Surgical management timing US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Surgical management timing. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Surgical management timing US Medical PG Question 1: An 8-year-old boy and his 26-year-old babysitter are brought into the emergency department with severe injuries caused by a motor vehicle accident. The child is wheeled to the pediatric intensive care unit with a severe injury to his right arm, as well as other external and internal injuries. He is hemorrhaging and found to be hemodynamically unstable. He subsequently requires transfusion and surgery, and he is currently unconscious. The pediatric trauma surgeon evaluates the child’s arm and realizes it will need to be amputated at the elbow. Which of the following is the most appropriate course of action to take with regards to the amputation?
- A. Obtain an emergency court order from a judge to obtain consent to amputate the child’s arm
- B. Find the child’s parents to obtain consent to amputate the child’s arm
- C. Amputate the child’s arm at the elbow joint (Correct Answer)
- D. Wait for the child’s babysitter to recover from her injuries to obtain her consent to amputate the child’s arm
- E. Wait for the child to gain consciousness to obtain his consent to amputate his arm
Surgical management timing Explanation: ***Amputate the child’s arm at the elbow joint***
- In an emergency situation where a child's life is at risk and a procedure is immediately necessary to save their life or prevent significant harm, **implied consent** allows for medical intervention without explicit parental consent. The child's **hemodynamic instability** and **severe hemorrhage** indicate an immediate threat to life.
- The decision to amputate to save the child's life is a **medically necessary emergency intervention**. Waiting for consent would cause a dangerous delay.
*Obtain an emergency court order from a judge to obtain consent to amputate the child’s arm*
- While court orders can be used in cases of parental refusal or unavailability for non-emergency procedures, the **urgent nature** of this life-threatening situation precludes waiting for a court order.
- The delay in obtaining a court order could significantly worsen the child's prognosis or lead to death.
*Find the child’s parents to obtain consent to amputate the child’s arm*
- Although parental consent is generally required for minors, the child's **critical condition** and **hemodynamic instability** mean delaying life-saving treatment to locate parents would be medically irresponsible.
- The principle of **beneficence** (acting in the best interest of the patient) and avoiding harm takes precedence in this emergency.
*Wait for the child’s babysitter to recover from her injuries to obtain her consent to amputate the child’s arm*
- A babysitter is generally not legally authorized to provide consent for major medical procedures for a child, especially an amputation.
- Even if the babysitter had some form of temporary custody, her own injury makes her an unreliable source of consent, and the delay would be critical.
*Wait for the child to gain consciousness to obtain his consent to amputate his arm*
- An 8-year-old child is generally not considered mature enough to provide **informed consent** for such a major medical decision.
- The child is **unconscious and hemodynamically unstable**, making it impossible to obtain consent and dangerously delaying a life-saving procedure.
Surgical management timing US Medical PG Question 2: A 4-year-old boy is brought to the physician by his parents for bedwetting. He went 3 months without wetting the bed but then started again 6 weeks ago. He has been wetting the bed about 1–2 times per week. He has not had daytime urinary incontinence or dysuria. His teachers report that he is attentive in preschool and plays well with his peers. He is able to name 5 colors, follow three-step commands, and recite his address. He can do a somersault, use scissors, and copy a square. Physical examination shows no abnormalities. Which of the following is the most appropriate next step in management?
- A. IQ testing
- B. Enuresis alarm
- C. Bladder ultrasound
- D. Oxybutynin therapy
- E. Reassurance (Correct Answer)
Surgical management timing Explanation: ***Reassurance***
- This 4-year-old boy presents with secondary enuresis, which is common and often **resolves spontaneously with time**. Given his age and lack of other concerning symptoms (daytime incontinence, dysuria, developmental delays), initial management should focus on **reassurance** and education for the parents.
- At this age, the **prevalence of enuresis is still high (around 20%)**, and many children have not yet achieved consistent nighttime bladder control. There is **no evidence of organic pathology** or significant psychological distress based on the provided information.
