Pre-operative evaluation US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Pre-operative evaluation. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Pre-operative evaluation US Medical PG Question 1: A 36-year-old woman is brought to the emergency department 20 minutes after being involved in a high-speed motor vehicle collision. On arrival, she is unconscious. Her pulse is 140/min, respirations are 12/min and shallow, and blood pressure is 76/55 mm Hg. 0.9% saline infusion is begun. A focused assessment with sonography shows blood in the left upper quadrant of the abdomen. Her hemoglobin concentration is 7.6 g/dL and hematocrit is 22%. The surgeon decided to move the patient to the operating room for an emergent explorative laparotomy. Packed red blood cell transfusion is ordered prior to surgery. However, a friend of the patient asks for the transfusion to be held as the patient is a Jehovah's Witness. The patient has no advance directive and there is no documentation showing her refusal of blood transfusions. The patient's husband and children cannot be contacted. Which of the following is the most appropriate next best step in management?
- A. Administer hydroxyethyl starch
- B. Transfusion of packed red blood cells (Correct Answer)
- C. Consult hospital ethics committee
- D. Administer high-dose iron dextran
Pre-operative evaluation Explanation: ***Transfusion of packed red blood cells***
- This patient is in **hemorrhagic shock** (tachycardia, hypotension, low hemoglobin, and hematocrit with evidence of active bleeding), requiring emergent blood transfusion to prevent irreversible organ damage and death.
- In an **emergency setting** with an **unconscious patient** and **no documented refusal** of blood products, the principle of **presumed consent** for life-saving treatment takes precedence, especially when next of kin cannot be reached.
*Administer hydroxyethyl starch*
- **Colloids** like hydroxyethyl starch can temporarily increase intravascular volume but do not provide oxygen-carrying capacity, which is critically needed for a patient with severe anemia and hemorrhagic shock.
- While useful for volume expansion, it is **not a substitute for blood products** in severe bleeding and can have adverse effects such as kidney injury.
*Consult hospital ethics committee*
- Consulting an ethics committee is appropriate for **complex ethical dilemmas** when there is time for deliberation and the patient's life is not in immediate danger.
- In this acute, life-threatening emergency, **delaying treatment** to consult an ethics committee would jeopardize the patient's life and is not appropriate.
*Administer high-dose iron dextran*
- **Iron dextran** is used to treat iron-deficiency anemia and works by supporting red blood cell production over several days to weeks.
- It is **ineffective in acute hemorrhagic shock** where immediate restoration of oxygen-carrying capacity is required.
Pre-operative evaluation US Medical PG Question 2: A 57-year-old man presents to his physician with dyspnea on exertion and rapid heartbeat. He denies any pain during these episodes. He works as a machine operator at a solar panels manufacturer. He has a 21-pack-year history of smoking. The medical history is significant for a perforated ulcer, in which he had to undergo gastric resection and bypass. He also has a history of depression, and he is currently taking escitalopram. The family history is unremarkable. The patient weighs 69 kg (152 lb). His height is 169 cm (5 ft 7 in). The vital signs include: blood pressure 140/90 mm Hg, heart rate 95/min, respiratory rate 12/min, and temperature 36.6℃ (97.9℉). Lung auscultation reveals widespread wheezes. Cardiac auscultation shows decreased S1 and grade 1/6 midsystolic murmur best heard at the apex. Abdominal and neurological examinations show no abnormalities. A subsequent echocardiogram shows increased left ventricular mass and an ejection fraction of 50%. Which of the options is a risk factor for the condition detected in the patient?
- A. History of gastric bypass surgery
- B. Exposure to heavy metals
- C. Escitalopram intake
- D. The patient’s body mass
- E. Smoking (Correct Answer)
Pre-operative evaluation Explanation: ***Smoking***
- The patient's 21-pack-year smoking history is a significant risk factor for **hypertension** and **cardiovascular disease**, contributing to increased left ventricular mass and cardiac dysfunction.
- Smoking directly damages blood vessels and the heart, leading to increased afterload and subsequent **left ventricular hypertrophy** (LVH), as seen on this patient's echocardiogram.
