Anesthesia in special populations US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Anesthesia in special populations. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Anesthesia in special populations US Medical PG Question 1: A 21-year-old man undergoes orthopedic surgery for a leg fracture that he has sustained in a motorbike accident. After induction of anesthesia with desflurane, the patient's respiratory minute ventilation decreases notably. Which of the following additional effects is most likely to occur in response to this drug?
- A. Decreased seizure threshold
- B. Increased intracranial pressure (Correct Answer)
- C. Increased skeletal muscle tonus
- D. Increased cerebral metabolic rate
- E. Increased glomerular filtration rate
Anesthesia in special populations Explanation: ***Increased intracranial pressure***
- **Desflurane**, like other volatile anesthetics, causes **cerebral vasodilation**, leading to increased cerebral blood flow and consequently **increased intracranial pressure (ICP)**.
- This effect is particularly pronounced with desflurane and is a key concern, especially in patients with pre-existing elevated ICP.
*Decreased seizure threshold*
- While some anesthetics can lower the seizure threshold, **desflurane** is generally considered to be **seizure-neutral** or even anticonvulsant at higher concentrations.
- **Enflurane** is an example of an inhaled anesthetic known to reliably induce epileptiform activity.
*Increased skeletal muscle tonus*
- **Volatile anesthetics** generally cause **skeletal muscle relaxation**, which is why they are often used with neuromuscular blockers during surgery.
- An increase in skeletal muscle tonus is seen in conditions like **malignant hyperthermia**, which can be triggered by desflurane, but this is a rare, life-threatening genetic disorder, not a typical effect of the drug.
*Increased cerebral metabolic rate*
- **Desflurane** typically causes a **dose-dependent reduction in the cerebral metabolic rate for oxygen (CMRO2)**, indicating a decrease in brain activity.
- This is often beneficial during anesthesia, providing **neuroprotection**, despite the concurrent cerebral vasodilation.
*Increased glomerular filtration rate*
- **Volatile anesthetics**, including desflurane, tend to cause a **dose-dependent decrease in renal blood flow and glomerular filtration rate (GFR)** due to systemic vasodilation and decreased cardiac output.
- Renal function is generally preserved in healthy individuals, but the GFR does not increase with the use of desflurane.
Anesthesia in special populations US Medical PG Question 2: A 9-year-old boy presents for incision and drainage of a small abscess on his left thigh. No significant past medical history. No current medications. Before the procedure, the patient is allowed to inhale colorless, sweet-smelling gas. After the procedure, the patient receives 3–4 minutes of high flow oxygen through a nasal mask. The pulse oximetry shows an oxygen saturation of 94%. This patient was oxygenated at the end of the procedure to prevent which of the following complications?
- A. Malignant hyperthermia
- B. Hepatotoxicity
- C. Raised intracranial pressure
- D. Cardiac arrhythmias
- E. Diffusion hypoxia (Correct Answer)
Anesthesia in special populations Explanation: ***Diffusion hypoxia (Correct)***
- **Nitrous oxide** rapidly diffuses from the blood into the alveoli after discontinuation, displacing oxygen and carbon dioxide.
- This creates the **"Fink effect"** - a dilution of alveolar oxygen that can lead to transient **hypoxemia**.
- Administering **high-flow oxygen for 3-5 minutes** prevents this complication by maintaining adequate alveolar oxygen concentration during the N2O washout period.
*Malignant hyperthermia (Incorrect)*
- This is a pharmacogenetic disorder triggered by **volatile anesthetics** (e.g., halothane, sevoflurane) and **succinylcholine**, not nitrous oxide.
- Characterized by **muscle rigidity, hyperthermia, and hypermetabolism**.
- While oxygen is part of supportive treatment, post-procedure oxygenation doesn't prevent its onset.
- Treatment requires **dantrolene**, not just oxygen.
*Hepatotoxicity (Incorrect)*
- Not prevented by post-procedure oxygenation.
- Typically associated with **halothane** (rare with modern anesthetics), not nitrous oxide.
