenderness over a bone** in a patient with a history of sickle cell disease strongly points towards *Salmonella* osteomyelitis.
*Coccidioides immitis*
- This fungus is a cause of **coccidioidomycosis**, common in **southwestern US desert regions**, but osteomyelitis is a less common manifestation and typically affects immunocompromised individuals more severely.
- While it can cause osteomyelitis, it is not the most likely organism in a child with sickle cell disease presenting with acute osteomyelitis.
*Pseudomonas aeruginosa*
- **Pseudomonas osteomyelitis** is more commonly associated with puncture wounds (e.g., foot puncture through a shoe), intravenous drug use, or nosocomial infections.
- While it can occur, it is less common as a primary cause of osteomyelitis in a child with sickle cell disease without these specific risk factors.
*Escherichia coli*
- *E. coli* can cause osteomyelitis, often in cases of **urinary tract infections** or **intra-abdominal infections** that spread hematogenously, or in settings of open fractures or surgical contamination.
- It is not as classically associated with sickle cell disease-related osteomyelitis as *Salmonella*.
*Streptococcus pneumoniae*
- *S. pneumoniae* can cause osteomyelitis, especially in **young children** and individuals with **impaired immunity**, but it is generally less common than *Staphylococcus aureus* or *Salmonella* in sickle cell patients.
- While sickle cell patients are prone to **pneumococcal infections**, *Salmonella* is a more specific and well-known cause of osteomyelitis in this population.
Bone and joint infections US Medical PG Question 6: A 56-year-old woman comes to the emergency department because of worsening pain and swelling in her right knee for 3 days. She underwent a total knee arthroplasty of her right knee joint 5 months ago. The procedure and immediate aftermath were uneventful. She has hypertension and osteoarthritis. Current medications include glucosamine, amlodipine, and meloxicam. Her temperature is 37.9°C (100.2°F), pulse is 95/min, and blood pressure is 115/70 mm Hg. Examination shows a tender, swollen right knee joint; range of motion is limited by pain. The remainder of the examination shows no abnormalities. Arthrocentesis of the right knee is performed. Analysis of the synovial fluid shows:
Appearance Cloudy
Viscosity Absent
WBC count 78,000/mm3
Segmented neutrophils 94%
Lymphocytes 6%
Synovial fluid is sent for culture and antibiotic sensitivity. Which of the following is the most likely causal pathogen?
- A. Staphylococcus aureus
- B. Escherichia coli
- C. Pseudomonas aeruginosa
- D. Staphylococcus epidermidis (Correct Answer)
- E. Streptococcus agalactiae
Bone and joint infections Explanation: ***Staphylococcus epidermidis***
- This patient's symptoms (worsening pain and swelling in a knee with a history of **total knee arthroplasty 5 months ago**, increased WBC count and neutrophil predominance in synovial fluid), point towards a **prosthetic joint infection**.
- **Coagulase-negative Staphylococci**, particularly *S. epidermidis*, are the most common cause of **late prosthetic joint infections**, typically occurring months to years after surgery.
*Staphylococcus aureus*
- *Staphylococcus aureus* is a common cause of **acute prosthetic joint infections**, which usually manifest within the **first 3 months post-surgery**. This patient's symptoms began 5 months after surgery.
- While it can cause late infections, *S. epidermidis* is more characteristic for this timeline in prosthetic joint infections.
*Escherichia coli*
- *Escherichia coli* is typically associated with **urinary tract infections** or **gastrointestinal infections**.
- It is an uncommon cause of prosthetic joint infections unless there's a direct spread from a local infection or systemic sepsis, which is not suggested here.
*Pseudomonas aeruginosa*
- *Pseudomonas aeruginosa* is often associated with **healthcare-associated infections**, particularly in immunocompromised patients or those with indwelling catheters or extensive burns.
- While it can cause prosthetic joint infections, it's less common than Staphylococci and usually linked to specific clinical settings or water contamination.
