A 21 year old woman attempted suicide by taking an overdose of barbiturates. On arrival in the emergency depament, her blood pressure is 95/65 and her pulse is 105 per minute. The physician in the intensive care unit orders aerial blood gases. Which of the following values would you expect in this patient?
Barbiturate overdose causes respiratory depression, resulting in carbon dioxide retention (producing increased PCO2 and decreased pH) and hypoxemia (decreased PO2). In other words, the patient has respiratory acidosis. You should look for a low PO2, high PCO2, and acidotic pH. Choices 1st,2nd & 3rd do not fulfill these requirements. Note that 3rd choice might be expected in a patient who is hyperventilating to the point of respiratory alkalosis: diminished O2 (the usual drive for hyperventilation in nonpsychiatric hyperventilation), diminished CO2, and mildly alkalotic pH. Ref: Gresham C., LoVecchio F. (2011). Chapter 176. Barbiturates. In J.E. Tintinalli, J.S. Stapczynski, D.M. Cline, O.J. Ma, R.K. Cydulka, G.D. Meckler (Eds),Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e
PO2 = 45, PCO2 = 45, pH = 7.45
PO2 = 55, PCO2 = 70, pH = 7.50
PO2 = 65, PCO2 = 35, pH = 7.45
PO2 = 75, PCO2 = 60, pH = 7.30