- Nitrous oxide is not a primary cause of hepatotoxicity.
*Raised intracranial pressure (Incorrect)*
- While nitrous oxide can increase **cerebral blood flow** and potentially raise ICP, post-procedure oxygen doesn't specifically prevent this effect.
- Management of elevated ICP involves **hyperventilation, head elevation, osmotic diuretics**, and avoiding N2O in at-risk patients.
- The oxygen administration here targets diffusion hypoxia, not ICP control.
*Cardiac arrhythmias (Incorrect)*
- While hypoxia can cause arrhythmias, the primary purpose of post-N2O oxygen is to prevent **diffusion hypoxia**.
- Preventing hypoxemia secondarily reduces arrhythmia risk, but this is not the direct indication.
- Arrhythmias from anesthetics are more commonly associated with **halogenated agents** sensitizing the myocardium to catecholamines.
Anesthesia in special populations US Medical PG Question 3: A 52-year-old obese man is brought to the emergency department 30 minutes after he was involved in a high-speed motor vehicle collision. He was the unrestrained driver. On arrival, he is lethargic. His pulse is 112/min, respirations are 10/min and irregular, and blood pressure is 94/60 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 91%. The pupils are equal and react sluggishly to light. He withdraws his extremities to pain. There are multiple bruises over his face, chest, and abdomen. Breath sounds are decreased over the left lung base. Two large bore peripheral venous catheters are inserted and 0.9% saline infusion is begun. Rapid sequence intubation is initiated and endotracheal intubation is attempted without success. Bag and mask ventilation is continued. Pulse oximetry shows an oxygen saturation of 84%. The patient has no advance directive and family members have not arrived. Which of the following is the most appropriate next step in the management of this patient?
- A. Nasotracheal intubation
- B. Video laryngoscopy
- C. Cricothyrotomy (Correct Answer)
- D. Comfort measures only
- E. Tracheostomy
Anesthesia in special populations Explanation: ***Cricothyrotomy***
- In a trauma patient with **failed endotracheal intubation** and declining oxygen saturation (from 91% to 84% despite bag-mask ventilation), an emergent cricothyrotomy is indicated for **immediate airway control**.
- This procedure provides a definitive airway in a **can't intubate/can't ventilate** scenario, preventing further hypoxia and potential brain damage.
*Nasotracheal intubation*
- **Nasotracheal intubation** is generally contraindicated in patients with suspected **facial or skull base fractures** due to the risk of intracranial intubation.
- Given the high-speed collision and facial bruises, such fractures are possible, making this a less safe option compared to cricothyrotomy.
*Video laryngoscopy*
- While **video laryngoscopy** can be helpful for difficult airways, it was already implied that intubation was attempted and failed, suggesting the issue might be with visualization or access, not just technique.
- Critically, the patient's oxygen saturation is dropping rapidly, requiring a quicker, more definitive solution than another attempt at orotracheal intubation.
*Comfort measures only*
- The patient has **no advance directive**, and family members have not arrived to make decisions regarding end-of-life care.
- Despite the severity of his injuries, the patient is still alive and does not have clear indications for **comfort measures only** at this stage; resuscitative efforts are warranted.
*Tracheostomy*
- **Tracheostomy** is a surgical procedure for establishing a long-term airway and is not suitable for **emergent airway management** in a rapidly decompensating trauma patient.
- It typically requires specialized surgical expertise and takes longer to perform than a cricothyrotomy, which is a faster, life-saving measure in this acute situation.
Anesthesia in special populations US Medical PG Question 4: A 5-year-old boy is brought to the emergency department by his grandmother because of difficulty breathing. Over the past two hours, the grandmother has noticed his voice getting progressively hoarser and occasionally muffled, with persistent drooling. He has not had a cough. The child recently immigrated from Africa, and the grandmother is unsure if his immunizations are up-to-date. He appears uncomfortable and is sitting up and leaning forward with his chin hyperextended. His temperature is 39.5°C (103.1°F), pulse is 110/min, and blood pressure is 90/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 95%. Pulmonary examination shows inspiratory stridor and scattered rhonchi throughout both lung fields, along with poor air movement. Which of the following is the most appropriate next step in management?