*Streptococcus agalactiae*
- *Streptococcus agalactiae* (Group B Strep) is primarily known to cause serious infections in **neonates** and **pregnant women**, and in adults with underlying conditions like **diabetes** or **immunocompromise**.
- It is an infrequent cause of prosthetic joint infections in otherwise healthy adults without specific risk factors for GBS infection.
Bone and joint infections US Medical PG Question 7: A 60-year-old woman presents to the physician with a 2-day history of fever and painful swelling of the left knee. She was diagnosed with rheumatoid arthritis about 15 years ago and has a 7-year history of diabetes mellitus. Over the past year, she has been admitted to the hospital twice for acute, painful swelling of the knees and hands. She is on insulin therapy and takes methotrexate, metformin, aspirin, and prednisolone 5 mg/day. Her temperature is 38.5°C (101.3°F), pulse is 86/min, respirations are 14/min, and blood pressure is 125/70 mm Hg. A finger-stick glucose test shows 230 mg/dL. Her left knee is diffusely swollen, warm, and painful on both active and passive motion. There is evidence of deformity in several small joints of the hands and feet without any acute swelling or pain. Physical examination of the lungs, abdomen, and perineum shows no abnormalities. The synovial fluid analysis shows the following:
Color turbid, purulent, gray
Viscosity reduced
WBC 25,000/µL–250,000/µL
Neutrophils > 90%
Crystals may be present (presence indicates coexistence, but does not rule out infection)
Which of the following is the most appropriate initial pharmacotherapy in this patient?
- A. Intra-articular triamcinolone acetonide
- B. Intravenous methylprednisolone
- C. Intra-articular ceftriaxone
- D. Oral ciprofloxacin
- E. Intravenous vancomycin (Correct Answer)
Bone and joint infections Explanation: ***Intravenous vancomycin***
- The patient's presentation with **fever**, a **swollen, warm, and painful knee**, and **turbid, purulent synovial fluid** with a high white blood cell count (25,000–250,000/µL) and >90% neutrophils is highly suggestive of **septic arthritis**.
- Given her history of **rheumatoid arthritis** (which can predispose to joint infections) and **diabetes mellitus** (increasing infection risk), empirical intravenous antibiotics covering **gram-positive organisms** like *Staphylococcus aureus* (a common cause of septic arthritis) are crucial. **Vancomycin** is an appropriate choice for initial broad-spectrum coverage, especially if **MRSA** is a concern.
*Intra-articular triamcinolone acetonide*
- This is an **anti-inflammatory corticosteroid** used to manage chronic joint inflammation in conditions like rheumatoid arthritis or osteoarthritis.
- It is **contraindicated** in suspected or confirmed septic arthritis because it can suppress the local immune response and potentially worsen the infection.
*Intravenous methylprednisolone*
- This is a **systemic corticosteroid** used for acute inflammatory conditions, including flares of rheumatoid arthritis.
- While it has anti-inflammatory effects, it does **not treat infection** and can globally **immunosuppress** the patient, making the existing septic arthritis potentially more severe.
*Intra-articular ceftriaxone*
- **Ceftriaxone is an antibiotic**, but administering it directly into the joint (**intra-articular**) is **not the standard or recommended route** for treating septic arthritis.
- Systemic intravenous administration is necessary to achieve adequate antibiotic concentrations throughout the joint and combat potential bacteremia.
*Oral ciprofloxacin*
- **Ciprofloxacin is an antibiotic**, but **oral administration** may not achieve sufficient drug levels in the joint quickly enough for acute septic arthritis, especially in a patient with a severe presentation.
- While it covers some gram-negative organisms, initial empirical therapy for septic arthritis often prioritizes coverage for gram-positive bacteria like *Staphylococcus aureus* before culture results are available.