*Enuresis alarm*
- While effective for enuresis, enuresis alarms are generally considered for children **over 5-7 years old** or older with persistent enuresis, after initial conservative measures and observation.
- For a 4-year-old, the primary approach is often to **wait and monitor**, as developmental maturation plays a significant role.
*IQ testing*
- The boy's developmental milestones (naming colors, following commands, gross and fine motor skills) are **appropriate for his age**, and his teachers report no concerns.
- There is **no indication of global developmental delay** or cognitive impairment that would necessitate IQ testing.
*Bladder ultrasound*
- This child exhibits no signs or symptoms suggesting an underlying urological abnormality, such as **daytime incontinence, frequent urinary tract infections, dysuria, or abnormal voiding patterns**.
- A bladder ultrasound would be considered in cases with **red flag symptoms** or if initial conservative management of enuresis fails in older children to rule out structural issues.
*Oxybutynin therapy*
- Oxybutynin is an **anticholinergic medication** used to treat overactive bladder symptoms or severe enuresis, typically in older children when other treatments have failed.
- It is **not a first-line therapy** for a 4-year-old with secondary enuresis without other symptoms, as the condition is likely developmental.
Surgical management timing US Medical PG Question 3: A 6-month-old boy is brought to the physician because of a right-sided scrotal swelling for the past 2 months. The swelling is intermittent and appears usually after the patient has been taken outdoors in a baby carrier, and disappears the next morning. The patient was born at term without complications and has been healthy. Examination shows a 3-cm, soft, nontender, and fluctuant right scrotal mass that is reducible and does not extend into the inguinal area. A light held behind the scrotum shines through. There are no bowel sounds in the mass. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in the management of this patient?
- A. Reassurance and follow-up (Correct Answer)
- B. Percutaneous drainage
- C. Ligation of the patent processus vaginalis
- D. Bilateral orchidopexy
- E. Surgical excision of the mass
Surgical management timing Explanation: ***Reassurance and follow-up***
- The presentation of an **intermittent, reducible, transilluminating scrotal swelling** in an infant, particularly one that resolves with rest, is characteristic of a **communicating hydrocele**.
- Most communicating hydroceles in infants resolve spontaneously by **12-18 months of age** as the **processus vaginalis** closes, so watchful waiting is the most appropriate initial management.
*Percutaneous drainage*
- This procedure is generally not recommended for communicating hydroceles due to the **risk of infection**, recurrence, and injury to scrotal structures.
- It does not address the underlying issue of the patent processus vaginalis, making it an ineffective long-term solution.
*Ligation of the patent processus vaginalis*
- This is the surgical treatment for a communicating hydrocele, but it is typically reserved for cases that **persist beyond 12-18 months of age** or those that cause complications.
- Given the patient's age (6 months) and the benign nature of the swelling, immediate surgical intervention is not indicated.
*Bilateral orchidopexy*
- **Orchidopexy** (surgical repositioning of a testis) is performed for **undescended testes**, which is not indicated by the patient's presentation.
- This patient has a scrotal swelling, and the testes are presumed to be in their normal position.
*Surgical excision of the mass*
- This is an overly aggressive and inappropriate intervention for a suspected communicating hydrocele.
- The mass is fluid-filled and caused by a patent processus vaginalis, not a solid tumor requiring excision.
Surgical management timing US Medical PG Question 4: Cardiac surgery is consulted on a newborn with a large ventricular septal defect. The child has poor weight gain and feeding difficulties. He requires furosemide and captopril to avoid dyspnea. On physical examination his temperature is 36.9°C (98.4°F), pulse rate is 158/min, respiratory rate is 30/min, and blood pressure is 94/62 mm Hg. Chest auscultation reveals a holosystolic murmur along the left lower sternal border and a mid-diastolic low-pitched rumble at the apex. Abdominal examination reveals the presence of hepatomegaly. An echocardiogram confirms a diagnosis of a membranous VSD while hemodynamic studies show a Qp:Qs ratio of 2.8:1. Which of the following is the best management option?