- A. Nebulized albuterol
- B. Direct laryngoscopy and pharyngoscopy
- C. Immediate nasotracheal intubation in the emergency department
- D. Prepare for emergency airway management in the operating room with anesthesia and ENT backup (Correct Answer)
- E. Intravenous administration of antibiotics
Anesthesia in special populations Explanation: ***Prepare for emergency airway management in the operating room with anesthesia and ENT backup***
- The constellation of **hoarseness**, **muffled voice**, **drooling**, **inspiratory stridor**, **fever**, and the classic **tripod position** (sitting up, leaning forward, hyperextended chin) in an unimmunized child strongly indicates **epiglottitis**.
- Given the risk of **complete airway obstruction**, securing the airway in a controlled environment like the **operating room** with specialized personnel (**anesthesia**, **ENT**) is the safest and most appropriate immediate step.
*Nebulized albuterol*
- This medication is a **bronchodilator** primarily used for conditions like **asthma** or **bronchiolitis** that involve bronchospasm.
- It would not alleviate airway obstruction caused by supraglottic swelling in epiglottitis and could potentially worsen the child's distress.
*Direct laryngoscopy and pharyngoscopy*
- Performing a direct laryngoscopy or pharyngoscopy in the emergency department, especially without immediate intubation capabilities, could precipitate **laryngospasm** and **complete airway obstruction** in a child with suspected epiglottitis.
- Visualization of the airway should only be attempted in a controlled setting where immediate intubation or tracheostomy can be performed.
*Immediate nasotracheal intubation in the emergency department*
- While intubation is necessary, attempting it immediately in the emergency department without the controlled environment of an operating room and without the full support of anesthesia and ENT specialists carries significant risks.
- The swelling can make intubation extremely difficult and increase the likelihood of failed attempts or trauma, further compromising the airway.
*Intravenous administration of antibiotics*
- Although antibiotics are a crucial part of epiglottitis treatment (typically **ceftriaxone** or **cefotaxime** to cover *Haemophilus influenzae* type b), they are not the immediate priority.
- The most urgent threat is airway compromise; therefore, securing the airway takes precedence over initiating antibiotic therapy.
Anesthesia in special populations US Medical PG Question 5: A 70-year-old male is brought to the emergency department from a nursing home due to worsening mental status. His nurse reports that the patient has been very lethargic and sleeping more than usual for the past week. She found him confused and difficult to arouse this morning and decided to bring him to the ER. His past medical history is significant for small cell carcinoma of the lung for which he is receiving chemotherapy. He is also on lithium and bupropion for bipolar disorder. Other medications include metoprolol, valsartan, metformin, and insulin. On admission, blood pressure is 130/70 mm Hg, pulse rate is 100/min, respiratory rate is 17/min, and temperature is 36.5°C (97.7°F). He is drowsy and disoriented. Physical examination is normal. Finger-stick glucose level is 110 mg/dL. Other laboratory studies show:
Na+ 120 mEq/L (136—145 mEq/L)
K+ 3.5 mEq/L (3.5—5.0 mEq/L)
Cl- 107 mEq/L (95—105 mEq/L)
Creatinine 0.8 mg/dL (0.6—1.2 mg/dL)
Serum osmolality 250 mOsm/kg (275—295 mOsm/kg)
Urine Na+ 70 mEq/L
Urine osmolality 340 mOsm/kg
He is admitted to the hospital for further management. Which of the following is the most likely cause of this patient's condition?
- A. Psychogenic polydipsia
- B. Lithium
- C. Infection
- D. Carcinoma (Correct Answer)
- E. Bupropion
Anesthesia in special populations Explanation: ***Carcinoma***
- This patient's **small cell lung carcinoma** is the most likely cause of his presentation, as it is one of the **most common causes of paraneoplastic SIADH**.