Bone and joint infections US Medical PG Question 8: A 37-year-old man presents to the emergency department after he cut his hand while working on his car. The patient has a past medical history of antisocial personality disorder and has been incarcerated multiple times. His vitals are within normal limits. Physical exam is notable for a man covered in tattoos with many bruises over his face and torso. Inspection of the patient's right hand reveals 2 deep lacerations on the dorsal aspects of the second and third metacarpophalangeal (MCP) joints. The patient is given a tetanus vaccination, and the wound is irrigated. Which of the following is appropriate management for this patient?
- A. Closure of the wound with sutures
- B. Clindamycin and topical erythromycin
- C. Ciprofloxacin and topical erythromycin
- D. Surgical irrigation, debridement, and amoxicillin-clavulanic acid (Correct Answer)
- E. No further management necessary
Bone and joint infections Explanation: ***Surgical irrigation, debridement, and amoxicillin-clavulanic acid***
- The presence of deep lacerations over the metacarpophalangeal joints, combined with an injury mechanism suggestive of a **fight bite** (laceration from striking another person's teeth), mandates **aggressive surgical management**.
- **Amoxicillin-clavulanic acid** is the appropriate antibiotic choice for **human bite wounds** due to its broad spectrum covering common oral flora like *Eikenella corrodens*, *Streptococci*, and anaerobes.
*Closure of the wound with sutures*
- **Primary closure** of human bite wounds, especially those on the hand, is strongly **contraindicated** due to the high risk of severe infection.
- These wounds should be left open to drain and heal by **secondary intention** following thorough debridement.
*Clindamycin and topical erythromycin*
- **Clindamycin** has good anaerobic coverage but lacks sufficient coverage for common aerobes found in human bites like *Eikenella corrodens*.
- **Topical erythromycin** is ineffective for deep soft tissue infections and does not provide systemic protection against the likely pathogens.
*Ciprofloxacin and topical erythromycin*
- **Ciprofloxacin** has limited activity against many oral anaerobes and *Eikenella corrodens*, making it a poor choice for human bite prophylaxis.
- As mentioned, **topical antibiotics** are insufficient for preventing serious infections in deep bite wounds.
*No further management necessary*
- This patient has sustained a **deep, contaminated wound** with a high risk of serious infection, potentially involving joints or tendons.
- Failing to provide further management, including surgical exploration and appropriate antibiotics, would likely lead to severe complications such as **osteomyelitis** or **septic arthritis**.
Bone and joint infections US Medical PG Question 9: Five days after undergoing right knee arthroplasty for osteoarthritis, a 68-year-old man has severe pain in his right knee preventing him from participating in physical therapy. On the third postoperative day when the dressing was changed, the surgical wound appeared to be intact, slightly swollen, and had a clear secretion. He has a history of diabetes, hyperlipidemia, and hypertension. Current medications include metformin, enalapril, and simvastatin. His temperature is 37.3°C (99.1°F), pulse is 94/min, and blood pressure is 130/88 mm Hg. His right knee is swollen, erythematous, and tender to palpation. There is pain on movement of the joint. The medial parapatellar skin incision appears superficially opened in its proximal and distal part with yellow-green discharge. There is blackening of the skin on both sides of the incision. Which of the following is the next best step in the management of this patient?
- A. Vacuum dressing
- B. Antiseptic dressing
- C. Nafcillin therapy
- D. Removal of prostheses
- E. Surgical debridement (Correct Answer)
Bone and joint infections Explanation: ***Surgical debridement***
- The patient presents with classic signs of **necrotizing fasciitis** or a severe wound infection: rapidly worsening pain, erythema, swelling, **yellow-green discharge**, and crucially, **blackening of the skin** (indicating tissue necrosis).
- Immediate **surgical debridement** is critical for source control, removal of necrotic tissue, and preventing further spread of infection, which can be life-threatening.
*Vacuum dressing*
- A vacuum-assisted closure (VAC) dressing is used for wound management after adequate debridement or for wounds without signs of aggressive infection to promote healing.
