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  #1  
Old 12-02-2009
DrSeddik's Avatar
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Cool Acute Lower Limb weakness

a 32 year old female comes to the ER with bilateral weakness of the lower limbs that has been going on for 2 days now, recently accompanied with severe numbness, tingling and burning in the same area. Her BP is 160/100, heart rate is 78 bpm. You examined her to find complete flaccid paraplesia of the lower limbs, knee and ankle reflexes are lost. When asked she confers a history of diarrheal disease about 3 weeks ago. While she waits for a spinal tap she starts complaining of dyspnea and drowsiness, you were instantly alarmed and you suggest that she should be intubated. The intern disagrees with you and says she shouldn't be subjected to the aggressive procedure. You try to prove your point by taking an Arterial Blood Gases sample to the lab. What do you expect to see:

a- a normal A-a gradient
b- low CO2 and respiratory alkalosis
c- low PaO2, high PaCO2, low pH, and elevated HCO3
d- low PaO2, other values are normal
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  #2  
Old 12-02-2009
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Since this is simply a muscular weakness of Guillain Barre syndrome then hypoxia with other normal values is the correct choice (option D)
Am I right!
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  #3  
Old 12-03-2009
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Yup - and the diarrhea is campylobacter jejuni right?
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Old 12-04-2009
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This is Guillaine Barre syndrome, the patient has acute ascending motor, sensory and autonomic (HTN) neuropathies. These patients are at risk of respiratory failure which may develope dramatically with little warning. The infection is most probably Campylobacter, but the condition may follow URT infections (mycoplasma, H. influenza) and other less important infections.

Choice c would be correct if it wasn't for the renal compensation for the respiratory acidosis (high HCO3), Which needs time to develope so doesn't happen in acute respiratory failure.

This is a neuropathy and it causes type 2 respiratory failure with high CO2, I think because the patient can't hyperventilate, so he can't dump excess CO2. Other causes of type 2 respiratory failure include (high CO2) Narcotic overdose, late Acute severe asthmatic attack, sleep apnea, scoliosis, myopathy, neuropathy, upper respiratory tract obstruction, note that in all these causes there's an defect in ventilatioin of the lungs as a whole.

finally defective ventilation (this case) and high altitude are 2 causes of hypoxemia that don't cause a difference in A-a gradient. so correct answer is Choice a
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  #5  
Old 05-04-2011
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DrSeddik, why couldn't the answer be D, since the patient will have hypoxemia (due to the muscular paralysis of the diaphragm) with a normal A-a gradient (hence, other lab values are normal)?

Thanks so much =)
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  #6  
Old 05-04-2011
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the correct ans is a
look out fr the cause of hypoxemia
at high altitude n hypoventilation : no change in A-a gradient
n since due to muscle paralysis the pt fails to ventilate so the condition apply
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