- The laboratory findings are **classic for SIADH**: euvolemic hyponatremia (Na+ 120 mEq/L), low serum osmolality (250 mOsm/kg), inappropriately concentrated urine (urine osmolality 340 mOsm/kg), and elevated urine sodium (70 mEq/L).
- The **altered mental status** (lethargy, confusion) is consistent with severe hyponatremia.
- Small cell lung cancer accounts for approximately **15% of all SIADH cases** and should always be considered in this clinical context.
*Psychogenic polydipsia*
- While excessive water intake can cause hyponatremia, it typically presents with **very dilute urine** (low urine osmolality <100 mOsm/kg) and **low urine sodium** (<20 mEq/L).
- This patient has **concentrated urine** (340 mOsm/kg) and **elevated urine sodium** (70 mEq/L), which are inconsistent with psychogenic polydipsia.
*Lithium*
- Lithium toxicity can cause neurological symptoms but typically causes **nephrogenic diabetes insipidus**, leading to **hypernatremia** or normal sodium levels, not hyponatremia.
- Lithium-induced SIADH is exceedingly rare and would not be the most likely diagnosis in a patient with known small cell lung cancer.
- The patient's creatinine is normal (0.8 mg/dL), making significant lithium toxicity less likely.
*Infection*
- Infections (particularly pneumonia, meningitis, or CNS infections) can cause SIADH and altered mental status.
- However, this patient has **no fever** (temperature 36.5°C), and there are no other signs suggesting active infection.
- The **direct paraneoplastic association** between small cell lung cancer and SIADH makes carcinoma the more likely primary cause.
*Bupropion*
- Bupropion has been rarely associated with SIADH in case reports, but this is an **uncommon adverse effect**.
- Given the patient's **well-established risk factor** (small cell lung carcinoma) for SIADH, the malignancy is a far more likely cause than medication effect.
Anesthesia in special populations US Medical PG Question 6: A 59-year-old man presents to his primary care provider with the complaint of daytime fatigue. He often has a headache that is worse in the morning and feels tired when he awakes. He perpetually feels fatigued even when he sleeps in. The patient lives alone, drinks 2-3 beers daily, drinks coffee regularly, and has a 10 pack-year smoking history. His temperature is 99.0°F (37.2°C), blood pressure is 180/110 mm Hg, pulse is 80/min, respirations are 13/min, and oxygen saturation is 98% on room air. Physical exam is notable for a BMI of 39 kg/m^2. The rest of the patient's pulmonary and neurological exams are unremarkable. Which of the following is the best next step in management?
- A. Caffeine avoidance
- B. Screening for depression
- C. Alcohol avoidance in the evening
- D. CT head
- E. Weight loss (Correct Answer)
Anesthesia in special populations Explanation: ***Weight Loss***
- The patient's **BMI of 39 kg/m²** indicates **class III obesity**, which is the strongest modifiable risk factor for **obstructive sleep apnea (OSA)**. The clinical presentation—**daytime fatigue**, morning headaches, unrefreshing sleep despite adequate sleep duration, and hypertension—strongly suggests OSA.
- While **polysomnography** is the gold standard for confirming OSA, the clinical diagnosis is evident in this case. **Weight loss** is the most important initial therapeutic intervention, as even modest weight reduction (10% of body weight) can significantly improve or resolve OSA in obese patients.
- Weight loss reduces upper airway collapse by decreasing fatty tissue deposition around the pharynx and improving lung volumes. This addresses the underlying pathophysiology rather than just treating symptoms.
- This intervention also addresses his **hypertension** (180/110 mm Hg), which is commonly associated with and exacerbated by OSA.
*Caffeine avoidance*
- While excessive caffeine can disrupt sleep architecture, the patient's symptoms—particularly **morning headaches** and **unrefreshing sleep despite sleeping in**—are not characteristic of caffeine-induced insomnia, which typically presents with difficulty initiating sleep.
- These symptoms, combined with obesity and hypertension, point strongly to a sleep-related breathing disorder rather than a stimulant effect.