- A. Continue medical treatment and provide reassurance about spontaneous closure of the defect
- B. Hybrid surgery using both transcatheter device and surgical repair
- C. Transcatheter occlusion of the defect
- D. Surgical closure of the defect (Correct Answer)
- E. Addition of digoxin to the current medical regimen with regular follow-up until spontaneous closure occurs
Surgical management timing Explanation: ***Surgical closure of the defect***
* This newborn exhibits **symptoms of severe heart failure** due to a large VSD, including poor weight gain, feeding difficulties, and hepatomegaly, despite maximal medical therapy.
* A **Qp:Qs ratio of 2.8:1** indicates a significant left-to-right shunt, which, combined with the clinical picture, necessitates **surgical intervention** to prevent irreversible pulmonary vascular disease and improve prognosis.
*Continue medical treatment and provide reassurance about spontaneous closure of the defect*
* While some small VSDs close spontaneously, this child has a **large VSD** with **symptoms of severe heart failure** that require aggressive medical management (furosemide, captopril) and show no signs of improvement.
* **Reassurance of spontaneous closure** is inappropriate given the significant hemodynamic compromise and the potential for long-term complications without surgical intervention.
*Hybrid surgery using both transcatheter device and surgical repair*
* Hybrid approaches are typically reserved for **complex congenital heart defects** or specific anatomical challenges where a purely transcatheter or open surgical approach is not feasible or optimal.
* For a large membranous VSD requiring definitive closure, a **direct surgical approach** is generally preferred and more effective.
*Transcatheter occlusion of the defect*
* **Transcatheter occlusion** is generally indicated for **smaller, hemodynamically insignificant VSDs** or in specific anatomical situations, and it is usually performed in older children.
* A **large membranous VSD** with significant shunt and symptoms of heart failure is typically **not amenable to transcatheter closure** due to the size and location of the defect, and the risk of complications.
*Addition of digoxin to the current medical regimen with regular follow-up until spontaneous closure occurs*
* The child is already on **maximal medical therapy** (furosemide, captopril) and still experiencing severe symptoms, indicating medicine alone is insufficient.
* While digoxin can improve myocardial contractility, it is unlikely to significantly alter the natural history or **resolve the large shunt** in a VSD of this magnitude, and waiting for spontaneous closure would be detrimental.
Surgical management timing US Medical PG Question 5: A 4-month-old girl is brought to the physician because she has been regurgitating and vomiting 10–15 minutes after feeding for the past 3 weeks. She is breastfed and formula-fed. She was born at 38 weeks' gestation and weighed 2966 g (6 lb 9 oz). She currently weighs 5878 g (12 lb 15 oz). She appears healthy. Vital signs are within normal limits. Examination shows a soft and nontender abdomen and no organomegaly. Which of the following is the most appropriate next best step in management?
- A. Upper endoscopy
- B. Ultrasound of the abdomen
- C. Esophageal pH monitoring
- D. Positioning therapy (Correct Answer)
- E. Pantoprazole therapy
Surgical management timing Explanation: ***Positioning therapy***
- This infant is thriving, as evidenced by her significant weight gain, despite her regurgitation and vomiting. Her examination is also benign. These features make **gastroesophageal reflux (GER)**, a physiological process, the most likely diagnosis.
- **Positioning therapy** (e.g., keeping the infant upright during and after feeds) is a first-line, conservative management strategy for GER in infants who are otherwise healthy and gaining weight well.
*Upper endoscopy*
- **Upper endoscopy** is an invasive procedure and is typically reserved for evaluating patients with suspected complicated gastroesophageal reflux disease (GERD), such as those with **poor weight gain**, **hematemesis**, or **esophagitis**, none of which are seen here.