*History of gastric bypass surgery*
- While gastric bypass surgery is associated with malabsorption and nutritional deficiencies (including thiamine deficiency leading to wet beriberi), it is not a direct risk factor for **hypertensive heart disease** with LVH.
- The patient's elevated blood pressure (140/90 mm Hg) and smoking history are more directly responsible for the cardiac findings.
*Exposure to heavy metals*
- Exposure to certain heavy metals (e.g., lead, cadmium) can be associated with cardiovascular disease, but the patient's job as a machine operator at a solar panel manufacturer does not inherently imply significant exposure to these specific toxins.
- The presenting symptoms and echocardiogram findings are more directly attributable to **hypertension** and **smoking**, which are clearly documented risk factors in this patient.
*Escitalopram intake*
- Escitalopram is an SSRI antidepressant with a generally low cardiotoxicity profile; it is not associated with **left ventricular hypertrophy** or the development of structural heart disease.
- While some medications can affect cardiac function, escitalopram is not a primary risk factor for the observed changes.
*The patient's body mass*
- The patient's BMI can be calculated as 69 kg / (1.69 m)² ≈ 24.1 kg/m², which falls within the **normal weight range** (18.5-24.9 kg/m²).
- Therefore, obesity and its associated cardiac risks (which can contribute to hypertension and LVH) are not applicable to this patient's presentation.
Pre-operative evaluation US Medical PG Question 3: A surgeon is interested in studying how different surgical techniques impact the healing of tendon injuries. In particular, he will compare 3 different types of suture repairs biomechanically in order to determine the maximum load before failure of the tendon 2 weeks after repair. He collects data on maximum load for 90 different repaired tendons from an animal model. Thirty tendons were repaired using each of the different suture techniques. Which of the following statistical measures is most appropriate for analyzing the results of this study?
- A. Chi-squared
- B. Wilcoxon rank sum
- C. Pearson r coefficient
- D. Student t-test
- E. ANOVA (Correct Answer)
Pre-operative evaluation Explanation: ***ANOVA***
- **ANOVA (Analysis of Variance)** is appropriate here because it compares the means of **three or more independent groups** (the three different suture techniques) on a continuous dependent variable (maximum load before failure).
- The study has three distinct repair techniques, each with 30 tendons, making ANOVA suitable for determining if there are statistically significant differences among their mean failure loads.
*Chi-squared*
- The **Chi-squared test** is used for analyzing **categorical data** (frequencies or proportions) to determine if there is an association between two nominal variables.
- This study involves quantitative measurement (maximum load), not categorical data, making Chi-squared inappropriate.
*Wilcoxon rank sum*
- The **Wilcoxon rank sum test** (also known as Mann-Whitney U test) is a **non-parametric test** used to compare two independent groups when the data is not normally distributed or is ordinal.
- While the study has independent groups, it involves three groups, and the dependent variable is continuous, making ANOVA a more powerful and appropriate choice assuming normal distribution.
*Pearson r coefficient*
- The **Pearson r coefficient** measures the **strength and direction of a linear relationship between two continuous variables**.
- This study aims to compare means across different groups, not to determine the correlation between two continuous variables.
*Student t-test*
- The **Student t-test** is used to compare the means of **exactly two groups** (either independent or paired) on a continuous dependent variable.
- This study involves comparing three different suture techniques, not just two, making the t-test unsuitable.
Pre-operative evaluation US Medical PG Question 4: A researcher is trying to determine whether a newly discovered substance X can be useful in promoting wound healing after surgery. She conducts this study by enrolling the next 100 patients that will be undergoing this surgery and separating them into 2 groups. She decides which patient will be in which group by using a random number generator. Subsequently, she prepares 1 set of syringes with the novel substance X and 1 set of syringes with a saline control. Both of these sets of syringes are unlabeled and the substances inside cannot be distinguished. She gives the surgeon performing the surgery 1 of the syringes and does not inform him nor the patient which syringe was used. After the study is complete, she analyzes all the data that was collected and performs statistical analysis. This study most likely provides which level of evidence for use of substance X?
- A. Level 3
- B. Level 1 (Correct Answer)
- C. Level 4
- D. Level 5
- E. Level 2
Pre-operative evaluation Explanation: ***Level 1***
- The study design described is a **randomized controlled trial (RCT)**, which is considered the **highest level of evidence (Level 1)** in the hierarchy of medical evidence.
