USMLE MCQ 31-35 : A seven year old child with chronic nasal obstruction has persistent disabling dysphagia causing sleep disturbance


Question: 31
A seven year old child with chronic nasal obstruction has persistent disabling dysphagia causing sleep disturbance. On inspection there is an appeareance of a 'clusters of grapes' located in the passage that connects the nasopharynx to the oropharxynx. The most appropriate treatment for this child would be
a) incision and drainage
b) adenoidectomy
c) laser treatment
d) steroids
e) interferon therapy

Question: 34
A middle aged woman is suspected of having a coagulation disorder affecting the intrinsic pathway before the prothrombin to thrombin stage. Which of the tests would be most appropriate in this patient ?
a) Activated partial thromboplastin time
b) Venous clotting time
c) Activated whole blood clotting time
d) Thrombin time
e) Plasma fibrinogen

Question: 35
A patient with chronic hypertension is on treatment with nifedipine, a calcium channel blocker.
Nifedipine lowers the blood pressure mainly by inhibiting the influx of extracellular calcium through the calcium channel of
a) skeletal muscle cells
b) smooth muscle cells
c) myocardial cells
d) cells in the atrioventricular (AV) node
e) cells in the sinoatrial (SA) node

Question: 31

Correct Answer: B
Clinical Indicators for Tonsillectomy/Adenoidectomy include a) Patient with 3 or more infections of tonsils and/or adenoids per year despite adequate medical therapy. b) Hypertrophy causing dental malocclusion or adversely affecting orofacial growth documented by orthodontist. c) Hypertrophy causing upper airway obstruction, severe dysphagia, sleep disorders, or cardiopulmonary complications. d) Peritonsillar abscess unresponsive to medical management and drainage documented by surgeon, unless surgery performed during acute stage. e) Persistent foul taste or breath due to chronic tonsillitis not responsive to medical therapy. f) Chronic or recurrent tonsillitis associated with the streptococcal carrier state and not responding to beta-lactamase-resistant antibiotics. g) Unilateral tonsil hypertrophy presumed neoplastic. h) Recurrent suppurative or otitis media with effusion. (Adenoidectomy alone. Tonsillectomy added requires one of the indications listed above.)

Question: 34

Correct Answer: A
The APTT is very sensitive to coagulation factor deficiencies within the intrinsic system before the prothrombin to thrombin stage. The precursor of the activated partial thromboplastin time (APTT) was the partial thromboplastin time (PTT). An incomplete thromboplastin reagent plus calcium is added to patient plasma, and the time necessary to form a fibrin clot is measured. The partial thromboplastin reagent is only a phospholipid platelet substitute without any of the other components of thromboplastin. The PTT was useful in detecting intrinsic factor abnormalities but was relatively insensitive to effects of heparin. Adding certain contact activators (usually chemicals or particulate matter, such as kaolin) to the PTT reagent was found to activate factor XII (contact factor) swiftly and uniformly and thus eliminate another variable in the clotting process. In addition, the activated APTT was found to be sensitive to heparin. The APTT is very sensitive to coagulation factor deficiencies within the intrinsic system before the prothrombin to thrombin stage. It may also be abnormal in prothrombin or fibrinogen deficiencies but only if the defect is relatively severe (prothrombin or fibrinogen/fibrin abnormalities may affect the test because the test depends on fibrin clot formation as the reaction end point).

Question: 35

Correct Answer: B
The selective calcium channel blockers share a similar antihypertensive mechanism of action: they inhibit the influx of extracellular calcium through the L-type channel, resulting in relaxation of vascular smooth muscle and reduction in vascular resistance. They are therefore often assumed to be a homogeneous family of drugs, whereas they are in fact an extremely heterogeneous group of compounds with marked differences in chemical structure, binding sites, tissue selectivity, and, consequently, clinical activity and therapeutic indication.
Selective calcium channel blockers include three discrete chemical types: the phenylalkylamines (eg, verapamil), the benzothiazepines (eg, diltiazem), and the 1,4-dihydropyridines (eg, nifedipine)
Binding sites for all three types of calcium channel blocker are found in a variety of tissues, including myocardium, smooth muscle, skeletal muscle, and glandular tissue. Yet this range of target tissues is not necessarily reflected in pharmacologic or therapeutic activity. For example, skeletal smooth muscle is relatively insensitive to calcium channel blockade, as indicated by the fact that calcium channel blocker therapy does not interfere with postural tone.

Like other calcium-channel antagonists, nifedipine inhibits the influx of extracellular calcium through myocardial and vascular membrane pores, which are selective for specific ions. Serum calcium levels remain unchanged. It is believed that nifedipine inhibits this influx by physically plugging the channel. While verapamil and diltiazem exert balanced effects on calcium channels in the SA node, AV node, and vasculature, nifedipine and other members of the dihydropyridine group act predominantly on the vasculature, making these agents more potent peripheral vasodilators. The decrease in intracellular calcium inhibits the contractile processes of smooth muscle cells, causing dilation of the coronary and systemic arteries. This results in increased oxygen delivery to the myocardial tissue, decreased total peripheral resistance, decreased systemic blood pressure, and decreased afterload.
In the past 15 to 20 years, numerous calcium channel blockers (CCBs) have been introduced. The CCBs lower blood pressure by inhibiting the entry of calcium ions into vascular smooth muscle cells, which:

Reduces vascular tone and contractility

Results in vasodilation

Reduces peripheral resistance

Decreases blood pressure

There are several types of CCBs. The nondihydropyridines diltiazem (Cardizem CD and SR, Dilacor XR, Tiazac), and verapamil (Calan SR, Isoptin SR, Verelan, Covera-HS) act on heart muscle as well as peripheral arterioles. Another type of CCB, mibefradil (Posicor) which acted to block calcium entry into cells through a different mechanism (T-channel blockers) has been withdrawn from the market because of numerous interactions with other drugs. Some CCBs, especially the verapamil type, may result in partial blockade of the atrioventricular (AV) or sinoatrial (SA) node, as well as have a negative inotropic effect


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