- It would not be the initial step in a thriving infant with symptoms consistent with uncomplicated GER.
*Ultrasound of the abdomen*
- An **abdominal ultrasound** is primarily used to diagnose **pyloric stenosis** in infants, which typically presents with **projectile, non-bilious vomiting** and **poor weight gain** or weight loss, usually between 3 and 6 weeks of age.
- This infant's symptoms are different in character (regurgitation/vomiting 10-15 minutes after feeding, not projectile) and she is gaining weight well, making pyloric stenosis less likely.
*Esophageal pH monitoring*
- **Esophageal pH monitoring** is used to quantify acid reflux episodes and is typically reserved for infants with atypical symptoms, suspected **complicated GERD**, or those who have failed empirical therapy.
- It is not indicated as a primary diagnostic or management step in a healthy, thriving infant with typical GER symptoms.
*Pantoprazole therapy*
- **Proton pump inhibitors (PPIs)** like pantoprazole are used to treat **GERD** by reducing stomach acid production, especially in cases with evidence of **esophagitis** or significant symptoms impacting growth or comfort.
- Given this infant is thriving and has no signs of complications, acid-suppressing medication is not appropriate as the initial management step; conservative measures should be tried first.
Surgical management timing US Medical PG Question 6: A 4-year-old-female presents with a flattened, reddish 2 cm lump located at the base of the tongue. The patient's mother reports her having trouble swallowing, often leading to feeding difficulties. The mother also reports lethargy, constipation, dry skin, and hypothermia. Which of the following is the most appropriate management of this patient’s presentation?
- A. Week-long course of penicillin
- B. No treatment is necessary, counsel mother on alternative feeding techniques
- C. Thyroid hormone replacement therapy with levothyroxine (Correct Answer)
- D. Combination therapy of methimazole and Beta-blockers
- E. Radioactive iodine ablation
Surgical management timing Explanation: ***Thyroid hormone replacement therapy with levothyroxine***
- The patient's symptoms of **lethargy, constipation, dry skin, and hypothermia** are classic signs of **hypothyroidism**
- The **flattened, reddish 2 cm lump at the base of the tongue** causing **dysphagia** is highly suggestive of a **lingual thyroid**, a developmental anomaly where thyroid tissue fails to descend from the base of the tongue during embryonic development
- In **90% of lingual thyroid cases**, this ectopic tissue represents the **only functioning thyroid tissue** in the body, leading to hypothyroidism
- **Levothyroxine replacement** is the first-line management, addressing the hypothyroidism and often reducing the size of the lingual thyroid mass, improving swallowing difficulties
- Surgical excision is reserved for cases where medical management fails or severe airway/swallowing obstruction persists
*Week-long course of penicillin*
- Penicillin is an **antibiotic** used to treat **bacterial infections**
- The patient's symptoms indicate an **endocrine disorder** (hypothyroidism) and **developmental anomaly** (lingual thyroid), not an infectious process
- No signs of infection such as fever, leukocytosis, or acute inflammation are present
*No treatment is necessary, counsel mother on alternative feeding techniques*
- Given the **significant systemic symptoms** of hypothyroidism (lethargy, constipation, dry skin, hypothermia) and feeding difficulties, **treatment is clearly necessary**
- **Untreated congenital hypothyroidism** in a child leads to severe developmental delays, intellectual disability, and growth retardation (cretinism)
- While feeding techniques may help with dysphagia, they do not address the underlying hypothyroidism requiring urgent treatment
*Combination therapy of methimazole and Beta-blockers*
- **Methimazole** (antithyroid medication) and **beta-blockers** are used to treat **hyperthyroidism** (overactive thyroid)
- The patient's symptoms (lethargy, constipation, hypothermia, dry skin) are characteristic of **hypothyroidism** (underactive thyroid), making antithyroid therapy completely inappropriate
- This would further suppress thyroid function and worsen the patient's condition
*Radioactive iodine ablation*
- **Radioactive iodine (I-131) ablation** is used to treat **hyperthyroidism** (Graves' disease, toxic nodules) or **thyroid cancer**
- It is a **destructive treatment** that eliminates thyroid tissue
- In this patient with a **lingual thyroid likely representing the only functioning thyroid tissue**, ablation would cause **complete thyroid failure** and severe, permanent hypothyroidism
- Radioactive iodine is also **contraindicated in children** except for specific cases of thyroid cancer
Surgical management timing US Medical PG Question 7: A 2-year-old boy is brought to a pediatrician because his parents have noticed that he seems to be getting tired very easily at home. Specifically, they have noticed that he is often panting for breath after walking around the house for a few minutes and that he needs to take naps fairly often throughout the day. He has otherwise been well, and his parents do not recall any recent infections. He was born at home, and his mom did not receive any prenatal care prior to birth. Physical exam reveals a high-pitched, harsh, holosystolic murmur that is best heard at the lower left sternal border. No cyanosis is observed. Which of the following oxygen tension profiles would most likely be seen in this patient? (LV = left ventricle, RV = right ventricle, and SC = systemic circulation).