- Key features like **randomization**, **control group**, and **blinding (double-blind)** help minimize bias and strengthen the validity of the findings.
*Level 2*
- Level 2 evidence typically comprises **well-designed controlled trials without randomization** (non-randomized controlled trials) or **high-quality cohort studies**.
- While strong, they do not possess the same level of internal validity as randomized controlled trials.
*Level 3*
- Level 3 evidence typically includes **case-control studies** or **cohort studies**, which are observational designs and carry a higher risk of bias compared to RCTs.
- These studies generally do not involve randomization or intervention assignment by the researchers.
*Level 4*
- Level 4 evidence is usually derived from **case series** or **poor quality cohort and case-control studies**.
- These studies provide descriptive information or investigate associations without strong control for confounding factors.
*Level 5*
- Level 5 evidence is the **lowest level of evidence**, consisting of **expert opinion** or **animal research/bench research**.
- This level lacks human clinical data or systematic investigative rigor needed for higher evidence levels.
Pre-operative evaluation US Medical PG Question 5: A 62-year-old man comes to the physician in May for a routine health maintenance examination. He feels well. He underwent a right inguinal hernia repair 6 months ago. He has hypertension and type 2 diabetes mellitus. There is no family history of serious illness. Current medications include metformin, sitagliptin, enalapril, and metoprolol. He received the zoster vaccine 1 year ago. He received the PPSV23 vaccine 4 years ago. His last colonoscopy was 7 years ago and was normal. He smoked a pack of cigarettes a day for 20 years but quit 17 years ago. He drinks two to three alcoholic beverages on weekends. He is allergic to amoxicillin. He is scheduled to visit Australia and New Zealand in 2 weeks to celebrate his 25th wedding anniversary. He appears healthy. Vital signs are within normal limits. An S4 is heard at the apex. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate recommendation at this time?
- A. Colonoscopy
- B. Influenza vaccine (Correct Answer)
- C. Pneumococcal conjugate vaccine 13
- D. Cardiac stress test
- E. Abdominal ultrasound
Pre-operative evaluation Explanation: ***Influenza vaccine***
- Current guidelines recommend annual **influenza vaccination** for all adults, particularly those over 60 years old and those with chronic medical conditions like diabetes and hypertension.
- **Critical timing consideration**: The patient is traveling to Australia and New Zealand (Southern Hemisphere) in 2 weeks, where it will be **winter season** (May-September) with peak influenza activity.
- He is a **high-risk patient** (age >60, diabetes, hypertension, cardiovascular disease) who should receive influenza vaccine before travel to areas experiencing influenza season.
- This is the **most appropriate and time-sensitive recommendation** at this visit.
*Colonoscopy*
- The patient had a normal colonoscopy 7 years ago; current guidelines suggest a repeat colonoscopy every **10 years** for average-risk individuals.
- There are no new symptoms, family history, or risk factors that would necessitate an earlier repeat colonoscopy at this time.
*Pneumococcal conjugate vaccine 13*
- The patient received **PPSV23** four years ago at approximately age 58.
- Per **current CDC guidelines (2019+)**, PCV13 is **no longer routinely recommended** for immunocompetent adults ≥65 years old.
- PPSV23 alone is now the standard recommendation for adults ≥65, which this patient has already received.
- PCV13 may be considered through **shared decision-making** in specific circumstances, but is not a routine or urgent recommendation.
*Cardiac stress test*
- Although the patient has risk factors for cardiovascular disease (hypertension, diabetes, former smoker) and an **S4 heart sound** (indicating **left ventricular hypertrophy**), he is asymptomatic.
- Routine **screening stress tests** are not recommended for asymptomatic individuals without signs of active cardiac ischemia.
*Abdominal ultrasound*
- There are **no symptoms** or specific indications (e.g., abdominal aortic aneurysm screening criteria not met - would need age 65-75 with smoking history).
- The patient is 62 years old and quit smoking 17 years ago, so AAA screening criteria are not yet met.
- Routine screening abdominal ultrasounds are not indicated.
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