Question

A 24 year old woman presented to the ED complaining of syncope and exhibiting cyanosis of the lips, tongue, and distal extremities. The patient had been at a tavern, and her friends suspected that someone had poisoned her drinks. Vitals signs were: Arterial BP 110/70, HR 120, RR 16. There was no change in her cyanosis with the administration of oxygen by nasal cannula at 3LPM. Oxygen by nasal cannula was continued and an ABG was obtained. The respiratory therapist who obtained the ABG noted that the blood was brown in color. The results on 3LPM are: 7.34/36/141/19/0/65% With the exception of HCO3 of 20 mEq/L, the venous electrolytes were within normal limits.

a. Classify the ABG

b. List abnormal clinical manifestations

c. Could there be a lavoratory error in the reported SaO2 of 65%?

d. Why should measured rather than calculated SaO2 values be used?

e. What could explain cyanosis in a patient with hyperoxemia?

f. What is the probable diagnosis?

g. Make specific recommendations for treatment

Answer 1

a, Patient PH-7.34(7.35-7.45) low
Pao2 -141(75-100)high
Paco2 - 36(35-45) normal
Hco3 19( 22-28)low
sao2 63%(94-100)low
high pao2 indicates hyperoxia with low Hco3 indicates acidosis. patient ph is less and Hco3 is low and paco2 is normal to indicate the patient is in metabolic acidosis
b, Abnormal clinical manifestations include explained cyanosis and ABG is brown in color.
c, Sao2 low value will be false by conventional pulse oximetry. ABG sao2 inappropriately higher or normal for this patient with methemoglobinemia after consuming a poisonous substance. this pulse oximeter and sao2 difference are called the saturation gap, the patient will have a high saturation gap with deep cyanosis.
d, Saturation gap is more than 5% for this patient with unexplained cyanosis, this patient needs co-oximetry or multiwavelength pulse is for a diagnostic tool with methemoglobinemia.