- A. LV: normal, RV: normal, SC: normal
- B. LV: normal, RV: increased, SC: normal (Correct Answer)
- C. LV: decreased, RV: increased, SC: decreased
- D. LV: decreased, RV: normal, SC: decreased
- E. LV: normal, RV: normal, SC: decreased
Surgical management timing Explanation: ***LV: normal, RV: increased, SC: normal***
- The patient's presentation with easy fatigability, dyspnea on exertion, and a **holosystolic murmur** at the **lower left sternal border** strongly suggests a **ventricular septal defect (VSD)**. These symptoms result from a **left-to-right shunt**, leading to increased blood flow and pressure in the **right ventricle (RV)** and pulmonary circulation.
- In a VSD, highly oxygenated blood from the **left ventricle (LV)** shunts into the RV. This increases the **oxygen tension** in the RV, while the LV and systemic circulation (SC) typically maintain normal oxygen tension if the shunt is not so large that it causes **pulmonary hypertension** with **Eisenmenger syndrome**.
*LV: normal, RV: normal, SC: normal*
- This profile would indicate a **normal cardiovascular system** without any significant shunting or cardiac anomaly.
- It does not align with the patient's symptoms of easy fatigability, dyspnea, and the presence of a pathological murmur.
*LV: decreased, RV: increased, SC: decreased*
- A **decreased oxygen tension in the left ventricle** and **systemic circulation** typically indicates a **right-to-left shunt** or severe **pulmonary disease**, often associated with **cyanosis**, which is noted as absent in this patient.
- While RV oxygen tension *could* be increased in some complex congenital heart diseases with right-to-left shunting (e.g., mixing lesions), the overall profile does not fit the characteristic presentation of a VSD without cyanosis.
*LV: decreased, RV: normal, SC: decreased*
- This profile with **decreased oxygen tension in the left ventricle** and **systemic circulation** suggests a condition where oxygenated blood supply to the systemic circulation is compromised, such as severe **left ventricular dysfunction** or a **right-to-left shunt**.
- A **normal RV oxygen tension** without **cyanosis** makes this unlikely in the context of the patient's symptoms.
*LV: normal, RV: normal, SC: decreased*
- A **decreased oxygen tension in the systemic circulation** with **normal LV and RV oxygen tension** is inconsistent with a **VSD**.
- This profile might be observed in conditions like severe **anemia** or **hypoxia** without a primary cardiac shunt.