- Applying a VAC dressing to a wound with widespread necrosis and active infection, especially necrotizing fasciitis, without prior debridement would be ineffective and potentially harmful.
*Antiseptic dressing*
- While antiseptic dressings can help reduce bacterial load in some superficial wounds, they are entirely insufficient for deep-seated, rapidly spreading infections with tissue necrosis.
- This approach fails to address the underlying necrotic tissue and the extent of the infection, leading to rapid deterioration.
*Nafcillin therapy*
- **Antibiotic therapy** is essential for treating severe infections; however, it must be combined with source control, especially when necrosis is present.
- Giving antibiotics alone without **surgical debridement** in cases of necrotizing fasciitis is inadequate and will not prevent progression of the infection or improve patient outcomes.
*Removal of prostheses*
- While **prosthesis removal** may be necessary in some cases of established periprosthetic joint infection, it is a definitive and often late measure.
- The immediate priority in a rapidly progressing, necrotic wound infection is **surgical debridement** to remove devitalized tissue and control the local infection, prior to considering implant removal unless the infection is directly on the implant.
Bone and joint infections US Medical PG Question 10: A 35-year-old man arrives at the emergency department within minutes after a head-on motor vehicle accident. He suffered from blunt abdominal trauma, several lacerations to his face as well as lacerations to his upper and lower extremities. The patient is afebrile, blood pressure is 45/25 mmHg and pulse is 160/minute. A CBC is obtained and is most likely to demonstrate which of the following?
- A. Hb 17 g/dL, Hct 20%
- B. Hb 15 g/dL, Hct 45% (Correct Answer)
- C. Hb 5 g/dL, Hct 30%
- D. Hb 20 g/dL, Hct 60%
- E. Hb 5 g/dL, Hct 20%
Bone and joint infections Explanation: ***Hb 15 g/dL, Hct 45%***
- This option represents **normal hemoglobin and hematocrit values**, which are expected in the **initial minutes following acute hemorrhage**.
- In acute blood loss, **whole blood is lost** (both RBCs and plasma together), so the **concentration of RBCs remains unchanged** initially.
- **Hemodilution has not yet occurred**, as there hasn't been enough time for fluid shifts from the extravascular to the intravascular space to dilute the blood.
- This is a **critical teaching point**: early CBC values can be **falsely reassuring** and don't reflect the severity of hemorrhagic shock.
*Hb 17 g/dL, Hct 20%*
- This option shows a **medically implausible combination** - the normal Hb:Hct ratio is approximately **1:3**, so an Hb of 17 g/dL should correspond to an Hct of approximately 51%, not 20%.
- This combination cannot occur physiologically and does not represent any stage of acute blood loss.
*Hb 5 g/dL, Hct 30%*
- This shows an **incorrect Hb:Hct ratio** (6:1 instead of the expected 3:1) - if Hb is 5 g/dL, the Hct should be approximately 15%, not 30%.
- While severe anemia can occur with massive blood loss, this would only be apparent **hours after injury** once hemodilution from fluid shifts occurs, not within minutes.
- The implausible ratio makes this medically incorrect.
*Hb 20 g/dL, Hct 60%*
- These values represent **polycythemia** (abnormally high red blood cell counts), which is the opposite of what would be expected after acute traumatic blood loss.
- The Hb:Hct ratio is appropriate (1:3), but the elevated values suggest chronic hypoxemia, dehydration, or myeloproliferative disorders - not acute hemorrhage.
*Hb 5 g/dL, Hct 20%*
- This shows an **incorrect Hb:Hct ratio** (4:1 instead of the expected 3:1) - if Hb is 5 g/dL, the Hct should be approximately 15%, not 20%.
- Even if we accept these as severe anemia values, they would only be seen **several hours after injury** when sufficient time has passed for fluid shifts and hemodilution to occur, not within minutes of the trauma.
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