NBME 6 help!

[britesky89]

Hey guys I'm confused about 2 NMBE 6 questions. Any help/explanations would be appreciated. Thanks in advance!

1. A study is undertaken to compare the effectiveness 0f lorazepam vs midazolam in providing sedation for children who need mechanical ventilation. Approx 100 kids ages 2-12 who need mechanical ventilation are randomly assigned to receive a continuous infusion of either lorazepam or midazolam. The paralytic agents are given to 26 out of the 50 kids in the lorazepam group and 2 out of 50 in the midazolam group to ensure more synchronized ventilation. A sedation score ranging from 1 to 5 is used to assess the amount of movement for each kid over the course of 3 days ( here, 1 means no movement and 5 means thrashing movments). The results display a sedation score of 1 for 92% of the lorazepam group and 12% of the midazolam group. It is concluded that lorazepam was much more effective than lorzepam in completely sedating the patient. Which of the following features of this study raises the most concern regarding the validity of the conclusion?

A. confounding variables
B. lack of control group
C. sample size (WRONG)
D. statistical power
E. univariate scale

Some people are saying it's confounding but I don't understand why?

2. 13 yo B comes for sports physical exam. He has no serious illness and takes no meds. His maternal ad paternal grandfathers have HTN and DM2. The patient is at the 95th percentile for height and above the 95th percentile for weight and BMI. Vitals: temp is 98.1 F, HR is 84/min, resp is 16/min, BP is 130/83 (95th percentile). Exam shows no abnormalities. In addition to recommending participation in sports which of the following is the most appropriate pharmacotherapy?

A. ACE inhibitor
B. Beta adrenergic blocker
C. Calcium channer blocker
D. Thiazide diuretic (WRONG)
E. No pharmacotherapy is indicated

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[pd1112]

1. Power
2. You're going to medicate a 13-year-old with a normal blood pressure ?

 

[ru4real1666]

1. Power
2. You're going to medicate a 13-year-old with a normal blood pressure ?

Disagree with #1. It's not the power (they have enough patients), it is the fact that not enough patients in the midazolam group got the midazolam. This is a confounder. (Don't get fooled by words like 'univariate scale.' It means what you think it means; it's a scale that measures one variable.)

 

[britesky89]

I don't understand it's confounding? I thought confounding meant when one factor is related to both the exposure and outcome. How is the fact that not enough patients in the midazolam group got the midazolam related to both the exposure and outcome ?

 

[ru4real1666]

Hey. Sorry! I was quick to answer and misposted. I mean to say that on lorazepam group, they got paralytic agents which affected the outcome (not true for the midazolam group). It's confounding because it affects the relationship (predisposes you to be biased) when assessing the outcome for the lorazepam group (if you recall, confounding variables influence the relationship in a somewhat hidden manner - obviously not a technical definition).

 

[pd1112]

Disagree with #1. It's not the power (they have enough patients), it is the fact that not enough patients in the midazolam group got the midazolam. This is a confounder. (Don't get fooled by words like 'univariate scale.' It means what you think it means; it's a scale that measures one variable.)

I agree; it's confounding. I originally read the question as "only 2/50 in the midazolam group got midazolam," not "only 2/50 got paralytic agents." I thought they were saying sedation was better in 26 lorazepam patients than 2 midazolam patients, which would have very low power.