*Screening for depression*
- Fatigue is indeed a cardinal symptom of major depressive disorder, but the specific pattern here—**morning headaches** (from nocturnal hypercapnia/hypoxemia), **unrefreshing sleep**, and **obesity with hypertension**—is far more consistent with OSA.
- Depression screening could be considered if symptoms persist after addressing the sleep disorder, as untreated OSA can contribute to or worsen mood disorders.
*Alcohol avoidance in the evening*
- **Alcohol consumption** (2-3 beers daily) does worsen OSA by relaxing upper airway dilator muscles and suppressing arousal responses to hypoxemia. Evening alcohol avoidance would be a beneficial **adjunctive measure**.
- However, while helpful, this intervention is less impactful than weight loss. The patient's **severe obesity** (BMI 39 kg/m²) is the predominant and most modifiable risk factor, making weight loss the priority intervention that will have the greatest effect on reducing OSA severity.
*CT head*
- CT head would be indicated if there were focal neurological deficits, papilledema, or features suggesting increased intracranial pressure or structural brain pathology.
- This patient's **neurological exam is unremarkable**, and his headaches are characteristic of OSA (worse in the morning due to nocturnal CO₂ retention, improving throughout the day). Imaging is not warranted.
Anesthesia in special populations US Medical PG Question 7: A 5-year-old is brought into the emergency department for trouble breathing. He was at a family picnic playing when his symptoms began. The patient is currently struggling to breathe and has red, warm extremities. The patient has an unknown medical history and his only medications include herbs that his parents give him. His temperature is 99.5°F (37.5°C), pulse is 112/min, blood pressure is 70/40 mmHg, respirations are 18/min, and oxygen saturation is 82% on 100% O2. Which of the following is the best initial step in management?
- A. Intubation
- B. Albuterol
- C. Cricothyroidotomy
- D. Albuterol, ipratropium, and magnesium
- E. Epinephrine (Correct Answer)
Anesthesia in special populations Explanation: ***Epinephrine***
- This patient is exhibiting signs of **anaphylactic shock** (difficulty breathing, red/warm extremities, hypotension) likely triggered by an allergen at the picnic. **Epinephrine** is the first-line treatment for anaphylaxis due to its alpha and beta-adrenergic effects that counteract vasodilation, bronchoconstriction, and histamine release.
- The rapid onset of symptoms and cardiovascular collapse (hypotension) necessitate immediate administration of epinephrine to stabilize the patient.
*Intubation*
- While the patient is in respiratory distress, intubation is a more invasive procedure and not the *initial* best step for anaphylactic shock. **Epinephrine** should be administered first to address the underlying physiological derangements.
- Airway management, including intubation, may be necessary if epinephrine fails to improve respiratory status, but it is secondary to addressing the systemic allergic reaction.
*Albuterol*
- **Albuterol** is a bronchodilator that helps with bronchospasm, but it does not address the widespread vasodilation, hypotension, or other systemic effects of anaphylaxis.
- While it might provide some symptomatic relief for breathing, it is insufficient as a standalone treatment for anaphylactic shock and would not prevent cardiovascular collapse.
*Cricothyroidotomy*
- **Cricothyroidotomy** is an emergency airway procedure used when conventional intubation is impossible due to upper airway obstruction.
- In this scenario, the primary issue is systemic anaphylaxis causing bronchospasm and shock, not an isolated upper airway obstruction, making epinephrine the more appropriate initial intervention.
*Albuterol, ipratropium, and magnesium*
- This combination is typically used for severe asthma exacerbations, focusing on bronchodilation and smooth muscle relaxation.
- Like albuterol alone, this combination does not address the underlying systemic vasodilation and hypotension characteristic of anaphylactic shock, which requires **epinephrine**.