Surgical management timing US Medical PG Question 8: A 5-month-old boy is brought to the emergency department by his mother because his lips turned blue for several minutes while playing earlier that evening. She reports that he has had similar episodes during feeding that resolved quickly. He was born at term following an uncomplicated pregnancy and delivery. He is at the 25th percentile for length and below the 5th percentile for weight. His temperature is 37°C (98.6°F), pulse is 130/min, blood pressure is 83/55 mm Hg, and respirations are 42/min. Pulse oximetry on room air shows an oxygen saturation of 90%. During the examination, he sits calmly in his mother's lap. He appears well. The patient begins to cry when examination of his throat is attempted; his lips and fingers begin to turn blue. Further evaluation of this patient is most likely to show which of the following?
- A. Pulmonary vascular congestion on x-ray of the chest
- B. Right axis deviation on ECG (Correct Answer)
- C. Anomalous pulmonary venous return on MR angiography
- D. Diminutive left ventricle on echocardiogram
- E. Machine-like hum on auscultation
Surgical management timing Explanation: ***Right axis deviation on ECG***
- The presentation of **cyanotic spells** ("blue lips for several minutes", "lips and fingers begin to turn blue" with crying), **poor weight gain**, and **hypoxemia** (SpO2 90%) in an infant strongly suggests a **cyanotic congenital heart defect** like **Tetralogy of Fallot** (TOF).
- TOF is characterized by **right ventricular outflow tract obstruction**, leading to **right ventricular hypertrophy** and subsequently **right axis deviation** on ECG.
*Pulmonary vascular congestion on x-ray of the chest*
- **Pulmonary vascular congestion** is typically seen in conditions with **increased pulmonary blood flow** or **left-sided heart failure**, such as a large ventricular septal defect or patent ductus arteriosus.
- In Tetralogy of Fallot, there is often **decreased pulmonary blood flow** due to right ventricular outflow tract obstruction, leading to a **clear lung fields** on chest x-ray.
*Anomalous pulmonary venous return on MR angiography*
- **Total anomalous pulmonary venous return (TAPVR)** is a cyanotic heart defect where all pulmonary veins drain into the systemic circulation.
- While it causes cyanosis, it typically presents with **pulmonary congestion** and signs of **right heart strain**, which is less consistent with the spells described.
*Diminutive left ventricle on echocardiogram*
- A **diminutive left ventricle** is characteristic of **hypoplastic left heart syndrome**, which is a severe cyanotic defect.
- However, patients with hypoplastic left heart syndrome usually present with **severe heart failure** and shock much earlier in infancy, often in the neonatal period, which is not described here.
*Machine-like hum on auscultation*
- A **machine-like hum** is the classic auscultatory finding for a **patent ductus arteriosus (PDA)**.
- While a PDA can cause cyanosis if pulmonary hypertension is severe (Eisenmenger syndrome), isolated PDA typically presents with **left-to-right shunting** and **pulmonary overcirculation**, not the classic cyanotic spells seen with activities like crying, characteristic of TOF.
Surgical management timing US Medical PG Question 9: A 1-day-old infant born at full term by uncomplicated spontaneous vaginal delivery is noted to have cyanosis of the oral mucosa. The baby otherwise appears comfortable. On examination, his respiratory rate is 40/min and pulse oximetry is 80%. His left thumb is displaced and hypoplastic. A right ventricular lift is palpated, S1 is normal, S2 is single, and a harsh 3/6 systolic ejection murmur is heard at the left upper sternal border. Chest X-ray is shown. Which of the following is the most likely diagnosis?
- A. Tetralogy of Fallot (Correct Answer)
- B. Ventricular septal defect
- C. Pneumothorax
- D. Transient tachypnoea of the newborn
- E. Transposition of great vessels
Surgical management timing Explanation: ***Tetralogy of Fallot***
- The combination of **cyanosis**, a **right ventricular lift**, a harsh **systolic ejection murmur**, and **hypoplastic thumb** (suggesting **VACTERL association** or **TAR syndrome**) with an abnormal chest X-ray (likely showing an **upturned cardiac apex** or "boot-shaped" heart) strongly indicates Tetralogy of Fallot.
