Quiz week 10
A 45 year old female is brought to the ER from home during your evening shift. She has been short of breath since the morning. She has a previous history of CHF and lupus. She smokes half a pack of cigarettes.
She is awake and alert, looks anxious and you find that she is tachycardic and tachypneic. Her electrolytes are as follows: Na 134, K 4.9, HCO3 24, Cl 103 , BUN 20 , Creatinine 0.8, Glucose 95. pH 7.43 pO2 76, pCO2 26, HCO3 12, Osmolality 285.
Q1. Which of the following is an unlikely cause of this patient's symptoms
Pneumonia
Heart failure
Hyperventilation syndrome
Pulmonary embolism
Pulmonary hemorrhage
Answer is choice 3 (Hyperventilation syndrome)
This question is based on the concept of A-a gradient. This is calculated
by subtracting the partial pressure of oxygen in the blood and pCO2 with a factor 1.25
from the partial pressure of oxygen in inhaled air . Therefore if in atmospheric air, the
partial pressure of oxygen is 150mmHg (21% of 713) and in blood it is 100mmHg and the pCO2
in blood is 40 (from the ABG), A-a gradient is calculated as the following 150 -[(100)+
(40x1.25)]= A-a gradient= 0. In the normal person one can accept an A-a gradient of 15. In
this question there is an A-a gradient >15. Conditions that increase A-a gradient are
pneumonia, heart failure, ARDS, Aspiration, pulmonary hemorrhage, etc. Problems of
ventilation alone do not change the A-a gradient.
Q2. Which of the following statements is FALSE ?
The commonest cause of multi-lobar community acquired pneumonia is viral
Pneumonia due to high grade penicillin resistant Pneumococcus should be treated using Ceftriaxone
Meningitis due to high grade penicillin resistant Pneumococcus should be treated using Vancomycin
The treatment for Mycoplasma pneumonia should last for more than 14 days.
Sputum analysis and gram stain has little benefit in terms of guiding therapy of pneumonia.
Answer is choice 1 (The commonest cause of multi-lobar community acquired pneumonia is viral - this is the false statement) Pneumococcal pneumonia is the commonest pneumonia. 25% of these are multilobar. This makes this the commonest multilobar pneumonia. All other statements are true. Although penicillin resistant pneumococcus (PRSP) is best tackled using Vancomycin, outcomes in the Ceftriaxone and Vanco group were no different in the case of pneumonias. In CNS infection with PRSP, Vanco still remains the drug of choice. Mycoplasma treatment is to be done for 3 weeks. Macrolides are drugs of choice for it.