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Old 02-07-2013
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Question Rustic log cabins with woodburning fireplaces

A 4-year-old boy is brought to the local emergency department by his mother because he is “not acting right.” His mother, who is pregnant, reports that he seemed well last night, but this morning he was uncharacteristically groggy and appeared “flushed.” He fell over twice while walking around the house and “passed out” for 20 seconds while eating breakfast.
Although he did not hit his head, he did complain of a headache. On the way to the hospital he vomited once; it was nonbloody and nonbilious. There are no sick contacts in the household, but his father awoke with an unusually severe headache this morning. The family is vacationing at a nearby mountain resort noted for its “rustic log cabins with woodburning fireplaces.” His temperature is 37C (98.6F), blood pressure is 90/50 mm Hg, pulse is 130/min, and respiratory rate is 26/min. The patient is minimally cooperative; he refuses to walk, preferring to nap in his mother’s arms. There is no evidence of head trauma and his physical examination is otherwise unremarkable.
Further testing would most likely reveal which of the following abnormalities?
(A) Blood glucose level of 60 mg/dL
(B) Low partial pressure of arterial oxygen measured on arterial blood gas testing
(C) Metabolic acidosis with increased anion gap
(D) Pulmonary effusion on x-ray of the chest
(E) Pulse oximetry reading of 89%
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Old 02-07-2013
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CO poisoning
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The mention of "wood burning stove" indicates CO poisoning. But shouldn't the answer be (E) Oxygen saturation of 89% on pulse oximetry?

Could OP please also mention source of the question in the first post so one doesn't come across NBME or Uworld questions one would rather not spoil?
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(E) Pulse oximetry reading of 89%
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Quote:
Originally Posted by spacecadet View Post
The mention of "wood burning stove" indicates CO poisoning. But shouldn't the answer be (E) Oxygen saturation of 89% on pulse oximetry?

Could OP please also mention source of the question in the first post so one doesn't come across NBME or Uworld questions one would rather not spoil?
Is pulse oximetry not normal in CO poison??
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Quote:
Originally Posted by Scombroid View Post
Is pulse oximetry not normal in CO poison??
CO has high affinity for Haemoglobin. So it binds with haem inside the RBC and kicks Oxygen out. Oxygen within the RBC is the saturation which is measured by a pulse oximeter. So in CO poisoning pulse oximeter reading is subnormal.
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Old 02-07-2013
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E is the correct answer as far as my knowledge goes
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Quote:
Originally Posted by Brainiac View Post
E is the correct answer as far as my knowledge goes
as far as my knowledge goes ,pulse oximetry measures Hb sat.
in CO poison,Hb is saturated but not by O2.
its saturated by CO but the pulse oximeter can not distinguish between the two
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Quote:
Originally Posted by Scombroid View Post
as far as my knowledge goes ,pulse oximetry measures Hb sat.
in CO poison,Hb is saturated but not by O2.
its saturated by CO but the pulse oximeter can not distinguish between the two
I didnt know that wee bit kind-of CRITICAL part
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Quote:
Originally Posted by Scombroid View Post
Is pulse oximetry not normal in CO poison??
http://bja.oxfordjournals.org/content/66/5/625

Yeah, didn't know that either. Something called a pulse CO-oximeter is used to detect carbon monoxide poisoning. Imagine that!

Thanks for the tip!
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Old 02-07-2013
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The answer, Mr. Elgohary?
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CO Poisoning>>>Lack of O2 delivery to tissues>>>>Anaerobic glycolysis>>>Lactic acidosis>>>>HAGMA (High anion gap metabolic acidosis)

Quote:
There are primarily 2 types of lactic acidosis:
Type A – Due to tissue hypoperfusion and hypoxia
Type B – Not due to tissue hypoperfusion and hypoxia.
Type A Lactic Acidosis
Most cases of lactic acidosis are due to reduced oxygen delivery as a result of reduced tissue perfusion from shock or cardiopulmonary arrest. Other conditions such as acute pulmonary edema, can cause severe hypoxemia leading to reduced O2 delivery. Other causes are carbon monoxide poisoning and severe anemia. Other causes of type A lactic acidosis which may not necessarily involve generalized tissue hypoxia are severe seizure, severe exercize and hypothermic shivering. All of which result in localized skeletal muscle hypoxia leading to increased lactic acid production.
The clinical signs usually indicate reduced tissue perfusion and include severe hypotension, tachypnea, oliguria or anuria, peripheral vasoconstriction and deteriorating mental status. Sepsis, particularly in critically ill patients is a very important cause of lactic acidosis and is often associated with fever (>38.5C) or hypothermia (35C). Kussmaul hyperventilation (deep sighing respiration) may be observed if the severity of the acidosis is sufficient to elicit a degree of respiratory compensation. Lactic acidosis is usually associated with laboratory abnormalities indicating organ failure or compromise such as abnormal liver function tests, elevated BUN and elevated creatinine. Lactate levels are usually greater than 5 meq/L. Upper limit of nl is 1.6 in plasma. Anion gap is classically elevated, > 16.
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Last edited by Novobiocin; 02-07-2013 at 03:01 PM.
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Old 02-08-2013
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Correct Answer

the correct answer is metabolic acidosis with increased anion gap that cause increase of lactic acid due to tissue hypoxia and its not oximetry cause as it was said in previous posts here it can't differeniate between carboxy hemoglobin , methemoglobin or normal hemoglobin as it measure Hb saturation as dr scombroid said , wish that helps , source of Q is FA Q & A , i don't put Qs from nmbe or uw as i think its not right to do so
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