Anesthesia in special populations US Medical PG Question 8: A 55-year-old man presents to the physician for the evaluation of excessive daytime sleepiness over the past six months. Despite sleeping 8–9 hours a night and taking a nap during the day, he feels drowsy and is afraid to drive. His wife complains of loud snoring and gasping during the night. His blood pressure is 155/95 mm Hg. BMI is 37 kg/m2. Oropharyngeal examination shows a small orifice and an enlarged tongue and uvula. The soft palate is low-lying. The examination of the nasal cavity shows no septal deviation or polyps. Examination of the lungs and heart shows no abnormalities. Polysomnography shows an apnea-hypopnea index of 20 episodes/h. The patient is educated about weight loss, exercise, and regular sleep hours and duration. Which of the following is the most appropriate next step in management?
- A. Continuous positive airway pressure (Correct Answer)
- B. Upper airway neurostimulation
- C. Supplemental oxygen
- D. Oral appliances
- E. Upper airway surgery
Anesthesia in special populations Explanation: ***Continuous positive airway pressure***
- This patient presents with symptoms and polysomnography findings consistent with **moderate to severe obstructive sleep apnea (OSA)** (apnea-hypopnea index of 20 episodes/h). **CPAP is the first-line treatment** for such cases.
- CPAP works by **delivering pressurized air** via a mask, creating a pneumatic splint that prevents the collapse of the upper airway during sleep, thereby reducing apneas and hypopneas.
*Upper airway neurostimulation*
- This therapy involves stimulating the **hypoglossal nerve** to activate upper airway muscles, improving airway patency.
- However, it is generally considered a **second-line treatment** for patients with moderate to severe OSA who **cannot tolerate or fail CPAP therapy**.
*Supplemental oxygen*
- While oxygen therapy can reduce nocturnal desaturation, it **does not address the underlying airway obstruction** that causes apneas and hypopneas.
- It might even **worsen apnea by blunting the ventilatory drive**, making it an inappropriate primary treatment for OSA.
*Oral appliances*
- **Mandibular advancement devices (MADs)** can be effective for **mild to moderate OSA**, or for patients with severe OSA who cannot tolerate CPAP.
- They work by repositioning the jaw and tongue forward to enlarge the pharyngeal space, but CPAP is generally more effective for the severity described.
*Upper airway surgery*
- Various surgical procedures, such as **uvulopalatopharyngoplasty (UPPP)**, aim to remove excess tissue in the pharynx to enlarge the airway.
- Surgery is typically reserved for patients who **fail or cannot tolerate CPAP and oral appliances** and are carefully selected based on anatomical considerations.
Anesthesia in special populations US Medical PG Question 9: A 23-year-old G1P0 woman presents to the emergency department with regular and painful contractions that occur every 3 minutes. She was at home cooking dinner when she experienced a deluge of clear fluid between her legs followed by painful contractions. The patient has a past medical history of obesity. Her pregnancy was not followed by an obstetrician, but she notes that she experienced abdominal pain and headaches frequently towards the end of her pregnancy. Her temperature is 99.5°F (37.5°C), blood pressure is 187/128 mmHg, pulse is 110/min, respirations are 17/min, and oxygen saturation is 98% on room air. The patient is started on magnesium sulfate and labetalol. The patient delivers her baby vaginally 2 hours later. On the labor and delivery floor, the patient is notably somnolent. Vitals are notable for respirations of 6 per minute. Physical exam reveals a somnolent woman who is minimally responsive. Cardiopulmonary exam is notable for hypopnea. Neurological exam reveals absent deep tendon reflexes and 3/5 strength in her upper and lower extremities. Which of the following is the next best step in management?
- A. Discontinue current drug infusion (Correct Answer)
- B. Remove retained fetal parts
- C. Ultrasound
- D. CT scan of the head
- E. Supportive therapy
Anesthesia in special populations Explanation: ***Discontinue current drug infusion***
- The patient's symptoms, including **somnolence, respiratory depression (hypopnea, 6 respirations/minute), absent deep tendon reflexes, and muscle weakness (3/5 strength)**, are highly suggestive of **magnesium toxicity**.
- Immediate discontinuation of the **magnesium sulfate infusion** is the critical first step to prevent further accumulation and worsening of toxicity.
*Remove retained fetal parts*
- This step is indicated for **postpartum hemorrhage** or infection due to retained placental fragments.