- The **single S2** is consistent with **pulmonary stenosis** or **pulmonary atresia**, and the low pulse oximetry (80%) highlights the cyanotic nature of this defect.
*Ventricular septal defect*
- While a VSD can cause a **systolic murmur** and a **right ventricular lift**, it typically presents with **acyanotic heart disease** until pulmonary hypertension develops much later.
- The severe **cyanosis** (80% SpO2) and **single S2** (implying pulmonary obstruction) are not typical features of an isolated VSD.
*Pneumothorax*
- A pneumothorax would present with **respiratory distress** (tachypnea, grunting), **diminished breath sounds** on the affected side, and potentially mediastinal shift, which are not described.
- It does not explain the presence of a **cardiac murmur**, the specific cyanosis patterns, or the associated limb abnormality.
*Transient tachypnoea of the newborn*
- This condition presents with **respiratory distress** and tachypnea, usually resolving within 24-48 hours.
- It does not involve **cyanosis to this degree**, a **cardiac murmur**, or a **hypoplastic thumb**.
*Transposition of great vessels*
- While TGV presents with severe **cyanosis** and a single S2 (if restrictive VSD), it typically has a **quiet precordium** or a less prominent murmur unless associated with a large VSD, and severe cyanosis does not improve with O2.
- The description of a **harsh systolic ejection murmur** and the hypoplastic thumb are less specific for isolated TGV, and the chest X-ray typically shows a **"egg-on-a-string" appearance**, though not always in the immediate newborn period.
Surgical management timing US Medical PG Question 10: A 9-month-old boy is brought to the pediatrician for evaluation of blue discoloration of the fingernails. His parents recently immigrated from Venezuela. No prior medical records are available. His mother states that during breastfeeding, he sweats and his lips turn blue. Recently, he has begun to crawl and she has noticed a similar blue discoloration in his fingers. The vital signs include: temperature 37℃ (98.6℉), blood pressure 90/60 mm Hg, pulse 100/min, and respiratory rate 26/min. On examination, he appeared to be in mild distress and cyanotic. Both fontanelles were soft and non-depressed. Cardiopulmonary auscultation revealed normal breath sounds and a grade 2/6 systolic ejection murmur at the left upper sternal border with a single S-2. He is placed in the knee-chest position. This maneuver is an attempt to improve this patient's condition by which of the following mechanisms?
- A. Increased systemic vascular resistance (Correct Answer)
- B. Decreased obstruction of the choanae
- C. Decreased pulmonary vascular resistance
- D. Increased systemic venous return
- E. Decreased systemic vascular resistance
Surgical management timing Explanation: ***Increased systemic vascular resistance***
* The **knee-chest position** is a classic intervention for **tet spells** in infants with **TOF (tetralogy of Fallot)**.
* By compressing the femoral arteries, this maneuver increases **systemic vascular resistance (SVR)**, thereby reducing right-to-left shunting across the **ventricular septal defect (VSD)** and improving pulmonary blood flow.
* *Decreased obstruction of the choanae*
* This maneuver has no impact on the patency of the **choanae** (the posterior nasal openings).
* **Choanal atresia** is a separate congenital anomaly that causes respiratory distress, which is not suggested by this patient's presentation.
* *Decreased pulmonary vascular resistance*
* The knee-chest position primarily affects SVR, not **pulmonary vascular resistance (PVR)**.
* While decreasing PVR would be beneficial by increasing pulmonary blood flow, this is not the direct mechanism of the knee-chest position.
* *Increased systemic venous return*
* While the knee-chest position can transiently affect venous return, its primary therapeutic effect in tet spells is on **SVR**.
* Increased venous return alone would not counteract the right-to-left shunt in TOF.
* *Decreased systemic vascular resistance*
* A decrease in **SVR** would worsen the patient's condition by exacerbating the right-to-left shunt across the VSD, leading to more **cyanosis**.
* The goal of the knee-chest position is precisely the opposite: to increase SVR.
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