- The patient's symptoms are neurological and respiratory, not related to uterine bleeding or infection.
*Ultrasound*
- An ultrasound might be useful to assess for retained products of conception or other intra-abdominal issues if there were signs of hemorrhage or infection.
- However, the patient's primary symptoms indicate neurological and respiratory depression, which is not an indication for ultrasound.
*CT scan of the head*
- A CT scan of the head would be considered if there were concerns for **intracranial hemorrhage**, stroke, or other neurological emergencies, especially given her history of headaches and severe hypertension.
- While hypertension is present, the constellation of absent deep tendon reflexes and respiratory depression points more directly to drug toxicity than to an acute intracranial event.
*Supportive therapy*
- Supportive therapy (e.g., **calcium gluconate as antidote**, airway management, mechanical ventilation) is essential and should be provided **concurrently** with stopping the magnesium infusion.
- However, the *next best step* prioritizes **stopping the source of toxicity** first, as continued infusion would worsen the patient's condition despite supportive measures.
- Without discontinuing the magnesium sulfate, supportive therapy alone would be insufficient to reverse the ongoing toxicity.
Anesthesia in special populations US Medical PG Question 10: A 19-year-old man is brought to the emergency department 35 minutes after being involved in a high-speed motor vehicle collision. On arrival, he is alert, has mild chest pain, and minimal shortness of breath. He has one episode of vomiting in the hospital. His temperature is 37.3°C (99.1°F), pulse is 108/min, respirations are 23/min, and blood pressure is 90/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 92%. Examination shows multiple abrasions over his trunk and right upper extremity. There are coarse breath sounds over the right lung base. Cardiac examination shows no murmurs, rubs, or gallop. Infusion of 0.9% saline is begun. He subsequently develops increasing shortness of breath. Arterial blood gas analysis on 60% oxygen shows:
pH 7.36
pCO2 39 mm Hg
pO2 68 mm Hg
HCO3- 18 mEq/L
O2 saturation 81%
An x-ray of the chest shows patchy, irregular infiltrates over the right lung fields. Which of the following is the most likely diagnosis?
- A. Pneumothorax
- B. Pulmonary contusion (Correct Answer)
- C. Aspiration pneumonia
- D. Acute respiratory distress syndrome
- E. Pulmonary embolism
Anesthesia in special populations Explanation: ***Pulmonary contusion***
- The patient's presentation with **hypoxia**, increasing shortness of breath after a high-speed motor vehicle collision, and **patchy, irregular infiltrates** on chest x-ray despite initial hydration, are highly suggestive of **pulmonary contusion**.
- The coarse breath sounds over the right lung base further support the presence of parenchymal injury and hemorrhage in the lung tissue.
*Pneumothorax*
- While a pneumothorax is common after trauma, the chest x-ray would typically show a **collapsed lung** and **absence of lung markings** in the affected area, which is not described.
- The presence of coarse breath sounds suggests air entry, not a complete absence due to collapsed lung.
*Aspiration pneumonia*
- Although the patient had one episode of vomiting, **aspiration pneumonia** typically develops hours to days after aspiration, presenting with fever and signs of infection.
- The acute onset of symptoms within minutes of trauma and the lack of fever make aspiration pneumonia less likely as the primary diagnosis immediately following the accident.
*Acute respiratory distress syndrome*
- **Acute respiratory distress syndrome (ARDS)** is a severe inflammatory lung injury that typically develops **24 to 72 hours** after an initial insult, not immediately.
- While the patient has hypoxia, the diffuse bilateral infiltrates characteristic of ARDS are not seen, and his symptoms are too acute for ARDS to be the primary cause at 35 minutes post-injury.
*Pulmonary embolism*
- A **pulmonary embolism** would typically present with sudden onset of shortness of breath and pleuritic chest pain, often without significant findings on chest x-ray or presenting with a **wedge-shaped infiltrate**.
- Given the direct chest trauma and immediate onset of respiratory compromise, a pulmonary contusion is a more direct and acute consequence.
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